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Current concepts: tissue engineering and regenerative medicine applications in the ankle joint.
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PMID:  24352667     Owner:  NLM     Status:  In-Data-Review    
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Tissue engineering and regenerative medicine (TERM) has caused a revolution in present and future trends of medicine and surgery. In different tissues, advanced TERM approaches bring new therapeutic possibilities in general population as well as in young patients and high-level athletes, improving restoration of biological functions and rehabilitation. The mainstream components required to obtain a functional regeneration of tissues may include biodegradable scaffolds, drugs or growth factors and different cell types (either autologous or heterologous) that can be cultured in bioreactor systems (in vitro) prior to implantation into the patient. Particularly in the ankle, which is subject to many different injuries (e.g. acute, chronic, traumatic and degenerative), there is still no definitive and feasible answer to 'conventional' methods. This review aims to provide current concepts of TERM applications to ankle injuries under preclinical and/or clinical research applied to skin, tendon, bone and cartilage problems. A particular attention has been given to biomaterial design and scaffold processing with potential use in osteochondral ankle lesions.
Authors:
S I Correia; H Pereira; J Silva-Correia; C N Van Dijk; J Espregueira-Mendes; J M Oliveira; R L Reis
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Type:  Journal Article     Date:  2013-12-18
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Title:  Journal of the Royal Society, Interface / the Royal Society     Volume:  11     ISSN:  1742-5662     ISO Abbreviation:  J R Soc Interface     Publication Date:  2014  
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Created Date:  2013-12-19     Completed Date:  -     Revised Date:  -    
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Nlm Unique ID:  101217269     Medline TA:  J R Soc Interface     Country:  England    
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Languages:  eng     Pagination:  20130784     Citation Subset:  IM    
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Journal ID (nlm-ta): J R Soc Interface
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ISSN: 1742-5662
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Received Day: 26 Month: 8 Year: 2013
Accepted Day: 28 Month: 11 Year: 2013
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DOI: 10.1098/rsif.2013.0784
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Current concepts: tissue engineering and regenerative medicine applications in the ankle joint Alternate Title:Current concepts: tissue engineering and regenerative medicine applications in the ankle joint
S. I. Correia12
H. Pereira1234
J. Silva-Correia12
C. N. Van Dijk35
J. Espregueira-Mendes123
J. M. Oliveira12
R. L. Reis12
13B's Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, S. Cláudio de Barco, Taipas, Guimarães 4806-909, Portugal
2ICVS/3B's—PT Government Associate Laboratory, Braga/Guimarães, Portugal
3Saúde Atlântica Sports Center—F.C. Porto Stadium, Minho University and Porto University Research Center, Porto, Portugal
4Orthopedic Department, Centro Hospitalar Póvoa de Varzim, Vila do Conde, Portugal
5Orthopedic Department, Amsterdam Medical Centre, Amsterdam, The Netherlands
Correspondence: e-mail: miguel.oliveira@dep.uminho.pt

1.  Introduction: fundamentals of tissue engineering and regenerative medicine
1.1.  Tissue engineering and regenerative medicine surgical application potential in several ankle tissues

In the anatomical ankle region, several tissues develop injuries/pathologies with new emerging therapeutic possibilities arising from tissue engineering and regenerative medicine (TERM) strategies.

Tissue engineering (TE) and related therapeutic strategies, which mimic the mechanisms of tissue normal repair and regeneration, have been regarded as a revolution in medical sciences [1]. As stated by Langer & Vacanti [1], TE is the research field which combines the principles of engineering, and life and health sciences with the development of biological functional substitutes. The aim is to restore, defend (avoid disease progression) or improve the function of the damaged tissue and/or organ.

Application of ankle TE strategies [2,3] can consider, by definition, three main variables (figure 1): (i) tridimensional porous supports or scaffolds [4,5], (ii) cells (differentiated or undifferentiated), and (iii) bioactive agents, i.e. physical stimulus [6], and/or growth factors (GFs) [7,8]. Cells can be seeded and cultured onto a structure or scaffold capable of supporting three-dimensional tissue formation [9]. GFs can be used in the isolated form in injured tissue/organ, as a ‘pool’ of GFs or in association with scaffolds and/or cells [10,11]. The use of bioreactors (dynamic systems) as a way to improve the in vitro biological and mechanical properties of the TE constructs (cell-laden scaffolds) is also advantageous, as it can allow one to overcome the limitation of nutrients/metabolites diffusion observed in static cultures [12]. On the other hand, regenerative medicine (RM) is a broader concept which, besides that previously discussed for TE, also considers the use of bioactive soluble molecules [13,14], stem cell technologies [15,16], prolotherapy (i.e. injectable regenerative techniques) [17], genetic therapeutic strategies [18], nanotechnologies and several medical devices.

The terms TE and RM can be used interchangeably, but both fields have been globally referred to in association as TERM [9,19].

In this review, an overview is given of the present applications in treatment of skin, tendon, bone and osteochondral lesions in the ankle joint.

1.1.1.  Applications of tissue engineering and regenerative medicine strategies to skin repair

Cutaneous ulcers around the ankle, secondary to trauma, vascular insufficiency or diabetes [20,21] are injuries that require special attention mainly owing to low vascular supply, a problem that is of great importance in poor subcutaneous tissue areas.

Simplicity of application and affordable price are the main reasons by which GFs have been widely applied for treatment of different injuries in orthopaedics but also in cardiovascular, plastic surgery and dentistry [22,23]. In a body injury, platelets participate in the natural healing process, being responsible for haemostasis and releasing of bioproteins or GFs that are crucial to the wound-healing process [22,24]. Platelet-rich plasma (PRP) can be harvested from patients’ own peripheral blood and after concentration it becomes ready to be administered at the injury site [25].

Biodegradable biomaterials [21,26] have also been processed as scaffolds and membranes as these systems can act as drug delivery carriers (figure 2), while serving as a three-dimensional template for supporting cell proliferation and repair at the damaged site.

Bone morphogenetic proteins (BMPs) are members of the human transforming growth factor-β (TGF-β) superfamily and similarly to PRP have been demonstrated to have many therapeutic possibilities [27,28]. However, BMPs still present a considerably higher cost as compared with PRP. The biological mechanism of action for BMPs has been demonstrated by Urist [29]. BMP-2 and BMP-7 belong to TGF-β superfamily, and BMP-1 is considered a metalloprotease. It is undeniable the importance of these GFs in the field of tissue engineering, owing to their effect in regeneration of body tissues, specially bone and cartilage. More than 15 BMPs have been described, and their specific characteristics and mechanism of action are under investigation [28].

Tissue-engineered skin with allogeneic dermal fibroblasts and epidermal keratinocytes [21] has been successfully used in chronic wounds that fail to heal with standard wound care. Allogeneic dermal products seem to have the necessary cytokines for wound healing, presenting not only superior effective rate, but also reduced time of treatment. Yamada et al. [30] proposed the use of a bilayered hyaluronan/atelocollagen sponge seeded with fibroblasts for wound-healing (e.g. leg, ankle or foot ulcers) applications. That work has shown the beneficial effect of using cell-seeded scaffolds when treating ulcers as it improved wound healing.

TERM approach using acellular dermal graft has also been described [31]. This technique allies tissue-engineered matrices to the cells and GFs present in the human recipient following transplantation. Brigido [32] reported a clinical trial which demonstrated that Graftjacket tissue matrix showed a statistically significant higher percentage of wound healing with respect to wound, and it is more effective than sharp debridement in this small case-control trial. The disadvantage of allogeneic dermal products as compared to the acellular graft is that they require multiple applications and can only be applied to the treatment of superficial full thickness ulcers.

Another relevant issue is related to the treatment of infection in this area. Using TERM technologies such as nanotechnology [17,20,33] (e.g. micro- and nanoparticles or nanospheres developed as systems to deliver drugs in a controlled manner), it is possible to increase simultaneously the delivery of antibiotics at the damaged site and promote tissue repair [13].

1.1.2.  Applications of tissue engineering and regenerative medicine strategies to tendon repair

Another relevant group of injuries located in the ankle region is the tendon lesions. Most tendons have the ability to heal after injury, but the newly formed tissue is functionally different from normal tendon. Achilles tendon pathologies (in their several classifications) [34] have high impact in both high-level athletes and the general population. Figure 3 shows a magnetic resonance image (MRI) of a typical Achilles tendon partial rupture. Tendon acute tears treatments are managed by direct suturing techniques [35,36], and the most common form of healing is scar formation. Poor tissue vascularization explains the slow healing rate and the observed scar tissue in the repaired tendon. The latter can affect tissue functioning as scar tissue results in adhesion formation, which disrupts tendons. Therefore, it represents a higher risk of further damage [3739]. All these facts contribute to distorted motion and consequently reduced life quality [40]. In the last few years, several TERM approaches have been investigated with the promise of a more successful outcome for patients, where acute tendon pathology and chronic tendon ruptures have been diagnosed [4143]. This can be achieved by means of both inhibiting degeneration process [4447] and helping to relieve pain [48].

Several GFs have been found to be useful in tendon wound healing [40], like TGF-β [44], BMP, fibroblast growth factor (FGF) [49] and insulin-like growth factor (IGF) [50]. All aforementioned approaches using GFs proved to accelerate the wound-healing process and strength of the repair. However, depending on the concentration, half-time and applied technique, it can also promote undesired fibrosis, with excessive disordered collagen deposition, i.e. the structural properties are improved, but not the tissue functioning [44].

Several studies have reported that PRP has a positive effect on proliferation and metabolism of human tenocytes, and thus enhances tendon repair [22,51]. Meanwhile, the main problem might be the standardization of the methods used in the clinical setting, and concentration of platelets and GFs to be used. One of the most challenging goals is related to the need for establishing the optimal concentration, half-life and local of injection and avoiding clearance of the PRP from lesion sites [48].

Tenocytes present low mitotic rate, which obviously influences any therapeutic approach. Particularly, in an attempt to reverse/decelerate the degenerative process, controlled drug delivery systems, such as micro- or nanoparticle proteins or polymer-based systems [52,53], have been tried. Figure 4 illustrates gellan gum microparticles obtained by precipitation in a phosphate buffer saline solution. Nanotechnology-based approaches are promising when it is envisioned to stabilize and to achieve a controlled release of a given therapeutic agent at the defect site.

Several authors have proposed both acellular and cellular silk fibroin-based scaffolds for ligament/tendon tissue engineering with promising results, in vitro and in vivo [54,55]. TERM approaches using a ligament/tendon with similar mechanical and functional characteristics as the native tissue can prevent several complications associated with the traditional methods. Scaffolds can be combined with stem cells [15,49,56] or GF [22,24,49,51,57] in a in vivo approach (to permit the self-regeneration of small tissue lesions) or used alone [5860] in an ex vivo approach, designed to produce functional tissue that can be implanted in the body. The ideal scaffold for tendon engineering must retain the basic structure of the tendon, mimic native extracellular matrix (ECM) and competence for cell seeding [61]. Reports on the use of several scaffolds (e.g. silk fibroin [54], collagen [45,58], chitosan-based [53] or poly(ethylene glycol) diacrylate hydrogel [62]) combined with adult mesenchymal stem cells (MSCs) demonstrated that differentiation of MSCs into tenocyte-like cells can occur in response to chemical factors, including BMPs, TGF-β and FGF [46,49].

1.1.3.  Applications of tissue engineering and regenerative medicine strategies to bone repair

Bone defects and bone reconstruction are, probably, two of the most important issues in a TERM perspective, with several proposals advanced over the years [7,29,53,62,63]. Some injuries in anatomic areas such as distal tibia, talus or calcaneus, given their difficult irrigation and scarce soft tissue protection, usually are difficult to consolidate. This is a particularly critical problem in patients with a clinical history of multiple surgical interventions [33].

Bone grafts can cover the basic requirements for bone repair as they combine a scaffold, GFs and cells with osteogenic potential. Yet, the use of bone grafts is associated with several complications, i.e. non-unions [64], incomplete filling of the defect and late graft fracture [63]. Furthermore, harvesting of autologous bone often results in donor site morbidity, which may vary with the location site and the applied technique [65].

Some technologies combining the use of GFs (namely BMPs) [7,28,29], cells [16] and/or scaffolds [66,67], adapted or not to a surgical intervention have achieved promising results in cases where several previous surgeries have failed systematically [3,33,68].

BMPs, specifically BMP-2, BMP-4 and BMP-7, have been known for over a decade for inducing osteogenic cell differentiation in vitro and in vivo [68]. The value of recombinant human BMP-2 (rhBMP-2) has been evaluated in a prospective study for treating open tibial shaft fractures [69]. A significant reduction of a secondary intervention was observed in the rhBMP-2 group as compared with the standard care group, suggesting that the use of GFs could accelerate healing of fractures and soft tissue, reduce hardware failure, and thus re-operation owing to delayed healing/non-union. Still, there are only few available GFs for clinical use in bone regeneration besides BMP-2, BMP-7 and growth and differentiation factor-5 (GDF-5) [70]. Recently, Kleinschmidt et al. [70] reported that the use of a mutant GDF-5 (obtained by introducing BMP-2 residues into GDF-5) demonstrated enhanced osteogenesis and long bone formation capacity [70]. When the use of GFs alone is not recommended, as in the treatment of large bone defects, stem cells and scaffolds are a very promising alternative to standard procedure. Stem cell-based TERM strategies require three main steps: (i) cells are harvested, isolated and expanded, (ii) scaffolds are seeded with the induced cells, and (iii) cell-seeded scaffolds are re-implanted in vivo [68]. The aim of TERM is the substitution of the missing tissue with the ex vivo tissue-engineered construct. There are several reports [71,72] on the application of different scaffolds combined with stem cells (mostly MSCs derived from bone marrow or adipose tissue). These have shown favourable autogenous bone grafting and no donor site morbidity [68]. Scaffold choice is still under investigation in order to be standardized. Biodegradable synthetic polyesters [73], calcium phosphate ceramics [74,75] and chitosan–alginate [76] are some of the scaffolds that have proved to have significant value in the treatment of bone defects.

Cancedda et al. [63] have provided relevant information and new insights on the importance of scaffold architecture towards enhancing de novo bone formation within scaffolds in vivo.

Kokemueller et al. [77] have been also investigating the vascularization of seeded scaffolds required for clinical application in reconstructive cranio-maxillofacial surgery. The authors reported that prefabrication of vascularized bioartificial bone grafts in vivo might be an alternative to in vitro tissue engineering techniques as it presented minimal donor site morbidity and no shape or volume limitations.

More recently, Nagata et al. [78] reported the use of cultured autogenous periosteal cells (CAPCs) in alveolar bone regeneration. CAPCs were mixed with particulate autogenous bone and PRP and grafted into the injury sites. Results have shown that CAPC grafting enhances recruitment of both osteoblasts and osteoclasts, accompanied by angiogenesis and leading to satisfactory bone regeneration.

Oliveira et al. [79] proposed the combination of nanotechnology tools and tissue engineering approaches for pre-programming the fate of bone marrow stromal cells (BMSCs) towards promoting superior de novo bone formation. The authors have shown that BMSCs cultured in vitro (figure 5) with a dendron-like nanoparticles system that delivers dexamethasone intracellularly, seeded onto starch–polycaprolactone (SPCL) scaffolds (figure 5a) and implanted subcutaneously were able to differentiate and produce new bone, in vivo (figure 5c). That work clearly evidenced the advantages of using intracellular tools, for example the dendronized nanoparticles, for tuning stem cells in vivo.


2.  Osteochondral ankle lesions

Osteochondral defects (OCDs) and osteoarthritis in lower limb have a relevant socio-economic impact with significant therapeutic investments and absence from work-related costs [80,81]. OCDs are defined as lesions of any origin that involve the articular surface and/or subchondral region, thus affecting cartilage, bone or both [81]. Suggested causes of ankle OCDs include local avascular necrosis, systemic vasculopathies, acute trauma, chronic microtrauma, endocrine or metabolic factors, degenerative joint disease and genetic predisposition [82].

Asymptomatic OCD patients can be treated non-operatively, with rest, ice application and immobilization or temporarily reduced weight bearing, even though this management has shown relatively high rates of failure [83].

Symptomatic patients with OCDs should be treated surgically. The main aim is to promote re-vascularization of the bone defect [8486]. This goal is achieved applying three principles [87]: (i) debridement and bone marrow stimulation (e.g. microfracture, drilling and abrasion arthroplasty), (ii) securing a lesion to the talar dome (e.g. fragment fixation, retrograde drilling and bone grafting), and (iii) development or replacement of hyaline cartilage (e.g. autologous chondrocyte implantation (ACI), osteochondral autograft transplantation (OAT), mosaicplasty and allografts) [88].

Articular hyaline cartilage is avascular and it has poor regenerative capability [89,90]. When repair involves the formation of fibrous cartilage, the newly formed tissue will lack favourable biomechanical properties and it can fail [90]. Therefore, the damaged tissue should be replaced with a tissue that best resembles the native hyaline cartilage [81,88]. For this reason, significant economic and scientific investments have been made on TERM applications in the treatment and prevention of cartilage defects and joint degradation [33]. Minimally invasive methods that can facilitate their use have also attracted much attention [81,88,91,92]. Besides, prolotherapy and arthroscopic/endoscopic procedures have a lower risk of complications. These procedures facilitate and decrease rehabilitation time, thus they help fight absence from work and promote return to athletic activity [88,92]. TERM strategies have been developed or adapted to promote this kind of application/delivery [81,88,92].

2.1.  Applications of tissue engineering and regenerative medicine strategies to ankle osteochondral lesions repair
2.1.1.  Applications of isolated growth factors

Debridement and bone marrow stimulation have been used as surgical approaches for partially destroying the calcified zone that is often present in OCDs and to create multiple openings into the subchondral bone [87,89]. As a consequence of these interventions, intra-osseous blood vessels are disrupted, and the release of GFs can lead to the formation of a fibrin clot and fibro-cartilaginous tissue formation. These approaches have proven to be one of the most effective treatments for OCDs of the talus, especially in a small lesion (less than 6 mm), with minimal subchondral bone involvement [81,87].

Based on this surgical treatment, the use of isolated GFs in the treatment of symptomatic OCDs has undergone a huge expansion over the last few years [33]. In the body's natural response to injury, a complex healing process is initiated. Platelets participate in this process, as they are responsible for stopping bleeding and for haemostasis [22]. Once they are activated by mediators at the site of injury, they undertake degranulation, releasing GFs that will help the wound-healing process. Examples of these GFs are TGF-β, IGF-1 and IGF-2, FGF, all of which have been shown in experimental settings to promote healing and the formation of the new tissue [8].

The short half-life of these proteins, the difficulty in keeping them within the area of the defect and the low mitotic rate of chondrocytes, among several other issues, make it hard or even impossible to predict, from a theoretical perspective, the complete repair of a chondral defect or OCD using this approach [28]. Moreover, results available in the literature are controversial, with some series reporting significant clinical or symptomatic improvement [17,24], while other studies conclude that there is not enough evidence to support their use with this objective [8]. Two recent reports have used TGF-β, IGF-1 and BMP-2 associated with scaffolds and have reported promising results for the repair of OCDs and cartilages [93,94]. Although the anabolic effect of these GFs cannot be questioned, as has been demonstrated and confirmed in vitro and in vivo [95,96], the original tissue replacement for fifibrous tissue is commonly observed in the neo-surface of the OCDs [2,94].

It is consistently recognized that most of the published studies have a low methodological quality in this matter, i.e. besides the absence of uniform criteria in outcome assessment, most of them also do not consider or not specify the different GFs applied, their quantities, isolation methods, simultaneous presence or absence of other proteins (e.g. metalloproteases) or cells (e.g. leucocytes) [22,25,97]. It becomes obvious that the improper early use of a promising technique will lead to obstacles in its correct improvement which creates higher resistance to its future application. However, tissue repair and homeostasis depend on a multitude of factors (the TERM triad) and should not be lightly simplified this way. Research must still progress considerably to gain deeper knowledge on the GFs application and their effects on different tissues and clinical situations. Thus, GFs are probably not expected to be a panacea, being able to solve all our problems independently of the way they are produced, stabilized and administered to the patient.

Besides the previously stated, one cannot ignore the analgesic effects which simple platelet-derived GF methods have shown in several clinical trials [8,22], particularly among high-level athletes.

2.1.2.  Applications of isolated cells

MSCs have demonstrated their high potential for clinical use as therapeutic agents with several possible RM applications including orthopaedics and percutaneous (injectable) techniques [98].

The rehabilitation of injured/degraded cartilage through the degenerative process leading to osteoarthritis remains the main challenge that clinicians and researchers have been facing. Several researchers have tested the use of MSCs instead of chondrocytes in the attempt to repair cartilage defects and defend joint homeostasis [71,99,100].

MSCs have the capacity to modulate the immune response of the individual and positively influence the microenvironment of pluripotent cells already present in native injured tissue. Through direct cell-to-cell interactions or by secreting a number of different proteins, MSCs can promote the endogenous regenerative mechanisms still present in an arthritic joint [101].

Gene therapy with modified MSCs might increase this therapeutic field in the near future [68,96,101]. Besides their isolated application, MSCs’ chondrogenic differentiation can be induced at the target tissue or in combination with an adequate support scaffold [99]. This may obviate the limited lifespan of chondrocytes that is an obstacle in the treatment of large OCDs [102].

Another therapeutic possibility makes use of cultured chondrocytes, which are expanded and finally implanted at the defect site [103]. ACI is an alternative to OAT and it involves harvesting a small amount of cartilage for chondrocyte isolation and culturing (in vitro), usually from a knee ipsilateral to the ankle injury [87,88,103]. Cell-based techniques have gained relevance in OCDs because, unlike bone-marrow-stimulation methods, where fibrocartilage fills the defect, cells can potentially induce regeneration and produce a ‘hyaline-like cartilage’ [104]. Nevertheless, a recent study [105] has shown that chondrocytes from the injured zone in the ankle have poorer regenerative capacities as compared with normal tissue, stating some reservations to their use in the therapeutic field. Thus, it seems that the source for harvesting cells should be a normal, healthy tissue, requiring one additional surgical procedure and limited associated morbidity.

On the other hand, the differentiated cells are sensitive and can present biochemical changes or diminished viability during the processes of harvesting, culturing, expansion or re-implantation in the defect zone [6].

The potential of ACI in the treatment of OCDs has been the source of great enthusiasm since the study performed by Brittberg et al. [103]. After 3 years of follow-up, the transplants restored considerable knee function in 14 of the 16 patients with femoral defects. The treatment resulted in the formation of new cartilage that was similar to normal cartilage in that it had an abundance of type II collagen and metachromatically stained matrix, similar as in original cartilage.

Still, despite several successes reported by the followers of this technique [106], up to now there is no evidence-based medicine to support their use, with no proven cost-effective advantages as compared to ‘classic’ treatment options such as microfractures or osteochondral grafting techniques (OAT, mosaicplasty) [107111].

Some advocate specific conditions for its use, for example a defect area more than 4 cm2 (factor predictor of a better outcome with ACI), reinstating the existence of specific injury and individual's conditions which might play a determinant role in outcome [112]. As aforementioned, gene therapy can enhance the clinical application of differentiated cells as stated by Orth et al. [113]. That study demonstrated that chondrocytes modified for higher co-expression of IGF-1 and FGF-2 hold an increased chondrogenic capacity in vivo.

2.1.3.  Applications of biomaterials

Hyaline cartilage serves as a low-friction surface with high wear resistance for weight-bearing joints. Unfortunately, it possesses an avascular and alymphatic profile which limits its autonomous regenerative capacity. The application of differentiated cells in the clinic presents additional problems such as cells' tendency towards losing their differentiated phenotype in a two-dimensional culture (e.g. chondrocytes) and to differentiate towards a fibroblast-like phenotype [114]. To overcome this problem in the treatment of cartilage lesions, different scaffolds have been developed for supporting cell adhesion, proliferation and maintenance of phenotype in an effective manner [4,115].

Among the several scaffolds proposed in an attempt to better fulfil the requirements of cartilage regeneration process, there are substantial differences regarding the materials chosen and their physical forms (i.e. fibers, meshes and gels). Solid scaffolds provide a substrate on which cells can adhere, whereas gel scaffolds physically entrap the cells [116]. The biomaterials used can be classified as synthetic or natural. Synthetic matrices present mechanical properties and degradation rates more easily tuned as compared with that of natural polymers, but some biocompatibility concerns might be raised owing to their degradation products and potential effect on native tissue and implanted cells. However, innovations in chemistry and materials science have been improving their biocompatibility [116]. Among the natural and synthetic materials that have been investigated (e.g. gellan gum, alginate, silk fibroin, chitosan, hydroxyapatite, collagen, hyaluronic acid (HA), polyglycolic acid and polylactic acid) [117], few have been used in ankle lesions, probably due to the lack of studies in the field of ankle tissue regeneration. Table 1 [5,53,93,118127,129,130,132140,142145,147151] summarizes the most important reports on polymers, ceramics and composites that have been used as scaffolds for osteochondral tissue regeneration.

Biomaterials including ceramics and polymers, such as aragonite [148], silk fibroin [5,121] or tricalcium phosphate [149151], are some of the most promising materials for OCD regeneration, alone or alternatively blended with other materials.

The application of an injectable biomaterial with bioadhesive properties, for example gellan gum (figure 6a), for regeneration of cartilage has been proposed for the first time by Oliveira et al. [129]. The gellan gum hydrogel was shown to efficiently sustain the delivery and growth of human articular chondrocytes and support the deposition of a hyaline-like ECM [128], leading to the formation of a functional cartilage. The use of biocompatible gellan gum-based hydrogels (e.g. methacrylated gellan gum, GG-MA) is also justified due to their many advantages such as improved biostability, tuneable degradability, mechanical properties and bioadhesiveness [52,130,131]. The versatility of the injectable gellan gum hydrogels and functionalized derivatives allowed the development of ionic- and photo-cross-linked GG-MA hydrogels, with improved mechanical properties for in situ gelation, within seconds to a few minutes [152,153]. Besides being able to serve as carriers of GFs/drugs and/or cells and promote ECM production, in another study [154], GG-MA hydrogels have been shown to possibly enable the control of the neovascularization process. In other words, one can use two different forms of gellan gum-based hydrogels to transport different cells: (i) in a given zone, facilitate vascular ingrowth (e.g. area to integrate in subchondral bone in a grade IV injury according to International Cartilage Repair Society) and (ii) in another area, prevent neovascularization and re-innervation by the presence of the hydrogel itself while it can also transport chondrocytes to the region that will replace hyaline cartilage [154]. That important work brings new insights to mimicking more precisely the native properties of tissue, because different tissues require neovascularization for regeneration, as in others vascularization and re-innervation is associated with pain and degeneration [155]. In fact, one of the goals of TERM is, precisely, to maintain the human characteristics of the natural tissue and so the knowledge of physiology of the original tissue is crucial.

Another biomaterial that has been tested, including in talar dome resurfacing, is collagen in its many presentations [66]. Besides its biocompatibility and positive results for the management of painful post-traumatic of the ankle joint, the biomechanical properties and stability remains an issue in several of its applications [66,118].

Hydrogel systems have been developed to obtain optimal nutrient diffusion [40,49], connectivity with host matrix, adequate biodegradability, solubility and mechanical properties to facilitate the production and organization of the matrix [14]. Several improvements have been achieved with several former systems, but the ‘ideal’ one remains to be established [156]. One of the most studied hydrogels is based in HA. The use of HA as adjuvant of microfractures surgical treatment (i.e. bone-marrow-stimulation techniques) seems to improve the results of microfractures alone, taking advantages of HA's rheological properties [157].

Since a treatment that focuses exclusively on articular cartilage is likely to fail [90], it has been suggested that treatment strategies should be designed with the entire osteochondral unit (articular cartilage and subchondral bone) [90]. Therefore, bilayered porous scaffolds with poly(lactide-co-glycolic) (PLGA) seeded with BMSCs [137] or with GFs [138] were reported to simultaneously regenerate cartilage and subchondral bone of rabbit knee. Porous PLGA–calcium sulfate biopolymer (TruFit by Smith and Nephew, London, UK) is one of the most popular commercially available devices (probably the most clinically tested) [135,136], and it has been applied from mono- to bilayered presentations (figure 7). Jiang et al. [135] observed bone formation in the osseous phase, with evident subchondral remodelling, as well as normal hyaline cartilage, in a mini-pig model, when cell suspension (composed of the harvested autogenous cartilage) was injected into the chondral phase of the PLGA scaffold. More recently, this device is also available in a shape adapted to the anteromedial talar corner. However, there is still little evidence-based medical data supporting its use in either acellular or cellular strategies, besides the existence of some concerns with polyglycolic acid biocompatibility [90,158].

In the field of ceramic polymers, hydroxyapatite is one of the most used implant materials for medical applications owing to its high biocompatibility [144]. It seems to be the most appropriate ceramic material for cartilage tissue engineering. However, owing to low strength and fracture toughness of the material, new approaches have been reported [147] in order to achieve a scaffold with the most suitable properties for cartilage tissue engineering. Sotoudeh et al. [147] reported that a composite of zirconia and hydroxyapatite would be an effective scaffold for cartilage regeneration.

The use of bilayered scaffolds (figure 6b) that combine different materials in the same implant constitutes a natural evolution in OCD treatment, in an attempt to combine favourable properties to both bone integration and cartilage repair [124,159]. In fact, it has been shown that the hydroxyapatite layer permits adhesion and proliferation of MSCs and osteogenic differentiation in vitro [124], while facilitating new bone formation in vivo [72]. By its turn, the cartilage-like layer is also able to support the adhesion of MSCs and can promote chondrogenesis, in vitro.

Another important commercially available product is MaioRegen (Fin-Ceramica SpA, Faenza, Italy) [146,160], which is a trilayered scaffold for treatment of OCDs. The deepest layer is composed of hydroxyapatite, the intermediate layer is a mixture of type I collagen and hydroxyapatite and the superficial layer consists of type I collagen only. In a previous study performed in vitro and in vivo, Kon et al. [145] obtained similar results when the scaffold was loaded with autologous chondrocytes or when it was used alone. The ability of the scaffold to induce OCD repair without the seeding of autologous cells makes it very attractive [146]. Comparative studies with OAT, ACI and bone-marrow-stimulation techniques are needed to establish the clinical outcome of this procedure.

2.1.4.  Applications of advanced tissue engineering and regenerative medicine strategies

The requirement for full OCD repair has been approached considering the heterogeneity of different tissues, different components and layers (including subchondral bone plate and different hyaline cartilage layers). This is also part of the underlying principle for OAT. Although some attempts have been made to overcome one of the most relevant problem of OAT [107], relevant morbidity related to donor zone in knee-to-ankle transplantation has been demonstrated [110,161]. Furthermore, other problems persist with these techniques including graft's source, achievement of joint congruence and interface between graft plugs and between grafts and native cartilage. It is generally accepted that the use of a lower number of plugs is a predictor of a better mid- to long-term outcome [107].

Table 2 [162165] summarizes the most important clinical studies related to TERM strategies for treatment of ankle lesions. Those studies have tested two main biomaterials, i.e. collagen and hyaluronan-based scaffolds/membranes, with matrix-induced ACI (MACI, Verigen, Leverkusen, Germany) being the most used approach. This technique can be considered as an evolution of conventional ACI and it makes use of processed cells that are harvested and isolated from the patient and expanded in vitro. Once grown, the chondrocytes are seeded between layers of a bilayered collagen scaffold in the operating room, prior to implantation of cell–scaffold construct into the defect area.

The studies that have been reported demonstrate [119,121,133,151] that combination of scaffolds and autologous cells can enhance the regeneration outcome, using scores adopted either by American Orthopaedic Foot and Ankle Society (AOFAS) or Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART).

Cellular-based techniques, such as ACI and MACI, require a two-stage operative procedure, where initial harvesting of cartilage is followed by culturing and subsequent implantation of the cultured tissue. In fact, this issue has been considered one of the major drawbacks of ACI. This has been the driving force for the search for new treatment methods [166] and development of novel and bioactive scaffolds, which can be easily implanted and fixed, and best mimic the native tissue to be repaired. The use of bilayered tridimensional porous scaffolds enhanced by MSCs requires several years of preclinical research [124]. Still, it remains a trend with high interest and investment from the scientific community. The histological results are available only in animal studies, but are indeed very encouraging [145]. Clinically, they have been applied up to now only in the knee, but they may represent a solution for the repair of deep OCDs even in the ankle [100,146]. The development of the ideal scaffold has been performed in a stepwise manner and is dependent on the knowledge gained in the last few years, in what concerns the biomechanical and biological properties of native tissues [5].

MSCs are emerging as a powerful tool for treatment of cartilage lesions, thanks to their ability to differentiate into various lineages [167]. In particular, the use of concentrated bone marrow instead of chondrocytes, in order to provide MSCs to be seeded onto the scaffold, has been recently introduced in clinical practice as a one-step procedure for the treatment of OCDs.

Giannini et al. [163] described their experience with bone-marrow-derived cells (BMDCs) implanted in talar dome focal OCDs. Two types of scaffolds were tested. Both collagen powder and hyaluronic acid membrane showed similar clinical improvement at 2 years in AOFAS score and a good MRI. Recently, the same group [168] compared the clinical outcome in focal osteochondral monolateral talar dome lesions after three different surgical approaches: (i) open fifirst generation ACI, (ii) arthroscopic Hyalograft C (Fidia Advanced Biopolymers Laboratories, Padova, Italy) implantation, and (iii) arthroscopic repair by BMDC implantation on a hyaluronic acid membrane. Although similar pattern of improvement was found at 3 years follow-up in all groups regarding collagen type II and proteoglycan expression, BMDCs showed a marked reduction in procedure morbidity and costs, demonstrating it to be a one-step technique able to overcome most of the drawbacks of previous techniques. Nearly complete integration of the regenerated tissue with the surrounding cartilage was demonstrated in 76% of the cases. In addition, histological analysis highlighted the presence of all components of hyaline cartilage in repaired tissue, which showed various degrees of remodelling.

Finally, Battaglia et al. [169] confirmed the good results of BMDC transplantation, with 85% of good to excellent clinical outcome, and demonstrated the ability to regenerate hyaline cartilage but not the capability of osteogenesis in OCD repair. In fact, regenerated mature bone was evident only in two cases and in less than 8% of regenerated volume. It must also be kept in mind that the phenotypic preservation of chondrocytes and/or adequate manipulation of MSC differentiation process in different tissues remain as challenging unsolved issues. Chondrocytes are ‘fragile’ cells, exposed to de-differentiation during laboratory manipulation (loss of original phenotype) [59,68,111]. The differentiation of MSCs into chondrocytes is a multi-factorial, complex target which requires, in vitro, the contemplation of simulators of biophysical stimulus present in normal tissues—bioreactors [26,135,136,158,170]. Both cell types remain under preclinical investigation and the bench-to-bedside transfer is still an unclosed matter.

The treatment of different focal OCDs by means of using autologous chondrocyte transplantation in tridimensional support scaffolds has been recently attempted [10,108,112,164]. Aiming to enhance this therapeutic strategy, the simultaneous application of GFs has also been evaluated, attempting to favour local environment for short-term integration and promote differentiation [10,11].

A recent study comparing two commercially available methods, (i) Hyalograft C (used by arthroscopic application) and (ii) Chondro-Gide MACI (open surgery application), concluded that both methods led to positive results, but the method of application influenced short-term results [171]. Arthroscopic application seems to provide faster rehabilitation, despite no significant differences being noted at 2 years follow-up. The reported failure rate was globally 20% highlighting the need for improvement of both techniques. The authors considered results as fair/good and recommended consideration of these techniques when debridement and bone marrow stimulation fail [171].

Gene therapy can provide some new answers to previously described pitfalls and limitations, but it might raise a different level of concern. The use of chondrocytes genetically transfected to increase the expression of BMP-7 inoculated into a fibrin–collagen scaffold provided better histological results as compared with controls (rabbit model) [18].

TERM applications have not only been attempted in focal defects but also in global joint degeneration, i.e. arthritis. Joint replacement using biological tissue modified using TERM principles to mimic osteochondral tissue has been attempted [172]. In addition, the use of synthetic materials (e.g. ceramics) enhanced by MSCs aiming at future application in patients presently referred to fusion or total ankle arthroplasty has been evaluated [173].

Concerning focal defects, a non-biological solution developed by van Dijk's group [174] presented promising results by means of contoured focal metallic replacement (figure 8), despite the lack of mid- to long-term follow-up in larger series.

An important issue regarding the applications of biomaterials is the implant–tissue interface. Because of the geometric complexity of the ankle and the relative thickness of its cartilage, the use of focal resurfacing implants to treat talar OCDs, as well as biomaterials, presents challenges with regard to implant/biomaterial design, selection and surgical placement [175]. Considering the basic principles of TERM, besides biological conditions, ankle biomechanics must be taken into account [91] since it is a more congruent joint compared with the knee [176]. A congruent joint surface, for example the ankle, is usually covered with thinner hyaline cartilage compared with incongruent ones that possess thicker cartilage, for example in the knee. The diminishing of articular congruence produces higher contact pressure per joint area. Higher loss of congruence or malalignment will lead to growing contact pressure with all its implications [91,177,178]. Injured subchondral bone, as in OCDs, is less effective in supporting the overlying cartilage, and this might be one of the reasons explaining the greater difficulty for cartilage repair in these situations [179,180].

Becher et al. [181] measured contact stress redistribution in the human knee after implantation of a metallic resurfacing cap, and reported elevated contact stresses associated with device implants. Also, Custers et al. [182] stated that implants seem to cause considerable degeneration of the directly articulating cartilage in the knee. In the case of biomaterials, owing to their biocompatibility, integration into the surrounding cartilage is usually observed [183]. This way, the stress level changes on the joint are minor. However, the size and shape of the OCDs must be taken into account, to ensure that the biomaterial is as similar as possible, in order to completely fulfil the injured area.


3.  Final considerations

The appropriate treatment for OCD repair is still controversial. The ideal technique would regenerate a tissue with biomechanical properties similar to normal hyaline articular cartilage, with reduced morbidity and costs. The excellent durability of results obtained by ACI or MACI over time is well established and contrasts sharply with the long-term results reported for bone-marrow-stimulating techniques (such as abrasion, drilling or microfractures).

A variety of biomaterials including polymers and ceramics have been proposed for regeneration of the cartilage of OCDs, and composite scaffolds (e.g. polymers combined with ceramics), especially if seeded with autologous cells and/or GFs, seem to improve biomechanical results.

Up to now only a few clinical trials on ankle healing have been described, whereas a scaffold approach to the treatment of knee chondral lesions has been largely used in clinical practice, with excellent or good clinical results largely documented in the literature. New approaches must be considered to talus osteocondral defects in order to improve restoration. Although there are particularities of such area, other biomaterials with significant results in knee OCDs may be applied to the ankle lesions.

TERM approaches are changing the paradigms of medicine and surgical practice. However, the success of these technologies at present and in future demands deep knowledge of native tissue biology and understanding of its repair mechanisms and response to injury, as well as the new biomaterials under consideration. Basic rules of biology and other ‘basic sciences’ (understanding basic only as fundamental, never as simple) must be well known by all surgeons since only in this way will they be able to understand, adapt and assist in the development of this knowledge to clinical practice.

TERM approaches have proven efficacy in clinical cases and problems which used selection criteria not previously solved by ‘conventional’ therapeutic repair and/or replacement options. However, undiscriminating use of any promising technique is one of the most effective ways to impair or even block its proper development.


Funding statement

The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) through the POCTI and FEDER programmes, including Project OsteoCart (grant no. PTDC/CTM-BPC/115977/2009) for providing funds.


References
1. Langer R,Vacanti J. Year: 1993Tissue engineering. Science260, 920–926 (doi:10.1126/science.8493529)8493529
2. Vinatier C,Mrugala D,Jorgensen C,Guicheux J,Noel D. Year: 2009Cartilage engineering: a crucial combination of cells, biomaterials and biofactors. Trends Biotechnol.27, 307–314 (doi:10.1016/j.tibtech.2009.02.005)19329205
3. Rush SM. Year: 2010Trinity evolution: mesenchymal stem cell allografting in foot and ankle surgery. Foot Ankle Spec.3, 140–143 (doi:10.1177/1938640010369638)20508015
4. Ducheyne P,Mauck RL,Smith DH. Year: 2012Biomaterials in the repair of sports injuries. Nat. Mater.11, 652–654 (doi:10.1038/nmat3392)22825010
5. Yan LP,Oliveira JM,Oliveira AL,Caridade SG,Mano JF,Reis RL. Year: 2012Macro/microporous silk fibroin scaffolds with potential for articular cartilage and meniscus tissue engineering applications. Acta Biomater.8, 289–301 (doi:10.1016/j.actbio.2011.09.037)22019518
6. Balash P,Kang RW,Schwenke T,Cole BJ,Wimmer MA. Year: 2010Osteochondral tissue cell viability is affected by total impulse during impaction grafting. Cartilage1, 270–275 (doi:10.1177/1947603510367913)
7. El-Amin SF,Hogan MV,Allen AA,Hinds J,Laurencin CT. Year: 2010The indications and use of bone morphogenetic proteins in foot, ankle, and tibia surgery. Foot Ankle Clin.15, 543–551 (doi:10.1016/j.fcl.2010.08.001)21056855
8. Engebretsen L,et al. Year: 2010IOC consensus paper on the use of platelet-rich plasma in sports medicine. Br. J. Sports Med.44, 1072–1081 (doi:10.1136/bjsm.2010.079822)21106774
9. Furth ME,Atala A,Van Dyke ME. Year: 2007Smart biomaterials design for tissue engineering and regenerative medicine. Biomaterials28, 5068–5073 (doi:10.1016/j.biomaterials.2007.07.042)17706763
10. Dhollander AA,De Neve F,Almqvist KF,Verdonk R,Lambrecht S,Elewaut D,Verbruggen G,Verdonk PC. Year: 2011Autologous matrix-induced chondrogenesis combined with platelet-rich plasma gel: technical description and a five pilot patients report. Knee Surg. Sports Traumatol. Arthrosc.19, 536–542 (doi:10.1007/s00167-010-1337-4)21153540
11. Kreuz PC,Muller S,Freymann U,Erggelet C,Niemeyer P,Kaps C,Hirschmuller A. Year: 2011Repair of focal cartilage defects with scaffold-assisted autologous chondrocyte grafts: clinical and biomechanical results 48 months after transplantation. Am. J. Sports Med.39, 1697–1705 (doi:10.1177/0363546511403279)21540360
12. Freed LE,Vunjak-Novakovic G,Langer R. Year: 1993Cultivation of cell-polymer cartilage implants in bioreactors. J. Cell Biochem.51, 257–264 (doi:10.1002/jcb.240510304)8501127
13. Brittberg M. Year: 2010Cell carriers as the next generation of cell therapy for cartilage repair: a review of the matrix-induced autologous chondrocyte implantation procedure. Am. J. Sports Med.38, 1259–1271 (doi:10.1177/0363546509346395)19966108
14. Gurkan UA,Tasoglu S,Kavaz D,Demirci U. Year: 2012Emerging technologies for assembly of microscale hydrogels. Adv. Healthc. Mater.1, 149–158 (doi:10.1002/adhm.201200011)23184717
15. Cohen S,Leshansky L,Zussman E,Burman M,Srouji S,Livne E,Abramov N,Itskovitz-Eldor J. Year: 2010Repair of full-thickness tendon injury using connective tissue progenitors efficiently derived from human embryonic stem cells and fetal tissues. Tissue Eng. A16, 3119–3137 (doi:10.1089/ten.TEA.2009.0716)
16. Atesok K,Matsumoto T,Karlsson J,Asahara T,Atala A,Doral MN,Verdonk R,Li R,Schemitsch E. Year: 2012An emerging cell-based strategy in orthopaedics: endothelial progenitor cells. Knee Surg. Sports Traumatol. Arthrosc.20, 1366–1377 (doi:10.1007/s00167-012-1940-7)22402606
17. DeChellis DM,Cortazzo MH. Year: 2011Regenerative medicine in the field of pain medicine: prolotherapy, platelet-rich plasma therapy, and stem cell therapy: theory and evidence. Tech. Reg. Anesth. Pain Manag.15, 74–80 (doi:10.1053/j.trap.2011.05.002)
18. Che JH,Zhang ZR,Li GZ,Tan WH,Bai XD,Qu FJ. Year: 2010Application of tissue-engineered cartilage with BMP-7 gene to repair knee joint cartilage injury in rabbits. Knee Surg. Sports Traumatol. Arthrosc.18, 496–503 (doi:10.1007/s00167-009-0962-2)19855958
19. Badylak SF,Nerem RM. Year: 2010Progress in tissue engineering and regenerative medicine. Proc. Natl Acad. Sci. USA107, 3285–3286 (doi:10.1073/pnas.1000256107)20181571
20. Zengerink M,van Dijk CN. Year: 2012Complications in ankle arthroscopy. Knee Surg. Sports Traumatol. Arthrosc.20, 1420–1431 (doi:10.1007/s00167-012-2063-x)22669362
21. DeCarbo WT. Year: 2009Special segment: soft tissue matrices—Apligraf bilayered skin substitute to augment healing of chronic wounds in diabetic patients. Foot Ankle Spec.2, 299–302 (doi:10.1177/1938640009354041)20400430
22. Sheth U,Simunovic N,Klein G,Fu F,Einhorn TA,Schemitsch E,Ayeni OR,Bhandari M. Year: 2012Efficacy of autologous platelet-rich plasma use for orthopaedic indications: a meta-analysis. J. Bone Joint Surg. Am.94, 298–307 (doi:10.2106/JBJS.K.00154)22241606
23. Schliephake H. In press.. Clinical efficacy of growth factors to enhance tissue repair in oral and maxillofacial reconstruction: a systematic review. Clin. Implant Dent. Relat. Res. (doi:10.1111/cid.12114)
24. Soomekh DJ. Year: 2011Current concepts for the use of platelet-rich plasma in the foot and ankle. Clin. Podiatr. Med. Surg.28, 155–170 (doi:10.1016/j.cpm.2010.09.001)21276524
25. Lopez-Vidriero E,Goulding KA,Simon DA,Sanchez M,Johnson DH. Year: 2010The use of platelet-rich plasma in arthroscopy and sports medicine: optimizing the healing environment. Arthroscopy26, 269–278 (doi:10.1016/j.arthro.2009.11.015)20141991
26. Ruszczak Z,Friess W. Year: 2003Collagen as a carrier for on-site delivery of antibacterial drugs. Adv. Drug Deliv. Rev.55, 1679–1698 (doi:10.1016/j.addr.2003.08.007)14623407
27. Bandyopadhyay A,Yadav PS,Prashar P. Year: 2013BMP signaling in development and diseases: a pharmacological perspective. Biochem. Pharmacol.85, 857–864 (doi:10.1016/j.bcp.2013.01.004)23333766
28. Bessa PC,Casal M,Reis RL. Year: 2008Bone morphogenetic proteins in tissue engineering: the road from the laboratory to the clinic, part I (basic concepts). J. Tissue Eng. Regen. Med.2, 1–13 (doi:10.1002/term.63)18293427
29. Urist MR. Year: 1965Bone: formation by autoinduction. Science150, 893–899 (doi:10.1126/science.150.3698.893)5319761
30. Yamada N,Uchinuma E,Kuroyanagi Y. Year: 2008Clinical trial of allogeneic cultured dermal substitutes for intractable skin ulcers of the lower leg. J. Artif. Organs11, 100–103 (doi:10.1007/s10047-008-0406-7)18604614
31. Winters CL,Brigido SA,Liden BA,Simmons M,Hartman JF,Wright ML. Year: 2008A multicenter study involving the use of a human acellular dermal regenerative tissue matrix for the treatment of diabetic lower extremity wounds. Adv. Skin Wound Care21, 375–381 (doi:10.1097/01.ASW.0000323532.98003.26)18679086
32. Brigido SA. Year: 2006The use of an acellular dermal regenerative tissue matrix in the treatment of lower extremity wounds: a prospective 16-week pilot study. Int. Wound J.3, 181–187 (doi:10.1111/j.1742-481X.2006.00209.x)16984575
33. Weil L Jr. Year: 2011Biologics in foot and ankle surgery. Foot Ankle Spec.4, 249–252 (doi:10.1177/1938640011415373)21868798
34. van Dijk CN,van Sterkenburg MN,Wiegerinck JI,Karlsson J,Maffulli N. Year: 2011Terminology for Achilles tendon related disorders. Knee Surg. Sports Traumatol. Arthrosc.19, 835–841 (doi:10.1007/s00167-010-1374-z)21222102
35. Longo UG,Garau G,Denaro V,Maffulli N. Year: 2008Surgical management of tendinopathy of biceps femoris tendon in athletes. Disabil. Rehabil.30, 1602–1607 (doi:10.1080/09638280701786120)18608398
36. Ebinesan AD,Sarai BS,Walley GD,Maffulli N. Year: 2008Conservative, open or percutaneous repair for acute rupture of the Achilles tendon. Disabil. Rehabil.30, 1721–1725 (doi:10.1080/09638280701786815)18608405
37. Longo UG,Franceschi F,Ruzzini L,Rabitti C,Morini S,Maffulli N,Denaro V. Year: 2009Characteristics at haematoxylin and eosin staining of ruptures of the long head of the biceps tendon. Br. J. Sports Med.43, 603–607 (doi:10.1136/bjsm.2007.039016)18070808
38. Maffulli N,Ajis A,Longo UG,Denaro V. Year: 2007Chronic rupture of tendo Achillis. Foot Ankle Clin.12, 583–596 (doi:10.1016/j.fcl.2007.07.007)17996617
39. Sharma P,Maffulli N. Year: 2005Tendon injury and tendinopathy: healing and repair. J. Bone Joint Surg.87, 187–202 (doi:10.2106/jbjs.d.01850)15634833
40. Longo UG,Lamberti A,Maffulli N,Denaro V. Year: 2011Tissue engineered biological augmentation for tendon healing: a systematic review. Br. Med. Bull.98, 31–59 (doi:10.1093/bmb/ldq030)20851817
41. Reverchon E,Baldino L,Cardea S,De Marco I. Year: 2012Biodegradable synthetic scaffolds for tendon regeneration. Muscles Ligaments Tendons J.2, 181–18623738295
42. Moshiri A,Oryan A,Meimandi-Parizi A. Year: 2013Role of tissue-engineered artificial tendon in healing of a large Achilles tendon defect model in rabbits. J. Am. Coll. Surg.217, 421–441 (doi:10.1016/j.jamcollsurg.2013.03.025)23816385
43. Smith L,Xia Y,Galatz LM,Genin GM,Thomopoulos S. Year: 2012Tissue-engineering strategies for the tendon/ligament-to-bone insertion. Connect. Tissue Res.53, 95–105 (doi:10.3109/03008207.2011.650804)22185608
44. Chang J. Year: 2012Studies in flexor tendon reconstruction: biomolecular modulation of tendon repair and tissue engineering. J. Hand Surg.37, 552–561 (doi:10.1016/j.jhsa.2011.12.028)
45. Kew SJ,et al. Year: 2011Regeneration and repair of tendon and ligament tissue using collagen fibre biomaterials. Acta Biomater.7, 3237–3247 (doi:10.1016/j.actbio.2011.06.002)21689792
46. Kryger GS,Chong AKS,Costa M,Pham H,Bates SJ,Chang J. Year: 2007A comparison of tenocytes and mesenchymal stem cells for use in flexor tendon tissue engineering. J. Hand Surg.32, 597–605 (doi:10.1016/j.jhsa.2007.02.018)
47. Zhang X,Bogdanowicz D,Erisken C,Lee NM,Lu HH. Year: 2012Biomimetic scaffold design for functional and integrative tendon repair. J. Shoulder Elbow Surg.21, 266–277 (doi:10.1016/j.jse.2011.11.016)22244070
48. van Sterkenburg MN,van Dijk CN. Year: 2011Injection treatment for chronic midportion Achilles tendinopathy: do we need that many alternatives?Knee Surg. Sports Traumatol. Arthrosc.19, 513–515 (doi:10.1007/s00167-011-1415-2)21290104
49. Lee JY,et al. Year: 2011BMP-12 treatment of adult mesenchymal stem cells in vitro augments tendon-like tissue formation and defect repair in vivo. PLoS ONE6, e17531 (doi:10.1371/journal.pone.0017531)21412429
50. Kurtz CA,Loebig TG,Anderson DD,DeMeo PJ,Campbell PG. Year: 1999Insulin-like growth factor I accelerates functional recovery from Achilles tendon injury in a rat model. Am. J. Sports Med.27, 363–36910352775
51. de Mos M,van der Windt AE,Jahr H,van Schie HT,Weinans H,Verhaar JA,van Osch GJ. Year: 2008Can platelet-rich plasma enhance tendon repair? A cell culture study. Am. J. Sports Med.36, 1171–1178 (doi:10.1177/0363546508314430)18326832
52. Pereira DR,et al. Year: 2011Development of gellan gum-based microparticles/hydrogel matrices for application in the intervertebral disc regeneration. Tissue Eng. C17, 961–972 (doi:10.1089/ten.tec.2011.0115)
53. Oliveira JM,Sousa RA,Kotobuki N,Tadokoro M,Hirose M,Mano JF,Reis RL,Ohgushi H. Year: 2009The osteogenic differentiation of rat bone marrow stromal cells cultured with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles. Biomaterials30, 804–813 (doi:10.1016/j.biomaterials.2008.10.024)19036432
54. Sahoo S,Toh SL,Goh JCH. Year: 2010A bFGF-releasing silk/PLGA-based biohybrid scaffold for ligament/tendon tissue engineering using mesenchymal progenitor cells. Biomaterials31, 2990–2998 (doi:10.1016/j.biomaterials.2010.01.004)20089300
55. Fang Q,Chen D,Yang Z,Li M. Year: 2009In vitro and in vivo research on using Antheraea pernyi silk fibroin as tissue engineering tendon scaffolds. Mater. Sci. Eng. C29, 1527–1534 (doi:10.1016/j.msec.2008.12.007)
56. Yin Z,Chen X,Chen JL,Ouyang HW. Year: 2010Stem cells for tendon tissue engineering and regeneration. Expert Opin. Biol. Ther.10, 689–700 (doi:10.1517/14712591003769824)20367125
57. de Jonge S,de Vos RJ,Weir A,van Schie HT,Bierma-Zeinstra SM,Verhaar JA,Weinans H,Tol JL. Year: 2011One-year follow-up of platelet-rich plasma treatment in chronic Achilles tendinopathy: a double-blind randomized placebo-controlled trial. Am. J. Sports Med.39, 1623–1629 (doi:10.1177/0363546511404877)21602565
58. Enea D,et al. Year: 2012Collagen fibre implant for tendon and ligament biological augmentation. In vivo study in an ovine model. Knee Surg. Sports Traumatol. Arthrosc.21, 1783–1793 (doi:10.1007/s00167-012-2102-7)22714976
59. Longo UG,Lamberti A,Petrillo S,Maffulli N,Denaro V. Year: 2012Scaffolds in tendon tissue engineering. Stem Cells Int.2012, 517165 (doi:10.1155/2012/517165)22190961
60. Hogan MV,Bagayoko N,James R,Starnes T,Katz A,Chhabra AB. Year: 2011Tissue engineering solutions for tendon repair. J. Am. Acad. Orthop. Surg.19, 134–14221368094
61. Omae H,Zhao C,Sun YL,An K-N,Amadio PC. Year: 2009Multilayer tendon slices seeded with bone marrow stromal cells: a novel composite for tendon engineering. J. Orthopaed. Res.27, 937–942 (doi:10.1002/jor.20823)
62. Paxton JZ,Donnelly K,Keatch RP,Baar K. Year: 2009Engineering the bone-ligament interface using polyethylene glycol diacrylate incorporated with hydroxyapatite. Tissue Eng. A15, 1201–1209 (doi:10.1089/ten.tea.2008.0105)
63. Cancedda R,Giannoni P,Mastrogiacomo M. Year: 2007A tissue engineering approach to bone repair in large animal models and in clinical practice. Biomaterials28, 4240–4250 (doi:10.1016/j.biomaterials.2007.06.023)17644173
64. Muramatsu K,Doi K,Ihara K,Shigetomi M,Kawai S. Year: 2003Recalcitrant posttraumatic nonunion of the humerus. Acta Orthop. Scand.74, 95–97 (doi:10.1080/00016470310013734)12635801
65. Chou LB,Mann RA,Coughlin MJ,McPeake WT,Mizel MS. Year: 2007Stress fracture as a complication of autogenous bone graft harvest from the distal tibia. Foot Ankle Int.28, 199–201 (doi:10.3113/fai.2007.0199)17296139
66. Ramanujam CL,Sagray B,Zgonis T. Year: 2010Subtalar joint arthrodesis, ankle arthrodiastasis, and talar dome resurfacing with the use of a collagen–glycosaminoglycan monolayer. Clin. Podiatr. Med. Surg.27, 327–333 (doi:10.1016/j.cpm.2009.12.004)20470961
67. Chen Y,Bloemen V,Impens S,Moesen M,Luyten FP,Schrooten J. Year: 2011Characterization and optimization of cell seeding in scaffolds by factorial design: quality by design approach for skeletal tissue engineering. Tissue Eng. C17, 1211–1221 (doi:10.1089/ten.tec.2011.0092)
68. Khaled EG,Saleh M,Hindocha S,Griffin M,Khan WS. Year: 2011Tissue engineering for bone production: stem cells, gene therapy and scaffolds. Open Orthop. J.5(Suppl. 2), 289–295 (doi:10.2174/1874325001105010289)21886695
69. Nordsletten L. Year: 2006Recent developments in the use of bone morphogenetic protein in orthopaedic trauma surgery. Curr. Med. Res. Opin.22, S13–S17 (doi:10.1185/030079906X80585)16882365
70. Kleinschmidt K,Ploeger F,Nickel J,Glockenmeier J,Kunz P,Richter W. Year: 2013Enhanced reconstruction of long bone architecture by a growth factor mutant combining positive features of GDF-5 and BMP-2. Biomaterials34, 5926–5936 (doi:10.1016/j.biomaterials.2013.04.029)23680368
71. Agung M,Ochi M,Yanada S,Adachi N,Izuta Y,Yamasaki T,Toda K. Year: 2006Mobilization of bone marrow-derived mesenchymal stem cells into the injured tissues after intraarticular injection and their contribution to tissue regeneration. Knee Surg. Sports Traumatol. Arthrosc.14, 1307–1314 (doi:10.1007/s00167-006-0124-8)16788809
72. Oliveira JM,Kotobuki N,Tadokoro M,Hirose M,Mano JF,Reis RL,Ohgushi H. Year: 2010Ex vivo culturing of stromal cells with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles promotes ectopic bone formation. Bone46, 1424–1435 (doi:10.1016/j.bone.2010.02.007)20152952
73. Abukawa H,Shin M,Williams WB,Vacanti JP,Kaban LB,Troulis MJ. Year: 2004Reconstruction of mandibular defects with autologous tissue-engineered bone. J. Oral Maxillofac. Surg.62, 601–606 (doi:10.1016/j.joms.2003.11.010)15122567
74. Mankani MH,Kuznetsov SA,Shannon B,Nalla RK,Ritchie RO,Qin Y,Robey PG. Year: 2006Canine cranial reconstruction using autologous bone marrow stromal cells. Am. J. Pathol.168, 542–550 (doi:10.2353/ajpath.2006.050407)16436668
75. Wang H,Zhi W,Lu X,Duan K,Duan R,Mu Y,Weng J. Year: 2013Comparative studies on ectopic bone formation in porous HA scaffolds with complementary pore structures. Acta Biomater.9, 8413–8421 (doi:10.1016/j.actbio.2013.05.026)23732684
76. Florczyk S,Leung M,Li Z,Huang J,Hopper R,Zhang M. Year: 2013Evaluation of three-dimensional porous chitosan–alginate scaffolds in rat calvarial defects for bone regeneration applications. J. Biomed. Mater. Res. A101, 2974–2983 (doi:10.1002/jbm.a.34593)23737120
77. Kokemueller H,Spalthoff S,Nolff M,Tavassol F,Essig H,Stuehmer C,Bormann KH,Rücker M,Gellrich NC. Year: 2010Prefabrication of vascularized bioartificial bone grafts in vivo for segmental mandibular reconstruction: experimental pilot study in sheep and first clinical application. Int. J. Oral Maxillofac. Surg.39, 379–387 (doi:10.1016/j.ijom.2010.01.010)20167453
78. Nagata M,et al. Year: 2012A clinical study of alveolar bone tissue engineering with cultured autogenous periosteal cells: coordinated activation of bone formation and resorption. Bone50, 1123–1129 (doi:10.1016/j.bone.2012.02.631)22406494
79. Oliveira JM,Sousa RA,Malafaya PB,Silva SS,Kotobuki N,Hirose M,Ohgushi H,Mano JF,Reis RL. Year: 2011In vivo study of dendronlike nanoparticles for stem cells ‘tune-up’: from nano to tissues. Nanomedicine7, 914–924 (doi:10.1016/j.nano.2011.03.002)21419875
80. Bitton R. Year: 2009The economic burden of osteoarthritis. Am. J. Manag. Care15, 230–235
81. O'Loughlin PF,Heyworth BE,Kennedy JG. Year: 2010Current concepts in the diagnosis and treatment of osteochondral lesions of the ankle. Am. J. Sports Med.38, 392–404 (doi:10.1177/0363546509336336)19561175
82. Bhosale AM,Richardson JB. Year: 2008Articular cartilage: structure, injuries and review of management. Br. Med. Bull.87, 77–95 (doi:10.1093/bmb/ldn025)18676397
83. Shearer C,Loomer R,Clement D. Year: 2002Nonoperatively managed stage 5 osteochondral talar lesions. Foot Ankle Int.23, 651–654 (doi:10.1177/107110070202300712)12146778
84. Giannini S,Buda R,Faldini C,Vannini F,Bevoni R,Grandi G,Grigolo B,Berti L. Year: 2005Surgical treatment of osteochondral lesions of the talus in young active patients. J. Bone Joint Surg.87, 28–41 (doi:10.2106/jbjs.e.00516)16326721
85. Gobbi A,Francisco RA,Lubowitz JH,Allegra F,Canata G. Year: 2006Osteochondral lesions of the talus: randomized controlled trial comparing chondroplasty, microfracture, and osteochondral autograft transplantation. Arthroscopy22, 1085–1092 (doi:10.1016/j.arthro.2006.05.016)17027406
86. Savva N,Jabur M,Davies M,Saxby T. Year: 2007Osteochondral lesions of the talus: results of repeat arthroscopic debridement. Foot Ankle Int.28, 669–673 (doi:10.3113/fai.2007.0669)17592696
87. Zengerink M,Struijs PA,Tol JL,van Dijk CN. Year: 2010Treatment of osteochondral lesions of the talus: a systematic review. Knee Surg. Sports Traumatol. Arthrosc.18, 238–246 (doi:10.1007/s00167-009-0942-6)19859695
88. van Dijk CN,van Bergen CJ. Year: 2008Advancements in ankle arthroscopy. J. Am. Acad. Orthop. Surg.16, 635–64618978286
89. Chen H,Chevrier A,Hoemann CD,Sun J,Ouyang W,Buschmann MD. Year: 2011Characterization of subchondral bone repair for marrow-stimulated chondral defects and its relationship to articular cartilage resurfacing. Am. J. Sports Med.39, 1731–1740 (doi:10.1177/0363546511403282)21628638
90. Gomoll AH,Madry H,Knutsen G,van Dijk N,Seil R,Brittberg M,Kon E. Year: 2010The subchondral bone in articular cartilage repair: current problems in the surgical management. Knee Surg. Sports Traumatol. Arthrosc.18, 434–447 (doi:10.1007/s00167-010-1072-x)20130833
91. van Dijk CN,Reilingh ML,Zengerink M,van Bergen CJ. Year: 2010Osteochondral defects in the ankle: why painful? Knee Surg. Sports Traumatol. Arthrosc.18, 570–580 (doi:10.1007/s00167-010-1064-x)20151110
92. Martel-Pelletier J,Wildi LM,Pelletier JP. Year: 2012Future therapeutics for osteoarthritis. Bone51, 297–311 (doi:10.1016/j.bone.2011.10.008)22037003
93. Reyes R,Delgado A,Sánchez E,Fernández A,Hernández A,Evora C. In press.. Repair of an osteochondral defect by sustained delivery of BMP-2 or TGFβ1 from a bilayered alginate–PLGA scaffold. J. Tissue Eng. Regen. Med. (doi:10.1002/term.1549)
94. Holland TA,Bodde EWH,Cuijpers VMJI,Baggett LS,Tabata Y,Mikos AG,Jansen JA. Year: 2007Degradable hydrogel scaffolds for in vivo delivery of single and dual growth factors in cartilage repair. Osteoarthritis Cartilage15, 187–197 (doi:10.1016/j.joca.2006.07.006)16965923
95. Kubota K,Iseki S,Kuroda S,Oida S,Iimura T,Duarte WR,Ohya K,Ishikawa I,Kasugai S. Year: 2002Synergistic effect of fibroblast growth factor-4 in ectopic bone formation induced by bone morphogenetic protein-2. Bone31, 465–471 (doi:10.1016/s8756-3282(02)00852-9)12398941
96. Kanitkar M,Tailor HD,Khan WS. Year: 2011The use of growth factors and mesenchymal stem cells in orthopaedics. Open Orthop. J.5(Suppl. 2), 271–275 (doi:10.2174/1874325001105010271)21886692
97. Arnoczky SP,Delos D,Rodeo SA. Year: 2011What is platelet-rich plasma?Oper. Tech. Sports Med.19, 142–148 (doi:10.1053/j.otsm.2010.12.001)
98. Centeno CJ,Schultz JR,Cheever M,Robinson B,Freeman M,Marasco W. Year: 2010Safety and complications reporting on the re-implantation of culture-expanded mesenchymal stem cells using autologous platelet lysate technique. Curr. Stem Cell Res. Ther.5, 81–93 (doi:10.2174/157488810790442796)19951252
99. Qi Y,Feng G,Yan W. Year: 2012Mesenchymal stem cell-based treatment for cartilage defects in osteoarthritis. Mol. Biol. Rep.39, 5683–5689 (doi:10.1007/s11033-011-1376-z)22183306
100. Qi Y,Du Y,Li W,Dai X,Zhao T,Yan W. In press.. Cartilage repair using mesenchymal stem cell (MSC) sheet and MSCs-loaded bilayer PLGA scaffold in a rabbit model. Knee Surg. Sports Traumatol. Arthrosc. (doi:10.1007/s00167-012-2256-3)
101. Chung R,Foster BK,Xian CJ. Year: 2011Preclinical studies on mesenchymal stem cell-based therapy for growth plate cartilage injury repair. Stem Cells Int.2011, 570125 (doi:10.4061/2011/570125)21808649
102. Steinert A,Ghivizzani S,Rethwilm A,Tuan R,Evans C,Noth U. Year: 2007Major biological obstacles for persistent cell-based regeneration of articular cartilage. Arthritis Res. Ther.9, 213 (doi:10.1186/ar2195)17561986
103. Brittberg M,Lindahl A,Nilsson A,Ohlsson C,Isaksson O,Peterson L. Year: 1994Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation. New Engl. J. Med.331, 889–895 (doi:10.1056/NEJM199410063311401)8078550
104. Johnson B,Lever C,Roberts S,Richardson J,McCarthy H,Harrison P,Laing P,Makwana N. Year: 2013Cell cultured chondrocyte implantation and scaffold techniques for osteochondral talar lesions. Foot Ankle Clin.18, 135–150 (doi:10.1016/j.fcl.2012.12.008)23465953
105. Candrian C,et al. Year: 2010Are ankle chondrocytes from damaged fragments a suitable cell source for cartilage repair?Osteoarthritis Cartilage18, 1067–1076 (doi:10.1016/j.joca.2010.04.010)20434576
106. Brittberg M,Winalski CS. Year: 2003Evaluation of cartilage injuries and repair. J. Bone Joint Surg. Am.85A(Suppl. 2), 58–6912721346
107. Espregueira-Mendes J,Pereira H,Sevivas N,Varanda P,da Silva MV,Monteiro A,Oliveira JM,Reis RL. Year: 2012Osteochondral transplantation using autografts from the upper tibio-fibular joint for the treatment of knee cartilage lesions. Knee Surg. Sports Traumatol. Arthrosc.20, 1136–1142 (doi:10.1007/s00167-012-1910-0)22286745
108. Clar C,Cummins E,McIntyre L,Thomas S,Lamb J,Bain L,Jobanputra P,Waugh N. Year: 2005Clinical and cost-effectiveness of autologous chondrocyte implantation for cartilage defects in knee joints: systematic review and economic evaluation. Health Technol. Assess.9, 1–82
109. Vasiliadis HS,Wasiak J. Year: 2010Autologous chondrocyte implantation for full thickness articular cartilage defects of the knee. Cochrane Database Syst. Rev. CD003323. (doi:10.1002/14651858.CD003323.pub3)
110. Valderrabano V,Leumann A,Rasch H,Egelhof T,Hintermann B,Pagenstert G. Year: 2009Knee-to-ankle mosaicplasty for the treatment of osteochondral lesions of the ankle joint. Am. J. Sports Med.37(Suppl. 1), 105–111 (doi:10.1177/0363546509351481)
111. Hangody L,Dobos J,Baló E,Pánics G,Hangody LR,Berkes I. Year: 2010Clinical experiences with autologous osteochondral mosaicplasty in an athletic population. Am. J. Sports Med.38, 1125–1133 (doi:10.1177/0363546509360405)20360608
112. Harris JD,Siston RA,Pan X,Flanigan DC. Year: 2010Autologous chondrocyte implantation: a systematic review. J. Bone Joint Surg. Am.92, 2220–2233 (doi:10.2106/JBJS.J.00049)20844166
113. Orth P,Kaul G,Cucchiarini M,Zurakowski D,Menger MD,Kohn D,Madry H. Year: 2011Transplanted articular chondrocytes co-overexpressing IGF-I and FGF-2 stimulate cartilage repair in vivo. Knee Surg. Sports Traumatol. Arthrosc.19, 2119–2130 (doi:10.1007/s00167-011-1448-6)21350959
114. Schnabel M,Marlovits S,Eckhoff G,Fichtel I,Gotzen L,Vécsei V,Schlegel J. Year: 2002Dedifferentiation-associated changes in morphology and gene expression in primary human articular chondrocytes in cell culture. Osteoarthritis Cartilage10, 62–70 (doi:10.1053/joca.2001.0482)11795984
115. Domm C,Schünke M,Christesen K,Kurz B. Year: 2002Redifferentiation of dedifferentiated bovine articular chondrocytes in alginate culture under low oxygen tension. Osteoarthritis Cartilage10, 13–22 (doi:10.1053/joca.2001.0477)11795979
116. Kon E,Verdonk P,Condello V,Delcogliano M,Dhollander A,Filardo G,Pignotti E,Marcacci M. Year: 2009Matrix-assisted autologous chondrocyte transplantation for the repair of cartilage defects of the knee: systematic clinical data review and study quality analysis. Am. J. Sports Med.37, 156S–166S (doi:10.1177/0363546509351649)19861700
117. Mano JF,et al. Year: 2007Natural origin biodegradable systems in tissue engineering and regenerative medicine: present status and some moving trends. J. R. Soc. Interface4, 999–1030 (doi:10.1098/rsif.2007.0220)17412675
118. Agung M,Ochi M,Adachi N,Uchio Y,Takao M,Kawasaki K. Year: 2004Osteochondritis dissecans of the talus treated by the transplantation of tissue-engineered cartilage. Arthroscopy20, 1075–1080 (doi:10.1016/j.arthro.2004.04.039)15592238
119. Willers C,Chen J,Wood D,Xu J,Zheng MH. Year: 2005Autologous chondrocyte implantation with collagen bioscaffold for the treatment of osteochondral defects in rabbits. Tissue Eng. A11, 1065–1076 (doi:10.1089/ten.2005.11.1065)
120. Getgood AMJ,Kew SJ,Brooks R,Aberman H,Simon T,Lynn AK,Rushton N. Year: 2012Evaluation of early-stage osteochondral defect repair using a biphasic scaffold based on a collagen–glycosaminoglycan biopolymer in a caprine model. Knee19, 422–430 (doi:10.1016/j.knee.2011.03.011)21620711
121. Augst A,et al. Year: 2008Effects of chondrogenic and osteogenic regulatory factors on composite constructs grown using human mesenchymal stem cells, silk scaffolds and bioreactors. J. R. Soc. Interface5, 929–939 (doi:10.1098/rsif.2007.1302)18230586
122. Chen K,Shi P,Teh TKH,Toh SL,Goh JCH. In press.. In vitro generation of a multilayered osteochondral construct with an osteochondral interface using rabbit bone marrow stromal cells and a silk peptide-based scaffold. J. Tissue Eng. Regen. Med. (doi:10.1002/term.1708)
123. Wang C-C,Yang K-C,Lin K-H,Liu H-C,Lin F-H. Year: 2011A highly organized three-dimensional alginate scaffold for cartilage tissue engineering prepared by microfluidic technology. Biomaterials32, 7118–7126 (doi:10.1016/j.biomaterials.2011.06.018)21724248
124. Oliveira JM,et al. Year: 2006Novel hydroxyapatite/chitosan bilayered scaffold for osteochondral tissue-engineering applications: scaffold design and its performance when seeded with goat bone marrow stromal cells. Biomaterials27, 6123–6137 (doi:10.1016/j.biomaterials.2006.07.034)16945410
125. Abarrategi A,Lópiz-Morales Y,Ramos V,Civantos A,López-Durán L,Marco F,López-Lacomba JL. Year: 2010Chitosan scaffolds for osteochondral tissue regeneration. J. Biomed. Mater. Res. A95A, 1132–1141 (doi:10.1002/jbm.a.32912)20878984
126. Nettles DL,Vail TP,Morgan MT,Grinstaff MW,Setton LA. Year: 2004Photocrosslinkable hyaluronan as a scaffold for articular cartilage repair. Ann. Biomed. Eng.32, 391–397 (doi:10.1023/B:ABME.0000017552.65260.94)15095813
127. Løken S,Jakobsen RB,Årøen A,Heir S,Shahdadfar A,Brinchmann JE,Engebretsen L,Reinholt FP. Year: 2008Bone marrow mesenchymal stem cells in a hyaluronan scaffold for treatment of an osteochondral defect in a rabbit model. Knee Surg. Sports Traumatol. Arthrosc.16, 896–903 (doi:10.1007/s00167-008-0566-2)18592218
128. Oliveira JT,Santos TC,Martins L,Silva MA,Marques AP,Castro AG,Neves NM,Reis RL. Year: 2009Performance of new gellan gum hydrogels combined with human articular chondrocytes for cartilage regeneration when subcutaneously implanted in nude mice. J. Tissue Eng. Regen. Med.3, 493–500 (doi:10.1002/term.184)19598145
129. Oliveira JT,Santos TC,Martins L,Picciochi R,Marques AP,Castro AG,Neves NM,Mano JF,Reis RL. Year: 2010Gellan gum injectable hydrogels for cartilage tissue engineering applications: in vitro studies and preliminary in vivo evaluation. Tissue Eng. A16, 343–353 (doi:10.1089/ten.tea.2009.0117)
130. Oliveira JT,Gardel LS,Rada T,Martins L,Gomes ME,Reis RL. Year: 2010Injectable gellan gum hydrogels with autologous cells for the treatment of rabbit articular cartilage defects. J. Orthopaed. Res.28, 1193–1199 (doi:10.1002/jor.21114)
131. Oliveira JT,Martins L,Picciochi R,Malafaya PB,Sousa RA,Neves NM,Mano JF,Reis RL. Year: 2010Gellan gum: a new biomaterial for cartilage tissue engineering applications. J. Biomed. Mater. Res. A93A, 852–863 (doi:10.1002/jbm.a.32574)19658177
132. Miljkovic N,Lin Y-C,Cherubino M,Minteer D,Marra K. Year: 2009A novel injectable hydrogel in combination with a surgical sealant in a rat knee osteochondral defect model. Knee Surg. Sports Traumatol. Arthrosc.17, 1326–1331 (doi:10.1007/s00167-009-0881-2)19633829
133. Lim CT,Ren X,Afizah MH,Tarigan-Panjaitan S,Yang Z,Wu Y,Chian KS,Mikos AG,Hui JHP. Year: 2013Repair of osteochondral defects with rehydrated freeze-dried oligo[poly(ethylene glycol) fumarate] hydrogels seeded with bone marrow mesenchymal stem cells in a porcine model. Tissue Eng. A19, 1852–1861 (doi:10.1089/ten.tea.2012.0621)
134. Hui J,Ren X,Afizah M,Chian K,Mikos A. Year: 2013Oligo[poly(ethylene glycol)fumarate] hydrogel enhances osteochondral repair in porcine femoral condyle defects. Clin. Orthop. Relat. Res.471, 1174–1185 (doi:10.1007/s11999-012-2487-0)22826014
135. Jiang CC,Chiang H,Liao CJ,Lin YJ,Kuo TF,Shieh CS,Huang YY,Tuan RS. Year: 2007Repair of porcine articular cartilage defect with a biphasic osteochondral composite. J. Orthop. Res.25, 1277–1290 (doi:10.1002/jor.20442)17576624
136. Nagura I,Fujioka H,Kokubu T,Makino T,Sumi Y,Kurosaka M. Year: 2007Repair of osteochondral defects with a new porous synthetic polymer scaffold. J. Bone Joint Surg. Br.89, 258–264 (doi:10.1302/0301-620X.89B2.17754)17322449
137. Duan P,Pan Z,Cao L,He Y,Wang H,Qu Z,Dong J,Ding J. Year: 2013The effects of pore size in bilayered poly(lactide-co-glycolide) scaffolds on restoring osteochondral defects in rabbits. J. Biomed. Mater. Res. A102, 180–192 (doi:10.1002/jbm.a.34683)
138. Reyes R,Delgado A,Solis R,Sanchez E,Hernandez A,Roman JS,Evora C. In press. Cartilage repair by local delivery of transforming growth factor-β1 or bone morphogenetic protein-2 from a novel, segmented polyurethane/polylactic-co-glycolic bilayered scaffold. J. Biomed. Mater. Res. A. (doi:10.1002/jbma.34769)
139. Huang X,Yang D,Yan W,Shi Z,Feng J,Gao Y,Weng W,Yan S. Year: 2007Osteochondral repair using the combination of fibroblast growth factor and amorphous calcium phosphate/poly(L-lactic acid) hybrid materials. Biomaterials28, 3091–3100 (doi:10.1016/j.biomaterials.2007.03.017)17412414
140. Spadaccio C,Rainer A,Trombetta M,Vadalá G,Chello M,Covino E,Denaro V,Toyoda Y,Genovese J. Year: 2009Poly-L-lactic acid/hydroxyapatite electrospun nanocomposites induce chondrogenic differentiation of human MSC. Ann. Biomed. Eng.37, 1376–1389 (doi:10.1007/s10439-009-9704-3)19418224
141. Deplaine II,et al. Year: 2013Biomimetic hydroxyapatite coating on pore walls improves osteointegration of poly(L-lactic acid) scaffolds. J. Biomed Mater. Res. B101B, 173–186 (doi:10.1002/jbm.b.32831)
142. Jeong CG,Zhang H,Hollister SJ. Year: 2012Three-dimensional polycaprolactone scaffold-conjugated bone morphogenetic protein-2 promotes cartilage regeneration from primary chondrocytes in vitro and in vivo without accelerated endochondral ossification. J. Biomed. Mater. Res. A100A, 2088–2096 (doi:10.1002/jbm.a.33249)22615065
143. Christensen B,Foldager C,Hansen O,Kristiansen A,Le D,Nielsen A,Nygaard J,Bünger C,Lind M. Year: 2012A novel nano-structured porous polycaprolactone scaffold improves hyaline cartilage repair in a rabbit model compared to a collagen type I/III scaffold: in vitro and in vivo studies. Knee Surg. Sports Traumatol. Arthrosc.20, 1192–1204 (doi:10.1007/s00167-011-1692-9)21971941
144. Kon E,et al. Year: 2000Autologous bone marrow stromal cells loaded onto porous hydroxyapatite ceramic accelerate bone repair in critical-size defects of sheep long bones. J. Biomed. Mater. Res. A49, 328–337 (doi:10.1002/(sici)1097-4636(20000305)49:3<328::aid-jbm5>3.0.co;2-q)
145. Kon E,et al. Year: 2010Orderly osteochondral regeneration in a sheep model using a novel nano-composite multilayered biomaterial. J. Orthopaed. Res.28, 116–124 (doi:10.1002/jor.20958)
146. Kon E,Delcogliano M,Filardo G,Pressato D,Busacca M,Grigolo B,Desando G,Marcacci M. Year: 2010A novel nano-composite multi-layered biomaterial for treatment of osteochondral lesions: technique note and an early stability pilot clinical trial. Injury41, 693–701 (doi:10.1016/j.injury.2009.11.014)20035935
147. Sotoudeh A,Jahanshahi A,Takhtfooladi MA,Bazazan A,Ganjali A,Harati MP. Year: 2013Study on nano-structured hydroxyapatite/zirconia stabilized yttria on healing of articular cartilage defect in rabbit. Acta Cir. Bras.28, 340–345 (doi:10.1590/S0102-86502013000500004)23702935
148. Kon E,Filardo G,Robinson D,Eisman JA,Levy A,Zaslav K,Shani J,Altschuler N. In press.. Osteochondral regeneration using a novel aragonite-hyaluronate bi-phasic scaffold in a goat model. Knee Surg. Sports Traumatol. Arthrosc. (doi:10.1007/s00167-013-2467-2)
149. Gotterbarm T,Richter W,Jung M,Berardi Vilei S,Mainil-Varlet P,Yamashita T,Breusch SJ. Year: 2006An in vivo study of a growth-factor enhanced, cell free, two-layered collagen–tricalcium phosphate in deep osteochondral defects. Biomaterials27, 3387–3395 (doi:10.1016/j.biomaterials.2006.01.041)16488472
150. Bernstein A,et al. Year: 2013Microporous calcium phosphate ceramics as tissue engineering scaffolds for the repair of osteochondral defects: histological results. Acta Biomater.9, 7490–7505 (doi:10.1016/j.actbio.2013.03.021)23528497
151. Mayr HO,et al. Year: 2013Microporous calcium phosphate ceramics as tissue engineering scaffolds for the repair of osteochondral defects: biomechanical results. Acta Biomater.9, 4845–4855 (doi:10.1016/j.actbio.2012.07.040)22885682
152. Silva-Correia J,Oliveira JM,Caridade SG,Oliveira JT,Sousa RA,Mano JF,Reis RL. Year: 2011Gellan gum-based hydrogels for intervertebral disc tissue-engineering applications. J. Tissue Eng. Regen. Med.5, 97–107 (doi:10.1002/term.363)20652875
153. Silva-Correia J,Oliveira JM,Oliveira JT,Sousa RA,Reis RL. Year: 2011 Photo-crosslinked gellan gum-based hydrogels: preparation methods and uses thereof. Patent no. WO/2011/119059.
154. Silva-Correia J,Miranda-Goncalves V,Salgado AJ,Sousa N,Oliveira JM,Reis RM,Reis RL. Year: 2012Angiogenic potential of gellan-gum-based hydrogels for application in nucleus pulposus regeneration: in vivo study. Tissue Eng. A18, 1203–1212 (doi:10.1089/ten.TEA.2011.0632)
155. Scholz B,Kinzelmann C,Benz K,Mollenhauer J,Wurst H,Schlosshauer B. Year: 2010Suppression of adverse angiogenesis in an albumin-based hydrogel for articular cartilage and intervertebral disc regeneration. Eur. Cell. Mater.20, 24–3720628970
156. Kim IL,Mauck RL,Burdick JA. Year: 2011Hydrogel design for cartilage tissue engineering: a case study with hyaluronic acid. Biomaterials32, 8771–8782 (doi:10.1016/j.biomaterials.2011.08.073)21903262
157. Doral MN,et al. Year: 2012Treatment of osteochondral lesions of the talus with microfracture technique and postoperative hyaluronan injection. Knee Surg. Sports Traumatol. Arthrosc.20, 1398–1403 (doi:10.1007/s00167-011-1856-7)22205098
158. Schlichting K,Schell H,Kleemann RU,Schill A,Weiler A,Duda GN,Epari DR. Year: 2008Influence of scaffold stiffness on subchondral bone and subsequent cartilage regeneration in an ovine model of osteochondral defect healing. Am. J. Sports Med.36, 2379–2391 (doi:10.1177/0363546508322899)18952905
159. Rodrigues MT,Lee SJ,Gomes ME,Reis RL,Atala A,Yoo JJ. Year: 2012Bilayered constructs aimed at osteochondral strategies: the influence of medium supplements in the osteogenic and chondrogenic differentiation of amniotic fluid-derived stem cells. Acta Biomater.8, 2795–2806 (doi:10.1016/j.actbio.2012.04.013)22510402
160. Luyten FP,Vanlauwe J. Year: 2012Tissue engineering approaches for osteoarthritis. Bone51, 289–296 (doi:10.1016/j.bone.2011.10.007)22023933
161. Reddy S,Pedowitz DI,Parekh SG,Sennett BJ,Okereke E. Year: 2007The morbidity associated with osteochondral harvest from asymptomatic knees for the treatment of osteochondral lesions of the talus. Am. J. Sports Med.35, 80–85 (doi:10.1177/0363546506290986)16957009
162. Giannini S,Buda R,Vannini F,Di Caprio F,Grigolo B. Year: 2008Arthroscopic autologous chondrocyte implantation in osteochondral lesions of the talus. Am. J. Sports Med.36, 873–880 (doi:10.1177/0363546507312644)18227232
163. Giannini S,Buda R,Vannini F,Cavallo M,Grigolo B. Year: 2009One-step bone marrow-derived cell transplantation in talar osteochondral lesions. Clin. Orthop. Relat. Res.467, 3307–3320 (doi:10.1007/s11999-009-0885-8)19449082
164. Giza E,Sullivan M,Ocel D,Lundeen G,Mitchell ME,Veris L,Walton J. Year: 2010Matrix-induced autologous chondrocyte implantation of talus articular defects. Foot Ankle Int.31, 747–753 (doi:10.3113/FAI.2010.0747)20880476
165. Aurich M,Bedi HS,Smith PJ,Rolauffs B,Mückley T,Clayton J,Blackney M. Year: 2011Arthroscopic treatment of osteochondral lesions of the ankle with matrix-associated chondrocyte implantation. Am. J. Sports Med.39, 311–319 (doi:10.1177/0363546510381575)21068444
166. Carmont MR,Carey-Smith R,Saithna A,Dhillon M,Thompson P,Spalding T. Year: 2009Delayed incorporation of a TruFit plug: perseverance is recommended. Arthroscopy25, 810–814 (doi:10.1016/j.arthro.2009.01.023)19560648
167. Caplan A. Year: 2005Review: mesenchymal stem cells: cell based reconstructive therapy in orthopedics. Tissue Eng.11, 1198–1211 (doi:10.1089/ten.2005.11.1198)16144456
168. Giannini S,Buda R,Cavallo M,Ruffilli A,Cenacchi A,Cavallo C,Vannini F. Year: 2010Cartilage repair evolution in post-traumatic osteochondral lesions of the talus: from open field autologous chondrocyte to bone-marrow-derived cells transplantation. Injury41, 1196–1203 (doi:10.1016/j.injury.2010.09.028)20934692
169. Battaglia M,Rimondi E,Monti C,Guaraldi F,Sant'Andrea A,Buda R,Cavallo M,Giannini S,Vannini F. Year: 2011Validity of T2 mapping in characterization of the regeneration tissue by bone marrow derived cell transplantation in osteochondral lesions of the ankle. Eur. J. Radiol.80, 132–139 (doi:10.1016/j.ejrad.2010.08.008)
170. De Napoli IE,Scaglione S,Giannoni P,Quarto R,Catapano G. Year: 2011Mesenchymal stem cell culture in convection-enhanced hollow fibre membrane bioreactors for bone tissue engineering. J. Membr. Sci.379, 341–352 (doi:10.1016/j.memsci.2011.06.001)
171. Kon E,Filardo G,Condello V,Collarile M,Di Martino A,Zorzi C,Marcacci M. Year: 2011Second-generation autologous chondrocyte implantation: results in patients older than 40 years. Am. J. Sports Med.39, 1668–1675 (doi:10.1177/0363546511404675)21596901
172. Koestler W,Sidler R,Gonzalez Ballester MA,Nolte LP,Suedkamp NP,Maier D. Year: 2008A feasibility study of computer-assisted bone graft implantation for tissue-engineered replacement of the human ankle joint. Comput. Aided Surg.13, 207–217 (doi:10.3109/10929080802210814)18622795
173. Ohgushi H,Kotobuki N,Funaoka H,Machida H,Hirose M,Tanaka Y,Takakura Y. Year: 2005Tissue engineered ceramic artificial joint: ex vivo osteogenic differentiation of patient mesenchymal cells on total ankle joints for treatment of osteoarthritis. Biomaterials26, 4654–4661 (doi:10.1016/j.biomaterials.2004.11.055)15722135
174. van Bergen C,Reilingh M,van Dijk C. Year: 2011Tertiary osteochondral defect of the talus treated by a novel contoured metal implant. Knee Surg. Sports Traumatol. Arthrosc.19, 999–1003 (doi:10.1007/s00167-011-1465-5)21409468
175. Anderson DD,Tochigi Y,Rudert MJ,Vaseenon T,Brown TD,Amendola A. Year: 2010Effect of implantation accuracy on ankle contact mechanics with a metallic focal resurfacing implant. J. Bone Joint Surg.92, 1490–1500 (doi:10.2106/jbjs.i.00431)20516325
176. Heijink A,Gomoll AH,Madry H,Drobnic M,Filardo G,Espregueira-Mendes J,Van Dijk CN. Year: 2012Biomechanical considerations in the pathogenesis of osteoarthritis of the knee. Knee Surg. Sports Traumatol. Arthrosc.20, 423–435 (doi:10.1007/s00167-011-1818-0)22173730
177. Lloyd J,Elsayed S,Hariharan K,Tanaka H. Year: 2006Revisiting the concept of talar shift in ankle fractures. Foot Ankle Int.27, 793–796 (doi:10.1177/107110070602701006)17054879
178. Radin EL,Burr DB. Year: 1984Hypothesis: joints can heal. Semin. Arthritis Rheum.13, 293–302 (doi:10.1016/0049-0172(84)90031-3)6729484
179. Qiu YS,Shahgaldi BF,Revell WJ,Heatley FW. Year: 2003Observations of subchondral plate advancement during osteochondral repair: a histomorphometric and mechanical study in the rabbit femoral condyle. Osteoarthritis Cartilage11, 810–820 (doi:10.1016/S1063-4584(03)00164-X)14609534
180. Schachter AK,Chen AL,Reddy PD,Tejwani NC. Year: 2005Osteochondral lesions of the talus. J. Am. Acad. Orthop. Surg.13, 152–15815938604
181. Becher C,Huber R,Thermann H,Paessler H,Skrbensky G. Year: 2008Effects of a contoured articular prosthetic device on tibiofemoral peak contact pressure: a biomechanical study. Knee Surg. Sports Traumatol. Arthrosc.16, 56–63 (doi:10.1007/s00167-007-0416-7)17934718
182. Custers RJH,Saris DBF,Dhert WJA,Verbout AJ,van Rijen MHP,Mastbergen SC,Lafeber FPJG,Creemers LB. Year: 2009Articular cartilage degeneration following the treatment of focal cartilage defects with ceramic metal implants and compared with microfracture. J. Bone Joint Surg.91, 900–910 (doi:10.2106/jbjs.h.00668)19339575
183. Zheng MH,Willers C,Kirilak L,Yates J,Wood D,Shimmin A. Year: 2007Matrix-induced autologous chondrocyte implantation (MACI): biological and histological assessment. Tissue Eng.13, 737–746 (doi:10.1089/ten.2006.0246)17371156

Figures

[Figure ID: RSIF20130784F1]
Figure 1. 

TERM applications on the ankle joint.



[Figure ID: RSIF20130784F2]
Figure 2. 

(a) Grade 3 ulcer, (b) PRP application in wound and (c) chronic infected wound protected by collagen membrane with gentamicin sulfate.



[Figure ID: RSIF20130784F3]
Figure 3. 

(a) Achilles tendon defect partial rupture identified in T2 MRI (arrow) and (b) endoscopic view of the defect.



[Figure ID: RSIF20130784F4]
Figure 4. 

Photograph of the gellan gum microparticles obtained by precipitation in a phosphate buffered saline (pH 7.4) solution and possessing a size between 500 and 2000 µm.



[Figure ID: RSIF20130784F5]
Figure 5. 

(a) Scanning electron microscopy image of MSCs seeded onto SPCL scaffolds and maintained in a standard osteogenic culture medium, after 14 days of culturing. Microscopy images of histological sections (haematoxylin and eosin staining) of (b) SPCL scaffold controls and (c) MSCs/SPCL construct explants after four weeks of implantation (Fischer rats subcutaneous model). Newly bone formed (NB), SPCL fibres (F) and fibrous tissue (FT).



[Figure ID: RSIF20130784F6]
Figure 6. 

Photographs of gellan gum hydrogels: (a) single and (b) bilayered.



[Figure ID: RSIF20130784F7]
Figure 7. 

(a) Photograph of TruFit PLGA-based scaffold delivery device, (b) defect zone prepared to receive the plug and (c) arthroscopically implanted device to resurface the defect preserving joint congruency.



[Figure ID: RSIF20130784F8]
Figure 8. 

(a) Per-operative photograph of Hemicap ankle implant after tibial osteotomy and control X-ray in (b) frontal and (c) lateral views at 1 year follow-up.



Tables
[TableWrap ID: RSIF20130784TB1] Table 1. 

Biomaterials used in the preparation of scaffolds for osteochondral tissue regeneration.


repeating unit properties examples of proposed applications
natural polymers
collagen it is the most abundant protein in the body. It possesses high mechanical strength, good biocompatibility and low antigenicity, which make it suitable for tissue engineering. Combinations of other materials are also described, as well as GFs or cell implantation atelocollagen gel was reported to be successfully used on OCDs on talar dome [118]
collagen bioscaffold seeded with autologous chondrocyte for the treatment of OCDs in rabbit knee [119]
collagen biphasic-based scaffolds were used in OCDs of the goat and compared to PLGA. Both provide indications of satisfactory development of a structural repair [120]
silk fibroin it contains a highly repetitive primary sequence that leads to a high content of β-sheets, responsible for the good mechanical properties of silk fibres. It has been shown to be a biocompatible material that allows good cell attachment, providing an adequate three-dimensional porous structure and the necessary mechanical support for bone and cartilage tissue generation porous silk scaffolds, bioreactors and BMSCs were used to engineer cartilage- or bone-like tissue constructs [121]
silk fibroin scaffolds were reported to be suitable for use in meniscus and cartilage tissue-engineered scaffolding [5]
rabbit BMSC/silk fibroin scaffold-based co-culture approach was used to generate tissue-engineered osteochondral grafts [122]
alginate it is non-toxic, biocompatible and biodegradable natural polymer that is widely applied in drug and cell delivery systems. Hydrogel formation can be obtained by interactions of anionic alginates with multivalent inorganic cations by simple ionotropic gelation method. Hydrophilic polymeric network of three-dimensional cross-linked structures of hydrogels absorbs substantial amount of water or biological fluids alginate droplets were gelated to form a highly organized scaffold and the feasibility of the use of this scaffold in cartilage tissue engineering was demonstrated [123]
alginate-based bilayered scaffolds loaded with GFs on rabbit knee [93]
chitosan it is a derivative of chitin and partially de-acetylated. Structurally, chitosan is a linear polysaccharide that shares some characteristics with various glycosaminoglycans and hyaluronic acid present in articular cartilage, composed of glucosamine and N-acetyl glucosamine. Some important properties are its biocompatibility, biodegradability, antibacterial activity, mucoadhesivity and wound-healing ability development of novel hydroxyapatite/chitosan bilayered scaffold that shows potential for being used in TE of OCDs [124]
appropriate chitosan properties were evaluated for an in vivo osteochondral tissue regeneration on rabbit knee [125]
hyaluronic acid one of the most important components of the ECM. Is soluble in water and can form hydrogels by covalent and photo-cross-linking, esterification and annealing. It is enzymatically degraded by hyaluronidase. The degradation products of hyaluronan, the oligosaccharides and very low-molecular-weight hyaluronan exhibit pro-angiogenic properties and can induce inflammatory responses in macrophages and dendritic cells in injured tissues in situ photo-cross-linkable hyaluronan was developed and evaluated as a scaffold for articular cartilage repair in vitro [126]
MSCs were seeded in a hyaluronan scaffold for repair of an OCD in rabbit knee [127]
gellan gum it forms thermoreversible gels possessing mechanical properties varying from soft to elastic. Presents no toxicity and it could be used in a non-invasive manner. Similar structure to native cartilage glycosaminoglycans gellan gum adequately supported the growth and ECM deposition of human articular chondrocytes implanted subcutaneously in nude mice [128]
successful encapsulation of human nasal chondrocytes on gellan gum [129]
gellan gum hydrogels seeded with autologous cells proved to be a promising approach in treatment of cartilage defects in rabbit knee [129,130]
synthetic polymers
poly(ethylene glycol) derivatives synthetic hydrogels are water-swollen polymeric networks, usually consisting of cross-linked hydrophilic polymers that can swell, but do not dissolve in water. This ability to swell under biological conditions makes them an ideal class of materials for biomedical applications, such as drug delivery systems and tissue engineering scaffolds for cell encapsulation. Hydrogels possess a three-dimensional network structure, cross-linked together either physically or chemically. This insoluble cross-linked structure allows effective immobilization and release of active agents and biomolecules or even cells. Generally exhibit good biocompatibility and high permeability to gases, nutrients and other water-soluble metabolites, making them attractive scaffolds poly(ethylene glycol)-based hydrogels used in osteochondral knee defect in rats [132]
oligo[poly(ethylene glycol) fumarate] hydrogel alone or loaded with BMSCs to endorse fully repair of OCDs on porcine model [133,134]
PLGA biodegradable and biocompatible and having mechanical strength, suitable for cartilage repair. It can be tuned with different pore size along the scaffold and combined with other polymers, for example polyurethane. It is suitable for seeding with BMSCs and GFs biphasic cylindrical porous plug of PGLA with β-tricalcium phosphate was used to repair articular cartilage in porcine model [135]
PLGA scaffold was implanted into OCDs on femoral trochlea of rabbits [136]
bilayered porous scaffolds seeded with BMSCs for regeneration of OCDs on rabbit knee [137]
PLGA-based bilayered scaffolds loaded with GFs on rabbit knee [138]
poly(L-lactic acid) (PLLA) biodegradable polyester that exhibits mechanical properties suitable for bone tissue regeneration. It degrades by hydrolytic scission of its ester bonds, yielding the physiologic molecule lactic acid. As a biodegradable material, it is suitable for tissue engineering, owing to the fact that the newly formed tissue can invade the space while the material degrades PLLA-based scaffold incorporated with GFs was used to repair articular cartilage defect in a rabbit model [139]
PLLA/hydroxyapatite nanocomposites induced differentiation of hMSCs in a chondrocyte-like phenotype with generation of a proteoglycan-based matrix [140]
optimization of the mineralization process on a PLLA macroporous scaffold on OCDs performed in the medial femoral condyle of healthy sheep [141]
polycaprolactone (PCL) it is one of the most widely used biodegradable polyesters for medical application owing to its slow biodegradability, biocompatibility, mechanical properties and structural flexibility. PCL expresses slow degradation kinematics and its degradation products are harmlessly metabolized in the tricarboxylic acid cycle three-dimensional PCL scaffolds with BMP-2 were applied to investigate the influence of BMP-2 on cartilage matrix and bone matrix production [142]
nanostructured porous PCL scaffold was developed to stimulate articular cartilage repair. It improved chondrocytic differentiation to produce more hyaline-like tissue [143]
ceramics chemical structure properties examples of proposed applications
hydroxyapatite Ca10(PO4)6(OH)2 it presents high biocompatibility, but low strength and fracture toughness, which may be a problem in OCD engineering. The osteocondutive properties of hydroxyapatite-based materials can be improved by manipulation of the structural characteristics implants load with BMSCs have proved to be useful in bone repair of sheep long bones [144]
trilayered scaffold with collagen and hydroxyapatite used on osteochondral regeneration in the femoral condyles of the sheep [145,146]
composed with zirconia has been proved to be an effective scaffold for cartilage tissue engineering [147]
aragonite Ca(CO3) it is a biological material very similar to bone, including its three-dimensional structure and pore interconnections that confer osteoconductive ability. Nevertheless, the native material does not regenerate hyaline cartilage aragonite–hyaluronate bi-phasic scaffold showed cartilage regenerative potential in a goat model [148]
tricalcium phosphate Ca3(PO4)2 it is a calcium salt of phosphoric acid, widely used as a synthetic alternative owing to their chemical similarity to the mineral part of the bone. Presents a high osteoconductivity and a cell-mediated resorption. Calcium and phosphate ions released during the resorption can be used to mineralize new bone in the bone remodelling process. It may be used alone or in combination with a biodegradable and resorbable polymer, for example polyglycolic acid tricalcium phosphate-based scaffold loaded with GFs was reported to induce chondrogenic differentiation, tissue formation and differentiation in a mini-pig model [149]
microporous three-dimensional calcium phosphate was seeded with autologous chondrocytes and implanted in femoral condyle of ovine knees [150,151]

[TableWrap ID: RSIF20130784TB2] Table 2. 

Clinical studies on TE of cartilage/OCD of the ankle.


references biomaterial/treatment approach defect area/follow-up procedure outcome
Giannini et al. [162] Hyalograft C scaffold seeded with human autologous chondrocytes ankle/12 and 36 months patients (n = 46) with a mean age of 31.4 years, post-traumatic talar dome lesions. First procedure: ankle arthroscopy to harvest cartilage. Chondrocytes were cultured on Hyalograft C scaffold. In the second step, the construct was arthroscopically implanted into the lesion site. Patients were evaluated by AOFAS score pre-operatively and at 12 and 36 months post-surgery the mean pre-operative AOFAS score was 57.2 ± 14.3. After 12 and 36 months, the scores were 86.8 ± 13.4 and 89.5 ± 13.4, respectively. Clinical results were significantly related to the age of patients and to previous operations for cartilage repair. Histological stainings have revealed that hyaline-like cartilage was formed
Giannini et al. [163] collagen powder/hyaluronan membrane loaded with concentrated BMDCs ankle/6, 12, 18 and 24 months patients (n = 23) used collagen/MSCs, and 25 patients used hyaluronan/MSCs for the treatment. Porcine collagen powder (Spongostan Powder) and hyaluronic acid membrane (HYAFF-11) were used. At first, bone marrow was harvested and concentrated. Then, the collagen powder or hyaluronan membrane was mixed with bone marrow and platelet-rich fibrin gel and composites were implanted for the collagen powder group, the mean AOFAS scores of pre-operation and 24 months post-operation were 62.5 ± 18 and 89.8 ± 9.8, respectively. In the hyaluronic acid group, the scores increased from 66.2 ± 10.5 to 92.8 ± 5.3, 24 months after the surgery. At 2 years follow-up, MRIs showed the restoration of the cartilage layer and subchondral bone of the patients
Giza et al. [164] collagen type I/III bilayered membrane with autologous chondrocytes ankle/1 and 2 years patients (n = 10) with average age of 40.2 years. The size and location of the defects were analysed by ankle arthroscopy, and cartilage was also harvested from the border or the lesion. Expanded chondrocytes were seeded into the collagen membrane. The joint was exposed with a small anterolateral or anteromedial approach, without malleolar osteotomy. The graft was cut and placed into the defect on top of a layer of fibrin sealant the AOFAS hindfoot scores increased from 61.2 (pre-operative, ranged from 42 to 76) to 74.7 (1 year post-operative, ranged from 46 to 87) and 73.3 (2 year post-operative, ranged from 42 to 90). At 19 months post-operation, MRIs showed the regeneration of articular cartilage and subchondral bone
Aurich et al. [165] collagen type I scaffold with autologous chondrocytes (MACI) ankle/mean follow-up 24.5 months patients (n = 18, with a total of 19 defects) with mean age of 29.2. Arthroscopy was used for the evaluation and debridement on the defects, as well as the harvest of cartilage. Cultured chondrocytes were seeded into the collagen membrane and implanted in the defects, with fibrin as the glue. MOCART score, the pain and disability module of the foot function index (FFI), AOFAS score and the core scale of the foot and ankle module of the American Academy of Orthopaedic Surgeons (AAOS) lower limb outcomes assessment instruments were used according to AOFAS hindfoot score, 64% were rated as excellent and good, whereas 36% were rated fair and poor. The results correlated with the age of the patient and the duration of symptoms, but not with the size of the lesion. Mean MOCART score was 62.4 ± 15.8 points. There was no relation between MOCART score and the clinical outcome


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Keywords: ankle, biomaterials, osteochondral lesions, regenerative medicine, scaffold, tissue engineering.

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