Document Detail


In situ permeability measurement of the mammalian lacunar-canalicular system.
MedLine Citation:
PMID:  20080221     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Bone is capable of adapting its mass and structure under mechanical cues. Bone cells respond to various mechanical stimuli including substrate strain, fluid pressure, and fluid flow (shear stress) in vitro. Although tissue-level strains are well documented experimentally, microfluidic parameters around bone cells are quantified mainly through theoretical modeling. A key model parameter, the Darcy permeability of the bone lacunar-canalicular system (LCS), is difficult to measure using traditional methods due to the co-existence of the larger vascular and smaller LCS porosities. In this paper, we developed a novel method to measure the LCS permeability by rapid compaction of intact mammalian bones and recording the intramedullary pressure (IMP). Six canine metacarpals were subjected to three step compression tests with peak loads of 50, 100, or 200lbs, while the IMP was simultaneously recorded using a catheter pressure transducer. The loading ramp time was chosen to be ~2ms, which was long enough to allow pressure equilibrium to be established between the marrow cavity and the vascular pores, but short enough to observe the LCS fluid flowing into and out of the vascular pores. This loading scheme permitted us to differentiate the contribution of the two intermingled porosities to the IMP responses. The time constant of the IMP pressurization and relaxation due to the LCS was found to be 8.1+/-3.6s (n=18). The mid-shaft cortex of the metacarpals mainly consisted of osteons with an average radial thickness of 65+/-27microm, which served as the characteristic distance for the LCS fluid to relax. The LCS permeability was obtained via poroelastic analysis to be 2.8+/-1.8x10(-)(23)m(2), which was smaller than previous theoretical predictions (order of 10(-)(19) to 10(-)(22)m(2)), but within the range of previous experimentally based estimations (order of 10(-)(22) to 10(-)(25)m(2)). Our results also show that osteoblasts and osteocytes experience hydraulic pressures that differ by three orders of magnitude under physiological compressive strains. These estimates of the in vivo mechanical environments may be used to design in vitro models for elucidating the cellular and molecular mechanisms of bone adaptation and pathological bone loss.
Authors:
Joseph D Gardinier; Chris W Townend; Kei-Peng Jen; Qianhong Wu; Randall L Duncan; Liyun Wang
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2010-01-18
Journal Detail:
Title:  Bone     Volume:  46     ISSN:  1873-2763     ISO Abbreviation:  Bone     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-03-19     Completed Date:  2010-06-28     Revised Date:  2011-07-27    
Medline Journal Info:
Nlm Unique ID:  8504048     Medline TA:  Bone     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1075-81     Citation Subset:  IM    
Copyright Information:
Copyright 2010 Elsevier Inc. All rights reserved.
Affiliation:
Department of Biomechanics and Movement Science, University of Delaware, Newark, DE 19716, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Compressive Strength
Dogs
Haversian System / physiology*
Models, Biological
Osteocytes / physiology*
Permeability
Porosity
Stress, Mechanical
Weight-Bearing
Grant Support
ID/Acronym/Agency:
AR043222/AR/NIAMS NIH HHS; AR054385/AR/NIAMS NIH HHS; P20 RR016458-085664/RR/NCRR NIH HHS; P20RR016458/RR/NCRR NIH HHS; R01 AR043222-09/AR/NIAMS NIH HHS; R01 AR054385-03/AR/NIAMS NIH HHS; R01 AR054385-05/AR/NIAMS NIH HHS
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