Document Detail

Effect of maturation stage at cryopreservation on post-thaw cytoskeleton quality and fertilizability of equine oocytes.
MedLine Citation:
PMID:  16477611     Owner:  NLM     Status:  MEDLINE    
Oocyte cryopreservation is a potentially valuable technique for salvaging the germ-line when a valuable mare dies, but facilities for in vitro embryo production or oocyte transfer are not immediately available. This study examined the influence of maturation stage and freezing technique on the cryopreservability of equine oocytes. Cumulus oocyte complexes were frozen at the immature stage (GV) or after maturation in vitro for 30 hr (MII), using either conventional slow freezing (CF) or open pulled straw vitrification (OPS); cryoprotectant-exposed and untreated nonfrozen oocytes served as controls. After thawing, GV oocytes were matured in vitro, and MII oocytes were incubated for 0 or 6 hr, before staining to examine meiotic spindle quality by confocal microscopy. To assess fertilizability, CF MII oocytes were subjected to intracytoplasmic sperm injection (ICSI) and cultured in vitro. At 12, 24, and 48 hr after ICSI, injected oocytes were fixed to examine their progression through fertilization. Both maturation stage and freezing technique affected oocyte survival. The meiosis resumption rate was higher for OPS than CF for GV oocytes (28% vs. 1.2%; P < 0.05), but still much lower than for controls (66%). Cryopreserving oocytes at either stage induced meiotic spindle disruption (37%-67% normal spindles vs. 99% in controls; P < 0.05). Among frozen oocytes, however, spindle quality was best for oocytes frozen by CF at the MII stage and incubated for 6 hr post-thaw (67% normal); since this combination of cryopreservation/IVM yielded the highest proportion of oocytes reaching MII with a normal spindle (35% compared to <20% for other groups), it was used when examining the effects of cryopreservation on fertilizability. In this respect, the rate of normal fertilization for CF MII oocytes after ICSI was much lower than for controls (total oocyte activation rate, 26% vs. 56%; cleavage rate at 48 hr, 8% vs. 42%: P < 0.05). Thus, although IVM followed by CF yields a respectable percentage of normal-looking MII oocytes (35%), their ability to support fertilization is severely compromised.
T Tharasanit; B Colenbrander; T A E Stout
Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Molecular reproduction and development     Volume:  73     ISSN:  1040-452X     ISO Abbreviation:  Mol. Reprod. Dev.     Publication Date:  2006 May 
Date Detail:
Created Date:  2006-03-02     Completed Date:  2006-06-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8903333     Medline TA:  Mol Reprod Dev     Country:  United States    
Other Details:
Languages:  eng     Pagination:  627-37     Citation Subset:  IM    
Copyright Information:
Mol. Reprod. Dev. (c) 2006 Wiley-Liss, Inc.
Faculty of Veterinary Medicine, Department of Equine Sciences, Utrecht University, Yalelaan, Utrecht, The Netherlands.
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MeSH Terms
Cell Survival / physiology
Cytoskeleton* / metabolism
Meiosis* / physiology
Mitotic Spindle Apparatus / metabolism
Oocytes / cytology*,  metabolism
Sperm Injections, Intracytoplasmic*

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