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Evaluation of Apoptotic Markers and Tissue Histology Indicate a Slight Advantage of Slow Freezing Method over Vitrification for Sheep Ovarian Tissues.

BACKGROUND
An efficient cryopreservation method is very important for preserving the fertility of sheep ovarian tissues.


OBJECTIVE
To compare the slow freezing method and vitrification for cryopreservation of sheep ovarian tissues.


METHODS
Dissected cortex fragments from ten sheep ovaries were used for the comparative study. Cryopreserved and control tissues were cultured for 24h and then evaluated according to follicular morphology and apoptotic assessment.


RESULTS
In both slow freezing and vitrification methods, normal follicles were reduced when compared to the non-frozen control group. There were significantly more abnormal follicles with vitrification than with slow freezing method (P < 0.05). However, there were no significant differences with regard to apoptotic gene expression or the percentage of Caspase3 positive follicles among cryopreserved and control groups.


CONCLUSION
A slight advantage of the slow freezing method was observed over vitrification for cryopreservation of sheep ovarian tissue fragments.