Morphological study on the effects of sample size on ovarian tissue vitrification.

Objective: The present study aimed to assess the effects of ovarian cortex sample size on tissue morphological integrity after vitrification in a metal capsule.

Methods: Bovine ovarian tissue samples cut in large and small fragments (1x1x5 and 1x1x3 mm, respectively - 5 and 3 mm refer to length), vitrified in a metal capsule were fixed for histological analysis immediately after rewarming or after 48 hours culture. We assessed primordial, primary and secondary follicle morphology and stromal integrity.

Results: Primordial follicles showed the highest rates of normal morphology after rewarming and after 48 hours culture in both, small and large tissue fragments. Primary follicles presented a significant drop in normal morphology in large samples, after 48 hours in culture. Stromal integrity was well-preserved immediately after rewarming in small and large fragments but presented a significant drop in normal morphology in large samples, after 48 hours in culture.

Conclusions: The ovarian reserve, represented by Primordial follicles, is well-preserved in small or large fragments, after vitrification and culture. However, the stromal components present better preservation after vitrification\rewarming, when tissue samples are cut in small fragments. Thus, small cortex samples should be preferred for ovarian tissue vitrification.