Goat and sheep ovarian tissue cryopreservation: Effects on the morphology and development of primordial follicles and density of stromal cell

The effect of exposure to cryoprotectant and cryopreservation of goat and sheep ovarian cortical fragments on the morphology of primordial follicles, stromal cell density and follicular development was performed. Goat and sheep ovarian fragments were exposed to 1.0 or 1.5 M ethylene glycol (EG) for 5, 10 or 20 min, followed or not by conventional cryopreservation. Follicular morphology and stromal cell density were evaluated by means of classical histological analysis. In addition, ovarian fragments were cultured for 1 or 7 days after cryopreservation to evaluate follicular development. Both exposure to cryoprotectant and cryopreservation of goat and sheep ovarian tissue did affect the morphology of primordial follicles and stromal cell density, except when goat ovarian tissue was exposed to EG for 5 min. Although exposure time did not influence follicular morphology in both species, increase in the exposure time from 5 to 20 min did reduce goat stromal cell density. Increase in EG concentration from 1.0 to 1.5 M did result in the decrease of the percentage of goat morphologically normal primordial follicles evaluated after exposure only. In vitro culture of frozen–thawed goat and sheep ovarian tissue showed that exposure to 1.0 M, for 10 min, before freezing of goat and sheep ovarian tissue does not impair follicular developmental capacity. In addition, stromal cell density may play a role in follicular survival and development after cryopreservation of ovarian tissue.