Zinc Chloride Supplementation during Ovarian Cortex Vitrification Improves in Vitro Follicular Development in Pigs

Vitrification is the fast freezing method of cryopreservation that causes oxidative stress damage on tissues therefore affecting the quality and development of tissues. An antioxidant, zinc chloride, reduces damage caused by reactive oxygen species in vitrification. The objective of this study was to determine the effects of zinc chloride supplementation in vitro, during porcine ovarian cortex vitrification, on in vitro follicle development. The cortexes (3 x 3 x 1 mm, n = 20) were isolated from cycling gilt ovaries (n = 10) and incubated in equilibrium solution (0, 5 μg/mL ZnCl₂) followed by vitrification solution (0, 5 μg/mL ZnCl₂) for 5 min each then plunged and stored into liquid nitrogen for 7 d. Ovarian sections were thawed in oocyte maturation media, cultured for 48 h, then fixed in formalin. Sections were subjected to histological assessment and follicle morphology was assessed. The results of this study suggest that supplementing zinc chloride during the vitrification process improves follicle integrity and recovery from the vitrification process in pigs.