Cryopreservation of immature bovine oocytes with 1,2 propanediol

Abstract

A study was carried out to investigate the ability of immature bovine cumulus-oocytes complexes to survive cryopreservation and undergo subsequent in vitro maturation in two different levels of propanediol (PROH). Treatment 1 consisted of subjecting oocytes to a gradual 3-step, concentration-driven dehydration with PROH (0.53; 1.06 and 1.6 M) at room temperature and subsequent freezing. Oocytes were thawed in water at 37ºC for 30 seconds and subjected to a gradual 3-step, concentration-driven rehydration with PROH (1.6; 1.06 and 0.53 M) in the presence of 0.25 M sucrose. Treatment 2 was conducted the same way, but PROH concentrations for dehydration were 0.7; 1.4 and 2.0 M and for rehydration were 2.0; 1.4 and 0.7 M. After rehydration, oocytes of both treatments were washed in TCM 199 medium followed by the in vitro maturation. The control consisted of nonfrozen oocytes. Oocytes of all groups were cultured in TCM 199 medium with 10% ECS and FSH, and 5% CO₂ air in co-culture at 39ºC, for 24 hours. The in vitro maturation rate of cryopreserved oocytes were different for treatments and control. Metafase II was reached by 2.04%, 0% and 84% for treatment 1, 2 and control, respectively.