Efficiency of non-protein solutions using hydroxypropyl cellulose on survival of bovine and human oocytes and embryos after vitrification

Abstract

Vitrification is an alternative method of cryopreservation in ART, resulting in significantly improved survival rates of oocytes and embryos, and with excellent clinical outcomes. To reduce risk of viral contamination, government regulators have stipulated that non-serum substitutes must be used ART. The purpose of this study was to test the efficacy of a synthetic macromolecule, hydroxypropyl cellulose (HPC), for use as a supplement in vitrification solutions. In vitro survival and clinical outcome of bovine and human oocytes and blastocysts after vitrification using non-protein vitrification solutions containing HPC were examined and compared with conventional vitrification method. Four experiments were conducted to assess the efficacy of non-protein VS for oocytes and blastocysts. Four-hundred and twenty bovine oocytes and 300 blastocysts and 154 human oocytes were vitrified by the Cryotec method(Kuwayama, 2013). The solutions for vitrification were supplemented with 0.06 mg/ml HPC or with 10%SSS or with no added macromolecule (NA). Some HPC solutions and SSS solutions were stored at 4ºC or -80ºC for 12months before vitrification. The survival rates of bovine oocytes vitrified in HPC, SSS and NA were 100%, 100% and 86% and the respective blastocyst rates were 22%, 18% and 8%, respectively. The survival rates of bovine blastocysts vitrified in HPC, SSS and NA were 99%, 93% and 88%, respectively.The survival rate of bovine oocytes vitrified in HPC solutions stored for 12 months at 4°C or -80°C was 100%; the rates for those vitrified in SSS solutions were somewhat lower than HPC. The survival rates of human oocytes vitrified in HPC, SSS and NA were 100%, 98% and 92%, respectively. High morphological in vitro survival and growth of bovine and human oocytes, and also bovine blastocysts after vitrification using the solutions containing HPC suggest that this supplement can be effective for human oocytes and embryos vitrification.