Effects of pre-treating in vitro-matured bovine oocytes with the cytoskeleton stabilizing agent taxol prior to vitrification

The purpose of this study was to determine the efficacy of pre-treating mature bovine oocytes with Taxol before vitrification by the open pulled Straw method (OPS). We evaluated the effects of pre-treating the oocytes with 1 microM Taxol on chromosome organization, spindle morphology, cortical granule distribution and the ability of fertilized oocytes to develop to the blastocyst stage. After calf or cow oocyte vitrification without Taxol, significantly higher proportions of spindle abnormalities in the form of abnormal spindle structures or dispersed or decondensed chromosomes were observed compared to fresh control oocytes. In contrast, when we compared calf oocytes pre-treated with Taxol before vitrification with control calf oocytes, similar percentages of oocytes showing a normal spindle morphology were observed. The percentages of oocytes with a peripheral cortical granule (CG) distribution increased when the oocytes were pretreated with Taxol and vitrified, while oocytes vitrified without Taxol pre-treatment gave rise to higher cortical distribution percentages. Cleavage and blastocyst rates were significantly lower for vitrified versus untreated oocytes, both in cow and calf oocytes. Significantly higher cleavage rates were obtained when calf and cow oocytes were vitrified with Taxol. Pre-treatment with Taxol before cow oocyte vitrification yielded significantly higher blastocyst rates. Calf oocytes, however, were unable to develop to the blastocyst stage, irrespective of previous Taxol treatment. These results indicate that the pre-treatment of oocytes with Taxol before vitrification helps to reduce the damage induced by the cryopreservation process, and potentially improves the subsequent development of vitrified bovine oocytes. Summary sentence: Pre-treatment of oocytes with Taxol before vitrification helps to reduce the damage induced by vitrification and potentially improves the development of vitrified bovine oocytes.