A Noninvasive Method for Assessing Oocyte Competency

Abstract

<jats:p>There is an increasing demand to evaluate oocyte competency and viability for oocyte cryopreservation and use for in vitro fertilization. Oocytes suffer decreased survival of cryopreservation as compared to embryos, due to physical characteristics of the oocyte. The objective of this study is to determine if a specific gravity device (SGD) can estimate oocyte viability based on oocyte descent through the buoyancy system. All experiments were performed in a research laboratory with a randomized block design with repeated measures. Three hundred-seventy-six oocytes were collected from seven mice and randomly assigned to one of four treatments: exposure to 60C for 30 min, acidified media for 1h, ethylene glycol-glycerol cryoprotectant for 1h, or standard culture to serve as control. To further analyze the relationship between oocyte descent time and viability, 98 additional oocytes were passed through SGD before and after treatment. Oocytes were stained with Coomassie Blue to determine membrane permeability and estimate viability based on treatment. Oocytes treated with 60C heat, acidified media and ethylene glycol/ glycerol cryoprotectant solution demonstrated altered descent times from control and pre-treatment oocytes (P&lt;0.05). Oocytes exposed to heat and cryoprotectants descended more rapidly through SGD than control and pre-treatment oocytes (P&lt;0.05). Oocytes treated with acidified media descended more slowly through SGD (P&lt;0.05). Permeation of stain into oocytes exposed to lethal treatments confirmed changes in membrane integrity post-treatment and further indicates SGD can detect such shifts. This suggests SGD can predict competency between live and dead oocytes. In conclusion, SGD can detect shifts in oocyte density due to altered membrane permeability, which can suggest information about oocyte competency. This information can help differentiate between high- and low-quality fresh oocytes to help select which oocytes to freeze and result in improved oocyte cryopreservation and fertilization.</jats:p>