Inhibition by human embryos of mouse granulosa cell progesterone production: development of a sensitive bioassay

Reproduction technologies could be improved by the development of methods t o evaluate oocyte or embryo quality in a non-invasive, quantitative manner. Since human embryos secrete a factor that inhibits granulosa cell progeste rone production, an interspecies bioassay was established to investigate wh ether the presence of this progesterone-inhibitory factor (PIF) in human em bryo-conditioned (HEC) media is related to the health and developmental cap acity of the embryos. Oocytes were microsurgically removed from oocyte-cumu lus complexes isolated from superovulated mouse ovaries, and the oocytectom ized complexes were cultured in HEC media in the presence of follicle stimu lating hormone and testosterone. Progesterone accumulation in the media was determined by radio-immunoassay, Despite the potential limitations of very small volumes of HEC media to evaluate, and the need to freeze these media at the source, the bioassay was able to detect PIF activity in HEC media. Most embryos produced PIF activity, but the degree of inhibition was not co rrelated with the ability of oocytes to be fertilized, nor with embryo morp hology or ability to cleave and develop after transfer. These results demon strate that secretion of PIF by human embryos can be measured by this bioas say and that human PIF can inhibit murine granulosa cell steroidogenesis; h owever, PIF activity is not correlated with human embryo quality or develop mental competence.