Gonadotropin-Induced Δ14-Reductase and Δ7-Reductase Gene Expression in Cumulus Cells during Meiotic Resumption of Porcine Oocytes

Progesterone is produced from cholesterol in cumulus cells during meiotic resumption of porcine oocytes. In follicular cells, it has been shown that exogenous lipoprotein-bound cholesterol ester can be used for steroid hormone production. However, in serum-free medium, progesterone is also secreted by FSH- and LH-stimulated cumulus-oocyte complexes, suggesting that progesterone could be produced from de novo synthesized cholesterol in cumulus cells. In the present study, we investigated the expression of Δ14-reductase and Δ7-reductase, which are the members of the superfamily that converts acetyl-CoA to cholesterol in cumulus cells. The expression of both genes was analyzed by RT-PCR. Both Δ14-reductase mRNA and Δ7-reductase mRNA in cumulus cells, cultured until 4 h, were under the level of detection limit. In response to gonadotropins, both mRNA levels were dramatically up-regulated, reaching a maximum at 20 h. To clarify the role of induced enzymes in cumulus cells, cumulus-oocyte complexes were culture...