Deletion of RhoA in Progesterone Receptor–Expressing Cells Leads to Luteal Insufficiency and Infertility in Female Mice

Ras homolog gene family, member A (RhoA) is widely expressed throughout the female reproductive system. To assess its role in progesterone receptor-expressing cells, we generated RhoA conditional knockout mice RhoA(d/d) (RhoA(f/f)-Pgr-Cre(+/−)). RhoA(d/d) female mice had comparable mating activity, serum luteinizing hormone, prolactin, and estradiol levels and ovulation with control but were infertile with progesterone insufficiency, indicating impaired steroidogenesis in RhoA(d/d) corpus luteum (CL). RhoA was highly expressed in wild-type luteal cells and conditionally deleted in RhoA(d/d) CL. Gestation day 3.5 (D3.5) RhoA(d/d) ovaries had reduced numbers of CL, less defined corpus luteal cord formation, and disorganized CL collagen IV staining. RhoA(d/d) CL had lipid droplet and free cholesterol accumulation, indicating the availability of cholesterol for steroidogenesis, but disorganized β-actin and vimentin staining, indicating disrupted cytoskeleton integrity. Cytoskeleton is important for cytoplasmic cholesterol movement to mitochondria and for regulating mitochondria. Dramatically reduced expression of mitochondrial markers heat shock protein 60 (HSP60), voltage-dependent anion channel, and StAR was detected in RhoA(d/d) CL. StAR carries out the rate-limiting step of steroidogenesis. StAR messenger RNA expression was reduced in RU486-treated D3.5 wild-type CL and tended to be induced in progesterone-treated D3.5 RhoA(d/d) CL, with parallel changes of HSP60 expression. These data demonstrated the in vivo function of RhoA in CL luteal cell cytoskeleton integrity, cholesterol transport, StAR expression, and progesterone synthesis, and a positive feedback on StAR expression in CL by progesterone signaling. These findings provide insights into mechanisms of progesterone insufficiency.