Effects of steroid ablation and progestin replacement on the transcriptome of the primate corpus luteum during simulated early pregnancy.

The LH-like molecule chorionic gonadotropin (CG) is secreted by the macaque conceptus during and following implantation, rescuing the CL from impending regression and extending its functional lifespan in early pregnancy for approximately two weeks. CG binds to the same receptor as LH; i.e., LHCGR, and promotes production of steroids and other factors such as relaxin (RLN1). Our research group recently used Affymetrix rhesus macaque total genome arrays to compare the effects of CG on the luteal transcriptome from rhesus females during simulated early pregnancy (SEP) with changes during luteal regression in the non-fecund menstrual cycle. This analysis demonstrated that CG-rescue affected expression levels of 4,500 mRNA transcripts between days 10 and 15 of the luteal phase. Previous analyses indicated that a portion of the transcriptome in the macaque CL of the menstrual cycle was regulated indirectly by LH via the local actions of steroid hormones, including progesterone (P). Therefore, this study was designed to distinguish CG-regulated luteal genes that are dependent versus independent of local steroid (P) action. A protocol of increasing dosages of hCG (SEP) was begun on day 9 of the luteal phase in rhesus females combined with concurrent administration of the 3BHSD inhibitor trilostane (TRL) +/- the synthetic progestin (P) R5020. CL were collected on day 10 (no treatment) of the luteal phase to serve as a baseline comparison (n=8), 1 day of SEP (Day 10+hCG+/-TRL+/-R5020) and 6 days of SEP (Day 15+hCG+/-TRL+/-R5020); n=4/group. In the presence of CG, treatment with TRL reduced serum P levels to less than 1 ng/ ml after 1 day and all of the Day 15+h+TRL-treated females initiated menses before CL collection. The isolated CL were processed for total RNA and hybridized to microarrays. Compared to hCG treatment alone, 50 significantly altered mRNA transcripts were identified on day 10, rising to 95 on day 15 (P<0.05, 2-fold change in gene expression). The mRNA levels for several genes were validated in CL by real-time PCR. RNL1 levels increased with CG-treatment, but were not affected by steroid ablation, similar to previously reported relaxin protein expression. Steroid-sensitive genes included CDH11, IL1RN, INSL3, LDLR, OPA1, SERPINE1, SFRP4, and TNSF13B1; however differential sensitivity was observed and effects of steroid ablation and P replacement varied by day. Expression of some genes (e.g., 3BHSD2, ADAMTS1, ADAMTS5, MMP9, STAR, and VEGFA) previously identified as steroid regulated in the macaque CL during the menstrual cycle were not significantly altered by steroid ablation and P replacement during CG exposure in SEP. These data indicate that the majority of CG-regulated luteal transcripts are differentially expressed independently of local steroid actions. The proportion of steroid sensitive mRNA transcripts in the presence of CG is much smaller than in the presence of LH during the non-fecund cycle. Nevertheless, the steroid-regulated genes in the macaque CL may be essential during early pregnancy, based on the previous report that TRL treatment initiates premature structural regression of the CL during SEP. These data reinforce the concept that the structure, function, and regulation of the rescued CL in early pregnancy is different from the CL of the menstrual cycle.

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Bishop CV, Aazzerah RA, Quennoz LM, Hennebold JD, Stouffer RL