Modulation of the baboon (Papio anubis) uterine endometrium by chorionic gonadotrophin during the period of uterine receptivity

This study was undertaken to determine the modulation of uterine function b y chorionic gonadotrophin (CG) in a nonhuman primate, Infusion of recombina nt human CG (hCG) between days 6 and 10 post ovulation initiated the endore plication of the uterine surface epithelium to form distinct epithelial pla ques. These plaque cells stained in tensely for cytokeratin and the prolife rating cell nuclear antigen. The stromal fibroblasts below the epithelial p laques stained positively for alpha-smooth muscle actin (alpha SMA). Expres sion of alpha SMA is associated with the initiation of decidualization in t he baboon endometrium, Synthesis of the glandular secretory protein glycode lin, as assessed by Western blot analysis, was markedly up-regulated by hCG , and this increase was confirmed by immunocytochemistry, Northern blot ana lysis, and reverse transcriptase-PCR. To determine whether hCG directly mod ulated these uterine responses, we treated ovariectomized baboons sequentia lly with estradiol and progesterone to mimic the hormonal profile of the no rmal menstrual cycle. Infusion of hCG into the oviduct of steroid-hormone-t reated ovariectomized baboons induced the expression of aSMA in the stromal cells and glycodelin in the glandular epithelium, The epithelial plaque re action, however, was not readily evident, These studies demonstrate a physi ological effect of CG on the uterine endometrium in vivo and suggest that t he primate blastocyst signal, like the blastocyst signals of other species, modulates the uterine environment prior to implantation.