IMMUNOLOCALIZATION OF PROGESTERONE-INDUCED UTERINE PROTEIN-1 IN HUMANENDOMETRIUM DURING THE MENSTRUAL-CYCLE AND IN THE PLACENTA THROUGHOUTGESTATION

OBJECTIVE: Progesterone-induced uterine protein-1, a product of secret ory endometrial stromal cells (relative molecular mass 70,000, isoelec tric point 5.7), was immunolocalized in endometrium and placenta. STUD Y DESIGN: Biopsies were performed to obtain human endometrium and plac enta throughout the menstrual cycle and gestation. Formalin-fixed, par affin-embedded tissues (n = 74) were sectioned and immunohistochemical ly stained for progesterone-induced uterine protein-1 by the avidin-bi otin peroxidase procedure. Isolated endometrial cells were also staine d for progesterone-induced uterine protein-1. RESULTS: Progesterone-in duced uterine protein-1 localized in proliferative endometrial stroma and in early to midsecretory stroma and ciliated epithelia and vanishe d from nonpregnant, late-secretory endometrium yet localized in the de cidua, syncytiotrophoblast, and intermediate cytotrophoblast during pr egnancy. Isolated, cultured endometrial stromal but not epithelial cel ls displayed progesterone-induced uterine protein-1 staining. CONCLUSI ON: Endometrial progesterone-induced uterine protein-1 localization sh ifts from stromal to epithelial, coinciding with the time of ovulation , fertilization, and implantation. This observation, combined with the disappearance of progesterone-induced uterine protein-1 in late-secre tory, nonpregnant endometrium and its presence in decidua and trophobl ast, suggests that progesterone-induced uterine protein-1 may play a r ole in decidualization, endometrial or embryo cross-talk, or placental physiologic features.