Immunolocalization of progesterone-induced uterine protein-1 in human endometrium during the menstrual cycle and in the placenta throughout gestation,

OBJECTIVE: Progesterone-induced uterine protein-1, a product of secretory endometrial stromal cells (relative molecular mass 70,000, isoelectric point 5.7), was immunolocalized in endometrium and placental. STUDY DESIGN: Biopsies were performed to obtain human endometrium and placenta throughout the menstrual cycle and gestation. Formalin-fixed, paraffin-embedded tissues (n = 74) were sectioned and immunohistochemically stained for proesterone-induced uterine protein-1 by the avidin-biotin peroxidase procedure. Isolated endometrial cells were also stained for progesterone-induced uterine protein-1. RESULTS: Progesterone-induced uterine protein-1 localized in proliferative endometrial stroma and in early to midsecretory stroma and cillated epithelia and vanished from nonpregnant, late-secretory endometrium yet localized in the decidua, syncytiotrophoblast, and intermediate cytotrophoblast during pregnancy. Isolated, cultured endometrial stromal but not epithelial cells displayed progesterone-induced uterine protein-1 staining. CONCLUSION: Endometrial progesterone-induced uterine protein-1 localization shifts 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-secretory, nonpregnant endometrium and its presence in decidua and trophoblast, suggests that progesterone-induced uterine protein-1 may play a role in decidualization, endometrial or embryo cross-talk, or placental physiologic features.