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 placenta.

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 progesterone-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 ciliated 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.