Placental protein 14 in endometrium during menstrual cycle and effect of early luteal phase mifepristone administration on its expression in implantation stage endometrium in the rhesus monkey

Placental protein 14 (PP14) is a glycoprotein which is secreted bysecretory phase endometrium and decidua in women. Despite the suggestionthat PP14 is involved in the process of endometrial maturation forblastocyst implantation, our understanding in this regard is poor. In thepresent study, the concentrations and distribution patterns ofimmunodetectable PP14 in the endometrium during proliferative and secretoryphases of normal ovulatory menstrual cycles, as well as in implantationstage endometrium in naturally mated ovulatory cycles with or without earlyluteal phase mifepristone treatment, were investigated using the rhesusmonkey as a primate model. Immunopositive PP14 was observed mainly inepithelial cells of glands and it was detected in one major immunopositiveband at Mr 28 kDa in tissue homogenate and spent medium. The area ofimmunopositive precipitation of PP14 in glands was minimal in follicularphase endometrium, and was higher (P < 0.01) in early, mid- and lateluteal phase endometrium compared with that in pre- and periovulatoryphases of the cycle, but there was no change in its area profile in theglandular compartment throughout the luteal phase. Immunopositivity forPP14 in luminal contents of gland displayed an increasing profile fromearly to late secretory phases. Thus, the concentrations and thedistribution of immunodetectable PP14 in luteal phase endometrium of therhesus monkey showed marked similarity with those of human endometriumduring the natural menstrual cycle. Although there was no marked change inthe band characterstics for the protein in implantation stage endometriumfollowing early luteal phase mifepristone treatment, it was markedlydecreased (P < 0.01) in tissue homogenate and in vitro spent mediumalong with a lesser (P < 0.02) degree of immunoprecipitation in theglands in implantation stage samples of mifepristone treatment groupcompared with that in control group samples. Thus, the contragestionaleffect of early luteal phase mifepristone treatment appears to beassociated with a decrease in the concentration of immunodetectable PP14 inimplantation stage endometrial glands and its secretion in the rhesusmonkey. It remains to be seen whether this decline is caused from directantiprogesterone action on endometrial glands during progesteronedominance, or secondarily from associated retarded development ofendometrium.