mRNA-Expression of ER alpha, ER beta, and PR in Clonal Stem Cell Cultures Obtained from Human Endometrial Biopsies

Schuring AN, Braun J, Wullner S, Kiesel L, Gotte M

Abstract

Background. Proliferation and differentiation of the endometrium are regulated by estrogen and progesterone. The enormous regenerative capacity of the endometrium is thought to be based on the activity of adult stem cells. However, information on endocrine regulatory mechanisms in human endometrial stem cells is scarce. In the present study, we investigated the expression of ER alpha, ER beta, and PR in clonal cultures of human endometrial stem cells derived from transcervical biopsies. Methods. Endometrial tissue of 11 patients was obtained by transcervical biopsy. Stromal cell suspensions were plated at clonal density and incubated for 15 days. Expression of ER alpha, ER beta and PR was determined by qPCR prior to and after one cloning round, and normalized to 18S rRNA expression. Results. Expression of ER alpha and ER beta was downregulated by 64% and 89%, respectively (P = 0.002 and P < 0.001). In contrast, PR was not significantly downregulated, due to a more heterogenous expression pattern. Conclusions. Culture of human endometrial stroma cells results in a downregulation of ER alpha and ER beta, while expression of PR remained unchanged in our patient collective. These results support the hypothesis that stem cells may not be subject to direct stimulation by sex steroids, but rather by paracrine mechanisms within the stem cell niche.