236. Characterising the stem cell activity of human endometrial epithelial and stromal cells

Abstract

The human endometrium has remarkable regenerative capacity. It contains rare clonogenic epithelial and stromal cells.1 The aims of this study were to compare the stem cell properties, self renewal, differentiation and proliferative potential, of endometrial cells initiating large clones (HPP-CFU, high proliferative potential–colony forming units) with those initiating small clones (LPP-CFU, low PP-CFU). Endometrial tissue obtained from 12 ovulating women undergoing hysterectomy was dissociated into single cell suspensions and epithelial and stromal cells were cultured at clonal density (8–20cells/cm2). Individual clones were harvested and serially recloned to measure self-renewal, serially passaged to assess proliferative potential and cultured in various media to assess differentiation. Secondary stromal clones were characterized for mesenchymal stem cell (MSC) markers by flow cytometry. Epithelial HPP-CFU serially cloned significantly more times than epithelial LPP-CFU (P<0.005, Table1) indicating greater self renewal capacity. Similarly, stromal HPP-CFU demonstrated greater self renewal activity compared with stromal LPP-CFU (P<0.005, Table1). Serially passaged epithelial HPP-CFU underwent significantly more population doublings (PD) before senescence than epithelial LPP-CFU (P<0.05, Table1). Likewise, stromal HPP-CFU underwent a higher number of PD compared with stromal LPP-CFU (P<0.005, Table1). Stromal HPP-CFU expressed CD29, CD44, CD73, CD90, CD105 and CD146, and were negative for haemopoietic and endothelial markers, CD45, CD34 and CD31. Stromal HPP-CFU differentiated into adipocytes, smooth muscle cells, osteoblasts and chondrocytes when cultured in appropriate differentiation media. Our studies of human endometrial cells demonstrate that the rare epithelial and stromal HPP-CFU exhibit self-renewal and high proliferative potential. Furthermore stromal HPP-CFU express markers typical of bone marrow MSC and differentiate into four mesenchymal lineages. These data suggest that epithelial and stromal HPP-CFU, but not LPP-CFU, have characteristic properties of adult epithelial stem cells and MSC respectively and are likely responsible for the remarkable cyclical, regenerative capacity of human endometrium.