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 (8–20 cells/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, Table 1) indicating greater self renewal capacity. Similarly, stromal HPP-CFU demonstrated greater self renewal activity compared with stromal LPP-CFU (P < 0.005, Table 1). Serially passaged epithelial HPP-CFU underwent significantly more population doublings (PD) before senescence than epithelial LPP-CFU (P < 0.05, Table 1). Likewise, stromal HPP-CFU underwent a higher number of PD compared with stromal LPP-CFU (P < 0.005, Table 1). 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.