Endometrial stem/progenitor cells and proliferative disorders of the endometrium.

The human endometrium undergoes cyclical processes of regeneration, differentiation and shedding as part of the menstrual cycle. In non-menstruating species, there are cycles of endometrial growth and apoptosis rather than physical shedding. It was hypothesized many years ago that endometrial stem cells are responsible for the remarkable regenerative capacity of endometrium. In this review, we summarize the first data providing evidence for the presence of adult stem/progenitor cells in human and mouse endometrium using functional assays. This is because adult stem cells are defined by their functional properties rather than by marker expression, and there are no known markers of endometrial stem/progenitor cells. Evidence will be presented which demonstrates that the endometrium contains rare populations of both and epithelial and stromal stem/progenitor cells. These fundamental studies on endometrial stem/progenitor cells will provide new insights into the pathophysiology of various gynecological disorders associated with abnormal endometrial proliferation, including endometriosis, endometrial cancer, endometrial hyperplasia, and adenomyosis. The possible use of endometrial stem/progenitor cells in tissue engineering applications relevant to urogynecology will also be mentioned.