Stem/progenitor cells in the human endometrium

Adult stem cells, also termed tissue stem cells or somatic stem cells, are rare populations residing in almost all adult tissues. They can self-renew and possess the capacity for multi-lineage differentiation. They play critical roles in tissue homeostasis, regeneration, repair, and response to injury. It has long been believed that stem/progenitor cells exist in the human endometrium based on its unique capacity to regenerate and regress cyclically in response to fluctuating ovarian steroid hormones during each menstrual cycle throughout a reproductive life. There is increasing evidence that human endometrium contains small populations of epithelial progenitor cells (EPCs), mesenchymal stem cells (MSCs), and side population cells (SPCs) that are likely responsible for its monthly regeneration and tissue homeostasis. This review summarizes the identification of EPCs, MSCs, and SPCs and discusses how they are involved in the physiological remodeling and regeneration of the human endometrium.