Stem/progenitor cells and the regeneration potentials in the human uterus

The human uterus is unique in that it possesses the tremendous regenerative capacity required for cyclical regeneration and remodeling throughout a woman's reproductive life. Not only must the uterus rapidly enlarge to accommodate the developing fetus, the endometrium must also regenerate with each menstrual cycle. This plasticity of the reproductive system has recently been highlighted. My research group and collaborators showed that functional endometrial tissue could be regenerated from only a small number of singly dispersed human endometrial cells, transplanted beneath the kidney capsule of severely immunodeficient mice. This artificially generated endometrium resembles the natural endometrium, and contains human blood vessels that invade the mouse kidney parenchyma. Additionally, it mimics normal hormone-dependent changes including proliferation, differentiation, and tissue breakdown (menstruation). The regenerative capacity of endometrial cells makes them ideal candidates for tissue reconstitution, angiogenesis, and human-mouse chimeric vessel formation. The smooth muscle cells of the uterus (myometrium) share the plasticity of the endometrium. This is evidenced by their capacity for dramatic, repeatable, pregnancy-induced enlargement. Regeneration and remodeling in the female reproductive tract allude to the existence of endometrial and myometrial stem cell systems. We have recently isolated candidate populations of adult stem cells from both the human endometrium and myometrium. Characterization of these endometrial and myometrial cells, along with the study of the mechanisms controlling their regeneration, will improve the understanding of the physiology and pathophysiology of the female reproductive tract. Furthermore, myometrial and endometrial stem-like cells might also represent a novel source of biological material that could be used for the reconstruction of not only the human uterus but other organs as well.