Human endometrial tissues regenerate easily after menstruation and childbirth, suggesting the existence of endometrial stem-like cells that can survive and proliferate from a single cell over a long time. To clarify this hypothesis, limiting dilution cultures performed with eutopic endometrial, ovarian endometrioma and adenomyosis cells obtained from a patient, achieved cloning efficiencies of 13.0, 5.0, and 0.8%, respectively. These monoclonal cells survived for more than 24 months. More than 4 types of monoclonal cells were established from eutopic endometrial cells and microscopically were distinctly different from each other. Intraperitoneal injections of dispersed human eutopic endometrial cells did not cause any endometriosis-like lesions in scid mice, but those of endometrial tissue fragments did. IL-6, TNF-α, IL-1β, M-CSF and HGF failed to enhance transplantation of dispersed endometrial cells to the mice. These results indicate that several types of eutopic endometrial cells survive long-term, and that simple regurgitation of eutopic endometrial stem-like cells may not induce peritoneal endometriosis.

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