Endometrial adult/progenitor stem cells: pathogenetic theory and new antiangiogenic approach for endometriosis therapy.

The cyclical arrival of endometrial cells into the abdominal cavity through retrograde flux at menstruation represents the etiopathogenetic basis of endometriosis. The endometrium has peculiar regenerative properties linked to the presence of adult stem cells similar to mesenchymal stem cells (MSCs). Once in the abdominal cavity, these MSCs could proliferate, invade, and differentiate into endometrial cells, finally generating ectopic implants. As only differentiated endometrial cells, and not endometrial MSCs, possess steroid hormone receptors, MSCs could be responsible for the high rate of persistence/recurrence of the disease after hypoestrogenism-inducing therapies. Even angiogenesis promoted by MSCs could play an important role, as survival and proliferation of endometriotic tissue depend on the formation of new blood vessels. Inhibition of angiogenesis represents, in fact, a new, promising therapeutic approach for the disease. Further, medications directly targeting endometriosis MSCs could be effective, alone or in association with hormonal treatments, in increasing the success of medical treatment.