Stem cells in the reproductive system.

This review article summarizes current knowledge on regulation, functions, and capacities of stem cells in the female and male reproductive tract. Major locations in which pluripotent cells reside and from where they can be isolated are the ovaries, the endometrium, the decidua, and the testis. They include oocytes, embryonic stem cells, trophoblast stem cells, and spermatogonial stem cells, but also several side populations, which can be obtained after certain isolation and culture procedures. The potential of pluripotent cells in the reproductive tract to differentiate is manifold, but heterogenous, depending upon their respective origin. As stem cells have a potential for future application in transplantation and regenerative medicine, this article also reviews the literature on major histocompatibility complex expression on stem cells of the reproductive tract, because of its immunogenic effects, but also because of its potential expression of HLA-G, a potent immunomodulator mainly associated with trophoblast cells.