Posts Tagged ‘Oogonia’

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

Germline stem cells that produce oocytes in vitro and fertilization-competent eggs in vivo have been identified in and isolated from adult mouse ovaries. A fluorescence-activated cell sorting-based protocol has been standardized that can be used with adult mouse ovaries and human ovarian cortical tissue to purify rare mitotically active cells that have a gene expression profile that is consistent with primitive germ cells. Once established in vitro, these cells can be expanded for months and can spontaneously generate 35- to 50-μm oocytes, as determined by morphology, gene expression and haploid (1n) status. Injection of the human germline cells, engineered to stably express GFP, into human ovarian cortical biopsies leads to formation of follicles containing GFP-positive oocytes 1–2 weeks after xenotransplantation into immunodeficient female mice. Therefore, based on the multiple experimental lines of evidence reported it is reasonable to conclude that the rare cells with cell-surface expression of DDX4 that are present in the ovaries of reproductive-age women represent adult human OSCs. In addition to opening a new research field in human reproductive biology that was inconceivable less than 10 years ago, clear evidence for the existence of these cells in women may offer new opportunities to expand on and enhance current fertility-preservation strategies. For example, with assisted reproductive technologies involving cryopreservation of ovarian cortical tissue already in development for females with cancer, isolation and expansion of OSCs from this tissue before or after cryopreservation might be useful for new fertility applications. In fact, it has been found that these cells can be consistently obtained from cryopreserved and thawed human ovarian tissue samples, and that these cells per se can be cryopreserved and thawed months later with minimal loss for successful establishment in vitro. In addition, the availability of a detailed protocol for the purification of these newly discovered cells from human ovary tissue provides a much more physiologically relevant in-vitro model system from which to study human female germ cell development compared to the ESC-derived or induced pluripotent stem cell-derived germline cells that are currently used as models for human female gametogenesis.

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