Oocyte formation by oogonial stem cells purified from ovaries of women of child-bearing age

This study describes an isolation protocol of rare mitotically active cells [oogonial stem cells (OSCs)], that have a gene expression profile consistent with primitive germ cells, from adult mouse ovaries and human ovarian cortical tissue. These cells can be expanded and can spontaneously generate 35- to 50-mm oocytes, as determined by morphology, gene expression and haploid (1n) status. Injection of the human OSCs, engineered to stably express GFP, into human ovarian cortical biopsies led to formation of follicles containing GFP-positive oocytes 1–2 weeks after xenotransplantation into immunodeficient female mice. Thus, ovaries of women of child-bearing age, possess, as do adult mice, rare mitotically active germ cells that can generate oocytes both in vitro and in vivo.