It is now well established that fetal mammalian eggs originate from somatic stem cells. More recent research of adult human ovaries has shown that oocytes and granulosa cells (the layer of small cells that form the wall of the ovarian follicle) may originate from OSE cells and assemble together to form new primary follicles -- the structures that grow and rupture during ovulation to release mature eggs. However, definitive proof that new oocytes may develop in adult human females will be if they can be found to differentiate in vitro from OSE cells derived from adult human ovaries.
For the first time, Antonin Bukovsky and colleagues from the Department of Obstetrics and Gynecology of the University of Tennessee, United States, have shown that human eggs and granulosa cells) can develop from cultured OSE cells. By scraping cells from the surface of adult ovaries and growing them for 5 to 6 days in the presence of an estrogen-containing medium (phenol red) to stimulate their growth, the team was able to produce new human oocytes in vitro.
The oocytes cultured in this way are viable and went on to successfully complete the first meiotic division to become mature human eggs -- capable of being fertilized and developing into an embryo. These in vitro findings support earlier in vivo studies by Bukovsky and colleagues that OSE cells are bipotent; capable of differentiating alon