Differentiation Of Human Amniotic Fluid Stem Cells Into Oocyte-Like Cells

Derivation of oocyte like cells from adult stem cells would benefit the study of oogenesis. It has been kwon that Human amniotic fluid stem cells (hAFS) are able to differentiate spontaneously in vitro into various somatic cell types. However, the germ cell potential of hAFS cells has never been tested. Here, we report that hAFS cells isolated from the 20 to 38 weeks'gestation have the intrinsic ability to differentiate into oocyte like cells based on several characters specially. The study also tested the hypothesis that a morphologically distinct population of cells derived from hAFS can differentiate further into more mature gametes.A XX hAFS cell line was isolated from human amniotic fluid of the 2nd trimester of gestation at the single-cell level by limiting dilution, and the specific cell surface antigens of the hAFS cells were characterized. In order to track and identify specific stages of female gamete induction, we construct a pBMP15-EGFP vector. When differentiation was induced in conditioned medium supplemented with porcine follicular fluid, we observed a subpopulation of morphologically round cells with zona pellucida-like morphology were observed which built large embryoid bodies in suspension culture. These 3D embryoid bodies were strongly alkaline phosphatase positive. During differentiation, these cells also express OCT4, Dazl, Stella, GDF9, CD117, SCP3, ZP1, ZP2 and ZP3, which are markers indicative of germ cell formation. When labeled with a pBMP15-EGFP reporter, these cells further differentiate into round GFP-positive oocyte-like cells. Some of these round cells spontaneously developed into parthenogenetic embryo-like structures, which were about 50 - 60μm in diameter.The potential of generate germ cell precursors from adult stem cells, especially hAFS cells, may provide an in vitro model to study some of the unanswered questions surrounding early germ cell formation.