Soluble factors and the emergence of chick primordial germ cells in vitro.

Previous observations obtained from a culture of blastodermal cells on a mouse fibroblast feeder layer (STO) suggested that STO cells provide a factor or factors that facilitate development of avian primordial germ cells (PGC) from dispersed embryo cells. The purpose of the current study was to test the hypothesis that soluble factors produced by STO cells are responsible, at least in part, in supporting the development of PGC in culture and to examine the effect of stem cell factor (SCF), ciliary neurotrophic factor (CNTF), and basic fibroblast growth factor (bFGF) in the development of PGC in culture. Blastodermal cells on gelatin-coated plastic or on feeder layers of CV-1 cells yielded a small number of PGC. When blastodermal cells were cultured on STO cells, a marked increase in PGC was observed. The addition of STO cell-conditioned medium (STO-CM) to blastodermal cells cultured on gelatin-coated plastic and on feeder layers of CV-1 cells resulted in a significant increase in the number of PGC, indicating that soluble factors produced by STO cells can enhance the development of chicken PGC in culture. Supplementation of blastodermal cells with SCF (100 ng/mL) or CNTF (2 ng/mL) or with CNTF and SCF together resulted in a significant increase in the number of PGC after 48 h of culture on feeder layers of CV-1 cells. However, addition of bFGF (100 ng/mL) did not increase PGC. We concluded from these observations that the culture of blastodermal cells on feeder layers of STO and CV-1 cells can be used as a useful biological system in examining the regulatory factors that govern the ontogeny of the germ cell lineage in the avian embryo.