The preliminary characterization of mitogens secreted by embryonic chick wing bud tissues in vitro.

Embryonic chick wing bud tissues secrete diffusible mitogens when cultured in vitro (Bell & McLachlan, 1985). These molecules may play an important role in limb development since media conditioned by morphogenetically active regions of the wing bud possess greater mitogenic activity than media conditioned by non-morphogenetic regions. These studies show that while the chick-derived growth factors were mitogenic for mouse-derived NIH 3T3, 10T1/2 and NR6 cells and chick limb bud cells, they did not stimulate DNA synthesis in 3B11, PC13 END, normal rat kidney or bovine endothelial cells. Furthermore, the effects of chick-derived mitogens were synergistically enhanced by insulin and PGF 2 alpha but remained unaffected by ECDGF, EGF, FGF and MSA. These findings indicate that embryonic chick limb bud cells synthesize and secrete growth factors which resemble in function other well-characterized growth factors and in particular PDGF.