Analysis of growth regulating factors produced by mesenchymal cells of the chick embryo in complete protein-free primary cultures.

点击翻译按钮获取中文摘要

In the chick embryo, there is a population of chondrogenic fibroblasts known as scleral fibroblasts. Scleral fibroblasts in primary culture secrete multiple autocrine growth-promoting factors, scleral autocrine factors (SAFs), into protein-free medium. One such factor, SAF-IIa, which is heat-labile and binds to heparin, shows strong DNA synthesis-promoting activity on the mouse fibroblast cell line, BALB/c 3T3 A31 cells and has a molecular weight of ca. 16kDa by gel filtration. These data suggest that SAF-IIa is related to growth factors of the FGF family. However, the effects of heparin augumentation on the growth-promoting activity suggest that SAF-IIa is not identical to aFGF or bFGF, when assayd on scleral fibroblasts and also on BALB/c 3T3 A31 cells. The other heat-labile autocrine growth-promoting factor, SAF-IIb, shows weak binding to heparin and no growth-promoting activity for BALB/c 3T3 A31 cells. The heatresistant growth factor, SAF-I, is effective in enhancing the proliferation of BALB/c 3T3 cells and its activity is increased by heat treatment. Whole-embryo fibroblasts, which show low autocrine growth in protein-free medium, produce mainly SAF-IIa-like growth-promoting activity and do not produce SAF-I.This indicates that the strong proliferative activity of scleral fibroblasts in vitro can be attributed to the production of a strong and stable autocrine factor, SAF-I, in the growing phase and is a specialized property of the chondrogenic cells of the sclera.