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

在鸡胚中，有一群软骨成纤维细胞，称为巩膜成纤维细胞。巩膜成纤维细胞在原代培养中分泌多种自分泌生长促进因子，巩膜自分泌因子（SAF），进入无蛋白培养基。一种这样的因子，SAF-IIa，其是热不稳定的并结合肝素，在小鼠成纤维细胞系BALB/c 3 T3 A31细胞上显示出强的DNA合成促进活性，并且具有约1000的分子量。16 kDa，通过凝胶过滤。这些数据表明，SAF-IIa与FGF家族的生长因子有关。然而，当对巩膜成纤维细胞和BALB/c 3 T3 A31细胞进行测定时，肝素增强对生长促进活性的影响表明SAF-Ⅱ a与aFGF或bFGF不同。另一种热不稳定的自分泌生长促进因子SAF-IIb与肝素结合较弱，对BALB/c 3 T3 A31细胞无生长促进活性。耐热生长因子（SAF-I）对BALB/c 3 T3细胞有促增殖作用，热处理可提高其活性。全胚胎成纤维细胞，在无蛋白培养基中显示低自分泌生长，主要产生SAF-IIa样生长促进活性，不产生SAF-I。这表明巩膜成纤维细胞在体外的强增殖活性可归因于在生长阶段产生强而稳定的自分泌因子，SAF-I，并且是巩膜软骨细胞的一种特殊性质。

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.