INFLUENCE OF EXTRACELLULAR-MATRIX ON THE LIPOGENESIS OF CULTURED WHITE FAT-CELLS

Collagenase digests from subcutaneous fat tissue of new born rats were cultured on different types of collagen gel containing 50% type I col lagen, on fibronectin (Fn) or on laminin (Lm). On day 6, 17% of cells on a plastic substratum differentiated and had multilocular or unilocu lar cytoplasmic lipid droplets (CLDs). Cells on each type of collagen and on Lm had more CLDs than those on a plastic substratum. The extent of lipogenesis showed the following decreasing order: cells on Lm (80 %), on type IV+I collagen (70%), on type I collagen (52%), on type III +I collagen (36%), on type II+I collagen (32%). On day 14, most cells on Lm became unilocular fat cells. Cells on Fn showed delipidation and showed decreased reactivity to insulin stimulation. Immunohistochemic ally differentiated fat cells were positively stained with antilaminin or anti-type IV collagen antibodies. These results provide evidence t hat Lm and type IV collagen promote fat cell differentiation, whereas Fn facilitates dedifferentiation into the fibroblast-like fat cell.