Behavior of rat mesangial cells cultured within extracellular matrix

Rat mesangial cells were cultured within hydrated laminin-rich gels prepared from the Engelbreth-Holm-Swarm mouse tumor (E gel) or within type I collagen gels (C gel) to examine the effects of extracellular matrix on cell morphology, growth and proteoglycan (PG) synthesis. Rat dermal fibroblasts were also cultured under the same conditions for comparison with mesangial cells. Mesangial cells extended an array of cell processes, developing an arborized shape within E gel, whereas they were elongate and bipolar within C gel. Conversely, fibroblasts adopted a bipolar elongate morphology in both E gel and C gel. The growth rate of cultured cells was determined by autoradiography using [3H]thymidine. The growth rate of 3H-labeled mesangial cells was higher than or about the same as that of labeled fibroblasts both on glass and within C gel, whereas within E gel the growth rate of mesangial cells was significantly lower than that of fibroblasts. In both mesangial cells and fibroblasts, there was no significant difference in the amounts of [35S]sulfate incorporated into macromolecules between cultures within E gel and C gel. However, gel chromatography on Sepharose CL-6B showed changes in the hydrodynamic size of newly synthesized PGs and glycosaminoglycan chains. The 35S-labeled PGs and glycosaminoglycan chains synthesized by mesangial cells cultured within E gel were smaller than those of cells cultured within C gel. In contrast, the PGs and glycosaminoglycan chains synthesized by fibroblasts within E gel were larger than those synthesized within C gel. These findings indicate that the extracellular matrix is important in regulating the morphology, growth, and PG synthesis of mesangial cells.