Proliferative response and macromolecular synthesis by ocular cells cultured on extracellular matrix materials

Abstract

To investigate the effects of extracellular matrix components on cellular function, we cultured several types of ocular cells on substrates composed of extracellular matrix materials that were layered on culture dishes either as dried films or as gels. We measured cellular proliferation on these substrates and on a series of gels composed of varying proportions of rat tail tendon type I collagen and Matrigel, a commercially available extract of a basement membrane-producing murine tumor. In addition, we studied the biosynthesis of collagens and of proteoglycans by these cultured cells using [3H]-L-proline and [35S]-sulfate. The proliferative abilities of the various types of ocular cells on the dried film substrates, on uncoated plastic culture vessels, and on pure type I collagen gel, were similar. However, proliferation of ocular cells cultured on gels composed of greater than or equal to 90% Matrigel was markedly reduced. There was little or no inhibition of growth of two types of non-ocular cells: rat C6 astrocytoma cells, and human dermal fibroblasts. Histologic studies showed that the ocular cells tested often formed long strands and capillary-like tubes, and tended to "burrow" beneath the surface of substrates containing high percentages of Matrigel. Fibroblasts infrequently formed tubes, and exhibited the burrowing property also on gels containing primarily type I collagen, while C6 cells showed neither of these behaviors on any of the matrices tested. The elution pattern of newly synthesized [3H]-labeled and [35S]-labeled macromolecules produced by all of the cultured cell types, and detected by Sepharose CL-4B chromatography in the medium and in the cell layer plus matrix fractions did not vary following culture on the different substrates. Approximately twofold more of the newly synthesized collagens and proteoglycans were deposited in the cell layer plus matrix, and proportionately less appeared in the medium, when cells were cultured on type I collagen gels and on Matrigel than on the dried film substrates. These experiments demonstrate the influence of the extracellular matrix on several aspects of cell behavior, and provide further evidence that modification of the composition of the extracellular matrix may be an important determinant of normal or pathological cell function.