These studies are designed to examine morphological and biochemical properties of synthesis, secretion and extracellular deposition of chondroitin sulfate proteoglycan and other matrix molecules. Immunolocalization of two products simultaneously at the light and electron microscopic levels will be used to visualize coordinate biosynthesis and matrix deposition for specific gene products of individual cells while preserving cell-cell and cell-matrix relationships. Chondrocytes in culture will provide a well-controlled and readily manipulated living model system for the study of biosynthesis and interactions among matrix constituents, presumably more representative of in vivo conditions than reconstituted cell-free systems. Antibodies specific for cartilage matrix components (type II collagen, chondroitin sulfate proteoglycan and link chondronectin) and for matrix constituents characteristic of fibroblasts and precartilage mesenchyme (type I collagen and fibronectin) will be used. Monoclonal antibodies for CSPG will be particularly valuable for these studies. Another dimension to this investigation will be provided by complementary biochemical analyses. Experiments are designed to elucidate properties of co- and post-translational processing of chondroitin sulfate proteoglycan, and perhaps link protein and type II collagen. Results obtained from cell-free translation studies will be related to information about processing and biosynthetic intermediates obtained from pulse labeling of chondrocytes in culture. In order to evaluate further the biosynthesis of matrix molecules and their interrelationships, chondrocytes will be grown in culture in the presence of agents which 1) block cartilage differentiation or 2) alter the synthesis or processing of matrix constituents. The use of immunohistochemistry in conjunction with biochemical and molecular analyses should enhance greatly the total picture of biosynthesis and interactions of matrix components and thereby provide a better understanding of the formation and regulation of cartilage matrix and a firm basis for the examination of proteoglycans and their interactions with other matrix components in non-cartilage connective tissues.
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