The aim of the proposed research is to advance our understanding of the way in which tissues, namely tendons, repair. We will use a biochemical approach to establish which particular molecular types of collagen are synthesized by the tendon cells during the repair process. The involvement of more than one type of collagen in the repair process was suggested by our ultrastructural studies which demonstrated the presence of small 400 A fibrils during the early stages of tendon repair. These small-diameter fibrils are indicative of type III collagen, a type normally present in embryonic tissues and not in adult tendon. To assess the capability of the tendon cells to synthesize type I and type III collagen, we will separate the two cell populations, the inner fascicle tendon cells and the outer synovial cells, and grow each in tissue culture. The types of collagen synthesized by each cell population will be determined by use of carboxymethyl- and diethylaminoethyl-cellulose chromatography and by sodium dodecyl sulfate-acrylamide gel electrophoresis. The type of collagen in each fraction will be verified by cyanogen bromide cleavage followed by analysis of the electrophoretically separated cyanogen bromide peptides. Monoclonal antibodies to type I and type III collagen will be prepared using mouse hybrid cells, and then used for immunofluorescence studies that detect and localize type I and type III collagen in situ. Tendon tissue at various stages of repair and normal developing chick tendon will be examined after indirect immunofluorescence staining.