REMODELING OF COLLAGEN: AN IN VITRO MODEL OF CONNECTIVE TISSUE

Abstract

An in vitro model of connective tissue was reconstituted by introducing fibroblasts into a three-dimensional space of the hydrated collagen lattice. The model was maintained in culture to investigate morphological and biochemical changes in collagen fibrils. Evidence was obtained that the collagen fibrils in the model were stabilized on one hand and were metabolized on the other hand. Collagen fibrils were contracted and were reorganized by the cells in an early stage of culture. Collagen fibrils in the freshly prepared model were easily hydrolyzed by bacterial collagenase. The fibrils became resistant to the enzyme digestion during culture. The acquired resistance seemed to be partly due to the formation of a complex of collagen with polysaccharides secreted by the cells. The amount ofcollagen in the model decreased gradually during culture and a hydroxyproline-containing substance or substances accumulated in the medium, indicating that fibroblasts catabolized the collagen fibrils. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis demonstrated that the collagen was degraded to a peptide or peptides with molecular weights less than 20 K. The electron microscopical examinations of the model revealed some bizzare bodies with a striated banding pattern, which resembled the zebra-bodies reported in vivo. The origin of this striated structure is discussed.