Change in collagen synthesis of human chondrocyte culture. I. Development of a human model, demonstration of collagen type conversion by immunofluorescence.

A research system constituted entirely of components of human origin was developed to study conversion of collagen synthesis by human chondrocytes. Type specificity of affinity chromatography-purified antibodies to human type II or type I collagen was proven by ELISA inhibition and immunofluorescence analysis. Human chondrocytes were isolated from articular cartilage and kept in monolayer cultures for eight subpassages. Conversion of type II to type I synthesis by chondrocytes was investigated by immunofluorescence. Staining with anti-type II collagen antibodies could be detected during primary cultures and in the first subpassage, whereas staining with anti-type I collagen antibodies occurred beginning from the end of primary cultures and was present up to the eighth subpassage. Results are compared to observations obtained in animal systems and their relevance to conditions in osteoarthritis is discussed.