Immunochemical Studies of Type II Collagen Degradation in Bovine and Human Articular Cartilage

Note:A major limitation in analyzing collagen degradation in articular cartilage in arthritis has been the lack of a technique for identifying collagen breakdown in situ. A new methodology is described which utilizes immunochemical and immunohistochemical protocols and a well characterized antiserum that permits the detection and analysis of type II collagen degradation in human and bovine articular cartilages. The antiserum R181 specifically reacts with unwound alpha chains and the CNBr-derived peptides a 1 (II)CB 11 and a l(II)CB8 of human and bovine type II collagens and not with helical collagens. Increased degradation of type n collagen was detected in bovine cartilage cultured with IL-l. Increased extractable a chains and smaller collagen fragments were detected immunochemically. Immunohistochemically, an increase in type II collagen degradation was detected in human cartilages cultured with interleukin-1. This could be inhibited by addition of a metalloproteinase inhibitor. All human arthritic cartilages showed more staining for type II collagen degradation than was seen in normal cartilages. Using light and electron microscopic analyses, distinct patterns of collagen degradation were seen in rheumatoid arthritic compared with osteoarthritic cartilages. The results suggest that type 11 collagen degradation is a significant and early event in cartilage pathology