Increased content of type-VI collagen epitopes in human ostearthritic cartilage: Quantitation by inhibition ELISA

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Abstract
Type‐VI collagen is an integral part of the extracellular cartilage matrix. However, the exact amounts of type‐VI collagen in normal and osteoarthritic human cartilage still are not known. In this study, we describe an inhibition enzyme‐linked immunosorbent assay that was developed to quantitate type‐VI collagen epitopes found in guanidinium chloride extracts from normal and osteoarthritic human cartilage. In 31 cartilage samples from various localizations of healthy adult human knees, type‐VI collagen epitopes accounted for approximately 0.40% of the total collagen content. Interestingly, type‐VI collagen epitopes increased about 4‐fold in osteoarthritic cartilage. A statistically significant increase of type‐VI collagen epitopes was found during early stages of the disease, with only a superficial roughening of the cartilage surface and a loss of proteoglycans. Thus, these findings indicate that type‐VI collagen is a minor component of normal human articular cartilage and that the amount of type‐VI collagen epitopes increases significantly during early stages of osteoarthritis.