Expression of type VI collagen in normal and osteoarthritic human cartilage

Objective: This study was undertaken in order to study the expression of ty pe VI collagen in normal and osteoarthritic human knee cartilage. Methods: Seventy-two osteoarthritic cartilage/bone samples were obtained fo rm 29 patients with primary OA undergoing surgery for a total knee replacem ent. Normal cartilage was collected from five human knees at the time of au topsy. Type VI collagen protein was localized using a polyclonal anti human type VI collagen antibody, the corresponding mRNA was detected with an 310 base antisense probe, specific for the alpha 2(VI) collagen chain. Results: In normal cartilage, type VI collagen protein is concentrated peri cellularly around the chondrocytes of all cartilage zones. In the middle an d deep zones, type VI collagen was also found in the interterritorial matri x. Type VI collagen mRNA expression was detected in chondrocytes of all car tilage zones. In moderately affected osteoarthritic cartilage, type VI coll agen expression was increased. An intensive immunohistological interterrito rial staining for type VI collagen was observed in the middle and deep cart ilage zones. Specific mRNA signals were also increased especially in the mi ddle and deep cartilage zone. In the superficial zone and calcified cartila ge of these samples, type VI collagen mRNA expression was restricted to foc al areas. In severe osteoarthritic cartilage, an intensive staining for typ e VI collagen mRNA was found in clusters of proliferating chondrocytes and in the deep cartilage zone. Type VI collagen was localized pericellularly a nd in the matrix of chondrocyte clusters. Furthermore, chondrocytes from th e deep zone showed a territorial distribution of type VI collagen. Conclusions: These results demonstrate that in normal and osteoarthritic ca rtilage, type VI collagen is expressed in a zone specific pattern. The obse rved increase of type VI collagen expression in osteoarthritis suggests a p otential role in the disease process.