Severe disturbance of the distribution and expression of type VI collagen chains in osteoarthritic articular cartilage.

Objective: The aim of this study was to evaluate the messenger RNA (mRNA) expression and distribution of the major pericellular type VI collagen in normal and osteoarthritic (OA) cartilage.

Methods: Conventional and confocal laser scanning immunohistochemistry, as well as in situ hybridization experiments, were performed for all 3 collagen type VI chains in sections of normal and OA articular cartilage.

Results: Normal adult articular chondrocytes were surrounded by a type VI collagen-positive pericellular matrix and showed significant levels of mRNA expression for all 3 type VI collagen chains. In OA cartilage, the expression and overall distribution of type VI collagen was largely increased in the lower middle and upper deep zones. In contrast, the upper zones showed a significant loss of pericellular type VI collagen staining.

Conclusions: Our results suggest that there is a significant basic turnover of type VI collagen in normal articular cartilage. In OA cartilage, the chondrocytes of the lower middle and upper deep zones account for a net increase in type VI collagen synthesis. The loss of type VI collagen staining in the upper zones is most likely the result of increased protein degradation rather than reduced synthetic activity.