To examine the phenotypic expression and geographic distribution of collagens in early stages of osteoarthrosis and their relationship to ultrastructural events in cartilage.
In situ hybridization was used to localize articular expression of total type II (A+B) and type IX collagen at 2 and 4 weeks in the rabbit meniscectomy model of osteoarthrosis. The expression of the developmental marker collagen IIA was analyzed at the same time points. Articular cartilage structure was examined by scanning electron microscopy.
Little difference was found in total type II or type IX collagen gene expression for operated versus control limbs at 2 weeks. Gene expression for collagen types IIA and IX was found to be site-specific by the 4 week period and was largely limited to the meniscectomy site. At 4 weeks, this activity was correlated with site-specific alterations in chondrocyte morphology, qualitative changes in the collagen matrix, and articular surface delamination on microscopy.
Gene expression for collagen types IIA and IX is site-specific and correlates with ultrastructural changes in cartilage in this model of early osteoarthrosis. We present the first known report of the distribution of type IX collagen gene expression in any model of osteoarthrosis. These findings support the central importance of matrix interactions in osteoarthrosis and suggest that early phases of repair involve re-expression of a developmental sequence by chondrocytes.