GENE-EXPRESSION OF COLLAGEN-TYPE-IIA AND COLLAGEN-TYPE-IX CORRELATES WITH ULTRASTRUCTURAL EVENTS IN EARLY OSTEOARTHROSIS - NEW APPLICATIONSOF THE RABBIT MENISCECTOMY MODEL

Objective. To examine the phenotypic expression and geographic distrib ution of collagens in early stages of osteoarthrosis and their relatio nship to ultrastructural events in cartilage. Methods, In situ hybridi zation 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 m odel of osteoarthrosis. The expression of the developmental marker col lagen IIA was analyzed at the same time points. Articular cartilage st ructure was examined by scanning electron microscopy, Results, Little difference was found in total type II or type IX collagen gene express ion 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, t his activity was correlated with site-specific alterations in chondroc yte morphology, qualitative changes in the collagen matrix, and articu lar surface delamination on microscopy, Conclusion, Gene expression fo r collagen types IIA and IX is site-specific and correlates with ultra structural changes in cartilage in this model of early osteoarthrosis. We present the first known report of the distribution of type IX coll agen gene expression in any model of osteoarthrosis. These findings su pport the central importance of matrix interactions in osteoarthrosis and suggest that early phases of repair involve re-expression of a dev elopmental sequence by chondrocytes.