GENE-EXPRESSION OF TYPE-II COLLAGENS IN CHONDRO-OSTEOPHYTES IN EXPERIMENTAL OSTEOARTHRITIS

The formation of chondro-osteophytes in osteoarthritic joints is a uni que example of adult neochondrogenesis that bears some similarities to growth plate elongation and fracture callus formation. This study use s in situ hybridization histochemistry to define the molecular phenoty pe of cells in active chondro-osteophytes. Chondro-osteophytes are com posed of fibrocytes and osteoblasts that express type I procollagen mR NA, mesenchymal prechondrochytes that express type IIA procollagen mRN A, and maturing chondrocytes that express type IIB procollagen mRNA. B ased on the spatial pattern of gene expression and cytomorphology, the neochondrogenesis associated with chondro-osteophyte formation closel y resembles that of healing fracture callus.