ACTIVATION OF FIBRILLAR COLLAGEN-SYNTHESIS AND PHENOTYPIC MODULATION OF CHONDROCYTES IN EARLY HUMAN OSTEOARTHRITIC CARTILAGE LESIONS

The objective of this study was to investigate the expression and extr acellular distribution of fibrillar collagen types I, II, and III in e arly stage osteoarthritic cartilage in order to elucidate matrix gene expression and cell differentiation in early phases of the disease. Ar throscopically, derived specimens of early stage osteoarthritic articu lar cartilage were analyzed by histochemistry, immunohistochemistry an d by in situ hybridization and compared with normal articular cartilag e samples. In normal articular cartilage no significant mRNA expressio n of any of the investigated collagen types was found. In early stage osteoarthritic specimens, a strongly enhanced mRNA expression of the m ajor cartilage matrix component type II collagen was detected. Additio nally, a focal onset of type III, but not type I collagen expression w as observed. Thus, besides activation of matrix synthesis, the modulat ion of the chondrocytic phenotype is likely to play a distinct role in the cellular response in the early phases of the degenerative process in osteoarthritis.