Enhanced expression of insulin-like growth factor-binding proteins in human osteoarthritic cartilage detected by immunohistochemistry and in situ hybridization

SummaryObjectiveTo determine the roles of insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) in the pathogenesis of osteoarthritis (OA).DesignCartilage tissues were obtained from the femoral heads of patients with OA, and those from patients with femoral neck fractures were used as a control. The expression of IGFBP-3, -4, and -5 was examined using immunohistochemistry and in situ hybridization, and IGF-I and IGF-I receptors were also immunohistochemically detected. The percentages of positive chondrocytes were determined by counting the total number of chondrocytes over the area of the surface, middle, and deep zones of the cartilage.ResultsThere was a marked increase in the percentage of positive chondrocytes in all IGFBPs on protein and messenger RNA levels for OA compared to that of the control cartilage. Furthermore, enhanced expression of IGFBPs and the IGF-I/IGF-I receptor was positively correlated with the histologic score for cartilage lesions.ConclusionUp-regulation of IGFBPs as well as IGF-I and its receptor was observed for OA cartilage tissue, suggesting the involvement of IGFBPs in the pathogenesis of OA