IGFBP5 regulates fibrocartilage differentiation and cartilage injury induced by T-2 toxin via blocking IGF-1/IGF-1R signalling.

Abstract

Kashin-Beck disease (KBD) is a form of osteoarthropathy that affects the skeletal and joint systems of children and adolescents. Insulin-like growth factor binding protein 5 (IGFBP5) plays an important role in bone growth and development. This study aimed to investigate the role of IGBFP5 in regulating the function and differentiation of chondrocytes in KBD. The mRNA and protein expressions of IGFBP5, IGF-1 and IGF-1R were detected by RT-qPCR and western blot assays. Commercial kits were performed to measure the mitochondrial ROS content, calcium loading and ATP synthesis in chondrocytes. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to detect the cell viability of chondrocytes. Co-IP and pull-down assays were conducted to verify the binding activity of IGFBP5 to IGF-1R. The rat KBD model was constructed by a low selenium diet and T-2 toxin. The expression of IGFBP5 was upregulated in KBD patient and rat tissues. Further studies showed that interfering with IGFBP5 effectively inhibited T-2-induced chondrocyte damage and mitochondrial stress. IGFBP5 depressed the interaction between IGF-1 and IGF-1R, thereby affecting the regulation of IGF-1/IGF-1R signalling in the repair of chondrocytes. In addition, the fibrous differentiation of cartilage progenitor cells (CPCs) and the activity and migration of CPCs induced by T-2 stimulation were suppressed under IGFBP5 silence treatment. IGFBP5 was upregulated during the pathological progression of KBD, and IGFBP5 competitively bound with IGF-1R to impede the interactions between IGF-1 and IGF-1R. Knockdown of IGFBP5 inhibited fibrotic differentiation and ameliorated the reduction of CPC function in KBD model.