The mechanism study of THBS3 in regulating cartilage vascularization/bone coupling via the TGF-β/Smad2/3 pathway in osteoarthritis

Objective Vascularization and osteogenesis coupling is observed in osteoarthritis (OA) cartilage. THBS-3 belongs to the extracellular matrix (ECM) proteins and is highly expressed in cartilage tissue. The effect of THBS-3 on OA is unclear. This study aims to explore the mechanistic role of THBS-3 in OA. Design: Expressions of THBS-3 was detected by Western blot (WB) and RT-qPCR. WB was employed to measure the expression levels of synthesis and degradation metabolism, as well as vascularization/ossification coupling. Migration and tube formation experiments were conducted to assess the migratory and tube-forming abilities of HUVECs influenced by THBS-3. Micro-CT was utilized for 3D imaging in mice. Immunohistochemistry was employed to detect the expression of synthesis, degradation metabolism, and vascularization/ossification coupling-related markers. Additionally, WB was utilized to assess the transforming growth factor-beta (TGF-β) signaling pathway. Results Proteinomics sequencing has revealed a higher expression level of THBS-3 in OA cartilage. Chondrocytes from OA joints exhibited significantly higher expression of THBS-3 relative to healthy individuals. In experiments conducted both in vivo and in vitro, THBS-3 exhibited a dual impact by enhancing catabolic metabolism, suppressing synthetic metabolism, and fostering the coupling of vascularization and osteogenesis within the cartilage. THBS-3 activated the TGF-β signaling pathway, and blockade of the TGF-β signaling pathway resulted in increased p-Smad2/3 expression in OA cartilage cells and decreased expression of vascularization /ossification coupling. Conclusion THBS-3 can promote the vascularization/ossification coupling of cartilage cells by activating the TGF-β/Smad2/3 signaling pathway, providing new insights and targets for the treatment of OA.