Connexin 43 affects thoracic ossification of ligamentum flavum by regulating the p38 MAPK-RUNX2 signaling pathway

This study aimed to investigate the role of connexin 43 (CX43) in thoracic ossification of ligamentum flavum (TOLF) based on the p38 mitogen-activated protein kinase (p38MAPK)-runt-related transcription factor 2 (RUNX2) pathway. Immunohistochemistry was used to detect CX43 expression in TOLF and non-TOLF patients, fibroblasts of TOLF were isolated and induced osteogenic differentiation, and CX43 expression was detected by western blot analysis (WB). In addition, si-CX43 was used to intervene CX43, and SB203580 was used to inhibit the p38MAPK. The expressions of bone differentiation marker protein were detected by WB, and the ossification ability was analyzed by alizarin red staining. The interaction between RUNX2 and CX43 was identified by dual-luciferase reporter assay. Results found that CX43 was highly expressed during TOLF, and si-CX43 could inhibit the expression of alkaline phosphatase (ALP) and osteopontin (OPN), as well as inhibit TOLF and the p38MAPK-RUNX2 pathway. In addition, SB203580 showed a synergistic effect with si-CX43 to further inhibit TOLF and the expression of RUNX2. The dual-luciferase reporter assay confirmed that RUNX2 could bind to the CX43 promoter. In conclusion, CX43 promotes TOLF, which may be mediated by p38MAPK-RUNX2, and RUNX2 binds to the CX43 promoter to form a positive feedback regulatory loop during TOLF.