RUNX1 Inhibites NF-κB/IL-6 Signaling to Promote Bone Remodeling and Suppress Bone Resorption in Mice with Juvenile Ischemic Osteonecrosis

Abstract

Background: Previous studies have identified the role of Runt-related transcription factor 1 (RUNX1) in enhancing bone formation by promoting both chondrogenesis and osteogenesis. However, its precise function in juvenile ischemic osteonecrosis (JIO) remains unclear and needs more comprehensive investigation. This current research aims to determine the influence of RUNX1 and the mechanisms on JIO. Methods: Immature C57BL/6 male mice were randomly divided into 4 groups: the Sham, the Osteonecrosis, the Osteonecrosis+negative control (NC), and the Osteonecrosis+RUNX1 groups. Mice in Sham group underwent a sham operation. In Osteonecrosis group, JIO mouse model was established. In Osteonecrosis+NC or Osteonecrosis+RUNX1 group, JIO mouse model was treated with empty lentivirus or RUNX1 overexpression lentivirus. The femoral head tissues of the JIO mice were then evaluated for histopathological changes through hematoxylin-eosin staining. Additionally, the articular chondrocyte necrosis and glycosaminoglycan accumulation in the articular cartilage were examined using Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining and safranin O-fast green staining. The expressions of proteins related to the nuclear factor-kappa B (NF-κB)/interleukin 6 (IL-6) signaling and related to bone remodeling and resorption in the femoral head tissues of the JIO mice were quantified by western blot. Results: Our findings demonstrate that long-term treatment with RUNX1 alleviated femur osteonecrosis in JIO mice. The same treatment relieved articular chondrocyte necrosis and enhanced glycosaminoglycan accumulation in the articular cartilage (p < 0.01). Significantly, treatment with RUNX1 impeded the activation of NF-κB/IL-6 signaling, upregulated the expression of bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF), and downregulated the receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG) ratios in the femoral head tissues of the JIO mice (p < 0.001). Conclusions: RUNX1 blocked NF-κB/IL-6 signaling to promote bone remodeling and suppress the bone resorption in JIO mice. These findings provide a new theoretical framework for further research and potential therapeutic strategies in JIO treatment.