cGAS-STING pathway mediation in osteoclast function and bone fracture healing

Objective The cGAS-STING pathway serves as a key mediator of inflammation. The aim of this study is to explore the biological role and molecular mechanisms of the cGAS-STING pathway in the fracture healing process, with a particular focus on its function during the early inflammatory phase. Methods A murine femoral fracture model was utilized to investigate the activation of the cGAS-STING pathway during the early and late stages of bone healing. The methodologies encompassed transcriptome sequencing and immunohistochemistry. Pathway modulation was accomplished through the application of the STING inhibitor H-151 and the activator SR-717, with the effects being assessed via in vivo experiments (transcriptome sequencing, microCT, safranin O-fast green staining, and TRAP staining) and in vitro assays (TRAP staining, F-actin ring formation, bone resorption tests, qPCR, and Western blot analysis). Results Transcriptome analysis revealed a higher expression of STING on day 7 compared to day 21. Immunohistochemistry results also demonstrated significant activation of the cGAS-STING pathway within the fracture callus, particularly during the initial stages of healing. Transcriptome sequencing indicated that the activation of the cGAS-STING pathway by SR-717, in contrast to H-151, predominantly impacted osteoclasts while activating the NF-κB pathway. Results from microCT, safranin O-fast green, and TRAP staining suggested that the activation of the cGAS-STING pathway contributed to facilitating fracture healing and osteoclastogenesis. In vitro experiments further confirmed that SR-717 enhanced osteoclast formation and activity, while H-151 had an inhibitory effect. The underlying molecular mechanisms further demonstrated that the activation of the cGAS-STING pathway enhanced the transmission of the RANKL-induced NF-κB signaling pathway. Conclusion The cGAS-STING pathway played a significant role in the early stages of healing in murine femoral fractures, accelerating the process of fracture repair. This pathway primarily influenced osteoclast differentiation and was associated with the key pathway of osteoclast formation, NF-κB.