STING contributes to trauma-induced heterotopic ossification through NLRP3-dependent macrophage pyroptosis

Trauma-induced heterotopic ossification (HO) is featured by aberrant bone formation at extra-skeletal site. STING is a master adaptor protein linking cellular damage to immune responses, while its role in HO remains elusive. A murine burn/tenotomy model was used to mimic trauma-induced HO in vivo. We demonstrated elevated STING expression in macrophages in inflammatory stage after burn/tenotomy, and STING inhibition significantly alleviated HO formation. Activated NLRP3-dependent macrophage pyroptosis was also found in inflammatory stage after burn/tenotomy. Either STING or NLRP3 suppression reduced mature HO by weakening macrophage pyroptotic inflammation, while protective effects of STING were abolished by NLRP3 overexpression. Further, in vitro, we also found a prominent STING level in pyroptotic BMDMs. STING suppression relieved macrophage pyroptotic inflammation, while abolished by NLRP3 overexpression. Our results reveal that STING poses regulatory effects on trauma-induced HO formation, via modulating NLRP3-dependent macrophage pyroptosis. Targeting STING-NLRP3 axis represents an attractive approach for trauma-induced HO prevention. Graphical summary of effects and mechanisms of STING on NLRP3-dependent macrophage pyroptosis that regulate traumatic HO progression. After burn/tenotomy, macrophages accumulate in the tendon lesions, and the elevated expression of cGAS-STING pathway further activates NLRP3 inflammasome in the macrophages, leading to aggravated pyroptosis and related inflammation. The built inflammatory immune microenvironment recruits TSPCs and induces osteogenesis differentiation, and finally leads to HO formation. Further, STING inhibitor (C-176) could suppress macrophages pyroptosis by inhibiting the NLRP3/Caspase 1 signaling involved in these biological processes, thereby inhibiting the HO formation. [Display omitted]