Transmembrane TNF-α signalling of macrophages drives pathological osteogenesis in radiographic axial
Pengfei Ji1, Peitao Xu2, Jianan Jiang1
1Department of Orthopedics, The Eighth Affiliated Hospital of Sun Yat-Sen University, Shenzhen, PR China; Guangdong Provincial Clinical Research Center for Orthopedic Diseases, The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, PR China; Biological Laboratory of Hetao Cooperation Zone, the Eighth Affiliated Hospital of Sun Yat-sen University, Shenzhen, PR China.
Objectives:
This study aimed to elucidate the molecular mechanism uncoupling inflammation from pathological osteogenesis in radiographic axial spondyloarthritis (r-axSpA), specifically investigating the role of transmembrane TNF (tmTNF) reverse signalling.
Methods:
We established a tmTNF-overexpressing transgenic mouse model that spontaneously recapitulates spinal ankylosis characteristic of r-axSpA. Single-cell RNA sequencing, genetic knockout (TNFR1/2), and macrophage depletion strategies were employed to identify cellular effectors. A mannose-modified nanoparticle system delivering Ikbkb siRNA was developed to assess targeted therapeutic intervention.
Results:
Macrophages were identified as the core drivers of osteogenesis, promoting bone formation via TGF-β3 (transforming growth factor beta 3) and BMP2 (bone morphogenetic protein 2) upregulation. Mechanistically, we discovered a novel reverse signalling axis wherein soluble TNFR1 binds to tmTNF, inducing the interaction of the tmTNF intracellular domain with the proteasome subunit alpha type-1 (PSMA1). This interaction activates the IKKβ/NF-κB (inhibitor of nuclear factor kappa B kinase subunit beta / nuclear factor kappa B) pathway to upregulate TGF-β3 and BMP2, instructing macrophages to drive mesenchymal stem cell ossification. Crucially, targeted silencing of Ikbkb in macrophages significantly inhibited new bone formation.
Conclusions:
This study reveals a distinct sTNFR1-tmTNF-PSMA1-NF-κB reverse signalling axis that empowers macrophages to drive pathological osteogenesis in r-axSpA. Targeting this axis offers a precise therapeutic strategy to arrest structural damage beyond solely controlling systemic inflammation.
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