Fuyuan Huoxue Decoction Promotes Lumbar Interbody Fusion in Rats: Role of Macrophage‐Driven Inflammation and the TLR9/NF‐κB Pathway

ABSTRACT

Delayed union and pseudarthrosis remain complications of lumbar interbody fusion. We investigated Fuyuan Huoxue decoction (FY) in a rat extreme lateral interbody fusion model. FY improved bone mineral density and trabecular architecture. Reduced inflammatory macrophage infiltration and nuclear factor kappa B (NF‐κB) activation at 4 weeks were accompanied by improved bony bridging at 8 weeks. Transcriptomic and network analyses nominated Toll‐like receptor 9 (TLR9)/NF‐κB signaling for functional investigation. FY‐medicated serum reduced macrophage inflammatory markers and extracellular double‐stranded DNA (dsDNA), promoted bone marrow mesenchymal stem cell (BMSC) osteogenesis, and attenuated impairment induced by inflammatory macrophage‐conditioned medium. DNase treatment reduced this medium's inhibitory effects, whereas a separate exogenous dsDNA challenge impaired osteogenesis and was attenuated by a TLR9 antagonist. TLR9 agonist and antagonist experiments in BMSCs and a 2‐week in vivo agonist intervention supported pathway involvement. Human nonunion single‐cell data showed increased phospholipid scramblase 1 and interleukin‐6 expression in myeloid cells. These findings support complementary pro‐osteogenic and anti‐inflammatory actions of FY and identify TLR9/NF‐κB as a candidate pathway contributing to fusion repair.