Longbie capsule ameliorates experimental knee osteoarthritis in association with gut microbiota and metabolic remodelling and suppression of TLR4/NF-κB signaling

Objectives Knee osteoarthritis (KOA) is a common chronic degenerative joint disease with limited disease-modifying treatment options. Longbie Capsule (LBC), a traditional Chinese medicine formulation, has shown therapeutic potential in bone and joint disorders, but its mechanisms in KOA remain incompletely defined. This study aimed to investigate the therapeutic effects and underlying mechanisms of LBC against KOA. Materials and methods Rats underwent anterior cruciate ligament transection (ACLT) or sham surgery and received vehicle, low- or high-dose Longbie Capsule, or celecoxib. Micro-computed tomography, histology, Osteoarthritis Research Society International scoring and serum cytokine measurements were used to assess joint damage and inflammation. Fecal 16 S rRNA gene sequencing and untargeted serum metabolomics were performed in the Control, KOA and high-dose LBC groups. Intestinal barrier-related measures, joint TLR4/MyD88/NF-κB signaling and extracellular matrix (extracellular matrix)-related proteins were also assessed. Fecal microbiota transplantation (FMT) examined whether fecal material from LBC-treated donors could transfer a protective effect. Results LBC alleviated cartilage degeneration and subchondral bone damage, rebalanced serum inflammatory cytokines, reshaped the gut microbiota, corrected serum metabolic perturbations, restored intestinal barrier integrity, suppressed TLR4/MyD88/NF-κB signaling and improved ECM homeostasis. FMT from LBC-treated donors partially reproduced these joint-protective effects in recipient rats. Conclusion LBC attenuated ACLT-induced joint damage in rats, accompanied by microbial and metabolic changes, improved intestinal barrier-related measures and reduced joint inflammatory signaling. Partial transfer of the protective phenotype through FMT supports a contribution of gut microbiota-associated factors to the effects of LBC.