In Bifidobacterium strains, Bifidobacterium breve, Bifidobacterium longum, and Bifidobacterium animalis can modulate the gut microbiota in OA rats, reduce the expression of the inflammatory cytokine monocyte chemoattractant protein-1 and related inflammatory factors in osteoblasts, thereby alleviating the symptoms of osteoarthritis (Li et al., 2022; Yang et al., 2025; Oh et al., 2023). The gene discussed is CCL2; the disease is osteoarthritis.