Propolis Flavonoids Ameliorate Chronic Osteomyelitis in a Rat Model by Modulating TAZ‐Regulated Treg/Th17 Balance

ABSTRACT Objective To investigate the therapeutic mechanism of propolis flavonoids (PF) in chronic osteomyelitis (COM) through transcriptional coactivator with PDZ‐binding motif (TAZ)‐mediated regulation of regulatory T cell (Treg)/T helper 17 (Th17) cell homeostasis. Methods Sixty 3‐month‐old Wistar rats were randomly divided into control, model, and PF‐treated groups. In vitro, human peripheral blood mononuclear cells (PBMCs) and rat PBMCs were stratified into five treatment groups: control (10% healthy control (HC) serum), osteomyelitis model (15 ng/mL transforming growth factor‐β1 + 10% HC serum), model+PF , TEA domain transcription factor 1 (TEAD1)+model , and TEAD1+model+PF. TAZ signaling components (TAZ, RAR‐related orphan receptor gamma t (RORγt), Forkhead box P3 (FOXP3)), inflammatory cytokines (interleukin (IL)−17, IL‐21, IL‐2, IL‐10), and T cell subsets (Th17/Treg ratios) were analyzed via Western blot, enzyme‐linked immunosorbent assay (ELISA), and flow cytometry. Periosteal cell proliferation was quantified using 5‐ethynyl‐2’‐deoxyuridine (EdU) assay. Bacterial load in bone tissue was quantified using colony‐forming unit (CFU) counts. Results PF administration significantly upregulated TAZ protein expression compared to untreated osteomyelitis models ( p < 0.05). PF treatment significantly reduced bacterial burden in bone tissue ( p < 0.001). In the PF group, Th17 cell proportions increased (2.28 ± 0.35%) compared to the osteomyelitis model group (1.58 ± 0.31%) and RORγt expression was elevated, coupled with reduced Treg populations (1.66 ± 0.27%) compared to the osteomyelitis model group (11.5 ± 0.29%) and reduced FOXP3 levels. Notably, pro‐inflammatory cytokines IL‐17 and IL‐21 decreased in PF‐treated groups, while anti‐inflammatory IL‐10 and IL‐2 increased. Periosteal cell proliferation rates improved significantly with PF intervention. TEAD1 overexpression attenuated PF‐mediated effects in both human and rat PBMCs, confirming TAZ's central regulatory role across species. Conclusion Propolis flavonoids ameliorate chronic osteomyelitis through TAZ‐dependent mechanisms that rebalance Treg/Th17 polarization and promote bacterial clearance. This involves restoring Th17 cell populations while concurrently suppressing their key effector cytokines, ultimately reducing inflammatory pathology and promoting bone repair.