STAPHYLOCOCCUS AUREUS-ASSOCIATED BONE DESTRUCTION IN CHRONIC OSTEOMYELITIS: POTENTIAL ANTI-INFLAMMATORY TREATMENT OPTIONS

Aim Osteomyelitis, commonly resulting from surgical procedures, open fractures, or hematogenous spread, remains a prevalent musculoskeletal infection. Increased levels of inflammatory mediators such as tumor necrosis factor (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) have been documented in osteomyelitis patients. Recent evidence suggests that anti-inflammatory TNF inhibitors (TNFi) reduce bone loss in non-bacterial osteomyelitis. However, TNF and its receptor, TNF-R1, along with several downstream effector molecules, are critical for clearing intracellular bacteria. This raises the question of whether TNFi can safely mitigate bone destruction in bacterial osteomyelitis if the infection is effectively managed surgically and with antibiotics. Method An intracellular Staphylococcus aureus infection model was established using human osteoblast-like Saos-2 cells. Cells were pre-stimulated with pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) before S. aureus infection, followed by gentamicin-killing assays. Ongoing experiments examine the impact of TNFi on intracellular bacterial survival. Additionally, using CRISPR-generated knockouts for TNF-R1, interleukin-1 receptor (IL-1R), and interleukin-6 receptor (IL-6R) in Saos-2 cells will clarify the roles of these receptors in intracellular bacterial persistence. Cell death induced by S. aureus is monitored via xCELLigence real-time cell analysis and confirmed through Western blotting. Results Preliminary findings indicate that pre-treatment with TNF-α or IL-1β modestly reduces intracellular S. aureus survival in gentamicin killing assay, with minimal differences observed across various cytokine concentrations. These finding correlate with reduced Saos-2 cell death following TNF-α stimulation during S. aureus infection, as measured by xCELLigence assays. Further data from ongoing experiments using TNFi and receptor knockouts will be presented Conclusions The observed reduction of intracellular bacteria after cytokine stimulation may result from TNF-receptosome maturation into lysosomal compartments, activating antimicrobial enzymatic pathways involving lysosomal acid sphingomyelinase (aSMase) and cathepsin D. These enzymes likely contribute to pathogen clearance within lysosomes, suggesting a potential therapeutic role for controlled anti-inflammatory treatments to limit bone damage while preserving bacterial eradication capabilities.