Profiling of inflammatory and anti-inflammatory cytokines in osteomyelitic bone tissue

TL;DR

This study analyzed cytokine levels in infected bone tissue to better understand the immune and regenerative responses in osteomyelitis.

Contribution

The study provides new insights into the cytokine profiles of different osteomyelitis subtypes and their correlation patterns.

Findings

Cytokine concentrations were significantly elevated in osteomyelitic bone tissue compared to noninfected controls.

MCP-1 was higher in sternal osteomyelitis compared to vascular osteomyelitis.

Inflammatory cytokines correlated strongly with each other, while SPARC showed distinct correlation patterns.

Abstract

Osteomyelitis (OM) represents a major clinical challenge in reconstructive surgery. It is characterized by chronic infection, impaired healing, and high treatment costs. Despite the high relevance, the local immune and regenerative microenvironment of infected human bone tissue remains insufficiently characterized. This study aimed to evaluate cytokine concentrations in osteomyelitic bone tissue.

Bone samples were collected intraoperatively from patients with sternal, vascular, and posttraumatic OM and compared to noninfected control tissue. Cytokine concentrations of IL-6, IL-8, MCP-1, osteopontin, and SPARC were quantified in tissue homogenates by enzyme-linked immunosorbent assays (ELISA). Bacterial pathogens were identified using routine clinical microbiological diagnostics, and cytokine profiles were compared across the OM subgroups.

Pathogen identification revealed Staphylococcus epidermidis as the most common isolate in sternal OM, while vascular OM exhibited a broader spectrum including S. epidermidis, Corynebacterium striatum, Enterobacter cloacae, and Proteus mirabilis. Posttraumatic OM showed both monomicrobial and polymicrobial infections. The concentrations of the examined cytokines were significantly elevated in OM. No significant differences were observed between OM subtypes for most cytokines, except for MCP-1, which was higher in sternal compared to vascular OM. Spearman analysis revealed strong positive correlations between IL-6, IL-8, and MCP-1, indicating a coordinated inflammatory response. Osteopontin correlated significantly with inflammatory cytokines, while SPARC correlated primarily with osteopontin but not with inflammatory cytokines.

Cytokine profiling demonstrated simultaneous activation of inflammatory and regenerative processes in OM. The preserved regenerative marker profile across OM subtypes supports individualized surgical strategies even in chronic infections. Distinct correlation patterns between inflammatory and regenerative cytokines suggest differential regulation of immune and repair mechanisms within infected bone tissue.

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