Inflammatory proteins in infected bone tissue – An explorative porcine study

Mats Bue,Natasja Leth Bergholt,Louise Kruse Jensen,Henrik Elvang Jensen,Kjeld Søballe,Maiken Stilling,Pelle Hanberg

doi:10.1016/j.bonr.2020.100292

Mats Bue, Natasja Leth Bergholt + Show 5 more

Open Access

https://doi.org/10.1016/j.bonr.2020.100292

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Abstract

ObjectiveTo explore the in situ inflammatory proteins in the local extracellular fluid of infected bone tissue. Material and methodsSeven pigs went through a two-step surgery performing a traumatically implant-associated Staphylococcus aureus osteomyelitis in the proximal tibia. Five days later, microdialysis catheters (membrane cut off: 20 kDa) were placed in the implant cavity, infected and healthy cancellous bone, and infected and healthy subcutaneous tissue. Plasma samples were collected simultaneously. We employed an antibody-based proximity extension assay (Olink Inflammatory panel) for the measurement of inflammatory molecules within plasma and extracellular fluid of the investigated tissue compartments. ResultsA higher normalized protein expression in the infected bone tissue in comparison to healthy bone tissue was identified for proteins associated with angiogenesis and bone remodeling: OPG, TGFα, MCP-1, VEGFA, and uPA. Moreover, a parallel detectability of the systemic range of cytokines and chemokines as from the investigated local tissue compartments was demonstrated, indicating the same occurrence of proteins in the local environment as within plasma. ConclusionAn angiogenic and osteogenic inflammatory protein composition within the extracellular fluid of infected bone tissue was described. The findings support the current histopathological knowledge and, therefore, microdialysis may represent a valid method for sampling of material for protein investigation of the in vivo inflammatory composition within the extracellular environment in infected bone tissue.

Highlights

Bacterial bone infections induce a massive inflammatory response
A broad range of gene ontology (GO) terms belonging to the immune response, leukocyte migration (GO:0050900), angiogenesis (GO:0001525), and blood vessel morphogenesis (GO:0048514) were identified and cell mechanisms were identified based on key proteins of interest (Fig. 1C)
Significant differences were seen for vascular endothelia growth factor A (VEGFA), uPA, OPG, CST5, MMP1, and FGF21 between microdialysates and plasma with the highest normalized protein expression (NPX) expression in plasma (Fig. 2)

Summary

Introduction

Bacterial bone infections induce a massive inflammatory response. the inflammatory composition in bone tissue emerged from bacterial infections and its impact on the final healing outcome is limited and the current knowledge is primarily based on in-vitro studies. Within the suppurative bone cavities, the histopathological changes comprised of extensive inflammatory processes characterized by the presence of neutrophils, macrophages, osteoclasts, activated fibroblasts, angiogenesis, oedema, and necrotic bone tissue (Morawietz et al, 2006; Jensen et al, 2017b). These changes are well described, whereas the in vivo biochemistry behind the inflammatory response is poorly investigated (Morawietz et al, 2006; Krenn et al, 2014; Jensen et al, 2017a; Jensen et al, 2017b). Antibody-based proximity extension assay (PEA) is a specific and sensitive technique requiring only a small amount of the target analyte within the sample in order to perform

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