gms | German Medical Science

Objectives: Multiple trauma can exert severe immunological responses at sites of injury and in the systemic circulation. Modulating the post-traumatic immune response may therefore offer therapeutic potential in the treatment of multiply traumatized patients. A novel combined inhibition therapy targeting C5 and CD14, can facilitate such a modulation. Among the cellular communication mechanisms that are involved in regulating the immune response after trauma, are microRNAs (miRNAs), key gene expression regulators with known involvements in trauma immunology and tissue regeneration. The aim of this study was therefore to investigate the effect of the novel combined C5/CD14 inhibition on the expression of miRNAs at the fracture site and in the systemic circulation over time, in a standardized porcine multiple trauma model. Furthermore, the expression of the mRNA targets of the obtained deregulated miRNAs were profiled at the fracture site and in end organs.

Methods: The multiple trauma model consisted of bilateral femur fractures, blunt chest trauma, liver laceration, and pressure controlled haemorrhagic shock. General anaesthesia was maintained throughout the whole study and animals were monitored under ICU-standards for 72 h. Two experimental groups were defined: intramedullary nailing (IMN; n=8), and IMN with combined C5/CD14 inhibition (n=4). For this study, fracture haematoma (fxH), fractured bone (fX), lung, and liver were sampled at the end of the study. Furthermore, extracellular vesicles (EVs) were isolated from plasma at four timepoints (1.5, 2.5, 24, 72 h after trauma). MiRNAs from the fxH, fX, and EVs were isolated, transcribed and pooled for qPCR arrays. Subsequently, in silico mRNA target prediction and mRNA qPCR analyses were done in the fxH, fX, and lung and liver.

Results and conclusion: The miRNA qPCR arrays and mRNA analyses showed that, compared to IMN, the combined C5/CD14 inhibition group exhibited potent anti-inflammatory miRNA and mRNA responses at the fracture site, while downregulating anti-osteogenic miRNAs. Furthermore, the combined C5/CD14 inhibition treatment reduced the expression of pro-inflammatory and pro-fibrotic EV-carried miRNAs in the systemic circulation and that of their respective downstream mRNA targets in the lung and liver.

Combined C5 and CD14 inhibition promoted anti-inflammatory miRNA and mRNA expression at the injury site, while preserving osteogenesis by downregulating anti-osteogenic miRNAs. In the systemic circulation, the C5/CD14 inhibition reduced inflammatory miRNA expression, which matched with the results from the in vivo mRNA target analyses in the lung and liver. These results warrant further research into the long-term outcomes of combined C5 and CD14 in the treatment of multiply traumatized patients.