gms | German Medical Science

Objectives: Multiple trauma (MT) elicits immunological responses at the injury site and in the systemic circulation. The type of surgical treatment upon MT can influence tissue regeneration due to its invasiveness and timing after trauma. Two known treatment types are Early Total Care (ETC), and Damage Control Orthopedics (DCO). Cellular mechanisms that underlie the connection between surgical treatment type and tissue regeneration are not fully known. Particularly, cellular communication over distance, between organs, is of growing interest. This occurs partly through Extracellular Vesicles (EVs). Cells release EVs, which transport compounds comprising proteins, lipids, and nucleic acids, such as microRNAs (miRNAs). MiRNAs are post-transcriptional gene regulators and may regulate the activation and progression of immunological and regenerative responses after MT. The aim of this study was therefore to examine miRNA expression in plasma derived EVs of a porcine MT model, comparing two treatment types.

Methods: The porcine MT model consisted of blunt chest trauma, liver laceration, bilateral femur fracture, and controlled haemorrhagic shock. Animals were operatively and medically stabilised, and monitored under ICU-standards for 72 hours. The control group consisted of six animals. Two treatment methods were applied, ETC (n=7), and DCO (n=8). For this study, blood was sampled at five timepoints, 0, 1.5, 2.5, 24, and 72 hrs after trauma and EVs were harvested from plasma. MiRNAs were isolated, transcribed, and pooled for qPCR array analysis. Lastly, in silico messengerRNA (mRNA) target analysis was identified targets of miRNAs of interest, and the pathways they might be implicated in.

Results and conclusion: The arrays showed distinct EV-packed miRNA expression levels that varied throughout all timepoints after MT. Several miRNAs were uniformly expressed in both the control and treatment groups. Treatment specific miRNAs were identified as well as miRNAs related to the overall MT and the individual injuries, e.g. liver damage. Anti-inflammatory miRNAs were upregulated in the DCO group compared to the ETC group. In silico target analysis revealed 99 target mRNAs for the most deregulated miRNAs. Validation of these mRNA targets in lung and liver matched the expression of their upstream miRNAs.

This study revealed unique, treatment specific EV-packed miRNA expression patterns that were associated to mRNA expressions in target organs. These miRNA expression patterns showed clear systemic responses to the increased surgical trauma in the ETC group, suggesting that inflammatory responses in sustained injuries may be aggravated, and that subsequent increased systemic inflammation requires more elaborate compensatory anti-inflammatory responses. Furthermore, this study showed that miRNA transport in EVs is a lively process, showing dynamic miRNA expression patterns throughout all timepoints after MT, and that EV-packed miRNAs have a clear systemic involvement in MT.