Exploring interstitial mediators in burn injury

Abstract

Burn injury remains a major clinical challenge to both survival and to quality of life. Its progressive, aberrant inflammation underlies the lethal dysfunction of various organs and the pain it induces is excruciating and notoriously difficult to manage. While it is known that burn injury’s complex local and disseminating pathology is orchestrated from the burned tissue, few studies have sought to characterise the local signalling environment. An enhanced understanding of the local and acutely temporally-dynamic processes defining burn injury and its progression is required for the development of novel therapeutic interventions. First, the viability of microdialysis as an interstitial sampling technique was established in a histologically-validated deep partial-thickness rat burn model before analysing the microdialysate’s dynamic composition over three hours post-burn via metabolomics and a multiplex cytokine immunoassay. Next-Generation sequencing libraries of the burn and control microdialysis sites were prepared to measure transcriptional changes potentially underlying the interstitial profile characterising burn injury. The cytokines leptin and fractalkine, three lysophosphatidylcholine species (LPC(18:0), LPC(16:0) and LPC(14:0)), niacinamide and uric acid were all identified as molecules upregulated locally in the burn injury interstitium for the first time, which was further supported by the differential expression of their associated genes. In vitro study of LPC(18:0)’s possible contribution to inflammation and/or pain in burn injury elucidated its potentiation of TRPV1-mediated nociceptor responses, highlighting this interaction as a potential mechanism of lysophosphatidylcholine’s established inflammatory and algogenic effects and implicating them in burn injury. This project is the first exploratory analysis of the burn site interstitium, demonstrating the feasibility of combining local and continuous sampling with untargeted and multiplex molecular profiling for comprehensive study of any pathological state. Elucidating the functional relevance of the many elevated mediators and the nociceptor sensitisation reported presently in burn injury is an exciting prospect.