Burn blister fluid analysis provides an opportunity to not only non-invasively investigate the biology of the initial stages of burn injury but also to help uncover novel diagnostics to assist in clinical decision making and perhaps identify new therapeutic approaches to enhance healing.
We have recently produced the most comprehensive protein catalogue for paediatric burn blister fluid to date [1]. In the process we quantified over 800 proteins in burns of different depths and found that some of the most significantly over-represented proteins burn blister fluid indicate the existence of exosomes. We subsequently confirmed that exosomes are highly abundant in burn blister fluid. Importantly, while exosomes are known to be released by keratinocytes [2] our preliminary data is, to the best of our knowledge, the first to describe exosomes in burn blister fluids. Since exosomes are known to facilitate intercellular communication and modulate cellular function though the transfer of biomolecules between cells. This biomolecular cargo, which includes proteins and micro-RNAs (miRNA), can elicit profound regulatory effects on the cellular behaviour of recipient cells such as fibroblasts and keratinocytes [3, 4]. Our recent data, revealed that blister fluid contains Heatshock protein 90-alpha (HSP90α) which has been shown to enhance burn wound healing in mice and is also known to be carried by exosomes [1, 5]. Furthermore, several miRNA molecules have been found to modulate fibroblast response and potentially scar formation in various burn wound model systems [6-10]. Indeed, miR-181c derived from mesenchymal stem cell exosomes was found to have immunomodulatory effects in burn-induced inflammation in rats [11].
Thus whether or not blister fluid should be removed from the burn microenvironment may depend on the composition of the biomolecular cargo of resident exosomes and their potential functional effect on cells of the wound microenvironment.