A. S. Karim1, Z. Wang2, C. Kendziorski2, A. L. Gibson1 1University Of Wisconsin,Department Of Surgery,Madison, WI, USA 2University Of Wisconsin,Department Of Biostatistics & Medical Informatics,Madison, WI, USA
Introduction: Thermal injury can result in substantial morbidity and mortality. The most important determinant of burn wound healing and the need for surgical intervention is burn depth. There is a gap in our knowledge of how burns progress and if they possess the regenerative capacity needed at various depths of injury to heal the wounds without skin grafting. This is in part due to our incomplete understanding of the interplay between inflammation and the regenerative response. In this study, we sought to characterize the wound microenvironment in deep partial (DPT) and full thickness (FT) burns using high throughput RNA sequencing in order to identify pathways for therapeutic interventions.
Methods: Non-burned (NB; n=6), DPT (n=5), and FT (n=5) tissue biopsies were obtained at the time of burn excision on days 5-10 (median: 6 days) after burn injury then submitted for RNA sequencing. After mapping and normalization, probabilities with a false discovery rate of 5% were calculated to determine differentially expressed genes (DEG). Gene sets of genes that are involved in inflammation, reactive oxygen species (ROS), regeneration, apoptosis and necroptosis were created from the list of DEG and compared in DPT and FT samples normalized to NB. One-sided, Paired t-tests of log2 transformed fold changes were used to compare the two conditions.
Results: 5416 DEG in FT and 4131 DEG in DPT tissues were identified. 1442 of the DEG were different in DPT versus FT. There were no significant differences between DPT and FT with regards to apoptosis and necroptosis (p=0.0763), but there were significant changes with regards to regenerative potential, inflammation and ROS. DPT had greater regenerative potential than FT (p<0.0001), while FT had greater inflammatory response and ROS than DPT (p<0.0001).
Conclusion: In this study we present findings suggesting that there are differences in gene expression profiles between DPT and FT burn tissues that were operatively managed. Genes that are involved in inflammation, ROS, apoptosis and necroptosis were upregulated in FT and DPT relative to NB. Regenerative capacity was significantly lower in FT compared with DPT burns. Overall, this points to an imbalance between the inflammatory and regenerative capacity which is leading to apoptosis, necroptosis and cellular senescence. Gene set enrichment analysis of the mechanisms leading to this imbalance suggests mitochondrial stress and ROS (specifically the NAPDH oxidase system) as some of the biggest mediators. Targeting ROS and preventing mitochondrial depletion may be a viable therapeutic target aimed at preventing burn wound progression and accelerating healing of burn wounds. This will ultimately reduce the need for skin grafting in these patients.
