Stress Dysregulates Inflammatory Gene Expression During Wound Healing Via miRS

Wound healing is a complex series of events aiming to clear bacteria, repair damaged tissue, and restore function, Later events rely on the successful completion of early events, thus the inflammatory phase is crucial. Neutrophils and macrophages are recruited during inflammation and facilitate bacterial clearance. Their recruitment and functions are regulated by gene expression of cytokines and other mediators. Previous studies showed that stress delays wound healing and impairs bacterial clearance. Stress can dysregulate inflammatory gene expression at the transcriptional and post-transcriptional levels. MicroRNAs (miRs), small noncoding RNAs, have emerged as potent post-transcriptional regulators. We hypothesized that stress dysregulates expression of genes involved in the inflammatory phase of wound healing via miRs and alters neutrophil and macrophage recruitment and functions leading to impaired bacterial clearance and wound healing. We report that stress-impaired bacterial clearance partly results from reduced phagocytic abilities of neutrophils and macrophages. Stress also impacts macrophage differentiation as evidenced by differential expression of activation markers. We identified 230 miRs differentially regulated during stress-impaired wound healing. This study focused on differential expression of miR-21, miR-98, miR-132, miR-155, let7b and miR-146b, and mRNA levels of miR targets regulating inflammation and proliferation during wound healing including: CXCL10, TGFβR2, GHR, PGC-1β, NFκB, MyD88 and FGF7. Finally, we studied ameliorating miR levels using a miR inhibitor as therapeutic treatment. We focused on inhibition of miR-98 by LNA-98 and gene expression of miR-98 targets, GHR and GH signaling pathway. The GH signaling pathway is involved in bacterial clearance, inflammation and tissue growth. Treatment of the stress group with LNA-98 significantly improved/restored miR-98 levels, expression of GHR and genes induced by the GH pathway (SCD1, Bcl-2, Myc, SOCS2). LNA-98 treatment enhanced wound closure and improved bacterial clearance under stress, which provides a novel and exciting therapeutic approach to ameliorate stress-impaired wound healing. This work provides strong evidence that stress dysregulates expression of genes involved in the inflammatory phase of wound healing via miRs and alters neutrophil and macrophage recruitment and functions leading to impaired bacterial clearance and altered healing. In addition, modulating miR levels constitutes a potential therapeutic treatment of stress-impaired wound healing.