Stress delays wound healing and impairs bacterial clearance at the wound site, increasing the risk of opportunistic infection. The growth hormone receptor (GHR), a key element of the GH signaling pathway, is important in bacterial clearance, inflammation and tissue growth, and is a potential target of miR-98. We hypothesize that stress induces differential expression of miR-98 that regulate GH pathway contributing to impaired inflammation and bacterial clearance and leading to poor tissue repair during wound healing.
SKH-1 mice were either food-and-water deprived (FWD) to serve as controls or stressed by restraint (RST) 12h/day for 3 days prior and 5 days post–wounding. Two punch biopsy wounds of 3.5mm were created on their backs. Wound sites were either non-treated or treated with 1uM LNA miR-98 inhibitor or scrambled sequence prior to and the day of surgery. Pictures of the wounds were taken every day for photoplanimetry. Wounds were harvested for each condition 0, 1 and 5 days post-wounding and processed for qRT-PCR (n=20) to determine the expression of miR-98, its mRNA target GHR and down-stream genes activated by GH pathway such as IGF-1.
We observed that stress up-regulated miR-98 levels at D1 by 38 fold (p<0.05) and D5 (p=0.058), which was associated with lower expression of GHR by 3 fold (p<0.1) and IGF-1 by 3 fold (p<0.05) at D1. Inhibition of miR-98 with LNA-miR-98 ameliorated wound closure (p<0.05), decreased miR-98 level to 3 folds and augmented gene expression of GHR and IGF-1.
Our study suggests that miR-98 overexpression by RST inhibits GH pathway through down-regulation of GHR. Inhibition of miR-98 improved stress-impaired wound healing and reestablished the gene expression of GHR demonstrating GH as a pathway important in regulating wound healing and the therapeutical potential for miR-98 inhibitor.
Keywords: Hormones and growth factors, Inflammation, Stress, Wound healing and miR-98
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