Stress has been shown to impair wound healing with altered expression of genes regulating inflammation. Recently, microRNAs (miRs) have been identified as potent regulators of gene expression through post-transcriptional degradation of mRNA or translational repression. miRs have been linked both to normal physiologic processes as well as pathological states of many diseases. We explored miRs as a mechanism of dysregulation of inflammation during stress- impaired healing.
A 3.5 mm punch was used to create wounds in SKH-1 mice. Mice were stressed by confinement during the dark cycle (12 hours) daily in well-ventilated 50 mL tubes 3 days prior to wounding and 5 days post-wounding. Controls were food/water deprived during this same time period. Tissue samples were harvested at days 0 and 1. Using microarray screening from LC Sciences, miR-21 and miR-155 were identified as potential miRs altered by stress. miR expression was validated using qRTPCR. Using an online database (Targetscan), downstream target genes related to wound healing were identified. Candidate genes included PPARGC1B and FGF7. The expression of downstream targets was assessed using qRTPCR (20 mice/group/day).
qRTPCR indicated miR-21 levels were 5-fold lower (p=0.063) in stressed mice at day 0, and its target gene TGFBR2 was 8-fold higher (p=.038) in stressed vs. control mice. miR-155 levels were 5-fold higher (p=.046) in stressed mice at day 1, and our previous data (Mercado, 2002) indicate its target gene FGF7 was significantly lower (p<0.05) in stressed vs. control mice.
We can conclude that miRs are altered by stress, and that selected downstream target genes appear to be regulated by this altered expression of miRs. To further validate these findings, future studies can explore target gene expression levels when miR-21 and miR-155 are ameliorated to unstressed levels.
Keywords: Gene expression, Stress and Wound healing