Micro-RNAs (miRs) are small non-coding RNAs that regulate gene expression. Studies have shown that miR-200b, 146a, 21 and 378a are altered in wounds and in the circulation of diabetic (DM) rodents, implying their potential as biomarkers for non-healing wounds. Whether changes in circulating miRs are also seen in wound fluids (WF) miRs is not known. Additionally how their expression is altered by insulin (INS) treatment has not been studied.
DM was induced (STZ:65mg/kg) in male Sprague-Dawley rats and they were maintained with insulin (DM:2IU alternate days) to prevent ketoacidosis or (DM+INS:10IU daily) to maintain blood glucose levels (BGL). After 6 weeks rats (n=5-13/group) were anesthetised and were wounded with excisional wounds (4x8mm2, punch biopsy) or had PVC sponges implanted (4x1cm3 inserted via 4x2cm wounds). On day 6 post-surgery, animals were euthanised and plasma and WF from harvested sponges were obtained. miRs were extracted and expression of miR-200b, 146a, 21 and 378a were measured by qRT-PCR using Taqman probes. Results were normalised to Caenorhabditis elegans miR-39 and reported as median±IQR.
DM animals had higher BGL and lower body weight than controls and DM±INS animals (P<0.05). DM had no effect on circulating levels of these miRs in either model, although there was a tendency toward increased miR-200b and miR-146a in the excisional model which was not seen in DM+INS. In contrast increased WF miR-146a in DM (P<0.05 vs Control) was prevented by INS (P<0.005 vs DM), a similar pattern was seen for miR-21 and 378a.
These results suggest that DM has different impacts on circulating and WF expression of these miRs. The increased WF miR-146a expression in DM is consistent with increased inflammation in these animals which maybe ameliorated by insulin treatment. The utility of WF miR-146a as a biomarker of healing remains to be investigated.