MicroRNA-155 as a Molecular Indicator of Diabetic Foot Ulcers

Abstract

Background: Diabetic foot ulcers (DFUs) are characterised by an imbalanced wound microenvironment, in which the molecular processes that regulate the inflammation-to-tissue-repair transition are impaired. MicroRNA-155 (miR-155) is a known immuno-inflammatory regulator whose expression is context-specific and has not been fully described in paired systemic and local tissue compartments in the diabetic context. Aims: To measure the level of miR-155 in the whole blood of diabetic patients with DFUs and in matched ulcer-tissue biopsies by reverse-transcription quantitative PCR (RT-qPCR); to compare miR-155 levels in whole blood and ulcer-tissue biopsies of diabetic patients with healthy controls; and to determine the relative differences between the systemic and localised levels. Study Design: A comparative cross-sectional molecular study. Place and Duration of Study: [Alhakem hospital l/Najaf], Najaf, Iraq, between April 2025 and November 2025. Methodology: Eighteen participants were recruited: nine patients with DFUs, each contributing a whole-blood sample and a matched ulcer-margin tissue biopsy, and nine healthy controls contributing whole-blood samples, yielding 27 biological specimens in total. TRIzol reagent was used to extract total RNA. RT-qPCR using SYBR Green, stem-loop reverse transcription, and U6 snRNA as the endogenous control was used to measure miR-155. The 2−ΔΔCt method was used to calculate relative expression. One-way ANOVA was used for group comparisons, followed by post-hoc testing; p < 0.05 was considered statistically significant. Results: miR-155 showed a significant down-regulation in the peripheral blood of DFU patients compared with healthy controls (fold change: 0.026 vs. 1.00; p < 0.0001), corresponding to an approximately 38-fold decrease. The corresponding mean Ct values were 29.69 ± 1.4 (DM) versus 22.45 ± 1.2 (Control). Local ulcer-tissue biopsies produced a mean Ct of 24.11 ± 1.8, which, when compared with a validated public reference (NCBI GEO/GTEx healthy-skin ΔCt baseline = 6.0), revealed significant local depletion of miR-155 at the wound site. The demographic profile was well matched between groups (age: 58.7 ± 7.4 vs. 52.4 ± 6.1 years; p = 0.12), while glycaemic control differed significantly (HbA1c: 9.1 ± 1.5% vs. 5.2 ± 0.4%; p < 0.001). Conclusion: DFU patients showed a significant systemic and local down-regulation of miR-155, which provides molecular evidence of an immunological failure characterised by impaired macrophage activation, suppressed fibroblast growth factor 7 (FGF7)-dependent re-epithelialisation, and perpetuation of the non-resolving inflammatory state. miR-155 holds promise as a quantifiable molecular biomarker of DFU severity and as a candidate target for antagomir-based therapeutic intervention.