MiRNA-122-5p is Upregulated in Diabetic Foot Ulcers and Decelerates the Transition from the Inflammatory to the Proliferative Stage

Transitioning from the inflammatory to the proliferative stage is critical in treating diabetic foot ulcers (DFUs), yet current treatment options are limited. MicroRNAs (miRNAs) hold significant potential in enhancing DFU healing. Previous studies have shown that miR-122-5p targets the regulation of diabetic metalloproteinases, impacting the extracellular matrix. We hypothesize that miR-122-5p plays a crucial role in the healing of DFU. MiR-122-5p levels in skin tissue samples from both patients with diabetic ulcers and diabetic mice were evaluated using quantitative real-time PCR (qRT-PCR). The streptozotocin-induced diabetes mouse model for diabetic wound healing was utilized. Animals were randomized to receive intradermal injections of either an AAVDJ empty vector (AAVDJ-EV, control) or AAVDJ-miR-122 upregulation vector. Mice were euthanized at different intervals (3, 7, and 14 days post-injury), and wound tissues were collected for gene marker analysis, histological evaluation, immunohistochemistry, and network analysis. The study focused on proteins involved in the transition from the inflammatory to the proliferative stage during DFU healing. Additionally, the role of miR-122-5p in mediating interactions between mouse macrophages and fibroblasts was analyzed. FISH and qRT-PCR results indicated that miR-122-5p levels were significantly upregulated in diabetic skin, both in individuals with DFU and diabetic mice, compared to controls. Western blot, IHC, and ELISA results indicated that in vitro, upregulation of miR-122-5p increased MMP9 expression and levels of inflammatory mediators such as TNF-α and HIF-1α, while concurrently decreasing expression levels of VEGF and markers associated with fibrosis such as FN1 and α-SMA.Our findings confirmed that miR-122-5p increases inflammatory cytokines and reduces fibrosis in fibroblasts cultured with macrophage-conditioned media.MiR-122-5p increased inflammation and reduce fibrosis during wound healing of diabetic mice, slowing the transition from the inflammatory to the proliferative stage. These findings open the door to understanding how miRNAs functionally contribute to human skin wound healing.