Diabetic foot ulcers represent one of the major and rising health issues, as the number of diabetic patients is increasing. MicroRNAs (miRNAs) are among various bioactive molecules under investigation for diabetic wound healing. The prolonged pro-inflammatory phase in diabetic wounds partly attributes to its non-healing nature. Therefore, we hypothesized that miRNA-497, known for its regulation of inflammatory responses, would enhance diabetic wound healing. We screened miRNA candidates, including miRNA-497 in the wounded skin of streptozotocin-induced type 1 diabetic mice. The therapeutic potential of miRNA-497 mimic was studied by intradermal injection around the wound in diabetic mice. In addition, the effects of miRNA-497 on pro-inflammatory cytokines were analyzed in the wound lesion of diabetic mice, and in human dermal fibroblasts cells exposed to high glucose and lipopolysaccharide.We found a significant reduction of miRNA-497 expression in the dermal wounds of the diabetic mice relative to normal mice. Intradermal injection of miRNA-497 around the full-thickness dermal wounds in diabetic mice accelerated wound closure effectively compared to the control miRNA. miRNA-497 treatment in vivo and in vitro decreased representative pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α. Such anti-inflammatory effects of miRNA-497 shed light on its role in accelerating diabetic wound healing. In conclusion, miRNA-497, with its down-regulation activity for pro-inflammatory cytokines, is proposed as a potential therapeutic agent for diabetic wound healing.

Emodin is a component in a Chinese herb, Rheum officinale Baill, traditionally used for diabetes and anticancer. Its poor solubility is one of the major challenges to pharmaceutical scientists. We previously reported on thermoreversible gel formulations based on poloxamer for the topical delivery of emodin. The present study was to understand the effect of poloxamer type on emodin solubility and its application in cellular activity screening. Various gel formulations composed of poloxamer 407 (P407), poloxamer 188 (P188) and PEG400 were prepared and evaluated. Major evaluation parameters were the gelation temperature (Tgel) and solubility of emodin. The emodin solubility increased with increasing poloxamer concentration and the Tgel was modulated by the proper combination of P407. In particular, this study showed that the amount of P407 in thermoreversible poloxamer gel (PG) was the dominant factor in enhancing solubility and P188 was effective at fixing gelation temperature in the desired range. A thermoreversible emodin PG was selected as the proper composition with the liquid state at room temperature and gel state at body temperature. The gel showed the solubility enhancement of emodin at least 100-fold compared to 10% ethanol or water. The thermoreversible formulation was applied for in vitro cellular activity screening in the human dermal fibroblast cell line and DLD-1 colon cancer cell line after dilution with cell culture media. The thermoreversible gel formulation remained as a clear solution in the microplate, which allowed reliable cellular activity screening. In contrast, emodin solution in ethanol or DMSO showed precipitation at the corresponding emodin concentration, complicating data interpretation. In conclusion, the gel formulation is proposed as a useful prototype topical formulation for testing emodin in vivo as well as in vitro.