miR-19a/b and miR-20a Promote Wound Healing by Regulating the Inflammatory Response of Keratinocytes

Abstract

Persistent and impaired inflammation impedes tissue healing and is a characteristic of chronic wounds. A better understanding of the mechanisms controlling wound inflammation is needed. In this study, we show that in human wound-edge keratinocytes, the expressions of microRNA (miR)-17, miR-18a, miR-19a, miR-19b, and miR-20a, which all belong to the miR-17w92 cluster, are upregulated during wound repair. However, their levels are lower in chronic ulcers than in acute wounds at the proliferative phase. Conditional knockout of miR-17w92 in keratinocytes as well as injection of miR-19a/b and miR-20a antisense inhibitors into wound edges enhanced inflammation and delayed wound closure in mice. In contrast, conditional overexpression of the miR-17w92 cluster or miR-19b alone in mice keratinocytes accelerated wound closure in vivo. Mechanistically, miR-19a/b and miR-20a decreased TLR3-mediated NF-kB activation by targeting SHCBP1 and SEMA7A, respectively, reducing the production of inflammatory chemokines and cytokines by keratinocytes. Thus, miR-19a/b and miR-20a being crucial regulators of wound inflammation, the lack thereof may contribute to sustained inflammation and impaired healing in chronic wounds. In line with this, we show that a combinatory treatment with miR-19b and miR-20a improved wound healing in a mouse model of type 2 diabetes.

The Immune Functions of Keratinocytes in Skin Wound Healing

“…The expression of TLR1, TLR2, TLR4, TLR6, TLR9, and MyD88 has been found to be significantly upregulated in the wounds of diabetic patients compared with nondiabetic wounds [164,165]. We also show that the TLR3 protein level is elevated in the wound-edge epidermis of human diabetic foot ulcers, venous ulcers, and pressure ulcers, contributing to the increased neutrophil and macrophage infiltration in these chronic wounds [144]. A single-nucleotide polymorphism (SNP) study revealed that TLR4 and TLR9 SNPs and their haplotypes may increase the risk of impaired wound healing in type 2 diabetic patients [166,167].…”

“…These two miRNAs promote keratinocyte inflammatory chemokine and cytokine production by targeting leucine rich repeat containing G protein-coupled receptor 4 (LGR4) [146]. We also showed that the levels of all miR-17∼92 cluster members, i.e., miR-17, miR-18a, miR-19a, miR-19b, and miR-20a, decreased in several types of human chronic ulcers, including pressure ulcers, venous ulcers, and diabetic foot ulcers, in comparison with normal acute wounds [144]. Moreover, miR-19a/b and miR-20a were found to reduce keratinocyte production of inflammatory chemokines and cytokines by regulating the TLR3-NF-κB signaling pathway by targeting SHC binding and spindle associated 1 (SHCBP1) and semaphorin 7A (SEMA7A) [144].…”

“…Decreases TLR3 13 -mediated NF-κB activation in keratinocytes SHCBP1 14 [144] hsa-miR-20a-5p Decreases TLR3-mediated NF-κB activation in keratinocytes SEMA7A 15 [144] hsa-miR-146a-5p Inhibits the NF-κB signaling pathway in keratinocytes IRAK1 16 and TRAF6 [145] hsa-miR-34a-5p and hsa-miR-34c-5p…”

“…IL8 is a vital neutrophil chemotactic factor and induces neutrophils to migrate to the site of IL8 production, while CCL2 exhibits a chemotactic activity for macrophages. The elevated number of macrophages and neutrophils in chronic wounds may be partially due to the dysregulated cytokine expression in keratinocytes at the nonhealing wound edge [144].…”

“…Multiple miRNAs are dysregulated in human chronic wounds and contribute to delayed wound healing through regulating keratinocyte immune functions, e.g., miR-132, miR-146, miR-34a/c, miR-19a/b, miR-20a, miR-203, miR-21, and miR-130 [127,[144][145][146]148,150] (Table 2). The miR-132 expression is significantly reduced in human diabetic ulcers compared with normal acute wounds [178].…”