Overexpression of miR-340-5p Inhibits Skin Fibroblast Proliferation by Targeting Kruppel-like Factor 2

Objective: MicroRNA (miR)-340-5p has been identified to play a key role in several cancers. However, the function of miR-340-5p in skin fibroblasts remains largely unknown. Methods: Gain of function experiments were performed by infecting normal skin fibroblast cells with a lentivirus carrying 22-bp miR-340-5p. Cell proliferation was detected by Cell Counting Kit-8 (CCK-8) assay. To uncover the mechanisms, mRNA-seq was used. Differentially expressed mRNAs were further determined by Gene Ontology and KEGG pathway analyses. The protein levels were analysed by Western blotting. A dual-luciferase reporter assay was used to detect the direct binding of miR-340-5p with the 3'UTR of Kruppel-like factor 2 (KLF2). Results: MiR-340-5p lentivirus infection suppressed normal skin fibroblast proliferation. The mRNA-seq data revealed that 41 mRNAs were differentially expressed, including 22 upregulated and 19 downregulated transcripts in the miR-340-5p overexpression group compared with those in the control group. Gene Ontology and KEGG pathway analyses revealed that miR-340-5p overexpression correlated with the macromolecule biosynthetic process, cellular macromolecule biosynthetic process, membrane, and MAPK signalling pathway. Bioinformatics analysis and luciferase reporter assays showed that miR-340-5p binds to the 3'UTR of KLF2. Forced expression of miR-340-5p decreased the expression of KLF2 in normal skin fibroblasts. Overexpression of KLF2 restored skin fibroblast proliferation in the miR-340-5p overexpression group. Conclusion: This study demonstrates that miR-340-5p may suppress skin fibroblast proliferation, possibly through targeting KLF2. These findings could help us understand the function of miR-340-5p in skin fibroblasts. miR-340-5p could be a therapeutic target for preventing scarring.