Hsa-miR-520d-5p promotes survival in human dermal fibroblasts exposed to a lethal dose of UV irradiation

We previously reported that hsa-miR-520d-5p is functionally involved in the induction of the epithelial–mesenchymal transition and stemness-mediated processes in normal cells and cancer cells, respectively. On the basis of the synergistic effect of p53 upregulation and demethylation induced by 520d-5p, the current study investigated the effect of this miRNA on apoptotic induction by ultraviolet B (UVB) light in normal human dermal fibroblast (NHDF) cells. 520d-5p was lentivirally transfected into NHDF cells either before or after a lethal dose of UVB irradiation (302 nm) to assess its preventive or therapeutic effects, respectively. The methylation level, gene expression, production of type I collagen and cell cycle distribution were estimated in UV-irradiated cells. NHDF cells transfected with 520d-5p prior to UVB irradiation had apoptotic characteristics, and the transfection exerted no preventive effects. However, transfection with 520d-5p into NHDF cells after UVB exposure resulted in the induction of reprogramming in damaged fibroblasts, the survival of CD105-positive cells, an extended cell lifespan and prevention of cellular damage or malfunction; these outcomes were similar to the effects observed in 520d-5p-transfected NHDF cells (520d/NHDF). The gene expression of c-Abl (Abelson murine leukemia viral oncogene homolog 1), ATR (ataxia telangiectasia and Rad3-related protein), and BRCA1 (breast cancer susceptibility gene I) in transfectants was transcriptionally upregulated in order. These mechanistic findings indicate that ATR-dependent DNA damage repair was activated under this stressor. In conclusion, 520d-5p exerted a therapeutic effect on cells damaged by UVB and restored them to a normal senescent state following functional restoration via survival of CD105-positive cells through c-Abl-ATR-BRCA1 pathway activation, p53 upregulation, and demethylation.