DNA methylation of miR-181a-5p mediated by DNMT3b drives renal interstitial fibrosis developed from acute kidney injury

<b>Aim:</b> To explore the role of miR-181a-5p in the progression of acute kidney injury (AKI) to renal interstitial fibrosis (RIF) from the perspective of DNA methylation. <b>Materials &amp; methods:</b> The role of miR-181a-5p was confirmed by collecting clinical samples, injecting miR-181a-5p agomir into tail vein, and transfecting miR-181a-5p mimic <i>in vitro</i>. The mechanism of miR-181a-5p’s influence on AKI induced RIF was investigated by methylation-specific PCR, bioinformatic analysis, transcriptome sequencing and so on. <b>Results:</b> MiR-181a-5p plays an important role in AKI induced RIF. DNMT3b-mediated miR-181a-5p promoter hypermethylation is the main reason for the downregulation of miR-181a-5p. HDAC9 and SNAI2 are direct targets of miR-181a-5p. <b>Conclusion:</b> Hypermethylation of miR-181a-5p promoter mediated by DNMT3b promotes AKI induced RIF by targeting HDAC9 and SNAI2. Renal interstitial fibrosis (RIF) is a common pathway in the progression of almost all types of chronic kidney disease (CKD) to end-stage renal disease, which severely threatens human health. Acute kidney injury (AKI) is a common clinical syndrome, which is closely correlated with the progression of RIF. However, the underlying mechanism of AKI-inducing RIF remains unclear. miR-181a-5p expression levels in the urine of AKI-CKD patients were significantly decreased compared with that of healthy volunteers. Compared with the control group, I/R mice showed decreased renal function, pathological damage of kidney tissue, and abnormal expression levels of fibrosis related proteins in kidney tissue. miR-181a-5p expression levels in I/R mice were significantly decreased compared with the Sham group. Serum creatinine and blood urea nitrogen levels were higher after I/R injury in mice, and these two indicators showed a significant decrease trend after miR-181a-5p agomir treatment. I/R led to dilation of renal tubules, sloughing of renal tubular epithelial cells (RTEC) and infiltration of inflammatory cells in the renal stroma interstitium, while overexpression of miR-181a-5p alleviated these phenomena. Over-expression of miR-181a-5p significantly restored the levels of fibrosis markers in kidney tissue. miR-181a-5p mimic treatment markedly blunted the motility of RTEC. Over-expression of miR-181a-5p significantly restored the levels of fibrosis markers in RTEC. TGF-β1 induced hypermethylation of the miR-181a-5p promoter. DNMT3b was significantly upregulated in the kidney tissue of CKD patients and RTEC that developed epithelial–mesenchymal transition. Aza, which inhibits DNMT3b activity, significantly restored the loss of miR-181a-5p. HDAC9 and SNAI2 were identified as the direct targets of miR-181a-5p. Hypermethylation of miR-181a-5p promoter mediated by DNMT3b promotes RIF developed from AKI by targeting HDAC9 and SNAI2. We anticipate that argeting the DNMT3B/miR-181a-5p/HDAC9 and SNAI2 pathway may represent a new effective therapeutic option for treating RIF developed from AKI.