Department of Nephrology, Shengjing Hospital of China Medical University, Shenyang, China.
Department of Urology, Shengjing Hospital of China Medical University, Shenyang, China.
Oxid Med Cell Longev. 2022 Oct 11;2022:2769487. doi: 10.1155/2022/2769487. eCollection 2022.
Recent studies have focused on nuclear-encoded circular RNAs (circRNAs) in kidney diseases, but little is known about mitochondrial circRNAs. Differentially expressed circRNAs were analyzed by RNA deep sequencing from lupus nephritis (LN) biopsies and normal human kidneys. In LN renal biopsies, the most downregulated circRNA was circMTND5, which is encoded in the mitochondrial genome. We quantitated circMTND5 by qPCR and localized by fluorescence in situ hybridization (FISH). Mitochondrial abnormalities were identified by electron microscopy. The expression of mitochondrial genes was decreased, and the expression of profibrotic genes was increased on qPCR and immunostaining. RNA binding sites for MIR6812 and circMTND5 were predicted. MIR6812 expression was increased by FISH and qPCR. In HK-2 cells and its mitochondrial fraction, the role of circMTND5 sponging MIR6812 was assessed by their colocalization in mitochondria on FISH, RNA immunoprecipitation, and RNA pulldown coupled with luciferase reporter assay. circMTND5 knockdown upregulated MIR6812, decreased mitochondrial functional gene expression, and increased profibrotic gene expression. Overexpression of circMTND5 reversed these effects in hTGF- stimulated HK-2 cells. Similar effects were observed in HK-2 cells with overexpression and with knockdown of MIR6812. We conclude that circMTND5 alleviates renal mitochondrial injury and kidney fibrosis by sponging MIR6812 in LN.
最近的研究集中在肾脏疾病中的核编码环状 RNA（circRNA），但对线粒体 circRNA 知之甚少。通过对狼疮肾炎（LN）活检和正常人肾脏的 RNA 深度测序分析差异表达的 circRNA。在 LN 肾活检中，下调最明显的 circRNA 是 circMTND5，它编码在线粒体基因组中。我们通过 qPCR 定量 circMTND5 并通过荧光原位杂交（FISH）定位。通过电子显微镜鉴定线粒体异常。线粒体基因的表达减少，qPCR 和免疫染色显示成纤维细胞生成基因的表达增加。预测了 MIR6812 和 circMTND5 的 RNA 结合位点。通过 FISH 和 qPCR 增加了 MIR6812 的表达。在 HK-2 细胞及其线粒体部分中，通过 FISH、RNA 免疫沉淀和 RNA 下拉结合荧光素酶报告基因测定评估 circMTND5 对 MIR6812 的海绵作用。circMTND5 敲低上调 MIR6812，降低线粒体功能基因表达，增加成纤维细胞生成基因表达。hTGF-刺激的 HK-2 细胞中转染 circMTND5 可逆转这些作用。在过表达和敲低 MIR6812 的 HK-2 细胞中观察到类似的效果。我们得出结论，circMTND5 通过海绵 MIR6812 减轻 LN 中的肾脏线粒体损伤和纤维化。
