Rationale: Ureteral obstruction-induced hydronephrosis is associated with renal fibrosis and progressive chronic kidney disease (CKD). Exosome-mediated cell-cell communication has been suggested to be involved in various diseases, including renal fibrosis. However, little is known regarding how exosomes regulate renal fibrosis in obstructed kidneys. Methods: We first examined the secretion of exosomes in UUO (unilateral ureteral obstruction) mouse kidneys and TGF-β1-stimulated tubular epithelial cells (NRK-52E). Exosomes from NRK-52E cells were subsequently harvested and incubated with fibroblasts (NRK-49F) or injected into UUO mice via the tail vein. We next constructed Rab27a knockout mice to further confirm the role of exosome-mediated epithelial-fibroblast communication relevant to renal fibrosis in UUO mice. High-throughput miRNA sequencing was performed to detect the miRNA profiles of TGFβ1-Exos. The roles of candidate miRNAs, their target genes and relevant pathways were predicted and assessed in vitro and in vivo by setting specific miRNA mimic, miRNA inhibitor, siRNA or miRNA LNA groups. Results: Increased renal fibrosis was associated with prolonged UUO days, and the secretion of exosomes was markedly increased in UUO kidneys and TGF-β1-stimulated NRK-52E cells. Purified exosomes from TGF-β1-stimulated NRK-52E cells could activate fibroblasts and aggravate renal fibrosis in vitro and in vivo. In addition, the inhibition of exosome secretion by Rab27a knockout or GW4869 treatment abolished fibroblast activation and ameliorated renal fibrosis. Exosomal miR-21 was significantly increased in TGFβ1-Exos compared with Ctrl-Exos, and PTEN is a certain target of miR-21. The promotion or inhibition of epithelial exosomal miR-21 correspondingly accelerated or abolished fibroblast activation in vitro, and renal fibrosis after UUO was alleviated by miR-21-deficient exosomes in vivo through the PTEN/Akt pathway. Conclusion: Our findings reveal that exosomal miR-21 from tubular epithelial cells may accelerate the development of renal fibrosis by activating fibroblasts via the miR-21/PTEN/Akt pathway in obstructed kidneys.

中文翻译：

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来自肾小管细胞的外泌体 miR-21 通过靶向阻塞肾脏中的 PTEN 激活成纤维细胞，从而促进肾纤维化。

基本原理：输尿管梗阻引起的肾积水与肾纤维化和进行性慢性肾病 (CKD) 相关。外泌体介导的细胞间通讯被认为与各种疾病有关，包括肾纤维化。然而，关于外泌体如何调节梗阻肾脏中的肾纤维化知之甚少。方法：我们首先检测了 UUO（单侧输尿管梗阻）小鼠肾脏和 TGF-β1 刺激的肾小管上皮细胞（NRK-52E）中外泌体的分泌。随后收获来自 NRK-52E 细胞的外泌体并与成纤维细胞 (NRK-49F) 一起孵育或通过尾静脉注射到 UUO 小鼠中。我们接下来构建了 Rab27a 敲除小鼠，以进一步证实外泌体介导的上皮-成纤维细胞通讯在 UUO 小鼠中与肾纤维化相关的作用。进行高通量miRNA测序以检测TGFβ1-Exos的miRNA谱。通过设置特定的 miRNA 模拟物、miRNA 抑制剂、siRNA 或 miRNA LNA 组，在体外和体内预测和评估候选 miRNA、它们的靶基因和相关途径的作用。结果：肾纤维化增加与 UUO 天数延长有关，UUO 肾脏和 TGF-β1 刺激的 NRK-52E 细胞中外泌体的分泌显着增加。从 TGF-β1 刺激的 NRK-52E 细胞纯化的外泌体可以在体外和体内激活成纤维细胞并加重肾纤维化。此外，通过 Rab27a 敲除或 GW4869 处理抑制外泌体分泌消除了成纤维细胞活化并改善了肾纤维化。与 Ctrl-Exos 相比，TGFβ1-Exos 中的外泌体 miR-21 显着增加，PTEN是miR-21的某个靶点。上皮外泌体 miR-21 的促进或抑制在体外相应地加速或消除了成纤维细胞的活化，而 UUO 后的肾纤维化通过 PTEN/Akt 途径在体内通过 miR-21 缺陷的外泌体得到缓解。结论：我们的研究结果表明，来自肾小管上皮细胞的外泌体 miR-21 可能通过 miR-21/PTEN/Akt 通路激活梗阻肾脏中的成纤维细胞，从而加速肾纤维化的发展。