Background: Asthma is usually associated with airway inflammation and airway remodeling. Epithelial mesenchymal transition (EMT) often occurs in airway remodeling. The purpose of this study is to identify the effect of miR-21-5p and Smad7 signaling pathway in macrophage-derived exosomes on EMT of airway epithelial cells.
Methods: HE staining and Masson staining were used to verify the successful establishment of the asthma model. The levels of epithelial cell adhesion factor and stromal cell markers were detected by Western blot. The levels of miR-21-5p were detected by qRT-PCR. The expression of miR-21-5p in lung tissue was further verified by fluorescence in situ hybridization (FISH). Exosome morphology was observed by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Luciferase reporter assay was applied to analyze the interaction of miR-21-5p with Smad7.
Results: The expression of miR-21-5p was upregulated in macrophages of rats in vivo with OVA-induced asthma. In vitro cultured alveolar macrophages stimulated by LPS could secrete exosomes with high levels of miR-21-5p. The exosome-derived miR-21-5p promotes EMT in rat tracheal epithelial cells through TGFβ 1/Smad signaling pathway by downregulating Smad7. This process can be blocked by miR-21-5p inhibitor.
Conclusion: Rat alveolar macrophages produced high levels of miR-21-5p-containing exosomes, which transported miR-21-5p to tracheal epithelial cells, thus promoting EMT through TGF-β 1/Smad signaling pathway by targeting Smad7.



中文翻译：

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巨噬细胞衍生外泌体中的 MiR-21-5p 靶向 Smad7 促进气道上皮细胞的上皮间质转化

背景：哮喘通常与气道炎症和气道重塑有关。上皮间质转化 (EMT) 经常发生在气道重塑中。本研究的目的是确定巨噬细胞衍生的外泌体中 miR-21-5p 和 Smad7 信号通路对气道上皮细胞 EMT 的影响。
方法：HE染色和Masson染色用于验证哮喘模型的成功建立。Western blot检测上皮细胞粘附因子和基质细胞标志物水平。通过qRT-PCR检测miR-21-5p的水平。通过荧光原位杂交（FISH）进一步验证了miR-21-5p在肺组织中的表达。通过透射电子显微镜 (TEM) 和纳米粒子跟踪分析 (NTA) 观察外泌体形态。荧光素酶报告基因分析用于分析 miR-21-5p 与 Smad7 的相互作用。
结果：OVA诱导的哮喘大鼠体内巨噬细胞中miR-21-5p的表达上调。LPS刺激的体外培养的肺泡巨噬细胞可以分泌具有高水平miR-21-5p的外泌体。外泌体来源的 miR-21-5p 通过下调 Smad7 的 TGFβ 1/Smad 信号通路促进大鼠气管上皮细胞的 EMT。这个过程可以被 miR-21-5p 抑制剂阻断。
结论：大鼠肺泡巨噬细胞产生高水平的含有miR-21-5p的外泌体，将miR-21-5p转运至气管上皮细胞，从而通过靶向Smad7的TGF-β1/Smad信号通路促进EMT。