Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Cells. 2020 Apr 26;9(5):1080. doi: 10.3390/cells9051080.
The corneal epithelium mediates the initial response to injury of the ocular surface and secretes a number of profibrotic factors that promote corneal scar development within the stroma. Previous studies have shown that corneal epithelial cells also secrete small extracellular vesicles (EVs) in response to corneal wounding. In this paper, we hypothesized that EVs released from corneal epithelial cells in vitro contain protein cargo that promotes myofibroblast differentiation, the key cell responsible for scar development. We focused on the interplay between corneal epithelial-derived EVs and the stroma to determine if the corneal fibroblast phenotype, contraction, proliferation, or migration were promoted following vesicle uptake by corneal fibroblasts. Our results showed an increase in myofibroblast differentiation based on α-smooth muscle actin expression and elevated contractility following EV treatment compared to controls. Furthermore, we characterized the contents of epithelial cell-derived EVs using proteomic analysis and identified the presence of provisional matrix proteins, fibronectin and thrombospondin-1, as the dominant encapsulated protein cargo secreted by corneal epithelial cells in vitro. Proteins associated with the regulation of protein translation were also abundant in EVs. This paper reveals a novel role and function of EVs secreted by the corneal epithelium that may contribute to corneal scarring.
角膜上皮介导眼表面损伤的初始反应，并分泌许多促纤维化因子，促进基质内角膜瘢痕的形成。先前的研究表明，角膜上皮细胞在受到角膜损伤时也会分泌小细胞外囊泡（EVs）。在本文中，我们假设体外培养的角膜上皮细胞释放的 EVs 中含有促进成肌纤维细胞分化的蛋白 cargo，而成肌纤维细胞是导致瘢痕形成的关键细胞。我们重点研究了角膜上皮衍生 EVs 与基质之间的相互作用，以确定角膜成纤维细胞摄取囊泡后，其表型、收缩、增殖或迁移是否得到促进。我们的结果表明，与对照组相比，EV 处理后α-平滑肌肌动蛋白表达增加，收缩力升高，导致成肌纤维细胞分化增加。此外，我们使用蛋白质组学分析对上皮细胞衍生 EVs 的内容进行了表征，并发现了存在的细胞外基质蛋白，纤维连接蛋白和血小板反应蛋白-1，作为体外培养的角膜上皮细胞分泌的主要包裹蛋白 cargo。EVs 中还富含与蛋白质翻译调控相关的蛋白。本文揭示了角膜上皮分泌的 EVs 的新作用和功能，可能与角膜瘢痕形成有关。
