Exosomes derived from hepatocellular carcinoma (HCC) cells are nanovesicles and are involved in the occurrence and development of HCC, they also serve as important carriers and drug targets of nanodrug delivery systems. The external shape and internal structure of exosomes are important indexes of identification, and isolated intact morphology is crucial to biological function integrity. However, given their susceptibility to various influencing factors, the external shape and internal structure of exosomes derived from HCC cells remain incompletely studied. In this study, exosomes purified from HCC cells were isolated at different centrifugation speeds and examined via multiple electron microscopy (EM) techniques. The results demonstrate that exosomes possess a nearly spherical shape and bilipid membranous vesicle with a concave cavity structure containing electron-dense and coated vesicles, suggesting the possible existence of subpopulations of exosomes with specific functions. The exosomes isolated at ultracentrifugation (UC) speed (≥110,000×g) presented irregular and diverse external morphologies, indicating the effect on the integrity of the exosomes. Transforming growth factor signaling bioactive substances (TGF-β1, S100A8, and S100A9) can be found in exosomes by performing Western blotting, showing that the internal content is associated with metastasis of HCC. These findings show that EMelectron microscopy and UC speed can affect exosome characteristics, including external shape, internal structure, and content of bioactive substances. The electron-dense and coated vesicles that had been discovered in exosomes might become new additional morphological features, which could help to improve the interpretation of experimental results and widen our understanding of exosome morphology.

中文翻译：

---

基于电子显微镜的比较和研究从不同离心速度分离的肝细胞癌细胞衍生的外泌体的形态

来自肝细胞癌（HCC）细胞的外泌体是纳米囊泡，参与了HCC的发生和发展，也是纳米药物递送系统的重要载体和药物靶点。外泌体的外形和内部结构是重要的鉴定指标，分离的完整形态对于生物学功能的完整性至关重要。然而，鉴于它们对各种影响因素的敏感性，源自 HCC 细胞的外泌体的外部形状和内部结构仍未得到完全研究。在这项研究中，从 HCC 细胞中纯化的外泌体以不同的离心速度分离，并通过多重电子显微镜 (EM) 技术进行检查。结果表明，外泌体具有近球形和双脂膜囊泡，具有凹腔结构，含有电子致密和包被的囊泡，表明可能存在具有特定功能的外泌体亚群。以超速离心 (UC) 速度 (≥110,000×G) 呈现不规则和多样的外部形态，表明对外泌体完整性的影响。通过Western blotting可以在外泌体中发现转化生长因子信号生物活性物质（TGF-β1、S100A8和S100A9），表明其内含物与HCC的转移有关。这些发现表明，EM电子显微镜和UC速度可以影响外泌体特征，包括外部形状、内部结构和生物活性物质的含量。在外泌体中发现的电子致密和包被的囊泡可能成为新的附加形态特征，这有助于改进对实验结果的解释，并拓宽我们对外泌体形态的理解。