School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, Guangdong, China.
Department of Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, Guangdong, China.
Biochim Biophys Acta Gen Subj. 2022 Feb;1866(2):130062. doi: 10.1016/j.bbagen.2021.130062. Epub 2021 Nov 22.
Numerous studies demonstrated that exosomes play a powerful role in mediating intercellular communication to induce a pro-tumoral environment to promote tumor progression, including pre-metastatic niche formation and metastasis. Noninvasive imaging could determine the in vivo kinetics of exosomes in real time to provide better understanding of the mechanisms of the tumor formation, progression and metastasis. Magnetic resonance imaging (MRI) is an ideal technique which provides excellent anatomical resolution, intrinsic soft tissue contrast, unlimited penetration depth and no radiation exposure.
A fusion protein composed of ferritin heavy chain (FTH1) and lactadherin was designed for visualizing exosomes through MRI. FTH1 was served as MRI reporter protein and lactadherin is a membrane-associated protein that is distributed on exosome surface. The characterizations of labeled exosomes were validated through transmission electron microscopy, western blot, nanoparticle tracking analysis and finally visualized in vitro and in vivo through MRI.
MR imaging showed that the labeled exosomes are able to be visualized in vitro and in vivo. Verification of the characterizations of exosomes observed no significant difference between labeled and unlabeled exosomes.
The proposed FTH1 labeling method was useful for visualizing exosomes through MRI.
The present study first reported a novel self-label method for imaging labeled exosomes of tumor cells in vivo through MR with cell endogenous MRI reporter protein. It may be further used as a tool to enhance understanding the role of exosomes in various pathophysiological conditions.
许多研究表明，外泌体在介导细胞间通讯方面发挥着强大的作用，可诱导有利于肿瘤进展的微环境，包括促进转移前生态位形成和转移。非侵入性成像可以实时确定外泌体的体内动力学，从而更好地了解肿瘤形成、进展和转移的机制。磁共振成像（MRI）是一种理想的技术，它提供了出色的解剖分辨率、固有软组织对比度、无限的穿透深度和无辐射暴露。
设计了一种由重链铁蛋白（FTH1）和乳贴蛋白组成的融合蛋白，用于通过 MRI 可视化外泌体。FTH1 用作 MRI 报告蛋白，而乳贴蛋白是一种分布在外泌体表面的膜相关蛋白。通过透射电子显微镜、western blot、纳米颗粒跟踪分析对标记的外泌体进行了表征，并最终通过 MRI 在体外和体内进行了可视化。
MR 成像显示，标记的外泌体能够在体外和体内被可视化。对外泌体特征的验证表明，标记和未标记的外泌体之间没有显著差异。
提出的 FTH1 标记方法可用于通过 MRI 可视化外泌体。
本研究首次报道了一种利用细胞内源性 MRI 报告蛋白通过 MR 对肿瘤细胞来源的标记外泌体进行体内成像的新方法。它可以进一步作为一种工具，用于增强对外泌体在各种病理生理条件下作用的理解。
