School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, Guangdong, China.
Department of Radiology, Guangzhou First People's Hospital, South China University of Technology, Guangzhou 510180, Guangdong, China.
Magn Reson Imaging. 2020 May;68:75-82. doi: 10.1016/j.mri.2020.02.001. Epub 2020 Feb 3.
We develop a method of imaging exosomes in vivo according to the vital role of exosomes in intercellular communication. This study aims to design a new label method that allows the visualization of labeled exosomes with magnetic resonance imaging (MRI).
We designed a fusion protein consisting of two parts, namely, ferritin heavy chain (FTH1) and a truncated lactadherin. FTH1 is used as an MRI reporter. Lactadherin is a trans-membrane protein. The lactadherin protein are mostly located on the outer surface of exosomes. We replaced the outer membrane part of lactadherin with FTH1, infected mesenchymal stem cells with lentivirus carrying the fusion protein, and isolated exosomes from the labeled cells by ultracentrifugation. Labeled exosomes were validated by transmission electron microscopy images, Western blot, nanosight particle tracking, and visualized in vitro and in vivo by MRI.
FTH1 expression would suppress mesenchymal stem cell proliferation, whereas the characterization of labeled exosomes remains comparable with unlabeled exosomes. MR imaging shows that exosomes labeled with FTH1 can be visualized in vitro and in vivo.
This innovative reporter-imaging approach to track and visualize exosomes with MRI can be utilized as a tool for the study of the role of exosomes under different conditions.
我们根据外泌体在细胞间通讯中的重要作用，开发了一种在体内对其进行成像的方法。本研究旨在设计一种新的标记方法，使磁共振成像（MRI）能够可视化标记的外泌体。
我们设计了一种由两部分组成的融合蛋白，即铁蛋白重链（FTH1）和截断的乳凝集素。FTH1 用作 MRI 报告器。乳凝集素是一种跨膜蛋白。乳凝集素蛋白主要位于外泌体的外表面。我们用 FTH1 替换乳凝集素的外膜部分，用携带融合蛋白的慢病毒感染间充质干细胞，并通过超速离心从标记的细胞中分离出外泌体。通过透射电子显微镜图像、Western blot、纳米粒子跟踪和 MRI 在体外和体内对标记的外泌体进行验证。
FTH1 的表达会抑制间充质干细胞的增殖，而标记的外泌体的特征与未标记的外泌体仍具有可比性。磁共振成像显示，用 FTH1 标记的外泌体可以在体外和体内可视化。
这种用于追踪和可视化外泌体的创新报告器成像方法可作为研究不同条件下外泌体作用的工具。
