Direct comparison of optical and electron microscopy methods for structural characterization of extracellular vesicles

• Published in: Journal of structural biology 2020-04, Vol.210 (1), p.107474-107474, Article 107474
• Main Authors: Noble, Jade M., Roberts, LaDeidra Monét, Vidavsky, Netta, Chiou, Aaron E., Fischbach, Claudia, Paszek, Matthew J., Estroff, Lara A., Kourkoutis, Lena F.
• Format: Article
• Language: English
• Subjects: Breast cancer; Cell Communication - physiology; Cellular communication; Cryo-scanning electron microscopy; Cryo-transmission electron microscopy; Cryoelectron Microscopy - methods; Exosomes; Exosomes - metabolism; Exosomes - ultrastructure; Extracellular vesicles; Extracellular Vesicles - metabolism; Extracellular Vesicles - ultrastructure; Female; Glycocalyx; Glycocalyx - metabolism; Humans; Microscopy, Electron, Transmission; Microvesicles; Nanoparticle tracking analysis
• ISSN: 1047-8477; 1095-8657
• DOI: 10.1016/j.jsb.2020.107474

[Display omitted] •Characterization of extracellular vesicle (EV) release from human breast cell lines.•SEM shows vesicular structures budding off of membrane tubes driven by HAS3.•Cryo-TEM reveals two EV sub-populations based upon size and structural detail.•EV surface structure is identified as biomarker for MVs compared to exosomes. As interest in the role of extracellular vesicles in cell-to-cell communication has increased, so has the use of microscopy and analytical techniques to assess their formation, release, and morphology. In this study, we evaluate scanning electron microscopy (SEM) and cryo-SEM for characterizing the formation and shedding of vesicles from human breast cell lines, parental and hyaluronan synthase 3-(HAS3)-overexpressing MCF10A cells, grown directly on transmission electron microscopy (TEM) grids. While cells imaged with conventional and cryo-SEM exhibit distinct morphologies due to the sample preparation process for each technique, tubular structures protruding from the cell surfaces were observed with both approaches. For HAS3-MCF10A cells, vesicles were present along the length of membrane protrusions. Once completely shed from the cells, extracellular vesicles were characterized using nanoparticle tracking analysis (NTA) and cryo-TEM. The size distributions obtained by each technique were different not only in the range of vesicles analyzed, but also in the relative proportion of smaller-to-larger vesicles. These differences are attributed to the presence of biological debris in the media, which is difficult to differentiate from vesicles in NTA. Furthermore, we demonstrate that cryo-TEM can be used to distinguish between vesicles based on their respective surface structures, thereby providing a path to differentiating vesicle subpopulations and identifying their size distributions. Our study emphasizes the necessity of pairing several techniques to characterize extracellular vesicles.