title: A Protocol for Isolation and Proteomic Characterization of Distinct Extracellular Vesicle Subtypes by Sequential Centrifugal Ultrafiltration.
abstract: Scientific and clinical interest in extracellular vesicles (EVs) has increased rapidly as evidence mounts that they may constitute a new signaling paradigm. Recent studies have highlighted EVs carry preassembled complex biological information that elicit pleiotropic responses in target cells. It is well recognized that cells secrete essentially two EV subtypes that can be partially separated by differential centrifugation (DC): the larger size class (referred to as "microvesicles" or "shed microvesicles," sMVs) is heterogeneous (100-1500 nm), while the smaller size class (referred to as "exosomes") is relatively homogeneous in size (50-150 nm). A key issue hindering progress in understanding underlying mechanisms of EV subtype biogenesis and cargo selectivity has been the technical challenge of isolating homogeneous EV subpopulations suitable for molecular analysis. In this protocol we reveal a novel method for the isolation, purification, and characterization of distinct EV subtypes: exosomes and sMVs. This method, based on sequential centrifugal ultrafiltration (SCUF), affords unbiased isolation of EVs from conditioned medium from a human colon cancer cell model. For both EV subtypes, this protocol details extensive purification and characterization based on dynamic light scattering, cryoelectron microscopy, quantitation, immunoblotting, and comparative label-free proteome profiling. This analytical SCUF method developed is potentially scalable using tangential flow filtration and provides a solid foundation for future in-depth functional studies of EV subtypes from diverse cell types.
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science (LIMS), La Trobe University, Room 422, LIMS1, Bundoora, Melbourne, VIC, 3086, Australia.
authors.forename: Rong
authors.initials: R
authors.lastname: Xu
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science (LIMS), La Trobe University, Room 414, LIMS1, Bundoora, Melbourne, VIC, 3086, Australia.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Simpson
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science (LIMS), La Trobe University, Room 423, LIMS1, Bundoora, Melbourne, VIC, 3086, Australia. d.greening@latrobe.edu.au.
authors.forename: David W
authors.initials: DW
authors.lastname: Greening
mesh_terms: D002458:Cell Fractionation / Q000379:methods; D045744:Cell Line, Tumor; D055252:Cell-Derived Microparticles; D020285:Cryoelectron Microscopy; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D000067493:Dynamic Light Scattering; D055354:Exosomes; D000067128:Extracellular Vesicles / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D010316:Particle Size; D020543:Proteome; D040901:Proteomics / Q000379:methods; D014462:Ultrafiltration / Q000379:methods
chemical_list: D017077:Culture Media, Conditioned; D020543:Proteome
keywords: Exosomes; Extracellular vesicles; Purification; Sequential centrifugal ultrafiltration; Shed microvesicles