Isolation of Exosome-Enriched Extracellular Vesicles Carrying Granulocyte-Macrophage Colony-Stimulating Factor from Embryonic Stem Cells

Summary

This study describes a method to isolate exosome-enriched extracellular vesicles carrying immune-stimulatory granulocyte macrophage colony-stimulating factors from embryonic stem cells.

Abstract

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell types, ESCs release small membrane vesicles, such as exosomes, to the extracellular environment. Exosomes serve as essential mediators of intercellular communication and play a basic role in many (patho)physiological processes. Granulocyte-macrophage colony-stimulating factor (GM-CSF) functions as a cytokine to modulate the immune response. The presence of GM-CSF in exosomes has the potential to boost their immune-regulatory function. Here, GM-CSF was stably overexpressed in the murine ESC cell line ES-D3. A protocol was developed to isolate high-quality exosome-enriched extracellular vesicles (EVs) from ES-D3 cells overexpressing GM-CSF. Isolated exosome-enriched EVs were characterized by a variety of experimental approaches. Importantly, significant amounts of GM-CSF were found to be present in exosome-enriched EVs. Overall, GM-CSF-bearing exosome-enriched EVs from ESCs might function as cell-free vesicles to exert their immune-regulatory activities.

Introduction

ESCs are derived from the blastocyst stage of a preimplantation embryo¹. As pluripotent stem cells, ESCs have the capability to self-renew and differentiate into any type of embryonic cell. Due to their remarkable developmental potential and long-term proliferative capacity, ESCs are extremely valuable for biomedical research¹. Current research efforts have largely focused on the therapeutic potential of ESCs for a variety of major pathological disorders, including diabetes, heart disease, and neurodegenerative diseases^2,3,4.

Protocol

1. Culturing ES-D3 cells

1. To generate exosome-free fetal bovine serum (FBS), load FBS into an ultracentrifuge and centrifuge at 100,000 x g for 16 h at 4 °C. Following centrifugation, collect serum supernatant as exosome-free FBS for culturing the murine ESC cell line ES-D3 and acquiring exosome-enriched EVs.
2. Before plating the ES-D3 cells, coat 15 cm tissue culture dishes using gelatin (0.1%) at room temperature for 30 min.
3. Following a previously described protocol¹⁶, culture the ES-D3 cells without feeder layer cells in the gelatin-coated 15 cm tissue culture dishes. The ES-D3 cell culture medium i....

Results

GM-CSF is overexpressed in murine ESCs.
To stably overexpress GM-CSF in ES-D3 cells, murine GM-CSF cDNA was cloned into a transfection vector to generate the expression vector pEF1α-mGM-CSF-IRES-hrGFP (Figure 1A). GM-CSF was overexpressed in ES-D3 cells by transfection, and about 20% of transiently transfected ES-D3 cells were GFP-positive. Cell clones stably overexpressing GM-CSF or the empty vector control were acquired.......

Discussion

This study shows a highly efficient method of producing exosome-enriched EVs carrying the immune-stimulatory protein GM-CSF, which can be employed to study the immune-modulatory effects of exosome-enriched EVs. Several studies suggest that exosomes exhibit immune-regulatory and anti-tumor functions²². Thus, exosomes from ESCs expressing GM-CSF might also possess biological activities that regulate the immune response. In this protocol, exogenous murine GM-CSF was stably overexpressed in murine ES-.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Alkaline phosphate, Calf Intestinal	New England Biolabs	M0290S	Dephosphorylating DNA plasmid
anti-Annexin V mAb	Santa Cruz Biotechnology	clone H-3, sc-74438	Western blot, RRID:AB_1118989
anti-CD81 mAb	Santa Cruz Biotechnology	clone B-11, sc-166029	Western blot, RRID:AB_2275892
anti-cytochrome c mAb	Santa Cruz Biotechnology	clone A-8, sc-13156	Western blot, RRID:AB_627385
anti-Flotillin-1 mAb	Santa Cruz Biotechnology	clone C-2; sc-74566	Western blot, RRID:AB_2106563
anti-GAPDH pAb	Rockland	600-401-A33S	Western blot, RRID:AB_11182910
anti-mouse IgG, goat, peroxidase-conjugated	Thermo Fisher	31430	Western blot, RRID:AB_228307
anti-Oxphos COX IV-subunit IV mAb	Thermo Fisher	clone 20E8C12 A21348	Western blot, RRID:AB_221509
anti-protein disulfide isomerase (PDI) pAb	Enzo	ADI-SPA-890	Western blot, RRID:AB_10616242
anti-rabbit IgG, goat, peroxidase-conjugated	Thermo Fisher	31460	Western blot, RRID:AB_228341
BCA (bicinchoninic acid) assay	Thermo Fisher	23223	Determining protein concentrations
Bis-Tris PAGE Gel, ExpressPlus, 4-20%	Genscript	M42015	Western blot
Carbenicillin, Disodium Salt	Thermo Fisher	10177012	Selecting E. coli colonies
Centrifuge, Avanti J-26 XPI	Beckman Coulter		Low speed centrifugation
Centrifuge rotor, JA-10	Beckman Coulter	09U1597	Low speed centrifugation
Centrifuge bottle, Nalgene PPCO	Thermo Fisher	3120-0500PK	Low speed centrifugation
Cu grids with carbon support film	Electron Microscopy Sciences	FF200-Cu	Acquiring electron microscopy images
EcoRI	New England Biolabs	R0101	Digesting DNA plasmid
Enhanced chemiluminescence detection system	Thermo Fisher	32106	Western blot
FACScalibur flow cytometer	Becton Dickinson		Examining GFP levels of ES-D3 cells
Fetal bovine serum	ATCC	SCRR-30-2020	Medium for ES-D3 cells
Fisherbrand Sterile Cell Strainers; Mesh Size: 40μm	Thermo Fisher	22-363-547	Filtering ES-D3 cells for FACS sorting
Gelatin (0.1%)	Thermo Fisher	ES006B	Culturing ES-D3 cells
GM-CSF ELISA kit	Thermo Fisher	88733422	Determining GM-CSF concentrations
KnockOut Dulbecco’s Modified Eagle’s Medium	Thermo Fisher	10-829-018	Medium for ES-D3 cells
Leukemia Inhibitory Factor	Thermo Fisher	ESG1106	Medium for ES-D3 cells
L-glutamine	VWR	VWRL0131-0100	Medium for ES-D3 cells
Lipofectamine 2000 transfection reagent	Thermo Fisher	11668019	Transfecting ES-D3 cells
Microplate reader, PowerWave XS	BioTek		Determining GM-CSF concentrations
MoFlo XDP high-speed cell sorter	Beckman Coulter		Isolating single ES-D3 cell clones
NEB 5-alpha Competent E. coli	New England Biolabs	C2988J	Generating GM-CSF expression plasmid
Neomycin	Thermo Fisher	10-131-035	Selecting ES-D3 clones
Non-essential amino acids	Thermo Fisher	SH3023801	Medium for ES-D3 cells
Non-fat dry milk	Thermo Fisher	NC9022655	Western blot
Opti-MEM I Reduced Serum Medium	Thermo Fisher	31985062	Transfecting ES-D3 cells
Paraformaldehyde	Electron Microscopy Sciences	15710	Acquiring electron microscopy images
Penicillin/streptomycin	VWR	sc45000-652	Medium for ES-D3 cells
Plasmid pEF1a-FD3ER-IRES-hrGFP	Addgene	37270	Generating GM-CSF expression plasmid
PVDF membranes	Millipore EMD	IPVH00010	Western blot
QIAprep Spin Miniprep Kit (250)	QIAGEN	27106	Generating GM-CSF expression plasmid
QIAquick Gel Extraction Kit (50)	QIAGEN	28704	Generating GM-CSF expression plasmid
Quick Ligation Kit	New England Biolabs	M2200S	Generating GM-CSF expression plasmid
Transmission electron microscope	Hitachi	HT7700	Acquiring electron microscopy images
Trypsin	VWR	45000-660	Culturing ES-D3 cells
Ultracentrifuge, OptimaTM L-100 XP	Beckman Coulter		High speed centrifugation
Ultracentrifuge rotor, 45Ti	Beckman Coulter	09U4454	High speed centrifugation
Ultracentrifuge polycarbonate bottle	Beckman Coulter	355622	High speed centrifugation
UranyLess staining solution	Electron Microscopy Sciences	22409	Acquiring electron microscopy images