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Exosomes: A big role for a small player

Exosomes uncovered. Recent research and the role of exosomes in disease


Tiny vesicles of macromolecules (30-120nm) secreted by cells called exosomes have come to the forefront of cancer, neurodegeneration, immunology, and more research areas. They were first described by Rose Johnstone’s group in 1983 in the context of transferrin receptor secretion by sheep reticulocytes. As technologies to study these vesicles improved, exosomes went from a niche mechanism to playing a broad signaling role after the discovery by Valadi et al that the RNAs inside can be used to exchange information between cells. Further investigation revealed that they also contain proteins and are found in a variety of body fluids including saliva, blood, and urine.

Like traditional vesicles, exosomes are formed in the endosomal pathway. During late endosomal maturation, intraluminal vesicles containing a variety of macromolecules form inside the endosome. Rather than fusing with the lysosome afterward, the late endosome fuses with the plasma membrane, releasing the intraluminal vesicles as exosomes.

Applications for cancer, immunology, and diagnostics

Recent work has uncovered a variety of roles for exosomes. For instance, Cheng et al showed that they play a role in cardiac tissue repair after an infarction, sending miRNAs that mobilize bone marrow progenitor cells. Also, Ramkumar Menon’s group at the University of Texas Medical Branch found that maternal exosomes can be delivered to the developing fetus and may impact tissue function. In cancer, Chen and colleagues discovered that exosomal PD-L1 secreted by metastatic lesions enhances tumor immunosuppression and is associated with poor clinical response. Lastly, Fan et al recently showed that cancer cells can use an alternative exosomal development pathway to create pro-tumorigenic exosomes.   

Due to their payloads, tropism, and ubiquity, exosomes also have exciting applications for diagnostics and drug delivery. Since exosomes contain proteins and nucleic acids from their origin, they have been used to diagnose and monitor disease. An example is exosomal CD63, which can be used to identify melanoma. Exosomal tau can also be used to detect the onset of early Alzheimer’s disease.

Besides diagnostics, there is potential for improving drug delivery. Drawbacks of current generation nanoparticle therapies include pre-mature drug release and high immunogenicity. However, exosomes have low immunogenicity, can be loaded with drug payload, and can be cell-targeted through their surface molecules. Exosomes are also small enough to pass through the blood-brain barrier, so there is potential for neurodegenerative and brain tumor treatment.

Methods to study exosomes

To isolate and study exosomes, there are a few biochemical methods including sucrose gradient and differential ultracentrifugation. Besides their small size, a challenge is their lability. Though cost-effective, differential ultracentrifugation methods may distort membranes and destroy others, lowering yields. By contrast, sucrose gradient centrifugation creates a “cushion” while helping remove contaminants and protocols have been developed to maximize yield and improve the workflow.

Once isolated, flow cytometry is a popular means of characterizing exosomes. Examining the cell surface markers can provide information regarding the origin of an exosome and potential tropism. For instance, the presence of ICAM-1, B7.2, and MHC Class II indicates a dendritic cell origin.

There is much more to learn about exosomes and Proteintech offers a variety of helpful markers that can aid you in your journey. Below are a few popular markers:

Target Catalog Number Citations Validation
ALIX 12422-1-AP 42 WB, IP, IHC, IF, ELISA
Annexin V 66245-1-Ig   WB, IHC, IF, FC, ELISA
Calnexin CL488-66903   IF, ELISA
CD9 FITC-65070   FC
CD63 25682-1-AP 71 WB, IHC, IF, FC, ELISA
CD81 66866-1-Ig 15 WB, FC, ELISA
EPCAM CL594-66316   IF, ELISA
Flotillin 1 15571-1-AP 13 WB, IP, IHC, IF, FC, ELISA
GM130 11308-1-AP 27 WB, IHC, IF, FC, ELISA
GRP94 60012-1-Ig 3 WB, IHC, IF, FC, CoIP, ELISA
MIA 15734-1-AP   IHC, ELISA
RAB11A 20229-1-AP 6 WB, IP, IHC, IF, ELISA
Syntenin-1 22399-1-AP 3 WB, IP, IHC, IF, FC, ELISA
TSG101 14497-1-AP 95 WB, IP, IHC, IF, FC, ELISA

References:

  1. Pan BT, Johnstone RM. Fate of the transferrin receptor during maturation of sheep reticulocytes in vitro: selective externalization of the receptor. Cell. 1983 Jul;33(3):967-78. doi: 10.1016/0092-8674(83)90040-5. PMID: 6307529.
  2. Valadi H, Ekström K, Bossios A, Sjöstrand M, Lee JJ, Lötvall JO. Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat Cell Biol. 2007 Jun;9(6):654-9. doi: 10.1038/ncb1596. Epub 2007 May 7. PMID: 17486113.
  3. Lin J, Li J, Huang B, Liu J, Chen X, Chen XM, Xu YM, Huang LF, Wang XZ. Exosomes: novel biomarkers for clinical diagnosis. ScientificWorldJournal. 2015;2015:657086. doi: 10.1155/2015/657086. Epub 2015 Jan 27. PMID: 25695100; PMCID: PMC4322857.
  4. Logozzi M, De Milito A, Lugini L, Borghi M, Calabrò L, Spada M, Perdicchio M, Marino ML, Federici C, Iessi E, Brambilla D, Venturi G, Lozupone F, Santinami M, Huber V, Maio M, Rivoltini L, Fais S. High levels of exosomes expressing CD63 and caveolin-1 in plasma of melanoma patients. PLoS One. 2009;4(4):e5219. doi: 10.1371/journal.pone.0005219. Epub 2009 Apr 17. PMID: 19381331; PMCID: PMC2667632.
  5. Saman S, Kim W, Raya M, Visnick Y, Miro S, Saman S, Jackson B, McKee AC, Alvarez VE, Lee NC, Hall GF. Exosome-associated tau is secreted in tauopathy models and is selectively phosphorylated in cerebrospinal fluid in early Alzheimer disease. J Biol Chem. 2012 Feb 3;287(6):3842-9. doi: 10.1074/jbc.M111.277061. Epub 2011 Nov 4. PMID: 22057275; PMCID: PMC3281682.
  6. Chen CL, Lai YF, Tang P, Chien KY, Yu JS, Tsai CH, Chen HW, Wu CC, Chung T, Hsu CW, Chen CD, Chang YS, Chang PL, Chen YT. Comparative and targeted proteomic analyses of urinary microparticles from bladder cancer and hernia patients. J Proteome Res. 2012 Dec 7;11(12):5611-29. doi: 10.1021/pr3008732. Epub 2012 Oct 31. PMID: 23082778.
  7. Arrighetti N, Corbo C, Evangelopoulos M, Pastò A, Zuco V, Tasciotti E. Exosome-like Nanovectors for Drug Delivery in Cancer. Curr Med Chem. 2019;26(33):6132-6148. doi: 10.2174/0929867325666180831150259. PMID: 30182846; PMCID: PMC6395517.
  8. Alvarez-Erviti L, Seow Y, Yin H, Betts C, Lakhal S, Wood MJ. Delivery of siRNA to the mouse brain by systemic injection of targeted exosomes. Nat Biotechnol. 2011 Apr;29(4):341-5. doi: 10.1038/nbt.1807. Epub 2011 Mar 20. PMID: 21423189.
  9. Parida BK, Garrastazu H, Aden JK, Cap AP, McFaul SJ. Silica microspheres are superior to polystyrene for microvesicle analysis by flow cytometry. Thromb Res. 2015 May;135(5):1000-6. doi: 10.1016/j.thromres.2015.02.011. Epub 2015 Feb 16. PMID: 25726425.
  10. Theodoraki, M.‐N., Hong, C.‐S., Donnenberg, V.S., Donnenberg, A.D. and Whiteside, T.L. (2020), Evaluation of Exosome Proteins by on‐Bead Flow Cytometry. Cytometry. doi:10.1002/cyto.a.24193
  11. Segura E, Amigorena S, Théry C. Mature dendritic cells secrete exosomes with strong ability to induce antigen-specific effector immune responses. Blood Cells Mol Dis. 2005 Sep-Oct;35(2):89-93. doi: 10.1016/j.bcmd.2005.05.003. PMID: 15990342.
  12. Chen G, Huang AC, Zhang W, Zhang G, Wu M, Xu W, Yu Z, Yang J, Wang B, Sun H, Xia H, Man Q, Zhong W, Antelo LF, Wu B, Xiong X, Liu X, Guan L, Li T, Liu S, Yang R, Lu Y, Dong L, McGettigan S, Somasundaram R, Radhakrishnan R, Mills G, Lu Y, Kim J, Chen YH, Dong H, Zhao Y, Karakousis GC, Mitchell TC, Schuchter LM, Herlyn M, Wherry EJ, Xu X, Guo W. Exosomal PD-L1 contributes to immunosuppression and is associated with anti-PD-1 response. Nature. 2018 Aug;560(7718):382-386. doi: 10.1038/s41586-018-0392-8. Epub 2018 Aug 8. PMID: 30089911; PMCID: PMC6095740.
  13. Cheng M, Yang J, Zhao X, Zhang E, Zeng Q, Yu Y, Yang L, Wu B, Yi G, Mao X, Huang K, Dong N, Xie M, Limdi NA, Prabhu SD, Zhang J, Qin G. Circulating myocardial microRNAs from infarcted hearts are carried in exosomes and mobilise bone marrow progenitor cells. Nat Commun. 2019 Feb 27;10(1):959. doi: 10.1038/s41467-019-08895-7. PMID: 30814518; PMCID: PMC6393447.
  14. Sheller-Miller S, Choi K, Choi C, Menon R. Cyclic-recombinase-reporter mouse model to determine exosome communication and function during pregnancy. Am J Obstet Gynecol. 2019 Nov;221(5):502.e1-502.e12. doi: 10.1016/j.ajog.2019.06.010. Epub 2019 Jun 14. PMID: 31207235.
  15. Fan SJ, Kroeger B, Marie PP, Bridges EM, Mason JD, McCormick K, Zois CE, Sheldon H, Khalid Alham N, Johnson E, Ellis M, Stefana MI, Mendes CC, Wainwright SM, Cunningham C, Hamdy FC, Morris JF, Harris AL, Wilson C, Goberdhan DC. Glutamine deprivation alters the origin and function of cancer cell exosomes. EMBO J. 2020 Aug 17;39(16):e103009. doi: 10.15252/embj.2019103009. Epub 2020 Jul 28. PMID: 32720716; PMCID: PMC7429491.
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Posted:
5 October, 2020

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