Review Article, Jrgm Vol: 10 Issue: 3
Regenerative Exosomes: A Theragnostic Repository
1Department of Surgery, University of California Irvine, 333 City Blvd West, Suite 1600, Orange, CA 92868, USA
2Department of XO Stem Inc., 17252 Armstrong Ave, Suite A, Irvine, CA 92614, USA
3Department of Biomedical Engineering, University of California Irvine, 402 E Peltason Dr, Irvine, CA 92617, USA
- *Corresponding Author:
- Jonathan RT Lakey
Department of Surgery and Biomedical Engineering
University of California Irvine, California, USA
Tel: +1- 949-824-8022
Received: March 24, 2021 Accepted: April 14, 2021 Published: April 21, 2021
Citation: Rodriguez S, Alexander M, Taylor G, Sanderson J, Manzoli V, et al. (2021) Regenerative Exosomes: A Theragnostic Repository. J Regen Med 10:3.
Exosomes are recently discovered biological nanoparticles (50- 150 nm) that contain signaling cargo pertinent to paracrine cellular signalling within all tissue systems of the human body. Once thought of as cellular debris, exosomes have demonstrateda vast array of applications significant to both the medical and regenerative fields. These extracellular vesicles are secreted from cells as larger multivesicular bodies undergo exocytosis following endosomal processing. Exosome detection in bodily fluids during disease progression has demonstrated potential application as an early-detection disease biomarker. Furthermore, exosomes have been shown to upregulate regenerative effects, such as tissue repair and angiogenesis, in tissue microstructures. Due to the size and bioengineering versatility, exosomes have been the subject of extensive research into targeted drug and gene delivery system development. This minireview aims to characterize both the composition and reported functions of exosomes in addition to potential applications of this technology.
Keywords: Exosomes; Regeneration; Stem Cells; Therapy; Neovascularization; Bioengineering; Paracrine Signaling; Nanoparticle; Drug Delivery; Gene Delivery
Exosomes; Regeneration; Stem Cells;Therapy; Neovascularization; Bioengineering; Paracrine Signaling; Nanoparticle; Drug Delivery; Gene Delivery
MVB: Multivesicular Bodies, EV: Extracellular Vehicles, MSC: Mesenchymal Stem Cells, BBB: Blood Brain Barrier, EXO: Exosomes, VEGF: Vascular Endothelial Growth Factor, EXPLOR: Exosomes for Protein Delivery via Optically Reversible Protein-Protein Interactions.
Exosomes were originally observed 50 years ago when they were assumed to be the means by which cells disposed of waste products such as unneeded proteins and excess nucleic acids. The recognition of the true nature of what we now call exosomes came in the 1980’s, from studies on the loss of transferrin during the maturation of reticulocytes into erythrocytes [1,2]. In the past decade, interest in exosomes has exploded. There was a tenfold increase in publications from 2006 to 2015 and the PubMed search term “exosome” returns nearly 10,000 articles for the year 2018 . The pace and magnitude of exosome research continues to accelerate rapidly. Nonetheless, despite 20 years of research, the very basics of exosome biology are in their infancy and we know little of the part they play in normal cellular physiology, or their potential as therapeutic modalities. The objective of this mini review will be to elucidate on the characteristics and reported therapeutic applications of these extracellular vesicles.
Exosomes are roving packets of potent messenger molecules. Similar in mechanism to paracrine signaling utilizing growth factors and cytokines, exosomes are bioactive constituents of the secretome of the cell of origin . Exosomes are lipid-bilayer-enclosed biological nanoparticles with sizes ranging from 30 to 150 nm, about 1/1000th the size of the average cell . They are released into the extracellular space by most types of cells when intracellular multivesicular endosomes (MVE) fuse with the cell plasma membrane . They are found in many body fluids including serum, plasma, urine, cerebrospinal fluid, saliva, semen, milk, bile, ascites, and amniotic fluid [6,7]. Also similar to other bio-signals, they can be taken up and affect the behavior of nearby recipient cells or travel through the bloodstream to influence biologic responses of cells in distant organs . Exosomal cargo is mostly comprised of proteins and miRNAs, which represent a carefully selected fraction of those same molecules from their parent cells (Figure 1). In addition, the exosomal miRNAs, unlike cellular miRNAs, are highly enriched in pre-miRNAs, while the proteins are functionally clustered in several processes. Together, this selective composition of RNAs and proteins in exosomes demonstrates that exosome biogenesis is a highly regulated, and therefore an important, cellular process. Moreover, this exclusive RNA-protein composition continues to provide insights into various molecular targets for exosome-mediated functions.
Figure 1: Schematic of exosome biogenesis and its associated cargo. Exosomes are formed by budding of the endosomal membrane, forming multivesicular bodies (MVB). MVB then fuses with the plasma membrane, and releases exosomes into extracellular space. Exosome has a lipid shell, and contains proteins, miRNA, mRNA, and DNA. Surface markers CD9, CD63, and CD81 are characteristics of exosome. Reproduced from  under Creative Commons license.
Exosomes in Tissue Regeneration
Previous studies have demonstrated that the in vivo regenerative effects of stem cells are due to paracrine signaling via cytokines and growth factors that promotes tissue generation in the local environment [8-10]. Exosomes have been shown to play a similar role in this process through the intercellular transmission of protein and nucleic acid components which in turn initiate downstream effects in neighboring targeted cells [11,12]. In wound healing models, treatment with stem cell-derived exosomes have resulted in improvements in wound healing completion time, epithelial structure, and scarring reduction [13-15].These improvements are particularly important for wound healing in diabetic patients where these processes are strained by diabetes pathophysiology. Recent studies have described enhanced neovascularization in cardiac [16,17] and renal  tissue systems treated with exosomes isolated from umbilical cord derived mesenchymal stem cells (MSCs). Upregulation of functional proteins, such as Wnt4 and VEGF, have been shown to induce these downstream angiogenesis-promoting effects [19,20]. These regenerative capabilities have potential application to combat ischemia of transplanted tissue housed within bio-artificial devices.
Exosomes in Health & Disease
Containing cell-of-origin cytoplasmic contents including proteins, mRNAs, miRNAs, lipids and other macromolecules , the exosome cargo has the potential to affect targeted cellular functions in either healthy or pathological ways. Hence, exosomes are intrinsic to normal cellular communication and function , as well as being incriminated in the genesis and metastatic behavior of malignancies [22-25].
As essential messenger emissaries functioning throughout the body, they are attractive candidates as possible therapeutic envoys. For instance, because the blood brain barrier (BBB) prevents penetration of 98% of small molecule drugs, and exosomes have the ability to cross the BBB under inflammatory conditions, it may prove feasible to use exosomes in the treatment of neurological diseases and traumatic conditions [26,27]. This could have profound implications in treatments for Parkinson’s and Alzheimer’s diseases, and other neurologic maladies including stroke and traumatic injury. Indeed, recently published research, in which certain authors participated, demonstrates the value of mesenchymal stem cell-derived exosomes in treating a mouse model of multiple sclerosis [28,29].
Advances in Exosome Technology
The highly regulated cellular secretion of exosomes, including the specific composition of their cargo and cell-targeting specificity, are of immense biological interest. They have extremely high potential as non-invasive diagnostic biomarkers for many degenerative illnesses such as kidney disease [30,31], Alzheimer’s disease [32,33], Parkinson’s disease , and various types of cancer [35-37]. As biomarkers, they appear useful in evaluating normal and pathological biologic processes and monitoring the response to therapeutic intervention. Exosomes can thus provide insights on diagnosis, prognosis, regression or response to disease and disease treatments. Development of exosome- derived therapeutic nanocarriers for targeted drug and gene delivery have also been reported for numerous disease models [38-42]. The implications of these recent studies demonstrate the potential dual function to both diagnose and treat human diseases (Table 1).
Table 1: Utility of exosomes. This table summarizes the various utility of exosomes both as diagnostic markers and delivery of active molecules in clinical setting.
|Utility of exosome||References|
|Disease detection||[43, 44]|
|Renal cell cancer|||
|Central nervous system diseases|
|Stroke and traumatic injury|||
Once described as cellular debris, exosomes have been shown to have biologically intrinsic significance in cell communication and demonstrated versatility in functional application. Increased understanding of exosome physiology is poised to transform medical technology in myriad ways. In Table 1 we have provided examples of exosome uses for specific clinical indications. Exosome technology has potential to produce a new class of natural, functional, and cell-free drugs with both medical and regenerative relevance. Due to the infancy of the field, exosome research is projected to increase in popularity as more potential applications of this technology are discovered.
We greatly appreciate the support from the Department of Surgery at UC Irvine Medical Centre and University of California, Irvine and the Stem Cell Research Centre for the writing of this manuscript.
Conflict of interest statement: The authors declare no conflict of interest.
- Johnstone R, Bianchini A, Teng K, (1989) Reticulocyte maturation and exosome release: Transferrin receptor containing exosomes shows multiple plasma membrane functions. Blood 74: 1844-1851.
- Johnstone RM, Adam M, Hammond J, Orr L, Turbide C, (1987) Vesicle formation during reticulocyte maturation. Association of plasma membrane activities with released vesicles (exosomes). Journal of Biological Chemistry, 262: 9412-9420.
- United States National Institute of Health, (2019) Pubmed United States Library of Medicine.
- Bang C, Thum T, (2012) Exosomes: New players in cell–cell communication. The International Journal of Biochemistry & Cell Biology 44: 2060-2064.
- Kao CY, Papoutsakis ET, (2019) Extracellular vesicles: Exosomes, microparticles, their parts, and their targets to enable their biomanufacturing and clinical applications. Current Opinion in Biotechnology 60:89-98.
- Raposo G, Stoorvogel W, (2013) Extracellular vesicles: Exosomes, microvesicles, and friends. Journal of Cell Biology 200: 373-383
- Cappello F, Logozzi M, Campanella C, Bavisotto CC, Marcilla A, et al. (2017) Exosome levels in human body fluids: A tumor marker by themselves? European Journal of Pharmaceutical Sciences 96: 93-98.
- Hofer HR, Tuan RS, (2016) Secreted trophic factors of mesenchymal stem cells support neurovascular and musculoskeletal therapies. Stem Cell Research & Therapy 7: 131.
- Mirotsou M, Jayawardena TM, Schmeckpeper J, Gnecchi M, Dzau VJ. (2011) Paracrine mechanisms of stem cell reparative and regenerative actions in the heart. Journal of Molecular and Cellular Cardiology 50: 280-289.
- Hocking AM, Gibran NS, (2010) Mesenchymal stem cells: Paracrine signaling and differentiation during cutaneous wound repair. Experimental Cell Research 316: 2213-2219
- Zhang B, Yin Y, Lai RC, Tan SS, Choo ABH, et al. (2013) Mesenchymal stem cells secrete immunologically active exosomes. Stem Cells and Development 23:1233-1244.
- Li T, Yan Y, Wang B, Qian H, Zhang X, et al. (2012) Exosomes derived from human umbilical cord mesenchymal stem cells alleviate liver fibrosis. Stem Cells and Development 22: 845-854.
- Ribault A, Loinard C, Flamant S, Lim SK, Tamarat R. (2018) Human mesenchymal stromal cell-derived exosomes promote wound healing in a mouse model of radiation-induced injury. Journal of Extracellular Vesicles 7: 250.
- Vrijsen K, Sluijter J, Schuchardt M, Van Balkom B, Noort W, et al. (2010) Cardiomyocyte progenitor cell‐derived exosomes stimulate migration of endothelial cells. Journal of Cellular and Molecular Medicine 14: 1064-1070.
- Walter MN, Wright KT, Fuller HR, MacNeil S, Johnson WEB. (2010) Mesenchymal stem cell-conditioned medium accelerates skin wound healing: An in vitro study of fibroblast and keratinocyte scratch assays. Experimental Cell Research. 316: 1271-1281.
- Ma J, Zhao Y, Sun L, Sun X, Zhao X, et al. (2017) Exosomes derived from Akt‐modified human umbilical cord mesenchymal stem cells improve cardiac regeneration and promote angiogenesis via activating platelet‐derived growth factor D. Stem Cells Translational Medicine 6: 51-59.
- Zhao Y, Sun X, Cao W, Ma J, Sun L, et al. (2015) Exosomes derived from human umbilical cord mesenchymal stem cells relieve acute myocardial ischemic injury. Stem Cells International : 1-12.
- Zhou Y, Xu H, Xu W, Wang B, Wu H, et al. (2013) Exosomes released by human umbilical cord mesenchymal stem cells protect against cisplatin-induced renal oxidative stress and apoptosis in vivo and in vitro. Stem Cell Research & Therapy 4: 34.
- Zhang B, Wu X, Zhang X, Sun Y, Yan Y, et al. (2015) Human umbilical cord mesenchymal stem cell exosomes enhance angiogenesis through the Wnt4/β‐catenin pathway. Stem Cells Translational Medicine 4: 513-522.
- Gangadaran P, Rajendran RL, Lee HW, Kalimuthu S, Hong CM, et al. (2017) Extracellular vesicles from mesenchymal stem cells activates VEGF receptors and accelerates recovery of hindlimb ischemia. Journal of Controlled Release 264: 112-126
- Van Niel G, Porto-Carreiro I, Simoes S, Raposo G. (2006) Exosomes: A common pathway for a specialized function. Journal of Biochemistry 140:13-21.
- Lin R, Wang S, Zhao RC. (2013) Exosomes from human adipose-derived mesenchymal stem cells promote migration through Wnt signaling pathway in a breast cancer cell model. Molecular and Cellular Biochemistry 383: 13-20.
- Lehmann BD, Paine MS, Brooks AM, McCubrey JA, Renegar RH, et al. (2008) Senescence-associated exosome release from human prostate cancer cells. Cancer Research 68: 7864-7871.
- Boelens MC, Wu TJ, Nabet BY, Xu B, Qiu Y, et al. (2014) Exosome transfer from stromal to breast cancer cells regulates therapy resistance pathways. Cell 159: 499-513.
- Cho JA, Park H, Lim EH, Lee KW. (2012) Exosomes from breast cancer cells can convert adipose tissue-derived mesenchymal stem cells into myofibroblast-like cells. International Journal of Oncology 40: 130-138.
- Chen CC, Liu L, Ma F, Wong CW, Guo XE, et al. 2016. Elucidation of exosome migration across the blood–brain barrier model in vitro. Cellular and Molecular Bioengineering 9: 509-529.
- Bullock K, Sharma P, Whiteside T, Banks W. (2019) Abstract# 2057 inflammation and blood-to-brain transport of tumor-derived exosomes. Brain, Behavior, and Immunity 76: 5.
- Shamili FH, Alibolandi M, Rafatpanah H, Abnous K, Mahmoudi M, et al. (2019) Immunomodulatory properties of MSC-derived exosomes armed with high affinity aptamer toward mylein as a platform for reducing multiple sclerosis clinical score. Journal of Controlled Release 299: 149-164.
- Riazifar M, Mohammadi MR, Pone EJ, Yeri A, Lässer C, et al. (2019) Stem cell-derived exosomes as nanotherapeutics for autoimmune and neurodegenerative disorders. ACS Nano 13: 6670-6688.
- Alvarez ML, Khosroheidari M, Ravi RK, DiStefano JK. (2012) Comparison of protein, microrna, and mrna yields using different methods of urinary exosome isolation for the discovery of kidney disease biomarkers. Kidney International 82:1024-1032.
- Khurana R, Ranches G, Schafferer S, Lukasser M, Rudnicki M, et al. (2017) Identification of urinary exosomal noncoding RNAs as novel biomarkers in chronic kidney disease. RNA 23:142-152.
- Hamlett ED, Goetzl EJ, Ledreux A, Vasilevko V, Boger HA, et al. (2017) Neuronal exosomes reveal alzheimer's disease biomarkers in down syndrome. Alzheimer's & Dementia 13: 541-549.
- Mullins RJ, Mustapic M, Goetzl EJ, Kapogiannis D. (2017) Exosomal biomarkers of brain insulin resistance associated with regional atrophy in alzheimer's disease. Human Brain Mapping 38: 1933-1940.
- Fraser KB, Rawlins AB, Clark RG, Alcalay RN, Standaert DG, et al. (2016) Ser (P)‐1292 LRRK2 in urinary exosomes is elevated in idiopathic Parkinson's disease. Movement Disorders 31: 1543-1550.
- Liu Q, Yu Z, Yuan S, Xie W, Li C, et al. (2017) Circulating exosomal micrornas as prognostic biomarkers for non-small-cell lung cancer. Oncotarget 8:13048.
- Skotland T, Ekroos K, Kauhanen D, Simolin H, Seierstad T, et al. (2017) Molecular lipid species in urinary exosomes as potential prostate cancer biomarkers. European Journal of Cancer 70: 122-132.
- Hannafon BN, Trigoso YD, Calloway CL, Zhao YD, Lum DH, et al. (2016) Plasma exosome microRNAs are indicative of breast cancer. Breast Cancer Research 18: 90.
- Tian T, Zhang H-X, He C-P, Fan S, Zhu Y-L,et al. (2018) Surface functionalized exosomes as targeted drug delivery vehicles for cerebral ischemia therapy. Biomaterials 150: 137-149.
- Vader P, Mol EA, Pasterkamp G, Schiffelers RM. (2016) Extracellular vesicles for drug delivery. Advanced Drug Delivery Reviews 106:148-156.
- Yang J, Zhang X, Chen X, Wang L, Yang G. (2017) Exosome mediated delivery of mir-124 promotes neurogenesis after ischemia. Molecular Therapy-Nucleic Acids 7: 278-287.
- Luan X, Sansanaphongpricha K, Myers I, Chen H, Yuan H, et al. (2017) Engineering exosomes as refined biological nanoplatforms for drug delivery. Acta Pharmacologica Sinica 38(6): 754.
- Yim N, Ryu S-W, Choi K, Lee KR, Lee S, et al. (2016) Exosome engineering for efficient intracellular delivery of soluble proteins using optically reversible protein–protein interaction module. Nature Communications 7: 12277.
- Zhou B, Xu K, Zheng X, Chen T, Wang J, Song Y, Shao Y, Zheng S. (2020) Application of exosomes as liquid biopsy in clinical diagnosis. Signal Transduct Target Ther. 5(1):144.
- Pinzani P, Argenio V, Del Re M, Pellegrini C, Cucchiara F, et al. (2021) Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors. Clin Chem Lab Med. Online ahead of print.
- Alimirzaie S, Bagherzadeh M, Akbari MR. (2019) Liquid biopsy in breast cancer: A comprehensive review. Clin Genet. 95(6): 643-660.
- Sandfeld-Paulsen B, Jakobsen KR, Bæk R, Folkersen BH, Rasmussen TR, et al. (2016) Exosomal Proteins as Diagnostic Biomarkers in Lung Cancer. Journal of Thoracic Oncology 11: 1701-1710.
- Lorenc T, Klimczyk K, Michalczewska I, Slomka M, Kubiak-Tomaxzewsha G, et al. (2020) Exosomes in Prostate Cancer Diagnosis, Prognosis and Therapy. Int J Mol Sci. 19;21(6): 2118.
- Hosseini M, Khatamianfar S, Hassanian SM, Nedaeinia R, Shafiee M, et al. (2017) Exosome-Encapsulated microRNAs as Potential Circulating Biomarkers in Colon Cancer. Curr Pharm Des. 23(11): 1705-1709
- Gowda R, Robertson BM, Iyer S, Barry J, Dinavahi SS, Robertson GP. (2020)
- Elsharkawi F, Slsabah M, Shabayek M, Khaled H. (2019) Urine and Serum Exosomes as Novel Biomarkers in Detection of Bladder Cancer. Asian Pac J Cancer Prev. 20(7): 2219-2224.
- Ofori K, Bhagat G, Rai AJ. (2021) Exosomes and extracellular vesicles as liquid biopsy biomarkers in diffuse large B-cell lymphoma: Current state of the art and unmet clinical needs. Br J Clin Pharmacol. 87(2): 284-294.
- Grange C, Brossa A, Bussolati B. (2019) Extracellular vesicles and carried miRNAs in the progression of renal cell carcinoma. Int J Mol Sci. 20(8): 1832.
- Srivastava A, Moxley K, Ruskin R, Dhanasekaran DN, Zhao YD, Ramesh R. (2018) A non-invasive liquid biopsy screening of urine-derived exosomes for miRNAs as Biomarkers in endometrial cancer patients. AAPS J. 20(5): 82.
- Deng W, Wang L, Pan M, Zheng J. (2020) The regulatory role of exosomes in leukemia and their clinical significance. J Int Med Res. 48(8).
- Lan B, Zeng S, Grützmann R, Pilarsky C. (2019) The role of exosomes in pancreatic cancer. Int J Mol Sci 20(18): 4332.
- Feng K, Ma R, Zhang L, Li H, Tang Y, et al. (2020) The Role of Exosomes in Thyroid Cancer and Their Potential Clinical Application. Front Oncol. 10: 596132.
- Shu T, Wang Y, Jin H, Li L. (2019) The role of exosomes in autoimmune connective tissue disease. Ann Med. 51(2): 101-108.
- Zhao T, Sun F, Liu J, Ding T, She J, et al. (2019) Emerging role of mesenchymal stem cell-derived exosomes in regenerative medicine. Curr Stem Cell Res Ther. 14(6): 482-494.
- Console L, Scalise M, Indiveri C. (2019) Exosomes in inflammation and role as biomarkers. Clin Chim Acta. 488: 165-171.
- Hu P, Yang Q, Wang Q, Shi C, Wang D, et al. (2019) Mesenchymal stromal cells-exosomes: a promising cell-free therapeutic tool for wound healing and cutaneous regeneration. Burns Trauma 26 (7):38.
- Porro C, Panaro MA, Lofrumento DD, Hasalla E, Trotta T. (2019) The multiple roles of exosomes in Parkinson’s disease: an overview. Immunopharmacol Immunotoxicol 41(4): 469-476.
- Jiang L, Dong H, Cao H, Ji X, Luan S, Liu J. (2019) Exosomes in pathogenesis, diagnosis, and treatment of Alzheimer’s disease. Med Sci Monit. 6(25): 3329-3335.
- Zhang ZG, Buller B, Chopp M. (2019) Exosomes-beyond stem cells for restorative therapy in stroke and neurological injury. Nat Rev Neurol. 15(4):193-203.
- Melzer C, Rehn V, Yang Y, Bähre H, von der Ohe J, Hass R. (2019) Taxol-Loaded MSC-Derived Exosomes Provide a Therapeutic Vehicle to Target Metastatic Breast Cancer and Other Carcinoma Cells. Cancers (Basel). 11(6): 798.
- Farugu FN, Xu L, Al-Jamal KT. (2018) Preparation of Exosomes for siRNA Delivery to Cancer Cells. J Vis Exp. 142(10): 3791-58814.
- Hofmann L, Ludwig S, Vahl JM, Brunner C, Hoffmann TK, et al. (2020) The Emerging Role of Exosomes in Diagnosis, Prognosis, and Therapy in Head and Neck Cancer. Int J Mol Sci. 21(11):4072.