Exosomes—the enigmatic regulators of bone homeostasis

Abstract

Exosomes are a heterogeneous group of cell-derived membranous structures, which mediate crosstalk interaction between cells. Recent studies have revealed a close relationship between exosomes and bone homeostasis. It is suggested that bone cells can spontaneously secret exosomes containing proteins, lipids and nucleic acids, which then to regulate osteoclastogenesis and osteogenesis. However, the network of regulatory activities of exosomes in bone homeostasis as well as their therapeutic potential in bone injury remain largely unknown. This review will detail and discuss the characteristics of exosomes, the regulatory activities of exosomes in bone homeostasis as well as the clinical potential of exosomes in bone injury.

Development: Exosomes guide bone development and offer clinical promise

Vesicles known as exosomes may prove to be valuable clinical tools once their function is clarified. Exosomes were discovered in the 1980s but not observed in bone tissue until 2003. Minghao Zheng of the University of Western Australia, together with colleagues elsewhere, has reviewed the biology of exosomes, their role in maintaining bones, and their potential clinical uses. Exosomes carry lipids, proteins, and nucleic acids between cells. They are released by every type of bone cell, with the role of each exosome determined by its specific contents. Exosome-mediated crosstalk is involved in regulating bone remodeling, and exosomes have also been implicated in myelomas. Recent work has shown that exosome treatment can improve fracture healing. The authors conclude that a better understanding of the role of exosomes in bone homeostasis will unlock their significant clinical potential.

References

[1] Cappariello A, Maurizi A, Veeriah V, Teti A. The great beauty of the osteoclast. Arch. Biochem. Biophys., 2014, 558:70-78

[2] Capulli M, Paone R, Rucci N. Osteoblast and osteocyte: games without frontiers. Arch. Biochem. Biophys., 2014, 561:3-12

[3] Compton JT, Lee FY. A review of osteocyte function and the emerging importance of sclerostin. J. Bone Jt. Surg. Am., 2014, 96:1659-1668

[4] Kennedy OD et al. Activation of resorption in fatigue-loaded bone involves both apoptosis and active pro-osteoclastogenic signaling by distinct osteocyte populations. Bone, 2012, 50:1115-22 1115-cell 1122

[5] Graves DT, Jiang Y, Valente AJ. The expression of monocyte chemoattractant protein-1 and other chemokines by osteoblasts. Front. Biosci., 1999, 4:D571-D580

[6] Lacey DL et al. Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell, 1998, 93:165-176

[7] Nakagawa N et al. RANK is the essential signaling receptor for osteoclast differentiation factor in osteoclastogenesis. Biochem. Biophys. Res. Commun., 1998, 253:395-400

[8] Yoshida H et al. The murine mutation osteopetrosis is in the coding region of the macrophage colony stimulating factor gene. Nature, 1990, 345:442-444

[9] Martin TJ, Sims NA. Osteoclast-derived activity in the coupling of bone formation to resorption. Trends Mol. Med., 2005, 11:76-81

[10] Raggatt LJ, Partridge NC. Cellular and molecular mechanisms of bone remodeling. J. Biol. Chem., 2010, 285:25103-25108

[11] Thery C, Ostrowski M, Segura E. Membrane vesicles as conveyors of immune responses. Nat. Rev. Immunol., 2009, 9:581-593

[12] Tricarico C, Clancy J, D’Souza-Schorey C. Biology and biogenesis of shed microvesicles. Small GTPases, 2017, 8:220-232

[13] Ponpuak M et al. Secretory autophagy. Curr. Opin. Cell Biol., 2015, 35:106-116

[14] Frazer AC, Stewart HC. Ultramicroscopic particles in normal human blood. J. Physiol., 1937, 90:18-30

[15] Barland P, Novikoff AB, Hamerman D. Electron microscopy of the human synovial membrane. J. Cell Biol., 1962, 14:207-220

[16] Anderson HC. Vesicles associated with calcification in the matrix of epiphyseal cartilage. J. Cell Biol., 1969, 41:59-72

[17] Dalton AJ. Microvesicles and vesicles of multivesicular bodies versus “virus-like” particles. J. Natl Cancer Inst., 1975, 54:1137-1148

[18] Trams EG, Lauter CJ, Salem N Jr., Heine U. Exfoliation of membrane ecto-enzymes in the form of micro-vesicles. Biochim Biophys. Acta, 1981, 645:63-70

[19] Harding C, Heuser J, Stahl P. Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes. J. Cell Biol., 1983, 97:329-339

[20] Pan BT, Teng K, Wu C, Adam M, Johnstone RM. Electron microscopic evidence for externalization of the transferrin receptor in vesicular form in sheep reticulocytes. J. Cell Biol., 1985, 101:942-948

[21] Johnstone RM, Adam M, Hammond JR, Orr L, Turbide C. Vesicle formation during reticulocyte maturation. J. Biol. Chem., 1987, 262:9412-9420

[22] Raposo G et al. B lymphocytes secrete antigen-presenting vesicles. J. Exp. Med., 1996, 183:1161-1172

[23] Zitvogel L et al. Eradication of established murine tumors using a novel cell-free vaccine: dendritic cell-derived exosomes. Nat. Med., 1998, 4:594-600

[24] Wolfers J et al. Tumor-derived exosomes are a source of shared tumor rejection antigens for CTL cross-priming. Nat. Med., 2001, 7:297-303

[25] Lai RC, Yeo RW, Tan KH, Lim SK. Exosomes for drug delivery - a novel application for the mesenchymal stem cell. Biotechnol. Adv., 2013, 31:543-551

[26] Bobrie A, Colombo M, Raposo G, Thery C. Exosome secretion: molecular mechanisms and roles in immune responses. Traffic, 2011, 12:1659-1668

[27] Lo Cicero A, Stahl PD, Raposo G. Extracellular vesicles shuffling intercellular messages: for good or for bad. Curr. Opin. Cell Biol., 2015, 35:69-77

[28] Hoshino D et al. Exosome secretion is enhanced by invadopodia and drives invasive behavior. Cell Rep., 2013, 5:1159-1168

[29] Gasser O, Schifferli JA. Activated polymorphonuclear neutrophils disseminate anti-inflammatory microparticles by ectocytosis. Blood, 2004, 104:2543-2548

[30] Bernier GM, Duca VD Jr, Brereton R, Graham RC Jr. Multiple myeloma with intramedullary masses of M-component. Blood, 1975, 46:931-935

[31] Bab IA, Muhlrad A, Sela J. Ultrastructural and biochemical study of extracellular matrix vesicles in normal alveolar bone of rats. Cell Tissue Res., 1979, 202:1-7

[32] Ornoy A, Atkin I, Levy J. Ultrastructural studies on the origin and structure of matrix vesicles in bone of young rats. Acta Anat. (Basel), 1980, 106:450-461

[33] Peche H, Heslan M, Usal C, Amigorena S, Cuturi MC. Presentation of donor major histocompatibility complex antigens by bone marrow dendritic cell-derived exosomes modulates allograft rejection. Transplantation, 2003, 76:1503-1510

[34] Ekstrom K et al. Monocyte exosomes stimulate the osteogenic gene expression of mesenchymal stem cells. PLoS ONE, 2013, 8:e75227

[35] Ge M, Ke R, Cai T, Yang J, Mu X. Identification and proteomic analysis of osteoblast-derived exosomes. Biochem. Biophys. Res. Commun., 2015, 467:27-32

[36] Li D et al. Osteoclast-derived exosomal miR-214-3p inhibits osteoblastic bone formation. Nat. Commun., 2016, 7

[37] Sato M, Suzuki T, Kawano M, Tamura M. Circulating osteocyte-derived exosomes contain miRNAs which are enriched in exosomes from MLO-Y4 cells. Biomed. Rep., 2017, 6:223-231

[38] Villarroya-Beltri C, Baixauli F, Gutierrez-Vazquez C, Sanchez-Madrid F, Mittelbrunn M. Sorting it out: regulation of exosome loading. Semin. Cancer Biol., 2014, 28:3-13

[39] Mathivanan S, Ji H, Simpson RJ. Exosomes: extracellular organelles important in intercellular communication. J. Proteom., 2010, 73:1907-1920

[40] Kalra H et al. Vesiclepedia: a compendium for extracellular vesicles with continuous community annotation. PLoS Biol., 2012, 10:e1001450

[41] Lydic TA et al. Rapid and comprehensive ‘shotgun’ lipidome profiling of colorectal cancer cell derived exosomes. Methods, 2015, 87:83-95

[42] Mobius W et al. Recycling compartments and the internal vesicles of multivesicular bodies harbor most of the cholesterol found in the endocytic pathway. Traffic, 2003, 4:222-231

[43] van Meer G, Voelker DR, Feigenson GW. Membrane lipids: where they are and how they behave. Nat. Rev. Mol. Cell Biol., 2008, 9:112-124

[44] Moser von Filseck J et al. Intracellular transport. Phosphatidylserine transport by ORP/Osh proteins is driven by phosphatidylinositol 4-phosphate. Science, 2015, 349:432-436

[45] Brouwers JF et al. Distinct lipid compositions of two types of human prostasomes. Proteomics, 2013, 13:1660-1666

[46] Simons K, Toomre D. Lipid rafts and signal transduction. Nat. Rev. Mol. Cell Biol., 2000, 1:31-39

[47] Luberto C, Hannun YA. Sphingomyelin synthase, a potential regulator of intracellular levels of ceramide and diacylglycerol during SV40 transformation. Does sphingomyelin synthase account for the putative phosphatidylcholine-specific phospholipase C? J. Biol. Chem., 1998, 273:14550-14559

[48] Kosaka N et al. Neutral sphingomyelinase 2 (nSMase2)-dependent exosomal transfer of angiogenic microRNAs regulate cancer cell metastasis. J. Biol. Chem., 2013, 288:10849-10859

[49] Theos AC et al. A lumenal domain-dependent pathway for sorting to intralumenal vesicles of multivesicular endosomes involved in organelle morphogenesis. Dev. Cell, 2006, 10:343-354

[50] Trajkovic K et al. Ceramide triggers budding of exosome vesicles into multivesicular endosomes. Science, 2008, 319:1244-1247

[51] Yuyama K, Sun H, Mitsutake S, Igarashi Y. Sphingolipid-modulated exosome secretion promotes clearance of amyloid-beta by microglia. J. Biol. Chem., 2012, 287:10977-10989

[52] Keerthikumar S et al. ExoCarta: A Web-Based Compendium of Exosomal Cargo. J. Mol. Biol., 2016, 428:688-692

[53] Takeuchi T et al. Intercellular chaperone transmission via exosomes contributes to maintenance of protein homeostasis at the organismal level. Proc. Natl Acad. Sci. USA, 2015, 112:E2497-E2506

[54] Henne WM, Buchkovich NJ, Emr SD. The ESCRT pathway. Dev. Cell, 2011, 21:77-91

[55] Keryer-Bibens C et al. Exosomes released by EBV-infected nasopharyngeal carcinoma cells convey the viral latent membrane protein 1 and the immunomodulatory protein galectin 9. BMC Cancer, 2006, 6

[56] Melo SA et al. Glypican-1 identifies cancer exosomes and detects early pancreatic cancer. Nature, 2015, 523:177-182

[57] Valadi H et al. Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat. Cell Biol., 2007, 9:654-659

[58] Thakur BK et al. Double-stranded DNA in exosomes: a novel biomarker in cancer detection. Cell Res., 2014, 24:766-769

[59] Li SP, Lin ZX, Jiang XY, Yu XY. Exosomal cargo-loading and synthetic exosome-mimics as potential therapeutic tools. Acta Pharmacol. Sin., 2018, 39:542-551

[60] Januszyk K, Lima CD. The eukaryotic RNA exosome. Curr. Opin. Struct. Biol., 2014, 24:132-140

[61] Lv LL et al. CD2AP mRNA in urinary exosome as biomarker of kidney disease. Clin. Chim. Acta, 2014, 428:26-31

[62] Shao H et al. Chip-based analysis of exosomal mRNA mediating drug resistance in glioblastoma. Nat. Commun., 2015, 6

[63] Liu R, Liu J, Ji X, Liu Y. Synthetic nucleic acids delivered by exosomes: a potential therapeutic for generelated metabolic brain diseases. Metab. Brain Dis., 2013, 28:551-562

[64] Mittelbrunn M et al. Unidirectional transfer of microRNA-loaded exosomes from T cells to antigen-presenting cells. Nat. Commun., 2011, 2

[65] Luo SS et al. Human villous trophoblasts express and secrete placenta-specific microRNAs into maternal circulation via exosomes. Biol. Reprod., 2009, 81:717-729

[66] Liu, H. et al. Tumor-derived exosomes promote tumor self-seeding in hepatocellular carcinoma by transferring miRNA-25-5p to enhance cell motility. Oncogene: https://doi.org/10.1038/s41388-018-0309-x (2018).

[67] Wang J et al. Bone marrow stromal cell-derived exosomes as communicators in drug resistance in multiple myeloma cells. Blood, 2014, 124:555-566

[68] Takahashi A et al. Exosomes maintain cellular homeostasis by excreting harmful DNA from cells. Nat. Commun., 2017, 8

[69] Hoeijmakers JH. DNA damage, aging, and cancer. N. Engl. J. Med., 2009, 361:1475-1485

[70] Kahlert C et al. Identification of double-stranded genomic DNA spanning all chromosomes with mutated KRAS and p53 DNA in the serum exosomes of patients with pancreatic cancer. J. Biol. Chem., 2014, 289:3869-3875

[71] Kalluri R, LeBleu VS. Discovery of Double-Stranded Genomic DNA in Circulating Exosomes. Cold Spring Harb. Symp. Quant. Biol., 2016, 81:275-280

[72] Raiborg C, Stenmark H. The ESCRT machinery in endosomal sorting of ubiquitylated membrane proteins. Nature, 2009, 458:445-452

[73] Svensson KJ et al. Exosome uptake depends on ERK1/2-heat shock protein 27 signaling and lipid Raft-mediated endocytosis negatively regulated by caveolin-1. J. Biol. Chem., 2013, 288:17713-17724

[74] van Niel G, D’Angelo G, Raposo G. Shedding light on the cell biology of extracellular vesicles. Nat. Rev. Mol. Cell Biol., 2018, 19:213-228

[75] Henne, W. M., Stenmark, H. & Emr, S. D. Molecular mechanisms of the membrane sculpting ESCRT pathway. Cold Spring Harb. Perspect. Biol. 5, https://doi.org/10.1101/cshperspect.a016766 (2013).

[76] Stoorvogel W. Resolving sorting mechanisms into exosomes. Cell Res., 2015, 25:531-532

[77] Colombo M et al. Analysis of ESCRT functions in exosome biogenesis, composition and secretion highlights the heterogeneity of extracellular vesicles. J. Cell Sci., 2013, 126:5553-5565

[78] Baietti MF et al. Syndecan-syntenin-ALIX regulates the biogenesis of exosomes. Nat. Cell Biol., 2012, 14:677-685

[79] Ramani VC, Pruett PS, Thompson CA, DeLucas LD, Sanderson RD. Heparan sulfate chains of syndecan-1 regulate ectodomain shedding. J. Biol. Chem., 2012, 287:9952-9961

[80] Roucourt B, Meeussen S, Bao J, Zimmermann P, David G. Heparanase activates the syndecan-syntenin-ALIX exosome pathway. Cell Res., 2015, 25:412-428

[81] Charrin S, Jouannet S, Boucheix C, Rubinstein E. Tetraspanins at a glance. J. Cell Sci., 2014, 127:3641-3648

[82] van Niel G et al. The tetraspanin CD63 regulates ESCRT-independent and -dependent endosomal sorting during melanogenesis. Dev. Cell, 2011, 21:708-721

[83] Zimmerman B et al. Crystal structure of a full-length human tetraspanin reveals a cholesterol-binding pocket. Cell, 2016, 167:1041-1051 e1011

[84] Janas T, Janas MM, Sapon K, Janas T. Mechanisms of RNA loading into exosomes. FEBS Lett., 2015, 589:1391-1398

[85] Wu BX et al. Identification of novel anionic phospholipid binding domains in neutral sphingomyelinase 2 with selective binding preference. J. Biol. Chem., 2011, 286:22362-22371

[86] Record M, Carayon K, Poirot M, Silvente-Poirot S. Exosomes as new vesicular lipid transporters involved in cell-cell communication and various pathophysiologies. Biochim. Biophys. Acta, 2014, 1841:108-120

[87] Kosaka N et al. Secretory mechanisms and intercellular transfer of microRNAs in living cells. J. Biol. Chem., 2010, 285:17442-17452

[88] Janas T, Janas T, Yarus M. Specific RNA binding to ordered phospholipid bilayers. Nucleic Acids Res., 2006, 34:2128-2136

[89] Kozlov MM, Chernomordik LV. Membrane tension and membrane fusion. Curr. Opin. Struct. Biol., 2015, 33:61-67

[90] Savina A, Fader CM, Damiani MT, Colombo MI. Rab11 promotes docking and fusion of multivesicular bodies in a calcium-dependent manner. Traffic, 2005, 6:131-143

[91] Wei Y et al. Pyruvate kinase type M2 promotes tumour cell exosome release via phosphorylating synaptosome-associated protein 23. Nat. Commun., 2017, 8

[92] Colombo M, Raposo G, Thery C. Biogenesis, secretion, and intercellular interactions of exosomes and other extracellular vesicles. Annu. Rev. Cell. Dev. Biol., 2014, 30:255-289

[93] Fruhbeis C, Frohlich D, Kuo WP, Kramer-Albers EM. Extracellular vesicles as mediators of neuron-glia communication. Front. Cell. Neurosci., 2013, 7:182

[94] Ostrowski M et al. Rab27a and Rab27b control different steps of the exosome secretion pathway. Nat. Cell Biol., 2010, 12:19-30 sup pp 11-13

[95] Kowal J, Tkach M, Thery C. Biogenesis and secretion of exosomes. Curr. Opin. Cell Biol., 2014, 29:116-125

[96] Christianson HC, Svensson KJ, van Kuppevelt TH, Li JP, Belting M. Cancer cell exosomes depend on cell-surface heparan sulfate proteoglycans for their internalization and functional activity. Proc. Natl Acad. Sci. USA, 2013, 110:17380-17385

[97] Cocucci E, Racchetti G, Meldolesi J. Shedding microvesicles: artefacts no more. Trends Cell Biol., 2009, 19:43-51

[98] Keller S et al. Systemic presence and tumor-growth promoting effect of ovarian carcinoma released exosomes. Cancer Lett., 2009, 278:73-81

[99] Mulcahy, L. A., Pink, R. C. & Carter, D. R. Routes and mechanisms of extracellular vesicle uptake. J. Extracell. Vesicles 3, https://doi.org/10.3402/jev.v3.24641 (2014).

[100] Feng D et al. Cellular internalization of exosomes occurs through phagocytosis. Traffic, 2010, 11:675-687

[101] Boscher C, Nabi IR. Caveolin-1: role in cell signaling. Adv. Exp. Med. Biol., 2012, 729:29-50

[102] Kirchhausen T. Clathrin. Annu. Rev. Biochem., 2000, 69:699-727

[103] Tian T et al. Exosome uptake through clathrin-mediated endocytosis and macropinocytosis and mediating miR-21 delivery. J. Biol. Chem., 2014, 289:22258-22267

[104] Swanson JA. Shaping cups into phagosomes and macropinosomes. Nat. Rev. Mol. Cell Biol., 2008, 9:639-649

[105] Parolini I et al. Microenvironmental pH is a key factor for exosome traffic in tumor cells. J. Biol. Chem., 2009, 284:34211-34222

[106] Chernomordik LV, Kozlov MM. Mechanics of membrane fusion. Nat. Struct. Mol. Biol., 2008, 15:675-683

[107] Chernomordik LV, Kozlov MM. Protein-lipid interplay in fusion and fission of biological membranes. Annu. Rev. Biochem., 2003, 72:175-207

[108] Kozlov MM, Markin VS. [Possible mechanism of membrane fusion]. Biofizika, 1983, 28:242-247

[109] Kozlov MM, Leikin SL, Chernomordik LV, Markin VS, Chizmadzhev YA. Stalk mechanism of vesicle fusion. Eur. Biophys. J., 1989, 17:121-129

[110] Helfrich MH et al. Beta 1 integrins and osteoclast function: involvement in collagen recognition and bone resorption. Bone, 1996, 19:317-328

[111] Crockett JC, Mellis DJ, Scott DI, Helfrich MH. New knowledge on critical osteoclast formation and activation pathways from study of rare genetic diseases of osteoclasts: focus on the RANK/RANKL axis. Osteoporos. Int., 2011, 22:1-20

[112] Li J et al. Exosomes mediate the cell-to-cell transmission of IFN-alpha-induced antiviral activity. Nat. Immunol., 2013, 14:793-803

[113] Cui Y, Luan J, Li H, Zhou X, Han J. Exosomes derived from mineralizing osteoblasts promote ST2 cell osteogenic differentiation by alteration of microRNA expression. FEBS Lett., 2016, 590:185-192

[114] Furuta T et al. Mesenchymal stem cell-derived exosomes promote fracture healing in a mouse model. Stem Cells Transl. Med., 2016, 5:1620-1630

[115] Qin Y, Wang L, Gao Z, Chen G, Zhang C. Bone marrow stromal/stem cell-derived extracellular vesicles regulate osteoblast activity and differentiation in vitro and promote bone regeneration in vivo. Sci. Rep., 2016, 6

[116] Zhao P, Xiao L, Peng J, Qian YQ, Huang CC. Exosomes derived from bone marrow mesenchymal stem cells improve osteoporosis through promoting osteoblast proliferation via MAPK pathway. Eur. Rev. Med. Pharmacol. Sci., 2018, 22:3962-3970

[117] Wei J et al. let-7 enhances osteogenesis and bone formation while repressing adipogenesis of human stromal/mesenchymal stem cells by regulating HMGA2. Stem. Cells Dev., 2014, 23:1452-1463

[118] Wang X et al. miR-214 targets ATF4 to inhibit bone formation. Nat. Med., 2013, 19:93-100

[119] Sun W et al. Osteoclast-derived microRNA-containing exosomes selectively inhibit osteoblast activity. Cell Discov., 2016, 2:16015

[120] Deng L et al. Osteoblast-derived microvesicles: a novel mechanism for communication between osteoblasts and osteoclasts. Bone, 2015, 79:37-42

[121] Huynh N et al. Characterization of regulatory extracellular vesicles from osteoclasts. J. Dent. Res., 2016, 95:673-679

[122] Chen C et al. MiR-503 regulates osteoclastogenesis via targeting RANK. J. Bone Miner. Res., 2014, 29:338-347

[123] Xie Y, Chen Y, Zhang L, Ge W, Tang P. The roles of bone-derived exosomes and exosomal microRNAs in regulating bone remodelling. J. Cell. Mol. Med., 2017, 21:1033-1041

[124] Xie Y et al. Involvement of serum-derived exosomes of elderly patients with bone loss in failure of bone remodeling via alteration of exosomal bone-related proteins. Aging Cell, 2018, 17:e12758

[125] Cappariello A et al. Osteoblast-derived extracellular vesicles are biological tools for the delivery of active molecules to bone. J. Bone Miner. Res., 2018, 33:517-533

[126] Qin Y et al. Myostatin inhibits osteoblastic differentiation by suppressing osteocyte-derived exosomal microRNA-218: a novel mechanism in muscle-bone communication. J. Biol. Chem., 2017, 292:11021-11033

[127] Bonewald LF. The amazing osteocyte. J. Bone Miner. Res., 2011, 26:229-238

[128] Kramer I et al. Osteocyte Wnt/beta-catenin signaling is required for normal bone homeostasis. Mol. Cell. Biol., 2010, 30:3071-3085

[129] Lu XL, Huo B, Park M, Guo XE. Calcium response in osteocytic networks under steady and oscillatory fluid flow. Bone, 2012, 51:466-473

[130] Raimondi L et al. Involvement of multiple myeloma cell-derived exosomes in osteoclast differentiation. Oncotarget, 2015, 6:13772-13789

[131] Ye Y et al. Exosomal miR-141-3p regulates osteoblast activity to promote the osteoblastic metastasis of prostate cancer. Oncotarget, 2017, 8:94834-94849

[132] Mundy GR. Metastasis to bone: causes, consequences and therapeutic opportunities. Nat. Rev. Cancer, 2002, 2:584-593

[133] Guise TA et al. Evidence for a causal role of parathyroid hormone-related protein in the pathogenesis of human breast cancer-mediated osteolysis. J. Clin. Invest., 1996, 98:1544-1549

[134] Valencia K et al. miRNA cargo within exosome-like vesicle transfer influences metastatic bone colonization. Mol. Oncol., 2014, 8:689-703

[135] Claes L, Recknagel S, Ignatius A. Fracture healing under healthy and inflammatory conditions. Nat. Rev. Rheumatol., 2012, 8:133-143

[136] Grundnes O, Reikeraas O. Effects of macrophage activation on bone healing. J. Orthop. Sci., 2000, 5:243-247

[137] Yu B, Zhang X, Li X. Exosomes derived from mesenchymal stem cells. Int. J. Mol. Sci., 2014, 15:4142-4157

[138] Schmidt-Bleek K et al. Inflammatory phase of bone healing initiates the regenerative healing cascade. Cell Tissue Res., 2012, 347:567-573

[139] Chen W et al. Immunomodulatory effects of mesenchymal stromal cells-derived exosome. Immunol. Res., 2016, 64:831-840

[140] Kolar P et al. The early fracture hematoma and its potential role in fracture healing. Tissue Eng. Part B Rev., 2010, 16:427-434

[141] Ismail N et al. Macrophage microvesicles induce macrophage differentiation and miR-223 transfer. Blood, 2013, 121:984-995

[142] Anderson JD et al. Comprehensive proteomic analysis of mesenchymal stem cell exosomes reveals modulation of angiogenesis via nuclear factor-kappaB signaling. Stem Cells, 2016, 34:601-613

[143] Salomon C et al. Exosomal signaling during hypoxia mediates microvascular endothelial cell migration and vasculogenesis. PLoS ONE, 2013, 8:e68451

[144] Shabbir A, Cox A, Rodriguez-Menocal L, Salgado M, Van Badiavas E. Mesenchymal stem cell exosomes induce proliferation and migration of normal and chronic wound fibroblasts, and enhance angiogenesis in vitro. Stem. Cells Dev., 2015, 24:1635-1647

[145] Qi X et al. Exosomes secreted by human-induced pluripotent stem cell-derived mesenchymal stem cells repair critical-sized bone defects through enhanced angiogenesis and osteogenesis in osteoporotic rats. Int. J. Biol. Sci., 2016, 12:836-849

[146] Narayanan R, Huang CC, Ravindran S. Hijacking the cellular mail: exosome mediated differentiation of mesenchymal stem cells. Stem Cells Int., 2016, 2016:3808674

[147] De Jong OG, Van Balkom BW, Schiffelers RM, Bouten CV, Verhaar MC. Extracellular vesicles: potential roles in regenerative medicine. Front. Immunol., 2014, 5:608

[148] Ferreira E, Porter RM. Harnessing extracellular vesicles to direct endochondral repair of large bone defects. Bone Jt. Res., 2018, 7:263-273

[149] Nazarenko I et al. Cell surface tetraspanin Tspan8 contributes to molecular pathways of exosome-induced endothelial cell activation. Cancer Res., 2010, 70:1668-1678

[150] Escola JM et al. Selective enrichment of tetraspan proteins on the internal vesicles of multivesicular endosomes and on exosomes secreted by human B-lymphocytes. J. Biol. Chem., 1998, 273:20121-20127

[151] Yanez-Mo M, Barreiro O, Gordon-Alonso M, Sala-Valdes M, Sanchez-Madrid F. Tetraspanin-enriched microdomains: a functional unit in cell plasma membranes. Trends Cell Biol., 2009, 19:434-446

[152] Tamai K et al. Exosome secretion of dendritic cells is regulated by Hrs, an ESCRT-0 protein. Biochem. Biophys. Res. Commun., 2010, 399:384-390

[153] Mathew A, Bell A, Johnstone RM. Hsp-70 is closely associated with the transferrin receptor in exosomes from maturing reticulocytes. Biochem. J., 1995, 308 Pt 3 823-830

[154] Hsu C et al. Regulation of exosome secretion by Rab35 and its GTPase-activating proteins TBC1D10A-C. J. Cell Biol., 2010, 189:223-232

[155] Gutierrez-Vazquez C, Villarroya-Beltri C, Mittelbrunn M, Sanchez-Madrid F. Transfer of extracellular vesicles during immune cell-cell interactions. Immunol. Rev., 2013, 251:125-142

[156] Laulagnier K et al. PLD2 is enriched on exosomes and its activity is correlated to the release of exosomes. FEBS Lett., 2004, 572:11-14

[157] Shinozaki K, Waite M. A novel phosphatidylglycerol-selective phospholipase A2 from macrophages. Biochemistry, 1999, 38:1669-1675

[158] Beh CT, McMaster CR, Kozminski KG, Menon AK. A detour for yeast oxysterol binding proteins. J. Biol. Chem., 2012, 287:11481-11488

[159] Xu C et al. CD82 endocytosis and cholesterol-dependent reorganization of tetraspanin webs and lipid rafts. FASEB J., 2009, 23:3273-3288

[160] Carayon K et al. Proteolipidic composition of exosomes changes during reticulocyte maturation. J. Biol. Chem., 2011, 286:34426-34439

[161] Subra C, Laulagnier K, Perret B, Record M. Exosome lipidomics unravels lipid sorting at the level of multivesicular bodies. Biochimie, 2007, 89:205-212

[162] Falguieres T et al. In vitro budding of intralumenal vesicles into late endosomes is regulated by Alix and Tsg101. Mol. Biol. Cell, 2008, 19:4942-4955

[163] Yang M et al. Microvesicles secreted by macrophages shuttle invasion-potentiating microRNAs into breast cancer cells. Mol. Cancer, 2011, 10

[164] Ibrahim AG, Cheng K, Marban E. Exosomes as critical agents of cardiac regeneration triggered by cell therapy. Stem Cell Rep., 2014, 2:606-619

[165] Fujita Y et al. Intercellular communication by extracellular vesicles and their microRNAs in asthma. Clin. Ther., 2014, 36:873-881

[166] Liu S et al. MSC Transplantation Improves Osteopenia via Epigenetic Regulation of Notch Signaling in Lupus. Cell. Metab., 2015, 22:606-618

[167] Zhang J et al. Exosomes/tricalcium phosphate combination scaffolds can enhance bone regeneration by activating the PI3K/Akt signaling pathway. Stem Cell Res. Ther., 2016, 7:136

[168] Morrell AE et al. Mechanically induced Ca(2+) oscillations in osteocytes release extracellular vesicles and enhance bone formation. Bone Res., 2018, 6:6

[169] Martin PJ et al. Adipogenic RNAs are transferred in osteoblasts via bone marrow adipocytes-derived extracellular vesicles (EVs). BMC Cell. Biol., 2015, 16