title: Exosomes from human CD34(+) stem cells mediate their proangiogenic paracrine activity.
abstract: BACKGROUND
  Transplantation of human CD34(+) stem cells to ischemic tissues has been associated with reduced angina, improved exercise time, and reduced amputation rates in phase 2 clinical trials and has been shown to induce neovascularization in preclinical models. Previous studies have suggested that paracrine factors secreted by these proangiogenic cells are responsible, at least in part, for the angiogenic effects induced by CD34(+) cell transplantation.
  
  
  OBJECTIVE
  Our objective was to investigate the mechanism of CD34(+) stem cell-induced proangiogenic paracrine effects and to examine if exosomes, a component of paracrine secretion, are involved.
  
  
  RESULTS
  Exosomes collected from the conditioned media of mobilized human CD34(+) cells had the characteristic size (40 to 90 nm; determined by dynamic light scattering), cup-shaped morphology (electron microscopy), expressed exosome-marker proteins CD63, phosphatidylserine (flow cytometry) and TSG101 (immunoblotting), besides expressing CD34(+) cell lineage marker protein, CD34. In vitro, CD34(+) exosomes replicated the angiogenic activity of CD34(+) cells by increasing endothelial cell viability, proliferation, and tube formation on Matrigel. In vivo, the CD34(+) exosomes stimulated angiogenesis in Matrigel plug and corneal assays. Interestingly, exosomes from CD34(+) cells but not from CD34(+) cell-depleted mononuclear cells had angiogenic activity.
  
  
  CONCLUSIONS
  Our data demonstrate that human CD34(+) cells secrete exosomes that have independent angiogenic activity both in vitro and in vivo. CD34(+) exosomes may represent a significant component of the paracrine effect of progenitor cell transplantation for therapeutic angiogenesis.
authors.affiliation: Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Susmita
authors.initials: S
authors.lastname: Sahoo
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Klychko
authors.forename: Tina
authors.initials: T
authors.lastname: Thorne
authors.forename: Sol
authors.initials: S
authors.lastname: Misener
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Schultz
authors.forename: Meredith
authors.initials: M
authors.lastname: Millay
authors.forename: Aiko
authors.initials: A
authors.lastname: Ito
authors.forename: Ting
authors.initials: T
authors.lastname: Liu
authors.forename: Christine
authors.initials: C
authors.lastname: Kamide
authors.forename: Hemant
authors.initials: H
authors.lastname: Agrawal
authors.forename: Harris
authors.initials: H
authors.lastname: Perlman
authors.forename: Gangjian
authors.initials: G
authors.lastname: Qin
authors.forename: Raj
authors.initials: R
authors.lastname: Kishore
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Losordo
mesh_terms: D042501:Angiogenic Proteins / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D018952:Antigens, CD34 / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D016510:Corneal Neovascularization / Q000276:immunology / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D055354:Exosomes / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D005434:Flow Cytometry; D006801:Humans; D008027:Light; D008297:Male; D051379:Mice; D008819:Mice, Nude; D046529:Microscopy, Electron, Transmission; D018919:Neovascularization, Physiologic; D019899:Paracrine Communication; D010316:Particle Size; D010718:Phosphatidylserines / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D012542:Scattering, Radiation; D013234:Stem Cells / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D060149:Tetraspanin 30; D014157:Transcription Factors / Q000378:metabolism; D000099177:Tsg101 Protein
chemical_list: D042501:Angiogenic Proteins; D015703:Antigens, CD; D018952:Antigens, CD34; D015415:Biomarkers; D017077:Culture Media, Conditioned; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D010718:Phosphatidylserines; D010980:Platelet Membrane Glycoproteins; D060149:Tetraspanin 30; D014157:Transcription Factors; D000099177:Tsg101 Protein; C554586:CD63 protein, human; C554587:Cd63 protein, mouse