title: Thymosin beta4 is an essential paracrine factor of embryonic endothelial progenitor cell-mediated cardioprotection.
abstract: BACKGROUND
  Prolonged myocardial ischemia results in cardiomyocyte loss despite successful revascularization. We have reported that retrograde application of embryonic endothelial progenitor cells (eEPCs) provides rapid paracrine protection against ischemia-reperfusion injury. Here, we investigated the role of thymosin beta4 (Tbeta4) as a mediator of eEPC-mediated cardioprotection.
  
  
  RESULTS
  In vitro, neonatal rat cardiomyocytes were subjected to hypoxia-reoxygenation in the absence or presence of eEPCs with or without Tbeta4 short hairpin RNA (shRNA) transfection. In vivo, pigs (n=9 per group) underwent percutaneous left anterior descending artery occlusion for 60 minutes on day 1. After 55 minutes of ischemia, control eEPCs (5x10(6) cells) or cells transfected with Tbeta4 shRNA when indicated or 15 mg Tbeta4 alone were retroinfused into the anterior interventricular vein. Segmental endocardial shortening in the infarct zone at 150-bpm atrial pacing, infarct size (triphenyl tetrazolium chloride viability and methylene blue exclusion), and inflammatory cell influx (myeloperoxidase activity) were determined 24 hours later. Survival of neonatal rat cardiomyocytes increased from 32+/-4% to 90+/-2% after eEPC application, an effect sensitive to shRNA transfection compared with Tbeta4 (45+/-7%). In vivo, infarct size decreased with eEPC application (38+/-4% versus 54+/-4% of area at risk; P<0.01), an effect abolished by Tbeta4 shRNA (62+/-3%). Segmental subendocardial shortening improved after eEPC treatment (22+/-3% versus -3+/-4% of control area) unless Tbeta4 shRNA was transfected (-6+/-4%). Retroinfusion of Tbeta4 mimicked eEPC application (infarct size, 37+/-3%; segmental endocardial shortening, 34+/-7%). Myeloperoxidase activity (3323+/-388 U/mg in controls) was decreased by eEPCs (1996+/-546 U/mg) or Tbeta4 alone (1455+/-197 U/mg) but not Tbeta4 shRNA-treated eEPCs (5449+/-829 U/mg).
  
  
  CONCLUSIONS
  Our findings show that short-term cardioprotection derived by regional application of eEPCs can be attributed, at least in part, to Tbeta4.
authors.affiliation: Medizinische Klinik I, University Clinic Grosshadern, Munich, Germany.
authors.forename: Rabea
authors.initials: R
authors.lastname: Hinkel
authors.forename: Chiraz
authors.initials: C
authors.lastname: El-Aouni
authors.forename: Tonia
authors.initials: T
authors.lastname: Olson
authors.forename: Jan
authors.initials: J
authors.lastname: Horstkotte
authors.forename: Stefan
authors.initials: S
authors.lastname: Mayer
authors.forename: Sebastian
authors.initials: S
authors.lastname: Müller
authors.forename: Michael
authors.initials: M
authors.lastname: Willhauck
authors.forename: Christine
authors.initials: C
authors.lastname: Spitzweg
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Gildehaus
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Münzing
authors.forename: Ewald
authors.initials: E
authors.lastname: Hannappel
authors.forename: Ildiko
authors.initials: I
authors.lastname: Bock-Marquette
authors.forename: J Michael
authors.initials: JM
authors.lastname: DiMaio
authors.forename: Antonis K
authors.initials: AK
authors.lastname: Hatzopoulos
authors.forename: Peter
authors.initials: P
authors.lastname: Boekstegers
authors.forename: Christian
authors.initials: C
authors.lastname: Kupatt
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000276:immunology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000637:transplantation; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology; D015316:Genetic Therapy / Q000379:methods; D007962:Leukocytes / Q000166:cytology; D051379:Mice; D008822:Mice, Transgenic; D017202:Myocardial Ischemia / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology* / Q000628:therapy*; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000502:physiology*; D019899:Paracrine Communication / Q000502:physiology; D051381:Rats; D033581:Stem Cell Transplantation; D013552:Swine; D013947:Thymosin / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D000099201:Thymosin beta(4)
chemical_list: D013947:Thymosin; D000099201:Thymosin beta(4)