title: Transdifferentiation of blood-derived human adult endothelial progenitor cells into functionally active cardiomyocytes.
abstract: BACKGROUND
  Further to promoting angiogenesis, cell therapy may be an approach for cardiac regeneration. Recent studies suggest that progenitor cells can transdifferentiate into other lineages. However, the transdifferentiation potential of endothelial progenitor cells (EPCs) is unknown.
  
  
  RESULTS
  EPCs were obtained from peripheral blood mononuclear cells of healthy adults or coronary artery disease (CAD) patients by cultivating with endothelial cell medium and growth factors. After 3 days, >95% of adherent cells were functionally and phenotypically EPCs. Diacetylated LDL-labeled EPCs were then cocultivated with rat cardiomyocytes for 6 days, resulting in significant increases of EPC cell length and size to a cardiomyocyte-like morphology. Biochemically, 9.94+/-1.39% and 5.04+/-1.09% of EPCs from healthy adults (n=15) or CAD patients (n=14, P<0.01 versus healthy adults), respectively, expressed alpha-sarcomeric actinin as measured by flow cytometry. Immunocytochemistry showed that human EPCs expressed alpha-sarcomeric actinin, cardiac troponin I (both with partial sarcomeric organization), atrial natriuretic peptide, and myocyte enhancer factor 2. Fluo 4 imaging demonstrated calcium transients synchronized with adjacent rat cardiomyocytes in transdifferentiated human EPCs. Single-cell microinjection of Lucifer yellow and calcein-AM labeling of cardiomyocytes demonstrated gap junctional communication between 51+/-7% of EPCs (16 hours after labeling, n=4) and cardiomyocytes. EPC transdifferentiation into cardiomyocytes was not observed with conditioned medium but in coculture with paraformaldehyde-fixed cardiomyocytes.
  
  
  CONCLUSIONS
  EPCs from healthy volunteers and CAD patients can transdifferentiate in vitro into functionally active cardiomyocytes when cocultivated with rat cardiomyocytes. Cell-to-cell contact but not cellular fusion mediates EPC transdifferentiation. The therapeutic use of autologous EPCs may aid cardiomyocyte regeneration in patients with ischemic heart disease.
authors.affiliation: Molecular Cardiology, Department of Internal Medicine IV, University of Frankfurt, Frankfurt, Germany.
authors.forename: Cornel
authors.initials: C
authors.lastname: Badorff
authors.forename: Ralf P
authors.initials: RP
authors.lastname: Brandes
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Popp
authors.forename: Stefan
authors.initials: S
authors.lastname: Rupp
authors.forename: Carmen
authors.initials: C
authors.lastname: Urbich
authors.forename: Alexandra
authors.initials: A
authors.lastname: Aicher
authors.forename: Ingrid
authors.initials: I
authors.lastname: Fleming
authors.forename: Rudi
authors.initials: R
authors.lastname: Busse
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Zeiher
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dimmeler
mesh_terms: D000328:Adult; D000818:Animals; D002118:Calcium / Q000032:analysis; D002450:Cell Communication; D002454:Cell Differentiation; D002478:Cells, Cultured; D018920:Coculture Techniques; D003324:Coronary Artery Disease / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D017629:Gap Junctions / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
chemical_list: D002118:Calcium