title: Vascular endothelial growth factor receptor upregulation in response to cell-based angiogenic gene therapy.
abstract: BACKGROUND
  We have previously reported that transplantation of vascular endothelial growth factor transfected cells into myocardial scar enhances angiogenesis. We evaluated the effect of transplanted cell type, time, and region of the heart on expression of the vascular endothelial growth factor receptors fms-like tyrosine kinase-1 (flt-1) and fetal liver kinase-1 (flk-1).
  
  
  METHODS
  Lewis rats underwent myocardial cryoinjury 3 weeks before transplantation with heart cells (a mixed culture of cardiomyocytes, smooth muscle cells, endothelial cells, and fibroblasts), vascular endothelial growth factor transfected heart cells, skeletal myoblasts, vascular endothelial growth factor transfected skeletal myoblasts, or medium (controls) (N = 13 each). Flt-1 and flk-1 expression in the scar, border zone, and normal myocardium were evaluated at 3 days and 1, 2, and 4 weeks by quantitative polymerase chain reaction. Transplanted cells, vascular endothelial growth factor, flt-1, and flk-1 were identified by immunohistology.
  
  
  RESULTS
  Flt-1 and flk-1 levels were low in all areas of control hearts. Upregulation of flt-1 and flk-1 after cell transplantation occurred primarily in host cells in the border zone rather than the scar (zone, p < 0.0001). Flt-1 and flk-1 expression was doubled by heart cells and skeletal myoblasts and increased eightfold by vascular endothelial growth factor transfected heart cells and skeletal myoblasts (group, p < 0.0001). Flk-1 expression peaked at 1 week, whereas flt-1 peaked at 2 weeks (time, p < 0.0001).
  
  
  CONCLUSIONS
  Flk-1 and flt-1 upregulation may mediate the angiogenic effect of cell transplantation and are augmented by vascular endothelial growth factor transgene expression, perhaps through a paracrine effect. Optimizing the angiogenic response to cell transplantation may maximize the benefit of cell transplantation strategies.
authors.affiliation: Division of Cardiovascular Surgery, Toronto General Hospital, University Health Network, University of Toronto, Heart & Stroke Foundation, Richard Lewar Centre of Excellence, Toronto, Ontario, Canada. terry.yau@utoronto.ca
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Yau
authors.forename: Guangming
authors.initials: G
authors.lastname: Li
authors.forename: Yaoguang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Richard D
authors.initials: RD
authors.lastname: Weisel
authors.forename: Donald A G
authors.initials: DA
authors.lastname: Mickle
authors.forename: Ren-Ke
authors.initials: RK
authors.lastname: Li
mesh_terms: D000818:Animals; D017690:Cell Transplantation; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000637:transplantation; D005260:Female; D005347:Fibroblasts / Q000637:transplantation; D005786:Gene Expression Regulation; D015316:Genetic Therapy; D006331:Heart Diseases / Q000628:therapy; D008297:Male; D009206:Myocardium / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000637:transplantation; D018919:Neovascularization, Physiologic / Q000235:genetics*; D019899:Paracrine Communication; D051381:Rats; D011917:Rats, Inbred Lew; D014162:Transfection; D019076:Transgenes; D015854:Up-Regulation; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000096:biosynthesis* / Q000235:genetics; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000096:biosynthesis* / Q000235:genetics
chemical_list: C501164:Flt1 protein, rat; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2