title: Paracrine effects of CD34 progenitor cells on angiogenic endothelial sprouting.
abstract: BACKGROUND
  Progenitor cells contribute to repair of ischemia-associated disturbances of microcirculations, but detailed mechanisms of paracrine angiogenic activation of endothelium by progenitor cells are unclear. The present study was designed to test whether progenitor cells maintain their activation pattern of cytokine secretion and capillary-like endothelial sprout attraction under conditions of hypoxia induced angiogenic activation.
  
  
  METHODS
  CD34 progenitor cells were kept separated together with spheroids of human umbilical vein endothelial cells (HUVEC) sharing a common medium supernatant to generate a paracrine diffusion gradient from CD34 cells to the endothelial cell spheroids. The expression of 27 cytokines was analyzed in the supernatant. The length and the direction of the capillary like sprouts were analyzed under 20% and 1% oxygen concentration.
  
  
  RESULTS
  Co-culture with CD34 cells increased sprout length of HUVEC spheroids by 18%, while reduction of oxygen concentration from 20% to 1% increased sprout length by 52%. Analysis of the direction of the sprout growth revealed a directed growth toward CD34 cells under normoxic as well as under hypoxic conditions. Paracrine induction of cytokine secretion by co-culture was similar in normoxia and in hypoxia with IL-8 (60-80-fold induction) >IL-6 and MIP-1beta (10-20-fold) >MIP-1alpha and MCP-1 (3-10-fold).
  
  
  CONCLUSIONS
  These data indicate that CD34 cell induced paracrine activation of cytokine secretion pattern and attraction of endothelial sprouting are well maintained under conditions of hypoxia induced endothelial cell sprout growth. This is a prerequisite for paracrine effectiveness of trapped progenitor cells in hypoperfused and hypooxygenated tissue areas.
authors.affiliation: Department of Cardiothoracic Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany. robert.scheubel@medizin.uni-halle.de
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Scheubel
authors.forename: Juergen
authors.initials: J
authors.lastname: Holtz
authors.forename: Ivar
authors.initials: I
authors.lastname: Friedrich
authors.forename: Jochen
authors.initials: J
authors.lastname: Borgermann
authors.forename: Simone
authors.initials: S
authors.lastname: Kahrstedt
authors.forename: Alexander
authors.initials: A
authors.lastname: Navarrete Santos
authors.forename: Rolf-Edgar
authors.initials: RE
authors.lastname: Silber
authors.forename: Andreas
authors.initials: A
authors.lastname: Simm
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D054405:Chemokine CCL3 / Q000378:metabolism; D054407:Chemokine CCL4 / Q000378:metabolism; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000502:physiology*; D019899:Paracrine Communication / Q000502:physiology*; D018874:Spheroids, Cellular; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D018952:Antigens, CD34; C111835:CCL2 protein, human; C515429:CCL3 protein, human; C066507:CCL4 protein, human; D018932:Chemokine CCL2; D054405:Chemokine CCL3; D054407:Chemokine CCL4; C508600:IL6 protein, human; D015850:Interleukin-6