title: Thrombin receptor PAR-1 activation on endothelial progenitor cells enhances chemotaxis-associated genes expression and leukocyte recruitment by a COX-2-dependent mechanism.
abstract: BACKGROUND
  Endothelial colony forming cells (ECFC) represent a subpopulation of endothelial progenitor cells involved in endothelial repair. The activation of procoagulant mechanisms associated with the vascular wall's inflammatory responses to injury plays a crucial role in the induction and progression of atherosclerosis. However, little is known about ECFC proinflammatory potential.
  
  
  OBJECTIVE
  To explore the role of the thrombin receptor PAR-1 proinflammatory effects on ECFC chemotaxis/recruitment capacity.
  
  
  RESULTS
  The expression of 30 genes known to be associated with inflammation and chemotaxis was quantified in ECFC by real-time qPCR. PAR-1 activation with the SFLLRN peptide (PAR-1-ap) resulted in a significant increase in nine chemotaxis-associated genes expression, including CCL2 and CCL3 whose receptors are present on ECFC. Furthermore, COX-2 expression was found to be dramatically up-regulated consequently to PAR-1 activation. COX-2 silencing with the specific COX-2-siRNA also triggered down-regulation of the nine target genes. Conditioned media (c.m.) from control-siRNA- and COX-2-siRNA-transfected ECFC, stimulated or not with PAR-1-ap, were produced and tested on ECFC capacity to recruit leukocytes in vitro as well in the muscle of ischemic hindlimb in a preclinical model. The capacity of the c.m. from ECFC stimulated with PAR-1-ap to recruit leukocytes was abrogated when COX-2 gene expression was silenced in vitro (in terms of U937 cells migration and adhesion to endothelial cells) as well as in vivo. Finally, the postnatal vasculogenic stem cell derived from infantile hemangioma tumor (HemSC) incubated with PAR-1-ap increased leukocyte recruitment in Matrigel(®) implant.
  
  
  CONCLUSIONS
  PAR-1 activation in ECFC increases chemotactic gene expression and leukocyte recruitment at ischemic sites through a COX-2-dependent mechanism.
authors.affiliation: Sorbonne Paris Cité, Université Paris Descartes, Paris, France.
authors.forename: Clément
authors.initials: C
authors.lastname: d'Audigier
authors.forename: Clément
authors.initials: C
authors.lastname: Cochain
authors.forename: Elisa
authors.initials: E
authors.lastname: Rossi
authors.forename: Coralie L
authors.initials: CL
authors.lastname: Guérin
authors.forename: Ivan
authors.initials: I
authors.lastname: Bièche
authors.forename: Adeline
authors.initials: A
authors.lastname: Blandinières
authors.forename: Bérengère
authors.initials: B
authors.lastname: Marsac
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Silvestre
authors.forename: Pascale
authors.initials: P
authors.lastname: Gaussem
authors.forename: David M
authors.initials: DM
authors.lastname: Smadja
mesh_terms: D000818:Animals; D050197:Atherosclerosis / Q000378:metabolism; D002633:Chemotaxis; D017077:Culture Media, Conditioned; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004195:Disease Models, Animal; D018450:Disease Progression; D042783:Endothelial Cells / Q000166:cytology; D005312:Fetal Blood / Q000166:cytology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006391:Hemangioma / Q000276:immunology; D006801:Humans; D007249:Inflammation; D007962:Leukocytes / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D034741:RNA, Small Interfering / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology*; D020298:U937 Cells
chemical_list: D017077:Culture Media, Conditioned; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human