title: Pericytes influence endothelial cell growth characteristics: role of plasminogen activator inhibitor type 1 (PAI-1).
abstract: OBJECTIVE
  Pericytes, located in close proximity to the underlying endothelium, form an integral component of the microvasculature. These cells are intimately involved in angiogenesis, which is of fundamental importance in many physiological and pathological processes. We evaluated the influence of pericyte-conditioned medium (PCM) on endothelial cell growth characteristics and modulation of endothelial gene expression.
  
  
  METHODS
  Migration and tubule formation assays were performed in vitro to determine the effect of PCM on endothelial growth characteristics. cDNA microarray analysis was used to identify alterations in gene expression following exposure of human microvascular endothelial cells (HMEC-1) to PCM. Overexpression of PAI-1 using recombinant protein or transient transfection, and inhibition using an inhibitory antibody against PAI-1, were used to determine whether up- or down-regulation of this gene was responsible for the changes in endothelial cell characteristics observed in response to PCM exposure.
  
  
  RESULTS
  We have shown that PCM exerts a dramatic inhibitory influence on endothelial cell migration in vitro. In addition, endothelial cells cultured on Matrigel and exposed to PCM were found to generate significantly fewer angiogenic branches. Microarray analysis of endothelial cells exposed to PCM identified PAI-1 as the gene showing the greatest level of differential expression (3.4-fold induction). Studies using an inhibitory antibody to PAI-1 suggest that induction of this protein by PCM is pivotal to the observed inhibitory influence on the migratory and angiogenic potential of HMEC-1. We further investigated this by overexpressing PAI-1, which was shown to have a potent inhibitory influence on EC migration and angiogenic branching, although the concentration of PAI-1 was clearly important.
  
  
  CONCLUSIONS
  Collectively, these findings suggest that PCM contains a bioactive element(s) that controls both endothelial cell migration and tubule formation in vitro and that these responses may be partially controlled by increased endothelial cell expression of PAI-1.
authors.affiliation: Biomedical Sciences Research Institute, University of Ulster, Coleraine, County Londonderry, BT52 1SA, Northern Ireland, United Kingdom.
authors.forename: Marie
authors.initials: M
authors.lastname: McIlroy
authors.forename: Martin
authors.initials: M
authors.lastname: O'Rourke
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: McKeown
authors.forename: David G
authors.initials: DG
authors.lastname: Hirst
authors.forename: Tracy
authors.initials: T
authors.lastname: Robson
mesh_terms: D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D018919:Neovascularization, Physiologic; D020411:Oligonucleotide Array Sequence Analysis; D020286:Pericytes / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics* / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; D017395:Plasminogen Activator Inhibitor 1