title: Discovery of microvascular miRNAs using public gene expression data: miR-145 is expressed in pericytes and is a regulator of Fli1.
abstract: BACKGROUND
  A function for the microRNA (miRNA) pathway in vascular development and angiogenesis has been firmly established. miRNAs with selective expression in the vasculature are attractive as possible targets in miRNA-based therapies. However, little is known about the expression of miRNAs in microvessels in vivo. Here, we identified candidate microvascular-selective miRNAs by screening public miRNA expression datasets.
  
  
  METHODS
  Bioinformatics predictions of microvascular-selective expression were validated with real-time quantitative reverse transcription PCR on purified microvascular fragments from mouse. Pericyte expression was shown with in situ hybridization on tissue sections. Target sites were identified with 3' UTR luciferase assays, and migration was tested in a microfluid chemotaxis chamber.
  
  
  RESULTS
  miR-145, miR-126, miR-24, and miR-23a were selectively expressed in microvascular fragments isolated from a range of tissues. In situ hybridization and analysis of Pdgfb retention motif mutant mice demonstrated predominant expression of miR-145 in pericytes. We identified the Ets transcription factor Friend leukemia virus integration 1 (Fli1) as a miR-145 target, and showed that elevated levels of miR-145 reduced migration of microvascular cells in response to growth factor gradients in vitro.
  
  
  CONCLUSIONS
  miR-126, miR-24 and miR-23a are selectively expressed in microvascular endothelial cells in vivo, whereas miR-145 is expressed in pericytes. miR-145 targets the hematopoietic transcription factor Fli1 and blocks migration in response to growth factor gradients. Our findings have implications for vascular disease and provide necessary information for future drug design against miRNAs with selective expression in the microvasculature.
authors.affiliation: Wallenberg Laboratory for Cardiovascular Research, Bruna Stråket 16, Sahlgrenska University Hospital, SE-413 45 Gothenburg, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Larsson
authors.forename: Peder
authors.initials: P
authors.lastname: Fredlund Fuchs
authors.forename: Johan
authors.initials: J
authors.lastname: Heldin
authors.forename: Irmeli
authors.initials: I
authors.lastname: Barkefors
authors.forename: Cecilia
authors.initials: C
authors.lastname: Bondjers
authors.forename: Guillem
authors.initials: G
authors.lastname: Genové
authors.forename: Christelle
authors.initials: C
authors.lastname: Arrondel
authors.forename: Pär
authors.initials: P
authors.lastname: Gerwins
authors.forename: Christine
authors.initials: C
authors.lastname: Kurschat
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schermer
authors.forename: Thomas
authors.initials: T
authors.lastname: Benzing
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Harvey
authors.forename: Johan
authors.initials: J
authors.lastname: Kreuger
authors.forename: Per
authors.initials: P
authors.lastname: Lindahl