Abstract 20024: Shear Stress-and Klf2-regulated Mir-27b Controls Pericyte Recruitment and Vessel Maturation
Vessel maturation involves recruitment of mural cells. Laminar shear stress is a major trigger for vessel maturation. However, the molecular mechanisms by which shear stress affects recruitment of pericytes are unclear. MicroRNAs (miRs) are small non-coding RNAs, which post-transcriptionally control gene expression. Since shear stress regulates various miRs, we hypothesize that flow-induced miRs inhibit repulsive cues and facilitate mural cell coverage.
Since the transcription factor KLF2 is responsible for the majority of shear stress induced genes, we first determined the role of KLF2 for vessel maturation in the mouse retina. Indeed, loss of endothelial KLF2 induces vessel regression and reduces vessel density (p<0.001). Next, we determined the expression of miRs in KLF2 or laminar flow exposed endothelial cells (ECs). We show that shear stress induces miR-27b (2.8±0.24-fold, p<0.05) in cultured ECs and in mouse femoral artery segments that were exposed to physiological shear stress ex vivo (1.5±0.14-fold, p<0.05). KLF2 overexpression increased miR-27b expression (385±41%). Silencing of KLF2 under shear stress conditions abolished the flow-induced expression of miR-27b. Predicted targets for miR-27b include members of the semaphorin (SEMA) family (known to regulate repulsive signaling) and angiopoietin-2 (Ang2), which causes vessel destabilization. MiR-27b overexpression reduces SEMA6A (63.5±13.5%), SEMA6D (58±26%), and Ang2 (51.5±11%) expression.
To determine whether miR-27b controls pericyte recruitment, we tested the effect of endothelial miR-27b on adhesion of pericytes. Overexpression of miR-27b increased the adhesion of pericytes (p<0.05) and inhibition of miR-27b reduced pericyte adhesion in vitro (p<0.05). In an in vitro matrigel assay overexpression of miR-27b increased pericyte coverage of endothelial cell tubes (155±45%), whereas inhibition of miR-27b reduced pericyte coverage (81±15%). In vivo inhibition of miR-27b had no effect on the blood brain barrier integrity but lead to morphological changes in the mouse uterus which may be caused by edema.
Taken together, our data demonstrate that shear stress and KLF2 regulate miR-27b, which targets Ang-2 and semaphorins, and controls pericyte adhesion and coverage.
Author Disclosures: S. Demolli: None. A. Doddaballapur: None. K. Stark: None. R.A. Boon: None. A. Eckart: None. T. Korff: None. M. Hecker: None. S. Massberg: None. D. Kaluza: None. S. Dimmeler: None.
- © 2014 by American Heart Association, Inc.