Slit2 modifies VEGF-induced angiogenic responses in rabbit skeletal muscle by inducing capillary sprouting and decreasing vascular permeability via reduced eNOS activity

Rationale: Slit2 is a possible modulator of vascular endothelial growth factor (VEGF) - induced angiogenesis, but its effects have not been tested in large animal models. Objective: We studied the effect of Slit2 on therapeutic angiogenesis induced by VEGF receptor 2 (VEGFR2) ligands Vammin and VEGF-D?N?C in vivo in rabbit skeletal muscles. The Slit2 target genes were also studied by RNA sequencing (RNA-Seq) in endothelial cells. Methods and Results: Adenoviral intramuscular gene transfers were performed into rabbit hindlimbs. Confocal and multiphoton microscopy were used for blood vessel imaging. Signaling experiments and gene expression analyses were performed to study mechanisms of Slit2 action. Slit2 decreased VEGFR2-mediated vascular permeability. It also reduced VEGFR2-mediated increase in blood perfusion and capillary enlargement, whereas sprouting of the capillaries was increased. Slit2 gene transfer alone did not have any effects on vascular functions or morphology. VEGFR2 activation was not affected by Slit2, but eNOS phosphorylation was diminished. The transcriptome profiling showed Slit2 downregulating angiogenesis-related genes such as nuclear receptor subfamily 4 group A member 1 (NR4A1) and Stanniocalcin-1 (STC-1) as well as genes related to endothelial cell migration and vascular permeability. Conclusions: Combining Slit2 with VEGFs adjusts VEGFR2-mediated angiogenic effects into a more physiological direction. This possibly allows the use of higher VEGF vector doses to achieve a more widespread vector and VEGF distribution in the target tissues leading to a better therapeutic outcome while reducing excess vascular permeability. Overall design: HUVEC mRNA profiles after adenoviral vector gene transfers in duplicate.

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Nieminen T, Toivanen PI, Laakkonen JP, Heikura T, Kaikkonen MU, Airenne KJ, Ylä-Herttuala S