The splicing factor kinase SRPK1 is a therapeutic target for Peripheral Vascular Disease

In peripheral arterial disease (PAD) vascular insufficiency and reduced blood flow results from overexpression of the anti-angiogenic splice isoform of VEGF-A, VEGF-A 165 b, in monocytes. Serine-arginine protein-kinase 1 (SRPK1) has been shown to regulate VEGF splicing. To determine SRPK1 involvement in VEGF splicing in PAD monocytes, we investigated the effects of SRPK1 inhibition and monocyte-specific SRPK1-knockout in mouse models of PAD in which VEGF-A 165 b is upregulated in monocytes, and in human monocytes from PAD patients. PAD patient monocytes significantly reduced migration of human endothelial cells in co-culture, which was reversed by an anti-VEGF-A 165 b antibody. This reduction was also reversed by SRPK1 inhibition, which switched splicing from VEGF-A 165 b to VEGF-A 165 a. Impaired revascularisation after femoral artery ligation, measured by Laser Speckle Imaging, due to either soluble frizzled-related protein-5 knockout (Sfrp5 -/- ), monocyte-specific Wnt5a gain-of-function (LysM-Wnt5a GOF ), or a high fat high sucrose (HF/HS) diet, was reversed by the SRPK1 inhibitor SPHINX31. To determine monocyte specific SRPK1 activity we generated an SRPK1 conditional knockout mouse, and crossed it with LysM-Wnt5a GOF mice. Again impaired blood flow was rescued in these triple-transgenic monocyte-specific SRPK1-knockout (SRPK1 MoKO ) mice. Impaired blood flow in obese mice was also rescued in obese-SRPK1 MoKO mice. These results indicate that SRPK1 inhibition enhances collateralisation in in vitro and in vivo models of monocyte dependent impaired angiogenesis. Furthermore, VEGF splicing in monocytes is differently regulated from VEGF splicing in epithelial cells or cancer cells indicating that control of splicing is dependent on cell type and/or environment.