Abstract
Introduction In peripheral arterial disease (PAD) anti-angiogenic VEGF-A165b isoform overexpression in monocytes contributes to impaired collateralisation. Serine-arginine protein-kinase-1 (SRPK1) regulates VEGF splicing. To determine whether SRPK1 controlled monocytic VEGF, impairing collateralisation, we investigated SRPK1 inhibition and monocyte-specific knockout in mouse models of and in human monocytes from PAD.
Methods VEGF-A165b activity was measured by co-culture of PAD patients’ monocytes with endothelial cells with SRPK1 inhibition. Mice with impaired revascularisation due to soluble-frizzled-related-protein-5 knockout (Sfrp5-/-), monocyte-specific Wnt5a gain-of-function (LysM-Wnt5aGOF), or obese mice on a high-fat high-sucrose (HF/HS) diet were subjected to femoral artery ligation and treated with SRPK1 inhibitor. We generated an SRPK1 conditional knockout and crossed it with monocyte-specific (LysM-Cre) driver line to specifically knockout SRPK1 in monocyte lineages. Blood flow was measured by Laser Speckle Imaging before, and for 28 days after surgery.
Results Monocytes from PAD patients significantly inhibited endothelial cell migration, which was reversed by an anti-VEGF-A165b antibody. Surprisingly, migration was stimulated by SRPK1 inhibition, switching splicing from VEGF-A165b to VEGF-A165a. In Sfrp5-/-, LysM-Wnt5aGOF and HF/HS mouse models of PAD, blood flow was improved by SRPK1 inhibition. Impaired revascularisation in LysM-Wnt5aGOF mice was rescued in LysM-Wnt5aGOF:SRPK1MoKO mice, which had a phenotypic shift towards M2 macrophages. Impaired blood flow recovery was also rescued in obese-SRPK1MoKO mice.
Conclusion VEGF splicing in monocytes is regulated differently from VEGF splicing in epithelial or cancer cells suggesting that control of splicing is dependent on cell type and/or environment. SRPK1 inhibition enhances collateralisation in mice, and in human in vitro models of monocyte-dependent impaired angiogenesis.
New and Noteworthy A novel potential treatment for peripheral arterial disease (PAD) is described. Inhibition of SRPK1, or knockout in monocytes, induces angiogenesis by preventing splicing to anti-angiogenic VEGF (VEGF-A165b) in patients and animal models. In PAD, monocyte splicing control is different from other cell types and SRPK1 inhibition by drug like compounds can alter macrophage phenotype and reverse PAD in mice using a new cell specific SRPK1-LoxP mouse.
Competing Interest Statement
JCM, SJH, and JB and DOB hold equity in companies that are making SRPK1 inhibitors for clinical use. DOB and SJH hold equity in companies that are making antibodies to VEGF165b for clinical use.
Footnotes
Additional data on monocyte phenotype is included (new figure 3F, G, fig 4H and I, and figure 6). This shows that SRPK1 knockout alters the phenotype of the macrophages towards and M2 phenotype
