VEGF‐A₁₆₅b protects against proteinuria in a mouse model with progressive depletion of all endogenous VEGF‐A splice isoforms from the kidney

Abstract

Key points Progressive depletion of all vascular endothelial growth factor A (VEGF‐A) splice isoforms from the kidney results in proteinuria and increased glomerular water permeability, which are both rescued by over‐expression of VEGF‐A165b only.VEGF‐A165b rescues the increase in glomerular basement membrane and podocyte slit width, as well as the decrease in sub‐podocyte space coverage, produced by VEGF‐A depletion.VEGF‐A165b restores the expression of platelet endothelial cell adhesion molecule in glomerular endothelial cells and glomerular capillary circumference.VEGF‐A165b has opposite effects to VEGF‐A165 on the expression of genes involved in endothelial cell migration and proliferation. AbstractChronic kidney disease is strongly associated with a decrease in the expression of vascular endothelial growth factor A (VEGF‐A). However, little is known about the contribution of VEGF‐A splice isoforms to kidney physiology and pathology. Previous studies suggest that the splice isoform VEGF‐A165b (resulting from alternative usage of a 3′ splice site in the terminal exon) is protective for kidney function. In the present study, we show, in a quad‐transgenic model, that over‐expression of VEGF‐A165b alone is sufficient to rescue the increase in proteinuria, as well as glomerular water permeability, in the context of progressive depletion of all VEGF‐A isoforms from the podocytes. Ultrastructural studies show that the glomerular basement membrane is thickened, podocyte slit width is increased and sub‐podocyte space coverage is reduced when VEGF‐A is depleted, all of which are rescued in VEGF‐A165b over‐expressors. VEGF‐A165b restores the expression of platelet endothelial cell adhesion molecule‐1 in glomerular endothelial cells and glomerular capillary circumference. Mechanistically, it increases VEGF receptor 2 expression both in vivo and in vitro and down‐regulates genes involved in migration and proliferation of endothelial cells, otherwise up‐regulated by the canonical isoform VEGF‐A165. The results of the present study indicate that manipulation of VEGF‐A splice isoforms could be a novel therapeutic avenue in chronic glomerular disease.

Vascular Endothelial Growth Factor-A₁₆₅b Restores Normal Glomerular Water Permeability in a Diphtheria-Toxin Mouse Model of Glomerular Injury

“…We speculate that the mechanism of VEGF-A 165 b in reducing the glomerular L p A/V i may be due to its previously reported effects on reducing the glomerular endothelial fenestration density, thus reducing permeability [17]. Furthermore, the treatment of conditionally immortalised GEnCs with VEGF-A 165 b has been reported to reduce the phosphorylation of VEGFR2, which in turn could decrease the permeability of the GFB [25]. On the other hand, podocyte-specific over-expression of the pro-permeability isoform, VEGF-A 164 , has been reported to result in glomerular dysfunction including increased glomerular L p A/V i , which could be rescued by the constitutive over-expression of VEGF-A 165 b [14], and a collapsing nephropathy phenotype [26].…”

Modulation of VEGF-A Alternative Splicing as a Novel Treatment in Chronic Kidney Disease

“…Although the VEGF-A xxx b isoforms have the same number of amino acids in total, they have an altered C-terminal sequence that differs by six amino acids ( Figure 1 ). This small change in the terminal six amino acids results in VEGF-A xxx b having functionally opposite properties to VEGF-A xxx ; VEGF-A xxx b has anti-angiogenic, anti-permeability, and anti-migratory properties [ 9 , 10 , 13 , 20 ]. However, like VEGF-A xxx , VEGF-A xxx b is a pro-survival factor [ 21 ].…”

“…It is becoming increasingly clear that changes to the tightly regulated process of AS in many genes can result in cellular dysfunction and disease. Cancer is the disease that is most commonly linked to AS dysregulation [ 6 , 7 , 8 ]; however, there are an increasing number of splice isoforms that have been recently implicated in kidney disease, including vascular endothelial growth factor A (VEGF-A) [ 9 , 10 ]. VEGF-A is key driver of angiogenesis, permeability, migration, and cell survival [ 11 ].…”

“…The abnormal expression of VEGF-A in the kidney has been widely reported in most types of kidney disease [ 12 ]. Alternative splicing of exon 8 of the VEGF-A gene results in the expression of an anti-angiogenic, anti-permeability, and cyto-protective family of isoforms, termed the VEGF-A xxx b family (the most common isoform being VEGF-A 165 b) [ 13 ], which has been shown to be protective in kidney disease [ 9 , 10 ].…”

Beneficial or deleterious effects of vascular endothelial growth factor may depend on the isoform involved

“…In this issue of The Journal of Physiology , Stevens et al . () studied the protective effect of overexpression of the vascular endothelial growth factor (VEGF)‐A 165 b splice isoform in the kidney, leading to rescue of abnormal glomerular permeability and proteinuria, which was present in knock‐out mice of all VEGF‐A isoforms. This well‐performed study proposes that a mouse model with progressive depletion of all VEGF‐A isoforms results in proteinuria and increased glomerular water permeability.…”