In peripheral arterial disease (PAD), antiangiogenic VEGF-A165b isoform overexpression in monocytes contributes to impaired collateralization. Serine-arginine protein-kinase-1 (SRPK1) regulates VEGF splicing. To determine whether SRPK1 controlled monocytic VEGF, impairing collateralization, we investigated SRPK1 inhibition and monocyte-specific knockout in mouse models of and in human monocytes from PAD. VEGF-A165b activity was measured by coculture of monocytes from patients with PAD with endothelial cells with SRPK1 inhibition. Mice with impaired revascularization 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 a 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. Monocytes from patients with PAD 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 revascularization in LysM-Wnt5aGOF mice was rescued in LysM-Wnt5aGOF:SRPK1MoKO mice, which had a phenotypic shift toward M2 macrophages. Impaired blood flow recovery was also rescued in obese-SRPK1MoKO mice. 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 collateralization in mice, and in human in vitro models of monocyte-dependent impaired angiogenesis.NEW & 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 antiangiogenic 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. A new cell-specific SRPK1-LoxP mouse is described.

PDF file - 37K, Comparison of study cases and overall patient population

PDF file - 260K, Scoring of immunohistochemically stained samples

The glomerular endothelial glycocalyx (GEnGlx) forms the first part of the glomerular filtration barrier. Previously, we showed that mineralocorticoid receptor (MR) activation caused GEnGlx damage and albuminuria. In this study, we investigated whether MR antagonism could limit albuminuria in diabetes and studied the site of action. Streptozotocin-induced diabetic Wistar rats developed albuminuria, increased glomerular albumin permeability (Ps'alb), and increased glomerular matrix metalloproteinase (MMP) activity with corresponding GEnGlx loss. MR antagonism prevented albuminuria progression, restored Ps'alb, preserved GEnGlx, and reduced MMP activity. Enzymatic degradation of the GEnGlx negated the benefits of MR antagonism, confirming their dependence on GEnGlx integrity. Exposing human glomerular endothelial cells (GEnC) to diabetic conditions in vitro increased MMPs and caused glycocalyx damage. Amelioration of these effects confirmed a direct effect of MR antagonism on GEnC. To confirm relevance to human disease, we used a potentially novel confocal imaging method to show loss of GEnGlx in renal biopsy specimens from patients with diabetic nephropathy (DN). In addition, patients with DN randomized to receive an MR antagonist had reduced urinary MMP2 activity and albuminuria compared with placebo and baseline levels. Taken together, our work suggests that MR antagonists reduce MMP activity and thereby preserve GEnGlx, resulting in reduced glomerular permeability and albuminuria in diabetes.

Background Glomerular endothelial cell (GEnC) fenestrations are recognized as an essential component of the glomerular filtration barrier, yet little is known about how they are regulated and their role in disease. Methods We comprehensively characterized GEnC fenestral and functional renal filtration changes including measurement of glomerular Kf and GFR in diabetic mice (BTBR ob-/ob-). We also examined and compared human samples. We evaluated Eps homology domain protein-3 (EHD3) and its association with GEnC fenestrations in diabetes in disease samples and further explored its role as a potential regulator of fenestrations in an in vitro model of fenestration formation using b.End5 cells. Results Loss of GEnC fenestration density was associated with decreased filtration function in diabetic nephropathy. We identified increased diaphragmed fenestrations in diabetes, which are posited to increase resistance to filtration and further contribute to decreased GFR. We identified decreased glomerular EHD3 expression in diabetes, which was significantly correlated with decreased fenestration density. Reduced fenestrations in EHD3 knockdown b.End5 cells in vitro further suggested a mechanistic role for EHD3 in fenestration formation. Conclusions This study demonstrates the critical role of GEnC fenestrations in renal filtration function and suggests EHD3 may be a key regulator, loss of which may contribute to declining glomerular filtration function through aberrant GEnC fenestration regulation. This points to EHD3 as a novel therapeutic target to restore filtration function in disease.

Alternative splicing of the vascular endothelial growth factor A (VEGF-A) terminal exon generates two protein families with differing functions. Pro-angiogenic VEGF-Axxxa isoforms are produced via selection of the proximal 3' splice site of the terminal exon. Use of an alternative distal splice site generates the anti-angiogenic VEGF-Axxxb proteins. A bichromatic splicing-sensitive reporter was designed to mimic VEGF-A alternative splicing and was used as a molecular tool to further investigate this alternative splicing event. Part of VEGF-A's terminal exon and preceding intron were inserted into a minigene construct followed by the coding sequences for two fluorescent proteins. A different fluorescent protein is expressed depending on which 3' splice site of the exon is used during splicing (dsRED denotes VEGF-Axxxa and EGFP denotes VEGF-Axxxb). The fluorescent output can be used to follow splicing decisions in vitro and in vivo. Following successful reporter validation in different cell lines and altering splicing using known modulators, a screen was performed using the LOPAC library of small molecules. Alterations to reporter splicing were measured using a fluorescent plate reader to detect dsRED and EGFP expression. Compounds of interest were further validated using flow cytometry and assessed for effects on endogenous VEGF-A alternative splicing at the mRNA and protein level. Ex vivo and in vitro angiogenesis assays were used to demonstrate the anti-angiogenic effect of the compounds. Furthermore, anti-angiogenic activity was investigated in a Matrigel in vivo model. To conclude, we have identified a set of compounds that have anti-angiogenic activity through modulation of VEGF-A terminal exon splicing.

Written for the busy nephrologist and internist who need easy to access information on the diagnosis, investigation, and treatment of patients with kidney disease, the Oxford Desk Reference Nephrology is presented in a way that is not only easy to read and digest but also is detailed enough to allow an in depth understanding of the complex mix of metabolic, immunological, and genetic causes of both acute and chronic kidney disease. The kidneys are rarely affected by disease in isolation; the book comprehensively covers the multisystem disorders that require a multidisciplinary approach, including the cardiological, rheumatological, haematological, infectious, oncological, and urological aspects of kidney disease. In parallel, it extensively describes the myriad multisystem complications of progressive chronic kidney disease with practical advice on how these should be investigated and managed. The importance of understanding the evolution of kidney disease in children and young adults is covered, as in many parts of the world there is no distinction between adult and paediatric nephrology. Therefore, it is important that nephrologists have a sound grasp of both paediatric and adult kidney diseases. The number of patients with advanced kidney disease treated with a kidney transplant or receiving dialysis is increasing in all parts of the world. All nephrologists will manage patients on dialysis or who have a kidney transplant and all internists will encounter these patients. Thus, it is imperative that they have an understanding of these treatments and the commonly encountered medical problems such patients experience.

There is evidence to suggest that abnormal angiogenesis, inflammation, and fibrosis drive diabetic nephropathy (DN). However, there is no specific treatment to counteract these processes. We aimed to determine whether DIAVIT, a natural Vaccinium myrtillus (blueberry) and Hippophae Rhamnoides (sea buckthorn) extract, is protective in a model of type II DN. Diabetic db/db mice were administered DIAVIT in their drinking water for 14 weeks. We assessed the functional, structural, and ultra-structural phenotype of three experimental groups (lean+vehicle, db/db+vehicle, db/db+DIAVIT). We also investigated the angiogenic and fibrotic pathways involved in the mechanism of action of DIAVIT. Diabetic db/db mice developed hyperglycaemia, albuminuria, and an increased glomerular water permeability; the latter two were prevented by DIAVIT. db/db mice developed fibrotic glomeruli, endothelial insult, and glomerular ultra-structural changes, which were not present in DIAVIT-treated mice. Vascular endothelial growth factor A (VEGF-A) splicing was altered in the db/db kidney cortex, increasing the pro-angiogenic VEGF-A165 relative to the anti-angiogenic VEGF-A165b. This was partially prevented with DIAVIT treatment. Delphinidin, an anthocyanin abundant in DIAVIT, increased the VEGF-A165b expression relative to total VEGF-A165 in cultured podocytes through phosphorylation of the splice factor SRSF6. DIAVIT, in particular delphinidin, alters VEGF-A splicing in type II DN, rescuing the DN phenotype. This study highlights the therapeutic potential of natural drugs in DN through the manipulation of gene splicing and expression.

Vascular endothelial growth factor (VEGF)-A is differentially spliced to give two functionally different isoform families; pro-angiogenic, pro-permeability VEGF-A(xxx) and anti-angiogenic, anti-permeability VEGF-A(xxx)b. VEGF-A splicing is dysregulated in several pathologies, including cancer, diabetes, and peripheral arterial disease. The bichromatic VEGF-A splicing-sensitive fluorescent reporter harboured in a transgenic mouse is a novel approach to investigate the splicing patterns of VEGF-A in vivo. We generated a transgenic mouse harbouring a splicing-sensitive fluorescent reporter designed to mimic VEGF-A terminal exon splicing (VEGF8ab) by insertion into the ROSA26 genomic locus. dsRED expression denotes proximal splice site selection (VEGF-A(xxx)) and eGFP expression denotes distal splice site selection (VEGF-A(xxx)b). We investigated the tissue-specific expression patterns in the eye, skeletal muscle, cardiac muscle, kidney, and pancreas, and determined whether the splicing pattern could be manipulated in the same manner as endogenous VEGF-A by treatment with the SRPK1 inhibitor SPHINX 31. We confirmed expression of both dsRED and eGFP in the eye, skeletal muscle, cardiac muscle, kidney, and pancreas, with the highest expression of both fluorescent proteins observed in the exocrine pancreas. The ratio of dsRED and eGFP matched that of endogenous VEGF-A(xxx) and VEGF-A(xxx)b. Treatment of the VEGF8ab mice with SPHINX 31 increased the mRNA and protein eGFP/dsRED ratio in the exocrine pancreas, mimicking endogenous VEGF-A splicing. The VEGF-A exon 8 splicing-sensitive fluorescent reporter mouse is a novel tool to assess splicing regulation in the individual cell-types and tissues, which provides a useful screening process for potentially therapeutic splicing regulatory compounds in vivo

To investigate human glomerular structure under conditions of physiological perfusion, we have analyzed fresh and perfusion-fixed normal human glomeruli at physiological hydrostatic and oncotic pressures using serial resin section reconstruction, confocal, multiphoton, and electron microscope imaging. Afferent and efferent arterioles (21.5 ± 1.2 µm and 15.9 ± 1.2 µm diameter), recognized from vascular origins, lead into previously undescribed wider regions (43.2 ± 2.8 µm and 38.4 ± 4.9 µm diameter) we have termed vascular chambers (VCs) embedded in the mesangium of the vascular pole. Afferent VC (AVC) volume was 1.6-fold greater than efferent VC (EVC) volume. From the AVC, long nonbranching high-capacity conduit vessels (n = 7) (Con; 15.9 ± 0.7 µm diameter) led to the glomerular edge, where branching was more frequent. Conduit vessels have fewer podocytes than filtration capillaries. VCs were confirmed in fixed and unfixed specimens with a layer of banded collagen identified in AVC walls by multiphoton and electron microscopy. Thirteen highly branched efferent first-order vessels (E1; 9.9 ± 0.4 µm diameter) converge on the EVC, draining into the efferent arteriole (15.9 ± 1.2 µm diameter). Banded collagen was scarce around EVCs. This previously undescribed branching topology does not conform to the branching of minimum energy expenditure (Murray’s law), suggesting that even distribution of pressure/flow to the filtration capillaries is more important than maintaining the minimum work required for blood flow. We propose that AVCs act as plenum manifolds possibly aided by vortical flow in distributing and balancing blood flow/pressure to conduit vessels supplying glomerular lobules. These major adaptations to glomerular capillary structure could regulate hemodynamic pressure and flow in human glomerular capillaries.

Background/Aims: Genetic cell ablation using the human diphtheria toxin receptor (hDTR) is a new strategy used for analysing cellular function. Diphtheria toxin (DT) is a cytotoxic protein that leaves mouse cells relatively unaffected, but upon binding to hDTR it ultimately leads to cell death. We used a podocyte-specific hDTR expressing (Pod-DTR) mouse to assess the anti-permeability and cyto-protective effects of the splice isoform vascular endothelial growth factor (VEGF-A165b). Methods: The Pod-DTR mouse was crossed with a mouse that over-expressed VEGF-A165b specifically in the podocytes (Neph-VEGF-A165b). Wild type (WT), Pod-DTR, Neph-VEGF-A165b and Pod-DTR X Neph-VEGF-A165b mice were treated with several doses of DT (1, 5, 100, and 1,000 ng/g bodyweight). Urine was collected and the glomerular water permeability (LpA/Vi) was measured ex vivo after 14 days. Structural analysis and podocyte marker expression were also assessed. Results: Pod-DTR mice developed an increased glomerular LpA/Vi 14 days after administration of DT (all doses), which was prevented when the mice over-expressed VEGF-A165b. No major structural abnormalities, podocyte ablation or albuminuria was observed in Pod-DTR mice, indicating this to be a mild model of podocyte disease. However, a change in expression and localisation of nephrin within the podocytes was observed, indicating disruption of the slit diaphragm in the Pod-DTR mice. This was prevented in the Pod-DTR X Neph-VEGF-A165b mice. Conclusion: Although only a mild model of podocyte injury, over-expression of the anti-permeability VEGF-A165b isoform in the podocytes of Pod-DTR mice had a protective effect. Therefore, this study further highlights the therapeutic potential of VEGF-A165b in glomerular disease.

The structure of the kidney glomerulus, known since Bowman's description in 18571, is of arterial afferent capillaries leading to exchange capillaries and an efferent arteriole. While investigating the three dimensional structure of the glomerulus we discovered that this description is incorrect in adult human glomeruli. Serial section reconstruction of glomeruli perfused‐fixed under physiological colloid osmotic and hydrostatic pressures showed that afferent and efferent arterioles lead into previously undescribed ellipsoid, wide vascular chambers (VCs). From the afferent vascular chamber (AVC), 5–7 long, non‐branching, conduit vessels lead to the glomerular edge where branching occurs. Using multiphoton microscopy, a signal consistent with banded (fibrilar) collagen was seen in second harmonic generation mode in unfixed glomeruli in a region consistent with vascular chamber walls imaged by two photon fluorescence. Electron microscopy confirmed that a layer of banded collagen surrounds VC walls. Approximately thirteen highly branched, first order vessels (E1) converge on the efferent VC (EVC), which drains into the efferent arteriole. Complex vortical flow modelling predicted that the AVC acts as a plenum manifold, distributing and balancing blood flow/pressure to conduit vessels supplying blood to different glomerular lobules. These previously undescribed adaptations of glomerular vascular structure in humans could regulate haemodynamic pressure and flow in glomeruli, and their disturbance provide a new mechanism to explain kidney diseases.Support or Funding InformationThe Richard Bright Research Trust, Kidney Research UK (2014–2015) and the Medical Research Council G10002073 and MR/K020366/1This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The vascular endothelial growth factor (VEGF) family of proteins are key regulators of physiological systems. Originally linked with endothelial function, they have since become understood to be principal regulators of multiple tissues, both through their actions on vascular cells, but also through direct actions on other tissue types, including epithelial cells, neurons, and the immune system. The complexity of the five members of the gene family in terms of their different splice isoforms, differential translation, and specific localizations have enabled tissues to use these potent signaling molecules to control how they function to maintain their environment. This homeostatic function of VEGFs has been less intensely studied than their involvement in disease processes, development, and reproduction, but they still play a substantial and significant role in healthy control of blood volume and pressure, interstitial volume and drainage, renal and lung function, immunity, and signal processing in the peripheral and central nervous system. The widespread expression of VEGFs in healthy adult tissues, and the disturbances seen when VEGF signaling is inhibited support this view of the proteins as endogenous regulators of normal physiological function. This review summarizes the evidence and recent breakthroughs in understanding of the physiology that is regulated by VEGF, with emphasis on the role they play in maintaining homeostasis. © 2017 American Physiological Society. Compr Physiol 8:955-979, 2018.

Rationale: Fibrosis after lung injury is related to poor outcome, and idiopathic pulmonary fibrosis (IPF) can be regarded as an exemplar. Vascular endothelial growth factor (VEGF)‐A has been implicated in this context, but there are conflicting reports as to whether it is a contributory or protective factor. Differential splicing of the VEGF‐A gene produces multiple functional isoforms including VEGF‐A165a and VEGF‐A165b, a member of the inhibitory family. To date there is no clear information on the role of VEGF‐A in IPF. Objectives: To establish VEGF‐A isoform expression and functional effects in IPF. Methods: We used tissue sections, plasma, and lung fibroblasts from patients with IPF and control subjects. In a bleomycin‐induced lung fibrosis model we used wild‐type MMTV mice and a triple transgenic mouse SPC‐rtTA+/−TetoCre+/−LoxP‐VEGF‐A+/+ to conditionally induce VEGF‐A isoform deletion specifically in the alveolar type II (ATII) cells of adult mice. Measurements and Main Results: IPF and normal lung fibroblasts differentially expressed and responded to VEGF‐A165a and VEGF‐A165b in terms of proliferation and matrix expression. Increased VEGF‐A165b was detected in plasma of progressing patients with IPF. In a mouse model of pulmonary fibrosis, ATII‐specific deficiency of VEGF‐A or constitutive overexpression of VEGF‐A165b inhibited the development of pulmonary fibrosis, as did treatment with intraperitoneal delivery of VEGF‐A165b to wild‐type mice. Conclusions: These results indicate that changes in the bioavailability of VEGF‐A sourced from ATII cells, namely the ratio of VEGF‐Axxxa to VEGF‐Axxxb, are critical in development of pulmonary fibrosis and may be a paradigm for the regulation of tissue repair.

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.

The endothelial glycocalyx forms a continuous coat over the luminal surface of all vessels, and regulates multiple vascular functions. The contribution of individual components of the endothelial glycocalyx to one critical vascular function, microvascular permeability, remains unclear. We developed novel, real-time, paired methodologies to study the contribution of sialic acids within the endothelial glycocalyx to the structural and functional permeability properties of the same microvessel in vivo. Single perfused rat mesenteric microvessels were perfused with fluorescent endothelial cell membrane and glycocalyx labels, and imaged with confocal microscopy. A broad range of glycocalyx depth measurements (0.17–3.02μm) were obtained with different labels, imaging techniques and analysis methods. The distance between peak cell membrane and peak glycocalyx label provided the most reliable measure of endothelial glycocalyx anatomy, correlating with paired, numerically smaller values of endothelial glycocalyx depth (0.078±0.016μm) from electron micrographs of the same portion of the same vessel. Disruption of sialic acid residues within the endothelial glycocalyx using neuraminidase perfusion decreased endothelial glycocalyx depth and increased apparent solute permeability to albumin in the same vessels in a timedependent manner, with changes in all three true vessel wall permeability coefficients (hydraulic conductivity, reflection coefficient, and diffusive solute permeability). These novel technologies expand the range of techniques that permit direct studies of the structure of the endothelial glycocalyx and dependent microvascular functions in vivo, and demonstrate that sialic acid residues within the endothelial glycocalyx are critical regulators of microvascular permeability to both water and albumin.

The endothelial glycocalyx forms a continuous coat over the luminal surface of all vessels, and regulates multiple vascular functions. The contribution of individual components of the endothelial glycocalyx to one critical vascular function, microvascular permeability, remains unclear. We developed novel, real-time, paired methodologies to study the contribution of sialic acids within the endothelial glycocalyx to the structural and functional permeability properties of the same microvessel in vivo. Single perfused rat mesenteric microvessels were perfused with fluorescent endothelial cell membrane and glycocalyx labels, and imaged with confocal microscopy. A broad range of glycocalyx depth measurements (0.17-3.02m) were obtained with different labels, imaging techniques and analysis methods. The distance between peak cell membrane and peak glycocalyx label provided the most reliable measure of endothelial glycocalyx anatomy, correlating with paired, numerically smaller values of endothelial glycocalyx depth (0.0780.016m) from electron micrographs of the same portion of the same vessel. Disruption of sialic acid residues within the endothelial glycocalyx using neuraminidase perfusion decreased endothelial glycocalyx depth and increased apparent solute permeability to albumin in the same vessels in a time-dependent manner, with changes in all three true vessel wall permeability coefficients (hydraulic conductivity, reflection coefficient and diffusive solute permeability). These novel technologies expand the range of techniques that permit direct studies of the structure of the endothelial glycocalyx and dependent microvascular functions in vivo, and demonstrate that sialic acid residues within the endothelial glycocalyx are critical regulators of microvascular permeability to both water and albumin.

Alternative splicing of vascular endothelial growth factor (VEGF-A) gives rise to isoform families, the pro-angiogenic VEGF-Axxx and the anti-angiogenic VEGF-Axxxb. VEGF-A165b has previously been shown to be protective in several murine models of renal disease, as well as providing cytoprotection to podocytes in culture. This study aimed to investigate whether a blueberry extract that promotes VEGF-A­165b expression, is a potential therapeutic in a mouse model of type I diabetic nephropathy. The natural extract had no effect on blood glucose levels, but did delay the onset/progression of albuminuria in diabetic mice, and prevented increases in glomerular water permeability. Diabetic control mice had a reduced glomerular expression of nephrin and reduced glomerular capillary circumference, which were rescued when treated with the natural extract. HUVECs displayed reduced tube formation when treated with the natural extract, which was rescued upon addition of Ab-VEGF-A165b. Certain unknown compounds within the blueberry extract are able to switch VEGF-A splicing to promote VEGF-A165b expression in podocytes. The extract plays a protective role in the prevention and treatment of diabetic nephropathy in the DBA/2J type I diabetic mouse model. This study highlights the therapeutic potential of switching VEGF-A splicing to promote VEGF-A165b in diabetic nephropathy.

Vascular endothelial growth factor (VEGF) undergoes alternative splicing to produce both proangiogenic and antiangiogenic isoforms. Preferential splicing of proangiogenic VEGF is determined by serine-arginine protein kinase 1 (SRPK1), which is upregulated in a number of cancers. In the present study, we aimed to investigate SRPK1 expression in prostate cancer (PCa) and its association with cancer progression. SRPK1 expression was assessed using immunohistochemistry of PCa tissue extracted from radical prostatectomy specimens of 110 patients. SRPK1 expression was significantly higher in tumour compared with benign tissue (p<0.00001) and correlated with higher pT stage (p=0.004), extracapsular extension (p=0.003) and extracapsular perineural invasion (p=0.008). Interestingly, the expression did not correlate with Gleason grade (p=0.21), suggesting that SRPK1 facilitates the development of a tumour microenvironment that favours growth and invasion (possibly through stimulating angiogenesis) while having little bearing on the morphology or function of the tumour cells themselves.