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Vascular endothelial growth factor-a (VEGF-A) and nitric oxide (NO) are essential for glomerular filtration barrier homeostasis, and are dysregulated in diabetic kidney disease (DKD). While NO availability is consistently low in diabetes, both high and low VEGF-A have been reported in patients with DKD. Here we examined the effect of inducible podocyte VEGF-A knockdown (VEGFKD) in diabetic mice and in endothelial nitric oxide synthase knockout mice (eNOS−/−). Diabetes was induced with streptozotocin using the Animal Models of Diabetic Complications Consortium (AMDCC) protocol. Induction of podocyte VEGFKD led to diffuse glomerulosclerosis, foot process effacement, and GBM thickening in both diabetic mice with intact eNOS and in non-diabetic eNOS−/−:VEGFKD mice. VEGFKD diabetic mice developed mild proteinuria and maintained normal glomerular filtration rate (GFR), associated with extremely high NO and thiol urinary excretion. In eNOS−/−:VEGFKD (+dox) mice severe diffuse glomerulosclerosis was associated with microaneurisms, arteriolar hyalinosis, massive proteinuria, and renal failure. Collectively, data indicate that combined podocyte VEGF-A and eNOS deficiency result in diffuse glomerulosclerosis in mice; compensatory NO and thiol generation prevents severe proteinuria and GFR loss in VEGFKD diabetic mice with intact eNOS, whereas VEGFKD induction in eNOS−/−:VEGFKD mice causes massive proteinuria and renal failure mimicking DKD in the absence of diabetes. Mechanistically, we identify VEGFKD-induced abnormal S-nitrosylation of specific proteins, including β3-integrin, laminin, and S-nitrosoglutathione reductase (GSNOR), as targetable molecular mechanisms involved in the development of advanced diffuse glomerulosclerosis and renal failure.

The synchronized advent of high-throughput next-generation sequencing technology and knowledge of the human genome has rendered exponential contributions to our understanding of the pathophysiology of glomerular kidney diseases. A genetic diagnosis can now be made or confirmed in about two-thirds of the suspected inherited glomerular diseases. Next-generation sequencing is adept at identifying single nucleotide variations and small insertions or deletions that constitute majority of the disease-causing mutations. Description of the complete mutation spectrum in syndromic glomerulopathies may require the use of both sequencing and cytogenetic methods to detect large structural DNA variation in addition to single nucleotide changes. The enthusiastic application of genetic and genomic knowledge to inherited glomerular diseases has uncovered anticipated and unforeseen challenges mainly related to the biological interpretation of variants of uncertain significance and the limited benefit on clinical management for the individual patient when a diagnosis is obtained. To attain the ultimate goal of transforming clinical decision-making based on accurate genetic diagnosis using genomic information, these challenges need to be addressed. Till then, the glory of genomic medicine stands the test of time in this gilded age of genomic advancements., Author(s): Ashima Gulati [sup.1] , Neera Dahl [sup.1] , Alda Tufro [sup.2] [sup.3] Author Affiliations: (1) grid.47100.32, 0000000419368710, Department of Internal Medicine/ Nephrology, Yale University School of Medicine, , New [...]

The onset of diabetic nephropathy (DN) is highlighted by glomerular filtration barrier abnormalities. Identifying pathogenic factors and targetable pathways driving DN is crucial to developing novel therapies and improving the disease outcome. Semaphorin3a (sema3a) is a guidance protein secreted by podocytes. Excess sema3a disrupts the glomerular filtration barrier. Here, using immunohistochemistry, we show increased podocyte SEMA3A in renal biopsies from patients with advanced DN. Using inducible, podocyte-specific Sema3a gain-of-function (Sema3a(+)) mice made diabetic with streptozotocin, we demonstrate that sema3a is pathogenic in DN. Diabetic Sema3a(+) mice develop massive proteinuria, renal insufficiency, and extensive nodular glomerulosclerosis, mimicking advanced DN in humans. In diabetic mice, Sema3a(+) exacerbates laminin and collagen IV accumulation in Kimmelstiel-Wilson-like glomerular nodules and causes diffuse podocyte foot process effacement and F-actin collapse via nephrin, αvβ3 integrin, and MICAL1 interactions with plexinA1. MICAL1 knockdown and sema3a inhibition render podocytes not susceptible to sema3a-induced shape changes, indicating that MICAL1 mediates sema3a-induced podocyte F-actin collapse. Moreover, sema3a binding inhibition or podocyte-specific plexinA1 deletion markedly ameliorates albuminuria and abrogates renal insufficiency and the diabetic nodular glomerulosclerosis phenotype of diabetic Sema3a(+) mice. Collectively, these findings indicate that excess sema3a promotes severe diabetic nephropathy and identifies novel potential therapeutic targets for DN.

The molecular pathogenesis of diabetic kidney disease progression is complex and remains unresolved. Rho-GAP MYO9A was recently identified as a novel podocyte protein and a candidate gene for monogenic FSGS. Myo9A involvement in diabetic kidney disease has been suggested. Here, we examined the effect of diabetic milieu on Myo9A expression in vivo and in vitro. We determined that Myo9A undergoes S-nitrosylation, a post-translational modification dependent on nitric oxide (NO) availability. Diabetic mice with nodular glomerulosclerosis and severe proteinuria associated with doxycycline-induced, podocyte-specific VEGF164 gain-of-function showed markedly decreased glomerular Myo9A expression and S-nitrosylation, as compared to uninduced diabetic mice. Immortalized mouse podocytes exposed to high glucose revealed decreased Myo9A expression, assessed by qPCR, immunoblot and immunocytochemistry, and reduced Myo9A S-nitrosylation (SNO-Myo9A), assessed by proximity link assay and biotin switch test, functionally resulting in abnormal podocyte migration. These defects were abrogated by exposure to a NO donor and were not due to hyperosmolarity. Our data demonstrate that high-glucose induced decrease of both Myo9A expression and SNO-Myo9A is regulated by NO availability. We detected S-nitrosylation of Myo9A interacting proteins RhoA and actin, which was also altered by high glucose and NO dependent. RhoA activity inversely related to SNO-RhoA. Collectively, data suggest that dysregulation of SNO-Myo9A, SNO-RhoA and SNO-actin may contribute to the pathogenesis of advanced diabetic kidney disease and may be amenable to therapeutic targeting.

Steroid-sensitive nephrotic syndrome (SRNS) can cause CKD and necessitate kidney transplant. Here the authors identify FAT1 mutations by homozygosity mapping and whole-exome sequencing in families with SRNS and provide functional mouse and zebrafish evidence that FAT1 is required for normal glomerular and tubular function and that FAT1 mutations can cause SRNS.

Cognitive decline due to neurodegenerative diseases is a prevalent worldwide problem. Both pharmacological and non-pharmacological treatments to improve, delay or stop disease progression are of vital importance. Cognitive stimulation is frequently used in clinical practice; however, there are few studies that demonstrate its efficacy. Aim: To evaluate the efficacy of cognitive stimulation in patients with mild cognitive impairment (CDR = 0.5) and dementia (CDR = 1). Methods: A retrospective cohort study was performed. Patients with cognitive impairment receiving weekly cognitive stimulation (16 or 24 sessions) were evaluated with a complete neuropsychological battery before and after the stimulation program. Each stimulation session was carried out by a trained neuropsychologist. Results: Forty two patients receiving cognitive stimulation were evaluated over a period of 12.53 months (SD 5.5). Patients were grouped as 11 amnesic mild cognitive impairment (aMCI), 23 multi domain mild cognitive impairment (mMCI) and 8 Mild Alzheimer's Dementia (CDR 1). None of the groups improved their cognitive functions after the cognitive stimulation program. MCI group was also divided according to their global intelligence quotient (IQ) into two groups: low (IQ < 98.5) and high (IQ > 98.5). Each group was compared before and after the stimulation program and no significant difference was found (p ≥ 0.05). Moreover, MCI group was also analyzed according to the duration of the stimulation program: less than 9, between 9 and 13 and more than 13 months. Different duration groups were compared before and after the cognitive stimulation program and no significant differences were found. Depression, anxiety and subjective memory symptoms were also analysed and neither improvement nor worsening could be demonstrated. Conclusions: Patients remained stable, both in cognitive and behavioural domains, for more than 18 months. However, no significant cognitive or behavioural improvement can be reported in these patients after the stimulation program (duration time: 12.53 months SD 5.5).

The prevalence of diabetes mellitus increased during the last century and it is estimated that 45% of the patients are not diagnosed. In South America the prevalence of diabetes and chronic kidney disease (CKD) increased, with a great disparity among the countries with respect to access to dialysis. In Ecuador it is one of the main causes of mortality, principally in the provinces located on the coast of the Pacific Ocean. The greatest single cause of beginning dialysis is diabetic nephropathy (DN). Even using the best therapeutic options for DN, the residual risk of proteinuria and of terminal CKD remains high. In this review we indicate the importance of the problem globally and in our region. We analyse relevant cellular and molecular studies that illustrate the crucial significance of glomerular events in DN development and evolution and in insulin resistance. We include basic anatomical, pathophysiological and clinical concepts, with special attention to the role of angiogenic factors such as the vascular endothelial growth factor (VEGF-A) and their relationship to the insulin receptor, endothelial isoform of nitric oxide synthase (eNOS) and angiopoietins. We also propose various pathways that have therapeutic potential in our opinion. Greater in-depth study of VEGF-A and angiopoietins, the state of glomerular VEGF resistance, the relationship of VEGF receptor 2/nephrin, VEGF/insulin receptors/nephrin and the relationship of VEGF/eNOS-NO at glomerular level could provide solutions to the pressing world problem of DN and generate new treatment alternatives.

La prevalencia de diabetes mellitus aumentó en el último siglo y se estima que el 45% de los pacientes, no estarían diagnosticados. En Sudamérica la prevalencia de diabetes y de enfermedad renal crónica (ERC) incrementó, existiendo gran disparidad entre los países respecto al acceso a diálisis. En Ecuador es una de las principales causas de mortalidad, principalmente en las provincias ubicadas en la costa del océano Pacífico. La mayor causa aislada de ingreso a diálisis es la nefropatía diabética (ND). Aun utilizando las mejores opciones terapéuticas para la ND, el riesgo residual de proteinuria y de ERC terminal permanece elevado. En esta revisión describimos la importancia del problema en el mundo y en nuestra región. Analizamos estudios moleculares y celulares relevantes que indican la crucial importancia de eventos glomerulares en el desarrollo y en la evolución de la ND y en la insulinorresistencia. Incluimos conceptos anatómicos, fisiopatológicos y clínicos básicos, desarrollando especial énfasis en el rol de factores angiogénicos como el factor de crecimiento vascular endotelial (VEGF-A) y su relación con el receptor de insulina, la sintasa endotelial de óxido nítrico-óxido nítrico (eNOS) y las angiopoietinas. En el transcurso del texto proponemos diversas vías, que a nuestro entender tienen potencial terapéutico. Profundizar en el estudio del VEGF-A y las angiopoietinas, el estado de VEGF resistencia glomerular, la relación del receptor 2 de VEGF/ nefrina, VEGF/receptores de insulina/nefrina, la relación VEGF/eNOS-ON a nivel glomerular podría aportar soluciones al acuciante problema de la ND en el mundo y generar nuevas alternativas de tratamiento.

Semaphorin3a (sema3a), a member of class 3 semaphorins, is a guidance protein that regulates angiogenesis, branching morphogenesis, axon growth, and cell migration, and has pleiotropic roles on organogenesis, immune response, and cancer. Sema3a is secreted by podocytes and is required for normal kidney patterning and glomerular filtration barrier development. We recently discovered that after completion of kidney development, Sema3a gain-of-function in podocytes leads to proteinuric glomerular disease in mice. Excess sema3a causes foot process effacement, glomerular basement lamination, and endothelial damage in vivo, and disrupts cell autonomously podocyte shape by downregulating nephrin and inhibiting Keywords Semaphorin3a * Glomerular filtration barrier * Podocyte signals * Proteinuria * Cell shape * Integrin activity, Introduction Semaphorins are phylogenetically conserved guidance proteins that regulate cellular function and shape [1]. Semaphorins were initially identified as axon repellents during nervous system development, and later found to modulate [...]

Podocyte or endothelial cell VEGF-A knockout causes thrombotic microangiopathy in adult mice. To study the mechanism involved in acute and local injury caused by low podocyte VEGF-A we developed an inducible, podocyte-specific VEGF-A knockdown mouse, and we generated an immortalized podocyte cell line (VEGF(KD)) that downregulates VEGF-A upon doxycycline exposure. Tet-O-siVEGF:podocin-rtTA mice express VEGF shRNA in podocytes in a doxycycline-regulated manner, decreasing VEGF-A mRNA and VEGF-A protein levels in isolated glomeruli to ~20% of non-induced controls and urine VEGF-A to ~30% of control values a week after doxycycline induction. Induced tet-O-siVEGF:podocin-rtTA mice developed acute renal failure and proteinuria, associated with mesangiolysis and microaneurisms. Glomerular ultrastructure revealed endothelial cell swelling, GBM lamination and podocyte effacement. VEGF knockdown decreased podocyte fibronectin and glomerular endothelial alpha(V)beta(3) integrin in vivo. VEGF receptor-2 (VEGFR2) interacts with beta(3) integrin and neuropilin-1 in the kidney in vivo and in VEGF(KD) podocytes. Podocyte VEGF knockdown disrupts alpha(V)beta(3) integrin activation in glomeruli, detected by WOW1-Fab. VEGF silencing in cultured VEGF(KD) podocytes downregulates fibronectin and disrupts alpha(V)beta(3) integrin activation cell-autonomously. Collectively, these studies indicate that podocyte VEGF-A regulates alpha(V)beta(3) integrin signaling in the glomerulus, and that podocyte VEGF knockdown disrupts alpha(V)beta(3) integrin activity via decreased VEGFR2 signaling, thereby damaging the three layers of the glomerular filtration barrier, causing proteinuria and acute renal failure.

Vascular endothelial growth factor (VEGF-A) signaling is required for endothelial cell differentiation, vasculogenesis, angiogenesis, and vascular patterning. During kidney morphogenesis, podocyte VEGF-A guides endothelial cells toward developing glomeruli. Podocyte VEGF-A expression continues throughout life but its function after completion of development remains unclear. Here, we examined the expression of VEGF-A and its receptors VEGFR1, VEGFR2, NP1, and NP2 in conditionally immortalized mouse podocytes cultured in undifferentiated and differentiated conditions using RT-PCR and Western analysis. VEGF-A secretion was assessed by ELISA and Western analysis. Upon podocyte differentiation, VEGF-A protein expression and secretion increased threefold. Differentiated podocytes expressed eightfold higher VEGFR2 mRNA levels than undifferentiated podocytes, whereas VEGFR1, sVEGFR1, NP1, and NP2 mRNA levels were similar. We examined the regulation and function of the VEGF-A system by exposing differentiated podocytes to recombinant VEG[F.sub.165] (20 ng/ ml) or control media for 24 h. VEG[F.sub.165] induced a twofold increase in VEGFR2 mRNA and protein levels, whereas VEGFR1, sVEGFR1, NP1, and NP2 mRNA levels remained unchanged. VEG[F.sub.165] induced VEGFR2 phosphorylation. VEG[F.sub.165] reduced podocyte apoptosis ~40%, whereas anti-VEGFR2 neutralizing antibody enhanced it twofold. We determined that VEGF-A signaling regulates slit diaphragm proteins by inducing a dose-response podocin upregulation and increasing its interaction with CD2AP. The data indicate that podocytes in culture have a functional autocrine VEGF-A system that is regulated by differentiation and ligand availability. VEGF-A functions in podocytes include promoting survival through VEGFR2, inducing podocin upregulation and increasing podocin/CD2AP interaction. cell differentiation; apoptosis; VEGF-A secretion; slit diaphragm proteins; VEGF receptor 2 doi:10.1152/ajprenal.00448.2005

To determine whether low oxygen is a stimulus for endothelial cell differentiation and vascular development in the kidney, we examined the effect of low oxygen on rat metanephric organ culture, a model known to recapitulate nephrogenesis in the absence of vessels. After 6 days in culture in standard (20% [O.sub.2]) or low oxygen (1-3% [O.sub.2]) conditions, metanephric kidney growth and morphology were assessed by DNA measurement, and light and electron microscopy. DNA content was higher in 3% [O.sub.2]-treated explants (2.5 [+ or -] 0.17 [[micro]gram]/kidney, n = 9) than in 20% [O.sub.2] explants (1.5 [+ or -] 0.09 [[micro]gram]/kidney, n = 9), P < 0.05. Low oxygen induced proliferation of tubular epithelial cells, resulting in enhanced number of tubules of similar size. Endothelial cells forming capillaries were localized in 3% [O.sub.2] explants by light and electron microscopy and by immunocytochemistry using endothelial cell markers. Fit-1, Flk-1, and ACE-containing cells were detected in 3% [O.sub.2]treated explants, whereas 20% [O.sub.2] explants were virtually negative. VEGF mRNA levels were 10-fold higher in 3% [O.sub.2]treated explants than in 20% [O.sub.2]-treated explants. Addition of anti-VEGF antibodies to 3% [O.sub.2]-treated explants prevented low oxygen-induced growth and endothelial cell differentiation and proliferation. Our data indicate that low oxygen stimulates growth by cell proliferation and induces tubulogenesis, endothelial cell differentiation, and vasculogenesis in metanephric kidneys in culture. Upregulation of VEGF expression by low oxygen and prevention of low oxygen-induced tubulogenesis and vasculogenesis by anti-VEGF antibodies indicate that these changes were mediated by VEGF. These data suggest that low oxygen is the stimulus to initiate renal vascularization.

Neurovascular development is controlled by angiotensin II (ANG II) in most animals. Blocking the ANG II type 1 receptor (AT1) in newborn Sprague-Dawson rats stops the maturation of the neurovasculature and the growth of the kidneys. The afferent arterioles in the kidney are less in number, thicker and shorter than normal; the glomerulus is smaller and less in number and tubular dilation is less. Inhibition of the formation of ANG II in tadpoles of Rana also causes defects in the renal development. However blocking AT2 has no effect on renal development in rats.

Analysis of the infusion of an angiotensin II (ANG II) antagonist, losartan, into rats reveals the regulatory effect of ANG II on renal growth and characterizes angiotensin type 1 (AT1) gene during development. The AT1 receptor mediates renal and somatic ANG II-initiated growth through cell hyperplasia modulation. ANG II exhibits tonic inhibition of renin gene expression during normal growth through the AT1 receptor and induces response in renin secreting cells.