The extracellular matrix protein fibronectin promotes metanephric kidney development.

Complex interactions of the branching ureteric bud (UB) and surrounding mesenchymal cells during metanephric kidney development determine the final number of nephrons. Impaired nephron endowment predisposes to arterial hypertension and chronic kidney disease. In the kidney, extracellular matrix (ECM) proteins are usually regarded as acellular scaffolds or as the common histological end-point of chronic kidney diseases. Since only little is known about their physiological role in kidney development, we aimed for analyzing the expression and role of fibronectin. In mouse, fibronectin was expressed during all stages of kidney development with significant changes over time. At embryonic day (E) 12.5 and E13.5, fibronectin lined the UB epithelium, which became less pronounced at E16.5 and then switched to a glomerular expression in the postnatal and adult kidneys. Similar results were obtained in human kidneys. Deletion of fibronectin at E13.5 in cultured metanephric mouse kidneys resulted in reduced kidney sizes and impaired glomerulogenesis following reduced cell proliferation and branching of the UB epithelium. Fibronectin colocalized with alpha 8 integrin and fibronectin loss caused a reduction in alpha 8 integrin expression, release of glial-derived neurotrophic factor and expression of Wnt11, both of which are promoters of UB branching. In conclusion, the ECM protein fibronectin acts as a regulator of kidney development and is a determinant of the final nephron number.

Oxysterol-binding protein-like 7 deficiency leads to ER stress-mediated apoptosis in podocytes and proteinuria.

Chronic kidney disease (CKD) is associated with renal lipid dysmetabolism among a variety of other pathways. We recently demonstrated that oxysterol-binding protein-like 7 (OSBPL7) modulates the expression and function of ATP-binding cassette subfamily A member 1 (ABCA1) in podocytes, a specialized type of cell essential for kidney filtration. Drugs that target OSBPL7 lead to improved renal outcomes in several experimental models of CKD. However, the role of OSBPL7 in podocyte injury remains unclear. Using mouse models and cellular assays, we investigated the influence of OSBPL7 deficiency on podocytes. We demonstrated that reduced renal OSBPL7 levels as observed in two different models of experimental CKD are linked to increased podocyte apoptosis, primarily mediated by heightened endoplasmic reticulum (ER) stress. Although as expected, the absence of OSBPL7 also resulted in lipid dysregulation (increased lipid droplets and triglycerides content), OSBPL7 deficiency-related lipid dysmetabolism did not contribute to podocyte injury. Similarly, we demonstrated that the decreased autophagic flux we observed in OSBPL7-deficient podocytes was not the mechanistic link between OSBPL7 deficiency and apoptosis. In a complementary zebrafish model, osbpl7 knockdown was sufficient to induce proteinuria and morphological damage to the glomerulus, underscoring its physiological relevance. Our study sheds new light on the mechanistic link between OSBPL7 deficiency and podocyte injury in glomerular diseases associated with CKD, and it strengthens the role of OSBPL7 as a novel therapeutic target.NEW & NOTEWORTHY OSBPL7 and ER stress comprise a central mechanism in glomerular injury. This study highlights a crucial link between OSBPL7 deficiency and ER stress in CKD. OSBPL7 deficiency causes ER stress, leading to podocyte apoptosis. There is a selective effect on lipid homeostasis in that OSBPL7 deficiency affects lipid homeostasis, altering cellular triglyceride but not cholesterol content. The interaction of ER stress and apoptosis supports that ER stress, not reduced autophagy, is the main driver of apoptosis in OSBPL7-deficient podocytes.

Biallelic ANKS6 mutations cause late-onset ciliopathy with chronic kidney disease through YAP dysregulation.

Nephronophthisis-related ciliopathies (NPHP-RC) comprises a group of inherited kidney diseases, caused by mutations in genes encoding proteins localizing to primary cilia. NPHP-RC represents one of the most frequent monogenic causes of renal failure within the first three decades of life, but its molecular disease mechanisms remain unclear. Here, we identified biallelic ANKS6 mutations in two affected siblings with late-onset chronic kidney disease by whole-exome sequencing. We employed patient-derived fibroblasts generating an in vitro model to study the precise biological impact of distinct human ANKS6 mutations, completed by immunohistochemistry studies on renal biopsy samples. Functional studies using patient-derived cells showed an impaired integrity of the ciliary inversin compartment with reduced cilia length. Further analyses demonstrated that ANKS6 deficiency leads to a dysregulation of Hippo-signaling through nuclear yes-associated protein (YAP) imbalance and disrupted ciliary localization of YAP. In addition, an altered transcriptional activity of canonical Wnt target genes and altered expression of non-phosphorylated (active) ß-catenin and phosphorylated glycogen synthase kinase 3ß were observed. Upon ciliation, ANKS6 deficiency revealed a deranged subcellular localization and expression of components of the endocytic recycling compartment. Our results demonstrate that ANKS6 plays a key role in regulating the Hippo pathway, and ANKS6 deficiency is linked to dysregulation of signaling pathways. Our study provides molecular clues in understanding pathophysiological mechanisms of NPHP-RC and may offer new therapeutic targets.

Pancreas transplantation as rescue therapy in a patient with type 1 diabetes and concurrent subcutaneous insulin resistance.

Patients with type 1 diabetes and concurrent subcutaneous insulin resistance present unique diagnostic and therapeutic challenges for clinicians. The standard therapeutic approach is the administration of intravenous insulin. Pancreatic transplantation should be considered at an appropriate time, particularly in the event of life-threatening ketoacidosis, hyperglycemia, hypoglycemia, catheter-associated thrombosis, and infections. We present the case of a 24-year-old woman with type 1 diabetes since early childhood and increasingly uncontrollable subcutaneous and intramuscular insulin resistance. Furthermore, we present the diagnostic pathway and therapeutic interventions performed, culminating in pancreatic transplantation as a curative approach. Immediate graft function resulted in optimal glycemic control.

Is GFR decline induced by SGLT2 inhibitor of clinical importance?

BACKGROUND: Use of sodium-glucose-cotransporter-2 (SGLT2) inhibitors often causes an initial decline in glomerular filtration rate (GFR). This study addresses the question whether the initial decline of renal function with SGLT2 inhibitor treatment is related to vascular changes in the systemic circulation. METHODS: We measured GFR (mGFR) and estimated GFR (eGFR) in 65 patients with type 2 diabetes (T2D) at baseline and after 12 weeks of treatment randomized either to a combination of empagliflozin and linagliptin (SGLT2 inhibitor based treatment group) (n = 34) or metformin and insulin (non-SGLT2 inhibitor based treatment group) (n = 31). mGFR was measured using the gold standard clearance technique by constant infusion of inulin. In addition to blood pressure (BP), we measured pulse wave velocity (PWV) under standardized conditions reflecting vascular compliance of large arteries, as PWV is considered to be one of the most reliable vascular parameter of cardiovascular (CV) prognosis. RESULTS: Both mGFR and eGFR decreased significantly after initiating treatment, but no correlation was found between change in mGFR and change in eGFR in either treatment group (SGLT2 inhibitor based treatment group: r=-0.148, p = 0.404; non-SGLT2 inhibitor based treatment group: r = 0.138, p = 0.460). Noticeably, change in mGFR correlated with change in PWV (r = 0.476, p = 0.005) in the SGLT2 inhibitor based treatment group only and remained significant after adjustment for the change in systolic BP and the change in heart rate (r = 0.422, p = 0.018). No such correlation was observed between the change in eGFR and the change in PWV in either treatment group. CONCLUSIONS: Our main finding is that after initiating a SGLT2 inhibitor based therapy an exaggerated decline in mGFR was related with improved vascular compliance of large arteries reflecting the pharmacologic effects of SGLT2 inhibitor in the renal and systemic vascular bed. Second, in a single patient with T2D, eGFR may not be an appropriate parameter to assess the true change of renal function after receiving SGLT2 inhibitor based therapy. TRIAL REGISTRATION: clinicaltrials.gov (NCT02752113).

Relation between waist circumference and the renal hemodynamic in healthy individuals.

BACKGROUND AND AIMS: Obesity has been shown to be an independent risk factor for the development of CKD. Little is known about pathways of interaction of visceral fat mass estimated by waist circumference (WC) and metabolic factors with the renal and intraglomerular hemodynamic profile in healthy, non-obese individuals. METHODS AND RESULTS: The study population of this post-hoc analysis in 80 healthy individuals, who participated in a randomized, controlled clinical trial (www. CLINICALTRIALS: gov: NCT02783456) was divided into two groups based on median of WC (high WC and low WC group). Renal hemodynamic profiles were analyzed using steady state input clearance (infusion of para-amino-hippuric acid and inulin). Intraglomerular pressure (IGP) and resistances of the afferent (RA) and efferent (RE) arterioles were calculated (Gomez equation). The analysis included healthy, non-smoking individuals, aged 27 ± 9 years with median WC of 84.75 ± 9 cm. Glomerular filtration rate (GFR) (110 ± 15 vs. 127 ± 16 ml/min/m2, p < 0.001), renal plasma flow (RPF) (620 ± 109 vs. 700 ± 104 ml/min, p = 0.001) and IGP (36.7 ± 2.3 vs. 38.5 ± 3.1 mmHg, p = 0.003) were lower in the high WC compared to the low WC group. Patients in the high WC group showed higher renal vascular resistance (RVR) (85 ± 19 vs. 70 ± 12 mmHg/(ml/min), p < 0.001), higher RA (4034 ± 1177 vs. 3069 ± 786 dyn∗s/cm5, p < 0.001) and higher RE (2283 ± 339 vs. 2118 ± 280 dyn∗s/cm5, p = 0.021) compared to the low WC group. Individuals in the high WC group showed higher leptin levels (p = 0.003) and higher HOMA-IR (p = 0.024) compared to the low WC group. CONCLUSION: Increased WC in healthy young individuals was associated with reduced GFR and RPF likely mediated by increased RVR.

Spot urinary sodium in CKD patients: correlation with 24h-excretion and evaluation of commonly used prediction equations.

BACKGROUND: Salt intake in CKD patients can affect cardiovascular risk and kidney disease progression. Twenty-four hour (24h) urine collections are often used to investigate salt metabolism but are cumbersome to perform. We assessed urinary sodium (U-Na) concentration in spot urine samples and investigated the correlation with 24h U-Na excretion and concentration in CKD patients under nephrological care. Further, we studied the role of CKD stage and diuretics and evaluated the performance of commonly used formulas for the prediction of 24h U-Na excretion from spot urine samples. METHODS: One hundred eight patients of the German Chronic Kidney Disease (GCKD) study were included. Each participant collected a 24h urine and two spot urine samples within the same period. The first spot urine sample (AM) was part of the second morning urine. The second urine sample was collected before dinner (PM). Patients were advised to take their medication as usual without changing dietary habits. U-Na concentrations in the two spot urine samples and their average ((AM + PM)/2) were correlated with U-Na concentration and total Na excretion in the 24h urine collections. Correlations were subsequently studied after stratification by CKD stage and diuretic intake. The usefulness of three commonly applied equations to estimate 24h U-Na excretion from spot urine samples (Kawasaki, Tanaka and Intersalt) was determined using Bland-Altman plots, analyses of sensitivity, specificity, as well as positive (PPV) and negative predictive values (NPV). RESULTS: Participants (42 women, 66 men) were on average (± SD) 62.2 (± 11.9) years old, with a mean serum creatinine of 1.6 (± 0.5) mg/dl. 95% had arterial hypertension, 37% diabetes mellitus and 55% were on diuretics. The best correlation with 24h U-Na total excretion was found for the PM spot U-Na sample. We also found strong correlations when comparing spot and 24h urine U-Na concentration. Correction of spot U-Na for U-creatinine did not improve strength of correlations. Neither CKD stage, nor intake of diuretics had significant impact on these correlations. All examined formulas revealed a significant mean bias. The lowest mean bias and the strongest correlation between estimated and measured U-Na excretion in 24h were obtained using the Tanaka-formula. Also, application of the Tanaka-formula with PM U-Na provided best sensitivity, specificity, PPV and NPV to estimate U-Na excretion > 4g/d corresponding to a salt consumption > 10g/d. CONCLUSION: U-Na concentration of spot urine samples correlated with 24h U-Na excretion especially when PM spot U-Na was used. However, correlation coefficients were relatively low. Neither CKD stage nor intake of diuretics appeared to have an influence on these correlations. There was a significant bias for all tested formulas with the Tanaka-formula providing the strongest correlation with measured 24h U-Na excretion. In summary, using spot urine samples together with the Tanaka-formula in epidemiological studies appears feasible to determine associations between approximate salt intake and outcomes in CKD patients. However, the usefulness of spot-urine samples to guide and monitor salt consumption in individual patients remains limited.

Hypoxia and renal fibrosis.

Renal fibrosis is the final stage of most progressive kidney diseases. Chronic kidney disease (CKD) is associated with high comorbidity and mortality. Thus, preventing fibrosis and thereby preserving kidney function increases the quality of life and prolongs the survival of patients with CKD. Many processes such as inflammation or metabolic stress modulate the progression of kidney fibrosis. Hypoxia has also been implicated in the pathogenesis of renal fibrosis, and oxygen sensing in the kidney is of outstanding importance for the body. The dysregulation of oxygen sensing in the diseased kidney is best exemplified by the loss of stimulation of erythropoietin production from interstitial cells in the fibrotic kidney despite anemia. Furthermore, hypoxia is present in acute or chronic kidney diseases and may affect all cell types present in the kidney including tubular and glomerular cells as well as resident immune cells. Pro- and antifibrotic effects of the transcription factors hypoxia-inducible factors 1 and 2 have been described in a plethora of animal models of acute and chronic kidney diseases, but recent advances in sequencing technologies now allow for novel and deeper insights into the role of hypoxia and its cell type-specific effects on the progression of renal fibrosis, especially in humans. Here, we review existing literature on how hypoxia impacts the development and progression of renal fibrosis.

The renal cancer risk allele at 14q24.2 activates a novel hypoxia-inducible transcription factor-binding enhancer of DPF3 expression.

Evolution of clear cell renal cell carcinoma is guided by dysregulation of hypoxia-inducible transcription factor (HIF) pathways following loss of the von Hippel-Lindau tumor suppressor protein. Renal cell carcinoma (RCC)-associated polymorphisms influence HIF-DNA interactions at enhancers of important oncogenes thereby modulating the risk of developing renal cancer. A strong signal of genome-wide association with RCC was determined for the single nucleotide polymorphism (SNP) rs4903064, located on chr14q.24.2 within an intron of DPF3, encoding for Double PHD Fingers 3, a member of chromatin remodeling complexes; however, it is unclear how the risk allele operates in renal cells. In this study, we used tissue specimens and primary renal cells from a large cohort of RCC patients to examine the function of this polymorphism. In clear cell renal cell carcinoma tissue, isolated tumor cells as well as in primary renal tubular cells, in which HIF was stabilized, we determined genotype-specific increases of DPF3 mRNA levels and identified that the risk SNP resides in an active enhancer region, creating a novel HIF-binding motif. We then confirmed allele-specific HIF binding to this locus using chromatin immunoprecipitation of HIF subunits. Consequentially, HIF-mediated DPF3 regulation was dependent on the presence of the risk allele. Finally, we show that DPF3 deletion in proximal tubular cells retarded cell growth, indicating potential roles for DPF3 in cell proliferation. Our analyses suggest that the HIF pathway differentially operates on a SNP-induced hypoxia-response element at 14q24.2, thereby affecting DPF3 expression, which increases the risk of developing renal cancer.

Afferent neurons of the kidney with impaired firing pattern in inflammation - role of sodium currents?

Peripheral neurons with renal afferents exhibit a predominantly tonic firing pattern of higher frequency that is reduced to low frequencies (phasic firing pattern) in renal inflammation. We wanted to test the hypothesis that the reduction in firing activity during inflammation is due to high-activity tonic neurons switching from higher to low frequencies depending on altered sodium currents. We identified and cultivated afferent sensory neurons with renal projections from the dorsal root ganglia (Th11-L2). Cultivated neurons were incubated with the chemokine CXCL1 (1,5 nmol/ml) for 12 h. We characterized neurons as "tonic," i.e., sustained action potential (AP) firing, or "phasic," i.e., < 5 APs upon stimulation in the current clamp. Their membrane currents were investigated in a voltage clamp. Data analyzed: renal vs. non-renal and tonic vs. phasic neurons. Renal afferent neurons exposed to CXCL1 showed a decrease in tonic firing pattern (CXCL1: 35,6% vs. control: 57%, P < 0.05). Na+ and K+ currents were not different between control renal and non-renal DRG neurons. Phasic neurons exhibited higher Na+ and K+ currents than tonic resulting in shorter APs (3.7 ± 0.3 vs. 6.1 ± 0.6 ms, P < 0.01). In neurons incubated with CXCL1, Na+ and K+ peak current density increased in phasic (Na+: - 969 ± 47 vs. - 758 ± 47 nA/pF, P < 0.01; K+: 707 ± 22 vs. 558 ± 31 nA/pF, P < 0.01), but were unchanged in tonic neurons. Phasic neurons exposed to CXCL1 showed a broader range of Na+ currents ([- 365- - 1429 nA] vs. [- 412- - 4273 nA]; P < 0.05) similar to tonic neurons. After CXCL1 exposure, significant changes in phasic neurons were observed in sodium activation/inactivation as well as a wider distribution of Na+ currents characteristic of tonic neurons. These findings indicate a subgroup of tonic neurons besides mere tonic or phasic neurons exists able to exhibit a phasic activity pattern under pathological conditions.

Hypoxia hits APOL1 in the kidney.

Individuals of African ancestry carrying two pathogenic variants of apolipoprotein 1 (APOL1) have a substantially increased risk for developing chronic kidney disease. The course of APOL1 nephropathy is extremely heterogeneous and shaped by systemic factors such as a response to interferon. However, additional environmental factors operating in this second-hit model have been less well defined. Here, we reveal that stabilization of hypoxia-inducible transcription factors (HIF) by hypoxia or HIF prolyl hydroxylase inhibitors activates transcription of APOL1 in podocytes and tubular cells. An active regulatory DNA-element upstream of APOL1 that interacted with HIF was identified. This enhancer was accessible preferentially in kidney cells. Importantly, upregulation of APOL1 by HIF was additive to the effects of interferon. Furthermore, HIF stimulated expression of APOL1 in tubular cells derived from the urine of an individual carrying a risk variant for kidney disease. Thus, hypoxic insults may serve as important modulators of APOL1 nephropathy.

A paired-kidney allocation study found superior survival with HLA-DR compatible kidney transplants in the Eurotransplant Senior Program.

The Eurotransplant Senior Program (ESP) has expedited the chance for elderly patients with kidney failure to receive a timely transplant. This current study evaluated survival parameters of kidneys donated after brain death with or without matching for HLA-DR antigens. This cohort study evaluated the period within ESP with paired allocation of 675 kidneys from donors 65 years and older to transplant candidates 65 years and older, the first kidney to 341 patients within the Eurotransplant Senior DR-compatible Program and 334 contralateral kidneys without (ESP) HLA-DR antigen matching. We used Kaplan-Meier estimates and competing risk analysis to assess all cause mortality and kidney graft failure, respectively. The log-rank test and Cox proportional hazards regression were used for comparisons. Within ESP, matching for HLA-DR antigens was associated with a significantly lower five-year risk of mortality (hazard ratio 0.71; 95% confidence interval 0.53-0.95) and significantly lower cause-specific hazards for kidney graft failure and return to dialysis at one year (0.55; 0.35-0.87) and five years (0.73; 0.53-0.99) post-transplant. Allocation based on HLA-DR matching resulted in longer cold ischemia (mean difference 1.00 hours; 95% confidence interval: 0.32-1.68) and kidney offers with a significantly shorter median dialysis vintage of 2.4 versus 4.1 yrs. in ESP without matching. Thus, our allocation based on HLA-DR matching improved five-year patient and kidney allograft survival. Hence, our paired allocation study suggests a superior outcome of HLA-DR matching in the context of old-for-old kidney transplantation.

Partner, Neighbor, Housekeeper and Dimension: 3D versus 2D Glomerular Co-Cultures Reveal Drawbacks of Currently Used Cell Culture Models.

Signaling-pathway analyses and the investigation of gene responses to different stimuli are usually performed in 2D monocultures. However, within the glomerulus, cells grow in 3D and are involved in direct and paracrine interactions with different glomerular cell types. Thus, the results from 2D monoculture experiments must be taken with caution. We cultured glomerular endothelial cells, podocytes and mesangial cells in 2D/3D monocultures and 2D/3D co-cultures and analyzed cell survival, self-assembly, gene expression, cell-cell interaction, and gene pathways using live/dead assay, time-lapse analysis, bulk-RNA sequencing, qPCR, and immunofluorescence staining. Without any need for scaffolds, 3D glomerular co-cultures self-organized into spheroids. Podocyte- and glomerular endothelial cell-specific markers and the extracellular matrix were increased in 3D co-cultures compared to 2D co-cultures. Housekeeping genes must be chosen wisely, as many genes used for the normalization of gene expression were themselves affected in 3D culture conditions. The transport of podocyte-derived VEGFA to glomerular endothelial cells confirmed intercellular crosstalk in the 3D co-culture models. The enhanced expression of genes important for glomerular function in 3D, compared to 2D, questions the reliability of currently used 2D monocultures. Hence, glomerular 3D co-cultures might be more suitable in the study of intercellular communication, disease modelling and drug screening ex vivo.

Diverse molecular causes of unsolved autosomal dominant tubulointerstitial kidney diseases.

Autosomal Dominant Tubulointerstitial Kidney Disease (ADTKD) is caused by mutations in one of at least five genes and leads to kidney failure usually in mid adulthood. Throughout the literature, variable numbers of families have been reported, where no mutation can be found and therefore termed ADTKD-not otherwise specified. Here, we aim to clarify the genetic cause of their diseases in our ADTKD registry. Sequencing for all known ADTKD genes was performed, followed by SNaPshot minisequencing for the dupC (an additional cytosine within a stretch of seven cytosines) mutation of MUC1. A virtual panel containing 560 genes reported in the context of kidney disease (nephrome) and exome sequencing were then analyzed sequentially. Variants were validated and tested for segregation. In 29 of the 45 registry families, mutations in known ADTKD genes were found, mostly in MUC1. Sixteen families could then be termed ADTKD-not otherwise specified, of which nine showed diagnostic variants in the nephrome (four in COL4A5, two in INF2 and one each in COL4A4, PAX2, SALL1 and PKD2). In the other seven families, exome sequencing analysis yielded potential disease associated variants in novel candidate genes for ADTKD; evaluated by database analyses and genome-wide association studies. For the great majority of our ADTKD registry we were able to reach a molecular genetic diagnosis. However, a small number of families are indeed affected by diseases classically described as a glomerular entity. Thus, incomplete clinical phenotyping and atypical clinical presentation may have led to the classification of ADTKD. The identified novel candidate genes by exome sequencing will require further functional validation.

Successful treatment of COVID-19 infection with convalescent plasma in B-cell-depleted patients may promote cellular immunity.

Treatment with convalescent plasma has been shown to be safe in coronavirus disease in 2019 (COVID-19) infection, although efficacy reported in immunocompetent patients varies. Nevertheless, neutralizing antibodies are a key requisite in the fight against viral infections. Patients depleted of antibody-producing B cells, such as those treated with rituximab (anti-CD20) for hematological malignancies, lack a fundamental part of their adaptive immunity. Treatment with convalescent plasma appears to be of general benefit in this particularly vulnerable cohort. We analyzed clinical course and inflammation markers of three B-cell-depleted patients suffering from COVID-19 who were treated with convalescent plasma. In addition, we measured serum antibody levels as well as peripheral blood CD38/HLA-DR-positive T-cells ex vivo and CD137-positive T-cells after in vitro stimulation with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-derived peptides in these patients. We observed that therapy with convalescent plasma was effective in all three patients and analysis of CD137-positive T-cells after stimulation with SARS-CoV-2 peptides showed an increase in peptide-specific T-cells after application of convalescent plasma. In conclusion, we here demonstrate efficacy of convalescent plasma therapy in three B-cell-depleted patients and present data that suggest that while application of convalescent plasma elevates systemic antibody levels only transiently, it may also boost specific T-cell responses.

Hemodialysis Patients with Cardiovascular Disease Reveal Increased Tissue Na+ Deposition.

BACKGROUND: The relationship between Na+ balance and cardiovascular disease (CVD) in hemodialysis (HD) patients is not yet fully understood. We hypothesized that HD patients co-diagnosed with CVD show increased tissue Na+ accumulation compared to HD patients without CVD. METHODS: In our observational study, 52 HD patients were divided into a group with (23 subjects) or without (29 subjects) a positive history of cardiovascular events. We used 23Na-magnetic resonance imaging (23Na-MRI) at 3.0 Tesla to quantify Na+ content in skin and muscle of both groups directly before and after HD. Additionally, total body fluid distribution was determined by bioimpedance spectroscopy (BIS) and laboratory parameters were assessed. RESULTS: Compared to HD patients without CVD, 23Na-MRI detected an increased Na+ content in skin (21.7 ± 7.3 vs. 30.2 ± 9.8 arbitrary units (a.u.), p < 0.01) and muscle tissue (21.5 ± 3.6 vs. 24.7 ± 6.0 a.u., p < 0.05) in patients with previous CVD events. Simultaneously measured fluid amount by BIS, includingexcess extracellular water (1.8 ± 1.7 vs. 2.2 ± 1.7 L, p = 0.44), was not significantly different between both groups. Tissue Na+ accumulation in HD-CVD patients was paralleled by a higher plasma concentration of the inflammation marker interleukin-6 (5.1, IQR 5.8 vs. 8.5, IQR 7.9 pg/mL, p < 0.05). CONCLUSION: In our cohort, HD patients with CVD showed higher tissue Na+ content than HD patients without CVD, while no difference in body water distribution could be detected between both groups. Our findings provide evidence that the history of a cardiovascular event is associated with disturbances in tissue Na+ content in HD patients.

Transplant Ureteral Stenosis after Renal Transplantation: Risk Factor Analysis.

INTRODUCTION: The results of kidney transplants have improved dramatically in recent years, leading to reduced morbidity and mortality. Despite continuous improvements, urological complications occur at a rate of 2.6%-15%. Ureteral stenosis of graft ureters is the most common complication, with a probability of 0.5%-6.3%. This study aimed to determine the incidence of ureteral stenosis after kidney transplantation and identify risk factors that distinguish transplant patients with and without ureteral stenosis. METHODS: This study retrospectively analyzed patients who had undergone kidney transplantation at the Department of Urology of the Friedrich-Alexander University Erlangen-Nuremberg between 2001 and 2015. Forty-seven patients developed ureteral stenosis during the operation. Most of the ureteral stenosis cases occurred in the first 4 months after transplantation. Kaplan-Meier analysis and the log-rank test were used to calculate the cumulative risk, and the Mann-Whitney U test was used nonparametrically. The significance level was set at p < 0.05. RESULTS: Statistical analysis showed that residual diuresis (p = 0.008), cold ischemia time (CIT) (p = 0.040), the body mass index (p = 0.027), and donor serum creatinine value (p = 0.039) showed a significantly different distribution between recipients with or without ureteral stenosis after kidney transplantation. In multivariate Cox's regression modeling, residual diuresis and the donor serum creatinine level were identified as the only independent predictors of patients' stenosis-free survival. CONCLUSION: Urological complications not diagnosed and treated in time endanger the success of kidney transplantation. After evaluating the kidney transplantation data of the patients at the Transplant Center Erlangen-Nuremberg from 2001 to 2015, residual diuresis, CIT, the body mass index, and donor serum creatinine value were found to influence the development of ureteral stenosis.

Glomerular Endothelial Cell-Derived microRNA-192 Regulates Nephronectin Expression in Idiopathic Membranous Glomerulonephritis.

BACKGROUND: Autoantibodies binding to podocyte antigens cause idiopathic membranous glomerulonephritis (iMGN). However, it remains elusive how autoantibodies reach the subepithelial space because the glomerular filtration barrier (GFB) is size selective and almost impermeable for antibodies. METHODS: Kidney biopsies from patients with iMGN, cell culture, zebrafish, and mouse models were used to investigate the role of nephronectin (NPNT) regulating microRNAs (miRs) for the GFB. RESULTS: Glomerular endothelial cell (GEC)-derived miR-192-5p and podocyte-derived miR-378a-3p are upregulated in urine and glomeruli of patients with iMGN, whereas glomerular NPNT is reduced. Overexpression of miR-192-5p and morpholino-mediated npnt knockdown induced edema, proteinuria, and podocyte effacement similar to podocyte-derived miR-378a-3p in zebrafish. Structural changes of the glomerular basement membrane (GBM) with increased lucidity, splitting, and lamellation, especially of the lamina rara interna, similar to ultrastructural findings seen in advanced stages of iMGN, were found. IgG-size nanoparticles accumulated in lucidity areas of the lamina rara interna and lamina densa of the GBM in npnt-knockdown zebrafish models. Loss of slit diaphragm proteins and severe structural impairment of the GBM were further confirmed in podocyte-specific Npnt knockout mice. GECs downregulate podocyte NPNT by transfer of miR-192-5p-containing exosomes in a paracrine manner. CONCLUSIONS: Podocyte NPNT is important for proper glomerular filter function and GBM structure and is regulated by GEC-derived miR-192-5p and podocyte-derived miR-378a-3p. We hypothesize that loss of NPNT in the GBM is an important part of the initial pathophysiology of iMGN and enables autoantigenicity of podocyte antigens and subepithelial immune complex deposition in iMGN.

Frequency of the necessity of dentoalveolar surgery or conservative treatment in patients before kidney transplantation depending on the duration of dialysis and causative nephrological disease.

OBJECTIVES: This retrospective study evaluates intraoral surgical and conservative treatment need in patients with a chronic kidney end-stage disease, depending on the duration of dialysis treatment and the causative nephrological disease. MATERIAL AND METHODS: This study is based on data of patients referred to the Department of Oral and Maxillofacial Surgery of the University Hospital Erlangen, Germany, prior to kidney transplantation between January 2015 and March 2020. The necessity for oral surgical or dental therapy was determined by clinical and radiological examinations. Data on renal replacement therapy, cause of underlying renal disease, lifestyle, and general health were collected. RESULTS: Data of N = 89 patients demonstrated that surgical treatment need depends on dialysis duration (p = 0.042). Patients, who had been dialyzing for 2 to 3 years showed the highest need for surgical intervention (80.0%; p = 0.024), followed by dialysis patients with a dialysis time of more than 3 years (48.1%). Similarly, dialysis patients in the second or third year of dialysis had the highest need for conservative treatment (73.3%; p > 0.05), followed by 55.6% of dialysis patients in the third year of dialysis. CONCLUSIONS: Operative and conservative treatment is essential to optimize subsequent kidney transplantation. The greatest necessity could be detected for patients in the second and third years of dialysis. CLINICAL RELEVANCE: Oral health addressing surgical and conservative treatment need depends on the duration of dialysis in patients with a chronic kidney end-stage disease.

Glomerular Endothelial Cell-Derived miR-200c Impairs Glomerular Homeostasis by Targeting Podocyte VEGF-A.

Deciphering the pathophysiological mechanisms of primary podocytopathies that can lead to end-stage renal disease and increased mortality is an unmet need. Studying how microRNAs (miRs) interfere with various signaling pathways enables identification of pathomechanisms, novel biomarkers and potential therapeutic options. We investigated the expression of miR-200c in urine from patients with different renal diseases as a potential candidate involved in podocytopathies. The role of miR-200c for the glomerulus and its potential targets were studied in cultured human podocytes, human glomerular endothelial cells and in the zebrafish model. miR-200c was upregulated in urine from patients with minimal change disease, membranous glomerulonephritis and focal segmental glomerulosclerosis and also in transforming growth factor beta (TGF-ß) stressed glomerular endothelial cells, but not in podocytes. In zebrafish, miR-200c overexpression caused proteinuria, edema, podocyte foot process effacement and glomerular endotheliosis. Although zinc finger E-Box binding homeobox 1/2 (ZEB1/2), important in epithelial to mesenchymal transition (EMT), are prominent targets of miR-200c, their downregulation did not explain our zebrafish phenotype. We detected decreased vegfaa/bb in zebrafish overexpressing miR-200c and could further prove that miR-200c decreased VEGF-A expression and secretion in cultured human podocytes. We hypothesize that miR-200c is released from glomerular endothelial cells during cell stress and acts in a paracrine, autocrine, as well as context-dependent manner in the glomerulus. MiR-200c can cause glomerular damage most likely due to the reduction of podocyte VEGF-A. In contrast, miR-200c might also influence ZEB expression and therefore EMT, which might be important in other conditions. Therefore, we propose that miR-200c-mediated effects in the glomerulus are context-sensitive.