Potentially inappropriate medication in patients with chronic kidney disease and elderly patients.

BACKGROUND: Most patients with chronic kidney disease (CKD) are old, comorbid, and subjected to polypharmacy. This study describes prevalence and predictors of potentially inappropriate medication (PIM) in CKD patients. MATERIALS AND METHODS: Medication plans of CKD patients of the "Greifswald Approach to Individualized Medicine" cross-sectional study (GANI_MED) were checked for PIM based on kidney function (PIM-K) and PIM for elderly patients (PIM-E). PIM-K were defined by prescription instructions of product labeling. PIM-E were defined by BEERS, -PRISCUS, and FORTA criteria. Predictors for PIM were identified through multiple stepwise regression. RESULTS: 375 patients were included (age: 67.9 ± 13.5 years; estimated glomerular filtration rate (eGFR): 23.3 ± 18.6 mL/min/1.73m2; prescriptions: 11.1 ± 4.7). 44.5% of all CKD patients had PIM-K, and 43.2 to 79.0% of all elderly patients had PIM-E. Polypharmacy and reduced eGFR were predictors for PIM. The risk for PIM-K was increased by 3.8 (95% confidence interval (CI): 1.5 - 9.6) with 10 or more prescriptions and by 8.7 (95% CI: 1.3 - 58.5) with an eGFR below 30 mL/min/1.73m2. On average, elderly patients with 10 or more prescriptions had 3.0 ± 1.7 PIM-E. CONCLUSION: Polypharmacy, PIM-K, and PIM-E affect many CKD patients and can lead to adverse events. Deprescribing and targeted prescribing may improve the outcome of CKD patients and elderly patients.

Studies on the Role of the Transcription Factor Tcf21 in the Transdifferentiation of Parietal Epithelial Cells into Podocyte-Like Cells.

BACKGROUND/AIMS: Podocyte differentiation is essential for proper blood filtration in the kidney. It is well known that transcription factors play an essential role to maintain the differentiation of podocytes. The present study is focused on the basic helix-loop-helix (bHLH) transcription factor Tcf21 (Pod1) which is essential for the development of podocytes in vivo. Since parietal epithelial cells (PECs) are still under debate to be progenitor cells which can differentiate into podocytes, we wanted to find out whether the expression of Tcf21 induces a transition of PECs into podocytes. METHODS: We transfected PECs with Tcf21-GFP and analyzed the expression of PEC- and podocyte-specific markers. Furthermore, we performed ChIP-Seq analysis to identify new putative interaction partners and target genes of Tcf21. RESULTS: By gene arrays analysis, we found that podocytes express high levels of Tcf21 in vivo in contrast to cultured podocytes and parietal epithelial cells (PECs) in vitro. After the expression of Tcf21 in PECs, we observed a downregulation of specific PEC markers like caveolin­1, ß-catenin and Pax2. Additionally, we found that the upregulation of Tcf21 induced multi-lobulation of cell nuclei, budding and a formation of micronuclei (MBM). Furthermore, a high number of PECs showed a tetraploid set of chromosomes. By qRT-PCR and Western blot analysis, we revealed that the transcription factor YY1 is downregulated by Tcf21. Interestingly, co-expression of YY1 and Tcf21 rescues MBM and reduced tetraploidy. By ChIP-Seq analysis, we identified a genome-wide Tcf21-binding site (CAGCTG), which matched the CANNTG sequence, a common E-box binding motif used by bHLH transcription factors. Using this technique, we identified additional Tcf21 targets genes that are involved in the regulation of the cell cycle (e.g. Mdm2, Cdc45, Cyclin D1, Cyclin D2), on the stability of microtubules (e.g. Mapt) as well as chromosome segregation. CONCLUSION: Taken together, we demonstrate that Tcf21 inhibits the expression of PEC-specific markers and of the transcription factor YY1, induces MBM as well as regulates the cell cycle suggesting that Tcf21 might be important for PEC differentiation into podocyte-like cells.

Meta-analysis uncovers genome-wide significant variants for rapid kidney function decline.

Rapid decline of glomerular filtration rate estimated from creatinine (eGFRcrea) is associated with severe clinical endpoints. In contrast to cross-sectionally assessed eGFRcrea, the genetic basis for rapid eGFRcrea decline is largely unknown. To help define this, we meta-analyzed 42 genome-wide association studies from the Chronic Kidney Diseases Genetics Consortium and United Kingdom Biobank to identify genetic loci for rapid eGFRcrea decline. Two definitions of eGFRcrea decline were used: 3 mL/min/1.73m2/year or more ("Rapid3"; encompassing 34,874 cases, 107,090 controls) and eGFRcrea decline 25% or more and eGFRcrea under 60 mL/min/1.73m2 at follow-up among those with eGFRcrea 60 mL/min/1.73m2 or more at baseline ("CKDi25"; encompassing 19,901 cases, 175,244 controls). Seven independent variants were identified across six loci for Rapid3 and/or CKDi25: consisting of five variants at four loci with genome-wide significance (near UMOD-PDILT (2), PRKAG2, WDR72, OR2S2) and two variants among 265 known eGFRcrea variants (near GATM, LARP4B). All these loci were novel for Rapid3 and/or CKDi25 and our bioinformatic follow-up prioritized variants and genes underneath these loci. The OR2S2 locus is novel for any eGFRcrea trait including interesting candidates. For the five genome-wide significant lead variants, we found supporting effects for annual change in blood urea nitrogen or cystatin-based eGFR, but not for GATM or LARP4B. Individuals at high compared to those at low genetic risk (8-14 vs. 0-5 adverse alleles) had a 1.20-fold increased risk of acute kidney injury (95% confidence interval 1.08-1.33). Thus, our identified loci for rapid kidney function decline may help prioritize therapeutic targets and identify mechanisms and individuals at risk for sustained deterioration of kidney function.

Adriamycin does not damage podocytes of zebrafish larvae.

Podocytes are highly specialized epithelial cells that are essential for an intact glomerular filtration barrier in the kidney. Several glomerular diseases like focal segmental glomerulosclerosis (FSGS) are initially due to podocyte injury and loss. Since causative treatments for FSGS are not available until today, drug screening is of great relevance. In order to test a high number of drugs, FSGS needs to be reliably induced in a suitable animal model. The zebrafish larva is an ideal model for kidney research due to the vast amount of offsprings, the rapid development of a simple kidney and a remarkable homology to the mammalian glomerulus. Zebrafish larvae possess a size-selective glomerular filtration barrier at 4 days post fertilization including podocytes with interdigitating foot processes that are connected by a slit membrane. Adriamycin is an anthracycline which is often used in mice and rats to induce a FSGS-like phenotype. In this study, we aimed to induce a similar phenotype to zebrafish larvae by adding adriamycin to the tank water in different concentrations. Surprisingly, zebrafish larvae did not develop glomerular injury and displayed an intact filtration barrier after treatment with adriamycin. This was shown by (immuno-) histology, our filtration assay, in vivo imaging by 2-photon microcopy, RT-(q)PCR as well as transmission electron microscopy. To summarize, adriamycin is unable to induce a podocyte-related damage in zebrafish larvae and therefore major effort must be made to establish FSGS in zebrafish larvae to identify effective drugs by screenings.

Prolonged podocyte depletion in larval zebrafish resembles mammalian focal and segmental glomerulosclerosis.

Focal and segmental glomerulosclerosis (FSGS) is a histological pattern frequently found in patients with nephrotic syndrome that often progress to end-stage kidney disease. The initial step in development of this histologically defined entity is injury and ultimately depletion of podocytes, highly arborized interdigitating cells on the glomerular capillaries with important function for the glomerular filtration barrier. Since there are still no causal therapeutic options, animal models are needed to develop new treatment strategies. Here, we present an FSGS-like model in zebrafish larvae, an eligible vertebrate model for kidney research. In a transgenic zebrafish strain, podocytes were depleted, and the glomerular response was investigated by histological and morphometrical analysis combined with immunofluorescence staining and ultrastructural analysis by transmission electron microscopy. By intravenous injection of fluorescent high-molecular weight dextran, we confirmed leakage of the size selective filtration barrier. Additionally, we observed severe podocyte foot process effacement of remaining podocytes, activation of proximal tubule-like parietal epithelial cells identified by ultrastructural cytomorphology, and expression of proximal tubule markers. These activated cells deposited extracellular matrix on the glomerular tuft which are all hallmarks of FSGS. Our findings indicate that glomerular response to podocyte depletion in larval zebrafish resembles human FSGS in several important characteristics. Therefore, this model will help to investigate the disease development and the effects of potential drugs in a living organism.

Expression of Slc35f1 in the murine brain.

The solute carrier (SLC) group of membrane transport proteins includes about 400 members organized into more than 50 families. The SLC family that comprises nucleoside-sugar transporters is referred to as SLC35. One of the members of this family is SLC35F1. The function of SLC35F1 is still unknown; however, recent studies demonstrated that SLC35F1 mRNA is highly expressed in the brain and in the kidney. Therefore, we examine the distribution of Slc35f1 protein in the murine forebrain using immunohistochemistry. We could demonstrate that Slc35f1 is highly expressed in the adult mouse brain in a variety of different brain structures, including the cortex, hippocampus, amygdala, thalamus, basal ganglia, and hypothalamus. To examine the possible roles of Slc35f1 and its subcellular localization, we used an in vitro glioblastoma cell line expressing Slc35f1. Co-labeling experiments were performed to reveal the subcellular localization of Slc35f1. Our results indicate that Slc35f1 neither co-localizes with markers for the Golgi apparatus nor with markers for the endoplasmic reticulum. Time-lapse microscopy of living cells revealed that Slc35f1-positive structures are highly dynamic and resemble vesicles. Using super-resolution microscopy, these Slc35f1-positive spots clearly co-localize with the recycling endosome marker Rab11.

Long-term Association of Periodontitis With Decreased Kidney Function.

RATIONALE & OBJECTIVE: Previous studies have yielded inconclusive findings regarding the relationship between periodontitis and kidney function. We sought to investigate whether periodontitis is associated with subsequent decreases in kidney function (reductions in estimated glomerular filtration rate [eGFR] and increased urinary albumin-creatinine ratio [UACR]) in the general population. STUDY DESIGN: Population-based cohort study. SETTING & PARTICIPANTS: We used baseline and 11-year follow-up data from 2,297 and 1,512 adult participants, respectively, in the Study of Health in Pomerania (SHIP). Age range was limited to 20 to 59 years to avoid the potential influence of tooth loss. EXPOSURES: Periodontal status defined by periodontal pocket probing depth (PPD) and clinical attachment level. Mean levels and the percentage of sites ≥ 3mm was determined for either all sites (PPD) or interproximal sites (clinical attachment level). All PPDs≥4mm were summed to calculate the total PPD. OUTCOMES: GFR estimated from serum creatinine and serum cystatin C (eGFRcr-cys). Moderately increased albuminuria defined as UACR>30mg/g. ANALYTICAL APPROACH: Adjusted linear and logistic mixed regression models. RESULTS: At baseline and follow-up, average eGFRcr-cys was 118.3 and 105.0mL/min/1.73m2, respectively. Using mixed models, no consistently significant associations between periodontitis variables and eGFRcr-cys were detected. Long-term changes in UACR were inconsistently associated with periodontitis measures. After imputation of missing data, associations were either attenuated or no longer detectable. LIMITATIONS: Because periodontal assessments were performed using a partial recording protocol, periodontal disease severity estimates might have been underestimated, resulting in attenuated effect estimates. CONCLUSIONS: We found no consistent evidence for an association between periodontitis and decreased kidney function. In contrast to previous studies, these results do not support the hypothesis that periodontitis is an important risk factor for chronic kidney disease.

Upregulation of Tumor Susceptibility Gene 101 (TSG101) by mechanical stress in podocytes.

Elevated mechanical stress in glomerular hypertension is thought to damage podocytes, the loss of which leads to development of glomerulosclerosis. Applying cDNA array analysis to mechanically stressed podocytes, we have recently identified TSG101 as a stretch-induced candidate gene among others. TSG101, which is part of the ESCRT-I complex, is involved in multivesicular body (MVB) formation. Here we demonstrate that TSG101 mRNA is strongly upregulated in conditionally immortalized mouse podocytes by cyclic mechanical stress. Differentiation of podocytes does not affect TSG101 mRNA levels. TSG101 immunofluorescence is distributed in a vesicular pattern in podocytes, the staining intensity being enhanced by mechanical stress. In DOCA/salt treated rats, a model of glomerular hypertension, glomerular TSG101 mRNA levels are elevated, and an increased number of MVBs is observed by electron microscopy in podocyte processes. Our data demonstrate that mechanical stress upregulates TSG101 in podocytes, suggesting that glomerular hypertension enhances sorting of cell surface proteins and their ligands into the degradative pathway in podocytes.

The Role of Palladin in Podocytes.

Background Podocyte loss and effacement of interdigitating podocyte foot processes are the major cause of a leaky filtration barrier and ESRD. Because the complex three-dimensional morphology of podocytes depends on the actin cytoskeleton, we studied the role in podocytes of the actin bundling protein palladin, which is highly expressed therein.Methods We knocked down palladin in cultured podocytes by siRNA transfection or in zebrafish embryos by morpholino injection and studied the effects by immunofluorescence and live imaging. We also investigated kidneys of mice with podocyte-specific knockout of palladin (PodoPalld-/- mice) by immunofluorescence and ultrastructural analysis and kidney biopsy specimens from patients by immunostaining for palladin.Results Compared with control-treated podocytes, palladin-knockdown podocytes had reduced actin filament staining, smaller focal adhesions, and downregulation of the podocyte-specific proteins synaptopodin and α-actinin-4. Furthermore, palladin-knockdown podocytes were more susceptible to disruption of the actin cytoskeleton with cytochalasin D, latrunculin A, or jasplakinolide and showed altered migration dynamics. In zebrafish embryos, palladin knockdown compromised the morphology and dynamics of epithelial cells at an early developmental stage. Compared with PodoPalld+/+ controls, PodoPalld-/- mice developed glomeruli with a disturbed morphology, an enlarged subpodocyte space, mild effacement, and significantly reduced expression of nephrin and vinculin. Furthermore, nephrotoxic serum injection led to significantly higher levels of proteinuria in PodoPalld-/- mice than in controls. Kidney biopsy specimens from patients with diabetic nephropathy and FSGS showed downregulation of palladin in podocytes as well.Conclusions Palladin has an important role in podocyte function in vitro and in vivo.

Serum chemerin levels are inversely associated with renal function in a general population.

OBJECTIVE: Chemerin has been found to be highly expressed in the kidneys of rodents and has been suggested to affect metabolic syndrome (MetS)-related phenotypes which are in turn related to kidney damage. Only few clinical studies have addressed the relation between circulating chemerin and renal function in humans, and no population-based analyses have yet been performed. The potential influence of MetS-related phenotypes on the assumed association has been largely neglected. We aimed to investigate the association of serum chemerin with renal function in a general population with special regard to possible interactions between chemerin and metabolic phenotypes. DESIGN, PATIENTS AND MEASUREMENTS: Linear and logistic regression models were applied to analyse data from 4082 subjects of the German Study of Health in Pomerania. Main outcomes included estimated glomerular filtration rate (eGFR), serum creatinine and cystatin C and chronic kidney disease. RESULTS: Inverse associations of chemerin with eGFR were observed. The components of the MetS emerged as modulating factors in this relation and enhanced the association. Logistic regression models confirmed the relation between chemerin and eGFR and revealed that each increase in chemerin per 25 ng/mL was associated with an about threefold higher odds of chronic kidney disease [odds ratio 2.72 (95% confidence interval 2.26-3.29)]. CONCLUSIONS: Our results demonstrate a strong inverse association between serum chemerin levels and renal function. This association might be explained by MetS-related phenotypes, which lead to renal damage and are associated with increased chemerin levels and/or an impaired renal elimination of chemerin by diseased kidneys.

Mortality is associated with inflammation, anemia, specific diseases and treatments, and molecular markers.

Lifespan is a complex trait, and longitudinal data for humans are naturally scarce. We report the results of Cox regression and Pearson correlation analyses using data of the Study of Health in Pomerania (SHIP), with mortality data of 1518 participants (113 of which died), over a time span of more than 10 years. We found that in the Cox regression model based on the Bayesian information criterion, apart from chronological age of the participant, six baseline variables were considerably associated with higher mortality rates: smoking, mean attachment loss (i.e. loss of tooth supporting tissue), fibrinogen concentration, albumin/creatinine ratio, treated gastritis, and medication during the last 7 days. Except for smoking, the causative contribution of these variables to mortality was deemed inconclusive. In turn, four variables were found to be associated with decreased mortality rates: treatment of benign prostatic hypertrophy, treatment of dyslipidemia, IGF-1 and being female. Here, being female was an undisputed causative variable, the causal role of IFG-1 was deemed inconclusive, and the treatment effects were deemed protective to the degree that treated subjects feature better survival than respective controls. Using Cox modeling based on the Akaike information criterion, diabetes, mean corpuscular hemoglobin concentration, red blood cell count and serum calcium were also associated with mortality. The latter two, together with albumin and fibrinogen, aligned with an"integrated albunemia" model of aging proposed recently.

FocusHeuristics - expression-data-driven network optimization and disease gene prediction.

To identify genes contributing to disease phenotypes remains a challenge for bioinformatics. Static knowledge on biological networks is often combined with the dynamics observed in gene expression levels over disease development, to find markers for diagnostics and therapy, and also putative disease-modulatory drug targets and drugs. The basis of current methods ranges from a focus on expression-levels (Limma) to concentrating on network characteristics (PageRank, HITS/Authority Score), and both (DeMAND, Local Radiality). We present an integrative approach (the FocusHeuristics) that is thoroughly evaluated based on public expression data and molecular disease characteristics provided by DisGeNet. The FocusHeuristics combines three scores, i.e. the log fold change and another two, based on the sum and difference of log fold changes of genes/proteins linked in a network. A gene is kept when one of the scores to which it contributes is above a threshold. Our FocusHeuristics is both, a predictor for gene-disease-association and a bioinformatics method to reduce biological networks to their disease-relevant parts, by highlighting the dynamics observed in expression data. The FocusHeuristics is slightly, but significantly better than other methods by its more successful identification of disease-associated genes measured by AUC, and it delivers mechanistic explanations for its choice of genes.

Serum protease activity in chronic kidney disease patients: The GANI_MED renal cohort.

Serum or plasma proteases have been associated with various diseases including cancer, inflammation, or reno-cardiovascular diseases. We aimed to investigate whether the enzymatic activities of serum proteases are associated with the estimated glomerular filtration rate (eGFR) in patients with different stages of chronic kidney disease (CKD). Our study population comprised 268 participants of the "Greifswald Approach to Individualized Medicine" (GANI_MED) cohort. Enzymatic activity of aminopeptidase A, aminopeptidase B, alanyl (membrane) aminopeptidase, insulin-regulated aminopeptidase, puromycin-sensitive aminopeptidase, leucine aminopeptidase 3, prolyl-endopeptidase (PEP), dipeptidyl peptidase 4 (DPP4), angiotensin I-converting enzyme, and angiotensin I-converting enzyme 2 (ACE2) proteases was measured in serum. Linear regression of the respective protease was performed on kidney function adjusted for age and sex. Kidney function was modeled either by the continuous Modification of Diet in Renal Disease (MDRD)-based eGFR or dichotomized by eGFR < 15 mL/min/1.73 m2 or <45 mL/min/1.73 m2, respectively. Results with a false discovery rate below 0.05 were deemed statistically significant. Among the 10 proteases investigated, only the activities of ACE2 and DPP4 were correlated with eGFR. Patients with lowest eGFR exhibited highest DPP4 and ACE2 activities. DPP4 and PEP were correlated with age, but all other serum protease activities showed no associations with age or sex. Our data indicate that ACE2 and DPP4 enzymatic activity are associated with the eGFR in patients with CKD. This finding distinguishes ACE2 and DPP4 from other serum peptidases analyzed and clearly indicates that further analyses are warranted to identify the precise role of these serum ectopeptidases in the pathogenesis of CKD and to fully elucidate underlying molecular mechanisms. Impact statement • Renal and cardiac diseases are very common and often occur concomitantly, resulting in increased morbidity and mortality. Understanding of molecular mechanisms linking both diseases is limited, available fragmentary data point to a role of the renin-angiotensin system (RAS) and, in particular, Ras-related peptidases. • Here, a comprehensive analysis of serum peptidase activities in patients with different stages of chronic kidney disease (CKD) is presented, with special emphasis given to RAS peptidases • The serum activities of the peptidases angiotensin I-converting enzyme 2 and dipeptidyl peptidase 4 were identified as closely associated with kidney function, specifically with the estimated glomerular filtration rate. The findings are discussed in the context of available data suggesting protective roles for both enzymes in reno-cardiac diseases. • The data add to our understanding of pathomechanisms underlying development and progression of CKD and indicate that both enzymes might represent potential pharmacological targets for the preservation of renal function.

Aldosterone and glomerular filtration--observations in the general population.

BACKGROUND: Increasing evidence suggests that aldosterone promotes renal damage. Since data on the association between aldosterone and renal function in the general population are sparse, we chose to address this issue. We investigated the associations between the plasma aldosterone concentration (PAC) or the aldosterone-to-renin ratio (ARR) and the estimated glomerular filtration rate (eGFR) in a sample of adult men and women from Northeast Germany. METHODS: A study population of 1921 adult men and women who participated in the first follow-up of the Study of Health in Pomerania was selected. None of the subjects used drugs that alter PAC or ARR. The eGFR was calculated according to the four-variable Modification of Diet in Renal Disease formula. Chronic kidney disease (CKD) was defined as an eGFR < 60 ml/min/1.73 m2. RESULTS: Linear regression models, adjusted for sex, age, waist circumference, diabetes mellitus, smoking status, systolic and diastolic blood pressures, serum triglyceride concentrations and time of blood sampling revealed inverse associations of PAC or ARR with eGFR (ß-coefficient for log-transformed PAC -3.12, p < 0.001; ß-coefficient for log-transformed ARR -3.36, p < 0.001). Logistic regression models revealed increased odds for CKD with increasing PAC (odds ratio for a one standard deviation increase in PAC: 1.35, 95% confidence interval: 1.06-1.71). There was no statistically significant association between ARR and CKD. CONCLUSION: Our study demonstrates that PAC and ARR are inversely associated with the glomerular filtration rate in the general population.

OPN deficiency results in severe glomerulosclerosis in uninephrectomized mice.

Osteopontin (OPN) expression has been reported to be elevated in experimental models of renal injury such as arterial hypertension or diabetic nephropathy finally leading to focal segmental glomerulosclerosis (FSGS). FSGS is characterized by glomerular matrix deposition and loss or damage of podocytes that represent the main constituents of the glomerular filtration barrier. To evaluate the role of OPN in the kidney we investigated WT and OPN knockout mice (OPN-/-) without treatment, after uninephrectomy (UNX), as well as after UNX and desoxycorticosterone acetate (DOCA)-salt treatment with respect to urine parameters, glomerular morphology, and expression of podocyte markers. OPN-/- mice showed normal urine parameters while a thickening of the glomerular basement membrane was evident. Intriguingly, following UNX, OPN-/- mice exhibited prominent FSGS, proteinuria, and glomerular matrix deposition. Electron microscopy revealed bulgings of the glomerular basement membrane and occasionally an effacement of podocytes. After UNX and DOCA-salt treatment, severe glomerular lesions as well as proteinuria and albuminuria were seen in WT and OPN-/- mice. Moreover, we found a reduction of specific markers such as Wilm's tumor-1, podocin, and synaptopodin in both experimental groups indicating a loss of podocytes. Podocyte damage was accompanied by increased number of Ki-67-positive cells in the parietal epithelium of Bowman's capsule. We conclude that OPN plays a crucial role in adaptation of podocytes following renal ablation and is renoprotective when glomerular mechanical load is increased.

Integration of genome-wide association studies with biological knowledge identifies six novel genes related to kidney function.

In conducting genome-wide association studies (GWAS), analytical approaches leveraging biological information may further understanding of the pathophysiology of clinical traits. To discover novel associations with estimated glomerular filtration rate (eGFR), a measure of kidney function, we developed a strategy for integrating prior biological knowledge into the existing GWAS data for eGFR from the CKDGen Consortium. Our strategy focuses on single nucleotide polymorphism (SNPs) in genes that are connected by functional evidence, determined by literature mining and gene ontology (GO) hierarchies, to genes near previously validated eGFR associations. It then requires association thresholds consistent with multiple testing, and finally evaluates novel candidates by independent replication. Among the samples of European ancestry, we identified a genome-wide significant SNP in FBXL20 (P = 5.6 × 10(-9)) in meta-analysis of all available data, and additional SNPs at the INHBC, LRP2, PLEKHA1, SLC3A2 and SLC7A6 genes meeting multiple-testing corrected significance for replication and overall P-values of 4.5 × 10(-4)-2.2 × 10(-7). Neither the novel PLEKHA1 nor FBXL20 associations, both further supported by association with eGFR among African Americans and with transcript abundance, would have been implicated by eGFR candidate gene approaches. LRP2, encoding the megalin receptor, was identified through connection with the previously known eGFR gene DAB2 and extends understanding of the megalin system in kidney function. These findings highlight integration of existing genome-wide association data with independent biological knowledge to uncover novel candidate eGFR associations, including candidates lacking known connections to kidney-specific pathways. The strategy may also be applicable to other clinical phenotypes, although more testing will be needed to assess its potential for discovery in general.

Morphology and migration of podocytes are affected by CD151 levels.

CD151, a member of the tetraspanin family of membrane proteins, is crucially involved in the formation of the glomerular filtration barrier in humans and mice. However, the role of CD151 in podocytes has not been investigated so far. In the present study, we utilized a conditionally immortalized mouse podocyte cell line to characterize CD151 in podocytes and to examine the consequences of manipulating CD151 expression levels. Mouse podocytes endogenously express CD151 as determined by RT-PCR and Western blotting. GFP-CD151 fusion protein localized to the cell membrane, to cell protrusions and cell-cell contacts, colocalizing with actin, ß(1)-integrin, zonula occludens-1, and CD9. The expression of GFP-CD151 in cultured podocytes resulted in a marked increase in the presence of thin arborized protrusions (TAPs). TAPs are distinct from filopodia by increased length, protein composition, branched morphology, and slower dynamics. Furthermore, the migration rate of pEGFP-CD151-transfected podocytes was reduced in a wound assay. Fluorescence recovery after photo bleaching measurements revealed a half-time of 3 s for GFP-CD151 consistent with a high mobility of CD151 in the membrane and cytosol. CD151 knockdown in podocytes reduced ß(1)-integrin expression and podocyte cell area, indicating diminished adherence and/or spreading. Our results indicate that CD151 importantly modulates podocyte function.

Age- and sex-specific reference limits for creatinine, cystatin C and the estimated glomerular filtration rate.

BACKGROUND: Early detection of patients with chronic kidney disease is of great importance. This study developed reference limits for serum creatinine and serum cystatin C concentrations and for the estimated glomerular filtration rate (eGFR) in healthy subjects from the general population aged 25-65 years. METHODS: This study defined a reference population including 985 subjects from the first follow-up of the Study of Health in Pomerania. Serum creatinine was measured with a modified kinetic Jaffé method. Serum cystatin C was measured with a nephelometric assay. The eGFR was calculated from serum creatinine according to the Cockcroft-Gault (eGFR(CG)) and the Modification of Diet in Renal Disease (eGFR(MDRD)) equation, respectively, as well as from serum cystatin C according to the formula by Larsson (eGFR(Larsson)). Non-parametric quantile regression was used to estimate the reference limits. For serum creatinine and serum cystatin C the 95th percentile and for eGFR(CG), eGFR(MDRD) and eGFR(Larsson) the 5th percentile were selected as reference limits. All data was weighted to reflect the age- and sex-structure of the German population in 2008. RESULTS: The reference limits for serum creatinine (men: 1.11-1.23 mg/dL; women: 0.93-1.00 mg/dL) and serum cystatin C levels (men: 0.92-1.04 mg/L; women: 0.84-1.02 mg/L) increased with advancing age. The reference limits for eGFR decreased with increasing age (eGFR(CG) men: 106.0-64.7 mL/min, women 84.4-57.9 mL/min; eGFR(MDRD) men: 82.5-62.2 mL/min/1.73 m², women 75.0-58.2 mL/min/1.73 m²; eGFR(Larsson) men: 85.5-72.9 mL/min, women 94.5-75.7 mL/min). CONCLUSIONS: This study presents age- and sex-specific reference limits for five measures of renal function based on quantile regression models.

Epidermal growth factor receptor promotes glomerular injury and renal failure in rapidly progressive crescentic glomerulonephritis.

Rapidly progressive glomerulonephritis (RPGN) is a life-threatening clinical syndrome and a morphological manifestation of severe glomerular injury that is marked by a proliferative histological pattern ('crescents') with accumulation of T cells and macrophages and proliferation of intrinsic glomerular cells. We show de novo induction of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in intrinsic glomerular epithelial cells (podocytes) from both mice and humans with RPGN. HB-EGF induction increases phosphorylation of the epidermal growth factor receptor (EGFR, also known as ErbB1) in mice with RPGN. In HB-EGF-deficient mice, EGFR activation in glomeruli is absent and the course of RPGN is improved. Autocrine HB-EGF induces a phenotypic switch in podocytes in vitro. Conditional deletion of the Egfr gene from podocytes of mice alleviates the severity of RPGN. Likewise, pharmacological blockade of EGFR also improves the course of RPGN, even when started 4 d after the induction of experimental RPGN. This suggests that targeting the HB-EGF-EGFR pathway could also be beneficial in treatment of human RPGN.

Parietal epithelial cells participate in the formation of sclerotic lesions in focal segmental glomerulosclerosis.

The pathogenesis of the development of sclerotic lesions in focal segmental glomerulosclerosis (FSGS) remains unknown. Here, we selectively tagged podocytes or parietal epithelial cells (PECs) to determine whether PECs contribute to sclerosis. In three distinct models of FSGS (5/6-nephrectomy + DOCA-salt; the murine transgenic chronic Thy1.1 model; or the MWF rat) and in human biopsies, the primary injury to induce FSGS associated with focal activation of PECs and the formation of cellular adhesions to the capillary tuft. From this entry site, activated PECs invaded the affected segment of the glomerular tuft and deposited extracellular matrix. Within the affected segment, podocytes were lost and mesangial sclerosis developed within the endocapillary compartment. In conclusion, these results demonstrate that PECs contribute to the development and progression of the sclerotic lesions that define FSGS, but this pathogenesis may be relevant to all etiologies of glomerulosclerosis.