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A profile-based search of the SWISS-PROT database reveals that most protein tyrosine phosphatases (PTPs) contain at least one caveolin-1-binding motif. To ascertain if the presence of caveolin-binding motif(s) in PTPs corresponds to their actual localization in caveolin-1-enriched membrane fractions, we performed subcellular fractionating experiments. We found that all tested PTPs (PTP1B, PTP1C, SHPTP2, PTEN, and LAR) are actually localized in caveolin-enriched membrane fractions, despite their distribution in other subcellular sites, too. More than 1/2 of LAR and about 1/4 of SHPTP2 and PTP-1C are localized in caveolin-enriched membrane fractions whereas, in these fractions, PTP-1B and PTEN are poorly concentrated. Co-immunoprecipitation experiments with antibodies specific for each tested PTP demonstrated that all five phosphatases form molecular complexes with caveolin-1 in vivo. Collectively, our findings propose that particular PTPs could perform some of their cellular actions or are regulated by recruitment into caveolin-enriched membrane fractions. [Copyright &y& Elsevier]

Background: Chronic kidney disease affects 10% of the world population, and it is associated with progression to end-stage kidney disease and increased morbidity and mortality. The advent of multi-omics technologies has expanded our knowledge on the complexity of kidney diseases, revealing their frequent genetic etiology, particularly in children and young subjects. Genetic heterogeneity and drug screening require patient-derived disease models to establish a correct diagnosis and evaluate new potential treatments and outcomes., Summary: Patient-derived renal progenitors can be isolated from urine to set up proper disease modeling. This strategy allows to make diagnosis of genetic kidney disease in patients carrying unknown significance variants or uncover variants missed from peripheral blood analysis. Furthermore, urinary-derived tubuloids obtained from renal progenitors of patients appear to be potentially valuable for modeling kidney diseases to test ex vivo treatment efficacy or to develop new therapeutic approaches. Finally, renal progenitors derived from urine can provide insights into acute kidney injury and predict kidney function recovery and outcome., Key Messages: Renal progenitors derived from urine are a promising new noninvasive and easy-to-handle tool, which improves the rate of diagnosis and the therapeutic choice, paving the way toward a personalized healthcare., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

Polyploidization of tubular cells (TC) is triggered by acute kidney injury (AKI) to allow survival in the early phase after AKI, but in the long run promotes fibrosis and AKI-chronic kidney disease (CKD) transition. The molecular mechanism governing the link between polyploid TC and kidney fibrosis remains to be clarified. In this study, we demonstrate that immediately after AKI, expression of cell cycle markers mostly identifies a population of DNA-damaged polyploid TC. Using transgenic mouse models and single-cell RNA sequencing we show that, unlike diploid TC, polyploid TC accumulate DNA damage and survive, eventually resting in the G1 phase of the cell cycle. In vivo and in vitro single-cell RNA sequencing along with sorting of polyploid TC shows that these cells acquire a profibrotic phenotype culminating in transforming growth factor (TGF)-β1 expression and that TGF-β1 directly promotes polyploidization. This demonstrates that TC polyploidization is a self-sustained mechanism. Interactome analysis by single-cell RNA sequencing revealed that TGF-β1 signaling fosters a reciprocal activation loop among polyploid TC, macrophages, and fibroblasts to sustain kidney fibrosis and promote CKD progression. Collectively, this study contributes to the ongoing revision of the paradigm of kidney tubule response to AKI, supporting the existence of a tubulointerstitial cross talk mediated by TGF-β1 signaling produced by polyploid TC following DNA damage. NEW & NOTEWORTHY Polyploidization in tubular epithelial cells has been neglected until recently. Here, we showed that polyploidization is a self-sustained mechanism that plays an important role during chronic kidney disease development, proving the existence of a cross talk between infiltrating cells and polyploid tubular cells. This study contributes to the ongoing revision of kidney adaptation to injury, posing polyploid tubular cells at the center of the process.

Kidney diseases are a global health concern. Modeling of kidney disease for translational research is often challenging because of species specificities or the postmitotic status of kidney epithelial cells that make primary cultures, for example podocytes. Here, we report a protocol for preparing primary cultures of podocytes based on the isolation and in vitro propagation of immature kidney progenitor cells subsequently differentiated into mature podocytes. This protocol can be useful for studying physiology and pathophysiology of human kidney progenitors and to obtain differentiated podocytes for modeling podocytopathies and other kidney disorders involving podocytes., Competing Interests: Competing interestsThe authors have no competing financial interests., (©Copyright : © 2023 The Authors; This is an open access article under the CC BY license.)

Significance Statement: To optimize the diagnosis of genetic kidney disorders in a cost-effective manner, we developed a workflow based on referral criteria for in-person evaluation at a tertiary center, whole-exome sequencing, reverse phenotyping, and multidisciplinary board analysis. This workflow reached a diagnostic rate of 67%, with 48% confirming and 19% modifying the suspected clinical diagnosis. We obtained a genetic diagnosis in 64% of children and 70% of adults. A modeled cost analysis demonstrated that early genetic testing saves 20% of costs per patient. Real cost analysis on a representative sample of 66 patients demonstrated an actual cost reduction of 41%. This workflow demonstrates feasibility, performance, and economic effect for the diagnosis of genetic kidney diseases in a real-world setting., Background: Whole-exome sequencing (WES) increases the diagnostic rate of genetic kidney disorders, but accessibility, interpretation of results, and costs limit use in daily practice., Methods: Univariable analysis of a historical cohort of 392 patients who underwent WES for kidney diseases showed that resistance to treatments, familial history of kidney disease, extrarenal involvement, congenital abnormalities of the kidney and urinary tract and CKD stage ≥G2, two or more cysts per kidney on ultrasound, persistent hyperechoic kidneys or nephrocalcinosis on ultrasound, and persistent metabolic abnormalities were most predictive for genetic diagnosis. We prospectively applied these criteria to select patients in a network of nephrology centers, followed by centralized genetic diagnosis by WES, reverse phenotyping, and multidisciplinary board discussion., Results: We applied this multistep workflow to 476 patients with eight clinical categories (podocytopathies, collagenopathies, CKD of unknown origin, tubulopathies, ciliopathies, congenital anomalies of the kidney and urinary tract, syndromic CKD, metabolic kidney disorders), obtaining genetic diagnosis for 319 of 476 patients (67.0%) (95% in 21 patients with disease onset during the fetal period or at birth, 64% in 298 pediatric patients, and 70% in 156 adult patients). The suspected clinical diagnosis was confirmed in 48% of the 476 patients and modified in 19%. A modeled cost analysis showed that application of this workflow saved 20% of costs per patient when performed at the beginning of the diagnostic process. Real cost analysis of 66 patients randomly selected from all categories showed actual cost reduction of 41%., Conclusions: A diagnostic workflow for genetic kidney diseases that includes WES is cost-saving, especially if implemented early, and is feasible in a real-world setting., (Copyright © 2023 by the American Society of Nephrology.)

Acute kidney injury (AKI) is frequent, often fatal and, for lack of specific therapies, can leave survivors with chronic kidney disease (CKD). We characterize the distribution of tubular cells (TC) undergoing polyploidy along AKI by DNA content analysis and single cell RNA-sequencing. Furthermore, we study the functional roles of polyploidization using transgenic models and drug interventions. We identify YAP1-driven TC polyploidization outside the site of injury as a rapid way to sustain residual kidney function early during AKI. This survival mechanism comes at the cost of senescence of polyploid TC promoting interstitial fibrosis and CKD in AKI survivors. However, targeting TC polyploidization after the early AKI phase can prevent AKI-CKD transition without influencing AKI lethality. Senolytic treatment prevents CKD by blocking repeated TC polyploidization cycles. These results revise the current pathophysiological concept of how the kidney responds to acute injury and identify a novel druggable target to improve prognosis in AKI survivors., (© 2022. The Author(s).)

Crescentic glomerulonephritis is characterized by vascular necrosis and parietal epithelial cell hyperplasia in the space surrounding the glomerulus, resulting in the formation of crescents. Little is known about the molecular mechanisms driving this process. Inducing crescentic glomerulonephritis in two Pax2Cre reporter mouse models revealed that crescents derive from clonal expansion of single immature parietal epithelial cells. Preemptive and delayed histone deacetylase inhibition with panobinostat, a drug used to treat hematopoietic stem cell disorders, attenuated crescentic glomerulonephritis with recovery of kidney function in the two mouse models. Three-dimensional confocal microscopy and stimulated emission depletion superresolution imaging of mouse glomeruli showed that, in addition to exerting an anti-inflammatory and immunosuppressive effect, panobinostat induced differentiation of an immature hyperplastic parietal epithelial cell subset into podocytes, thereby restoring the glomerular filtration barrier. Single-cell RNA sequencing of human renal progenitor cells in vitro identified an immature stratifin-positive cell subset and revealed that expansion of this stratifin-expressing progenitor cell subset was associated with a poor outcome in human crescentic glomerulonephritis. Treatment of human parietal epithelial cells in vitro with panobinostat attenuated stratifin expression in renal progenitor cells, reduced their proliferation, and promoted their differentiation into podocytes. These results offer mechanistic insights into the formation of glomerular crescents and demonstrate that selective targeting of renal progenitor cells can attenuate crescent formation and the deterioration of kidney function in crescentic glomerulonephritis in mice.

Bartter (BS) and Gitelman (GS) syndrome are autosomal recessive inherited tubulopathies, whose clinical diagnosis can be challenging, due to rarity and phenotypic overlap. Genotype-phenotype correlations have important implications in defining kidney and global outcomes. The aim of our study was to assess the diagnostic rate of whole-exome sequencing (WES) coupled with a bioinformatic analysis of copy number variations in a population of 63 patients with BS and GS from a single institution, and to explore genotype-phenotype correlations. We obtained a diagnostic yield of 86% (54/63 patients), allowing disease reclassification in about 14% of patients. Although some clinical and laboratory features were more commonly reported in patients with BS or GS, a significant overlap does exist, and age at onset, preterm birth, gestational age and nephro-calcinosis are frequently misleading. Finally, chronic kidney disease (CKD) occurs in about 30% of patients with BS or GS, suggesting that the long-term prognosis can be unfavorable. In our cohort the features associated with CKD were lower gestational age at birth and a molecular diagnosis of BS, especially BS type 1. The results of our study demonstrate that WES is useful in dealing with the phenotypic heterogeneity of these disorders, improving differential diagnosis and genotype-phenotype correlation.

Steroid-resistant nephrotic syndrome (SRNS) is a clinical picture defined by the lack of response to standard steroid treatment, frequently progressing toward end-stage kidney disease. The genetic basis of SRNS has been thoroughly explored since the end of the 1990s and especially with the advent of next-generation sequencing. Genetic forms represent about 30% of cases of SRNS. However, recent evidence supports the hypothesis that "phenocopies" could account for a non-negligible fraction of SRNS patients who are currently classified as non-genetic, paving the way for a more comprehensive understanding of the genetic background of the disease. The identification of phenocopies is mandatory in order to provide patients with appropriate clinical management and to inform therapy. Extended genetic testing including phenocopy genes, coupled with reverse phenotyping, is recommended for all young patients with SRNS to avoid unnecessary and potentially harmful diagnostic procedures and treatment, and for the reclassification of the disease. The aim of this work is to review the main steps of the evolution of genetic testing in SRNS, demonstrating how a paradigm shifting from "forward" to "reverse" genetics could significantly improve the identification of the molecular mechanisms of the disease, as well as the overall clinical management of affected patients.

Introduction : The number of patients with end-stage kidney disease is increasing worldwide, creating an unprecedented organ shortage. The kidney is a highly complex structure performing many crucial functions. Dialysis replaces filtration but not all other kidney functions and transplant is limited by kidney availability. Numerous innovative ways are being explored to obtain new kidneys for disease modeling and potentially replace lost kidney functions. Areas covered : In this review, we will go through the different approaches that have been developed over the years to build kidneys. We will first present the current advances in xenotransplantation and generation of interspecies chimeras. Next, we will examine the attempts to create bioengineered kidneys with hemodialysis-derived implantable devices and decellularized organs. Finally, we will examine how organoids and microfluidic devices could answer important pathophysiological questions and model the path toward creating in vitro functional organs, for example through 3D bioprinting. Expert opinion : While all the aforementioned approaches to create new kidneys are promising, their translation into clinical practice seems a long way off, except xenotransplantation. Nonetheless, these novel technologies already consent disease modeling and drug testing at 3D level. We will review the stages of progress toward patient therapy and advantages/drawbacks of the various strategies.

Acute tissue injury causes DNA damage and repair processes involving increased cell mitosis and polyploidization, leading to cell function alterations that may potentially drive cancer development. Here, we show that acute kidney injury (AKI) increased the risk for papillary renal cell carcinoma (pRCC) development and tumor relapse in humans as confirmed by data collected from several single-center and multicentric studies. Lineage tracing of tubular epithelial cells (TECs) after AKI induction and long-term follow-up in mice showed time-dependent onset of clonal papillary tumors in an adenoma-carcinoma sequence. Among AKI-related pathways, NOTCH1 overexpression in human pRCC associated with worse outcome and was specific for type 2 pRCC. Mice overexpressing NOTCH1 in TECs developed papillary adenomas and type 2 pRCCs, and AKI accelerated this process. Lineage tracing in mice identified single renal progenitors as the cell of origin of papillary tumors. Single-cell RNA sequencing showed that human renal progenitor transcriptome showed similarities to PT1, the putative cell of origin of human pRCC. Furthermore, NOTCH1 overexpression in cultured human renal progenitor cells induced tumor-like 3D growth. Thus, AKI can drive tumorigenesis from local tissue progenitor cells. In particular, we find that AKI promotes the development of pRCC from single progenitors through a classical adenoma-carcinoma sequence., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Background and Objectives: Nephrotic syndrome is a typical presentation of genetic podocytopathies but occasionally other genetic nephropathies can present as clinically indistinguishable phenocopies. We hypothesized that extended genetic testing followed by reverse phenotyping would increase the diagnostic rate for these patients., Design, Setting, Participants, & Measurements: All patients diagnosed with nephrotic syndrome and referred to our center between 2000 and 2018 were assessed in this retrospective study. When indicated, whole-exome sequencing and in silico filtering of 298 genes related to CKD were combined with subsequent reverse phenotyping in patients and families. Pathogenic variants were defined according to current guidelines of the American College of Medical Genetics., Results: A total of 111 patients (64 steroid-resistant and 47 steroid-sensitive) were included in the study. Not a single pathogenic variant was detected in the steroid-sensitive group. Overall, 30% (19 out of 64) of steroid-resistant patients had pathogenic variants in podocytopathy genes, whereas a substantial number of variants were identified in other genes, not commonly associated with isolated nephrotic syndrome. Reverse phenotyping, on the basis of a personalized diagnostic workflow, permitted to identify previously unrecognized clinical signs of an unexpected underlying genetic nephropathy in a further 28% (18 out of 64) of patients. These patients showed similar multidrug resistance, but different long-term outcome, when compared with genetic podocytopathies., Conclusions: Reverse phenotyping increased the diagnostic accuracy in patients referred with the diagnosis of steroid-resistant nephrotic syndrome., (Copyright © 2020 by the American Society of Nephrology.)

MicroRNAs (miRNAs/miRs) are a novel class of gene regulators that may be involved in tumor chemoresistance. Recently, specific miRNA expression profiles have been identified in adult glioblastoma (aGBM), but there are only limited data available on the role of miRNAs in pediatric GBM (pGBM). In the present study, the expression profile of miRNAs was examined in seven pGBMs and three human GBM cell lines (U87MG, A172 and T98G), compared with a non-tumoral pool of pediatric cerebral cortex samples by microarray analysis. A set of differentially expressed miRNAs was identified, including miR-490, miR-876-3p, miR-876-5p, miR-448 and miR-137 (downregulated), as well as miR-501-3p (upregulated). Through bioinformatics analysis, a series of target genes was predicted. In addition, similar gene expression patterns in pGBMs and cell lines was confirmed. Of note, drug resistant T98G cells had upregulated nuclear casein kinase and cyclin-dependent kinase substrate 1 ( NUCKS1 ) expression, a protein overexpressed in many tumors that serves an important role in cell proliferation and progression. On the basis of the present preliminary report, it could be intriguing to further investigate the relationship between each of the identified differentially expressed miRNAs and NUCKS1, in order to clarify their involvement in the multi-drug resistance mechanism of pGBMs.

Introduction: Chronic kidney disease is a major health-care problem worldwide and its cost is becoming no longer affordable. Indeed, restoring damaged renal structures or building a new kidney represents an ambitious and ideal alternative to renal replacement therapy. Streams of research have explored the possible application of pluripotent stem cells (SCs) (embryonic SCs and induced pluripotent SCs) in different strategies aimed at regenerate functioning nephrons and at understanding the mechanisms of kidney regeneration., Areas Covered: In this review, we will focus on the main potential applications of human pluripotent SCs to kidney regeneration, including those leading to rebuilding new kidneys or part of them (organoids, scaffolds, biological microdevices) as well as those aimed at understanding the pathophysiological mechanisms of renal disease and regenerative processes (modeling of kidney disease, genome editing). Moreover, we will discuss the role of endogenous renal progenitors cells in order to understand and promote kidney regeneration, as an attractive alternative to pluripotent SCs., Expert Opinion: Opportunities and pitfalls of all these strategies will be underlined, finally leading to the conclusion that a deeper knowledge of the biology of pluripotent SCs is mandatory, in order to allow us to hypothesize their clinical application.

Acute kidney injury (AKI) is considered largely reversible based on the capacity of surviving tubular cells to dedifferentiate and replace lost cells via cell division. Here we show by tracking individual tubular cells in conditional Pax8/Confetti mice that kidney function is  recovered after AKI despite substantial tubular cell loss. Cell cycle and ploidy analysis upon AKI in conditional Pax8/FUCCI2aR mice and human biopsies identify endocycle-mediated hypertrophy of tubular cells. By contrast, a small subset of Pax2+ tubular progenitors enriches via higher stress resistance and clonal expansion and regenerates necrotic tubule segments, a process that can be enhanced by suitable drugs. Thus,  renal functional recovery upon AKI involves remnant tubular cell hypertrophy via endocycle and limited progenitor-driven regeneration that can be pharmacologically enhanced.

Primary distal renal tubular acidosis is a rare genetic disease. Mutations in SLC4A1, ATP6V0A4, and ATP6V1B1 genes have been described as the cause of the disease, transmitted as either an autosomal dominant or recessive trait. Particular clinical features, such as sensorineural hearing loss, have been mainly described in association with mutations in one gene instead of the others. Nevertheless, the diagnosis of distal renal tubular acidosis is essentially based on clinical and laboratory findings, and the series of patients described so far are usually represented by small cohorts. Therefore, a strict genotype-phenotype correlation is still lacking, and questions about whether clinical and laboratory data should direct the genetic analysis remain open. Here, we applied next-generation sequencing in 89 patients with a clinical diagnosis of distal renal tubular acidosis, analyzing the prevalence of genetic defects in SLC4A1, ATP6V0A4, and ATP6V1B1 genes and the clinical phenotype. A genetic cause was determined in 71.9% of cases. In our group of sporadic cases, clinical features, including sensorineural hearing loss, are not specific indicators of the causal underlying gene. Mutations in the ATP6V0A4 gene are quite as frequent as mutations in ATP6V1B1 in patients with recessive disease. Chronic kidney disease was frequent in patients with a long history of the disease. Thus, our results suggest that when distal renal tubular acidosis is suspected, complete genetic testing could be considered, irrespective of the clinical phenotype of the patient., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Introduction: Chronic kidney disease (CKD) is recognized as a health care problem of increasing importance. Following the discovery of renal progenitors, the investigation of new therapeutic approaches to promote the kidney regenerative capacity has received increasing research attention., Areas Covered: The authors discuss the current knowledge of glomerular regeneration by renal progenitors and the modulation of their behavior through chemical and biological agents. The regenerative capacity of renal progenitors after injury must be regulated in order to prevent an inefficient or excessive response that could lead to a failed attempt to replace lost podocytes. In addition, they discuss the most relevant pathways involved in tubular repair and how these could be modulated in order to obtain renal regeneration rather than progression of a fibrotic maladaptive response., Expert Opinion: Modulation of the endogenous renal regenerative capacity is a new approach in the treatment of kidney diseases. Research efforts that concentrate on the potential regenerative capacity of the kidney can be advantageous when the experimental results are translated into clinical practice and may open the way to new therapeutic strategies for CKD.

Often the cause of refractory lupus nephritis (RLN) remains unclear. We performed next-generation sequencing for podocyte genes in an RLN patient and identified compound heterozygosity for APOL1 risk alleles G1 and G2 and a novel homozygous c.[1049C>T]+[1049C>T] NPHS1 gene variant of unknown significance. To test for causality renal progenitor cells isolated from urine of this patient were differentiated into podocytes in vitro. Podocytes revealed aberrant nephrin trafficking, cytoskeletal structure and lysosomal leakage, and increased detachment as compared with podocytes isolated from controls. Thus, lupus podocytopathy can be confirmed as a cause of RLN by functional genetics on patient-derived podocytes., (© The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Primitive nephrotic syndrome is one of the most common glomerular diseases in childhood and represents the clinical manifestation of various pathologic changes in the kidney. In children, nephrotic syndrome is classified based on the initial response to empiric corticosteroid treatment, which is considered as the best predictor of patients' final outcome. The advent of next-generation sequencing technology showed that genetic alterations in structural genes of the podocyte can be recognized in a significant proportion of not only familial or syndromic patients with steroid-resistant nephrotic syndrome (SRNS), but also of sporadic cases, raising the question of whether it is time to update current protocols of patient care. In this review, we discuss the implications derived from several studies describing a high prevalence in children with SRNS of pathogenic mutations in a group of genes and their unresponsiveness to immunosuppressive therapy. We propose a diagnostic and therapeutic algorithm to reduce the exposure to immunosuppressants in individuals with unresponsive forms of the disease, sparing patients the untoward side effects of prolonged ineffective treatments, and at the same time guaranteeing the optimal immunosuppressive or other new therapy in potentially responsive patients.

Podocyte loss is a general mechanism of glomerular dysfunction that initiates and drives the progression of chronic kidney disease, which affects 10% of the world population. Here, we evaluate whether the regenerative response to podocyte injury influences chronic kidney disease outcome. In models of focal segmental glomerulosclerosis performed in inducible transgenic mice where podocytes are tagged, remission or progression of disease was determined by the amount of regenerated podocytes. When the same model was established in inducible transgenic mice where renal progenitors are tagged, the disease remitted if renal progenitors successfully differentiated into podocytes, while it persisted if differentiation was ineffective, resulting in glomerulosclerosis. Treatment with BIO, a GSK3s inhibitor, significantly increased disease remission by enhancing renal progenitor sensitivity to the differentiation effect of endogenous retinoic acid. These results establish renal progenitors as critical determinants of glomerular disease outcome and a pharmacological enhancement of their differentiation as a possible therapeutic strategy., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

The critical role of genetic and epigenetic factors in the pathogenesis of kidney disorders is gradually becoming clear, and the need for disease models that recapitulate human kidney disorders in a personalized manner is paramount. In this study, we describe a method to select and amplify renal progenitor cultures from the urine of patients with kidney disorders. Urine-derived human renal progenitors exhibited phenotype and functional properties identical to those purified from kidney tissue, including the capacity to differentiate into tubular cells and podocytes, as demonstrated by confocal microscopy, Western blot analysis of podocyte-specific proteins, and scanning electron microscopy. Lineage tracing studies performed with conditional transgenic mice, in which podocytes are irreversibly tagged upon tamoxifen treatment (NPHS2.iCreER;mT/mG), that were subjected to doxorubicin nephropathy demonstrated that renal progenitors are the only urinary cell population that can be amplified in long-term culture. To validate the use of these cells for personalized modeling of kidney disorders, renal progenitors were obtained from (1) the urine of children with nephrotic syndrome and carrying potentially pathogenic mutations in genes encoding for podocyte proteins and (2) the urine of children without genetic alterations, as validated by next-generation sequencing. Renal progenitors obtained from patients carrying pathogenic mutations generated podocytes that exhibited an abnormal cytoskeleton structure and functional abnormalities compared with those obtained from patients with proteinuria but without genetic mutations. The results of this study demonstrate that urine-derived patient-specific renal progenitor cultures may be an innovative research tool for modeling of genetic kidney disorders., (Copyright © 2015 by the American Society of Nephrology.)

In children, sporadic nephrotic syndrome can be related to a genetic cause, but to what extent genetic alterations associate with resistance to immunosuppression is unknown. In this study, we designed a custom array for next-generation sequencing analysis of 19 target genes, reported as possible causes of nephrotic syndrome, in a cohort of 31 children affected by sporadic steroid-resistant nephrotic syndrome and 38 patients who exhibited a similar but steroid-sensitive clinical phenotype. Patients who exhibited extrarenal symptoms, had a familial history of the disease or consanguinity, or had a congenital onset were excluded. We identified a genetic cause in 32.3% of the children with steroid-resistant disease but zero of 38 children with steroid-sensitive disease. Genetic alterations also associated with lack of response to immunosuppressive agents in children with steroid-resistant disease (0% of patients with alterations versus 57.9% of patients without alterations responded to immunosuppressive agents), whereas clinical features, age at onset, and pathologic findings were similar in steroid-resistant patients with and without alterations. These results suggest that heterogeneous genetic alterations in children with sporadic forms of nephrotic syndrome associate with resistance to steroids as well as immunosuppressive treatments. In these patients, a comprehensive screening using such an array may, thus, be useful for genetic counseling and may help clinical decision making in a fast and cost-efficient manner., (Copyright © 2015 by the American Society of Nephrology.)

In CKD, the risk of kidney failure and death depends on the severity of proteinuria, which correlates with the extent of podocyte loss and glomerular scarring. We investigated whether proteinuria contributes directly to progressive glomerulosclerosis through the suppression of podocyte regeneration and found that individual components of proteinuria exert distinct effects on renal progenitor survival and differentiation toward a podocyte lineage. In particular, albumin prevented podocyte differentiation from human renal progenitors in vitro by sequestering retinoic acid, thus impairing retinoic acid response element (RARE)-mediated transcription of podocyte-specific genes. In mice with Adriamycin nephropathy, a model of human FSGS, blocking endogenous retinoic acid synthesis increased proteinuria and exacerbated glomerulosclerosis. This effect was related to a reduction in podocyte number, as validated through genetic podocyte labeling in NPHS2.Cre;mT/mG transgenic mice. In RARE-lacZ transgenic mice, albuminuria reduced retinoic acid bioavailability and impaired RARE activation in renal progenitors, inhibiting their differentiation into podocytes. Treatment with retinoic acid restored RARE activity and induced the expression of podocyte markers in renal progenitors, decreasing proteinuria and increasing podocyte number, as demonstrated in serial biopsy specimens. These results suggest that albumin loss through the damaged filtration barrier impairs podocyte regeneration by sequestering retinoic acid and promotes the generation of FSGS lesions. Our findings may explain why reducing proteinuria delays CKD progression and provide a biologic rationale for the clinical use of pharmacologic modulators to induce regression of glomerular diseases.

The contribution of microRNA (miRNA) to the pathogenesis of renal fibrosis is not well understood. Here, we investigated whether miRNA modulates the fibrotic process in Munich Wistar Fromter (MWF) rats, which develop spontaneous progressive nephropathy. We analyzed the expression profile of miRNA in microdissected glomeruli and found that miR-324-3p was the most upregulated. In situ hybridization localized miR-324-3p to glomerular podocytes, parietal cells of Bowman's capsule, and most abundantly, cortical tubules. A predicted target of miR-324-3p is prolyl endopeptidase (Prep), a serine peptidase involved in the metabolism of angiotensins and the synthesis of the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). In cultured tubular cells, transient transfection with a miR-324-3p mimic reduced Prep protein and activity, validating Prep as a target of this miRNA. In MWF rats, upregulation of miR-324-3p associated with markedly reduced expression of Prep in both glomeruli and tubules, low urine Ac-SDKP, and increased deposition of collagen. ACE inhibition downregulated glomerular and tubular miR-324-3p, promoted renal Prep expression, increased plasma and urine Ac-SDKP, and attenuated renal fibrosis. In summary, these results suggest that dysregulation of the miR-324-3p/Prep pathway contributes to the development of fibrosis in progressive nephropathy. The renoprotective effects of ACE inhibitors may result, in part, from modulation of this pathway, suggesting that it may hold other potential therapeutic targets.

Recent studies implicated the existence in adult human kidney of a population of renal progenitors with the potential to regenerate glomerular as well as tubular epithelial cells and characterized by coexpression of surface markers CD133 and CD24. Here, we demonstrate that CD133+CD24+ renal progenitors can be distinguished in distinct subpopulations from normal human kidneys based on the surface expression of vascular cell adhesion molecule 1, also known as CD106. CD133+CD24+CD106+ cells were localized at the urinary pole of Bowman's capsule, while a distinct population of scattered CD133+CD24+CD106- cells was localized in the proximal tubule as well as in the distal convoluted tubule. CD133+CD24+CD106+ cells exhibited a high proliferative rate and could differentiate toward the podocyte as well as the tubular lineage. By contrast, CD133+CD24+CD106- cells showed a lower proliferative capacity and displayed a committed phenotype toward the tubular lineage. Both CD133+CD24+CD106+ and CD133+CD24+CD106- cells showed higher resistance to injurious agents in comparison to all other differentiated cells of the kidney. Once injected in SCID mice affected by acute tubular injury, both of these populations displayed the capacity to engraft within the kidney, generate novel tubular cells, and improve renal function. These properties were not shared by other tubular cells of the adult kidney. Finally, CD133+CD24+CD106- cells proliferated upon tubular injury, becoming the predominating part of the regenerating epithelium in patients with acute or chronic tubular damage. These data suggest that CD133+CD24+CD106- cells represent tubular-committed progenitors that display resistance to apoptotic stimuli and exert regenerative potential for injured tubular tissue., (Copyright © 2012 AlphaMed Press.)

Objective: • To compare the frequency of T regulatory cells (Tregs) in peripheral blood of patients (pPB) affected by renal cell carcinoma (RCC) both with the frequency of Tregs found in PB of healthy donors (hPB) and that of Tregs present in tumour infiltrating lymphocytes (TILs). To verify in vitro the inhibitory activity of tumour isolated Tregs on the effector T cells and, finally, to assess the prognostic role of Treg frequency determination., Patients and Methods: • Treg frequency in hPB, pPB and TILs was evaluated in 30 patients and 20 healthy controls by measuring both membrane-CD25 and intracytoplasmic-Foxp3 expression by flow cytometry. • Treg inhibitory activity was evaluated by an in vitro proliferation assay performed on total, CD25-depleted mononuclear cells (MNC) and CD25-depleted MNC cultured in the presence of purified CD25(+) Tregs. • Finally, Treg frequency in pPB and TIL were correlated with conventional prognostic factors and scores of University of California Los Angeles and Kattan predictive models., Results: • Treg frequency was higher in TILs than in pPB (P= 0.002), whereas there were no important differences between hPB and pPB. CD25(+) cells isolated either from PB and tumours showed the ability to significantly suppress in vitro both proliferation and interferon-γ production by CD25-depleted MNC, thus demonstrating that they are active Tregs. • Treg frequency was found to significantly correlate both with pathological stage (pPB, P= 0.03; TIL, P= 0.04) and nuclear grade (TIL, P= 0.005), both for UCLA and Kattan models (all: P < 0.05 for both pPB and TIL)., Conclusion: • Treg frequency is significantly higher in TIL than in pPB of patients with RCC. Tregs showed in vitro an inhibitory activity on effector T cells isolated from kidney tumours. The increase in both peripheral and intratumoral Tregs in subjects affected with RCC were associated with worse prognosis., (© 2010 THE AUTHORS. JOURNAL COMPILATION © 2010 BJU INTERNATIONAL.)

Glomerular diseases account for 90% of end-stage kidney disease. Podocyte loss is a common determining factor for the progression toward glomerulosclerosis. Mature podocytes cannot proliferate, but recent evidence suggests that they can be replaced by renal progenitors localized within the Bowman's capsule. Here, we demonstrate that Notch activation in human renal progenitors stimulates entry into the S-phase of the cell cycle and cell division, whereas its downregulation is required for differentiation toward the podocyte lineage. Indeed, a persistent activation of the Notch pathway induced podocytes to cross the G(2)/M checkpoint, resulting in cytoskeleton disruption and death by mitotic catastrophe. Notch expression was virtually absent in the glomeruli of healthy adult kidneys, while a strong upregulation was observed in renal progenitors and podocytes in patients affected by glomerular disorders. Accordingly, inhibition of the Notch pathway in mouse models of focal segmental glomerulosclerosis ameliorated proteinuria and reduced podocyte loss during the initial phases of glomerular injury, while inducing reduction of progenitor proliferation during the regenerative phases of glomerular injury with worsening of proteinuria and glomerulosclerosis. Taken altogether, these results suggest that the severity of glomerular disorders depends on the Notch-regulated balance between podocyte death and regeneration provided by renal progenitors.

During kidney allograft rejection, CXC chemokine ligand 10 (CXCL10)-CXC chemokine receptor 3 (CXCR3) trafficking between peripheral blood and tissues initiates alloresponse and perpetuates a self-inflammatory loop; thus, CXCL10-CXCR3 axis could represent a pharmacologic target. In this perspective, immunosuppressors targeting graft-resident cells, beside immune cells, could be very advantageous. Vitamin D receptor (VDR) agonists exhibit considerable immunomodulatory properties. This study aimed to investigate whether elocalcitol and BXL-01-0029 could decrease the expression of CXCL10 in activated renal tubular cells in vitro and thus be useful in kidney allograft rejection treatment. Experiments were performed in human tubular renal cells stimulated with interferon-gamma + tumor necrosis factor-alpha with and without VDR agonists, tacrolimus, sirolimus, hydrocortisone, methylprednisolone, cyclosporin A and mycophenolate mofetil. CXCL10 protein secretion and gene expression were measured by ELISA and by quantitative PCR. Specific inhibitors were used to investigate intracellular pathways involved in tubular cells activation. For IC(50) determination and comparison, dose-response curves with VDR agonists, tacrolimus and mycophenolic acid were performed. Elocalcitol and BXL-01-0029 inhibited CXCL10 secretion by renal cells, without affecting cell viability, while almost all the immunosuppressors were found to be ineffective, except for tacrolimus and mycophenolate mofetil. BXL-01-0029 was the most potent drug and, notably, it was found to be capable of allowing reduction in tacrolimus-inhibitory doses. Our data suggest that BXL-01-0029 could potentially be a dose-reducing agent for conventional immunosuppressors in kidney rejection management.

Glomerular injury can involve excessive proliferation of glomerular epithelial cells, resulting in crescent formation and obliteration of Bowman's space. The origin of these hyperplastic epithelial cells in different glomerular disorders is controversial. Renal progenitors localized to the inner surface of Bowman's capsule can regenerate podocytes, but whether dysregulated proliferation of these progenitors contributes to crescent formation is unknown. In this study, we used confocal microscopy, laser capture microdissection, and real-time quantitative reverse transcriptase-PCR to demonstrate that hypercellular lesions of different podocytopathies and crescentic glomerulonephritis consist of three distinct populations: CD133(+)CD24(+)podocalyxin (PDX)(-)nestin(-) renal progenitors, CD133(+)CD24(+)PDX(+)nestin(+) transitional cells, and CD133(-)CD24(-)PDX(+)nestin(+) differentiated podocytes. In addition, TGF-beta induced CD133(+)CD24(+) progenitors to produce extracellular matrix, and these were the only cells to express the proliferation marker Ki67. Taken together, these results suggest that glomerular hyperplastic lesions derive from the proliferation of renal progenitors at different stages of their differentiation toward mature podocytes, providing an explanation for the pathogenesis of hyperplastic lesions in podocytopathies and crescentic glomerulonephritis.

The molecular basis for the exquisite sensitivity of testicular germ cell tumours of adolescents and adults (TGCTs), ie seminomas and non-seminomatous germ cell tumours, to chemo/radiotherapy has not been fully clarified so far. It has been suggested that it may be dependent on factors involved in the regulation of apoptosis. Seladin-1 is a multi-functional protein involved in various biological processes, including apoptosis. The aim of our study was to assess the expression of seladin-1 in different histological types of TGCTs, known to have varying treatment sensitivity, in order to establish whether this protein may influence cisplatin responsiveness in vitro. Seladin-1 expression levels, both at the mRNA and at the protein level, were higher in the adjacent normal parenchyma than in the pathological counterparts. In tumoural tissues, the level of expression differed among TGCT histological types. The highest tumour-expression level was found in teratoma, whereas the lowest was detected in seminoma, corresponding to the different chemo/and radiosensitivities of these tumour types. In common with other cancers, in TGCT-derived cell lines seladin-1 showed anti-apoptotic properties through inhibition of caspase-3 activation. We confirmed our results using a non-seminomatous cell line model (NT2) before and after differentiation with retinoic acid. Significantly higher seladin-1 expression was observed in the differentiated derivatives (teratoma) and an inverse relationship was found between seladin-1 expression and the amount of cleaved caspase-3. Seladin-1 silencing or overexpression in this cell line supports involvement of seladin-1 in cisplatin responsiveness. Seladin-1 silencing was associated with greater cisplatin responsiveness demonstrated by decreased cell viability and increased expression of apoptotic markers. In contrast, overexpression of seladin-1 was associated with a higher survival rate and a clear anti-apoptotic effect. In conclusion, we have demonstrated for the first time an important role for seladin-1 in the biology of TGCTs and provided new insights into cisplatin responsiveness of these tumours.

Depletion of podocytes, common to glomerular diseases in general, plays a role in the pathogenesis of glomerulosclerosis. Whether podocyte injury in adulthood can be repaired has not been established. Here, we demonstrate that in the adult human kidney, CD133+CD24+ cells consist of a hierarchical population of progenitors that are arranged in a precise sequence within Bowman's capsule and exhibit heterogeneous potential for differentiation and regeneration. Cells localized to the urinary pole that expressed CD133 and CD24, but not podocyte markers (CD133+CD24+PDX- cells), could regenerate both tubular cells and podocytes. In contrast, cells localized between the urinary pole and vascular pole that expressed both progenitor and podocytes markers (CD133+CD24+PDX+) could regenerate only podocytes. Finally, cells localized to the vascular pole did not exhibit progenitor markers, but displayed phenotypic features of differentiated podocytes (CD133-CD24-PDX+ cells). Injection of CD133+CD24+PDX- cells, but not CD133+CD24+PDX+ or CD133-CD24- cells, into mice with adriamycin-induced nephropathy reduced proteinuria and improved chronic glomerular damage, suggesting that CD133+CD24+PDX- cells could potentially treat glomerular disorders characterized by podocyte injury, proteinuria, and progressive glomerulosclerosis.

Acute kidney injury (AKI) is characterized by a sudden impairment of kidney function, which results in the retention of urea and other nitrogenous waste products and in the perturbation of extracellular fluid volume as well as electrolyte and acid-base homeostasis. The dysfunction and apoptosis of tubular epithelial cells are of key importance for the pathophysiological consequences of AKI. However, a growing body of evidence supports the contribution of altered renal vascular structure and function in potentially initiating and extending the initial tubular injury. Vascular injury and dysfunction result in alterations of renal oxygenation and hemodynamics that may have long-term effects in regards to renal function, predisposing to chronic kidney disease. There is growing evidence that endothelial progenitor cells (EPCs) may improve vascular regeneration in different ischemic organs, and recent data suggest that EPCs are mobilized after acute renal ischemia and recruited in ischemic kidney areas and can ameliorate AKI through both paracrine effects and repair of injured microvasculature. The loss of endothelial cell function may represent an important therapeutic target, in which EPCs may show potential importance in ameliorating the acute and chronic effects of ischemic AKI., (Copyright 2009 S. Karger AG, Basel.)

Background: The mechanisms by which human dendritic cells (DCs) activate a TH1-polarizing or TH2-polarizing program are still partially unclear., Objective: Study of the mechanisms responsible for the TH1/TH2-polarizing activity of human circulating myeloid DCs before and after ligation of their Toll-like receptors (TLRs)., Methods: IL-4 and IFN-gamma production by CD4+ T cells was assessed in cocultures with myeloid DCs before or after TLR triggering. Expression of Jagged-1 and Delta-4 Notch ligands and of GATA-3 and T-box expressed in T cells transcription factors was evaluated by real-time quantitative PCR. Signal transducer and activator of transcription 4 and 6 phosphorylation was assessed by flow cytometry. Knockdown of Jagged-1 or Delta-4 was performed by transfection of DCs with appropriate silencing mRNAs., Results: Myeloid immature DCs constitutively expressed Jagged-1, which induces in CD4+ T cells a TH2 polarization, as shown by Jagged-1 gene silencing. The TH2 polarization associated with high GATA-3/T-box expressed in T cells ratio and was at least partially dependent on the early induction of IL-4. Maturation of DCs by TLR ligation resulted in the reduction of Jagged-1 and upregulation of Delta-4, which was at least in part responsible for the polarization of CD4+ T cells to the TH1 phenotype., Conclusion: CD4+ T-cell responses are usually characterized by a prevalent TH2 phenotype unless TLRs are triggered on DCs by microbial components.

Recently, we have identified a population of renal progenitor cells in human kidneys showing regenerative potential for injured renal tissue of SCID mice. We demonstrate here that among all known chemokine receptors, human renal progenitor cells exhibit high expression of both stromal-derived factor-1 (SDF-1) receptors, CXCR4 and CXCR7. In SCID mice with acute renal failure (ARF), SDF-1 was strongly up-regulated in resident cells surrounding necrotic areas. In the same mice, intravenously injected renal stem/progenitor cells engrafted into injured renal tissue decreased the severity of ARF and prevented renal fibrosis. These beneficial effects were abolished by blocking either CXCR4 or CXCR7, which dramatically reduced the number of engrafting renal progenitor cells. However, although SDF-1-induced migration of renal progenitor cells was only abolished by an anti-CXCR4 antibody, transendothelial migration required the activity of both CXCR4 and CXCR7, with CXCR7 being essential for renal progenitor cell adhesion to endothelial cells. Moreover, CXCR7 but not CXCR4 was responsible for the SDF-1-induced renal progenitor cell survival. Collectively, these findings suggest that CXCR4 and CXCR7 play an essential, but differential, role in the therapeutic homing of human renal progenitor cells in ARF, with important implications for the development of stem cell-based therapies.

Factors influencing the susceptibility to mucosal candidiasis in HIV-infected patients are not clearly understood. Since in animal models of candidiasis the T helper (Th)1- or Th2-responses are protective or non-protective, respectively, this study was aimed to evaluate the cytokine profile of T-cell response to Candida albicans in the blood and lesional tissues of human immunodeficiency virus (HIV)-infected individuals, suffering, or not, from pseudomembranous oropharyngeal candidiasis (POPC), of HIV-negative women suffering from recurrent vaginal candidiasis (RVC) and of healthy controls. Peripheral blood mononuclear cells from HIV-infected and RVC patients proliferated to C. albicans antigen more than controls. Upon antigen activation, T cells from HIV-infected patients produced low interferon (IFN)-gamma, while only T cells from patients with POPC displayed high interleukin (IL)-4 and IL-5 production. POPC-positive patients also showed higher serum IgE levels than POPC-negative patients. T-cell clones generated from the oral mucosa of one HIV-infected patient with POPC produced IL-4, but not IFN-gamma (Th2 phenotype), whereas clones obtained from vaginal mucosa from one RVC patient or one healthy donor showed a Th1 profile. These findings, showing a non-protective Th0/Th2 response to C. albicans antigen in the blood and lesional mucosa of HIV-infected patients with POPC, may explain the high susceptibility of candidiasis in these subjects.

Objective: End-stage renal disease (ESRD) is a condition associated with thyroid disturbances both in function and morphology. Recent studies demonstrated that serum free triiodothyronine 3 (FT3) levels are negatively correlated with serum markers of inflammation and endothelial activation in patients with ESRD. However, no previous research evaluated serum thyroid function parameters in relation to kidney graft outcome, as we aim to do so in this study., Design: Serum FT3, free thyroxine 4 (FT4) and TSH levels were measured before transplantation in 196 kidney graft recipients., Results: The graft survival rate at 5 years for all patients was 92.3%. Kidney graft recipients with normally functioning grafts showed serum pretransplant thyroid parameters similar to patients who experienced graft failure. Life-time analysis was performed after stratification of patients according to pretransplant serum FT3 levels < 3.1 pmol/l or > 3.1 pmol/l. A significantly different 5-year death-censored graft survival rate (93.9%vs. 76.5% for patients with normal or low FT3 levels, respectively; P < 0.01) and similar survival rate (death of patients with functioning grafts) (21.1%vs. 5.9%; P = 0.288) were observed. No similar feature was found for FT4 or TSH, suggesting that the effect is not related to hypothyroidism but rather dependent upon inappropriately low FT3 levels. Pretransplant serum FT3 levels were similar in patients who experienced early acute rejections as compared with nonrejector patients., Conclusions: The results of this study demonstrate that among patients with ESRD undergoing kidney transplantation, those displaying lower pretransplant serum FT3 levels are at higher risk for subsequent graft failure. The demonstration of a predictive value of serum FT3 levels for graft survival suggests that measurement of pretransplant serum FT3 levels might represent a clinically useful parameter to identify patients with increased risk for graft failure.

Chemokines binding the CXCR3 receptor have been shown to inhibit angiogenesis via the CXCR3-B isoform, but the underlying molecular mechanisms are unknown. Aim of this study was to elucidate the effects of CXCR3-B on activation of members of the mitogen-activated protein kinase family, and to explore the relevance of defined signaling pathways to the angiostatic effects of CXCR3-B ligands. Human embryonic kidney (HEK) 293 cells were transfected with expression vectors encoding for CXCR3-A or CXCR3-B. In cells expressing CXCR3-A, CXCL10 (IP-10) at nanomolar concentrations induced activation of ERK, Akt, and Src, as previously described in human vascular pericytes. In HEK-293 cells expressing CXCR3-B, exposure to CXCL10 in the micromolar concentration range led to activation of the p38(MAPK) pathway, as indicated by phosphorylation of p38(MAPK) itself, and of MKK3/6 and MAPKAPK-2, that lie upstream and downstream of p38(MAPK), respectively. Similar results were obtained in cells stimulated with CXCL4 (PF4), a specific ligand of CXCR3-B. In contrast, CXCL4 was unable to activate p38(MAPK) in mock-transfected HEK-293 cells. Only a modest induction of ERK or JNK was observed upon CXCR3-B activation. In human microvascular endothelial cells, which selectively express CXCR3-B, in a cell cycle-dependent fashion, CXCL10 and CXCL4 increased the enzymatic activity of p38(MAPK). Pharmacologic inhibition of p38(MAPK) by SB302580 resulted in a significant increase in DNA synthesis and in reversal of the inhibitory action of CXCL10. In conclusion, the p38(MAPK) pathway is a downstream effector of CXCR3-B implicated in the angiostatic action of this chemokine receptor.

Bone marrow (BM)-derived mesenchymal stem cells (MSCs) are multipotent, nonhemopoietic progenitors that also possess regulatory activity on immune effector cells through different mechanisms. We demonstrate that human BM-derived MSCs expressed high levels of Toll-like receptors (TLRs) 3 and 4, which are both functional, as shown by the ability of their ligands to induce nuclear factor kappaB (NF-kappaB) activity, as well as the production of interleukin (IL)-6, IL-8, and CXCL10. Of note, ligation of TLR3 and TLR4 on MSCs also inhibited the ability of these cells to suppress the proliferation of T cells, without influencing their immunophenotype or differentiation potential. The TLR triggering effects appeared to be related to the impairment of MSC signaling to Notch receptors in T cells. Indeed, MSCs expressed the Notch ligand Jagged-1, and TLR3 or TLR4 ligation resulted in its strong downregulation. Moreover, anti-Jagged-1 neutralizing antibody and N[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT), an inhibitor of Notch signaling, hampered the suppressive activity of MSCs on T-cell proliferation. These data suggest that TLR3 and TLR4 expression on MSCs may provide an effective mechanism to block the immunosuppressive activity of MSCs and therefore to restore an efficient T-cell response in the course of dangerous infections, such as those sustained by double-stranded RNA viruses or Gram-negative bacteria, respectively.

Bone marrow-and adult kidney-derived stem/progenitor cells hold promise in the development of therapies for renal failure. Here is reported the identification and characterization of renal multipotent progenitors in human embryonic kidneys that share CD24 and CD133 surface expression with adult renal progenitors and have the capacity for self-renewal and multilineage differentiation. It was found that these CD24+CD133+ cells constitute the early primordial nephron but progressively disappear during nephron development until they become selectively localized to the urinary pole of Bowman's capsule. When isolated and injected into SCID mice with acute renal failure from glycerol-induced rhabdomyolysis, these cells regenerated different portions of the nephron, reduced tissue necrosis and fibrosis, and significantly improved renal function. No tumorigenic potential was observed. It is concluded that CD24+CD133+ cells represent a subset of multipotent embryonic progenitors that persist in human kidneys from early stages of nephrogenesis. The ability of these cells to repair renal damage, together with their apparent lack of tumorigenicity, suggests their potential in the treatment of renal failure.