Pathology of Podocytopathies Causing Nephrotic Syndrome in Children

Differentiating primary and secondary FSGS using non-invasive urine biomarkers

Background

Focal segmental glomerulosclerosis (FSGS) is divided into genetic, primary (p), uncertain cause, and secondary (s) forms. The subclasses differ in management and prognosis with differentiation often being challenging. We aimed to identify specific urine proteins/peptides discriminating between clinical and biopsy-proven pFSGS and sFSGS.

Methods

Sixty-three urine samples were collected in two different centers (19 pFSGS and 44 sFSGS) prior to biopsy. Samples were analysed using capillary electrophoresis-coupled mass spectrometry. For biomarker definition, datasets of age-/sex-matched normal controls (NC, n = 98) and patients with other chronic kidney diseases (CKDs, n = 100) were extracted from the urinary proteome database. Independent specificity assessment was performed in additional data of NC (n = 110) and CKD (n = 170).

Results

Proteomics data from patients with pFSGS were first compared to NC (n = 98). This resulted in 1179 biomarker (P < 0.05) candidates. Then, the pFSGS group was compared to sFSGS, and in a third step, pFSGS data were compared to data from different CKD etiologies (n = 100). Finally, 93 biomarkers were identified and combined in a classifier, pFSGS93. Total cross-validation of this classifier resulted in an area under the receiving operating curve of 0.95. The specificity investigated in an independent set of NC and CKD of other etiologies was 99.1% for NC and 94.7% for CKD, respectively. The defined biomarkers are largely fragments of different collagens (49%).

Conclusion

A urine peptide-based classifier that selectively detects pFSGS could be developed. Specificity of 95%-99% could be assessed in independent samples. Sensitivity must be confirmed in independent cohorts before routine clinical application.

Urinary matrix metalloproteinase-7 is a sensitive biomarker to evaluate renal tubular injury in patients with minimal change disease and focal segmental glomerulosclerosis

Objective

To explore the advantages of urinary matrix metalloproteinase-7 (MMP-7) in evaluating renal tubular injury in minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) patients compared with urinary cystatin C (CysC) and retinol-binding protein (RBP).

Methods

Serum and urine samples were collected from 20 healthy volunteers, and 40 MCD and 20 FSGS patients. Serum and urinary MMP-7 levels were measured by enzyme-linked immunosorbent assay. Urinary total protein, CysC and RBP levels were measured by automatic specific protein analyzer and compared with urinary creatinine level for calibration. The renal tissue serial sections were stained by MMP-7 immunohistochemistry and periodic acid-Schiff.

Results

Under light microscopy, MMP-7 granular weak positive expression was showed sporadically in the cytoplasm of a few renal tubular epithelial cells without obvious morphological changes in MCD patients, and MMP-7-positive expression was observed in the cytoplasm of some renal tubular epithelial cells in FSGS patients. There was no significant difference in serum MMP-7 level among the three groups. Compared with the control group, the urinary MMP-7 level in MCD patients was higher, but urinary CysC and RBP levels were not increased significantly. Compared with the control group and MCD patients, urinary MMP-7, CysC and RBP levels in FSGS patients were upregulated significantly.

Conclusions

Urinary MMP-7 could not only evaluate the mild renal tubular epithelial cells injury in MCD patients with massive proteinuria, but also evaluate the continuous renal tubular epithelial cells injury in FSGS patients.

Nephrotic Syndrome and Renin-angiotensin System: Pathophysiological Role and Therapeutic Potential

Idiopathic Nephrotic Syndrome (INS) is the most frequent etiology of glomerulopathy in pediatric patients and one of the most common causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD) in this population. In this review, we aimed to summarize evidence on the pathophysiological role and therapeutic potential of the Renin-Angiotensin System (RAS) molecules for the control of proteinuria and for delaying the onset of CKD in patients with INS. This is a narrative review in which the databases PubMed, Web of Science, and Sci- ELO were searched for articles about INS and RAS. We selected articles that evaluated the pathophysiological role of RAS and the effects of the alternative RAS axis as a potential therapy for INS. Several studies using rodent models of nephropathies showed that the treatment with activators of the Angiotensin-Converting Enzyme 2 (ACE2) and with Mas receptor agonists reduces proteinuria and improves kidney tissue damage. Another recent paper showed that the reduction of urinary ACE2 levels in children with INS correlates with proteinuria and higher concentrations of inflammatory cytokines, although data with pediatric patients are still limited. The molecules of the alternative RAS axis comprise a wide spectrum, not yet fully explored, of potential pharmacological targets for kidney diseases. The effects of ACE2 activators and receptor Mas agonists show promising results that can be useful for nephropathies including INS.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most frequent pediatric glomerular disease, affecting from 1.15 to 16.9 per 100,000 children per year globally. It is characterized by massive proteinuria, hypoalbuminemia, and/or concomitant edema. Approximately 85-90% of patients attain complete remission of proteinuria within 4-6 weeks of treatment with glucocorticoids, and therefore, have steroid-sensitive nephrotic syndrome (SSNS). Among those patients who are steroid sensitive, 70-80% will have at least one relapse during follow-up, and up to 50% of these patients will experience frequent relapses or become dependent on glucocorticoids to maintain remission. The dose and duration of steroid treatment to prolong time between relapses remains a subject of much debate, and patients continue to experience a high prevalence of steroid-related morbidity. Various steroid-sparing immunosuppressive drugs have been used in clinical practice; however, there is marked practice variation in the selection of these drugs and timing of their introduction during the course of the disease. Therefore, international evidence-based clinical practice recommendations (CPRs) are needed to guide clinical practice and reduce practice variation. The International Pediatric Nephrology Association (IPNA) convened a team of experts including pediatric nephrologists, an adult nephrologist, and a patient representative to develop comprehensive CPRs on the diagnosis and management of SSNS in children. After performing a systematic literature review on 12 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, recommendations were formulated and formally graded at several virtual consensus meetings. New definitions for treatment outcomes to help guide change of therapy and recommendations for important research questions are given.

Primary Focal Segmental Glomerulosclerosis Plasmas Increase Lipid Droplet Formation and Perilipin-2 Expression in Human Podocytes

Many patients with primary focal segmental glomerulosclerosis (FSGS) develop recurrence of proteinuria after kidney transplantation. Several circulating permeability factors (CPFs) responsible for recurrence have been suggested, but were never validated. We aimed to find proteins involved in the mechanism of action of CPF(s) and/or potential biomarkers for the presence of CPF(s). Cultured human podocytes were exposed to plasma from patients with FSGS with presumed CPF(s) or healthy and disease controls. Podocyte proteomes were analyzed by LC-MS. Results were validated using flow cytometry, RT-PCR, and immunofluorescence. Podocyte granularity was examined using flow cytometry, electron microscopy imaging, and BODIPY staining. Perilipin-2 protein expression was increased in podocytes exposed to presumed CPF-containing plasmas, and correlated with the capacity of plasma to induce podocyte granularity, identified as lipid droplet accumulation. Elevated podocyte perilipin-2 was confirmed at protein and mRNA level and was also detected in glomeruli of FSGS patients whose active disease plasmas induced podocyte perilipin-2 and lipid droplets. Our study demonstrates that presumably, CPF-containing plasmas from FSGS patients induce podocyte lipid droplet accumulation and perilipin-2 expression, identifying perilipin-2 as a potential biomarker. Future research should address the mechanism underlying CPF-induced alterations in podocyte lipid metabolism, which ultimately may result in novel leads for treatment.

Anti-ANGPTL3-FLD monoclonal antibody treatment ameliorates podocyte lesions through attenuating mitochondrial damage

Proteinuria, an indication of kidney disease, is caused by the malfunction of podocytes, which play a key role in maintaining glomerular filtration. Angiopoietin-like 3 (ANGPTL3) has been documented to have a cell-autonomous involvement in podocytes, and deletion of Angptl3 in podocytes reduced proteinuria in adriamycin-induced nephropathy. Here, we developed a monoclonal antibody (mAb) against ANGPTL3 to investigate its effects on podocyte injury in an ADR nephropathy mouse model and puromycin (PAN) induced podocyte damage in vitro. The mAb against the human ANGPTL3-FLD sequence (5E5F6) inhibited the binding of ANGPTL3-FLD to integrin β3. Treatment with the 5E5F6 mAb in ADR nephropathy mice mitigated proteinuria and led to a significant decline in podocyte apoptosis, reactive oxygen species (ROS) generation and mitochondrial fragmentation. In PAN-induced podocyte damage in vitro, the 5E5F6 mAb blocked the ANPGPLT3-mediated activation of integrin αvβ3 and Rac1, which regulated the mitochondrial homeostasis. Altogether, anti-ANGPLT3-FLD mAb attenuates proteinuria and podocyte lesions in ADR mice models, as well as PAN-induced podocyte damage, in part through regulating mitochondrial functions. Our study provides a therapeutic approach for targeting ANGPTL3 in proteinuric kidney disease.

MELAS syndrome with rare manifestations misdiagnosed as vasculitis in the absence of lactic acidosis: A case report

Introduction

The syndrome of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is one of the most common inherited mitochondrial disorders.

Presentation of case

A 33- year-old male was admitted due to edema, urinary retention, and reduce urinary output. The medical history included a pigmentary retinopathy (PR) at age of 22 and uveitis at age of 30, which were both treated with prednisolone. At age of 32, unapparent bilateral sensorineural hearing loss (SNHL) and symmetric basal ganglia calcifications were observed in neurologic study, and received prednisolone for the diagnosis of migraine and undefined vasculitis. Also, he described a right transient ischemic stroke (TIA) in the past 4 months. His family history included a dead brother, who had nearly similar components. Physical exam on admission corresponded with parkinsonism. The status points to MELAS but the genetic test was not available. Additional tests were applied, excluding all other disorders. Lactate was normal in serum and CSF. Kidney tests revealed a nephrotic syndrome and glomerulopathy, and the biopsy showed a single hyalinized glomerulus, which most likely suggests focal segmental glomerulosclerosis (FSGS). Muscle biopsy showed ragged red fibers.

Conclusion

Here, we report a challenging case of MELAS syndrome with rare manifestations including uveitis, PR, parkinsonism, and FSGS in the absence of lactic acidosis with unapparent muscle or hearing impairments. Since, clinicians might misdiagnose MELAS as vasculitis or other disorders due to its heterogeneous presentations, a proper investigations should guide the diagnosis of these conditions to reduce the delay of diagnosis and ineffective treatments.

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Clinicians might misdiagnose MELAS as vasculitis or other disorders due to its heterogeneous presentations.

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Muscle biopsy showed ragged red fibers with unapparent muscle impairment.

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MELAS can demonstrate a typical Parkinson's disease with extrapyramidal features.

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Relevant investigations should guide the diagnosis to reduce the delay of diagnosis and ineffective treatments.

CXCL16/ERK1/2 pathway regulates human podocytes growth, migration, apoptosis and epithelial mesenchymal transition

Primary nephrotic syndrome (PNS) is the commonest glomerular disease affecting children. Previous studies have confirmed that CXC motif chemokine ligand 16 (CXCL16) is involved in the pathogenesis of PNS. However, the exact mechanisms underlying the pathogenesis of PNS remain to be elucidated. Thus, the present study aimed to elucidate the role of CXCL16 in PNS. It was found that the expression of CXCL16 and extracellular signal‑regulated kinases 1 and 2 (ERK1/2) were significantly increased in clinical PNS renal tissues using reverse transcription‑quantitative PCR, western blot analysis and immunohistochemistry. Lentivirus overexpression or short hairpin RNA vector was used to induce the overexpression or knockdown of CXCL16 in podocytes, respectively. Overexpression of CXCL16 in podocytes could decrease the cell proliferation and increase the migration and apoptosis, whereas CXCL16 knockdown increased cell proliferation and decreased cell migration and apoptosis. Results of the present study further demonstrated that ERK2 protein expression was regulated by CXCL16. The knockdown of ERK2 expression reversed the effects of CXCL16 on the proliferation, apoptosis, migration and epithelial mesenchymal transition (EMT) of podocytes. Collectively, the findings of the present study highlighted that the CXCL16/ERK1/2 pathway regulates the growth, migration, apoptosis and EMT of human podocytes.

Klotho: A Possible Role in the Pathophysiology of Nephrotic Syndrome

Klotho, encoded by the klotho gene, is associated with phosphate homeostasis. Klotho acts as a co-receptor for FGF23 for binding to its receptors. With FGF23, klotho regulates the systemic mineral homeostasis by regulation of vitamin D and parathyroid hormone. The anti-inflammatory, antifibrotic and antioxidant properties of klotho give it a cardinal role in the development of various renal diseases. The protective effect of klotho has been evident in different types of nephropathy, including diabetic nephropathy, cyclosporine A-induced nephropathy, Calcineurin inhibitors-induced nephropathy, and renal ischemic-reperfusion injury. Nephrotic syndrome is distinguished by hypoproteinemia, proteinuria, and hypercholesterolemia as a result of the aberration of the glomerular filtration barrier. The various factors and pathways associated with the pathophysiology of the nephrotic syndrome have similarities with other types of nephropathy. Despite these similarities, the role of klotho in the pathology of nephrotic syndrome remains still unexplored. This minireview builds the case for the possible role of klotho in nephrotic syndrome. The review explores the possible pathways where klotho can play a major role by identifying the similarities in the pathophysiology of nephrotic syndrome and other types of nephropathy.

Role of Arachidonic Acid and Its Metabolites in the Biological and Clinical Manifestations of Idiopathic Nephrotic Syndrome

Studies concerning the role of arachidonic acid (AA) and its metabolites in kidney disease are scarce, and this applies in particular to idiopathic nephrotic syndrome (INS). INS is one of the most frequent glomerular diseases in childhood; it is characterized by T-lymphocyte dysfunction, alterations of pro- and anti-coagulant factor levels, and increased platelet count and aggregation, leading to thrombophilia. AA and its metabolites are involved in several biological processes. Herein, we describe the main fields where they may play a significant role, particularly as it pertains to their effects on the kidney and the mechanisms underlying INS. AA and its metabolites influence cell membrane fluidity and permeability, modulate platelet activity and coagulation, regulate lymphocyte activity and inflammation, preserve the permeability of the glomerular barrier, influence podocyte physiology, and play a role in renal fibrosis. We also provide suggestions regarding dietary measures that are able to prevent an imbalance between arachidonic acid and its parental compound linoleic acid, in order to counteract the inflammatory state which characterizes numerous kidney diseases. On this basis, studies of AA in kidney disease appear as an important field to explore, with possible relevant results at the biological, dietary, and pharmacological level, in the final perspective for AA to modulate INS clinical manifestations.

oxLDL promotes podocyte migration by regulating CXCL16, ADAM10 and ACTN4

Nephrotic syndrome (NS) is one of the most common causes of chronic kidney disease in the pediatric population. Hyperlipidemia is one of the main features of NS. The present study investigated the role of CXC motif chemokine ligand 16 (CXCL16) and ADAM metallopeptidase domain 10 (ADAM10) in oxidized low-density lipoprotein (oxLDL)-stimualted podocytes and the underlying mechanisms. CXCL16 and ADAM10 expression levels in oxLDL-treated podocytes were measured via reverse transcription-quantitative PCR and western blotting. Cell migration assays were conducted to assess the migration of oxLDL-treated podocytes. CXCL16 or ADAM10 overexpression and knockdown assays were conducted. The results indicated that oxLDL stimulation increased ADAM10 and CXCL16 expression levels, and enhanced podocyte migration compared with the control group. Moreover, CXCL16 and ADAM10 overexpression significantly increased podocyte migration and the expression of actinin-α4 (ACTN4) compared with the control groups. By contrast, CXCL16 and ADAM10 knockdown significantly reduced podocyte migration and the expression of ACTN4 compared with the control groups. The results suggested that oxLDL promoted podocyte migration by regulating CXCL16 and ADAM10 expression, as well as by modulating the actin cytoskeleton. Therefore, CXCL16 and ADAM10 may serve as novel therapeutic targets for primary nephrotic syndrome in children.

Protein misfolding in endoplasmic reticulum stress with applications to renal diseases

Protein misfolding may be the result of a variety of different processes that disrupt the ability of a protein to form a thermodynamically stable tertiary structure that allows it to perform its proper function. In this chapter, we explore the nature of a protein's form that allows it to have a stable tertiary structure, and examine specific mutation that are known to occur in the coding regions of DNA that disrupt a protein's ability to be folded into a thermodynamically stable tertiary structure. We examine the consequences of these protein misfoldings in terms of the endoplasmic reticulum stress response and resulting unfolded protein response. These conditions are specifically related to renal diseases. Further, we explore novel therapeutics, pharmacological chaperones, that are being developed to alleviate the disease burden associated with protein misfolding caused by mutations. These interventions aim to stabilize protein folding intermediates and allow proper folding to occur as well as prevent protein aggregation and the resulting pathophysiological consequences.

Mitochondrial biogenesis induced by the β2-adrenergic receptor agonist formoterol accelerates podocyte recovery from glomerular injury

Podocytes have limited ability to recover from injury. Here, we demonstrate that increased mitochondrial biogenesis, to meet the metabolic and energy demand of a cell, accelerates podocyte recovery from injury. Analysis of events induced during podocyte injury and recovery showed marked upregulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a transcriptional co-activator of mitochondrial biogenesis, and key components of the mitochondrial electron transport chain. To evaluate our hypothesis that increasing mitochondrial biogenesis enhanced podocyte recovery from injury, we treated injured podocytes with formoterol, a potent, specific, and long-acting β2-adrenergic receptor agonist that induces mitochondrial biogenesis in vitro and in vivo. Formoterol increased mitochondrial biogenesis and restored mitochondrial morphology and the injury-induced changes to the organization of the actin cytoskeleton in podocytes. Importantly, β2-adrenergic receptors were found to be present on podocyte membranes. Their knockdown attenuated formoterol-induced mitochondrial biogenesis. To determine the potential clinical relevance of these findings, mouse models of acute nephrotoxic serum nephritis and chronic (Adriamycin [doxorubicin]) glomerulopathy were used. Mice were treated with formoterol post-injury when glomerular dysfunction was established. Strikingly, formoterol accelerated the recovery of glomerular function by reducing proteinuria and ameliorating kidney pathology. Furthermore, formoterol treatment reduced cellular apoptosis and increased the expression of the mitochondrial biogenesis marker PGC-1α and multiple electron transport chain proteins. Thus, our results support β2-adrenergic receptors as novel therapeutic targets and formoterol as a therapeutic compound for treating podocytopathies.

Podocin and uPAR are good biomarkers in cases of Focal and segmental glomerulosclerosis in pediatric renal biopsies

There are controversies whether Minimal Change Disease (MCD) and Focal and Segmental Glomerulosclerosis (FSGS) are distinct glomerular lesions or different manifestations within the same spectrum of diseases. The uPAR (urokinase-type plasminogen activator receptor) and some slit diaphragm proteins may be altered in FSGS glomeruli and may function as biomarkers of the disease in renal biopsies. Thus, this study aims to evaluate the diagnostic potential of uPAR and glomerular proteins for differentiation between MCD and FSGS in renal pediatric biopsy. Renal biopsies from 50 children between 2 and 18 years old were selected, with diagnosis of MCD (n = 29) and FSGS (n = 21). Control group consisted of pediatric autopsies (n = 15) from patients younger than 18 years old, with no evidences of renal dysfunction. In situ expressions of WT1, nephrin, podocin and uPAR were evaluated by immunoperoxidase technique. Renal biopsy of patients with MCD and FSGS expressed fewer WT1 (p≤0.0001, F = 19.35) and nephrin (p<0.0001; H = 21.54) than patients in the control group. FSGS patients expressed fewer podocin than control (p<0.0359, H = 6.655). FSGS cases expressed more uPAR than each of control and MCD (p = 0.0019; H = 12.57) and there was a positive and significant correlation between nephrin and podocin (p = 0.0026, rS = 0.6502) in these cases. Podocin had sensitivity of 73.3% and specificity of 86.7% (p = 0.0068) and uPAR had sensitivity of 78.9% and specificity of 73.3% (p = 0.0040) for diagnosis of FSGS patients. The main limitation of the study is the limited number of cases due to the difficulty in performing biopsy in pediatric patients. Podocin and uPAR are good markers for FSGS and differentiate these cases from MCD, reinforcing the theory of distinct glomerular diseases. These findings suggest that podocin and uPAR can be used as biomarkers in the routine analysis of renal biopsies in cases of podocytopathies when the lesion (sclerosis) is not sampled.

Nanoscale Imaging of Kidney Glomeruli Using Expansion Pathology

Kidney glomerular diseases, such as the minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS), and other nephrotic syndromes, are typically diagnosed or confirmed via electron microscopy. Although optical microscopy has been a vital tool to examine clinical specimens for diagnoses in pathology for decades, the optical resolution is constricted by the physical diffraction limit of the optical microscope, which prevents high-resolution investigation of subcellular anatomy, such as of the podocyte tertiary foot processes. Here, we describe a simple, fast, and inexpensive protocol for nanoscale optical imaging of kidney glomeruli. The protocol is based on Expansion Pathology (ExPath), a new principle of microscopy that overcomes optical diffraction limit by chemically embedding specimens into a swellable polymer and physically expanding it homogenously prior to imaging. Our method uses only commercially available reagents, a conventional fluorescence microscope and it can be applied to both fixed-frozen or formalin-fixed paraffin embedded (FFPE) tissue sections. It requires minimal operative experience in a wet lab, optical microscopy and imaging processing. Finally, we also discuss challenges, limitations and prospective applications for ExPath-based imaging of glomeruli.

Curvature facilitates podocyte culture in a biomimetic platform

Most kidney diseases begin with abnormalities in glomerular podocytes, motivating the need for podocyte models to study pathophysiological mechanisms and new treatment options. However, podocytes cultured in vitro face a limited ability to maintain appreciable extents of differentiation hallmarks, raising concerns over the relevance of study results. Many key properties such as nephrin expression and morphology reach plateaus that are far from the in vivo levels. Here, we demonstrate that a biomimetic topography, consisting of microhemispheres arrayed over the cell culture substrate, promotes podocyte differentiation in vitro. We define new methods for fabricating microscale curvature on various substrates, including a thin porous membrane. By growing podocytes on our topographic substrates, we found that these biophysical cues augmented nephrin gene expression, supported full-size nephrin protein expression, encouraged structural arrangement of F-actin and nephrin within the cell, and promoted process formation and even interdigitation compared to the flat substrates. Furthermore, the topography facilitated nephrin localization on curved structures while nuclei lay in the valleys between them. The improved differentiation was also evidenced by tracking barrier function to albumin over time using our custom topomembranes. Overall, our work presents accessible methods for incorporating microcurvature on various common substrates, and demonstrates the importance of biophysical stimulation in supporting higher-fidelity podocyte cultivation in vitro.

The expressional disorder of the renal RAS mediates nephrotic syndrome of male rat offspring induced by prenatal ethanol exposure

This study aimed to prove that prenatal ethanol exposure (PEE) can induce nephrotic syndrome in male rat offspring and to explore the underlying intrauterine programming mechanisms. Pregnant Wistar rats were intragastrically administered ethanol (4 g/kg d) from gestational day (GD) 9 to GD 20, and the male fetuses were delivered by cesarean section at GD20 and the male adult offspring were euthanized at postnatal week (PW) 24. In vitro, the primary metanephric mesenchyme cells were treated with ethanol at concentrations of 15-60 mM. The results indicated that the kidneys of adult offspring in the PEE group exhibited glomerulosclerosis as well as interstitial fibrosis. The levels of serum creatinine and urine protein were elevated; the serum total cholesterol level was increased and the serum albumin concentration was reduced. In the fetal kidney, developmental retardation was presented in the PEE group via pathological examinations, accompanied by the expressional inhibition of the glial-cell-line-derived neurotrophic factor/c-ret tyrosine kinase receptor (GDNF/c-ret) signaling pathway. Although serum angiotensin II (Ang II) level and the gene expression of renal angiotensin-converting enzyme (ACE) were increased in the PEE group, the expression of renal angiotensin II type 2 receptor (AT₂R) was significantly inhibited, accompanied by a reduction in the H3K27ac level on the AT₂R gene promoter. In the non-classical renin-angiotensin system (RAS), the expression of renal angiotensin converting enzyme 2 (ACE2) and Mas receptor (MasR) were inhibited in the PEE group. The above changes of the classical and non-classical RAS all sustained from utero to adulthood. In vitro, ethanol elevated the gene expression of ACE and angiotensin II type 1a receptor (AT_1aR) whereas it reduced the expression of AT₂R, ACE2, and MasR, accompanied by a reduction in the H3K27ac level on AT₂R gene promoter. Taken together, these results suggested that PEE can induce fetal kidney developmental retardation and adult nephrotic syndrome, and direct regulation of ethanol to the renal RAS was involved in the mechanism of nephrotic syndrome induced by PEE.

Differentiating Primary, Genetic, and Secondary FSGS in Adults: A Clinicopathologic Approach

FSGS describes a renal histologic lesion with diverse causes and pathogenicities that are linked by podocyte injury and depletion. Subclasses of FSGS include primary, genetic, and secondary forms, the latter comprising maladaptive, viral, and drug-induced FSGS. Despite sharing certain clinical and histologic features, these subclasses differ noticeably in management and prognosis. Without an accepted nongenetic biomarker that discriminates among these FSGS types, classification of patients is often challenging. This review summarizes the clinical and histologic features, including the onset and severity of proteinuria as well as the presence of nephrotic syndrome, that may aid in identifying the specific FSGS subtype. The FSGS lesion is characterized by segmental sclerosis and must be differentiated from nonspecific focal global glomerulosclerosis. No light microscopic features are pathognomonic for a particular FSGS subcategory. The characteristics of podocyte foot process effacement on electron microscopy, while helpful in discriminating between primary and maladaptive FSGS, may be of little utility in detecting genetic forms of FSGS. When FSGS cannot be classified by clinicopathologic assessment, genetic analysis should be offered. Next generation DNA sequencing enables cost-effective screening of multiple genes simultaneously, but determining the pathogenicity of a detected genetic variant may be challenging. A more systematic evaluation of patients, as suggested herein, will likely improve therapeutic outcomes and the design of future trials in FSGS.

Difficult Renal Pathological Classification in a Case of Pediatric Nephrotic Syndrome

The underlying histopathology is very important in determining patient management, as the histopathology usually has direct repercussions on the treatment response and clinical course. However, the impact of the method used to assess renal biopsies, i.e., light microscopy (LM), immunofluorescence (IF), and electron microscopy (EM), on the occurrence of a difficult biopsy classification in the native kidneys of pediatric nephrotic patients is unknown. A 12-month-old Japanese boy was diagnosed with nephrotic syndrome (NS); he was administered prednisolone (60 mg/m²/day), and a continuous albumin infusion was started. A renal biopsy using LM revealed minimal change. However, an IF study showed granular staining for immunoglobulin G along the glomerular basement membrane. Therefore, he was diagnosed with membranous nephropathy (MN). As his proteinuria was so severe, we started immunosuppressant therapy and continued the albumin infusion for more than 2 months. However, he did not attain complete remission. A month later, EM examination of his renal biopsy showed extensive foot process fusion without electron-dense deposits. Although the result of the IF study suggested MN, the results of the LM and EM studies indicated minimal change. We finally diagnosed the patient with minimal change NS, in consideration of his clinical condition and course. Because of the failure of previous treatments, pulse steroid therapy was started. After five rounds of therapy the patient attained complete remission. A difficult renal biopsy finding classification, dependent on the diagnostic method used, might occur in the native kidneys of pediatric nephrotic patients. Therefore, a diagnosis should be made after considering all renal biopsy findings and the clinical course.

Adaptive self-organization in the embryo: its importance to adult anatomy and to tissue engineering

The anatomy of healthy humans shows much minor variation, and twin‐studies reveal at least some of this variation cannot be explained genetically. A plausible explanation is that fine‐scale anatomy is not specified directly in a genetic programme, but emerges from self‐organizing behaviours of cells that, for example, place a new capillary where it happens to be needed to prevent local hypoxia. Self‐organizing behaviour can be identified by manipulating growing tissues (e.g. putting them under a spatial constraint) and observing an adaptive change that conserves the character of the normal tissue while altering its precise anatomy. Self‐organization can be practically useful in tissue engineering but it is limited; generally, it is good for producing realistic small‐scale anatomy but large‐scale features will be missing. This is because self‐organizing organoids miss critical symmetry‐breaking influences present in the embryo: simulating these artificially, for example, with local signal sources, makes anatomy realistic even at large scales. A growing understanding of the mechanisms of self‐organization is now allowing synthetic biologists to take their first tentative steps towards constructing artificial multicellular systems that spontaneously organize themselves into patterns, which may soon be extended into three‐dimensional shapes.

Nephrin Loss Can Be Used to Predict Remission and Long-term Renal Outcome in Patients With Minimal Change Disease

Introduction

Minimal change disease is a common cause of nephrotic syndrome. In general, patients with minimal change disease respond to corticosteroids and have excellent long-term renal survival. However, some patients have less favorable outcome. These patients are often thought to have progressed to focal segmental glomerulosclerosis. We previously reported that a segmental loss of podocyte markers is present before the development of focal segmental glomerulosclerosis in a rat model. Here, we investigated whether loss of podocyte marker nephrin can serve as a biomarker for predicting poor outcome in patients with minimal change disease.

Methods

We obtained 47 kidney biopsy samples from patients diagnosed with minimal change disease and stained sections with periodic acid−Schiff and for nephrin. Nephrin loss was scored by 2 independent researchers who were blinded to clinical outcome. Clinical data were collected retrospectively, and nephrin loss was correlated with clinical follow-up data.

Results

Nephrin loss was present in 34% of the biopsy samples. During follow-up, patients with nephrin loss achieved remission less frequently (61%) compared to patients without (96%) (P = 0.002). Moreover, 5-year eGFR was lower in the patients with renal nephrin loss. The risk of eGFR decreasing to < 60 ml/min per 1.73m² increased with each percentage of glomeruli with nephrin loss (hazard ratio = 1.044, 95% confidence interval = 1.02−1.07).

Conclusion

These results indicate that nephrin loss in patients with minimal change disease can help predict both remission and long-term renal outcome.

Nanoscale imaging of clinical specimens using pathology-optimized expansion microscopy

Expansion microscopy (ExM), a method for improving the resolution of light microscopy by physically expanding the specimen, has not been applied to clinical tissue samples. Here we report a clinically optimized form of ExM that supports nanoscale imaging of human tissue specimens that have been fixed with formalin, embedded in paraffin, stained with hematoxylin and eosin (H&E), and/or fresh frozen. The method, which we call expansion pathology (ExPath), converts clinical samples into an ExM-compatible state, then applies an ExM protocol with protein anchoring and mechanical homogenization steps optimized for clinical samples. ExPath enables ~70 nm resolution imaging of diverse biomolecules in intact tissues using conventional diffraction-limited microscopes, and standard antibody and fluorescent DNA in situ hybridization reagents. We use ExPath for optical diagnosis of kidney minimal-change disease, which previously required electron microscopy (EM), and demonstrate high-fidelity computational discrimination between early breast neoplastic lesions that to date have challenged human judgment. ExPath may enable the routine use of nanoscale imaging in pathology and clinical research.

A unified pathogenesis for kidney diseases, including genetic diseases and cancers, by the protein-homeostasis-system hypothesis

Every cell of an organism is separated and protected by a cell membrane. It is proposed that harmony between intercellular communication and the health of an organism is controlled by a system, designated the protein-homeostasis-system (PHS). Kidneys consist of a variety of types of renal cells, each with its own characteristic cell-receptor interactions and producing characteristic proteins. A functional union of these renal cells can be determined by various renal function tests, and harmonious intercellular communication is essential for the healthy state of the host. Injury to a kind of renal cells can impair renal function and induce an imbalance in total body health. Every acute or chronic renal disease has unknown etiologic substances that are responsible for renal cell injury at the molecular level. The immune/repair system of the host should control the etiologic substances acting against renal cells; if this system fails, the disease progresses to end stage renal disease. Each renal disease has its characteristic pathologic lesions where immune cells and immune proteins, such as immunoglobulins and complements, are infiltrated. These immune cells and immune proteins may control the etiologic substances involved in renal pathologic lesions. Also, genetic renal diseases and cancers may originate from a protein deficiency or malfunctioning protein under the PHS. A unified pathogenesis for renal diseases, including acute glomerulonephritis, idiopathic nephrotic syndrome, immunoglobulin A nephropathy, genetic renal diseases such as Alport syndrome, and malignancies such as Wilms tumor and renal cell carcinoma, is proposed using the PHS hypothesis.

Minimal Change Disease

Minimal change disease (MCD) is a major cause of idiopathic nephrotic syndrome (NS), characterized by intense proteinuria leading to edema and intravascular volume depletion. In adults, it accounts for approximately 15% of patients with idiopathic NS, reaching a much higher percentage at younger ages, up to 70%-90% in children >1 year of age. In the pediatric setting, a renal biopsy is usually not performed if presentation is typical and the patient responds to therapy with oral prednisone at conventional doses. Therefore, in this setting steroid-sensitive NS can be considered synonymous with MCD. The pathologic hallmark of disease is absence of visible alterations by light microscopy and effacement of foot processes by electron microscopy. Although the cause is unknown and it is likely that different subgroups of disease recognize a different pathogenesis, immunologic dysregulation and modifications of the podocyte are thought to synergize in altering the integrity of the glomerular basement membrane and therefore determining proteinuria. The mainstay of therapy is prednisone, but steroid-sensitive forms frequently relapse and this leads to a percentage of patients requiring second-line steroid-sparing immunosuppression. The outcome is variable, but forms of MCD that respond to steroids usually do not lead to chronic renal damage, whereas forms that are unresponsive to steroids may subsequently reveal themselves as FSGS. However, in a substantial number of patients the disease is recurrent and requires long-term immunosuppression, with significant morbidity because of side effects. Recent therapeutic advances, such as the use of anti-CD20 antibodies, have provided long-term remission off-therapy and suggest new hypotheses for disease pathogenesis.

Association of Endothelin-1 rs5370 G>T gene polymorphism with the risk of nephrotic syndrome in children

Background:

Primary nephrotic syndrome (NS) is a common kidney disease in children. Objectives: The present study was aimed to investigate whether rs5370 G>T (lys198Asn) genetic variant of endothelin-1 (ET-1) is involved in the susceptibility to NS.

Patients and Methods:

This case-control study was performed on 138 patients with NS and 150 healthy children. Genomic DNA was extracted from whole blood using salting out method. Polymorphism of the ET-1 rs5370 G>T (lys198Asn) polymorphism detected by T-ARMS-PCR as well as PCR-RFLP method.

Results:

The results showed that the genotype and allelic frequencies of the ET-1 rs5370 G>T variant were not significantly different between cases and controls. Furthermore, subgroup analysis showed that rs5370 G>T variant was not associated with gender of patients. In NS patients the genotype was not associated with cholesterol, triglyceride, total protein and albumin levels.

Conclusions:

In conclusion, our findings indicate that ET-1 rs5370 G>T is not associated with NS. Further studies with larger sample sizes and different ethnicities are required to validate our findings.