Broadening the ocular phenotypic spectrum of ultra-rare BRPF1 variants: report of two cases

INTRODUCTION

BRPF1 gene on 3p26-p25 encodes a protein involved in epigenetic regulation, through interaction with histone H3 lysine acetyltransferases KAT6A and KAT6B of the MYST family. Heterozygous pathogenic variants in BRPF1 gene are associated with Intellectual Developmental Disorder with Dysmorphic Facies and Ptosis (IDDDFP), characterized by global developmental delay, intellectual disability, language delay, and dysmorphic facial features. The reported ocular involvement includes strabismus, amblyopia, and refraction errors. This report describes a novel ocular finding in patients affected by variants in the BRPF1 gene.

METHODS

We performed exome sequencing and deep ocular phenotyping in two unrelated patients (P1, P2) with mild intellectual disability, ptosis, and typical facies.

RESULTS

Interestingly, P1 had a Chiari Malformation type I and a subclinical optic neuropathy, which could not be explained by variations in other genes. Having detected a peculiar ocular phenotype in P1, we suggested optical coherence tomography (OCT) for P2; such an exam also detected bilateral subclinical optic neuropathy in this case.

DISCUSSION

To date, only a few patients with BRPF1 variants have been described, and none were reported to have optic neuropathy. Since subclinical optic nerve alterations can go easily undetected, our experience highlights the importance of a more detailed ophthalmologic evaluation in patients with BRPF1 variant.

Polyploid tubular cells initiate a TGF-β1 controlled loop that sustains polyploidization and fibrosis after acute kidney injury

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.

A Clinical Workflow for Cost-Saving High-Rate Diagnosis of Genetic Kidney Diseases

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.

Intravenous Glu-plasminogen attenuates cholesterol crystal embolism-induced thrombotic angiopathy, acute kidney injury and kidney infarction

BACKGROUND

Cholesterol crystal (CC) embolism causes acute kidney injury (AKI) and ischaemic cortical necrosis associated with high mortality. We speculated that sustaining the fibrinolytic system with Glu-plasminogen (Glu-Plg) could be a safe way to attenuate AKI and prevent ischaemic infarction upon CC embolism.

METHODS

We induced CC embolism by injecting CC into the left kidney artery of C57BL/6J mice. The primary endpoint was glomerular filtration rate (GFR).

RESULTS

Starting as early as 2 h after CC embolism, thrombotic angiopathy progressed gradually in the interlobular, arcuate and interlobar arteries. This was associated with a decrease of GFR reaching a peak at 18 h, i.e. AKI, and progressive ischaemic kidney necrosis developing between 12-48 h after CC injection. Human plasma Glu-Plg extracts injected intravenously 4 h after CC embolism attenuated thrombotic angiopathy, GFR loss as well as ischaemic necrosis in a dose-dependent manner. No bleeding complications occurred after Glu-Plg injection. Injection of an intermediate dose (0.6 mg/kg) had only a transient protective effect on microvascular occlusions lasting for a few hours without a sustained protective effect on AKI at 18-48 h or cortical necrosis, while 1.5 mg/kg were fully protective. Importantly, no bleeding complications occurred.

CONCLUSIONS

These results provide the first experimental evidence that Glu-Plg could be an innovative therapeutic strategy to attenuate thrombotic angiopathy, AKI, kidney necrosis and potentially other clinical manifestations of CC embolism syndrome.

Tubular cell polyploidy protects from lethal acute kidney injury but promotes consequent chronic kidney disease

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.

Acute kidney injury is frequent, often fatal and can leave survivors with chronic kidney disease. Here the authors show that tubular cell polyploidy reduces early fatality sustaining residual function but promotes chronic kidney disease, which can be prevented by blocking YAP1

Differentiation of crescent-forming kidney progenitor cells into podocytes attenuates severe glomerulonephritis in mice

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.

MO1057: Cost-Analysis of a Clinical Workflow for Diagnosis of Inherited Kidney Diseases

BACKGROUND AND AIMS

In the last decade, the use of whole-exome sequencing techniques (WES) has provided many insights into inherited kidney diseases that are thought to represent at least 10%–15% of cases of end-stage CKD [1]. However, among others, cost concerns limit the widespread of genomics use in daily practice [1, 2]. Publicly funded genomic testing is restricted in most health care systems [2]. Consequently, the evaluation of cost-effectiveness is urgently required in order to establish genomic sequencing as a standard diagnostic test for nephropathic patients.

The aim of this study was to perform a cost-analysis of genetic testing use in a diagnostic workflow.

METHOD

We recently set up a diagnostic workflow for the selection of patients that should undergo genetic testing in the suspicion of a genetic disease. This algorithm is applied by a network of nephrology centres on the regional territory. Selected patients are referred to a tertiary centre, Meyer University Hospital of Florence (Italy), for genetic diagnosis by WES.

We enrolled paediatric and adult patients referred to the outpatient service based on the pre-specified clinical criteria. All the patients underwent genetic testing from 2018 to June 2021.

We conducted a cost-analysis in two parts: (1) assessment of the cost-effectiveness cut-off; and (2) exploratory modeled cost-analysis using WES in different phases of the diagnostic trajectory.

As a surrogate of the cost-effectiveness analysis, we calculated the cost-effectiveness cut-off, indicating the amount of expenses for diagnostic examinations at which WES sequencing would be cost-effective.

For the exploratory cost-analysis, we defined two diagnostic trajectories: Model I, considering an ideal complete diagnostic pathway and late use of WES; and Model II, considering an early use of WES allowing to save a certain number of examinations. Genomic and non-genomic investigations were obtained from local practice, available clinical evidence and guidelines. We then calculated the cost per diagnosis according to each Model for different clinical categories and for the whole study population using the diagnostic rates of this study.

We considered only direct medical costs, based on the regional health reimbursement system, which is comprehensive of materials and human resources. The prices are expressed in euros. The analysis was conducted from a regional healthcare system perspective.

RESULTS

The analysis included 402 patients. WES performed after the standard non-conclusive diagnostic work-up (at a mean cost of €2992/patient) resulted in cost-effectiveness at a cost of <€2004/patient in the study population. Looking at different clinical categories, WES was cost-effective at a cost ranging from €3336 to €770.

Overall, the exploratory cost-analysis showed Model II as cost reducing in comparison to Model I. The mean cost per diagnosis in Model I with late use of WES was estimated at €7700. Early use of WES in Model II had an estimated cost per diagnosis of €6340, leading to a cost saving of €1360/patient tested. Regarding the single clinical categories, the highest cost saving per diagnosis was obtained in podocytopathies (Model I: €13.010 versus Model II: €7261). The early use of WES produced a slight increase in estimated costs per diagnosis for tubulopathies, as well as for ciliopathies, while for syndromic CKD and metabolic kidney disorders, the costs per diagnosis did not result in major changes.

CONCLUSION

Early use of WES in the diagnostic pathway of inherited diseases, guided by a framework of specific criteria, is feasible and has the potential to produce substantial cost savings in healthcare.

FC036: A Clinical Workflow for Selection of Patients and Cost-Efficient Diagnosis of Genetic Kidney Diseases

BACKGROUND AND AIMS

With the spread of whole-exome sequencing techniques (WES), genetic kidney diseases are increasingly recognized across all age groups. However, accessibility, interpretation of results and costs limit the widespread of genomics use in daily practice [1]. In the very last years, first experiences in the implementation of renal genetic services have been started [2]. In this work, we explored the feasibility and diagnostic performance of a service delivery model based on a territorial network for patients’ selection, followed by referral to the renal genetic clinic of a tertiary centre for WES, results interpretation and counseling. We hypothesized that higher diagnostic yield and cost-effectiveness could be achieved by implementing a workflow that could solve three problems: (1) Give clear indications to the nephrologist about which patients with kidney diseases should undergo genetic testing, (2) Increase the rate and accuracy of genetic testing and evaluate the clinical impact and (3) Identify the kidney diseases for which early genetic testing is not only clinically, but also economically convenient for the healthcare provider based on pre-specified clinical criteria for tertiary centre referral.

METHOD

We set up a multi-step diagnostic workflow. We established specific clinical criteria for evaluation of patients who should undergo genetic testing on the suspicion of a genetic disease by a network of nephrology centres. Patients selected were referred to a tertiary centre for genetic diagnosis by WES, reverse-phenotyping and multidisciplinary board analysis.

This workflow has been applied to pediatric and adult patients with kidney diseases belonging to eight clinical categories (Podocytopathies, Collagenopathies, Tubulopathies, Unknown familial nephropathies, Ciliopathies, Congenital anomalies of the kidney and urinary tract, Syndromic chronic kidney disease and Metabolic kidney disorders). We recorded clinical-laboratory-radiological information of patients included. We also performed a cost-analysis of the diagnostic workflow modelling the possible economic saving using it.

RESULTS

We included 402 patients, of note, 188 patients were female (46.8%) and 132 patients (33%) were >16 years of age. We obtained a global diagnostic yield of 69.2% (278–402), with category-specific diagnostic rates ranging from 38.5% to 87%. By reverse phenotyping, we reclassified diagnoses in 74–278 (26.6%) patients, thus increasing diagnostic accuracy. Overall, reverse phenotyping increased the diagnostic rate in an average of 20% of cases, irrespective of the age at clinical onset of the disease. Diagnostic yield was independent of the age at the onset of kidney disease. Genetic testing was offered as cascade screening to 67 families, providing a genetic diagnosis in 62 family members with previously unsuspected or unspecified kidney disorders. The clinical work-up changed and was redirected on average in 50% of patients. In 11.5% of patients, the results of genetic testing helped in guiding kidney transplant decisions. Finally, cost-analysis showed that our workflow is cost-efficient allowing to potentially save a mean of 1360 euros per patient.

CONCLUSION

Ordering genetic testing, interpreting results, counselling patients and their families, and tailoring clinical management (i.e. personalized nephrology) is feasible and saves costs in a real-world setting.

OUP accepted manuscript

Podocytopathies are glomerular disorders in which podocyte injury drives proteinuria and progressive kidney disease. They encompass a broad spectrum of aetiologies, resulting in pathological pictures of minimal-changes, focal segmental glomerulosclerosis, diffuse mesangial sclerosis or collapsing glomerulopathy. Despite improvement in classifying podocytopathies as a distinct group of disorders, the histological definition fails to capture the relevant biological heterogeneity underlying each case, manifesting as extensive variability in disease progression and response to therapies. Increasing evidence suggests that podocytopathies can result from a single causative factor or a combination of multiple genetic and/or environmental risk factors with different relative contributions, identifying complex physiopathological mechanisms. Consequently, the diagnosis can still be challenging. In recent years, significant advances in genetic, microscopy and biological techniques revolutionized our understanding of the molecular mechanisms underlying podocytopathies, pushing nephrologists to integrate innovative information with more conventional data obtained from kidney biopsy in the diagnostic workflow. In this review, we will summarize current approaches in the diagnosis of podocytopathies, focusing on strategies aimed at elucidating the aetiology underlying the histological picture. We will provide several examples of an integrative view of traditional concepts and new data in patients with suspected podocytopathies, along with a perspective on how a reclassification could help to improve not only diagnostic pathways and therapeutic strategies, but also the management of disease recurrence after kidney transplantation. In the future, the advantages of precision medicine will probably allow diagnostic trajectories to be increasingly focused, maximizing therapeutic results and long-term prognosis.

Guidelines for Genetic Testing and Management of Alport Syndrome

Genetic testing for pathogenic COL4A3-5 variants is usually undertaken to investigate the cause of persistent hematuria, especially with a family history of hematuria or kidney function impairment. Alport syndrome experts now advocate genetic testing for persistent hematuria, even when a heterozygous pathogenic COL4A3 or COL4A4 is suspected, and cascade testing of their first-degree family members because of their risk of impaired kidney function. The experts recommend too that COL4A3 or COL4A4 heterozygotes do not act as kidney donors. Testing for variants in the COL4A3-COL4A5 genes should also be performed for persistent proteinuria and steroid-resistant nephrotic syndrome due to suspected inherited FSGS and for familial IgA glomerulonephritis and kidney failure of unknown cause.

Consensus statement on standards and guidelines for the molecular diagnostics of Alport syndrome: refining the ACMG criteria

The recent Chandos House meeting of the Alport Variant Collaborative extended the indications for screening for pathogenic variants in the COL4A5, COL4A3 and COL4A4 genes beyond the classical Alport phenotype (haematuria, renal failure; family history of haematuria or renal failure) to include persistent proteinuria, steroid-resistant nephrotic syndrome, focal and segmental glomerulosclerosis (FSGS), familial IgA glomerulonephritis and end-stage kidney failure without an obvious cause. The meeting refined the ACMG criteria for variant assessment for the Alport genes (COL4A3-5). It identified 'mutational hotspots' (PM1) in the collagen IV α5, α3 and α4 chains including position 1 Glycine residues in the Gly-X-Y repeats in the intermediate collagenous domains; and Cysteine residues in the carboxy non-collagenous domain (PP3). It considered that 'well-established' functional assays (PS3, BS3) were still mainly research tools but sequencing and minigene assays were commonly used to confirm splicing variants. It was not possible to define the Minor Allele Frequency (MAF) threshold above which variants were considered Benign (BA1, BS1), because of the different modes of inheritances of Alport syndrome, and the occurrence of hypomorphic variants (often Glycine adjacent to a non-collagenous interruption) and local founder effects. Heterozygous COL4A3 and COL4A4 variants were common 'incidental' findings also present in normal reference databases. The recognition and interpretation of hypomorphic variants in the COL4A3-COL4A5 genes remains a challenge.

Acute kidney injury promotes development of papillary renal cell adenoma and carcinoma from renal progenitor cells

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.

MO033WHOLE-EXOME SEQUENCING AS A FIST-LINE DIAGNOSTIC TOOL IN BARTTER AND GITELMAN SYNDROME

Background and Aims

Bartter (BS) and Gitelman syndrome (GS) are autosomal recessive rare inherited disorders characterized by hypokalemic metabolic alkalosis and secondary hyperaldosteronism. The primary defect is a genetically determined impairment of sodium chloride reabsorption in the renal tubule, thus resulting in salt loss, dehydration and acid-base homeostasis perturbations.

Although the diagnosis can be suspected based on presenting features, the clinical diagnosis of BS and GS can be challenging, as they are rare and phenotypically overlapping. As a consequence, the current clinical classification lacks of specificity and genetic testing represents the gold standard for the diagnosis. Driven by the rapidly decreasing costs and turn-around time, next-generation sequencing technologies are increasingly utilized in diagnostics and research of inherited tubulopathies, including BS and GS. Recently, sequencing of selected gene panels provided the advantage of achieving high coverage of genes of interest at lower costs, providing high diagnostic yield and new insights into the phenotypic spectrum of these rare disorders. However, whole-exome (WES) is not routinely performed for the molecular diagnosis of BS and GS. The aim of our study was to assess the diagnostic performance of WES in BS and GS and to establish genotype-phenotype correlations.

Method

We performed WES in all consecutive patients referred for genetic testing with a clinical suspect of BS or GS. Variant prioritization was carried out according to the American College of Medical Genetics and Genomics guidelines (ACMG). Parents and first-degree relatives were included, whenever available. Demographic, clinical and laboratory data were collected retrospectively, in order to establish genotype-phenotype correlations.

Results

We enrolled 50 patients (22 males, 46 Caucasians) with a clinical diagnosis of BS (19), GS (24) or BS/GS (7). All the patients showed hypokalemic metabolic alkalosis at onset (serum bicarbonate=29.5 mEq/l ± 4.4, potassium= 2.7 mEq/l ± 0.6). The median age at clinical diagnosis was 7 years (range 0-67 years). Three patients had familial history of tubulopathies. WES showed pathogenic variants in 42/50 patients (84%), thus establishing a conclusive diagnosis. Interestingly, a dedicated analytic pipeline allowed us to identify copy number variations (CNVs) in 7/42 patients with a confirmed genetic diagnosis. In detail, WES allowed us to confirm the clinical diagnosis in 33/50 patients, with an improvement in classification in at least 14 cases (i.e. subtype I-V of BS). In 9 additional patients, genetic testing changed the clinical diagnosis: 6 patients with a clinical of BS turned out to have pathogenic variants in SLC12A3, resulting in GS; in 3 patients, genetic testing revised the clinical diagnosis indicating inherited disorders outside the BS/GS spectrum (HELIX syndrome, Primary familial hypoparatiroidism, Type 2 renal hypomagnesemia). Only 38% of patients with a genetic diagnosis of BS showed nephrocalcinosis. Strikingly, this was present in 8% of patients with GS. On the other hand, hypomagnesemia, a distinctive feature of GS, was similarly distributed among BS and GS patients (45% vs. 68%, respectively). Finally, although patients with GS showed a median age at onset higher than patients with BS, some overlap did exist, making differential diagnosis challenging at single-patient level.

Conclusion

The results of our study demonstrate that WES ensures a high diagnostic yield (84%) in patients with a clinical diagnosis of BS or GS, especially if coupled with analysis of CNVs. This approach showed to be useful in dealing with the phenotypic heterogeneity typical of these rare disorders, improving differential diagnosis by detecting phenocopies also outside the BS/GS spectrum, enabling additional specific work-up, genetic counseling, and screening of at-risk relatives.

Collapsing Glomerulopathy as a Complication of Type I Interferon-Mediated Glomerulopathy in a Patient With RNASEH2B-Related Aicardi-Goutières Syndrome

Aicardi-Goutières syndrome (AGS) is a well-characterized monogenic type I interferonopathy presenting with prominent neurologic manifestations. Among extraneurologic features, renal involvement has been described in only 1 patient with an IFIH1 mutation in whom membranous nephropathy developed. The pathogenic role of augmented interferon (IFN) signaling in tissues other than the central nervous system remains to be elucidated. We report a case of collapsing glomerulopathy in a 15-year-old girl affected by AGS with RNASEH2B mutation (an alanine-to-threonine change at amino acid 177), which led to kidney failure. The patient had no lupus-like features and lacked the APOL1 G1 and G2 risk alleles. Kidney biopsy showed findings consistent with collapsing glomerulopathy. MxA, a protein involved in antiviral immunity and induced by type I IFNs, was selectively expressed in CD133-positive parietal epithelial cells (PECs) but not in podocytes that stained for synaptopodin or in other glomerular cells. MxA also colocalized within pseudocrescents with CD44, a marker of PEC activation involved in cellular proliferation, differentiation, and migration and in glomerular scarring. Our findings suggest that collapsing glomerulopathy can be a complication of the type I interferonopathy AGS and that a constitutively enhanced type I IFN response in CD133-positive PECs can drive collapsing glomerulopathy.

Look Alike, Sound Alike: Phenocopies in Steroid-Resistant Nephrotic Syndrome

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.

[Eculizumab as rescue therapy for lupus nephritis-related thrombotic microangiopathy]

Thrombotic microangiopathy (TMA) is a frequent and severe complication in systemic lupus erythematosus (SLE). It is reported in almost 20-25% of renal biopsies of patients with lupus nephritis (LN) and is associated with a poor renal prognosis. We report the case of a patient suffering from an aggressive form of proliferative LN in association with thrombotic microangiopathy (TMA-LN), who was resistant to standard combined immunosuppressive treatment with corticosteroids and cyclophosphamide, as well as to plasma exchange (PEX). Eculizumab was given as a rescue therapy with an optimal clinical response. We performed a systematic review of the literature and identified 11 papers, published between 2011 and 2018, with a total of 20 patients, in which eculizumab was used, always as rescue therapy, to treat TMA-LN. All reported cases showed a positive clinical response to eculizumab with a high rate of remission. Even if sparse, available clinical cases and case series support the use of eculizumab in highly selected cases as rescue treatment for LN-TMA resistant to conventional combined immunosuppressive treatment.

Reverse Phenotyping after Whole-Exome Sequencing in Steroid-Resistant Nephrotic Syndrome

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.

A microRNA profile of pediatric glioblastoma: The role of NUCKS1 upregulation

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.

Restoration of Ultrafiltration Capacity of Peritoneal Membrane in Patients on CAPD

Among 55 uremic patients who entered our CAPD program, 7 of them showed a reduction or loss of the ultrafiltration capacity (UF) of the peritoneal membrane (PM). They have been treated with high dose of Furosemide (F) to force residual urine output. Four appeared «responders» to drug administration with a significant increase in urine volume, Na excretion and, within a week period gained their dry body weight (BW).

In the remaining 3 patients drug therapy resulted ineffective, and fluid removal was obtained by hemofiltration (HF).

In both groups we noted an increase in the UF capacity of PM when their dry BW was obtained either by pharmacological or technical approach.

These results support the assumption that the overhydration status of the PM plays a major role in maintaining the UF process.

Spontaneous Plasma Exchange by Gravity

Lysagth et al have reported a semplified model of spontaneous plasmapheresis by placing between an A-V shunt a conventional plasmafilter. On the basis of this experience we tried to make a further semplification of this apparatus using a single venous puncture, obtaining by gravity sufficient transmembrane pressure for plasma separation. By alternatively lowering and elevating the system, plasma is separated from the blood and packed red cells are reinfused after a new pass through the filter with FFP or plasma substitutes.

Effect of epoetin on HO-1 mRNA level and plasma antioxidants in hemodialysis patients

OBJECTIVE

Patients with renal failure and undergoing hemo- (HD) or peritoneal dialysis are under oxidative stress which is thought to contribute to the long-term complications noted in this patient population. One effect of HD-induced oxidative stress is via red blood cell (RBC) membrane lipid peroxidation leading to RBC destruction and anemia. Interaction of this oxidative stress with epoetin (EPO) treatment to increase RBC number and Hb concentration remains unexplored.

PATIENTS AND METHODS

This preliminary study used RT-PCR as well as colorimetric based assay approaches to evaluate the effect of EPO-alpha treatment on markers of oxidative stress in hemodialysis patients. Eighteen patients (12 males, 6 females, age range 45 - 68), were treated with EPO-alpha (Eprex) 50 UI/kg thrice weekly over an 8-month study period. Monocytes were isolated at baseline, then monthly thereafter, monocyte heme-oxygenase-1 (HO-1) and plasma Hb and antioxidant power (AOP) were determined.

RESULTS AND CONCLUSIONS

Treatment with EPO increased Hb (9.4 +/- 0.7 g/dl to 10.9 +/- 0.5, mean +/- SD p < 0.001). In addition, both monocyte HO-1 mRNA (0.34 +/- 0.08 vs. 0.59 +/- 0.02 d.u. p < 0.001) and plasma AOP (1,379.8 +/- 175 micromol/l to 1,624 +/- 170, p < 0.04) increased. While AOP changes showed no correlation with other indices, increases in HO-1 and Hb were positively correlated using 2 different measures: delta Hb (peak Hb - baseline Hb) vs. delta HO-1 (peak HO-1 mRNA - baseline HO-1 mRNA) as well as delta Hb(5 months-baseline) vs. delta HO-1 (5 months - baseline) mRNA (r = 0.81, p < 0.001 and r = 0.76, p < 0.001; respectively). In conclusion, the increases upon EPO treatment of both HO-1 gene expression and plasma AOP as well as the significant correlation between delta Hb and delta HO-1 mRNA suggest that EPO treatment reduces oxidative stress via a combination of effects. These could potentially include effects on oxidative stress directly as well as effects on the levels and types of antioxidants present in plasma.

Chemiluminescent and Colorimetric Detection of Erwinia amylovora by Immunoenzymatic Determination of PCR Amplicons from Plasmid pEA29

A molecular diagnostic technique (polymerase chain reaction enzyme-linked immunosorbent assay [PCR-ELISA]) for detection of Erwinia amylovora was developed. The protocol is based on the immunoenzymatic determination of PCR products. For in vitro amplification, we used previously published primers able to detect the cryptic plasmid pEA29, which is ubiquitous in E. amylovora. Amplicons were labeled with 11-digoxigenin (DIG)-dUTP during the amplification reaction, captured by hybridization to a biotinylated oligonucleotide in streptavidin-coated ELISA microplates, and then detected with anti-DIG-Fab'-peroxidase conjugated antibodies. The specificity of the assay was verified using E. amylovora strains from different host plants and geographical origins in addition to other plant-associated bacteria (either phytopathogenic or saprophytic) belonging to the genera Erwinia, Pseudomonas, and Agrobacterium. In detection threshold experiments with pure cultures, as few as 30 and 3 CFU/reaction tube were detected when the ABTS (colorimetric) and ECL (chemiluminescent) detection assays, respectively, were used. PCR-ELISA coupled with chemiluminescent detection was able to detect as few as 4 × 10² CFU/g of artificially infested pear twigs. The assay was further shown to be suitable for detection of E. amylovora in naturally infected plant organs, and the results were compared to those obtained using standard PCR assays with electrophoretic separation of amplicons.

Combined hemodialysis-hemoperfusion in the treatment of secondary hyperparathyroidism of uremic patients

Hyperparathyroidism and its related symptoms such as bone pain, soft-tissue calcifications and pruritus often get worse during dialysis treatment. We have treated 12 cases among 170 patients on regular dialysis by using coated charcoal (150 g/cartridge) in combination with standard hemodialysis. During a 6-month treatment period, without changing medical therapy and diet regime, the patients reported a marked relief from pruritus. Parathyroid hormone (PTH) levels changed from 552 +/- 86 to 364 +/- 62 pg/ml (p less than 0.001) compared to the pretreatment period, Plasma PO4(3-) changed in the same period from 6.9 +/- 1.8 to 4.6 +/- 1.5 mg/dl (p less than 0.005). The results obtained indicate a relationship between PTH, serum plasma PO4(3-) levels and pruritus. The mechanism which may be involved is that hemoperfusion removes PTH excess by absorption. Our treatment reducing PTH levels resulted in a marked relief from pruritus and other symptoms, suggesting that patients in this condition, before undergoing surgical parathyroidectomy, may be usefully treated with this therapeutic modality.

On-line bioelectric impedance during haemodialysis: monitoring of body fluids and cell membrane status

We have measured by a computed integrated system (BIA 109, RJL AKERN) the changes of bio-impedance (BI) deriving from a tetrapolar system working on 800 microA, 50 kHz current, in 23 haemodialysed patients. Resistance (R) and reactance (Xc) have been continuously monitored during haemodialysis in each patient. Resistance was strictly inversely correlated to the decrease of body weight (r = 0.82). Also, Xc increased almost constantly. In most of the patients the increase of Xc was proportionally greater than R, resulting in an increase of phase angle (PA). However, Xc showed a transient decrease in response to seven severe symptomatic hypotensive episodes, whereas R maintained the increasing trend, causing a sharp reduction of phase angle. As Xc is an expression of storage of electrical charge by the cells acting as condensers, and phase angle quantifies the active capacitive component in relation to passive electrical resistance, these parameters may be important to evaluate cell membrane function. In fact, the univocal increase of R, Xc and phase angle observed during normal unevenful haemodialysis probably indicates improvement of cellular activities due to the depurative treatment. On the contrary, the transient reduction of Xc and phase angle observed during hypotensive crises may be an expression of cellular distress because of a too rapid ultrafiltration.

Removal of phosphate (Pi) by either bicarbonate dialysis or biofiltration in uremics

The kinetics of extra and intracellular red blood cell (RBC) Pi and its removal by different therapeutic modalities were evaluated in 30 uremic patients over a 6 mo. period. Acetate hemodialysis alone, combined with hemoperfusion, or associated once a week with plasma-perfusion sessions using an activated bauxite cartridge, bicarbonate dialysis either in single pass or in recirculating system (40 L) and biofiltration, were the depurative treatments employed. The treatments with acetate buffer showed a temporary intracellular shift of Pi at the end of the sessions with post-dialytic plasma Pi rebound. This was not evident with bicarbonate buffer and biofiltration where acidosis was corrected better, and similarly during plasma perfusion treatment because blood pH remained unchanged. These findings may explain the better plasma Pi level at the end of our study with these later therapeutic models compared to acetate dialysis alone or combined with hemoperfusion. In these conditions Pi removal is limited by the correction of acidosis which implies acetate metabolism with ATP activation leading to a transient Pi intracellular influx and a subsequent efflux into the extracellular compartment.

Spontaneous ascites filtration and reinfusion (SAFR) in cirrhotic patients

Since knowledge about the pathogenesis of hepato-renal syndrome (HRS) is incomplete, the therapy is empiric and supportive. While a number of specific therapeutic measures have been attempted, none has been proved to be of practical value. We describe a very simple technique for concentration of ascitic fluid obtained with spontaneous filtration by gravity. We have been treating with this new device 4 patients affected by HRS with ascites refractory to diuretics. We obtained a rapid disappearance of ascites and improvement in clinical condition. The simplicity and the ease of operation make this technique feasible for repeated chronic ambulatory treatment.

Spontaneous plasma exchange by gravity

Lysagth et al have reported a semplified model of spontaneous plasmapheresis by placing between an A-V shunt a conventional plasmafilter. On the basis of this experience we tried to make a further semplification of this apparatus using a single venous puncture, obtaining by gravity sufficient transmembrane pressure for plasma separation. By alternatively lowering and elevating the system, plasma is separated from the blood and packed red cells are reinfused after a new pass through the filter with FFP or plasma substitutes.

Restoration of ultrafiltration capacity of peritoneal membrane in patients on CAPD

Among 55 uremic patients who entered our CAPD program, 7 of them showed a reduction or loss of the ultrafiltration capacity (UF) of the peritoneal membrane (PM). They have been treated with high dose of Furosemide (F) to force residual urine output. Four appeared "responders" to drug administration with a significant increase in urine volume, Na excretion and, within a week period gained their dry body weight (BW). In the remaining 3 patients drug therapy resulted ineffective, and fluid removal was obtained by hemofiltration (HF). In both groups we noted an increase in the UF capacity of PM when their dry BW was obtained either by pharmacological or technical approach. These results support the assumption that the over-hydration status of the PM plays a major role in maintaining the UF process.

Muscle biopsy studies in chronically uremic patients: evidence for malnutrition

Evidence for muscle protein wasting and abnormal muscle metabolism is common in uremia. Muscle DNA content is considered a reliable reference standard in normal and undernourished adults. Muscle RNA content rapidly changes during starvation and refeeding. The ratio of noncollagen alkali-soluble proteins (ASP) to DNA is considered to be an estimate of the cytoplasmic volume of a single cell, and the RNA: DNA ratio is an index of the ribosomal capacity for protein synthesis. Muscle DNA, RNA, ASP, water, and fat content were determined in muscle biopsy specimens from chronically uremic patients receiving conservative treatment (CT), maintenance hemodialysis (two centers), or CAPD. Nutrient intake was low and the anthropometric indices were decreased in all groups of patients, except in the hemodialysis patients from one center. Serum proteins and muscle ASP: DNA and RNA: DNA ratios were decreased. The nutritional status was reassessed in some malnourished CAPD patients after about one year of careful nutritional advice and was unchanged. These results suggest that chronically uremic patients on CT are often malnourished, primarily because of an inadequate protein and/or energy intake. Muscle nucleic acid and protein content are useful tools for nutritional assessment at a cellular level in humans with chronic renal failure and can be used to monitor the response to nutritional therapy.

Hemodynamic evaluation during plasma-exchange with intermittent flow

Plasma-exchange (PE) represents an effective therapeutic approach employed in several immunological nephropathies, poisonings and various other diseases. Hemodynamic changes during intermittent flow PE were studied--using the thermodilution technique--in 8 patients (3 male and 5 female) aged between 36 and 73 years (mean 46.4). The mean values for the following parameters were measured before, during every cycle--exchanging about 300 ml of fresh frozen plasma--and at the end of the session: mean arterial pressure (MAP), heart rate (HR), cardiac index (Cl), stroke index (SI), total peripheral resistence (TPR), central venous pressure (CVP), pulmonary arterial pressure (PAP) and pulmonary capillary wedge pressure (PCWP). During the first exchange the systemic circulation showed hemodynamic changes similar that of an acute hemorrhagic condition: decrease in MAP (from 106 to 97 mmHg), Cl (from 4.27 to 3.7 L/m'/m2), SI (from 53 to 49 ml/beat/m2) and CVP (from 6.9 to 4.4 mmHg); increase in TPR (from 1230 to 1339) dynes/sec/cm-5), while HR showed only mild changes. In the following cycles all the parameters progressively returned toward the previous values. During the first cycle the pulmonary circulation showed a decrease in PAP (from 15.5 to 13 mmHg) and PCWP (from 8.9 to 6.6 mmHg). PAP also increased constantly in the following cycles reaching at the end of the session levels which were higher than the initial ones. Our data demonstrate that in PE treatment especially when is employed a low volume of fluid, has to be substituted at every cycle in order to prevent the major hemodynamic complications i.e. hypovolemic shock and heart failure.

Thyroidal status in uremia - effects of hemodialysis and CAPD

Thyroid function was explored in 27 CAPD patients and 25 HD patients. Dialysis was associated with low T3 and T4 levels, increased rT3 concentrations, normal T4 : T3 and reduced T4 : rT3 ratios, normal FT3 and Thyroglobulin concentrations. TSH levels increased during dialysis but still fell within normal limits. The data rule out a condition of primary hypothyroidism and point out to increased thyroidal dismission associated with the block T4-T3 in peripheral cells. Also the increased FT4 levels in CAPD patients could be due to de novo dismission of thyroidal T4.