Hereditary causes of kidney stones and chronic kidney disease

Heavy metal exposure and metabolomics analysis: an emerging frontier in environmental health

Exposure to heavy metals in various populations can lead to extensive damage to different organs, as these metals infiltrate and bioaccumulate in the human body, causing metabolic disruptions in various organs. To comprehensively understand the metal homeostasis, inter-organ "traffic," and extensive metabolic alterations resulting from heavy metal exposure, employing complementary analytical methods is crucial. Metabolomics is pivotal in unraveling the intricacies of disease vulnerability by furnishing thorough understandings of metabolic changes linked to different metabolic diseases. This field offers exciting prospects for enhancing the disease prevention, early detection, and tailoring treatment approaches to individual needs. This article consolidates the existing knowledge on disease-linked metabolic pathways affected by the exposure of diverse heavy metals providing concise overview of the underlying impact mechanisms. The main aim is to investigate the connection between the altered metabolic pathways and long-term complex health conditions induced by heavy metals such as diabetes mellitus, cardiovascular diseases, renal disorders, inflammation, neurodegenerative diseases, reproductive risks, and organ damage. Further exploration of common pathways may unveil the shared targets for treating associated pathological conditions. In this article, the role of metabolomics in disease susceptibility is emphasized that metabolomics is expected to be routinely utilized for the diagnosis and monitoring of diseases and practical value of biomarkers derived from metabolomics, as well as determining their appropriate integration into extensive clinical settings.

Prevention, diagnosis, and treatment of urolithiasis in geriatric patients - differences, similarities and caveats in comparison to the general population

PURPOSE OF REVIEW

Purpose of the review is to address management and prevention of urolithiasis in elderly patients examining the dynamic interplay between general measures, dietary adjustments, lifestyle modifications, and targeted pharmacological and/ or surgical interventions. The goal is to provide understanding of the evolving strategies required for effective urolithiasis prevention in the geriatric population.

RECENT FINDINGS

Age-specific diagnostic considerations are necessary because urolithiasis in the elderly population is characterized by bigger stones, greater peri-operative risks, and heightened symptom severity. When comorbidities are present, conservative treatments - especially analgesia - provide difficulties. Surgical procedures prove to be safe and effective, with complication rates and practical application comparable to younger cohorts. Prevention approaches that include lifestyle changes and the investigation of novel pharmaceutical options such as sodium-dependent glucose co-transporter 2 (SGLT-2)-inhibitors are promising in the management of urolithiasis in the elderly population.

SUMMARY

Our review offers a thorough investigation of urolithiasis in the elderly population, elucidating distinct clinical manifestations, complex diagnostic issues, and treatment implications. The safety and effectiveness of ureteroscopy in older patients, as well as the possible prophylactic function of SGLT-2-I, offer crucial insights for clinicians. Subsequent studies are necessary to enhance age-specific therapies, addressing the distinct obstacles presented by urolithiasis in the elderly population within this rapidly growing demographic.

Monogenic features of urolithiasis: A comprehensive review

Objective

Urolithiasis formation has been attributed to environmental and dietary factors. However, evidence is accumulating that genetic background can contribute to urolithiasis formation. Advancements in the identification of monogenic causes using high-throughput sequencing technologies have shown that urolithiasis has a strong heritable component.

Methods

This review describes monogenic factors implicated in a genetic predisposition to urolithiasis. Peer-reviewed journals were evaluated by a PubMed search until July 2023 to summarize disorders associated with monogenic traits, and discuss clinical implications of identification of patients genetically susceptible to urolithiasis formation.

Results

Given that more than 80% of urolithiases cases are associated with calcium accumulation, studies have focused mainly on monogenetic contributors to hypercalciuric urolithiases, leading to the identification of receptors, channels, and transporters involved in the regulation of calcium renal tubular reabsorption. Nevertheless, available candidate genes and linkage methods have a low resolution for evaluation of the effects of genetic components versus those of environmental, dietary, and hormonal factors, and genotypes remain undetermined in the majority of urolithiasis formers.

Conclusion

The pathophysiology underlying urolithiasis formation is complex and multifactorial, but evidence strongly suggests the existence of numerous monogenic causes of urolithiasis in humans.

Drosophila ClC-c Is a Homolog of Human CLC-5 and a New Model for Dent Disease Type 1

Key Points

Drosophila can be a model for Dent Disease type 1. Drosophila Clc-C mutations function similar to human CLC-5 Dent 1 mutations.

Background

Drosophila serve as exceptional alternative models for in vivo and ex vivo research and may provide an avenue for in-depth investigation for human ClC-5 and Dent disease type 1 (DD1). The Drosophila ClC-c (CG5284) has sequence homology with human ClC-5 and is hypothesized to encompass similar functional and phenotypical roles with ClC-5 and variants that cause DD1.

Methods

Ion transport function and activity of Drosophila ClC-c and homologous DD1 variants were assessed by voltage clamp electrophysiology. Membrane localization was demonstrated in Drosophila expressing a GFP-labeled construct of ClC-c. Genetic expression of an RNAi against ClC-c mRNA was used to generate a knockdown fly that serves as a DD1 disease model. Tubule secretion of cations and protein were assessed, as well as the crystal formation in the Malpighian tubules.

Results

Voltage clamp experiments demonstrate that ClC-c is voltage-gated with Cl−-dependent and pH-sensitive currents. Inclusion of homologous DD1 mutations pathogenic variants (S393L, R494W, and Q777X) impairs ClC-c ion transport activity. In vivo expression of ClC-c-eGFP in Malpighian tubules reveals that the membrane transporter localizes to the apical membrane and nearby cytosolic regions. RNAi knockdown of ClC-c (48% decreased mRNA expression) causes increased secretion of both urinary protein and Ca2+ and increased occurrence of spontaneous tubule crystals.

Conclusions

Drosophila ClC-c shows orthologous function and localization to human ClC-5. Thus, Drosophila and ClC-c regulation may be useful for future investigations of Cl− transport, Ca2+ homeostasis, and urinary protein loss in DD1.

Fifteen-minute consultation: An approach to the child with nephrocalcinosis

Nephrocalcinosis is a common problem faced in both paediatrics and neonates, which may need referral on to paediatric nephrology. This 15 min consultation aims to look at children of different age groups (neonates, children 1-5 years old and older children) looking particularly at history, examination, causes, initial investigations and management.

Novel compound heterozygous pathogenic variants in the SLC3A1 gene in a Chinese family with cystinuria

BACKGROUND

Cystinuria is an autosomal recessive disorder characterized by a cystine transport deficiency in the renal tubules due to mutations in two genes: SLC3A1 and SLC7A9. Cystinuria can be classified into three forms based on the genotype: type A, due to mutations in the SLC3A1 gene; type B, due to mutations in the SLC7A9 gene; and type AB, due to mutations in both genes.

METHODS

We report a 12-year-old boy from central China with cystine stones. He was from a non-consanguineous family that had no known history of genetic disease. A physical examination showed normal development and neurological behaviors. Whole-exome and Sanger sequencing were used to identify and verify the suspected pathogenic variants.

RESULTS

The compound heterozygous variants c.898_905del (p.Arg301AlafsTer6) is located in exon5 and c.1898_1899insAT (p.Asp634LeufsTer46) is located in exon10 of SLC3A1 (NM_000341.4) were deemed responsible for type A cystinuria family. The variant c.898_905del was reported in a Japanese patient in 2000, and the variant c.1898_1899insAT is novel.

CONCLUSION

A novel pathogenic heterozygous variant pair of the SLC3A1 gene was identified in a Chinese boy with type A cystinuria, enriching the mutational spectrum of the SLC3A1 gene. We attempted to find a pattern for the association between the genotype of SLC3A1 variants and the manifestations of cystinuria in patients with different onset ages. Our findings have important implications for genetic counseling and the early clinical diagnosis of cystinuria.

Adenine phosphoribosyl transferase (APRT) deficiency and a novel sequence variant in APRT with phenotypic diversity and a literature review

Adenine phosphoribosyl transferase (APRT) deficiency is an autosomal recessive disorder and a rare cause of urolithiasis due to mutations in APRT (OMIM #102600). APRT deficiency results in increased urinary excretion of 2,8-dihydroxyadenine (DHA) which can cause urolithiasis and kidney failure. However, with prompt diagnosis, patients with APRT deficiency can be treated with xanthine oxidoreductase inhibitors which decrease urinary DHA excretion and improve outcomes. We report a pair of siblings, an 11-year-old brother and his 14-year-old sister with compound heterozygous variants c.270del (p.Lys91Serfs*46) and c.484_486del (p.Leu162del) in APRT with variable clinical presentation of APRT deficiency. The brother presented at 17 months of age with urolithiasis and severe acute kidney injury. His elder sister remained well and asymptomatic with normal kidney function and did not develop renal calculi. Brownish disk or sphere-like crystals with both concentric and radial markings were reported on urine microscopy in the sister on screening. The sister's diagnosis was confirmed with further laboratory evidence of absent red cell lysate APRT activity with corresponding elevated levels of urinary DHA. In conclusion, we identified a novel mutation in the APRT gene in a pair of siblings with greater phenotypic severity in the male.

Safety, Pharmacokinetics, and Exposure-Response Modeling of Nedosiran in Participants With Severe Chronic Kidney Disease

Nedosiran is an investigational RNA-interference therapeutic in development for primary hyperoxaluria (PH). Because nedosiran undergoes renal clearance, we assessed its pharmacokinetic profile in non-PH participants with normal kidney function and Stages 4/5 chronic kidney disease (CKD), the latter with/without dialysis. Nedosiran exposure-response modeling in patients with PH Subtype 1 (PH1) with different renal function level was performed to recommend a nedosiran dose for this subpatient population. In this open-label, single-dose, Phase 1 study, 24 participants with estimated glomerular filtration rate <30 mL/min/1.73 m2 (CKD Stages 4/5; on hemodialysis [Groups 1a, 1b] and not on hemodialysis [Group 2]) and 10 participants with normal kidney function (estimated glomerular filtration rate ≥90 mL/min/1.73 m2 ; Group 3) received a single dose of subcutaneous nedosiran sodium 170 mg. Group 1a received nedosiran 8 hours before beginning hemodialysis, Group 1b received nedosiran 2 hours after completing hemodialysis; Group 2 was not on hemodialysis. Nedosiran population pharmacokinetic-pharmacodynamic analyses were conducted using pooled data from this study and 4 others. Nedosiran pharmacokinetic exposure in non-PH participants with CKD Stages 4/5 was approximately 2-fold higher versus participants with normal kidney function. Hemodialysis timing relative to nedosiran administration had no clinically significant impact on pharmacokinetics (Group 1a vs 1b). Nedosiran was well tolerated. Modeling indicated that in patients with PH1 with CKD Stages 4/5, lower nedosiran doses provide similar exposure and potential reduction in 24-hour urinary oxalate to standard nedosiran doses in patients with PH1 with normal kidney function or CKD Stages 2/3. Nedosiran dosage reductions are recommended in patients with PH1 with CKD Stages 4/5; further adjustments are unnecessary if dialysis is started.

Environmental Conditions as Determinants of Kidney Stone Formation

Urolithiasis is a disease characterized by the presence of stones in the urinary tract, whether in the kidneys, ureters, or bladder. Its origin is multiple, and causes can be cited as hereditary, environmental, dietary, anatomical, metabolic, or infectious factors. A kidney stone is a biomaterial that originates inside the urinary tract, following the principles of crystalline growth, and in most cases, it cannot be eliminated naturally. In this work, 40 calculi from the Don Benito, Badajoz University Hospital are studied and compared with those collected in Madrid to establish differences between both populations with the same pathology and located in very different geographical areas. Analysis by cathodoluminescence offers information on the low crystallinity of the phases and their hydration states, as well as the importance of the bonds with the Ca cation in all of the structures, which, in turn, is related to environmental and social factors of different population groups such as a high intake of proteins, medications, bacterial factors, or possible contamination with greenhouse gases, among other factors.

Polymorphic variations and mRNA expression of the genes encoding interleukins as well as enzymes of oxidative and nitrative stresses as a potential risk of nephrolithiasis development

Urolithiasis is one of the most common urological diseases worldwide with an unclear aetiology. However, a growing body of evidence suggests the potential role of molecular disturbances of the inflammation as well as oxidative and nitrative stresses, in the pathogenesis of urolithiasis. Therefore, we aimed to detect the potential association between six selected single-nucleotide polymorphisms (SNPs) and the development of nephrolithiasis. Moreover, we verified the association of urolithiasis development and mRNA expression of IL-6, IL-8, SOD2, and NOS2 in peripheral blood mononuclear cells (PBMCs). Total genomic DNA and mRNA were isolated from the peripheral blood of 112 patients with urolithiasis and 114 healthy subjects. Using Taq-Man® probes, we genotyped the following SNPs: rs1800797 and rs2069845 in IL-6, rs2227307 in IL-8, rs4880 in SOD2, rs2297518 and rs2779249 in NOS2. In turn, the evaluation of mRNA expression was performed using real-time PCR and 2-ΔCt methods. We found that the C/T genotype of the c.47 T>C-SOD2 SNP increased the frequency of urolithiasis occurrence whereas the T/T homozygote of the same polymorphism decreased the risk of urolithiasis development in the Polish population. Moreover, our study confirmed that patients with urolithiasis were characterised by decreased IL-6, IL-8, and SOD2 mRNA expression levels compared to the controls. In conclusion, our results suggest that polymorphic variants and changes in mRNA expression of IL-6, IL8, SOD2, and NOS2 may be involved in the pathophysiology of urolithiasis.

A Rare Sparkle: A Case of Calcified Kidneys in a Young Infant With Renal Failure

Primary hyperoxaluria-1 (PH1) is an autosomal recessively inherited rare genetic condition due to the deficiency of the hepatic enzyme alanine:glyoxylate aminotransferase which leads to high systemic levels of oxalate and subsequently, early end-stage renal disease and death. Here, we present a case of a three-month-old male infant who presented with loose stools, reduced oral intake, and decreased activity for 12-13 days along with edema and a peeling rash on cheeks, lips, and genitalia. During the entire duration of the inpatient stay, the child was oligoanuric. Kidney ultrasound (USG) was suggestive of bilateral hyperechoic kidneys with increased cortical echogenicity and a computed tomography scan showed bilateral diffusely calcified renal cortices with well-preserved renal architecture. A diagnosis of "oxalate nephropathy" was made from renal biopsy and genetic testing confirmed it to be "primary hyperoxaluria-1". The child was initially managed conservatively, and then peritoneal dialysis was done, following which the child was shifted to intermittent hemodialysis.

Population genetics analysis of SLC3A1 and SLC7A9 revealed the etiology of cystine stone may be more than what our current genetic knowledge can explain

BACKGROUND

Cystine stone is a Mendelian genetic disease caused by SLC3A1 or SLC7A9. In this study, we aimed to estimate the genetic prevalence of cystine stones and compare it with the clinical prevalence to better understand the disease etiology.

METHODS

We analyzed genetic variants in the general population using the 1000 Genomes project and the Human Gene Mutation Database to extract all SLC3A1 and SLC7A9 pathogenic variants. All variants procured from both databases were intersected. Pathogenic allele frequency, carrier rate, and affected rate were calculated and estimated based on Hardy-Weinberg equilibrium.

RESULTS

We found that 9 unique SLC3A1 pathogenic variants were carried by 26 people and 5 unique SLC7A9 pathogenic variants were carried by 12 people, all of whom were heterozygote carriers. No homozygote, compoun d heterozygote, or double heterozygote was identified in the 1000 Genome database. Based on the Hardy-Weinberg equilibrium, the calculated genetic prevalence of cystine stone disease is 1 in 30,585.

CONCLUSION

The clinical prevalence of cystine stone has been previously reported as 1 in 7,000, a notably higher figure than the genetic prevalence of 1 in 30,585 calculated in this study. This suggests that the etiology of cystine stone is more complex than what our current genetic knowledge can explain. Possible factors that may contribute to this difference include novel causal genes, undiscovered pathogenic variants, alternative inheritance models, founder effects, epigenetic modifications, environmental factors, or other modifying factors. Further investigation is needed to fully understand the etiology of cystine stone.

Pediatric Stone Disease: Current Trends and Future Directions

Pediatric nephrolithiasis is less common in children than in adults but the incidence has been rising rapidly, and it is now a public health and economic burden in the United States. There are challenges unique to children that should be taken into consideration when evaluating and managing pediatric stone disease. In this review, we present the current research on risk factors, emerging new technologies for treatment of stones and recent investigations on prevention of stones in this population.

Primary Hyperoxaluria Type 1: Clinical, Paraclinical, and Evolutionary Aspects in Adults from One Nephrology Center

Introduction

Primary hyperoxaluria type 1 (PH1) is a rare and inherited condition of urolithiasis. The aim of our study was to analyze clinical, paraclinical, and evolutionary aspects of PH1 in adult patients in our Nephrology department.

Methods

We conducted a retrospective single-center study between 1990 and 2021. We collected patients followed for PH1 confirmed by genetic study and/or histopathological features of renal biopsy and morphoconstitutional analysis of the calculi.

Results

There were 25 patients with a gender ratio of 1.78. The median age at onset of symptoms was 18 years. A delay in diagnosis more than 10 years was noted in 13 cases. The genetic study found the I244T mutation in 17 cases and 33-34 InsC in 4 cases. A kidney biopsy was performed in 5 cases, on a native kidney in 4 cases and on a graft biopsy in one case. The analysis of calculi was done in 10 cases showing type Ic in 2 cases. After a median follow-up of 13 years (1 year-42 years), 14 patients progressed to end-stage chronic renal failure (ESRD). The univariate study demonstrated a remarkable association with progression to ESRD in our population (44% vs. 56%) RR = 13.32 (adjusted ORs (95% CI): 2.82-62.79) (p < 0.01).

Conclusion

Progression to ESRD was frequent in our series. Early diagnosis and adequate management can delay such an evolution.

Tubular Diseases and Stones Seen From Pediatric and Adult Nephrology Perspectives

The tubular system of the kidneys is a complex series of morphologic and functional units orchestrating the content of tubular fluid as it flows along the nephron and collecting ducts. Renal tubules maintain body water, regulate electrolytes and acid-base balance, reabsorb precious organic solutes, and eliminate specific metabolites, toxins, and drugs. In addition, decisive mechanisms to adjust blood pressure are governed by the renal tubules. Genetic as well as acquired disorders of these tubular functions may cause serious diseases that manifest both in childhood and adulthood. This article addresses a selection of tubulopathies and the underlying pathomechanisms, while highlighting the important differences in pediatric and adult nephrology care. These range from rare monogenic conditions such as nephrogenic diabetes insipidus, cystinosis, and Bartter syndrome that present in childhood, to the genetic and acquired tubular pathologies causing hypertension or nephrolithiasis that are more prevalent in adults. Both pediatric and adult nephrologists must be aware of these conditions and the age-dependent manifestations that warrant close interaction between the two subspecialties.

Pediatric urolithiasis: what can pediatricians expect from radiologists?

The incidence of urolithiasis in children has increased over the two last decades. Urolithiasis formation results from urine oversaturation following insufficient water intake, urinary obstruction (notably in cases of congenital uropathies), excess production of an insoluble compound, or imbalance between crystallization promoters and inhibitors. Whereas most urolithiases in adults occur secondary to environmental factors, in children, secondary causes are far more frequent, and 15% are related to genetic causes, most often monogenic. This is especially true in recurrent forms, with early and rapid progression and bilateral stones, and in cases of familial history or consanguinity. Because of differing clinical management, one should rule out cystinuria, primary hyperoxaluria and renal tubular acidosis, among other causes of urolithiasis. As such, a complete biochemical evaluation must be performed in all cases of pediatric urolithiasis, even in cases of an underlying uropathy. Ultrasound examination is the first-line modality for imaging pediatric urolithiasis, allowing both diagnosis (urolithiasis and its complications) and follow-up. US examination should also explore clues to an underlying cause of urolithiasis. This review is focused on the role of imaging in the management and etiological assessment of pediatric urolithiasis. Radiologists play an important role in pediatric urolithiasis, facilitating diagnosis, follow-up and surgical management. A trio of clinicians (pediatric nephrologist, pediatric surgeon, pediatric radiologist) is thus necessary in the care of these pediatric patients.

A Summary of Current Guidelines and Future Directions for Medical Management and Monitoring of Patients with Cystinuria

Cystinuria is the most common genetic cause of recurrent kidney stones. As the result of a genetic defect in proximal tubular reabsorption of filtered cystine, increased urine levels of the poorly soluble amino acid result in recurrent cystine nephrolithiasis. Recurrent cystine stones not only adversely affect the quality of patients suffering from cystinuria but also may result in chronic kidney disease (CKD) from recurrent renal injury. Thus, the mainstay of medical management revolves around prevention of stones. Recently published consensus statements on guidelines for managing cystinuria were released from both the United States and Europe. The purpose of this review is to summarize guidelines for medical management of patients with cystinuria, to provide new insight into the utility and clinical significance of cystine capacity-an assay for monitoring cystinuria, and to discuss future directions for research on treatment of cystinuria. We discuss future directions, including the potential use of cystine mimetics, gene therapy, V2-receptor blockers, and SGLT2 inhibitors, topics which have not appeared in more recent reviews. It is notable that in the absence of randomized, controlled trials, the recommendations cited here and in the guidelines are based on our best understanding of the disorder's pathophysiology, observational studies, and clinical experience.

Pediatric Nephrolithiasis

The prevalence of pediatric nephrolithiasis has increased dramatically in the past two decades for reasons that have yet to be fully elucidated. Workup of pediatric kidney stones should include metabolic assessment to identify and address any risk factors predisposing patients to recurrent stone formation, and treatment should aim to facilitate stone clearance while minimizing complications, radiation and anesthetic exposure, and other risks. Treatment methods include observation and supportive therapy, medical expulsive therapy, and surgical intervention, with choice of treatment method determined by clinicians' assessments of stone size, location, anatomic factors, comorbidities, other risk factors, and preferences and goals of patients and their families. Much of the current research into nephrolithiasis is restricted to adult populations, and more data are needed to better understand many aspects of the epidemiology and treatment of pediatric kidney stones.

Epidemiology of Kidney Stones

In the past two decades, major breakthroughs that improve our understanding of the pathophysiology and therapy of kidney stones (KS) have been lacking. The disease continues to be challenging for patients, physicians, and healthcare systems alike. In this context, epidemiological studies are striving to elucidate the worldwide changes in the patterns and the burden of the disease and identify modifiable risk factors that contribute to the development of kidney stones. Our expanding knowledge of the epidemiology of kidney stones is of paramount importance and largely upgrades the modern management of the disease. In this paper, we review the variables affecting prevalence and incidence, including age, gender, race, ethnicity, occupation, climate, geography, systemic diseases, diabetes, vascular disease, chronic kidney disease, and dietary risk factors relevant to kidney stones.

Urinary stone disease in Syrian children

BACKGROUND

Pediatric urinary stone disease (USD) is a costly medical problem. This study aims to assess the clinical characteristics and outcomes of common and rare causes of pediatric USD.

METHODS

A retrospective descriptive cohort study included all children < 13 years of age with confirmed USD admitted to the Children's University Hospital in Damascus, Syria, from January 2013 to December 2019. The study sample was divided into two groups based on etiologies: common and rare causes groups.

RESULTS

We evaluated 235 patients; 147 of them were males, and the male-to-female ratio was 1.7:1. The common causes group consisted of 203 patients (mean age 3.52 ± 3.66 years) and mainly included metabolic disorders (45.5%) and anatomical abnormalities (22.3%), while the rare causes group included 32 cases (mean age 4.93 ± 4.08 years), 12 patients with uric acid stones (37.5%), 7 patients with cystinuria (21.9%), and primary hyperoxaluria in 5 patients (15.6%). In addition, 39.6% of study patients were born to consanguineous marriages. Sixty-two patients developed AKI, and eleven patients had chronic kidney disease (CKD). Patients with rare causes were more likely to have AKI, CKD, bilateral stones, and recurrent stones (P-value < 0.05). Stone analysis was performed on 83 patients, and the main stone types were calcium oxalate (34.9%), uric acid (14.4%), and struvite stones (12%). Surgery was the most performed treatment in 101 patients (56.7%).

CONCLUSION

Patients with rare causes of pediatric USD are at a higher risk for severe complications and require early diagnosis and management. The high rate of uric acid stones in our society requires further evaluation for possible underlying causes. A higher resolution version of the Graphical abstract is available as Supplementary information.

A Study on the CLCN5 Gene in Iranian Patients: A Report of Novel and Recurrent Mutations

INTRODUCTION

Dent's disease is an X-linked inherited renal tubular disorder characterized by proteinuria, hypercalciuria, nephrocalcinosis, nephrolithiasis, rickets, and end-stage renal disease. Almost 60% of patients have causative mutations in the CLCN5 gene (Dent 1), and 15% of affected individuals have mutations in the OCRL1 gene (Dent 2). The aims of this study are to identify CLCN5 mutations in Iranian families with Dent's disease and to characterize the associated clinical syndromes.

METHODS

We studied 14 patients from 13 unrelated Iranian families with a clinical diagnosis of Dent's disease. Proteinuria was detected in all patients. Nephrolithiasis was found in 5 patient, and hematuria in 2 patients. Most of the affected individuals had nephrocalcinosis. PCR-sequencing for the CLCN5 gene was performed in all 14 patients. Next-generation sequencing (NGS) has also been performed in one patient who we did not find causative mutation.

RESULTS

We identified four different CLCN5 mutations including one missense mutation (c.731C>T), one nonsense mutation (c.100C>T), and two novel mutations, consisting of one frameshift mutation (c.1241_1242dupAA) and one splicing mutation (c.805-2A>G). We also identified one OCRL1 mutation, one splicing mutation (c.1466 + 1G>A), using NGS.

CONCLUSION

This is the first report to characterize mutations in the CLCN5 gene in Iranian patients with Dent's disease and expands the spectrum of CLCN5 mutations by reporting two novel mutations, c.1241_1242dupAA and c.805-2A>G.

Emerging Perspectives on the Rare Tubulopathy Dent Disease: Is Glomerular Damage a Direct Consequence of ClC-5 Dysfunction?

Dent disease (DD1) is a rare tubulopathy caused by mutations in the CLCN5 gene. Glomerulosclerosis was recently reported in DD1 patients and ClC-5 protein was shown to be expressed in human podocytes. Nephrin and actin cytoskeleton play a key role for podocyte functions and podocyte endocytosis seems to be crucial for slit diaphragm regulation. The aim of this study was to analyze whether ClC-5 loss in podocytes might be a direct consequence of the glomerular damage in DD1 patients. Three DD1 kidney biopsies presenting focal global glomerulosclerosis and four control biopsies were analyzed by immunofluorescence (IF) for nephrin and podocalyxin, and by immunohistochemistry (IHC) for ClC-5. ClC-5 resulted as down-regulated in DD1 vs. control (CTRL) biopsies in both tubular and glomerular compartments (p < 0.01). A significant down-regulation of nephrin (p < 0.01) in DD1 vs. CTRL was demonstrated. CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/Caspase9) gene editing of CLCN5 in conditionally immortalized human podocytes was used to obtain clones with the stop codon mutation p.(R34Efs*14). We showed that ClC-5 and nephrin expression, analyzed by quantitative Reverse Transcription/Polymerase Chain Reaction (qRT/PCR) and In-Cell Western (ICW), was significantly downregulated in mutant clones compared to the wild type ones. In addition, F-actin staining with fluorescent phalloidin revealed actin derangements. Our results indicate that ClC-5 loss might alter podocyte function either through cytoskeleton disorganization or through impairment of nephrin recycling.

PHYOX2: a pivotal randomized study of nedosiran in primary hyperoxaluria type 1 or 2

Nedosiran is an investigational RNA interference agent designed to inhibit expression of hepatic lactate dehydrogenase, the enzyme thought responsible for the terminal step of oxalate synthesis. Oxalate overproduction is the hallmark of all genetic subtypes of primary hyperoxaluria (PH). In this double-blind, placebo-controlled study, we randomly assigned (2:1) 35 participants with PH1 (n = 29) or PH2 (n = 6) with eGFR ≥30 mL/min/1.73 m² to subcutaneous nedosiran or placebo once monthly for 6 months. The area under the curve (AUC) of percent reduction from baseline in 24-hour urinary oxalate (Uox) excretion (primary endpoint), between day 90-180, was significantly greater with nedosiran vs placebo (least squares mean [SE], +3507 [788] vs -1664 [1190], respectively; difference, 5172; 95% CI 2929-7414; P < 0.001). A greater proportion of participants receiving nedosiran vs placebo achieved normal or near-normal (<0.60 mmol/24 hours; <1.3 × ULN) Uox excretion on ≥2 consecutive visits starting at day 90 (50% vs 0; P = 0.002); this effect was mirrored in the nedosiran-treated PH1 subgroup (64.7% vs 0; P < 0.001). The PH1 subgroup maintained a sustained Uox reduction while on nedosiran, whereas no consistent effect was seen in the PH2 subgroup. Nedosiran-treated participants with PH1 also showed a significant reduction in plasma oxalate versus placebo (P = 0.017). Nedosiran was generally safe and well tolerated. In the nedosiran arm, the incidence of injection-site reactions was 9% (all mild and self-limiting). In conclusion, participants with PH1 receiving nedosiran had clinically meaningful reductions in Uox, the mediator of kidney damage in PH.

A case of 2,8-DHA crystalline nephropathy caused by adenine phosphoribosyltransferase deficiency: diagnosis and treatment

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive disorder that leads to the accumulation of poorly soluble 2,8-dihydroxyadenine (DHA) in the kidneys, resulting in a variety of renal presentations including nephrolithiasis, acute kidney injury, and chronic kidney disease (CKD) caused by crystal nephropathy. Here, we report a case of a 43-year-old man with 2,8-DHA crystalline nephropathy caused by APRT deficiency strongly suspected by renal biopsy results and definitively diagnosed by a urine gas chromatography-mass spectrometry (GC/MS)-based plasma metabolomic assessment. This case represents the importance of awareness and recognition of the signs and symptoms of this rare condition and its progression to CKD, which can be prevented by the early administration of xanthine oxidoreductase inhibitors.

Dent Disease Type 1: Still an Under-Recognized Renal Proximal Tubulopathy: A Case Report

Dent disease is a rare renal tubular disorder that appears almost exclusively in males. The diagnosis is still challenging, and therefore Dent disease is occasionally misdiagnosed. We report a case of a 45-year-old man with Dent disease who developed renal failure. Since the age of 7 months, he persistently exhibited proteinuria. At the age of 24 years, he underwent kidney biopsy, which revealed focal segmental glomerulosclerosis. The patient’s brother was found to have proteinuria since he was 2 years old. At the age of 45 years, the patient was transferred to a tertiary care nephrologist, and Dent disease was suspected. Genetic testing revealed a CLCN5 mutation. We highlight the broad spectrum of clinical manifestations in Dent disease and the importance of having a high clinical suspicion to attain a definitive diagnosis. Furthermore, future research regarding the clinical course of the disease, prognosis, and effective treatment options is needed.

Shockwaves and the Rolling Stones: An Overview of Pediatric Stone Disease

Urinary stone disease is a common problem in adults, with an estimated 10% to 20% lifetime risk of developing a stone and an annual incidence of almost 1%. In contrast, in children, even though the incidence appears to be increasing, urinary tract stones are a rare problem, with an estimated incidence of approximately 5 to 36 per 100,000 children. Consequently, typical complications of rare diseases, such as delayed diagnosis, lack of awareness, and specialist knowledge, as well as difficulties accessing specific treatments also affect children with stone disease. Indeed, because stone disease is such a common problem in adults, frequently, it is adult practitioners who will first be asked to manage affected children. Yet, there are unique aspects to pediatric urolithiasis such that treatment practices common in adults cannot necessarily be transferred to children. Here, we review the epidemiology, etiology, presentation, investigation, and management of pediatric stone disease; we highlight those aspects that separate its management from that in adults and make a case for a specialized, multidisciplinary approach to pediatric stone disease.

HOGA1 gene pathogenic variants in primary hyperoxaluria type III: Spectrum of pathogenic sequence variants, and phenotypic association

Primary hyperoxalurias (PH) are a group of rare heterogeneous disorders characterized by deficiencies in glyoxylate metabolism. To date, three genes have been identified to cause three types of PH (I, II, and III). The HOGA1 gene caused type III in around 10% of the PH cases. Disease-associated pathogenic variants have been reported from several populations and a comprehensive spectrum of these mutations and genotype-phenotype correlation has never been presented. In this study, we describe new cases of the HOGA1 gene pathogenic variants identified in our population. We report the first case of ESKD with successful kidney transplantation with 5 years of follow-up. Furthermore, a comprehensive overview of PH type III associated HOGA1 gene variants was carried out. Compiling the data from the literature, we reviewed 57 distinct HOGA1 gene pathogenic variants in 175 patients worldwide. The majority of reported variants are missense variants that predicted a loss of function mechanism as the underlying pathology. There has been evidence of the presence of founder mutations in several populations like Europeans, Ashkenazi Jews, Arab, and Chinese populations. No significant genotype-phenotype correlation was identified concerning the ages of onset of the disease and biochemical and metabolic parameters. Nephrocalcinosis was rare in patients with disease-associated variants. Most of the patients were presented with urolithiasis early in life; only five cases reported disease progression after the second decade of life. The establishment of impairment of renal function in 8% of all the reported cases makes this type a relatively severe form of primary hyperoxaluria, not a benign etiology as suggested previously.

Etiology, urine metabolic risk factors, and urine oxalate patterns in patients with significant hyperoxaluria and recurrent nephrolithiasis

PURPOSE

American Urology Association guidelines recommend genetic testing for patients with recurrent stones and urine oxalate > 75 mg/day. The goal of this study was to examine the treatment of patients in this category in a large multidisciplinary adult stone clinic.

METHODS

Patients were evaluated from a single institution between 2006 and 2019. Those with at least one level of urinary oxalate excretion (uOx) above 75 mg/day were identified. A chart review identified enteric risk factors and genetic testing results. Patients without an identifiable enteric cause were considered idiopathic.

RESULTS

A total of 4229 separate 24-h urine collections in 1302 patients were reviewed. At least one measurement of uOx above 75 mg/day was found in 103 (7.9%) patients. Enteric hyperoxaluria (EH) was seen in 28 (27%) and idiopathic hyperoxaluria (IH) in 76 (74%). 20 (71%) patients in the EH group had undergone gastric bypass. The median uOx was significantly higher level in the EH group (121.0 vs. 93.0 mg/day). For the entire cohort, there was a drop in uOx (- 33.8 mg/day) with medical and dietary therapy after a follow-up of 46.6 months. The final oxalate was higher in EH (88.9 vs. 60.1 mg/day). Only one patient had referral for genetic testing and was found to have primary hyperoxaluria type 2.

CONCLUSIONS

The most common cause of significant hyperoxaluria in patients with recurrent nephrolithiasis remains idiopathic. Patients with IH have more significant improvement in uOx compared to EH; however, both groups had hyperoxaluria at last follow-up. Rate of genetic testing is low despite guideline recommendations.

Cystinuria: an update on pathophysiology, genetics, and clinical management

Cystinuria is the most common genetic cause of nephrolithiasis in children. It is considered a heritable aminoaciduria as the genetic defect affects the reabsorption of cystine and three other amino acids (ornithine, lysine, and arginine) in the renal proximal tubule. Patients affected by this condition have elevated excretion of cystine in the urine, and because of this amino acid's low solubility at normal urine pH, patients tend to form cystine calculi. To date, two genes have been identified as disease-causative: SLC3A1 and SLC7A9, encoding for the two subunits of the heterodimeric transporter. The clinical features of this condition are solely related to nephrolithiasis. The diagnosis is usually made during infancy or adolescence, but cases of late diagnosis are common. The goal of therapy is to reduce excretion and increase the solubility of cystine, through both modifications of dietary habits and pharmacological treatment. However, therapeutic interventions are not always sufficient, and patients often have to undergo several surgical procedures during their lives to treat recurrent nephrolithiasis. The goal of this literature review is to synthesize the available evidence on diagnosis and management of patients affected by cystinuria in order to provide physicians with a practical tool that can be used in daily clinical practice. This review also aims to shed some light on new therapy directions with the aim of ameliorating kidney outcomes while improving adherence to treatment and quality of life of cystinuric patients.

Lipidomics characterization of the lipid metabolism profiles in a cystinuria rat model: Precalculus damage in the kidney of cystinuria

Cystinuria is a genetic disorder of cystine transport, including defective protein b^0,+AT (encoded by SLC7A9), and/or rBAT (encoded by SLC3A1). Patients present hyperexcretion of cystine in the urine, recurrent cystine lithiasis, and progressive decline in kidney function. Moreover, heterodimer transport is defective. To date, little omics data are accessible regarding this metabolic disease caused by membrane proteins. Since membrane function is closely related to changes in the lipidome, we decided to explore the changes in kidney tissue of a self-established cystinuria rat model by performing lipidomic analysis by LC-MS/MS. Our results demonstrated that Slc7a9 deficiency changed the lipid profile of the renal cortex and induced vital modifications in the lipidome, including major alterations in ChE, LPA, and PA. Among those alterations, this lipidomic study highlights the lipid changes that participate in inflammatory responses during cystinuria. As a result, lipid research, perhaps has great potential, for it may lead to the identification of novel therapeutic targets for the prevention and treatment of cystinuria.

Oxalobacter formigenes: A new hope as a live biotherapeutic agent in the management of calcium oxalate renal stones

Recent advances in understanding the association of gut microbiota with the host have shown evidence of certain bacterial therapeutic potentiality in preventing and treating metabolic diseases. Hyperoxaluria is a severe challenge in nephrology and has led to the novel gut eubiosis as current therapy. The human gut commensal, obligate anaerobic, and intestinal oxalate-degrading strains of Oxalobacter formigenes have drawn a promising significant interest for the next-generation probiotics (NGPs). This nonpathogenic, potential probiotic, and specialist oxalotrophic properties of O. formigenes give a new hope as a live biotherapeutic agent for calcium oxalate renal therapy. Numerous satisfactory outcomes of in vitro and in vivo studies were achieved on evaluating O. formigenes functionality, but the commercial production of this bacterium is yet to be achieved. This bacterium finds diverse application in dietary and endogenous oxalate degradation and the improvement of gut health, on which we concentrated our attention in this review. The relationship between good anaerobic gut bacterial dysbiosis and renal complications is comprehensively discussed to address the need for the development probiotic formulation. However, the commercial production of this bacteria on a broad scale is complex, with numerous obstacles, mainly because they are oxygen-sensitive and difficult to culture. This review will coherently present the current and available methodologies in producing, stabilizing, and delivering these NGPs to treat calcium stones. Moreover, the study presents the extensive work and key milestones achieved in the research on O. formigenes from tale to the truth.

The causes and consequences of paediatric kidney disease on adult nephrology care

Adult nephrologists often look after patients who have been diagnosed with kidney disease in childhood. This does present unique challenges to the adult nephrologist, who may be unfamiliar with the underlying cause of kidney disease as well as the complications of chronic kidney disease (CKD) that may have accumulated during childhood. This review discusses common causes of childhood CKD, in particular congenital anomalies of the kidney and urinary tract (CAKUT), autosomal dominant tubulointerstitial kidney disease (ADTKD), polycystic kidney disease, hereditary stone disease, nephrotic syndrome and atypical haemolytic uraemic syndrome. The long-term consequences of childhood CKD, such as the cardiovascular consequences, cognition and education as well as bone health, nutrition and growth are also discussed.

Monogenic urinary lithiasis in Tunisian children: 25 years' experience of a referral center

OBJECTIVE

To describe the clinical, biochemical and evolutive profile of monogenic urinary lithiasis in Tunisian children followed up in a reference service, during a 25 years period.

METHODS

This was a single-center retrospective observational study of children with urolithiasis, conducted in the pediatric nephrology department in Charles Nicolle Hospital, Tunis, Tunisia over 25 years (January 1st, 1996 to December 31, 2020). Children≤18 of age with urolithiasis with or without nephrocalcinosis related to a monogenic disease were included in our study.

RESULTS

A total of 66 children were included in our study. Patients were 5.92±3.48 years of age at the time of urolithiasis diagnosis, and 5.33±3.66 years of age at the time of the underlying pathology diagnosis. The inherited urolithiasis disorders found in our series were: primary hyperoxaluria in 44 cases, cystinuria in 9 cases, Lesch Nyhan syndrome in 5 cases. Renal tubular acidosis was found in 3 cases, and hereditary xanthinuria in 2 cases. Bartter syndrome, adenine phosphoribosyltransferase deficiency and Hereditary hypophosphatemic rickets with hypercalciuria were found in 1 case each. After an average follow-up of 6.45±3.79 years, six patients were in end-stage renal disease. Three patients had died, all of them being followed for primary hyperoxaluria type 1.

CONCLUSIONS

Monogenic urinary lithiasis, although rare, are most likely under-diagnosed in countries with high consanguinity such as Tunisia. The screening of these diseases seems to be of primary importance because of their significant morbidity.

Social Determinants of Kidney Stone Disease: The Impact of Race, Income and Access on Urolithiasis Treatment and Outcomes

The medical and surgical management of kidney stones is one of the most common functions of the urologist. Management choices are often nuanced, involving the decision to embark on one surgical plan among several options. As the wider medical community critically evaluates the care we provide to an increasingly diverse population, it will be important to examine patient outcomes with a particular focus on ensuring equitable care. This review examines the influence of social parameters on the care of kidney stone patients. The dearth of literature in this area warrants rigorous studies on the relationship between race as well as socioeconomic status and the management of kidney stone disease.

Differences in renal cortex transcriptional profiling of wild-type and novel type B cystinuria model rats

Cystinuria is a genetic disorder of cystine transport that accounts for 1–2% of all cases of renal lithiasis. It is characterized by hyperexcretion of cystine in urine and recurrent cystine lithiasis. Defective transport of cystine into epithelial cells of renal tubules occurs because of mutations of the transport heterodimer, including protein b^0,+AT (encoded by SLC7A9) and rBAT (encoded by SLC3A1) linked through a covalent disulfide bond. Study generated a novel type B cystinuria rat model by artificially deleting 7 bp of Slc7a9 gene exon 3 using the CRISPR-Cas9 system, and those Slc7a9-deficient rats were proved to be similar with cystinuria in terms of genome, transcriptome, translation, and biologic phenotypes with no off-target editing. Subsequent comparisons of renal histopathology indicated model rats gained typical secondary changes as medullary fibrosis with no stone formation. A total of 689 DEGs (383 upregulated and 306 downregulated) were differentially expressed in the renal cortex of cystinuria rats. In accordance with the functional annotation of DEGs, the potential role of glutathione metabolism processes in the kidney of cystinuria rat model was proposed, and KEGG analysis results showed that knock-out of Slc7a9 gene triggered more biological changes which has not been studied. In short, for the first time, a rat model and its transcriptional database that mimics the pathogenesis and clinical consequences of human type B cystinuria were generated.

Dent Disease Type 1: A Diagnostic Dilemma and Review

This case report describes a boy with a rare genetic disease that primarily affects the kidneys and has implications on growth and development. Dent disease type 1 is an X-linked tubulopathy mainly caused by inactivating mutations in the chloride voltage-gated channel 5 (CLCN5) gene. It is a rare but important diagnosis for children with variable phenotypic presentations that can include low molecular weight proteinuria (LMWP), nephrocalcinosis, bony deformities and possible progression to early-onset renal failure. A delay in diagnosis is often encountered when it comes to Dent disease. This is due to the similarities in presentation of the disease to other commonly seen pediatric conditions (such as minimal change nephrotic syndrome, nutritional rickets, renal tubular acidosis [RTA], etc.) and also since it can present with variable phenotypes and has a great amount of allelic heterogeneity. In this case, it was diagnosed after 13 years from symptom onset. The patient was subjected to alternative forms of medicine, multiple working diagnoses and associated treatments at various hospitals which most likely contributed to a faster disease progression. In addition to the treatment of the disease, growth hormone (GH) therapy has proven to be beneficial but was not offered to this patient. In this case, we would also like to report some rare findings such as persistent hypercholesterolemia and steroid-resistant nephrotic syndrome (SRNS) biopsy pattern. We decided to pursue this particular disease to highlight the importance of having a high clinical suspicion with a view to attain a definitive diagnosis and instituting appropriate treatment as soon as possible. We also highlight the importance of keeping the patient informed about their disease, the possible therapeutic options and the importance of genetic counselling and patient education.

The genetics of kidney stone disease and nephrocalcinosis

Kidney stones (also known as urinary stones or nephrolithiasis) are highly prevalent, affecting approximately 10% of adults worldwide, and the incidence of stone disease is increasing. Kidney stone formation results from an imbalance of inhibitors and promoters of crystallization, and calcium-containing calculi account for over 80% of stones. In most patients, the underlying aetiology is thought to be multifactorial, with environmental, dietary, hormonal and genetic components. The advent of high-throughput sequencing techniques has enabled a monogenic cause of kidney stones to be identified in up to 30% of children and 10% of adults who form stones, with ~35 different genes implicated. In addition, genome-wide association studies have implicated a series of genes involved in renal tubular handling of lithogenic substrates and of inhibitors of crystallization in stone disease in the general population. Such findings will likely lead to the identification of additional treatment targets involving underlying enzymatic or protein defects, including but not limited to those that alter urinary biochemistry.

Molecular Diagnosis of Primary Hyperoxaluria Type 1 and Distal Renal Tubular Acidosis in Moroccan Patients With Nephrolithiasis and/or Nephrocalcinosis

Nephrolithiasis (NL) and urolithiasis (UL) are usual reasons for hospitalization and presentation in pediatric outpatient departments and their incidence continues to rise worldwide. In Morocco, a previous epidemiological study done in the Fez region between January 2003 and November 2013 reported a prevalence of 0.83% of childhood UL. In two studies, heritability accounted for almost half of all NL or nephrocalcinosis (NC) prevalence. Genetic factors must be considered in the etiological diagnosis of urinary lithiasis in Morocco since the frequency of consanguineous marriages is high. Hereditary tubular disorders, especially distal renal tubular acidosis (dRTA) and Dent disease, and metabolic disorders like idiopathic hypercalciuria and hyperoxaluria are the most common causes of medullary NC. Primary hyperoxaluria type 1 (PH1), which can generate an early onset of NC, and often chronic kidney disease (CKD) should always be considered and thoroughly diagnosed. The aim of this work was to establish a molecular diagnosis of PH1 and dRTA and, thus, to predict and explain the disease phenotype in a cohort of 44 Moroccan patients with NL and/or NC by analyzing the AGXT and ATP6V1B1 genes that cause NL and/or NC when mutated. Disease phenotype was molecularly explained and solved in six of 44 individuals with NL and/or NC (13.6%). In the pediatric subgroup of individuals, a causative mutation in 16.2% was identified, whereas in the adult cohort no pathogenic mutation was detected. In our patients, PH1 was objectified in 67% of cases followed by dRTA in 33% of cases. We suggest that prompt detection and prophylactic treatment of UL are necessary to limit the risk of everlasting renal damage and thus prevent or delay the progression to CKD.

Gene therapy for kidney disease: targeting cystinuria

PURPOSE OF REVIEW

The aim of this study was to summarize recent findings in kidney gene therapy while proposing cystinuria as a model kidney disease target for genome engineering therapeutics.

RECENT FINDINGS

Despite the advances of gene therapy for treating diseases of other organs, the kidney lags behind. Kidney-targeted gene delivery remains an obstacle to gene therapy of kidney disease. Nanoparticle and adeno-associated viral vector technologies offer emerging hope for kidney gene therapy. Cystinuria represents a model potential target for kidney gene therapy due to its known genetic and molecular basis, targetability, and capacity for phenotypic rescue.

SUMMARY

Although gene therapy for kidney disease remains a major challenge, new and evolving technologies may actualize treatment for cystinuria and other kidney diseases.

Disrupting Crystal Growth through Molecular Recognition: Designer Therapies for Kidney Stone Prevention

Aberrant crystallization within the human body can lead to several disease states or adverse outcomes, yet much remains to be understood about the critical stages leading to these events, which can include crystal nucleation and growth, crystal aggregation, and the adhesion of crystals to cells. Kidney stones, which are aggregates of single crystals with physiological origins, are particularly illustrative of pathological crystallization, with 10% of the U.S. population experiencing at least one stone occurrence in their lifetimes. The human record of kidney stones is more than 2000 years old, as noted by Hippocrates in his renowned oath and much later by Robert Hooke in his treatise Micrographia. William Hyde Wollaston, who was a physician, chemist, physicist, and crystallographer, was fascinated with stones, leading him to discover an unusual stone that he described in 1810 as cystic oxide, later corrected to cystine. Despite this long history, however, a fundamental understanding of the stages of stone formation and the rational design of therapies for stone prevention have remained elusive.This Account reviews discoveries and advances from our laboratories that have unraveled the complex crystal growth mechanisms of l-cystine, which forms l-cystine kidney stones in at least 20 000 individuals in the U.S. alone. Although l-cystine stones affect fewer individuals than common calcium oxalate stones, they are usually larger, recur more frequently, and are more likely to cause chronic kidney disease. Real-time in situ atomic force microscopy (AFM) reveals that the crystal growth of hexagonal l-cystine is characterized by a complex mechanism in which six interlaced anisotropic spirals grow synchronously, emanating from a single screw dislocation to generate a micromorphology with the appearance of stacked hexagonal islands. In contrast, proximal heterochiral dislocations produce features that appear to be spirals but actually are closed loops, akin to a Frank-Read source. These unusual and aesthetic growth patterns can be explained by the coincidence of the dislocation Burgers vector and the crystallographic 6₁ screw axis. Inhibiting l-cystine crystal growth is key to preventing stone formation. Decades of studies of "tailor-made additives", which are imposter molecules that closely resemble the solute and bind to crystal faces through molecular recognition, have demonstrated their effects on crystal properties such as morphology and polymorphism. The ability to visualize crystal growth in real time by AFM enables quantitative measurements of step velocities and, by extension, the effect of prospective inhibitors on growth rates, which can then be used to deduce inhibition mechanisms. Investigations with a wide range of prospective inhibitors revealed the importance of precise molecular recognition for binding l-cystine imposters to crystal sites, which results in step pinning and the inhibition of step advancement as well as the growth of bulk crystals. Moreover, select inhibitors of crystal growth, measured in vitro, reduce or eliminate stone formation in knockout mouse models of cystinuria, promising a new pathway to l-cystine stone prevention. These observations have wide-ranging implications for the design of therapies based on tailor-made additives for diseases associated with aberrant crystallization, from disease-related stones to "xenostones" that form in vivo because of the crystallization of low-solubility therapeutic agents such as antiretroviral agents.

The Potential of CRISPR/Cas9 Gene Editing as a Treatment Strategy for Inherited Diseases

Clustered regularly interspaced short palindromic repeats (CRISPR) is a promising innovative technology for genomic editing that offers scientists the chance to edit DNA structures and change gene function. It has several possible uses consisting of editing inherited deficiencies, treating, and reducing the spread of disorders. Recently, reports have demonstrated the creation of synthetic RNA molecules and supplying them alongside Cas9 into genome of eukaryotes, since distinct specific regions of the genome can be manipulated and targeted. The therapeutic potential of CRISPR/Cas9 technology is great, especially in gene therapy, in which a patient-specific mutation is genetically edited, or in the treating of human disorders that are untreatable with traditional treatments. This review focused on numerous, in vivo, in vitro, and ex vivo uses of the CRISPR/Cas9 technology in human inherited diseases, discovering the capability of this versatile in medicine and examining some of the main limitations for its upcoming use in patients. In addition to introducing a brief impression of the biology of the CRISPR/Cas9 scheme and its mechanisms, we presented the utmost recent progress in the uses of CRISPR/Cas9 technology in editing and treating of human genetic diseases.

The Crystalline Nephropathies

Crystalline nephropathies are a unique form of kidney disease characterized by the histologic finding of intrarenal crystal deposition. The intrinsic nature of some molecules and ions combined with a favorable tubular fluid physiology leads to crystal precipitation and deposition within the tubular lumens. Crystal deposition promotes kidney injury through tubular obstruction and both direct and indirect cytotoxicities. Further kidney injury develops from inflammation triggered by these crystals. From a clinical standpoint, the crystalline nephropathies are associated with abnormal urinalysis and urinary sediment findings, tubulopathies, acute kidney injury (AKI), and/or chronic kidney disease (CKD). Urine sediment examination is often helpful in alerting clinicians to the possibility of crystal-related kidney injury. The identification of crystals within the kidneys on biopsy by pathologists prompts clinicians to evaluate patients for medication-related kidney injury, dysproteinemia-related malignancies, and certain inherited disorders. This review will focus on the clinical and pathologic aspects of these 3 categories of crystalline nephropathies.

Comprehensive Genetic Analysis Reveals Complexity of Monogenic Urinary Stone Disease

Introduction

Because of phenotypic overlap between monogenic urinary stone diseases (USD), gene-specific analyses can result in missed diagnoses. We used targeted next generation sequencing (tNGS), including known and candidate monogenic USD genes, to analyze suspected primary hyperoxaluria (PH) or Dent disease (DD) patients genetically unresolved (negative; N) after Sanger analysis of the known genes. Cohorts consisted of 285 PH (PHN) and 59 DD (DDN) families.

Methods

Variants were assessed using disease-specific and population databases plus variant assessment tools and categorized using the American College of Medical Genetics (ACMG) guidelines. Prior Sanger analysis identified 47 novel PH or DD gene pathogenic variants.

Results

Screening by tNGS revealed pathogenic variants in 14 known monogenic USD genes, accounting for 45 families (13.1%), 27 biallelic and 18 monoallelic, including 1 family with a copy number variant (CNV). Recurrent genes included the following: SLC34A3 (n = 13), CLDN16 (n = 8), CYP24A1 (n = 4), SLC34A1 (n = 3), SLC4A1 (n = 3), APRT (n = 2), CLDN19 (n = 2), HNF4A1 (n = 2), and KCNJ1 (n = 2), whereas ATP6V1B1, CASR, and SLC12A1 and missed CNVs in the PH genes AGXT and GRHPR accounted for 1 pedigree each. Of the 48 defined pathogenic variants, 27.1% were truncating and 39.6% were novel. Most patients were diagnosed before 18 years of age (76.1%), and 70.3% of biallelic patients were homozygous, mainly from consanguineous families.

Conclusion

Overall, in patients suspected of DD or PH, 23.9% and 7.3% of cases, respectively, were caused by pathogenic variants in other genes. This study shows the value of a tNGS screening approach to increase the diagnosis of monogenic USD, which can optimize therapies and facilitate enrollment in clinical trials.

THE FUNCTIONAL STATE OF THE RENAL PARENCHYMA AFTER VARIOUS VIDEO ENDOSURGICAL METHODS OF TREATMENT OF PATIENTS WITH LARGE AND COMPLEX KIDNEY STONES

The work is based on the analysis of literature data devoted to the problem of preserving the functional state of the kidneys with various video endoscopic methods of surgical treatment of large and complex kidney stones. The purpose of the review is to highlight the likelihood of deterioration in the functional state of the kidneys in the postoperative period. A detailed analysis of postoperative outcomes in various minimally invasive methods of treatment of patients with large and complex kidney stones was carried out, with an overview of the possibility of using dynamic nephroscintigraphy as a method of objectively assessing the functional state of the kidneys.

Chronic Kidney Disease: Strategies to Retard Progression

Chronic kidney disease (CKD), defined as the presence of irreversible structural or functional kidney damages, increases the risk of poor outcomes due to its association with multiple complications, including altered mineral metabolism, anemia, metabolic acidosis, and increased cardiovascular events. The mainstay of treatments for CKD lies in the prevention of the development and progression of CKD as well as its complications. Due to the heterogeneous origins and the uncertainty in the pathogenesis of CKD, efficacious therapies for CKD remain challenging. In this review, we focus on the following four themes: first, a summary of the known factors that contribute to CKD development and progression, with an emphasis on avoiding acute kidney injury (AKI); second, an etiology-based treatment strategy for retarding CKD, including the approaches for the common and under-recognized ones; and third, the recommended approaches for ameliorating CKD complications, and the final section discusses the novel agents for counteracting CKD progression.

Safety, pharmacodynamics, and exposure-response modeling results from a first-in-human phase 1 study of nedosiran (PHYOX1) in primary hyperoxaluria

Primary hyperoxaluria (PH) is a family of ultra-rare autosomal recessive inherited disorders of hepatic glyoxylate metabolism characterized by oxalate overproduction. Nedosiran is an RNA interference agent that inhibits hepatic lactate dehydrogenase, the enzyme responsible for the common, final step of oxalate production in all three genetic subtypes of PH. Here, we assessed in a two-part, randomized, single-ascending-dose, phase 1 study (PHYOX1) the safety, pharmacokinetics, pharmacodynamics, and exposure-response of subcutaneous nedosiran in 25 healthy participants (Group A) and 18 patients with PH1 or PH2 (Group B). Group A received nedosiran (0.3, 1.5, 3.0, 6.0, then 12.0 mg/kg) or placebo, and Group B received open-label nedosiran (1.5, 3.0, or 6.0 mg/kg). No significant safety concerns were identified. Injection site reactions (four or more hours post dose) occurred in 13.3% of participants in Group A and 27.8% of participants in Group B. Mean maximum reduction in 24-hour urinary oxalate excretion from baseline to day 57 (end of study) across Group B dose cohorts was 55% (range: 22%-100%) after single-dose nedosiran, with 33% participants reaching normal 24-hour urinary oxalate excretion. Based on the available modeling and simulation data, a fixed monthly dose of nedosiran 160 mg (free acid; equivalent to 170 mg sodium salt) in adults was associated with the highest proportion of simulated individuals achieving normal or near-normal 24-hour urinary oxalate excretion and fewest fluctuations in urinary oxalate response. Thus, single-dose nedosiran demonstrated acceptable safety and evidence of a pharmacodynamic effect in both PH1 and PH2 subpopulations consistent with its mechanism of action.

Clinical profile of a Polish cohort of children and young adults with cystinuria

Background

Cystinuria is an inherited disorder that results in increased excretion of cystine in the urine. It accounts for about 1–2% of pediatric kidney stones. In this study, we sought to identify the clinical characteristics of patients with cystinuria in a national cohort.

Methods

This was a retrospective study involving 30 patients from the Polish Registry of Inherited Tubulopathies. Initial data and that from a 6-month follow-up were analyzed. Mutational analysis was performed by targeted Sanger sequencing and, if applicable, MLPA analysis was used to detect large rearrangements.

Results

SLC7A9 mutations were detected in 15 children (50%; 10 males, 5 females), SLC3A1 mutations in 14 children (47%; 5 males, 9 females), and bigenic mutations in one male patient. The first clinical symptoms of the disease were detected at a median of 48 months of age (range 3–233 months). When individuals with different mutations were compared, there were no differences identified in gender, age of diagnosis, presence of UTI or urolithiasis, eGFR, calcium, or cystine excretion. The most common initial symptoms were urolithiasis in 26 patients (88%) and urinary tract infections in 4 patients (13%). Urological procedures were performed in 18 out of 30 (60%).

Conclusions

The clinical course of cystinuria is similar among patients, regardless of the type of genetic mutation. Most patients require surgery before diagnosis or soon after it. Patients require combined urological and pharmacological treatment for prevention of stone recurrence and renal function preservation.