A comparative study of cellular diversity between the Xenopus pronephric and mouse metanephric nephron

The kidney is an essential organ that ensures bodily fluid homeostasis and removes soluble waste products from the organism. The functional units within the kidneys are epithelial tubules called nephrons. These tubules take in filtrate from the blood or coelom and selectively reabsorb nutrients through evolutionarily conserved nephron segments, leaving waste product to be eliminated in the urine. Genes coding for functional transporters are segmentally expressed, enabling nephrons to function as selective filters. The developmental patterning program that generates these segments is of great interest. The Xenopus embryonic kidney, the pronephros, has served as a valuable model to identify genes involved in nephron formation and patterning. Prior work has defined the gene expression profiles of Xenopus epithelial nephron segments via in situ hybridization strategies, but our understanding of the cellular makeup of the Xenopus pronephric kidney remains incomplete. Here, we scrutinize the cellular composition of the Xenopus pronephric nephron through comparative analyses with previous Xenopus studies and single-cell mRNA sequencing of the adult mouse kidney, this study reconstructs the cellular makeup of the pronephric kidney and identifies conserved cells, segments, and expression profiles. The data highlight significant conservation in podocytes, proximal and distal tubule cells and divergence in cellular composition underlying the evolution of the corticomedullary axis, while emphasizing the Xenopus pronephros as a model for physiology and disease.

Assessment of Hydroxyethyl Starch (6% HES 130/0.4) Kidney Storage in Critically Ill Dogs: A Post-mortem Prospective Study

Objective: Intravenous hydroxyethyl starch (HES) solutions are potentially nephrotoxic due to rapid renal tissue uptake, subsequent osmotic nephrosis, and long-lasting intracellular storage. This study aimed to investigate the severity of intracellular storage of HES in renal tissue samples from critically ill dogs receiving 6% HES 130/0.4.Materials and Methods: Fresh, post-mortem (<2 h after death) renal tissue samples were analyzed through histology, immunohistochemistry (HES 130/0.4-specific antibodies), and electron microscopy for the severity of renal tubular vacuolization (VAC), intravacuolar HES accumulation (ACC), and ultra-structure impairment. Moreover, we investigated the relationship between VAC or ACC grade and HES dose (mL/kg), duration of HES administration (h), and pre-HES plasma creatinine concentrations.Results: Histology revealed that 2/20 dogs (10%) had no, 11/20 dogs (55%) had mild, 5/20 dogs (25%) had moderate, and 2/20 dogs (10%) had severe VAC. Immunohistochemistry revealed that 5/20 dogs (25%) had no, 6/20 dogs (30%) had mild, 7/20 dogs (35%) had moderate, and 2/20 dogs (10%) had severe ACC. Both changes were predominantly found in the distal tubular epithelium of mild and moderate cases, and all tubular segments were affected in severe cases. Seven of 20 dogs (35%) had osmotic nephrosis (ON). On electron microscopy, large granules with an electron-dense content were repeatedly detected in individual cells, mainly in the distal tubules. No correlation was found between cumulative HES dose or duration of HES administration and VAC grade, ACC grade, or presence/absence of ON.Conclusion: A high percentage of dogs had renal tubular HES storage and one-third of dogs showed HES-induced ON. Short-term HES administration caused VAC and ACC, regardless of the dose or duration of administration. In contrast to previous studies, HES 130/0.4 deposits were mainly located in the renal distal tubule.

Revisiting The Role of Notch in Nephron Segmentation: Notch is required for proximal, not distal fate selection during mouse and human nephrogenesis

Notch signaling promotes maturation of nephron epithelia, but its proposed contribution to nephron segmentation into proximal and distal domains has been called into doubt. We leveraged single cell and bulk RNA-seq, quantitative immunofluorescent lineage/fate tracing, and genetically modified human iPSC to revisit this question in developing mouse kidneys and human kidney organoids. We confirmed that Notch signaling is needed for maturation of all nephron lineages, and thus mature lineage markers fail to detect a fate bias. By contrast, early markers identified a distal fate bias in cells lacking Notch2, and a concomitant increase in early proximal and podocyte fates in cells expressing hyperactive Notch1 was observed. Orthogonal support for a conserved role for Notch signaling in the distal/proximal axis segmentation is provided by the ability of Nicastrin-deficient hiPSCs-derived organoids to differentiate into TFA2B+ distal tubule and CDH1 connecting segment progenitors, but not into HNF4A+ or LTL+ proximal progenitors.

Abstract MP35: Pharmacological Inhibition And Knockout Of K ir 7.1 Does Not Affect The Development Of Salt-Sensitive Hypertension In The Dahl SS Rat

Ion channels play a vital role in the kidney’s ability to maintain electrolyte homeostasis, and mutations of certain inwardly rectifying K + channels (K ir ) have been associated with various tubulopathies that can cause salt-wasting and as a consequence, low blood pressure. K ir 7.1 is a member of the K ir family, that helps maintain resting membrane potential; however, its role in the kidney is not well understood. Immunohistochemistry in the kidney confirmed that K ir 7.1 is expressed in both aquaporin 2 and sodium chloride co-transporter positive cells, suggesting it may affect distal tubule K + handling. We hypothesized that K ir 7.1 is involved in renal K + homeostasis and may influence the development of salt-sensitive (SS) hypertension. To examine the role of K ir 7.1 during the development of SS hypertension, we used both a genetic knockout of the gene encoding K ir 7.1, Kcnj13 , on the Dahl SS background and pharmacological inhibition; SS Kcnj13-/- was lethal and we used SS Kcnj13+/- . Mean arterial pressure (MAP) in response to a high salt diet was determined by telemetry or arterial catheter. In the genetic model, there was no difference in MAP development between wild type and SS Kcnj13+/- rats (153±6 vs. 159±7, mmHg; n=11 for each group) after 3 weeks on a 4% NaCl diet. Additionally, there were no differences in K + or Na + urinary excretion in WT vs. SS Kcnj13+/- . For the pharmacological studies, ML418, a novel and highly specific K ir 7.1 inhibitor, was administered daily by i.v. infusion during 2 weeks of 8% NaCl diet. While no significant differences in MAP or K + excretion were observed between vehicle or drug treated rats, administration of ML418 had significantly increased urinary Na + excretion (197±54 vs. 333±21, Na/Cre, vehicle vs. ML418; n≥3 for each group, p=0.02). Moreover, equivalent short circuit current measurements of polarized mCCD cells demonstrated that K ir 7.1 antagonism by ML418 reduced vectoral Na + transport. Overall, these results indicate that K ir 7.1 can impact renal Na + homeostasis, but loss of basolateral K ir 7.1 conductance is insufficient to alter development of hypertension, likely due to compensation by the primary basolateral K ir ’s in the distal nephron such as K ir 4.1 and K ir 5.1.

Pengaruh Pemberian Minuman Beralkohol (Ciu) Terhadap Histomorfometri Ren Mencit (Mus musculus L.)

Ciu merupakan salah satu minuman beralkohol yang banyak dikonsumsi oleh masyarakat Indonesia. Konsumsi Ciu dapat merusak jaringan dan organ tubuh, karena hasil metabolisme alkohol merupakan molekul reaktif yang berupa Reactive Oxygen Species (ROS). Penelitian bertujuan untuk menganalisis pengaruh konsumsi Ciu terhadap perubahan histomorfologi ren. Penelitian menggunakan 15 ekor mencit jantan dengan Desain Rancangan Acak Lengkap dengan 3 kelompok perlakuan dan 5 ulangan, yaitu T0: mencit tidak diberikan perlakuan Ciu, T1: mencit diberi perlakuan Ciu 1 x 0,2ml/hari, dan T2: mencit diberi perlakuan Ciu 2 x 0,2ml/hari. Parameter pengukuran antara lain bobot ren, diameter glomerulus, lebar ruang Bowman, ukuran sel epitel dan diameter lumen tubulus kontortus proksimal, dan ukuran sel epitel dan diameter lumen tubulus kontortus distal. Data yang diperoleh dianalisis menggunakan uji Analysis of Variance (ANOVA), dilanjutkan dengan uji Duncanpada taraf kepercayaan 95%. Hasil penelitian menunjukkan bahwa pemberian Ciu memberikan pengaruh nyata (P<0,05) terhadap bobot ren, ukuran sel epitel tubulus kontortus proksimal, dan diameter lumen tubulus kontortus distal. Kesimpulan, pemberian Ciu pada mencit dapat merubah histomorfometri dan menurunkan bobot ren. Ciu is one of an alcoholic beverages that widely consumed by Indonesian people. Ciu consumption could damage body tissues and organs, because the result of alcohol metabolism is a reactive molecule that forms Reactive Oxygen Species (ROS). The study aims to analyze the effect of Ciu consumption on ren histomorphometry changes. The study used 15 male mice with Completed Random Design with 3 treatment groups and 5 repetitions, i.e. T0: mice were not given Ciu treatment, T1: mice were treated with Ciu 1 x 0,2ml/day, T2: mice were treated with Ciu 2 x 0,2ml/day. The measurement parameters are ren weight, glomerular diameter, Bowman space width, epithelial cell size and lumen diameter of proximal tubules, and epithelial cell size and lumen diameter of distal tubules. Data obtained were analyzed using the Analysis of Variance (ANOVA) test, followed by Duncan’s test at 95% confidence level. The result of the study showed that giving Ciu had a significant effect on ren weight (P<0,05), epithelial cell size of proximal tubule, and lumen diameter of distal tubule. In conclusion, Ciu given to mice could change the histomorphometry and decrease weight of its ren.

Atypical histological abnormalities in an adult patient with nephronophthisis harboring NPHP1 deletion: a case report

Background Nephronophthisis (NPHP) is a chronic tubular interstitial disorder that exhibits an autosomal recessive genetic form and causes progressive renal failure in children. Patients with NPHP rarely show urinary abnormalities, edema, or hypertension. Thus, NPHP is often detected only when renal failure becomes advanced. NPHP can be divided into three types based on the age of end-stage renal failure, i.e., infant type (approximately 5 years old), juvenile type (approximately 13–14 years old), and adolescent type (approximately 19 years old). Here, we report a case of NPHP diagnosed by genetic analysis at 26 years of age with atypical histological abnormalities. Case presentation A 26-year-old woman showed no growth disorders or urinary abnormalities in annual school physical examinations. However, at a check-up at 26 years old, she exhibited renal dysfunction (eGFR 26 mL/min/1.73 m2). Urine tests indicated low specific gravity of urine, but not proteinuria or microscopic hematuria. Urinary β2-microglobulin was high (805 μg/L), and renal biopsy was performed for definitive diagnosis. Histological findings showed no significant findings in glomeruli. However, moderate fibrosis was observed in the interstitial area, and moderate atrophy was observed in the tubules. There were no significant findings in immunofluorescence analysis, and no electron dense deposits were detected by electron microscopy. Although cyst-like expansion of the tubules was unclear, tubular atrophy was dominantly found in the distal tubule by cytokeratin 7 staining. Genetic analysis of the NPHP1 gene showed complete deletion of this gene, leading to a definitive diagnosis of NPHP. Conclusions NPHP is not merely a pediatric disease and is relatively high incidence in patients with adult onset end-stage of renal disease. In this case, typical histological abnormalities, such as cyst-like expansion of the tubular lesion, were not observed, and diagnosis was achieved by genetic analysis of the NPHP1 gene, which is responsible for the onset of NPHP. In patients with renal failure with tubular interstitial disease dominantly in the distal tubules, it is necessary to discriminate NPHP, even in adult cases.

Epidemiology of Distal Renal Tubular Acidosis: A Study Using Linked UK Primary Care and Hospital Data

<b><i>Introduction:</i></b> Distal renal tubular acidosis (dRTA), or RTA type 1, a rare inherited or acquired disease, is a disorder of the distal tubule caused by impaired urinary acid secretion. Due to associated conditions and nonspecific symptoms, dRTA may go undetected. This analysis aims to estimate the prevalence of dRTA in the UK Clinical Practice Research Datalink (CPRD) databases and extrapolate it to European Union Five (EU5) populations. <b><i>Methods:</i></b> A retrospective analysis was conducted using the CPRD GOLD database and linked Hospital Episode Statistics (HES) data to identify diagnosed and potentially undiagnosed or miscoded patients (suspected patients). Patients’ records with at least one diagnosis code for dRTA, RTA, specific autoimmune diseases, or renal disorders recorded between January 1987 and November 2017 were obtained and analyzed. An algorithm was developed to detect potentially undiagnosed/miscoded dRTA, based on associated conditions and prescriptions. <b><i>Results:</i></b> A total of 216 patients with diagnosis of RTA or dRTA were identified (with 98 linked to hospital data), and 447 patients were identified as having suspected dRTA. dRTA prevalence for 2017 was estimated between 0.46 (recorded cases, of which 22.1% were considered primary) and 1.60 when including suspected cases (7.6% primary) per 10,000 people. Prescription and clinical records of diagnosed patients revealed a wide range of comorbidities and a need for pharmacological treatment to manage associated symptoms. <b><i>Conclusion:</i></b> The study provides new estimates of dRTA prevalence in Europe and suggests that patients may often be unreported or miscoded, potentially confounding appropriate disease management.

Validity of Serum Uromodulin as Early Diagnosis Marker of Diabetic Nephropathy in T2DM

Increased prevalence of DM is accompanied by increased in its various complications include diabetic nephropathy, which can lead to end stage renal disease (ESRD). Urinary albumin-creatinine ratio (uACR) is the gold standard for diabetic nephropathy; however, it has several limitations, including the inability to early diagnose due to the absence of increased level in uACR. Uromodulin is produced by thick ascending limb (TAL) at Henle’s loop and early distal tubule of nephron. Uromodulin will decrease when tubular atrophy occurs in early stage of renal impairment with normoalbuminuria. The aim of this study was to determine the validity of serum uromodulin in type 2 diabetes mellitus (T2DM) in identifying diabetic nephropathy by comparing it with uACR as gold standard. This study was a cross-sectional analytical observational study at Dr. Hasan Sadikin (RSHS) Bandung from June to August 2020. Subjects consisted of 62 patiens with T2DM. Results showed that the serum uromodulin level had a sensitivity of 93.3%, a specificity of 88.2%, a positive predictive value of 95.5%, a negative predictive value of 83.3%, and an accuracy of 91,9% and an AUC value of 0.975. The cut-off point of serum uromodulin in this study was 47.195 ng/mL. In conclusion, serum uromodulin, when compared to the uACR as the gold standard, has good sensitivity and specificity for identifying diabetic nephropathy.

MO001THE EUROPEAN DRTA REGISTRY: AN INITIAL DATA ANALYSIS*

Background and Aims Distal renal tubular acidosis (dRTA) is a rare disorder characterised by an inability of the distal tubule to secrete acid, leading to metabolic acidosis. Clinical consequences typically include hypokalaemia, hypercalciuria with nephrocalcinosis and/or urolithiasis, as well as bone disease. Treatment with adequate alkali supplementation corrects the acidosis and hypercalciuria, but there are few data on long-term outcome. In 2018, a registry for dRTA was established by the European Society for Paediatric Nephrology, hosted by the European Rare Kidney Disease Reference Network. Here, we present an initial analysis of data in the registry. Method Analysis of data entered into the registry by the cut-off data of 18/11/2020. Results A total of 135 patients had been entered, of which 106 had additional data from an annual follow-up visit. Median age at last visit was 10 years (range 0-54), including 16 adults (&gt;17y). Genetic testing had been performed in 91 subjects and causative variants were reported in 74 (81%). Pertinent clinical details according to genetic group are listed in table 1. Treatment was provided with at least 15 different preparations, containing citrate or bicarbonate, given in 1-10 (median 3) daily doses. Adequate treatment at last follow-up, as judged by a plasma bicarbonate level &gt;21 mmol/l and a urine calcium-creatinine ratio in the age-specific normal range was present in 46% of subjects. There was a trend for higher eGFR and height SDS in subjects with adequate treatment compared to those without, but this was not statistically significant. Conclusion Currently available data demonstrate the difficulties in treating dRTA, with less than half of subjects achieving adequate control of their acidosis. By collecting long-term data, the registry will provide important information on the prognosis and complications of dRTA and to what degree these can be prevented with treatment. Enrollment of further, especially adult patients will contribute to our understanding of this rare disorder.

Distal Renal Tubular Acidosis: ERKNet/ESPN Clinical Practice Points

Distal renal tubular acidosis (dRTA) is characterised by an impaired ability of the distal tubule to excrete acid, leading to metabolic acidosis. Associated complications include bone disease, growth failure, urolithiasis and hypokalaemia. Due to its rarity, there is a limited evidence to guide diagnosis and management, however, available data strongly suggest that metabolic control of the acidosis by alkali supplementation can halt or revert almost all complications. Despite this, cohort studies show that adequate metabolic control is present in only about half of patients, highlighting problems with treatment provision or adherence. With these clinical practice points the authors, part of the working groups tubulopathies in the European Rare Kidney Disease Reference network (ERKnet) and inherited kidney diseases of the European Society for Paediatric Nephrology (ESPN) aim to provide guidance for the management of patients with dRTA to facilitate adequate treatment and establish an initial best practice standard against which treatment of patients can be audited.