Autosomal Recessive Polycystic Kidney Disease Patients Research Articles

A Potential Therapy Using Antisense Oligonucleotides to Treat Autosomal Recessive Polycystic Kidney Disease.

(1) Background: Autosomal recessive polycystic kidney disease (ARPKD) is a rare ciliopathy characterized by progressively enlarged kidneys with fusiform dilatation of the collecting ducts. Loss-of-function mutations in the PKHD1 gene, which encodes fibrocystin/polyductin, cause ARPKD; however, an efficient treatment method and drug for ARPKD have yet to be found. Antisense oligonucleotides (ASOs) are short special oligonucleotides which function to regulate gene expression and alter mRNA splicing. Several ASOs have been approved by the FDA for the treatment of genetic disorders, and many are progressing at present. We designed ASOs to verify whether ASOs mediate the correction of splicing further to treat ARPKD arising from splicing defects and explored them as a potential treatment option. (2) Methods: We screened 38 children with polycystic kidney disease for gene detection using whole-exome sequencing (WES) and targeted next-generation sequencing. Their clinical information was investigated and followed up. The PKHD1 variants were summarized and analyzed, and association analysis was carried out to analyze the relationship between genotype and phenotype. Various bioinformatics tools were used to predict pathogenicity. Hybrid minigene analysis was performed as part of the functional splicing analysis. Moreover, the de novo protein synthesis inhibitor cycloheximide was selected to verify the degraded pathway of abnormal pre-mRNAs. ASOs were designed to rescue aberrant splicing, and this was verified. (3) Results: Of the 11 patients with PKHD1 variants, all of them exhibited variable levels of complications of the liver and kidneys. We found that patients with truncating variants and variants in certain regions had a more severe phenotype. Two splicing variants of the PKHD1 genotypes were studied via the hybrid minigene assay: variants c.2141-3T>C and c.11174+5G>A. These cause aberrant splicing, and their strong pathogenicity was confirmed. We demonstrated that the abnormal pre-mRNAs produced from the variants escaped from the NMD pathway with the use of the de novo protein synthesis inhibitor cycloheximide. Moreover, we found that the splicing defects were rescued by using ASOs, which efficiently induced the exclusion of pseudoexons. (4) Conclusion: Patients with truncating variants and variants in certain regions had a more severe phenotype. ASOs are a potential drug for treating ARPKD patients harboring splicing mutations of the PKHD1 gene by correcting the splicing defects and increasing the expression of the normal PKHD1 gene.

The Clinical and Mutational Spectrum of 69 Turkish Children with Autosomal Recessive or Autosomal Dominant Polycystic Kidney Disease: A Multicenter Retrospective Cohort Study

Introduction: Autosomal recessive polycystic kidney disease (ARPKD) is associated with pathogenic variants in the PKHD1 gene. Autosomal dominant polycystic kidney disease (ADPKD) is mainly associated with pathogenic variants in PKD1 or PKD2. The present study aimed to identify the clinical and genetic features of Turkish pediatric ARPKD and ADPKD patients. Methods: This multicenter, retrospective cohort study included 21 genetically confirmed ARPKD and 48 genetically confirmed ADPKD patients from 7 pediatric nephrology centers. Demographic features, clinical, and laboratory findings at presentation and during 12-month intervals were recorded. Results: The median age of the ARPKD patients at diagnosis was lower than the median age of ADPKD patients (10.5 months [range: 0–15 years] vs. 5.2 years [range: 0.1–16 years], respectively, [p = 0.014]). At the time of diagnosis, the median eGFR in the ARPKD patients was lower compared to that of ADPKD patients (81.6 [IQR: 28.7–110.5] mL/min/1.73 m2 and 118 [IQR: 91.2–139.8] mL/min/1.73 m2, respectively, [p = 0.0001]). In total, 11 (52.4%) ARPKD patients had malnutrition; 7 (33.3%) patients had growth retardation at presentation; and 4 (19%) patients had both malnutrition and growth retardation. At diagnosis, 8 (16.7%) of the ADPKD patients had malnutrition, and 5 (10.4%) patients had growth retardation. The malnutrition, growth retardation, and hypertension rates at diagnosis were higher in the ARPKD patients than the ADPKD patients (p = 0.002, p = 0.02, and p = 0.0001, respectively). ARPKD patients with malnutrition and growth retardation had worse renal survival compared to the patients without (p = 0.03 and p = 0.01). Similarly, ADPKD patients with malnutrition had worse renal survival compared to the patients without (p = 0.002). ARPKD patients with truncating variants had poorer 3- and 6-year renal outcome than those carrying non-truncating variants (p = 0.017). Conclusion: Based on renal survival analysis, type of genetic variant, growth retardation, and/or malnutrition at presentation were observed to be factors associated with progression to chronic kidney disease (CKD). Differentiation of ARPKD and ADPKD, and identification of the predictors of the development of CKD are vital for optimal management of patients with ARPKD or ADPKD.

Mosaic PKHD1 in Polycystic Kidneys Caused Aberrant Protein Expression in the Mitochondria and Lysosomes

Autosomal recessive polycystic kidney disease (ARPKD) is a severe renal cystic disease caused mainly by the polycystic kidney and hepatic disease 1 (PKHD1). However, the genetic cause, pathologic features, and mechanism of action of ARPKD are not well known. Here, we identified a family with ARPKD. Two siblings harbored biallelic variants in PKHD1 (c.7205G>A, c.7973T>A). We determined that the “de novo” variant, c.7205G>A, arose from the mosaicism of the father and had a 7.4% level. Pathologic characterization, using biopsy analysis, was evidenced with predominant cystic dilation in proximal tubules, slight ectasia of collecting ducts, defective ciliogenesis, and impaired cell-cell junctions in renal tubules and collecting ducts. Exosome proteomics in the urine from patients with ARPKD were markedly different from those of controls, with the most significant alterations occurring in mitochondrial and lysosomal proteins. Expression of the proteins of OXPHOS was downregulated sharply, in parallel with upregulated expression of the proteins involved in glycolysis in patients with ARPKD. Several lysosomal proteins associated with renal lesions were more abundant in the exosome of the patient than in controls. Moreover, the lysosomal enzyme sulfamidase, which is produced by the SGSH gene, was abrupt uniquely in the exosome of the patient. Consistently, swollen mitochondria and abundant lysosomes were visualized in the mutant tubular epithelial cells of patients with mutant PKHD1. Collectively, these findings provide new insights on the pathophysiology of the polycystic kidney due to PKHD1 deficiency. PKHD1 mosaicism should be considered in genetic testing of ARPKD patients.

Early childhood height-adjusted total kidney volume as a risk marker of kidney survival in ARPKD

Autosomal recessive polycystic kidney disease (ARPKD) is characterized by bilateral fibrocystic changes resulting in pronounced kidney enlargement. Impairment of kidney function is highly variable and widely available prognostic markers are urgently needed as a base for clinical decision-making and future clinical trials. In this observational study we analyzed the longitudinal development of sonographic kidney measurements in a cohort of 456 ARPKD patients from the international registry study ARegPKD. We furthermore evaluated correlations of sonomorphometric findings and functional kidney disease with the aim to describe the natural disease course and to identify potential prognostic markers. Kidney pole-to-pole (PTP) length and estimated total kidney volume (eTKV) increase with growth throughout childhood and adolescence despite individual variability. Height-adjusted PTP length decreases over time, but such a trend cannot be seen for height-adjusted eTKV (haeTKV) where we even observed a slight mean linear increase of 4.5 ml/m per year during childhood and adolescence for the overall cohort. Patients with two null PKHD1 variants had larger first documented haeTKV values than children with missense variants (median (IQR) haeTKV 793 (450–1098) ml/m in Null/null, 403 (260–538) ml/m in Null/mis, 230 (169–357) ml/m in Mis/mis). In the overall cohort, estimated glomerular filtration rate decreases with increasing haeTKV (median (IQR) haeTKV 210 (150–267) ml/m in CKD stage 1, 472 (266–880) ml/m in stage 5 without kidney replacement therapy). Strikingly, there is a clear correlation between haeTKV in the first eighteen months of life and kidney survival in childhood and adolescence with ten-year kidney survival rates ranging from 20% in patients of the highest to 94% in the lowest quartile. Early childhood haeTKV may become an easily obtainable prognostic marker of kidney disease in ARPKD, e.g. for the identification of patients for clinical studies.

MO026CLINICAL AND MUTATIONAL SPECTRUM OF CHILDREN WITH AUTOSOMAL RECESSIVE AND AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE

Abstract Background and Aims Cystic kidney diseases are a heterogeneous group of chronic renal disease. Autosomal recessive polycystic kidney disease (ARPKD) is generally diagnosed in utero or at birth due to mutations in PKHD1 gene. Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease commonly associated with mutations in PKD1 or PKD2. In this study, we aimed to investigate clinical and genetic features of ARPKD and ADPKD in a group of Turkish patients. Method A total of 69 children with genetically confirmed ARPKD (10 females, 11 males) or ADPKD (28 females, 20 males) from seven pediatric nephrology centers were included in this study. Demographic features, family history, clinical and laboratory findings at presentation and during 12 months intervals were collected. Results For ARPKD patients, the median age at diagnosis was 10.5 (IQR; 0.75-58.5) months. Consanguinity between parents was present in 11 patients (52.4%). At the time of diagnosis, 14 (66.7%) patients had eGFR<90 ml/min/1.73 m2. Mean duration of follow-up was 4.1±3,7 years. At the last visit, median eGFR was 74 (IQR; 43-126) ml/min/1.73m2. A total of 6 patients (28,6%) underwent a renal replacement therapy (RRT), 3 of them died in infancy and 2 of them had renal transplantation during follow up. All patients had bi-allelic PKHD1 mutation. For ADPKD patients, the mean age at diagnosis was 5.5±4.6 years. At the time of diagnosis 11 (22.9%) patients had eGFR<90 ml/min/1.73m2. Mean duration of follow-up was 2,7±2.3 years. At the last visit, median eGFR was 114 (IQR; 98-135) ml/min/1.73m2. Only one patient underwent a renal transplantation. A total of 42 patients (87.5%) had a heterozygous PKD1 mutation while 6 (12.5%) had a heterozygous PKD2 mutation. The rate of growth retardation, hypertension at diagnosis and progression to chronic kidney disease (CKD) were higher in patients with PKHD1 mutation than the patients with PKD1 or PKD2 mutation (p < 0.001, p < 0.001 and p = 0.001, respectively). In kidney survival analysis, mutation type, growth retardation at presentation, increased renal echogenity in ultrasonography were found as independent risk factors for progression to CKD. Conclusion Cystic kidney diseases are one of the most clinically and genetically heterogenous diseases. Differentiating them and establishing the predictors for CKD development is important to provide appropriate management including choosing appropriate donor in renal transplantation.

Refining genotype–phenotype correlations in 304 patients with autosomal recessive polycystic kidney disease and PKHD1 gene variants

Autosomal recessive polycystic kidney disease (ARPKD) is asevere disease of early childhood that is clinically characterized by fibrocystic changes of the kidneys and the liver. The main cause of ARPKD are variants in the PKHD1 gene encoding the large transmembrane protein fibrocystin. The mechanisms underlying the observed clinical heterogeneity in ARPKD remain incompletely understood, partly due to the fact that genotype-phenotype correlations have been limited to the association of biallelic null variants in PKHD1 with the most severe phenotypes. In this observational study we analyzed a deep clinical dataset of 304 patients with ARPKD from two independent cohorts and identified novel genotype-phenotype correlations during childhood and adolescence. Biallelic null variants frequently show severe courses. Additionally, our data suggest that the affected region in PKHD1 is important in determining the phenotype. Patients with two missense variants affecting amino acids 709-1837 of fibrocystin or a missense variant in this region and a null variant less frequently developed chronic kidney failure, and patients with missense variants affecting amino acids 1838-2624 showed better hepatic outcome. Variants affecting amino acids 2625-4074 of fibrocystin were associated with poorer hepatic outcome. Thus, our data expand the understanding of genotype-phenotype correlations in pediatric ARPKD patients and can lay the foundation for more precise and personalized counselling and treatment approaches.

Occurrence of Portal Hypertension and Its Clinical Course in Patients With Molecularly Confirmed Autosomal Recessive Polycystic Kidney Disease (ARPKD).

Purpose: Liver involvement in autosomal recessive polycystic kidney disease (ARPKD) leads to the development of portal hypertension and its complications. The aim of this study was to analyze the occurrence of the portal hypertension and its clinical course and the dynamics in patients with molecularly confirmed ARPKD in a large Polish center. Moreover, the available options in diagnostics, prevention and management of portal hypertension in ARPKD will be discussed.Materials and Methods: The study group consisted of 17 patients aged 2.5–42 years. All patients had ARPKD diagnosis confirmed by molecular tests. Retrospective analysis included laboratory tests, ultrasound and endoscopic examinations, transient elastography and clinical evaluation.Results: Any symptom of portal hypertension was established in 71% of patients. Hypersplenism, splenomegaly, decreased portal flow and esophageal varices were found in 47, 59, 56, and 92% of patients, respectively. Gastrointestinal bleeding occurred in four of 17 patients. Endoscopic variceal ligation (EVL) was performed at least once in nine patients with esophageal varices.Conclusions: Portal hypertension and its complications are present in a significant percentage of ARPKD patients. They should be under the care of multidisciplinary nephrology-gastroenterology/hepatology team. Complications of portal hypertension may occur early in life. Endoscopic methods of preventing gastroesophageal bleeding, such as endoscopic variceal ligation, are effective and surgical techniques, including liver transplantation, are required rarely.

The carboxy-terminus of the human ARPKD protein fibrocystin can control STAT3 signalling by regulating SRC-activation.

Autosomal recessive polycystic kidney disease (ARPKD) is mainly caused by variants in the PKHD1 gene, encoding fibrocystin (FC), a large transmembrane protein of incompletely understood cellular function. Here, we show that a C‐terminal fragment of human FC can suppress a signalling module of the kinase SRC and signal transducer and activator of transcription 3 (STAT3). Consistently, we identified truncating genetic variants specifically affecting the cytoplasmic tail in ARPKD patients, found SRC and the cytoplasmic tail of fibrocystin in a joint dynamic protein complex and observed increased activation of both SRC and STAT3 in cyst‐lining renal epithelial cells of ARPKD patients.

P0041CHARACTERISTICS OF URINE-DERIVED RENAL EPITHELIAL CELLS (UREC) FROM CHILDREN WITH POLYCYSTIC KIDNEY DISEASE (PKD)

Abstract Background and Aims In hereditary PKD, epithelial cell defects are mostly caused by mutation of proteins of the cilia-centrosome complex. Use of primary cells from patients allows to study specific cell characteristics and altered activation of signal pathways in epithelial cell function-related culture models. In this ex vivo approach, comparison of cell properties is based on defined genetic origin and can be related to kidney function at the time of UREC collection, revealing consequences of genetic disposition and kidney-stress related changes on cell function. Method The study considers patients with genetically confirmed causes of PKD, autosomal recessive polycystic kidney disease (ARPKD), nephronophtisis (NPH), Bardet-Biedl syndrome (BBS), and age-matched controls with normal kidney function. UREC are grown from cellular urine sediment using selective growth conditions. Primary cells are cultured up-to 21 days (passages 2 & 3) and tested with respect to their proliferation, tubular origin and epithelial properties in 2D/3D culture conditions. To allow pathway analysis and improve control conditions, immortalized UREC lines are also included. Results UREC preparations of cohorts from ARPKD, NPH, and BBS patients, and controls were studied quantitatively to determine specific epithelial cell properties. Considering basic characteristics of each primary culture including cell morphology, expression of epithelial markers, and formation of cell-cell adhesions, the potential of UREC cells to polarize and generate liquid-filled epithelial spheroids was measured. The capacity of lumen formation in 3D culture strongly varies among individual cell preparations and appears to reflect the genetic origin of UREC cells, whereas no correlation to (remaining) kidney function (eGFR) is observed. Conclusion Determining specific, quantitative UREC cell properties related to genetics and kidney function, we expect to gain a better mechanistic understanding of cellular and renal epithelial defects in PKD patients. Ex vivo analysis based on UREC cells may provide options for testing of personalized pharmaceutical intervention.

A Chinese family of autosomal recessive polycystic kidney disease identified by whole exome sequencing.

Autosomal recessive polycystic kidney disease (ARPKD) is an autosomal recessive hepatorenal fibrocystic syndrome. The majority of ARPKD patients progress to end-stage renal disease. Precise molecular diagnosis of ARPKD has proven valuable for understanding its mechanism and selecting optimal therapy. A Chinese family with ARPKD was recruited in current study. The clinical characteristics of ARPKD patient were collected from medical records and the potential responsible genes were studied by the whole exome sequencing (WES). Candidate pathogenic variants were validated by Sanger sequencing. Both renal manifestation and hepatobiliary phenotype were observed. WES revealed compound heterozygous mutations of polycystic kidney and hepatic disease 1 genes, NM_138694: c.751G>T, (p.Asp251Tyr) and c.3998_4004delACCTGAA (p.Asn1333Thr fs × 13), which were confirmed by Sanger sequencing. Moreover, the mutations in the proband and its affected sib were co-segregated with the phenotype. The novel mutation in polycystic kidney and hepatic disease 1 gene identified by WES might be molecular pathogenic basis of this disorder.

SAT-436 CLINICAL AND GENETIC CHARACTERISTICS OF AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE (ARPKD) PATIENTS FROM OMAN AND PKHD1 FOUNDER MUTATIONS

The Omani population has a high prevalence of rare genetic disorders, and their study provides unique clinical and genetic insights. Autosomal recessive polycystic kidney disease (ARPKD) is one of the leading causes of kidney and liver-associated morbidity and mortality in the country. We aimed to describe the clinical and genetic profile of ARPKD patients from Oman. A group of 75 patients and relatives (40 males and 35 females) from apparently 33 unrelated families, who were referred to the National Genetic Centre in Oman between January 2015 and December 2018, were studied. This included 41 patients with a clinical diagnosis of ARPKD, their parents (n=24) and siblings or relatives (n=10). Genetic analysis of PKHD1 was performed through next generation sequencing (NGS) and Sanger sequencing. A clinical diagnosis was made in 5 patients prenatally, 24 were diagnosed during the infancy period (0-1 year), nine during early childhood (2-8 years) and 3 at later ages (9-13 years). The main clinical features of patients included hypertension, hepatic fibrosis and splenomegaly. 25 patients had documented chronic renal failure at a median age of 3 years. 24 out of 33 families had a family history suggesting an autosomal recessive pattern of inheritance, and there was known consanguinity in 22 families (67%). A molecular genetic diagnosis of ARPKD with biallelic PKHD1 mutations was confirmed in 30 families (n= 38 patients), giving a detection rate of 91%. Three families remained genetically unsolved. In total, only four different PKHD1 missense pathogenic mutations were identified: c.107C>T; (Thr36Met), c.406A>G; (Thr136Ala), c.4870C>T; (Arg1624Trp) and c.9370C>T; (His3124Tyr) located in exons 3, 6, 32 and 58, respectively. The c.406A>G; (Thr136Ala) is a novel missense mutation that was detected homozygously in one family and heterozygously with c.107C>T; (Thr36Met) allele in 5 other families. Overall, the most commonly detected pathogenic allele was c.107C>T; (Thr36Met), which was seen in 24 families. All four PKHD1 mutations were detected in patients from all governorates of the country except, Musandam, Al Wusta and Dhofar. Molecular genetic screening of suspected ARPKD cases produces a highly yield of genetic diagnosis. The four PKHD1 missense mutations may suggest common founder alleles in Omani population and allow cost effective targeted PCR analysis of these specific alleles to be a useful diagnostic tool.

Clinical courses and complications of young adults with Autosomal Recessive Polycystic Kidney Disease (ARPKD)

Autosomal recessive polycystic kidney disease (ARPKD) is a severe pediatric hepatorenal disorder with pronounced phenotypic variability. A substantial number of patients with early diagnosis reaches adulthood and some patients are not diagnosed until adulthood. Yet, clinical knowledge about adult ARPKD patients is scarce. Here, we describe forty-nine patients with longitudinal follow-up into young adulthood that were identified in the international ARPKD cohort study ARegPKD. Forty-five patients were evaluated in a cross-sectional analysis at a mean age of 21.4 (±3.3) years describing hepatorenal findings. Renal function of native kidneys was within CKD stages 1 to 3 in more than 50% of the patients. Symptoms of hepatic involvement were frequently detected. Fourteen (31%) patients had undergone kidney transplantation and six patients (13%) had undergone liver transplantation or combined liver and kidney transplantation prior to the visit revealing a wide variability of clinical courses. Hepatorenal involvement and preceding complications in other organs were also evaluated in a time-to-event analysis. In summary, we characterize the broad clinical spectrum of young adult ARPKD patients. Importantly, many patients have a stable renal and hepatic situation in young adulthood. ARPKD should also be considered as a differential diagnosis in young adults with fibrocystic hepatorenal disease.

Transient Elastography for Detection of Liver Fibrosis in Children With Autosomal Recessive Polycystic Kidney Disease.

Introduction: Congenital hepatic fibrosis (CHF) is invariably present in all patients with autosomal recessive polycystic kidney disease (ARPKD) but is usually clinically asymptomatic. The portal hypertension in the course of CHF develops and progresses over time, so an early detection of liver fibrosis remains crucial.Aim: The aim of the study was to evaluate a predictive value of transient elastography for evaluating liver disease progress in pediatric ARPKD patients.Material and Methods: The study group encompassed 21 pediatric patients with ARPKD and 20 healthy children (control group) from The Children's Memorial Health Institute in Warsaw, Poland. Liver fibrosis was determined by assessing the liver stiffness (LS) with transient elastography (FibroScan®, FS) using size-appropriate probes. In ARPKD group the laboratory findings, results of an abdominal ultrasound examination, and an endoscopic gastroduodenoscopy were also analyzed.Results: Compared with healthy controls, patients with ARPKD had significantly increased median LS values (22 vs. 4.25 kPa, p < 0.0001). Based on FS results, ARPKD group was divided into two subgroups: patients (n = 5) with LS results suggestive of no fibrosis or minimal fibrosis (LS < 6.9 kPa, METAVIR fibrosis stage 0–1) and patients (n = 16) with LS results suggestive of at least significant liver fibrosis (LS ≥ 6.9 kPa, METAVIR fibrosis stage 2–4). In the first subgroup (no fibrosis or minimal fibrosis), all patients had no signs of portal hypertension. In the subgroup with at least significant liver fibrosis, splenomegaly was observed in 87.5% of patients and thrombocytopenia in 69% of patients. An endoscopic gastroduodenoscopy was performed in 15 out of 21 ARPKD patients, nine patients (60%) had esophageal varices. All of these patients had LS results suggestive of at least significant liver fibrosis.Conclusions: TE by FibroScan can be used as an additional method for evaluating liver disease progress in pediatric ARPKD patients.

Gastrostomy Tube Insertion in Pediatric Patients With Autosomal Recessive Polycystic Kidney Disease (ARPKD): Current Practice.

Introduction: Autosomal recessive polycystic kidney disease (ARPKD) is a severe hepatorenal disorder of childhood. Early renal disease in ARPKD may require renal replacement therapy and is associated with failure to thrive resulting in a need for nasogastric tube feeding or gastrostomy. In ARPKD patients, the benefit of a gastrostomy in nutrition and growth needs to be weighed against the potential risk of complications of congenital hepatic fibrosis (CHF) and portal hypertension like variceal bleeding. CHF in ARPKD has thus been considered as a relative contraindication for gastrostomy insertion. Yet, data on gastrostomies in pediatric patients with ARPKD is lacking.Methods: We conducted a web-based survey study among pediatric nephrologists, pediatric hepatologists and pediatric gastroenterologists on their opinions on and experiences with gastrostomy insertion in ARPKD patients.Results: 196 participants from 39 countries shared their opinion. 45% of participants support gastrostomy insertion in all ARPKD patients, but portal hypertension is considered to be a contraindication by a subgroup of participants. Patient-specific data was provided for 38 patients indicating complications of gastrostomy that were in principal comparable to non-ARPKD patients. Bleeding episodes were reported in 3/38 patients (7.9%). Two patients developed additional severe complications. Gastrostomy was retrospectively considered as the right decision for the patient in 35/38 (92.1%) of the cases.Conclusions: This report on the results of an online survey gives first insights into the clinical practice of gastrostomy insertion in ARPKD patients. For the majority of participating physicians benefits of gastrostomy insertion retrospectively outweigh complications and risks. More data will be required to lay the foundation for clinical recommendations.

Design and Implementation of the Hepatorenal Fibrocystic Disease Core Center Clinical Database: A Centralized Resource for Characterizing Autosomal Recessive Polycystic Kidney Disease and Other Hepatorenal Fibrocystic Diseases.

Autosomal recessive polycystic kidney disease (ARPKD) and other hepatorenal fibrocystic diseases (HRFD) are relatively rare recessive disorders that constitute an important set of childhood nephropathies. Little is known about fundamental pathogenesis, and advances toward clinical trials will require well-characterized patient cohorts and the development of predictive and prognostic biomarkers. Such studies in rare diseases require greater collaboration than the efforts in common diseases where large patient repositories can be built at a single site. For the HRFD, clinical and translational research studies would be well served by centralized case accrual that coordinates collection of clinical data, biospecimens (DNA and tissues), and genetic information. As a part of the NIH-funded Hepatorenal Fibrocystic Disease Core Center, we have established a web-accessible portal to enroll patients with ARPKD and other HRFD and compile baseline and longitudinal clinical information in a REDCap-based clinical database. This central database is structured to collect clinical data from patients throughout the Americas (North, Central, and South). By using informatic analyses, we have defined the first data-driven estimates of ARPKD-related neonatal mortality, as well as the incidence and prevalence of this disease. These data indicate that while ARPKD is a rare disorder, there are hundreds of patients potentially available for deep clinical phenotyping in the United States alone. The centralization and sharing of clinical information and biomaterials from ARPKD and other HRFD patients hold the potential to accelerate progress in understanding disease pathways. Once the database is mature, the well-characterized patient cohorts will provide an important resource for developing clinical trials to evaluate new targeted therapeutic interventions in this spectrum of disorders.

Molecular genetic analysis of PKHD1 by next-generation sequencing in Czech families with autosomal recessive polycystic kidney disease

BackgroundAutosomal recessive polycystic kidney disease (ARPKD) is an early-onset form of polycystic kidney disease that often leads to devastating outcomes for patients. ARPKD is caused by mutations in the PKHD1 gene, an extensive gene that encodes for the ciliary protein fibrocystin/polyductin. Next-generation sequencing is presently the best option for molecular diagnosis of ARPKD. Our aim was to set up the first study of ARPKD patients from the Czech Republic, to determine the composition of their mutations and genotype-phenotype correlations, along with establishment of next-generation sequencing of the PKHD1 gene that could be used for the diagnosis of ARPKD patients.MethodsMutational analysis of the PKHD1 gene was performed in 24 families using the amplicon-based next-generation sequencing (NGS) technique. In patients without 2 causal mutations identified by NGS, subsequent MLPA analysis of the PKHD1 gene was carried out.ResultsTwo underlying mutations were detected in 54 % of families (n = 13), one mutation in 13 % of families (n = 3), and in 33 % of families (n = 8) no mutation could be detected. Overall, seventeen different mutations (5 novel) were detected, including deletion of one exon. The detection rate in our study reached 60 % in the entire cohort of patients; but 90 % in the group of patients who fulfilled all clinical criteria of ARPKD, and 42 % in the group of patients with unknown kidney pathology. The most frequent mutation was T36M, accounting for nearly 21 % of all identified mutations.ConclusionsNext-generation sequencing of the PKHD1 gene is a very useful method of molecular diagnosis in patients with a full clinical picture of ARPKD, and it has a high detection rate. Furthermore, its relatively low costs and rapidity allow the molecular genetic analysis of patients without the full clinical criteria of ARPKD, who might also have mutations in the PKHD1 gene.

Initial evaluation of hepatic T1 relaxation time as an imaging marker of liver disease associated with autosomal recessive polycystic kidney disease (ARPKD).

Autosomal recessive polycystic kidney disease (ARPKD) is a potentially lethal multi-organ disease affecting both the kidneys and the liver. Unfortunately, there are currently no non-invasive methods to monitor liver disease progression in ARPKD patients, limiting the study of potential therapeutic interventions. Herein, we perform an initial investigation of T1 relaxation time as a potential imaging biomarker to quantitatively assess the two primary pathologic hallmarks of ARPKD liver disease: biliary dilatation and periportal fibrosis in the PCK rat model of ARPKD. T1 relaxation time results were obtained for five PCK rats at 3 months of age using a Look-Locker acquisition on a Bruker BioSpec 7.0 T MRI scanner. Six three-month-old Sprague-Dawley (SD) rats were also scanned as controls. All animals were euthanized after the three-month scans for histological and biochemical assessments of bile duct dilatation and hepatic fibrosis for comparison. PCK rats exhibited significantly increased liver T1 values (mean ± standard deviation = 935 ± 39 ms) compared with age-matched SD control rats (847 ± 26 ms, p = 0.01). One PCK rat exhibited severe cholangitis (mean T1 = 1413 ms), which occurs periodically in ARPKD patients. The observed increase in the in vivo liver T1 relaxation time correlated significantly with three histological and biochemical indicators of biliary dilatation and fibrosis: bile duct area percent (R = 0.85, p = 0.002), periportal fibrosis area percent (R = 0.82, p = 0.004), and hydroxyproline content (R = 0.76, p = 0.01). These results suggest that hepatic T1 relaxation time may provide a sensitive and non-invasive imaging biomarker to monitor ARPKD liver disease.

Autosomal recessive polycystic kidney disease: the prototype of the hepato-renal fibrocystic diseases.

Autosomal recessive polycystic kidney disease (ARPKD) is a severe, typically early onset form of renal cystic disease. The care of ARPKD patients has traditionally been the purview of pediatric nephrologists for management of systemic hypertension and progressive renal insufficiency. However, the disease has multisystem manifestations and a comprehensive care strategy frequently requires a multidisciplinary team. In severely affected infants, the diagnosis often is first suspected by obstetricians when enlarged, echogenic kidneys and oligohydramnios are detected on prenatal ultrasounds. Neonatologists are central to the care of these infants, who may have respiratory compromise due to pulmonary hypoplasia and massively enlarged kidneys. Among neonatal survivors, a subset of ARPKD patients has clinically significant congenital hepatic fibrosis, which can lead to portal hypertension, requiring close monitoring by pediatric hepatologists. Surgical consultation may be sought to access pre-emptive nephrectomy to relieve mass effect, placement of dialysis access, surgical shunting procedures, and kidney and/or liver transplantation. Recent data suggest that children with ARPKD may be at risk of neurocognitive dysfunction, and may require neuropsychological referral. In addition to these morbidities, families of patients with ARPKD face decisions regarding genetic testing of affected children, testing of asymptomatic siblings, or consideration of preimplantation genetic diagnosis for future pregnancies. These issues require the input of genetic counselors, geneticists, and reproductive endocrinologists. As a result, the management of ARPKD requires the involvement of multiple subspecialists, as well as the general pediatrician, in a complex care network. In this review, we discuss the genetics of this disorder and provide an overview of the associated pathobiology; outline the spectrum of clinical manifestations of ARPKD and the management of organ-specific complications; discuss other disorders that involve genes encoding cilia-associated proteins that can clinically mimic ARPKD; review the animal models available for preclinical studies; and finally, consider future directions for potential targeted therapies.

A labor and cost effective next generation sequencing of PKHD1 in autosomal recessive polycystic kidney disease patients

The Sanger sequencing of patients with recessive polycystic kidney disease is challenging due to the length and heterogeneous mutational spectrum of the PKHD1 gene. Next generation sequencing (NGS) might thus be of special interest to search for PKHD1 mutations. The study involved a total of 22 patients with autosomal recessive polycystic kidney disease (ARPKD) and 8 parents of non-available ARPKD patients. Five pools of 6 samples each were sequenced with the Personal Genome Machine (PGM, Ion Torrent). For each DNA pool, a total of 109 fragments that covered the entire PKHD1 coding sequence were amplified in only two tubes followed by library preparation and NGS with the PGM. To validate the technique, each pool contained the DNA of at least one patient with known mutation. The putative mutations identified in each pool were confirmed and assigned to specific individuals through Sanger sequencing.All but one of the 109 amplicons were successfully read, and we identified the two PKHD1 mutations in 11 of the ARPKD cases, one mutation in 9 patients, and no mutation in only 2 patients. Six of the 8 parents from non-available patients were mutation carriers.The reported procedure would facilitate the large scale analysis of PKHD1 with a significant reduction in cost and labor.

Autosomal recessive polycystic kidney disease: a hepatorenal fibrocystic disorder with pleiotropic effects.

Autosomal recessive polycystic kidney disease (ARPKD) is an important cause of chronic kidney disease in children. The care of ARPKD patients has traditionally been the realm of pediatric nephrologists; however, the disease has multisystem effects, and a comprehensive care strategy often requires a multidisciplinary team. Most notably, ARPKD patients have congenital hepatic fibrosis, which can lead to portal hypertension, requiring close follow-up by pediatric gastroenterologists. In severely affected infants, the diagnosis is often first suspected by obstetricians detecting enlarged, echogenic kidneys and oligohydramnios on prenatal ultrasounds. Neonatologists are central to the care of these infants, who may have respiratory compromise due to pulmonary hypoplasia and massively enlarged kidneys. Surgical considerations can include the possibility of nephrectomy to relieve mass effect, placement of dialysis access, and kidney and/or liver transplantation. Families of patients with ARPKD also face decisions regarding genetic testing of affected children, testing of asymptomatic siblings, or consideration of preimplantation genetic diagnosis for future pregnancies. They may therefore interface with genetic counselors, geneticists, and reproductive endocrinologists. Children with ARPKD may also be at risk for neurocognitive dysfunction and may require neuropsychological referral. The care of patients and families affected by ARPKD is therefore a multidisciplinary effort, and the general pediatrician can play a central role in this complex web of care. In this review, we outline the spectrum of clinical manifestations of ARPKD and review genetics of the disease, clinical and genetic diagnosis, perinatal management, management of organ-specific complications, and future directions for disease monitoring and potential therapies.