Disease-associated missense mutations in the pore loop of polycystin-2 alter its ion channel function in a heterologous expression system.

Polycystin-2 (PC2) is mutated in ∼15% of patients with autosomal dominant polycystic kidney disease (ADPKD). PC2 belongs to the family of transient receptor potential (TRP) channels and can function as homotetramer. We investigated whether three disease-associated mutations (F629S, C632R or R638C) localized in the channel's pore loop alter ion channel properties of human PC2 expressed in Xenopus laevis oocytes. Expression of wildtype (WT) PC2 typically resulted in small but measurable Na+ inward currents in the absence of extracellular divalent cations. These currents were no longer observed, when individual pore mutations were introduced in WT PC2. Similarly, Na+ inward currents mediated by the F604P gain-of-function (GOF) PC2 construct (PC2 F604P) were abolished by each of the three pore mutations. In contrast, when the mutations were introduced in another GOF construct, PC2 L677A N681A, only C632R had a complete loss-of-function effect, whereas significant residual Na+ inward currents were observed with F629S (∼15 %) and R638C (∼30 %). Importantly, the R638C mutation also abolished the Ca2+ permeability of PC2 L677A N681A and altered its monovalent cation selectivity. To elucidate the molecular mechanisms by which the R638C mutation affects channel function, molecular dynamics (MD) simulations were used in combination with functional experiments and site-directed mutagenesis. Our findings suggest that R638C stabilizes ionic interactions between Na+ ions and the selectivity filter residue D643. This probably explains the reduced monovalent cation conductance of the mutant channel. In summary, our data support the concept that altered ion channel properties of PC2 contribute to the pathogenesis of ADPKD.

Revisiting the gene mutations and protein profile of WT 9-12: An autosomal dominant polycystic kidney disease cell line.

WT 9-12 is one of the cell lines commonly used for autosomal dominant polycystic kidney disease (ADPKD) studies. Previous studies had described the PKD gene mutations and polycystin expression in WT 9-12. Nonetheless, the mutations occurring in other ADPKD-associated genes have not been investigated. This study aims to revisit these mutations and protein profile of WT 9-12. Whole genome sequencing verified the presence of truncation mutation at amino acid 2556 (Q2556X) in PKD1 gene of WT 9-12. Besides, those variations with high impacts included single nucleotide polymorphisms (rs8054182, rs117006360, and rs12925771) and insertions and deletions (InDels) (rs145602984 and rs55980345) in PKD1L2; InDel (rs1296698195) in PKD1L3; and copy number variations in GANAB. Protein profiles generated from the total proteins of WT 9-12 and HK-2 cells were compared using isobaric tags for relative and absolute quantitation (iTRAQ) analysis. Polycystin-1 was absent in WT 9-12. The gene ontology enrichment and reactome pathway analyses revealed that the upregulated and downregulated proteins of WT 9-12 relative to HK-2 cell line leaded to signaling pathways related to immune response and amino acid metabolism, respectively. The ADPKD-related mutations and signaling pathways associated with differentially expressed proteins in WT 9-12 may help researchers in cell line selection for their studies.

Pain and Health-Related Quality of Life in Autosomal Dominant Polycystic Kidney Disease: Results from a National Patient-Powered Registry.

Rationale & Objective: Autosomal dominant polycystic kidney disease (ADPKD) affects health-related quality of life (HRQoL) including pain, discomfort, fatigue, emotional distress, and impaired mobility. Stakeholders prioritized kidney cyst-related pain as an important core outcome domain in clinical trials, leading to the development of disease-specific assessment tools. Study Design: The ADPKD Registry is hosted online with multiple disease-specific patient-reported outcomes modules to characterize the patient experience in the United States. Setting & Participants: The ADPKD Registry allows consented participants access to a Core Questionnaire that includes demographics, comorbid conditions, current symptoms, and kidney function. Participants complete subsequent modules on a 3-month schedule, including 2 validated HRQoL tools, the ADPKD-Pain and Discomfort Scale (ADPKD-PDS), the ADPKD Impact Scale (ADPKD-IS) and a Healthcare Access and Utilization module. Exposures: Patient-reported latest estimated glomerular filtration rate or creatinine used to calculate stage of chronic kidney disease. Outcomes: Health-related quality of life, measured using validated ADPKD-specific tools; access to polycystic kidney disease-specific health care. Analytical Approach: For the 2 HRQoL tools, scores were calculated for physical, emotional, and fatigue domains; pain severity; and pain interference (based on the licensed user manuals). Associations to health care access were also assessed. Results: By July 2022, 1,086 individuals with ADPKD completed at least 1 of the HRQoL modules, and 319 completed 4 over a year. Participants were an average age of 53. In total, 71% were women, and 91% were White, with all chronic kidney disease (CKD) stages represented. In total, 2.5% reported being treated with dialysis, and 23% had a kidney transplant. CKD stage 4/5 participants reported the most dull kidney pain, whereas sharp kidney pain was evenly distributed across early CKD stages. Dull kidney pain had an impact on sleep regardless of CKD stage. There was a strong positive correlation between the ADPKD-PDS and ADPKD-IS. Patients with a neutral or positive HRQoL were less likely to have been denied access to imaging or other care. Limitations: Currently, all the information collected is patient reported without health record validation of clinical variables. Conclusions: Use of the HRQoL tools in the ADPKD Registry provided a broad cross-sectional assessment in the United States and provided granular information on the burden of pain across the CKD spectrum in ADPKD. The ADPKD Registry allowed assessment of ADPKD impact in a community that experiences decline in health and kidney function over decades.

The Autosomal Dominant Polycystic Kidney Disease Registry is a longitudinal, patient-powered research tool created with the goal to better understand the impacts of ADPKD on affected individuals in the United States. Here, we analyze pain and other health-related quality of life outcomes in 1,086 individuals using validated tools and comment on the utility of these tools for future use in clinical trials and observational studies. We found that sharp pain, dull pain, fullness discomfort, and other related impacts affected individuals across the disease spectrum, although some participants reported more dull pain in later stages (CKD stages 4 and 5). Future analysis of these trends over time will be valuable in understanding how to assess and address the burden of pain in autosomal dominant polycystic kidney disease.

Kidney Cysts in Children With Alport Syndrome: A Report of 3 Cases.

Alport syndrome (AS) is a progressive hereditary kidney disease characterized by hematuria, proteinuria, and progressive kidney dysfunction accompanied by sensorineural hearing loss and ocular abnormalities. Pathogenic COL4A3-5 variants can result in different AS spectra. Further, kidney cysts have been reported in adults with AS. However, the relationship between kidney cysts and AS remains unclear. Here, we report 3 cases of AS in children that occurred with kidney cysts. The patient in case 1 was initially diagnosed with IgA nephropathy at the age of 8 years but later developed bilateral multiple kidney cysts at the age of 17 years, suggesting autosomal-dominant polycystic kidney disease. Whole-exome sequencing identified a pathogenic COL4A5 variant and confirmed the AS diagnosis. The patients in cases 2 and 3 had already been diagnosed with X-linked AS using kidney biopsy and genetic analysis. Initial kidney ultrasonography showed nephromegaly; however, kidney cyst formation was observed during their annual follow-up. Our study supports the association between AS and kidney cysts. Kidney cysts in adolescents with suspected AS should not discourage clinicians from testing for pathogenic COL4A3-COL4A5 variants. Early detection of kidney cysts is critical because it may indicate kidney disease progression.

Treatment for patients with autosomal dominant polycystic kidney disease in the chronic kidney disease without kidney replacement therapy in real-world clinical practice: a descriptive retrospective cohort study.

BACKGROUND: In real-world clinical practice, treatments selected for patients with autosomal dominant polycystic kidney disease (ADPKD) in the chronic kidney disease (CKD) without kidney replacement therapy (KRT) have not been reported. This study investigated the oral treatments used in these patients and the changes in their use in recent years. Additionally, we studied the factors affecting tolvaptan dose reduction or discontinuation. METHODS: This retrospective cohort study was conducted using the medical records of 160 hospitals in Japan. Patients with ADPKD or polycystic kidney disease registered on the database between January 2014 and December 2020 were selected. Changes in prescription proportions over time were assessed using the Cochran-Armitage test. We focused on patients prescribed with >15 mg of tolvaptan daily to identify the factors related to its dose reduction or discontinuation and used Multivariate Cox regression analysis to evaluate them. RESULTS: Tolvaptan use in patients with ADPKD in the CKD without KRT stage has increased. As of 2020, 25% of patients were treated with tolvaptan. Overall, 3639 patients with ADPKD were enrolled in the database, of whom 156 were treated with tolvaptan. Of these, 64 patients (41%) reduced or discontinued tolvaptan during the observation period. The presence of an estimated glomerular filtration rate <60 mL/min/1.73 m2 at the beginning of the treatment was associated with a higher risk of tolvaptan dose reduction or discontinuation. CONCLUSION: The proportion of patients with ADPKD treated with high-dose tolvaptan is increasing. However, patients with late-stage CKD tended to reduce or discontinue tolvaptan.

Activation of Polycystin-1 Signaling by Binding of Stalk-derived Peptide Agonists.

Polycystin-1 (PC1) is the membrane protein product of the PKD1 gene whose mutation is responsible for 85% of the cases of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is primarily characterized by the formation of renal cysts and potential kidney failure. PC1 is an atypical G protein-coupled receptor (GPCR) consisting of 11 transmembrane helices and an autocatalytic GAIN domain that cleaves PC1 into extracellular N-terminal (NTF) and membrane-embedded C-terminal (CTF) fragments. Recently, signaling activation of the PC1 CTF was shown to be regulated by a stalk tethered agonist (TA), a distinct mechanism observed in the adhesion GPCR family. A novel allosteric activation pathway was elucidated for the PC1 CTF through a combination of Gaussian accelerated molecular dynamics (GaMD), mutagenesis and cellular signaling experiments. Here, we show that synthetic, soluble peptides with 7 to 21 residues derived from the stalk TA, in particular, peptides including the first 9 residues (p9), 17 residues (p17) and 21 residues (p21) exhibited the ability to re-activate signaling by a stalkless PC1 CTF mutant in cellular assays. To reveal molecular mechanisms of stalk peptide-mediated signaling activation, we have applied a novel Peptide GaMD (Pep-GaMD) algorithm to elucidate binding conformations of selected stalk peptide agonists p9, p17 and p21 to the stalkless PC1 CTF. The simulations revealed multiple specific binding regions of the stalk peptide agonists to the PC1 protein including an "intermediate" bound yet inactive state. Our Pep-GaMD simulation findings were consistent with the cellular assay experimental data. Binding of peptide agonists to the TOP domain of PC1 induced close TOP-putative pore loop interactions, a characteristic feature of the PC1 CTF signaling activation mechanism. Using sequence covariation analysis of PC1 homologs, we further showed that the peptide binding regions were consistent with covarying residue pairs identified between the TOP domain and the stalk TA. Therefore, structural dynamic insights into the mechanisms of PC1 activation by stalk-derived peptide agonists have enabled an in-depth understanding of PC1 signaling. They will form a foundation for development of PC1 as a therapeutic target for the treatment of ADPKD.

Patient-Reported Outcomes Measures, Polycystic Kidney Disease Burden, and Outcomes in Autosomal Dominant Polycystic Kidney Disease.

Rationale & Objective: Using OVERTURE (NCT01430494) study data on patient-perceived health, health care utilization, and productivity in autosomal dominant polycystic kidney disease (ADPKD), this research was conducted to characterize the burden of illness in patients with ADPKD and assess whether patient-reported outcome (PRO) assessment scores predict clinical and health-economic outcomes. Study Design: Data were analyzed from a prospective, observational study. Setting & Participants: The study cohort comprised 3,409 individuals with ADPKD in 20 countries who were aged 12-78 years and were in chronic kidney disease (CKD) stages G1-G5 and Mayo risk subclasses 1A-1E. Predictors: Scores on PRO instruments, including disease-specific assessments [ADPKD-Impact Scale (ADPKD-IS), and ADPKD-Urinary Impact Scale (ADPKD-UIS)] and generic measures were assessed. Outcomes: Clinical variables [eg, height-adjusted total kidney volume (htTKV), estimated glomerular filtration rate (eGFR), and abdominal girth] and health-economic outcomes were assessed. Analytical Approach: Associations among variables were evaluated using Spearman correlations, logistic regression, and generalized linear mixed effects repeated measures models. Results: Baseline CKD stage and Mayo risk classification showed little correlation with baseline PRO scores; however, scores on disease-specific instruments and measures of physical functioning were worse at more severe CKD stages. PRO scores predicted hospitalizations and sick days at 6-18 months, with strongest associations noted for the ADPKD-IS. PRO scores were not associated with htTKV and eGFR, but worse PRO scores were associated with greater abdominal girth. Poor baseline ADPKD-IS scores were positively associated with occurrence of ADPKD-related symptoms up to 18 months, including kidney pain (OR, 5.30; 95% CI, 2.75-10.24), hematuria (OR, 4.58; 95% CI, 1.99-10.53), and urinary tract infection (OR, 4.41; 95% CI, 1.93-10.11; P < 0.001 for all). Limitations: A limitation of the study was the maximum 18 months of follow-up available to assess outcomes. Conclusions: PRO scores predicted clinical and health-economic outcomes, such as hospitalization and absence from work, underscoring the importance of quality of life assessment of individuals with ADPKD. Plain-Language Summary: Patient-reported outcomes (PROs) are increasingly recognized as important parameters for assessing the clinical and humanistic burden of autosomal dominant polycystic kidney disease (ADPKD). We analyzed data from the observational OVERTURE study to better characterize disease impact on quality of life and determine whether patient-perceived burden might predict outcomes. Scores on PRO assessment instruments predicted hospitalizations and sick days at 6-18 months, with associations strongest for the disease-specific ADPKD-Impact Scale. Compared to patients who rated their health-related quality of life as good, those with poor baseline scores were significantly more likely to report ADPKD-related signs and symptoms up to 18 months of follow-up. These findings support using disease-specific PRO assessment instruments to assess and predict the impact of ADPKD.

Autopsy of a 45-year-old Man with Liver Failure Due to Polycystic Liver Disease.

A 37-year-old man with autosomal polycystic kidney disease (ADPKD) was admitted to our hospital with a liver volume of 8,000 cm3. Hepatic arterial embolization was performed using a microcoil but was ineffective. Eight years later, the hepatomegaly progressed to liver failure and death. At autopsy, the liver weighed 21.5 kg, and the entire liver had been replaced by cysts; in the few remaining areas of liver parenchyma, microscopic, small cysts of various sizes and fibrosis were evident, with only a few normal hepatocytes observed. Hepatic arterial branches developed; however, the portal vein could not be observed.

A Case of Autosomal Dominant Polycystic Kidney Disease With Resolution of Massive Pericardial Effusion After Renal Transcatheter Artery Embolization.

A 68-year-old woman being treated with hemodialysis for autosomal dominant polycystic kidney disease was admitted for progressive dyspnea over 6 months. On chest radiography, her cardiothoracic ratio had increased from 52.2% 6 months prior, to 71%, and echocardiography revealed diffuse pericardial effusion and right ventricular diastolic insufficiency. A resultant pericardial tamponade was thought to be the cause of the patient's dyspnea, and therefore a pericardiocentesis was performed, with a total of 2,000mL of fluid removed. However, 21 days later the same amount of pericardial fluid had reaccumulated. The second pericardiocentesis was performed, followed by transcatheter renal artery embolization (TAE). The kidneys, which were hard on palpation before TAE, softened immediately after TAE. After resolution of the pericardial effusion was confirmed, the patient was discharged after 24 days in hospital. Twelve months later, the patient was asymptomatic, the cardiothoracic ratio decreased to 48% on chest radiography and computed tomography revealed no reaccumulation of pericardial effusion. This case illustrates a potential relationship between enlarged kidneys in autosomal dominant polycystic kidney disease and pericardial effusion.

Deep learning-based automated kidney and cyst segmentation of autosomal dominant polycystic kidney disease using single vs. multi-institutional data.

PURPOSE: This study aimed to investigate if a deep learning model trained with a single institution's data has comparable accuracy to that trained with multi-institutional data for segmenting kidney and cyst regions in magnetic resonance (MR) images of patients affected by autosomal dominant polycystic kidney disease (ADPKD). METHODS: We used TensorFlow with a Keras custom UNet on 2D slices of 756 MRI images of kidneys with ADPKD obtained from four institutions in the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) study. The ground truth was determined via a manual plus global thresholding method. Five models were trained with 80 % of all institutional data (n = 604) and each institutional data (n = 232, 172, 148, or 52), respectively, and validated with 10 % and tested on an unseen 10 % of the data. The model's performance was evaluated using the Dice Similarity Coefficient (DSC). RESULTS: The DSCs by the model trained with all institutional data ranged from 0.92 to 0.95 for kidney image segmentation, only 1-2 % higher than those by the models trained with single institutional data (0.90-0.93).In cyst segmentation, however, the DSCs by the model trained with all institutional data ranged from 0.83 to 0.89, which were 2-20 % higher than those by the models trained with single institutional data (0.66-0.86). CONCLUSION: The UNet performance, when trained with a single institutional dataset, exhibited similar accuracy to the model trained on a multi-institutional dataset. Segmentation accuracy increases with models trained on larger sample sizes, especially in more complex cyst segmentation.

Predicting autosomal dominant polycystic kidney disease progression: review of promising Serum and urine biomarkers.

Autosomal dominant polycystic kidney disease (ADPKD) is one of the leading causes of end-stage renal disease. In spite of the recent tremendous progress in the understanding of ADPKD pathogenesis, the molecular mechanisms of the disease remain incompletely understood. Considering emerging new targeted therapies for ADPKD, it has become crucial to disclose easily measurable and widely available biomarkers for identifying patients with future rapid disease progression. This review encompasses all the research with a shared goal of identifying promising serum or urine biomarkers for predicting ADPKD progression or response to therapy. The rate of the ADPKD progress varies significantly between patients. The phenotypic variability is only partly explained by the underlying genetic lesion diversity. Considering significant decline in kidney function in ADPKD is not usually evident until at least 50% of the parenchyma has been destroyed, conventional kidney function measures, such as glomerular filtration rate (GFR), are not suitable for monitoring disease progression in ADPKD, particularly in its early stages. Since polycystic kidney enlargement usually precedes the decline in GFR, height-adjusted total kidney volume (ht-TKV) has been accepted as an early biomarker for assessing disease severity in ADPKD patients. However, since measuring ht-TKV is time-consuming and observer-dependent, the identification of a sensitive and quickly measurable biomarker is of a great interest for everyday clinical practice. Throughout the last decade, due to development of proteomic and metabolomic techniques and the enlightenment of multiple molecular pathways involved in the ADPKD pathogenesis, a number of urine and serum protein biomarkers have been investigated in ADPKD patients, some of which seem worth of further exploring. These include copeptin, angiotensinogen, monocyte chemoattractant protein 1, kidney injury molecule-1 and urine-to-plasma urea ratio among many others. The aim of the current review is to provide an overview of all of the published evidence on potentially clinically valuable serum and urine biomarkers that could be used for predicting disease progression or response to therapy in patients with ADPKD. Hopefully, this review will encourage future longitudinal prospective clinical studies evaluating proposed biomarkers as prognostic tools to improve management and outcome of ADPKD patients in everyday clinical practice.

Clinical findings, underlying pathogenetic processes and treatment of vascular dysfunction in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder characterized by the development of fluid-filled cysts in the kidneys. The primary cause of ADPKD is mutations in the PKD1 (polycystic kidney disease 1) or PKD2 (polycystic kidney disease 2) gene. Patients with ADPKD often develop a variety of vascular abnormalities, which have a major impact on the structure and function of the blood vessels and can lead to complications such as hypertension, intracranial aneurysm (ICAN), and atherosclerosis. The progression of ADPKD involves intricate molecular and cellular processes that lead to the development of these vascular abnormalities. Our understanding of these processes remains incomplete, and available treatment options are limited. The aim of this review is to delve into the underlying mechanisms of these vascular abnormalities and to explore potential interventions.

Polycystin-1 Interacting Protein-1 (CU062) Interacts with the Ectodomain of Polycystin-1 (PC1).

The PKD1 gene, encoding protein polycystin-1 (PC1), is responsible for 85% of cases of autosomal dominant polycystic kidney disease (ADPKD). PC1 has been shown to be present in urinary exosome-like vesicles (PKD-ELVs) and lowered in individuals with germline PKD1 mutations. A label-free mass spectrometry comparison of urinary PKD-ELVs from normal individuals and those with PKD1 mutations showed that several proteins were reduced to a degree that matched the decrease observed in PC1 levels. Some of these proteins, such as polycystin-2 (PC2), may be present in a higher-order multi-protein assembly with PC1-the polycystin complex (PCC). CU062 (Q9NYP8) is decreased in ADPKD PKD-ELVs and, thus, is a candidate PCC component. CU062 is a small glycoprotein with a signal peptide but no transmembrane domain and can oligomerize with itself and interact with PC1. We investigated the localization of CU062 together with PC1 and PC2 using immunofluorescence (IF). In nonconfluent cells, all three proteins were localized in close proximity to focal adhesions (FAs), retraction fibers (RFs), and RF-associated extracellular vesicles (migrasomes). In confluent cells, primary cilia had PC1/PC2/CU062 + extracellular vesicles adherent to their plasma membrane. In cells exposed to mitochondrion-decoupling agents, we detected the development of novel PC1/CU062 + ring-like structures that entrained swollen mitochondria. In contact-inhibited cells under mitochondrial stress, PC1, PC2, and CU062 were observed on large, apically budding extracellular vesicles, where the proteins formed a reticular network on the membrane. CU062 interacts with PC1 and may have a role in the identification of senescent mitochondria and their extrusion in extracellular vesicles.

A novel heterozygous PKD1 variant causing alternative splicing in a Chinese family with autosomal dominant polycystic kidney disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by pathogenic variants of PKD1 and PKD2. Compared to PKD2-related patients, patients with PKD1 pathogenic variants have more severe symptoms, present a gradual decline in renal function, and finally progress to end-stage kidney disease with an earlier mean onset age. METHODS: In this study, trio exome sequencing (ES) was performed to reveal the genetic etiology in a Chinese family clinically diagnosed with polycystic kidney, followed by validation through Sanger sequencing on both genomic DNA and cDNA levels. Subsequently, targeted preimplantation genetic testing was provided for the family. RESULTS: A novel heterozygous PKD1 variant (c.1717_1722+11del) was detected in the proband and other clinically-affected relatives. Interestingly, cDNA sequencing demonstrated that the variant, despite being annotated as non-frameshift within exon 8, impacted the splicing of PKD1. Two abnormal transcription products were formed: one induced frameshift, while the other caused 133 amino acids to be inserted between exon 8 and exon 9. CONCLUSIONS: Our study revealed a novel PKD1 variant using ES as the cause of ADPKD in a Chinese family with multiple affected members. The variant at the exon-intron boundary would induce alternative splicing, which should not be excluded from genetic analysis. Validated on the cDNA level could provide more comprehensive genetic information for disease stratification. And the novel variant expands the spectrum of PKD1 variants in ADPKD. The recurrent risk could be blocked accordingly for the families' offspring.

Effects of tolvaptan discontinuation in patients with autosomal dominant polycystic kidney disease: a post hoc pooled analysis.

BACKGROUND: Tolvaptan slows kidney function decline in patients with autosomal dominant polycystic kidney disease (ADPKD) who are at risk of rapid progression. Given that treatment requires commitment to long-term use, we evaluated the effects of tolvaptan discontinuation on the trajectory of ADPKD progression. METHODS: This was a post hoc analysis of pooled data from two clinical trials of tolvaptan (TEMPO 2:4 [NCT00413777] and TEMPO 3:4 [NCT00428948]), an extension trial (TEMPO 4:4 [NCT01214421]), and an observational study (OVERTURE [NCT01430494]) that enrolled patients from the other trials. Individual subject data were linked longitudinally across trials to construct analysis cohorts of subjects with a tolvaptan treatment duration > 180 days followed by an off-treatment observation period of > 180 days. For inclusion in Cohort 1, subjects were required have ≥ 2 outcome assessments during the tolvaptan treatment period and ≥ 2 assessments during the follow-up period. For Cohort 2, subjects were required to have ≥ 1 assessment during the tolvaptan treatment period and ≥ 1 assessment during the follow-up period. Outcomes were rates of change in estimated glomerular filtration rate (eGFR) and total kidney volume (TKV). Piecewise-mixed models compared changes in eGFR or TKV in the on-treatment and post-treatment periods. RESULTS: In the Cohort 1 eGFR population (n = 20), the annual rate of eGFR change (in mL/min/1.73 m2) was -3.18 on treatment and -4.33 post-treatment, a difference that was not significant (P = 0.16), whereas in Cohort 2 (n = 82), the difference between on treatment (-1.89) and post-treatment (-4.94) was significant (P < 0.001). In the Cohort 1 TKV population (n = 11), TKV increased annually by 5.18% on treatment and 11.69% post-treatment (P = 0.06). In Cohort 2 (n = 88), the annual TKV growth rates were 5.15% on treatment and 8.16% post-treatment (P = 0.001). CONCLUSIONS: Although limited by small sample sizes, these analyses showed directionally consistent acceleration in measures of ADPKD progression following the discontinuation of tolvaptan.

Tolvaptan and Kidney Function Decline in Older Individuals With Autosomal Dominant Polycystic Kidney Disease: A Pooled Analysis of Randomized Clinical Trials and Observational Studies.

Rationale & Objective: Tolvaptan is indicated for treatment of patients with autosomal dominant polycystic kidney disease (ADPKD) at risk of rapid progression. Participants aged 56-65 years constituted a small proportion of the Replicating Evidence of Preserved Renal Function: an Investigation of Tolvaptan Safety and Efficacy in ADPKD (REPRISE) trial population. We assessed effects of tolvaptan on estimated glomerular filtration rate (eGFR) decline in participants aged >55 years. Study Design: This was a pooled data analysis from 8 studies of tolvaptan or non-tolvaptan standard of care (SOC). Setting & Participants: Participants aged >55 years with ADPKD were included. Data on participants in >1 study were linked longitudinally for maximum follow-up duration, with matching for age, sex, eGFR, and chronic kidney disease (CKD) stage to minimize confounding. Interventions: Tolvaptan or non-tolvaptan SOC. Outcomes: Treatment effects on annualized eGFR decline were compared using mixed models with fixed effects for treatment, time, treatment-by-time interaction, and baseline eGFR. Results: In the pooled studies, 230 tolvaptan-treated and 907 SOC participants were aged >55 years at baseline. Ninety-five participant pairs from each treatment group were matched, all in CKD G3 or G4, ranging from 56.0 to 65.0 years (tolvaptan) or from 55.1 to 67.0 years (SOC). The eGFR annual decline rate was significantly reduced by 1.66 mL/min/1.73 m2 (95% CI, 0.43-2.90; P = 0.009) in the tolvaptan group compared with SOC (-2.33 versus -3.99 mL/min/1.73 m2) over 3 years. Limitations: Limitations include potential bias because of study population differences (bias risk was reduced through matching and multiple regression adjustment); vascular disease history data was not uniformly collected, and therefore not adjusted; and natural history of ADPKD precludes evaluating certain clinical endpoints within the study time frame. Conclusions: In individuals aged 56-65 years with CKD G3 or G4, compared to a SOC group with mean GFR rate of decline ≥3 mL/min/1.73 m2/year, tolvaptan was associated with efficacy similar to that observed in the overall indication. Funding: Otsuka Pharmaceutical Development & Commercialization, Inc (Rockville, MD). Trial Registration: TEMPO 2:4 (NCT00413777); phase 1 tolvaptan trial (no NCT number; trial number 156-06-260); phase 2 tolvaptan trial (NCT01336972); TEMPO 4:4 (NCT01214421); REPRISE (NCT02160145); long-term tolvaptan safety extension trial (NCT02251275); OVERTURE (NCT01430494); HALT Progression of Polycystic Kidney Disease (HALT-PKD) study B (NCT01885559).

Mutation Analysis of Autosomal-Dominant Polycystic Kidney Disease Patients.

Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by bilateral kidney cysts that ultimately lead to end-stage kidney disease. While the major causative genes of ADPKD are PKD1 and PKD2, other genes are also thought to be involved. Fifty ADPKD patients were analyzed by exome sequencing or multiplex ligation-dependent probe amplification (MLPA), followed by long polymerase chain reaction and Sanger sequencing. Variants in PKD1 or PKD2 or GANAB were detected in 35 patients (70%). Exome sequencing identified 24, 7, and 1 variants in PKD1, PKD2, and GANAB, respectively, in 30 patients. MLPA analyses identified large deletions in PKD1 in three patients and PKD2 in two patients. We searched 90 cyst-associated genes in 15 patients who were negative by exome sequencing and MLPA analyses, and identified 17 rare variants. Four of them were considered "likely pathogenic" or "pathogenic" variants according to the American College of Medical Genetics and Genomics guidelines. Of the 11 patients without a family history, four, two, and four variants were found in PKD1, PKD2, and other genes, respectively, while no causative gene was identified in one patient. While the pathogenicity of each variant in these genes should be carefully assessed, a comprehensive genetic analysis may be useful in cases of atypical ADPKD.

Caregiver Burden of Autosomal Dominant Polycystic Kidney Disease: A Qualitative Study.

Rationale & Objective: There is limited published research on how autosomal dominant polycystic kidney disease (ADPKD) impacts caregivers. This study explored how caregivers of individuals with ADPKD perceive the burdens placed on them by the disease. Study Design: Qualitative study consisting of focus groups and interviews. Discussions were conducted by trained interviewers using semi-structured interview guides. Setting & Participants: The research was conducted in 14 countries in North America, South America, Asia, Australia, and Europe. Eligible participants were greater than or equal to 18 years old and caring for a child or adult diagnosed with ADPKD. Analytical Approach: The concepts reported were coded using qualitative research software. Data saturation was reached when subsequent discussions introduced no new key concepts. Results: Focus groups and interviews were held with 139 participants (mean age, 44.9 years; 66.9% female), including 25 participants who had a diagnosis of ADPKD themselves. Caregivers reported significant impact on their emotional (74.1%) and social life (38.1%), lost work productivity (26.6%), and reduced sleep (25.2%). Caregivers also reported worry about their financial situation (23.7%). In general, similar frequencies of impact were reported among caregivers with ADPKD versus caregivers without ADPKD, with the exception of sleep (8.0% vs 28.9%, respectively), leisure activities (28.0% vs 40.4% respectively), and work/employment (12.0% vs 29.8%, respectively). Limitations: The study was observational and designed to elicit concepts, and only descriptive analyses were conducted. Conclusions: These findings highlight the unique burden on caregivers in ADPKD, which results in substantial emotional, social, and professional/financial impact.

Development of an enterocutaneous fistula from an intestinal perforation in a patient with autosomal dominant polycystic kidney disease.

We herein report a case of enterocutaneous fistula in a patient with autosomal dominant polycystic kidney disease (ADPKD). A 37-year-old Japanese man was admitted to our hospital. Three months prior to transfer to our hospital, he developed intense flank pain with gross hematuria. His serum creatinine had decreased to 7.8 mg/dL and hemodialysis was started, but gross hematuria persisted and he developed hypotension. Upon admission, plain chest radiography did not reveal any free air, but computed tomography (CT) showed generalized ventral subcutaneous air from the head to the lower extremities and enlarged kidneys. Enterography showed leakage of contrast medium from the descending colon into the subcutaneous area. C-reactive protein was 23.1 mg/dL. A colostomy was placed in the transverse colon proximal to the perforation, and systemic subcutaneous drainage was performed. The fever subsequently resolved, and the C-reactive protein test became negative. Three months later, renal artery embolization was performed, and 12 months thereafter, CT showed a marked decrease in kidney size. We assume that a markedly enlarged kidney leaded to intestinal perforation, which developed into an enterocutaneous fistula. Consequently, intestinal fluid leaked into the subcutaneous cavity of the abdominal wall and spread systemically, resulting in extensive subcutaneous abscesses.