State of the Science and Ethical Considerations for Preimplantation Genetic Testing for Monogenic Cystic Kidney Diseases and Ciliopathies.

There is a broad phenotypic spectrum of monogenic polycystic kidney diseases (PKDs). These disorders often involve cilia-related genes and lead to the development of fluid-filled cysts and eventual kidney function decline and failure. Preimplantation genetic testing for monogenic (PGT-M) disorders has moved into the clinical realm. It allows prospective parents to avoid passing on heritable diseases to their children, including monogenic PKD. The PGT-M process involves embryo generation through in vitro fertilization, with subsequent testing of embryos and selective transfer of those that do not harbor the specific disease-causing variant(s). There is a growing body of literature supporting the success of PGT-M for autosomal-dominant and autosomal-recessive PKD, although with important technical limitations in some cases. This technology can be applied to many other types of monogenic PKD and ciliopathies despite the lack of existing reports in the literature. PGT-M for monogenic PKD, like other forms of assisted reproductive technology, raises important ethical questions. When considering PGT-M for kidney diseases, as well as the potential to avoid disease in future generations, there are regulatory and ethical considerations. These include limited government regulation and unstandardized consent processes, potential technical errors, high cost and equity concerns, risks associated with pregnancy for mothers with kidney disease, and the impact on all involved in the process, including the children who were made possible with this technology.

The Clinical Utility of Genetic Testing in the Diagnosis and Management of Adults with Chronic Kidney Disease.

SIGNIFICANCE STATEMENT: Accurate diagnosis of a patient's underlying cause of CKD can influence management and ultimately overall health. The single-arm, interventional, prospective Renasight Clinical Application, Review, and Evaluation study assessed the utility of genetic testing with a 385 gene kidney disease panel on the diagnosis and management of 1623 patients with CKD. Among 20.8% of patients who had positive genetic findings, half resulted in a new or reclassified diagnosis. In addition, a change in management because of genetic testing was reported for 90.7% of patients with positive findings, including treatment changes in 32.9%. These findings demonstrate that genetic testing has a significant effect on both CKD diagnosis and management. BACKGROUND: Genetic testing in CKD has recently been shown to have diagnostic utility with many predicted implications for clinical management, but its effect on management has not been prospectively evaluated. METHODS: Renasight Clinical Application, Review, and Evaluation RenaCARE (ClinicalTrials.gov NCT05846113 ) is a single-arm, interventional, prospective, multicenter study that evaluated the utility of genetic testing with a broad, 385 gene panel (the Renasight TM test) on the diagnosis and management of adult patients with CKD recruited from 31 US-based community and academic medical centers. Patient medical history and clinical CKD diagnosis were collected at enrollment. Physician responses to questionnaires regarding patient disease categorization and management were collected before genetic testing and 1 month after the return of test results. Changes in CKD diagnosis and management after genetic testing were assessed. RESULTS: Of 1623 patients with CKD in 13 predefined clinical disease categories (ages, 18-96; median, 55 years), 20.8% ( n =338) had positive genetic findings spanning 54 genes. Positive genetic findings provided a new diagnosis or reclassified a prior diagnosis in 48.8% of those patients. Physicians reported that genetic results altered the management of 90.7% of patients with a positive genetic finding, including changes in treatment plan, which were reported in 32.9% of these patients. CONCLUSIONS: Genetic testing with a CKD-focused 385 gene panel substantially refined clinical diagnoses and had widespread implications for clinical management, including appropriate treatment strategies. These data support the utility of broader integration of panels of genetic tests into the clinical care paradigm for patients with CKD. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: ClinicalTrials.gov, NCT05846113 .

Utility of new image-derived biomarkers for autosomal dominant polycystic kidney disease prognosis using automated instance cyst segmentation.

New image-derived biomarkers for patients affected by autosomal dominant polycystic kidney disease are needed to improve current clinical management. The measurement of total kidney volume (TKV) provides critical information for clinicians to drive care decisions. However, patients with similar TKV may present with very different phenotypes, often requiring subjective decisions based on other factors (e.g., appearance of healthy kidney parenchyma, a few cysts contributing significantly to overall TKV, etc.). In this study, we describe a new technique to individually segment cysts and quantify biometric parameters including cyst volume, cyst number, parenchyma volume, and cyst parenchyma surface area. Using data from the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) study the utility of these new parameters was explored, both quantitatively as well as visually. Total cyst number and cyst parenchyma surface area showed superior prediction of the slope of estimated glomerular filtration rate decline, kidney failure and chronic kidney disease stages 3A, 3B, and 4, compared to TKV. In addition, presentations such as a few large cysts contributing significantly to overall kidney volume were shown to be much better stratified in terms of outcome predictions. Thus, these new image biomarkers, which can be obtained automatically, will have great utility in future studies and clinical care for patients affected by autosomal dominant polycystic kidney disease.

Congenital Heart Disease in Adults with Autosomal Dominant Polycystic Kidney Disease.

INTRODUCTION: Autosomal dominant polycystic kidney disease (ADPKD) is caused mainly by pathogenic variants in PKD1 or PKD2 encoding the polycystin-1 and -2 proteins. Polycystins have shown to have an essential role in cardiac development and function in animal models. In the current study, we describe the clinical association between ADPKD and congenital heart disease (CHD). METHODS: Medical records from Mayo Clinic were queried for all patients with confirmed ADPKD and CHD between 1993 and 2020. CHD was categorized into left-to-right shunt, obstructive, and complex lesions. Patent foramen ovale, mitral valve prolapse, and bicuspid aortic valve anomalies were excluded. RESULTS: Twenty-five out of 1,359 (1.84%) ADPKD patients were identified to have CHD. Of these, 84% were Caucasians and 44% were males. The median (Q1-Q3) age (years) at CHD diagnosis was 12.0 (2.0-43.5). Fourteen patients (56%) had left-to-right shunt lesions, 6 (24%) had obstructive lesions and 5 (20%) complex lesions. Seventeen patients (68%) had their defects surgically corrected at a median age (Q1-Q3) of 5.5 (2.0-24.7). Among 13 patients with available genetic testing, 12 (92.3%) had PKD1 pathogenic variants, and none had PKD2. The median (Q1-Q3) age at last follow-up visit was 47.0 (32.0-62.0) and median (Q1-Q3) eGFR was 35.8 (11.4-79.0) mL/min/1.73 m2. Three patients (12%) died; all of them had left-to-right shunt lesions. DISCUSSION/CONCLUSION: We observed a higher CHD frequency in ADPKD than the general population (1.84 vs. 0.4%). While only PKD1 pathogenic variants were identified in this cohort, further studies are needed to confirm this novel finding and understand the role of polycystins in the development of the heart and vessels.

Assessing Risk of Rapid Progression in Autosomal Dominant Polycystic Kidney Disease and Special Considerations for Disease-Modifying Therapy.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited cause of kidney failure, accounting for 5%-10% of cases. Predicting which patients with ADPKD will progress rapidly to kidney failure is critical to assess the risk-benefit ratio of any intervention and to consider early initiation of long-term kidney protective measures that will maximize the cumulative benefit of slowing disease progression. Surrogate prognostic biomarkers are required to predict future decline in kidney function. Clinical, genetic, environmental, epigenetic, and radiologic factors have been studied as predictors of progression to kidney failure in ADPKD. A complex interaction of these prognostic factors determines the number of kidney cysts and their growth rates, which affect total kidney volume (TKV). Age-adjusted TKV, represented by the Mayo imaging classification, estimates each patient's unique rate of kidney growth and provides the most individualized approach available clinically so far. Tolvaptan has been approved to slow disease progression in patients at risk of rapidly progressive disease. Several other disease-modifying treatments are being studied in clinical trials. Selection criteria for patients at risk of rapid progression vary widely among countries and are based on a combination of age, baseline glomerular filtration rate (GFR), GFR slope, baseline TKV, and TKV rate of growth. This review details the approach in assessing the risk of disease progression in ADPKD and identifying patients who would benefit from long-term therapy with disease-modifying agents.

Clinical spectrum, prognosis and estimated prevalence of DNAJB11-kidney disease.

Monoallelic mutations of DNAJB11 were recently described in seven pedigrees with atypical clinical presentations of autosomal dominant polycystic kidney disease. DNAJB11 encodes one of the main cofactors of the endoplasmic reticulum chaperon BiP, a heat-shock protein required for efficient protein folding and trafficking. Here we conducted an international collaborative study to better characterize the DNAJB11-associated phenotype. Thirteen different loss-of-function variants were identified in 20 new pedigrees (54 affected individuals) by targeted next-generation sequencing, whole-exome sequencing or whole-genome sequencing. Amongst the 77 patients (27 pedigrees) now in total reported, 32 reached end stage kidney disease (range, 55-89 years, median age 75); without a significant difference between males and females. While a majority of patients presented with non-enlarged polycystic kidneys, renal cysts were inconsistently identified in patients under age 45. Vascular phenotypes, including intracranial aneurysms, dilatation of the thoracic aorta and dissection of a carotid artery were present in four pedigrees. We accessed Genomics England 100,000 genomes project data, and identified pathogenic variants of DNAJB11 in nine of 3934 probands with various kidney and urinary tract disorders. The clinical diagnosis was cystic kidney disease for eight probands and nephrocalcinosis for one proband. No additional pathogenic variants likely explaining the kidney disease were identified. Using the publicly available GnomAD database, DNAJB11 genetic prevalence was calculated at 0.85/10.000 individuals. Thus, establishing a precise diagnosis in atypical cystic or interstitial kidney disease is crucial, with important implications in terms of follow-up, genetic counseling, prognostic evaluation, therapeutic management, and for selection of living kidney donors.

Effect of a Vasopressin V2 Receptor Antagonist on Polycystic Kidney Disease Development in a Rat Model.

BACKGROUND: Vasopressin V2 receptor inhibition is a clinically validated mechanism of action in the treatment of autosomal dominant polycystic kidney disease (ADPKD). In this study, the effect of lixivaptan, a potent, selective vasopressin V2 antagonist, was evaluated in PCK rats, a validated animal model of PKD. METHODS: Four-week old PCK rats were fed rodent chow with 0.5% lixivaptan (low dose) or 1% lixivaptan (high dose), or chow only (control) for 8 weeks. Urine output was measured at weeks 7 and 10 of age. Animals were killed at 12 weeks of age; kidneys and livers were collected, weighted, and analyzed for cyclic adenosine 3',5'-monophosphate (cAMP) levels and cystic burden and fibrosis; serum creatinine and sodium were measured. RESULTS: Consistent with the development of a polycystic kidney phenotype, control PCK rats showed enlarged kidneys, extensive cyst formation, and early signs of serum creatinine elevation at 12 weeks of age. Compared to controls, PCK rats treated with low-dose lixivaptan showed a 26% reduction in % kidney weight/body weight (p < 0.01); a 54% reduction in kidney cystic score (p < 0.001), a histomorphometric measure of cystic burden; a 23% reduction in kidney cAMP levels (p < 0.05), a biochemical marker of disease; and a 13% reduction in plasma creatinine (p < 0.001), indicating preserved renal function. These reductions were associated with 3-fold increases in 24-h urine output, demonstrating the potent aquaretic effect of lixivaptan. The fact that the high dose was less efficacious than the low dose is discussed. CONCLUSIONS: These results provide the first evidence of the potential utility of lixivaptan for the treatment of ADPKD.

Outcomes of patients with autosomal-dominant polycystic kidney disease on peritoneal dialysis: A meta-analysis.

BACKGROUND: Complications related to peritoneal dialysis (PD) in patients with autosomal-dominant polycystic kidney disease (ADPKD), including intraperitoneal rupture of renal cyst, hernia, membrane failure and peritonitis, have been reported. However, long-term clinical outcomes of ADPKD patients on PD remain unclear. We performed this meta-analysis to assess the risks of death, technique failure and peritonitis in ADPKD patients on PD. METHODS: A systematic review was conducted using MEDLINE, EMBASE and Cochrane databases from inception to October 2017 to identify studies that evaluated the outcomes of ADPKD patients on PD, including the risks of death, technique failure and peritonitis. Non-ADPKD patients on PD were used as controls. Effect estimates from the individual study were extracted and combined using the random-effect, generic inverse variance method of DerSimonian and Laird. RESULTS: Twelve cohort studies with a total of 14 673 patients on PD (931 ADPKD and 13 742 non-ADPKD patients) were enrolled. Compared with non-ADPKD status, ADPKD was associated with significantly decreased mortality risk with pooled odds ratio (OR) of 0.68 (95% confidence interval (CI), 0.53-0.86; I2 = 0). There were no associations of ADPKD with the risks of technique failure of PD and peritonitis with pooled OR of 0.93 (95% CI, 0.79-1.10; I2 = 0) and 0.88 (95% CI, 0.75-1.05; I2 = 0), respectively. We found no publication bias as assessed by Egger's regression asymmetry test, with P = 0.90, 0.28 and 0.60 for the risks of mortality, technique failure and peritonitis in ADPKD patients on PD, respectively. CONCLUSION: Compared with non-ADPKD patients on PD, our study demonstrates that ADPKD patients on PD have 0.68-fold decreased mortality risk. There are no associations of ADPKD status with the risks of technique failure or peritonitis.

A Practical Guide for Treatment of Rapidly Progressive ADPKD with Tolvaptan.

In the past, the treatment of autosomal dominant polycystic kidney disease (ADPKD) has been limited to the management of its symptoms and complications. Recently, the US Food and Drug Administration (FDA) approved tolvaptan as the first drug treatment to slow kidney function decline in adults at risk of rapidly progressing ADPKD. Full prescribing information approved by the FDA provides helpful guidelines but does not address practical questions that are being raised by nephrologists, internists, and general practitioners taking care of patients with ADPKD, and by the patients themselves. In this review, we provide practical guidance and discuss steps that require consideration before and after prescribing tolvaptan to patients with ADPKD to ensure that this treatment is implemented safely and effectively. These steps include confirmation of diagnosis; identification of rapidly progressive disease; implementation of basic renal protective measures; counseling of patients on potential benefits and harms; exclusions to use; education of patients on aquaresis and its expected consequences; initiation, titration, and optimization of tolvaptan treatment; prevention of aquaresis-related complications; evaluation and management of liver enzyme elevations; and monitoring of treatment efficacy. Our recommendations are made on the basis of published evidence and our collective experiences during the randomized, clinical trials and open-label extension studies of tolvaptan in ADPKD.

The Value of Genetic Testing in Polycystic Kidney Diseases Illustrated by a Family With PKD2 and COL4A1 Mutations.

The diagnosis of autosomal dominant polycystic kidney disease (ADPKD) relies on imaging criteria in the setting of a positive familial history. Molecular analysis, seldom used in clinical practice, identifies a causative mutation in >90% of cases in the genes PKD1, PKD2, or rarely GANAB. We report the clinical and genetic dissection of a 7-generation pedigree, resulting in the diagnosis of 2 different cystic disorders. Using targeted next-generation sequencing of 65 candidate genes in a patient with an ADPKD-like phenotype who lacked the familial PKD2 mutation, we identified a COL4A1 mutation (p.Gln247*) and made the diagnosis of HANAC (hereditary angiopathy with nephropathy, aneurysms, and muscle cramps) syndrome. While 4 individuals had ADPKD-PKD2, various COL4A1-related phenotypes were identified in 5 patients, and 3 individuals with likely digenic PKD2/COL4A1 disease reached end-stage renal disease at around 50 years of age, significantly earlier than observed for either monogenic disorder. Thus, using targeted next-generation sequencing as part of the diagnostic approach in patients with cystic diseases provides differential diagnoses and identifies factors underlying disease variability. As specific therapies are rapidly developing for ADPKD, a precise etiologic diagnosis should be paramount for inclusion in therapeutic trials and optimal patient management.

The regulatory 1α subunit of protein kinase A modulates renal cystogenesis.

The failure of the polycystins (PCs) to function in primary cilia is thought to be responsible for autosomal dominant polycystic kidney disease (ADPKD). Primary cilia integrate multiple cellular signaling pathways, including calcium, cAMP, Wnt, and Hedgehog, which control cell proliferation and differentiation. It has been proposed that mutated PCs result in reduced intracellular calcium, which in turn upregulates cAMP, protein kinase A (PKA) signaling, and subsequently other proliferative signaling pathways. However, the role of PKA in ADPKD has not been directly ascertained in vivo, although the expression of the main regulatory subunit of PKA in cilia and other compartments (PKA-RIα, encoded by PRKAR1A) is increased in a mouse model orthologous to ADPKD. Therefore, we generated a kidney-specific knockout of Prkar1a to examine the consequences of constitutive upregulation of PKA on wild-type and Pkd1 hypomorphic (Pkd1RC) backgrounds. Kidney-specific loss of Prkar1a induced renal cystic disease and markedly aggravated cystogenesis in the Pkd1RC models. In both settings, it was accompanied by upregulation of Src, Ras, MAPK/ERK, mTOR, CREB, STAT3, Pax2 and Wnt signaling. On the other hand, Gli3 repressor activity was enhanced, possibly contributing to hydronephrosis and impaired glomerulogenesis in some animals. To assess the relevance of these observations in humans we looked for and found evidence for kidney and liver cystic phenotypes in the Carney complex, a tumoral syndrome caused by mutations in PRKAR1A These observations expand our understanding of the pathogenesis of ADPKD and demonstrate the importance of PRKAR1A highlighting PKA as a therapeutic target in ADPKD.

Effect of genotype on the severity and volume progression of polycystic liver disease in autosomal dominant polycystic kidney disease.

BACKGROUND: The autosomal dominant polycystic kidney disease (APDKD) genotype influences renal phenotype severity but its effect on polycystic liver disease (PLD) is unknown. Here we analyzed the influence of genotype on liver phenotype severity. METHODS: Clinical data were retrieved from electronic records of patients who were mutation screened with the available liver imaging (n = 434). Liver volumes were measured by stereology (axial or coronal images) and adjusted to height (HtLV). RESULTS: Among the patients included, 221 (50.9%) had truncating PKD1 (PKD1-T), 141 (32.5%) nontruncating PKD1 (PKD1-NT) and 72 (16.6%) PKD2 mutations. Compared with PKD1-NT and PKD2, patients with PKD1-T had greater height-adjusted total kidney volumes (799 versus 610 and 549 mL/m; P < 0.001). HtLV was not different (1042, 1095 and 1058 mL/m; P = 0.64) between the three groups, but females had greater HtLVs compared with males (1114 versus 1015 mL/m; P < 0.001). Annualized median liver growth rates were 1.68, 1.5 and 1.24% for PKD1-T, PKD1-NT and PKD2 mutations, respectively (P = 0.49), and remained unaffected by the ADPKD genotype when adjusted for age, gender and baseline HtLV. Females <48 years of age had higher annualized growth rates compared with those who were older (2.65 versus 0.09%; P < 0.001). After age 48 years, 58% of females with severe PLD had regression of HtLV, while HtLV continued to increase in males. CONCLUSIONS: In contrast to the renal phenotype, the ADPKD genotype was not associated with the severity or growth rate of PLD in ADKPD patients. This finding, along with gender influence, indicates that modifiers beyond the disease gene significantly influence the liver phenotype.

Volume regression of native polycystic kidneys after renal transplantation.

BACKGROUND: The natural course of native kidneys after renal transplantation (RT) or dialysis in patients with autosomal dominant polycystic kidney disease (ADPKD) remains poorly understood. METHODS: We measured the total volumes of native kidneys and liver in 78 and 68 ADPKD patients, respectively, who had pre-transplant (within 2 years) and at least one post-transplant computed tomography (CT)/magnetic resonance imaging (MRI); in 40 patients with at least two post-transplant but no pre-transplant CT/MRIs; in 9 patients on chronic hemodialysis with at least one CT/MRI before and after beginning dialysis; and in 5 patients who had no image before and more than one image after dialysis. The last imaging was used in patients with multiple studies. RESULTS: Mean total kidney volume (TKV) ( ± SD) prior to transplantation was 3187 ± 1779 mL in the 78 patients who had imaging before and after transplantation and decreased by 20.2, 28.6, 38.3 and 45.8% after 0.5-1 (mean 0.7), 1-3 (1.8), 3-10 (5.7) and >10 (12.6) years, respectively. In the multivariable analysis, time on dialysis prior to RT and time from baseline to transplantation were negatively associated with reduction in TKV, whereas estimated glomerular filtration rate (eGFR) after transplantation and time from transplantation were positively associated with percent reduction in TKV. In the 40 patients with imaging only after transplantation, TKV decreased by 3.2 ± 16.3% between 7.2 ± 6.0 and 11.2 ± 6.8 years after transplantation (P < 0.001). TKV was 11.2 ± 35.6% higher (P = NS) after a follow-up of 3.4 ± 2.0 years in the 9 patients with imaging before and after initiation of hemodialysis and 3.4 ± 40.2% lower (P = NS) in the 5 patients with imaging between 2.0 ± 2.1 and 3.5 ± 3.6 years after initiation of hemodialysis. In the 68 patients with liver measurements, volume increased by 5.8 ± 17.9% between baseline and follow-up at 3.7 ± 3.8 years after transplantation (P = 0.009). CONCLUSIONS: TKV of native polycystic kidneys decreases substantially after RT. The reduction occurs mainly during the early post-transplantation period and more slowly thereafter.