Autosomal dominant polycystic kidney disease

Safety and efficacy of tolvaptan in real‑world Japanese patients with autosomal dominant polycystic kidney disease: final results of SLOW‑PKD surveillance

BACKGROUND

Tolvaptan, a vasopressin type 2 receptor antagonist, has been used to treat autosomal dominant polycystic kidney disease in Japan since 2014.

METHODS

This long-term, real-world, post-marketing surveillance (PMS) was conducted in Japan from March 2014 to March 2022. Safety was assessed based on adverse drug reactions (ADRs). For efficacy, changes in the slope of total kidney volume (TKV) and estimated glomerular filtration rate (eGFR) were assessed before and during the administration of tolvaptan.

RESULTS

A total of 1676 patients were enrolled, with mean TKV (n = 1000) of 2149 ± 1339 mL and eGFR (n = 1641) of 44.4 ± 21.7 mL/min/1.73 m2. Frequent ADRs were hepatic function abnormal (9.6%), hyperuricaemia (8.3%), and thirst (8.1%). Most of the increased alanine aminotransferase exceeding 3 times the upper limit of the reference level occurred from 3  to  14 months after the start of treatment, but about 20% was observed after 15 months. There was no increase in ADRs over 36 months, suggesting that no other safety concerns need to be monitored during administration over 3-7 years. The mean slope of the estimated TKV increase before and during tolvaptan treatment was 6.58 and 3.71%/year, respectively (P = 0.0020). The mean slope of eGFR decline was - 3.63 and - 3.26 mL/min/1.73 m2/year, respectively (P = 0.2728).

CONCLUSION

There were no major problems with the safety of tolvaptan treatment, and efficacy in limiting TKV increase in this PMS was comparable to the previous, pivotal randomized control trials. Trial registration ClinicalTrials.gov; NCT02847624.

Characteristics of patients with autosomal polycystic kidney disease reaching kidney failure by age 40

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) demonstrates broad genetic and phenotypic variability, with kidney failure (KF) occurring across a wide age spectrum. Despite several predictor tools, there remains a need to identify factors associated with rapid disease progression. This study describes the phenotypic characteristics of a multicentric cohort experiencing early-onset KF by age 40.

METHODS

This retrospective, multicenter cohort study analyzed longitudinal data of rapidly progressive ADPKD patients (n = 199). The prevalence of established risk factors was compared to nine existing ADPKD cohorts (ntotal = 6782) with KF after 40 years of age. We examined the longitudinal impact of early hypertension and urological events on the risk of developing KF.

RESULTS

The median age at ADPKD diagnosis was 22.3 years (IQR, 16.5-28.6) and median age of KF was 35.6 years (31.7-38.0). Hypertension was observed in 68.1% of cases, with early-onset hypertension being more common among those with accelerated progression towards KF. Urological events were present in 60.1% of cases, with a high burden of gross hematuria (30.4%). Existing ADPKD cohorts had a mean age of 45.5 years, with weighted prevalences of hypertension (71.1%), kidney stones (22.4%), hematuria (22.9%), and urinary tract infections (22.8%). Extrarenal manifestations were less prevalent compared to other ADPKD cohorts.

CONCLUSION

This study outlines a cohort of ADPKD patients with accelerated disease progression, reaching KF before age 40. Hypertension and urological events were highly prevalent at a young age, emphasizing the importance of early and regular blood pressure monitoring.

Association Between Body Mass Index and Age at End-Stage Renal Disease in Patients With Autosomal Dominant Polycystic Kidney Disease in the United States and Japan

OBJECTIVE

To evaluate the association between body mass index (BMI) and age at initiation of renal replacement therapy (RRT) of patients with autosomal dominant polycystic kidney disease (ADPKD) in the United States and Japan, 2 populations with different dietary habits and BMIs.

METHODS

We performed a cross-sectional analysis using data from the United States Renal Data System (USRDS) and the Japanese Society for Dialysis Therapy Renal Data Registry (JRDR) to compare age, BMI, and other clinical characteristics of the patients who initiated RRT in the 2 countries between January 1, 2006, and December 31, 2007.

RESULTS

This study included 3556 patients (1877 men and 1679 women) with RRT from the USRDS (n=2491) and JRDR (n=1065). Mean ages at RRT were 56.6±13.1 years in the United States and 61.6±12.5 years in Japan (P<.001). The BMI was 28.2±7.1 kg/m2 in the USRDS and 22.0±3.3 kg/m2 in the JRDR (P<.001). Japanese participants were the oldest, followed in descending order by Asian Americans, White Americans, and African Americans. Japanese participants had the lowest BMI, followed in ascending order by Asian Americans, White Americans, and African Americans. Univariable and adjusted analyses found that BMI was significantly and inversely associated with age at RRT, both overall and separately in American and Japanese populations.

CONCLUSION

Lower BMI is significantly associated with older age at RRT in patients with ADPKD in both the United States and Japan. Japanese individuals had lower BMI and were older than US people of various ethnicities. Lower BMI in Japan is likely to be associated with a slower progression of ADPKD.

Percutaneous renal denervation in the management of kidney-related pain syndromes: a case series

INTRODUCTION

Positive effects on pain reduction following renal denervation (RDN) have been described in patients with kidney-related pain syndromes, yet data on the safety and efficacy of redo RDN procedures are limited.

METHODS

Consecutive patients with a history of chronic loin pain, hypertension and preserved renal function (eGFR ≥40 ml/min) scheduled for RDN were included. Changes in perceived pain, opioid and antihypertensive medication use, and blood pressure were prospectively assessed 3 months after each procedure.

RESULTS

Two patients presented with a history of Autosomal Dominant Polycystic Kidney Disease (n = 2) and one with Loin Pain Hematuria Syndrome (n = 1). Two patients underwent a redo RDN. After the initial procedures, a reduction in perceived pain, along with a 50 % and 75 % reduction in the daily dosage of opioids, was observed in two patients. One patient showed no reduction in perceived pain or opioid use and underwent a redo procedure after 3 years, again with no reduction in perceived pain or opioid use. One patient who initially responded returned at 2 years with recurrent symptoms and underwent a redo procedure. After 3 months, a significant improvement in pain and opioid use was observed. Mean 24-hour systolic blood pressure decreased in all patients and after each procedure with a mean decrease of 12 mmHg. No adverse events were observed.

CONCLUSION

In hypertensive patients with kidney-related pain syndromes, percutaneous RDN may be considered as an alternative treatment option to reduce pain severity and improve blood pressure control. Redo procedures may be considered in patients with recurrent symptoms after an initial response.

Ketogenic diets in chronic kidney disease patients: a review for skeptics by skeptics

Over the last few decades, there has been growing interest in the use of ketogenic diets, mainly as a weight loss strategy. Obesity and diabetes are major risk factors for kidney disease, and obese patients with chronic kidney disease (CKD) are potential candidates for weight reducing diets, among them ketogenic diets. Of further relevance to nephrology, a limited number of recent studies suggests a favorable effect of ketogenic diets in patients affected by autosomal dominant polycystic kidney disease (ADPKD). However, concerns remain about safety in patients with CKD, particularly in the long term and in those with poor residual kidney function. The confusion surrounding the definition of ketogenic diets adds to these concerns. The aim of this review is to summarize information on the main types of ketogenic diets used in daily practice and to discuss the options for their implementation in CKD patients, limiting ultra-processed or industrial preparations.Although further studies are needed to identify the profile of CKD patients who may benefit from the implementation of ketogenic diets to treat obesity or slow the progression of ADPKD, and to assess short- and long-term safety and adherence, the available data appear promising. This critical review is intended to stimulate further research.

Autosomal Dominant Polycystic Kidney Disease-Related Multifocal Renal Cell Carcinoma: A Narrative Iconographic Review

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inheritable disease of cystic degeneration in the kidney. ADPKD is a significant cause of end-stage renal disease (ESRD). Autosomal Dominant Polycystic Liver Disease (ADPLD) results in substantial PLD with minimal PKD. Currently, there are eight genes which have been associated with ADPKD (PKD1 and PKD2), ADPLD (PRKCSH, SEC63, LRP5, ALG8, and SEC61B), or both (GANAB). The severity of ADPKD can show an extremely broad range, but the evolution to ESRD is doubtless unavoidable. In some patients, carcinogenesis develops with inflammation as a potential promoting factor. In this chapter, we illustrate the severity of ADPKD and the fate to develop renal cell carcinoma (RCC).

Time-restricted eating and autosomal dominant polycystic kidney disease: a pilot, randomized clinical trial

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most commonly inherited progressive kidney disease. Time-restricted eating (TRE) is a fasting regimen that restricts eating to a particular window (typically 8 hours/day), which could slow cyst growth based on preclinical models.

Methods

A 12-month, randomized, controlled, behavioral dietary intervention compared TRE with a control group given healthy eating advice without TRE (HE), without caloric restriction. Participants underwent baseline and 12-month measurements, including adherence (percentage of participants adhering to the 8-hour window; primary outcome), and MRI to determine height-adjusted total kidney volume (htTKV) and adiposity.

Results

Twenty-nine participants (23 females, mean standard ± deviation 48 ± 9 years) with a body mass index of 31.1±5 kg/m2 were randomized to TRE (n = 14) or HE (n = 15). Of the total participants, 71% (n = 10) of TRE and 87% (n = 13) of HE participants completed the intervention. The eating window was 9.6 ± 3.6 hours for TRE (60% achieving the 8-hour window) and 12.0 ± 2.0 for HE groups (P = .07). At month 12, both groups lost modest weight (-2.4 ± 6.4% and -3.6 ± 5.4% in the TRE and HE groups, respectively). Annual change in htTKV was 3.0 ± 8.5% and 4.6 ± 8.8% in the TRE and HE groups, respectively. Both change in weight (r = 0.67, P < .01) and change in visceral adiposity (r = 0.54, P < .01) were positively correlated with change in htTKV.

Conclusion

Both the TRE and HE group lost modest weight at 12 months. The targeted TRE adherence of ≥75% of participants was not achieved. Weight and adiposity loss may be more important drivers of kidney growth than the timing of eating.

Management of Anterior Mediastinal Hodgkin's Lymphoma in Polycystic Kidney Disease: A Case Report

This case report presents a 33-year-old male with polycystic kidney disease (PKD) who presented with superior vena cava syndrome due to an anterior mediastinal mass. Imaging and pathology confirmed a Hodgkin's lymphoma of nodular sclerosis subtype of the mediastinum. Despite chronic kidney disease, prioritization to treat the Hodgkin's lymphoma was taken with careful monitoring of renal function. Renal function declined throughout chemotherapy, necessitating modification to the chemotherapy regimen, but not requiring dialysis. Three years following remission from lymphoma, renal function continued to decline, prompting renal transplant and bilateral nephrectomy. This case highlights considerations in treatment for oncological disease with pre-existing decreased kidney function.

Overweight Status, Obesity, and Progression to ESKD in Patients with Autosomal Dominant Polycystic Kidney Disease

Key Points

Higher body mass index increased risk of progression to ESKD in patients with early-stage autosomal dominant polycystic kidney disease. Higher body mass index did not increase the risk of progression to ESKD in patients with late-stage autosomal dominant polycystic kidney disease.

Background

Prior research has linked higher body mass index (BMI) and greater visceral adiposity with more rapid progression of early-stage autosomal dominant polycystic kidney disease (ADPKD). We now evaluate the association between overweight and obesity in patients with early- and late-stage ADPKD with progression to ESKD.

Methods

Participants with early-stage ADPKD (study A; N =556; eGFR: 91±17 ml/min per 1.73 m2) and late-stage ADPKD (study B; N =483; eGFR: 48±12 ml/min per 1.73 m2) who participated in the Halt Progression of Polycystic Kidney Disease (HALT) polycystic kidney disease trials were categorized by BMI as normal weight (18.5–24.9 kg/m2; ref; n =357), overweight (25.0–29.9 kg/m2; n =384), or obese (≥30 kg/m2; n =298). Kaplan–Meier survival analysis and multivariate Cox proportional hazard models were used to determine the association of baseline BMI as a continuous and categorical variable with risk of ESKD (according to the United States Renal Data System) over a median (interquartile range) follow-up period of 12.2 (7.5–13.3; study A) and 7.3 (5.1–11.7; study B) years (primary outcome). All-cause mortality (National Death Index) was also considered as a competing risk (Fine and Gray method).

Results

The number of ESKD events was greater with overweight (n =24) and obesity (n =23) in HALT study A versus normal weight (n =12) but not in HALT study B (normal weight: n =89, overweight: n =102, obese: n =92). In fully adjusted models, higher BMI was associated with risk of progression to ESKD in study A (hazard ratio [HR (95% confidence interval)], 1.09 [1.03 to 1.15] per unit higher BMI) but not in study B (HR, 0.98 [0.96 to 1.00]). Obesity was associated with increased risk of ESKD (HR, 2.71 [1.22 to 6.02] versus normal weight) in study A only. Results were similar when considering death as a competing risk.

Conclusions

Higher BMI, particularly obesity, increased the risk of progression to ESKD in patients with early-stage ADPKD but not in those with late-stage ADPKD.

PKD1 mutation perturbs morphogenesis in tubular epithelial organoids derived from human pluripotent stem cells

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal genetic disease, with most patients carrying mutations in PKD1. The main feature is the formation of bilateral renal cysts, leading to end stage renal failure in a significant proportion of those affected. Despite recent advances made in understanding ADPKD, there are currently no effective curative therapies. The emergence of human induced pluripotent stem cell (hiPSC)-derived kidney disease models has led to renewed hope that more physiological systems will allow for the development of novel treatments. hiPSC-derived organoid models have been used to recapitulate ADPKD, however they present numerous limitations which remain to be addressed. In the present study, we report an efficient method for generating organoids containing a network of polarised and ciliated epithelial tubules. PKD1 null (PKD1-/-) organoids spontaneously develop dilated tubules, recapitulating early ADPKD cystogenesis. Furthermore, PKD1-/- tubules present primary cilia defects when dilated. Our model could therefore serve as a valuable tool to study early ADPKD cystogenesis and to develop novel therapies.

Genetic and protein structure prediction analyses identify a rare pathogenic PKD1 variant causing autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common monogenic kidney disorders. The diagnosis of ADPKD requires imaging findings showing multiple kidney cysts or genetic testing, in cases where a family history is unknown. We report a patient diagnosed with ADPKD based on the identification of a rare PKD1 variant. The patient was a 41-year-old female in whom cysts and calcification in the kidneys were incidentally detected. Whole-exome sequencing identified a rare PKD1 variant (NM_001009944.3: c.11557G > A/p.E3853K). Protein structure prediction of the PKD1-PKD2 complex showed that the variant may be pathogenic, leading to the diagnosis of autosomal dominant polycystic kidney disease. A detailed family history revealed that her relatives also had ADPKD, further supporting the diagnosis of ADPKD. Comprehensive genetic analysis and protein structure prediction led to the diagnosis of ADPKD and the identification of rare causative genes. These methods are useful for diagnosing hereditary kidney diseases of unknown etiologies.

BICC1 Interacts with PKD1 and PKD2 to Drive Cystogenesis in ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is primarily of adult-onset and caused by pathogenic variants in PKD1 or PKD2 . Yet, disease expression is highly variable and includes very early-onset PKD presentations in utero or infancy. In animal models, the RNA-binding molecule Bicc1 has been shown to play a crucial role in the pathogenesis of PKD. To study the interaction between BICC1, PKD1 and PKD2 we combined biochemical approaches, knockout studies in mice and Xenopus, genetic engineered human kidney cells as well as genetic association studies in a large ADPKD cohort. We first demonstrated that BICC1 physically binds to the proteins Polycystin-1 and -2 encoded by PKD1 and PKD2 via distinct protein domains. Furthermore, PKD was aggravated in loss-of-function studies in Xenopus and mouse models resulting in more severe disease when Bicc1 was depleted in conjunction with Pkd1 or Pkd2 . Finally, in a large human patient cohort, we identified a sibling pair with a homozygous BICC1 variant and patients with very early onset PKD (VEO-PKD) that exhibited compound heterozygosity of BICC1 in conjunction with PKD1 and PKD2 variants. Genome editing demonstrated that these BICC1 variants were hypomorphic in nature and impacted disease-relevant signaling pathways. These findings support the hypothesis that BICC1 cooperates functionally with PKD1 and PKD2 , and that BICC1 variants may aggravate PKD severity highlighting RNA metabolism as an important new concept for disease modification in ADPKD.

Integrated Use of Autosomal Dominant Polycystic Kidney Disease Prediction Tools for Risk Prognostication

Key Points

The Mayo clinic imaging classification and the predicting renal outcome in polycystic kidney disease score are used to assess the risk of progression to kidney failure in autosomal dominant polycystic kidney disease. Mayo imaging classification and predicting renal outcome in polycystic kidney disease show little concordance; combined use increased the ability to identify rapid progression especially among intermediate risk patients. Accurate risk prediction is key for determining indication for specific treatment.

Background

Autosomal dominant polycystic kidney disease is the most common genetic cause of kidney failure. Specific treatment is indicated on observed or predicted rapid progression. For the latter, risk stratification tools have been developed independently based on either total kidney volume or genotyping as well as clinical variables. This study aimed to improve risk prediction by combining both imaging and clinical-genetic scores.

Methods

We conducted a retrospective multicenter cohort study of 468 patients diagnosed with autosomal dominant polycystic kidney disease. Clinical, imaging, and genetic data were analyzed for risk prediction. We defined rapid disease progression as an eGFR slope ≥3 ml/min per 1.73 m2 per year over 2 years, Mayo imaging classification (MIC) 1D–1E, or a predicting renal outcome in polycystic kidney disease (PROPKD) score of ≥7 points. Using MIC, PROPKD, and rare exome variant ensemble learner scores, several combined models were designed to develop a new classification with improved risk stratification. Primary endpoints were the development of advanced CKD stages G4–G5, longitudinal changes in eGFR, and clinical variables such as hypertension or urological events. Statistically, logistic regression, survival, receiver operating characteristic analyses, linear mixed models, and Cox proportional hazards models were used.

Results

PKD1 -genotype (P < 0.001), MIC class 1E (P < 0.001), early-onset hypertension (P < 0.001), and early-onset urological events (P = 0.003) correlated best with rapid progression in multivariable analysis. While the MIC showed satisfactory specificity (77%), the PROPKD was more sensitive (59%). Among individuals with an intermediate risk in one of the scores, integration of the other score (combined scoring) allowed for more accurate stratification.

Conclusions

The combined use of both risk scores was associated with higher ability to identify rapid progressors and resulted in a better stratification, notably among intermediate risk patients.

Spot Versus 24-Hour Urine Osmolality Measurement in Autosomal Dominant Polycystic Kidney Disease: A Diagnostic Test Study

Rationale & Objective

Arginine vasopressin (AVP) is an established driver of cyst growth in autosomal dominant polycystic kidney disease (ADPKD). Urine osmolality (osm) measures are surrogate markers of AVP activity. Both 24-hour and spot urine samples are used as indicators of AVP suppression. The agreement between these 2 measurements remains unclear.

Study Design

A retrospective cohort study.

Setting & Study Population

Three hundred and forty-nine patients with ADPKD with 839 urine samples from a tertiary care center.

Selection Criteria for Study

Patients with ADPKD with records of spot and 24-hour urine measurements.

Data Extraction

Consecutive patients' data from January 2018 to March 2023 were extracted from the quality assurance database of The Ottawa Hospital Cystic Kidney Disease Clinic.

Analytical Approach

Discordance assessed at target urine osmolality of 250 and 270 mmol/kg. Agreement assessed by Bland-Altman plots. The percentage of patients with difference in osmolality between the 2 measures for cutoff points of > 50, > 100, >150, and > 200 mmol/kg was calculated.

Results

The mean 24-hour urine osm was 364 mmol/kg, and the mean spot urine osm was 424 mosm/kg. Mean age of 46 years, 52% females, and 47 (13.5%) were on tolvaptan. Overall, in comparing spot urine osm to 24-hour urine osm, the discordance at 250 and 270 mmol/kg was 24% with poor agreement on Bland-Altman plots. The differences between the 2 measures at varying cutoff points were 53.9% at 50 mmol/kg, 35.8% at 100 mmol/kg, 24.1% at 150 mmol/kg, and 16.1% at 200 mmol/kg. Results were similar when only a single measurement from each patient was used for analysis.

Limitations

Total of 29% of patients did not have concurrent spot urine osmolality and 24-hour urine osmolality. The study was conducted at a single center. Limited number of patients were on tolvaptan.

Conclusions

In adults with ADPKD, important differences exist between the 24-hour urine osmolality and spot urine osmolality that preclude interchangeable use. The method employed may impact clinical decision-making. More research is needed to determine, which urine osm should be used when assessing AVP suppression.

The pathophysiological significance between autosomal dominant polycystic kidney disease and neutrophil gelatinase-associated lipocalin

Autosomal dominant polycystic kidney disease (ADPKD) is the most common form of polycystic kidney disease (PKD) and is a typical adult-onset multisystem disorder. It is a progressive disease characterized by the disruption of renal tubular integrity, involving the modulation of cellular proliferation and apoptosis. Most ADPKD results from a mutation in either the PKD1 or PKD2 gene encoding polycystin-1 and polycystin-2, respectively. With the inconsistent disease course of ADPKD, biomarkers that can predict the treatment efficacy and rapid progression of the disease are needed. Studies have identified neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker for predicting the progression of ADPKD patients. The NGAL protein is expressed at a low level in the kidneys, which helps to regulate iron transport and participates in epithelial differentiation, inflammation, and cell proliferation. NGAL level also increases in serum and urine during renal detrimental conditions such as ischemia and acute and chronic kidney diseases. On the other hand, some studies have also demonstrated that NGAL may act as a tubulogenic factor controlling cell growth and that the upregulation of the Ngal gene hinders tubular cell proliferation, resulting in significantly reduced cyst growth in cellular and murine models of ADPKD. This review attempts to correlate ADPKD and NGAL based on available research findings to evaluate the therapeutic potential of NGAL in ADPKD.

The impact of asymptomatic kidney stones on disease progression in autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a common hereditary disorder leading to end-stage kidney disease due to the progressive formation of renal cysts. Nephrolithiasis is a frequent complication of ADPKD, with a prevalence significantly higher than in the general population. However, its role in disease progression remains underexplored. This study investigates the impact of asymptomatic nephrolithiasis on kidney function decline in ADPKD patients.

METHODS

A retrospective cohort of 195 ADPKD patients was followed at our nephrology clinic. Of these, 85 patients had nephrolithiasis (N+), and 110 did not (N-). Data on demographic characteristics, biochemical parameters, and kidney function were collected. ΔeGFR (change in eGFR over time) served as the primary outcome. Statistical analyses, including correlation and multiple linear regression, were performed to assess the predictors of ΔeGFR.

RESULTS

The N + group exhibited a significantly greater decline in kidney function compared to the N- group (ΔeGFR: 16.53 vs. 12.82 mL/min/1.73 m², p = 0.008). Lower calcium levels were observed in the N + group (p = 0.007), potentially reflecting metabolic abnormalities linked to nephrolithiasis. Nephrolithiasis was independently associated with kidney function decline (B = 3.159, p = 0.038). Follow-up duration was strongly associated with ΔeGFR (p < 0.001). Age showed a trend toward significance but did not reach statistical significance.

CONCLUSION

Asymptomatic nephrolithiasis is associated with accelerated kidney function decline in ADPKD patients. These findings highlight the importance of monitoring kidney stones, even in the absence of symptoms, to mitigate their impact on renal dysfunction.

Tolvaptan safety in autosomal-dominant polycystic kidney disease; a focus on idiosyncratic drug-induced liver injury liabilities

Tolvaptan is a vasopressin V2 receptor antagonist which has proven to be an effective and mostly well-tolerated agent for the treatment of autosomal-dominant polycystic kidney disease. However, its administration is associated with rare but serious idiosyncratic liver injury, which has warranted a black box warning on the drug labels and frequent monitoring of liver blood tests in the clinic. This review outlines mechanistic investigations that have been conducted to date and constructs a working narrative as an explanation for the idiosyncratic drug-induced liver injury (IDILI) events that have occurred thus far. Potential risk factors which may contribute to individual susceptibility to DILI reactions are addressed, and key areas for future investigative/clinical development are highlighted.

MicroRNA and renal fibrosis in autosomal dominant polycystic kidney disease: a longitudinal study

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary kidney disorder that may progress to kidney failure, accounting for 5-10% of all patients with end-stage kidney disease (ESKD). Clinical data, as well as molecular genetics and advanced imaging techniques have provided surrogate prognostic biomarkers to predict rapid decline in kidney function, nonetheless enhanced tools for assessing prognosis for ADPKD are still needed. The aim of this study was to analyze specific microRNAs involved in the pathogenesis of ADPKD and in the development of renal fibrosis, evaluating their potential role as predictors of renal function loss.

METHODS

We evaluated kidney function by estimated glomerular filtration rate (eGFR) in 32 ADPKD patients in different stages of kidney disease at T0 and after a 24-month follow up (T1). Patients were divided into two groups: Rapid disease progression ([RP], n 15) and Non-rapid disease progression ([NRP], n 17), according to the Mayo Clinic classification criteria. At T0, ADPKD patients underwent plasma sampling for quantitative analysis of h-miR-17-5p, h-miR-21-5p and h-miR-199a-5p microRNA expression, using the quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) method and a 3 T magnetic resonance imaging (MRI), using an advanced MRI imaging protocol, for the quantification of total kidney volume (TKV), total perfusion volume (TPV) and total fibrotic volume (TFV).

RESULTS

The expression of h-miR17-5p was higher (p < 0.05) in ADPKD patients with rapid disease progression. h-miR-17-5p, h-miR-21-5p and h-mir-199-5p showed a positive and significant correlation with the eGFR slope (mL/min/1.73 m2/year) (p < 0.05) but not with the eGFR at both T0 and T1. Both total fibrotic volume (cm3) and height-adjusted total fibrotic volume (cm3/m) were positively and significantly correlated to h-miR 21-5p and h-miR 199-5p (p < 0.05), but not to total kidney volume (cm3) and height-adjusted total kidney volume (cm3/m).

CONCLUSIONS

The microRNAs we studied were associated with fibrosis and renal damage, suggesting their possible role as biomarkers able to identify ADPKD patients at high risk of disease progression regardless of the degree of kidney function, and therefore suitable for medical therapy, and may help uncovering new molecular mechanisms underlying cystogenesis.

Melanin-like nanoparticles slow cyst growth in ADPKD by dual inhibition of oxidative stress and CREB

Melanin-like nanoparticles (MNPs) have recently emerged as valuable agents in antioxidant therapy due to their excellent biocompatibility and potent capacity to scavenge various reactive oxygen species (ROS). However, previous studies have mainly focused on acute ROS-related diseases, leaving a knowledge gap regarding their potential in chronic conditions. Furthermore, apart from their well-established antioxidant effects, it remains unclear whether MNPs target other intracellular molecular pathways. In this study, we synthesized ultra-small polyethylene glycol-incorporated Mn2+-chelated MNP (MMPP). We found that MMPP traversed the glomerular filtration barrier and specifically accumulated in renal tubules. Autosomal dominant polycystic kidney disease (ADPKD) is a chronic genetic disorder closely associated with increased oxidative stress and featured by the progressive enlargement of cysts originating from various segments of the renal tubules. Treatment with MMPP markedly attenuated oxidative stress levels, inhibited cyst growth, thereby improving renal function. Interestingly, we found that MMPP effectively inhibits a cyst-promoting gene program downstream of the cAMP-CREB pathway, a crucial signaling pathway implicated in ADPKD progression. Mechanistically, we observed that MMPP directly binds to the bZIP DNA-binding domain of CREB, leading to competitive inhibition of CREB's DNA binding ability and subsequent reduction in CREB target gene expression. In summary, our findings identify an intracellular target of MMPP and demonstrate its potential for treating ADPKD by simultaneously targeting oxidative stress and CREB transcriptional activity.

Deciphering Intercellular Communication of the Immune Landscape within Autosomal Dominant Polycystic Kidney Disease Microenvironment at Single-Cell Resolution

Introduction

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder that often leads to end-stage renal disease, with disease progression deeply influenced by the renal microenvironment. This study aims to unravel the critical cellular types and their intricate interactions within the ADPKD microenvironment.

Methods

Leveraging single-cell transcriptome data from seven ADPKD and three healthy human kidney samples, we systematically dissected the cellular landscape of the ADPKD microenvironment. Our approach included CellChat for cell-cell communication analysis, VISION for pathway enrichment analysis, pySCENIC for regulon activity calculation, and Monocle V3 for pseudotime trajectory construction.

Results

We identified nine major cell lineages, with a notable increase of mononuclear phagocytes (MNPs), T cells, and fibroblasts in the ADPKD microenvironment. These cells collectively orchestrated a distinctive microenvironment, marked by complex intercellular networks. Notably, a specific subset of macrophages exhibited an "M2-like" phenotype, which was driven by IL-10 signaling from M1-like macrophages and contributed to cyst cell proliferation. Immunosuppression was predominantly mediated by CD4+ T cells, activated by macrophages through immune checkpoint pathways, such as PDL1 signaling. The fibrotic expansion was a cumulative effect of fibroblast activation and proliferation, modulated by macrophages and cyst-lining epithelial cells.

Conclusion

This comprehensive investigation provides valuable insights into the diverse landscapes of the ADPKD microenvironment at single-cell resolution, emphasizing MNPs, T cells, and fibroblasts. The study unveils complex interactions among these cell types, shedding light on an understanding of the immunological aspect of ADPKD and proposing potential therapeutic targets.

Echocardiographic characteristics of autosomal dominant polycystic kidney disease

Cardiovascular complications in patients with autosomal dominant polycystic kidney disease (ADPKD) are frequently investigated extrarenal manifestations with contradictory outcomes. The primary goal of this study is to explore the prevalence of cardiovascular abnormalities using echocardiography and analyze their associations with clinical characteristics at different stages of chronic kidney disease (CKD) progression in ADPKD patients. We included sixty-eight patients in the study. All patients underwent transthoracic echocardiography using GE Vingmed Ultrasound (GE Norway Health Tech, Oslo, Norway). Demographic information, prior medical history, and antihypertensive medication use were recorded. To diagnose the rapid progression of CKD, creatinine levels were measured twice, with a one-year interval. Analysis revealed left ventricular hypertrophy (LVH) in over 40% of ADPKD patients, as indicated by various LVH parameters. Notably, a decline in estimated glomerular filtration rate (eGFR) after one year of observation was associated with increased left ventricular mass. Other prevalent findings included asymptomatic left ventricular diastolic dysfunction (ALVDD) in 39% of patients, left atrium (LA) enlargement in 39%, and mild valvular regurgitations in 80%. Ejection fraction, aortic root dimension, and the prevalence of mitral valve prolapse were not significantly increased. Cardiac indices did not differ substantially across the different eGFR stages. LVH, LA enlargement, ALVDD and valvular regurgitations are characteristics of cardiac phenotype in ADPKD. Cardiac indices were not different across different stages of CKD pointing towards the diagnosis of ADPKD being the main drive of their occurrence.

Chronic endothelial dopamine receptor stimulation improves endothelial function and hemodynamics in autosomal dominant polycystic kidney disease

Altered polycystin-mediated endothelial flow mechanosensitivity contributes to the development of hypertension and cardiovascular complications in patients with autosomal dominant polycystic kidney disease (ADPKD). Stimulation of endothelial type 5 dopamine receptors (DR5) can acutely compensate for the endothelial consequences of polycystin deficiency, but the chronic impact of this approach must be evaluated in ADPKD. Nineteen patients with ADPKD on standard of care therapy were randomized to receive a 2-month treatment with the DR agonist rotigotine using transdermal patches, nine at 2 mg/24hours and ten at 4 mg/24hours or while ten were untreated. Rotigotine at the dose of 4 mg/24hours significantly increased nitric oxide release (nitrite levels from 10±30 to 46±34 nmol/L) and radial artery endothelium-dependent flow-mediated dilatation (from 16.4±6.3 to 22.5±7.3%) in response to hand skin heating. Systemic hemodynamics were not significantly modified but aplanation tonometry showed that rotigotine at 4 mg/24hours reduced aortic augmentation index and pulse pressure without affecting carotid-to femoral pulse wave velocity. Plasma creatinine and urea, urinary cyclic AMP, which contributes to cyst growth in ADPKD and copeptin, a surrogate marker of vasopressin, were not affected by rotigotine. In mice with a specific deletion of polycystin-1 in endothelial cells, chronic infusion of the peripheral DR5 agonist fenoldopam also improved mesenteric artery flow-mediated dilatation and reduced blood pressure. Thus, our study demonstrates that in patients with ADPKD, chronic administration of rotigotine improves conduit artery endothelial function through the restoration of flow-induced nitric oxide release as well as hemodynamics suggesting that endothelial DR5 activation may represent a promising pharmacological approach to prevent cardiovascular complications of ADPKD.

Prenatal identification of a pathogenic maternal FGFR1 variant in two consecutive pregnancies with fetal forebrain malformations

OBJECTIVE

Holoprosencephaly (HPE) is the most common aberration of forebrain development, and it leads to a wide spectrum of developmental and craniofacial anomalies. HPE etiology is highly heterogeneous and includes both chromosomal abnormalities and single-gene defects.

METHODS

Here, we report an FGFR1 heterozygous variant detected by prenatal exome sequencing and inherited from the asymptomatic mother, in association with recurrent neurological abnormalities in the HPE spectrum in two consecutive pregnancies.

RESULTS

Individuals with germline pathogenic variants in FGFR1 (MIM: 136350) show extensive phenotypic variability, which ranges from asymptomatic carriers to hypogonadotropic hypogonadism, arhinencephaly, Kallmann's syndrome with associated features such as cleft lip and palate, skeletal anomalies, isolated HPE, and Hartsfield syndrome.

CONCLUSION

The presented case supports the role of exome sequencing in prenatal diagnosis when fetal midline structural anomalies are suggestive of a genetic etiology, as early as the first trimester of gestation. The profound heterogeneity of FGFR1 allelic disorders needs to be considered when planning prenatal screening even in asymptomatic carriers.

Genetic analysis and counseling of ADPKD caused by novel heterozygous mutations of PKD1 in two Chinese families: Case report

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease, characterized by the progressive formation of multiple cysts in both kidneys, destruction of the renal structure, changes in renal function and eventually leading to end-stage renal failure and renal transplantation. In our study, Whole-exome sequencing (WES) was used to identify the responsible mutation of ADPKD in two unrelated Chinese PKD families. The WES revealed three variants in the PKD1 gene, c.9857T > C in family 1, c.9860T > G and c.3496G > A in family 2. The comprehensive analysis of population frequency, conservation, structural prediction, and pathogenicity prediction by multiple software suggests that c.9857T > C and c.9860T > G in the PKD1 gene are the primary causes of occurrence and inheritance of ADPKD in family 1 and family 2, respectively. Due to the significant genetic heterogeneity of ADPKD, it's necessary to understand molecular mechanisms further and collect more data on gene mutations that cause ADPKD. The newly discovered PKD1 variant in this study can expand the database of gene variants and understanding of ADPKD, and provide valuable information for accurate diagnosis and genetic counseling of ADPKD families.

Mitral Valve Prolapse in a Patient With Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is a multisystemic heterogeneous disease characterized by the presence of cysts in several organs leading to progressive dysfunction. The cardiovascular manifestations of ADPKD include hypertension, left ventricular hypertrophy, and valvular heart disease, predominantly mitral valve abnormalities. We present the case of a 30-year-old male with a past medical history of ADPKD who was admitted to the emergency department due to sudden chest pain and signs of congestive heart failure for weeks. Echocardiography in the emergency department showed lateral wall hypokinesis and severe mitral regurgitation. Coronary angiography revealed a small collateral branch occlusion unsuitable for revascularization. On the first day of hospitalization, the patient developed an acute ischemia of the left lower limb, for which he underwent revascularization surgery. After the thrombectomy, the patient presented with fever, for which prophylactic antibiotics were started while awaiting investigation into surgical and cystic complications, such as infection, which were ruled out. Once stabilized, a second transthoracic echocardiogram confirmed the severe mitral regurgitation and prolapse due to posterior mitral valve flail, suggesting long-term primary mitral valve disease as the underlying mechanism for regurgitation. The patient underwent surgical mitral valve repair, which was complicated by suture dehiscence.  The severe mitral valve regurgitation was attributed to ADPKD, given the patient's family history, age, and typical cardiovascular findings and multiple renal and hepatic cysts observed. Further investigation into primary mitral valve disorders, such as soft connective tissue diseases like Marfan syndrome, was not deemed necessary.

Cyclin-dependent kinase 4 drives cystic kidney disease in the absence of mTORC1 signaling activity

Progression of cystic kidney disease has been linked to activation of the mTORC1 signaling pathway. Yet the utility of mTORC1 inhibitors to treat patients with polycystic kidney disease remains controversial despite promising preclinical data. To define the cell intrinsic role of mTORC1 for cyst development, the mTORC1 subunit gene Raptor was selectively inactivated in kidney tubular cells lacking cilia due to simultaneous deletion of the kinesin family member gene Kif3A. In contrast to a rapid onset of cyst formation and kidney failure in mice with defective ciliogenesis, both kidney function, cyst formation discerned by magnetic resonance imaging and overall survival were strikingly improved in mice additionally lacking Raptor. However, these mice eventually succumbed to cystic kidney disease despite mTORC1 inactivation. In-depth transcriptome analysis revealed the rapid activation of other growth-promoting signaling pathways, overriding the effects of mTORC1 deletion and identified cyclin-dependent kinase (CDK) 4 as an alternate driver of cyst growth. Additional inhibition of CDK4-dependent signaling by the CDK4/6 inhibitor Palbociclib markedly slowed disease progression in mice and human organoid models of polycystic kidney disease and potentiated the effects of mTORC1 deletion/inhibition. Our findings indicate that cystic kidneys rapidly adopt bypass mechanisms typically observed in drug resistant cancers. Thus, future clinical trials need to consider combinatorial or sequential therapies to improve therapeutic efficacy in patients with cystic kidney disease.

Perspectives of Patients and Clinicians on Reproductive Health Care and ADPKD

Introduction

Family planning and reproductive care are essential but complex aspects of lifecycle management for individuals with autosomal dominant polycystic kidney disease (ADPKD), given the potential genetic transmission and pregnancy-related complications. In this qualitative study, we studied the experiences and perspectives of patients with ADPKD and clinicians to identify areas for potential improvement in reproductive lifecycle care.

Methods

Focus group discussions (FGDs) were conducted in the Netherlands with patients with ADPKD, both men and women, who had children through varied reproductive choices; and clinicians, including (pediatric) nephrologists, obstetric gynecologists and geneticists. Thematic analysis, utilizing a grounded theory approach, was performed on verbatim transcriptions of recordings, followed by consensus discussions to finalize themes.

Results

Nine focus groups involving 31 participants (16 patients and 15 physicians) identified 6 key themes. These included the need for timely and comprehensive information dissemination from puberty on, understanding patient-specific decision-making factors, improving tailored psychosocial guidance and communication, the need for systematic efforts to take care of missed (minor) at-risk patients, addressing inequities in access to care, and improving multidisciplinary collaboration.

Conclusions

This study represents the first qualitative study of patient and physician perspectives on reproductive lifecycle care for ADPKD. We present valuable insights into factors influencing patients' reproductive decision-making, a comprehensive comparison between the perspectives of patients and clinicians on family planning and follow-up care of minors at risk for ADPKD, and recommendations for enhancing overall care quality. Incorporating these insights into clinical care could enhance patient-centered care and foster interdisciplinary collaborations to further improve the quality of reproductive health care services for individuals with ADPKD.

Renal Pelvic Cancer with Multiple Lung Metastases in a Patient with Polycystic Kidney Disease, Initially Diagnosed as Non-small Cell Lung Cancer: An Autopsy Case Report

A 64-year-old man with autosomal dominant polycystic kidney disease (ADPKD) on hemodialysis presented with multiple lung masses. A computed tomography (CT)-guided biopsy revealed non-small-cell lung cancer (NSCLC). A cavitary mass in the right lung indicated primary NSCLC (cT2N1M1a, stage IVA). Pembrolizumab was initiated because of a high programmed death-ligand 1 (PD-L1) expression (90%). On day 10 post-treatment, he developed acute respiratory failure with diffuse ground-glass opacities on chest CT, indicative of pembrolizumab-induced lung injury. Despite steroid pulse therapy, the patient died on day 13. An autopsy revealed left renal pelvic cancer with lung metastases, highlighting the diagnostic challenges in ADPKD.

Multiomics profiling of mouse polycystic kidney disease progression at a single-cell resolution

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and causes significant morbidity, ultimately leading to kidney failure. PKD pathogenesis is characterized by complex and dynamic alterations in multiple cell types during disease progression, hampering a deeper understanding of disease mechanism and the development of therapeutic approaches. Here, we generate a single-nucleus multimodal atlas of an orthologous mouse PKD model at early, mid, and late timepoints, consisting of 125,434 single-nucleus transcriptomic and epigenetic multiomes. We catalog differentially expressed genes and activated epigenetic regions in each cell type during PKD progression, characterizing cell-type-specific responses to Pkd1 deletion. We describe heterogeneous, atypical collecting duct cells as well as proximal tubular cells that constitute cyst epithelia in PKD. The transcriptional regulation of the cyst lining cell marker GPRC5A is conserved between mouse and human PKD cystic epithelia, suggesting shared gene regulatory pathways. Our single-nucleus multiomic analysis of mouse PKD provides a foundation to understand the earliest changes molecular deregulation in a mouse model of PKD at a single-cell resolution.

Incidental renal cell carcinoma post bilateral nephrectomy in autosomal dominant polycystic kidney disease

BACKGROUND

Renal cell carcinoma (RCC) is more common in patients with autosomal dominant polycystic kidney disease (ADPKD) than in the general population. Diagnosing RCC in ADPKD is challenging due to the presence of multiple renal cysts, often leading to delays and difficulties in distinguishing RCC from cyst infection or hemorrhage.

AIM

To analyze the prevalence and characterize the clinical features of RCC in patients with ADPKD undergoing simultaneous bilateral native nephrectomy.

METHODS

Between May 2017 and April 2024, 19 ADPKD patients undergoing hemodialysis and awaiting kidney transplantation due to end-stage renal disease (ESRD) underwent bilateral nephrectomies in a single center. Parameters such as patient characteristics, intraoperative blood loss, blood transfusion volume, length of hospital stay, and postoperative complications were documented. Pathological findings for RCC were reviewed.

RESULTS

A total of 38 kidneys were excised from 19 patients, with a mean age of 56.8 years and an average hemodialysis duration of 84.2 months. Eight patients underwent open nephrectomies, and 11 underwent hand-assisted laparoscopic nephrectomies. RCC was detected in 15.8% of kidneys, affecting 21.1% of patients. Two patients had multifocal RCC in both kidneys. All RCC cases were pT1 stage, with the largest lesion averaging 16.5 mm in diameter. The average operative duration was 120 minutes, with intraoperative blood loss averaging 184.2 mL. Five patients required blood transfusions. Postoperative complications occurred in five patients, with a mean hospital stay of 17.1 days. The mean follow-up period was 28.1 months.

CONCLUSION

The prevalence of RCC is higher in patients with ADPKD with ESRD than in those with ESRD alone. Thus, clinicians should be cautious and implement surveillance programs to monitor the development of RCC in patients with ADPKD, particularly those on dialysis.

Interventions for preventing the progression of autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the leading inherited cause of kidney disease. Clinical management has historically focused on symptom control and reducing associated complications. Improved understanding of the molecular and cellular mechanisms involved in kidney cyst growth and disease progression has resulted in new pharmaceutical agents targeting disease pathogenesis and preventing disease progression. However, the role of disease-modifying agents for all people with ADPKD is unclear. This is an update of a review first published in 2015.

OBJECTIVES

We aimed to evaluate the benefits and harms of interventions to prevent the progression of ADPKD and the safety based on patient-important endpoints, defined by the Standardised Outcomes in NephroloGy-Polycystic Kidney Disease (SONG-PKD) core outcome set, and general and specific adverse effects.

SEARCH METHODS

We searched the Cochrane Kidney and Transplants Register of Studies up to 13 August 2024 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any interventions for preventing the progression of ADPKD with other interventions, placebo, or standard care were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study risks of bias and extracted data. Summary estimates of effects were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 57 studies (8016 participants) that investigated 18 pharmacological interventions (vasopressin 2 receptor (V2R) antagonists, antihypertensive therapy, mammalian target of rapamycin (mTOR) inhibitors, somatostatin analogues, antiplatelet agents, eicosapentaenoic acids, statins, kinase inhibitors, diuretics, anti-diabetic agents, water intake, dietary intervention, and supplements) in this review. Compared to placebo, the V2R antagonist tolvaptan probably preserves eGFR (3 studies, 2758 participants: MD 1.26 mL/min/1.73 m2, 95% CI 0.73 to 1.78; I2 = 0%) and probably slows total kidney volume (TKV) growth in adults (1 study, 1307 participants: MD -2.70 mL/cm, 95% CI -3.24 to -2.16) (moderate certainty evidence). However, there was insufficient evidence to determine tolvaptan's impact on kidney failure and death. There may be no difference in serious adverse events; however, treatment probably increases nocturia, fatigue and liver enzymes, may increase dry mouth and thirst, and may decrease hypertension and urinary and upper respiratory tract infections. Data on the impact of other therapeutic interventions were largely inconclusive. Compared to placebo, somatostatin analogues probably decrease TKV (6 studies, 500 participants: SMD -0.33, 95% CI -0.51 to -0.16; I2 = 11%), probably have little or no effect on eGFR (4 studies, 180 participants: MD 4.11 mL/min/1.73 m3, 95% CI -3.19 to 11.41; I2 = 0%) (moderate certainty evidence), and may have little or no effect on kidney failure (2 studies, 405 participants: RR 0.64, 95% CI 0.16 to 2.49; I2 = 39%; low certainty evidence). Serious adverse events may increase (2 studies, 405 participants: RR 1.81, 95% CI 1.01 to 3.25; low certainty evidence). Somatostatin analogues probably increase alopecia, diarrhoea or abnormal faeces, dizziness and fatigue but may have little or no effect on anaemia or infection. The effect on death is unclear. Targeted low blood pressure probably results in a smaller per cent annual increase in TKV (1 study, 558 participants: MD -1.00, 95% CI -1.67 to -0.33; moderate certainty evidence) compared to standard blood pressure targets, had uncertain effects on death, but probably do not impact other outcomes such as change in eGFR or adverse events. Kidney failure was not reported. Data comparing antihypertensive agents, mTOR inhibitors, eicosapentaenoic acids, statins, vitamin D compounds, metformin, trichlormethiazide, spironolactone, bosutinib, curcumin, niacinamide, prescribed water intake and antiplatelet agents were sparse and inconclusive. An additional 23 ongoing studies were also identified, including larger phase III RCTs, which will be assessed in a future update of this review.

AUTHORS' CONCLUSIONS

Although many interventions have been investigated in patients with ADPKD, at present, there is little evidence that they improve patient outcomes. Tolvaptan is the only therapeutic intervention that has demonstrated the ability to slow disease progression, as assessed by eGFR and TKV change. However, it has not demonstrated benefits for death or kidney failure. In order to confirm the role of other therapeutic interventions in ADPKD management, large RCTs focused on patient-centred outcomes are needed. The search identified 23 ongoing studies, which may provide more insight into the role of specific interventions.

P2Y2R and Cyst Growth in Polycystic Kidney Disease

Key Points

Polycystic kidney disease (PKD) is characterized by continuous cyst growth, which results in a decline in kidney function. Deletion of P2Y2R and pharmacological antagonism of purinergic signaling significantly reduced cyst growth in an orthologous PKD mouse model. P2Y2R was expressed in cysts of human PKD nephrectomies, which makes P2Y2R a reasonable target for treatment of PKD.

Background

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by multiple bilateral kidney cysts that gradually enlarge, resulting in a decline in kidney function. Cyst growth is significantly driven by ATP-dependent chloride secretion mediated by the ion channel TMEM16A. This pathway is further augmented in advanced stages of the disease by hypoxia and activation of hypoxia-inducible factor (HIF)-1α . The mechanisms by which ATP leads to activation of TMEM16A and how HIF-1α contributes to cyst growth in vivo have remained elusive.

Methods

Mice with an inducible tubule-specific deletion of Pkd1 were compared with mice with an additional codeletion of the purinergic receptor P2y2r . Furthermore, animals were challenged by pharmacological activation of HIF-1α and Pkd1 -deficient mice were treated with suramin, an antagonist of purinergic signaling. In addition, expression of P2Y2R, TMEM16A, and HIF-1α was analyzed in nephrectomy samples from 27 patients with ADPKD.

Results

Genetic deletion of P2y2r significantly inhibited cyst growth in vivo . In addition, aggravation of the polycystic phenotype mediated by pharmacological activation of HIF-1α was reduced by deletion of P2y2r . Application of suramin to pharmacologically inhibit purinergic signaling also suppressed cyst enlargement in vivo . Analysis of kidney samples from 27 patients with ADPKD revealed significant expression of P2Y2R at the luminal site of the cyst-lining epithelium.

Conclusions

P2Y2R was significantly expressed in human and mouse polycystic kidneys. Deletion and antagonism of P2Y2R reduced cyst enlargement in an ADPKD mouse model.

Protocol for the nationwide registry of patients with polycystic kidney disease: japanese national registry of PKD (JRP)

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are major genetic polycystic kidney diseases that can progress to end-stage kidney disease (ESKD). Longitudinal data on the clinical characteristics associated with clinical outcomes in polycystic kidney disease (PKD), including the development of ESKD and cardiovascular disease (CVD) are lacking in Japan. To address this unmet need the authors are establishing a novel, web-based, Nationwide Cohort Registry Study-the Japanese Registry of PKD (JRP).

METHODS

The JRP is a prospective cohort study for ADPKD (aim to recruit n = 1000 patients), and both a retrospective and prospective study for ARPKD (aim to recruit n = 100). In the prospective registry, patients will be followed-up for 10 years every 6 months and 12 months for patients with ADPKD and ARPKD, respectively. Data collection will be recorded on Research Electronic Data Capture (REDCap) starting on April 1, 2024, with recruitment ending on March 31, 2029. (jRCT 1030230618).

RESULTS

Data to be collected include: baseline data, demographics, diagnostic and genetic information, radiological and laboratory findings, and therapeutic interventions. During follow-up, clinical events such as development of ESKD, hospitalization, occurrence of extra kidney complications including CVD events, and death will be recorded, as well as patient-reported health-related quality of life for patients with ADPKD.

CONCLUSIONS

The JRP is the first nationwide registry study for patients with ADPKD and ARPKD in Japan, providing researchers with opportunities to advance knowledge and treatments for ADPKD and ARPKD, and to inform disease management and future clinical practice.

Robotic Ultrasound and Novel Collagen Analyses for Polycystic Kidney Disease Research Using Mice

Key Points

Robotic ultrasound performed favorably compared with magnetic resonance imaging for evaluating total kidney volume. Collagen evaluation by two novel methods of picrosirius red imaging were more informative than the standard method by brightfield imaging. Findings can improve research by increasing speed and access to total kidney volume determination and sensitivity of collagen assessment.

Background

3D imaging and histology are critical tools for assessing polycystic kidney disease (PKD) in patients and animal models. Magnetic resonance (MR) imaging provides micron resolution but is time consuming and expensive, and access to equipment and expertise is limited. Robotic ultrasound (US) imaging has lower spatial resolution but is faster, more cost-effective, and accessible. Similarly, picrosirius red (PSR) staining and brightfield microscopy are commonly used to assess fibrosis; however, alternative methods have been shown in non-kidney tissues to provide greater sensitivity and more detailed structural characterization.

Methods

In this study, we evaluated the utility of robotic US and alternative methods of quantifying PSR staining for PKD research. We compared longitudinal total kidney volume measurements using US and MR imaging. We additionally compared PSR imaging and quantification using standard brightfield microscopy with that by circularly polarized light with hue analysis and fluorescence imaging analyzed using curvelet transform fiber extraction software for automatic detection of individual collagen fibers.

Results

Increased total kidney volume was detected by US in Pkd1 RC/RC versus wild-type (WT) at time points spanning from early to established disease. US interobserver variability was greater but allowed scanning in 2–5 minutes/mouse, whereas MR imaging required 20–30 minutes/mouse. While no change in fibrotic index was detected in this cohort of relatively mild disease using brightfield microscopy, polarized light showed fibers skewed thinner in Pkd1 RC/RC versus WT. Fluorescence imaging showed a higher density of collagen fibers in Pkd1 RC/RC versus WT, and fibers were thinner and curvier with no change in length. In addition, fiber density was higher in both glomeruli and tubules in Pkd1 RC/RC , and glomeruli had a higher fiber density than tubules in Pkd1 RC/RC and trended higher in WT.

Conclusions

These studies show robotic US is a rigorous imaging tool for preclinical PKD research. In addition, they demonstrate the increased sensitivity of polarized and fluorescence analysis of PSR-stained collagen.

Clinical Approach to Genetic Cerebral Arteriopathy in the Adult Patient With Ischemic Stroke

Genetic arteriopathies leading to stroke in adults constitute a diverse group of cerebrovascular disorders with distinct etiologies, pathophysiologic mechanisms, and clinical presentations. As imaging modalities better delineate subtle changes in cerebral vasculature and access to genetic testing increases, the detection rate for these conditions is expected to rise, particularly among young adults with idiopathic cerebral arteriopathy and stroke. Adults with stroke in the setting of a genetic cerebral arteriopathy often present with few traditional stroke risk factors and, in certain cases, have characteristic clinical features, cerebrovascular imaging findings, and often concurrent systemic vasculopathy, such as aortopathy, which are important to recognize. Given that there are over 50 recognized genetic cerebral arteriopathies that can cause ischemic and hemorrhagic stroke in young adults, it can be a significant diagnostic challenge for the practicing neurologist when faced with a genetic cerebral arteriopathy, because clinical algorithms for a systematic approach to genetic cerebral arteriopathies are lacking. In this review, we present a phenotype-driven, clinically oriented algorithm to guide the diagnostic workup when suspecting a genetic cerebral arteriopathy in an adult patient while highlighting the genetic basis of each disease, molecular mechanisms, clinical manifestations, diagnostic approaches, and emerging therapeutic strategies. Moreover, given the lack of widely available gene panels for diagnostic germline testing for genetic cerebral arteriopathies, we propose key genes to be tested and focused on in each clinical scenario, to better decipher the underlying diagnosis in these rare conditions.

New Mutation Associated with Polycystic Kidney Disease Type I: A Case Report

INTRODUCTION

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most prevalent heritable disorders, characterized by the progressive development of kidney cysts leading to renal failure. It is primarily caused by mutations in the PKD1 and PKD2 genes, which account for approximately 85% and 15% of cases, respectively. This case report describes a previously unreported mutation in the PKD1 gene, identified in a family involving an aunt and her niece with ADPKD.

CASE PRESENTATION

The index case, a 56-year-old female with chronic kidney disease stage 3b secondary to ADPKD and hypertension, exhibited a strong family history of polycystic kidney disease (PKD). Initial genetic evaluations did not identify any recognized pathogenic mutations, leading to a more detailed investigation which revealed a novel mutation in the PKD1 gene. This mutation was also found in her niece, who presented with early-onset disease.

CONCLUSIONS

The identification of a heterozygous six-nucleotide deletion, c.2084_2089del, resulting in the in-frame deletion of two amino acids, p.Pro695_Ala696del, in the PKD1 gene, has been linked with ADPKD in these patients. This report emphasizes the need for continuous updates to genetic data for a deeper understanding of the diagnosis and prognosis of ADPKD that could potentially aid in targeted therapy.

Trigger Warning: How Modern Diet, Lifestyle, and Environment Pull the Trigger on Autosomal Dominant Polycystic Kidney Disease Progression

Understanding chronic kidney disease (CKD) through the lens of evolutionary biology highlights the mismatch between our Paleolithic-optimized genes and modern diets, which led to the dramatically increased prevalence of CKD in modern societies. In particular, the Standard American Diet (SAD), high in carbohydrates and ultra-processed foods, causes conditions like type 2 diabetes (T2D), chronic inflammation, and hypertension, leading to CKD. Autosomal dominant polycystic kidney disease (ADPKD), a genetic form of CKD, is characterized by progressive renal cystogenesis that leads to renal failure. This review challenges the fatalistic view of ADPKD as solely a genetic disease. We argue that, just like non-genetic CKD, modern dietary practices, lifestyle, and environmental exposures initiate and accelerate ADPKD progression. Evidence shows that carbohydrate overconsumption, hyperglycemia, and insulin resistance significantly impact renal health. Additionally, factors like dehydration, electrolyte imbalances, nephrotoxin exposure, gastrointestinal dysbiosis, and renal microcrystal formation exacerbate ADPKD. Conversely, carbohydrate restriction, ketogenic metabolic therapy (KMT), and antagonizing the lithogenic risk show promise in slowing ADPKD progression. Addressing disease triggers through dietary modifications and lifestyle changes offers a conservative, non-pharmacological strategy for disease modification in ADPKD. This comprehensive review underscores the urgency of integrating diet and lifestyle factors into the clinical management of ADPKD to mitigate disease progression, improve patient outcomes, and offer therapeutic choices that can be implemented worldwide at low or no cost to healthcare payers and patients.

Discovery of putative inhibitors of human Pkd1 enzyme: Molecular docking, dynamics and simulation, QSAR, and MM/GBSA

Polycystic kidney disease is the most prevalent hereditary kidney disease globally and is mainly linked to the overexpression of a gene called PKD1. To date, there is no effective treatment available for polycystic kidney disease, and the practicing treatments only provide symptomatic relief. Discovery of the compounds targeting the PKD1 gene by inhibiting its expression under the disease condition could be crucial for effective drug development. In this study, a molecular docking and molecular dynamic simulation, QSAR, and MM/GBSA-based approaches were used to determine the putative inhibitors of the Pkd1 enzyme from a library of 1379 compounds. Initially, fourteen compounds were selected based on their binding affinities with the Pkd1 enzyme using MOE and AutoDock tools. The selected drugs were further investigated to explore their properties as drug candidates and the stability of their complex formation with the Pkd1 enzyme. Based on the physicochemical and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) properties, and toxicity profiling, two compounds including olsalazine and diosmetin were selected for the downstream analysis as they demonstrated the best drug-likeness properties and highest binding affinity with Pkd1 in the docking experiment. Molecular dynamic simulation using Gromacs further confirmed the stability of olsalazine and diosmetin complexes with Pkd1 and establishing interaction through strong bonding with specific residues of protein. High biological activity and binding free energies of two complexes calculated using 3D QSAR and Schrodinger module, respectively further validated our results. Therefore, the molecular docking and dynamics simulation-based in-silico approach used in this study revealed olsalazine and diosmetin as potential drug candidates to combat polycystic kidney disease by targeting Pkd1 enzyme.

Long-Term Outcomes of Nephrectomy Before Kidney Transplantation in Patients With Polycystic Kidney Disease

BACKGROUND

Polycystic kidney disease (PKD) is the most common hereditary kidney disorder. In most patients, the disease progresses to end stage kidney disease, which is treated preferably by kidney transplantation. In certain clinical circumstances, a pretransplant nephrectomy is indicated. Data regarding long-term outcomes of pretransplant nephrectomy are limited. In this study, we aimed to compare patient and graft survival, as well as other long-term outcomes of kidney transplantation, between patients with PKD who had a pretransplant nephrectomy and those who have not.

METHODS

A retrospective analysis of 112 adult kidney transplant recipients with PKD, 36 (32.14%) of which underwent a pretransplant nephrectomy.

RESULTS

In a mean follow-up period of 79 and 129 months (for patients who underwent nephrectomy and patients who did not, respectively), no significant differences were found in patient and graft survival, after adjustment to age and donor type. In addition, rate of hospitalizations, urinary tract infections requiring hospitalization, diabetes mellitus, and erythrocytosis post-transplant were similar in both cohorts.

CONCLUSIONS

Pretransplant nephrectomy in patients with PKD is not associated with increased risk of mortality and other long-term complications following kidney transplantation.

miR-542-5p targets GREM1 to affect the progression of renal fibrosis

Renal fibrosis (RF) is a typical pathological presentation of end-stage chronic kidney disease (CKD) and autosomal dominant polycystic kidney disease (ADPKD). However, the precise regulatory mechanisms governing this re-expression process remain unclear. Differentially expressed microRNAs (miRNAs) associated with RF were screened by microarray analysis using the Gene Expression Omnibus (GEO) database. The miRNAs upstream of the genes in question were predicted using the miRWalk database. The miRNAs involved in the two GEO data sets were intersected to identify key miRNAs; their regulatory pathways were investigated using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Subsequently, the effects and the underlying mechanisms of target miRNA on RF were examined in a unilateral ureteral obstruction (UUO)-induced mice renal fibrotic model and a transforming growth factor-β1 (TGF-β1)-induced tubular epithelium (HK-2) fibrotic cell model. In total, 109 and 32 differentially expressed miRNAs were identified in the GSE133530 and GSE80247 data sets, respectively. GREM1 was identified as a hub gene, where its 2196 upstream miRNAs were predicted; miR-574-5p was found to be downregulated and closely related to fibrosis after data set intersection and enrichment analyses, thus was selected for further investigation. A differential expression heatmap (GSE162794) showed that miR-542-5p was downregulated. The expression of GREM1 mRNA was upregulated, whereas that of miR-542-5p was downregulated in UUO mice and fibrotic HK-2 cells as compared with the relevant controls. The binding site of miR-542-5p was predicted at the 3'UTR region of GREM1 and was confirmed by subsequent dual luciferase reporter gene assay. Western blot analysis showed that Gremlin-1 and Fibronectin were significantly upregulated after induction of TGF-β1; when miR-542-5p was overexpressed or GREM1 mRNA was interfered, the upregulations of Gremlin-1 and Fibronectin were significantly reduced. Our research demonstrates that miR-542-5p plays a critical role in the progression of RF, and thus may be a promising therapeutic target for CKD and ADPKD.

Kidney Energetics and Cyst Burden in Autosomal Dominant Polycystic Kidney Disease: A Pilot Study

RATIONALE & OBJECTIVE

In this pilot study, we hypothesized that autosomal dominant polycystic kidney disease (ADPKD) is characterized by impaired kidney oxidative metabolism that associates with kidney size and cyst burden.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

Twenty adults with ADPKD (age, 31±6 years; 65% women; body mass index [BMI], 26.8 [22.7-30.4] kg/m2; estimated glomerular filtration rate [eGFR, 2021 CKD-EPI creatinine], 103±18mL/min/1.73m2; height-adjusted total kidney volume [HTKV], 731±370mL/m; Mayo classifications 1B [5%], 1C [42%], 1D [21%], and 1E [32%]) and 11 controls in normal weight category (NWC) (age, 25±3 years; 45% women; BMI, 22.5 [21.7-24.2] kg/m2; eGFR, 113±15mL/min/1.73m2; HTKV, 159±31mL/m) at the University of Colorado Anschutz Medical Campus.

PREDICTORS

ADPKD status (yes/no) and severity (Mayo classifications).

OUTCOME

HTKV and cyst burden by magnetic resonance imaging, kidney oxidative metabolism, and perfusion by 11C-acetate positron emission tomography/computed tomography, insulin sensitivity by hyperinsulinemic-euglycemic clamps (presented as ratio of M-value of steady state insulin concentration [M/I]).

ANALYTICAL APPROACH

For categorical variables, χ2/Fisher's exact tests, and for continuous variables t tests/Mann-Whitney U tests. Pearson correlation was used to estimate the relationships between variables.

RESULTS

Compared with NWC individuals, the participants with ADPKD exhibited lower mean±SD M/I ratio (0.586±0.205 vs 0.424±0.171 [mg/kg lean/min]/(μIU/mL), P=0.04), lower median cortical perfusion (1.93 [IQR, 1.80-2.09] vs 0.68 [IQR, 0.47-1.04] mL/min/g, P<0.001) and lower median total kidney oxidative metabolism (0.17 [IQR, 0.16-0.19] vs. 0.14 [IQR, 0.12-0.15] min-1, P=0.001) in voxel-wise models excluding cysts. HTKV correlated inversely with cortical perfusion (r: -0.83, P < 0.001), total kidney oxidative metabolism (r: -0.61, P<0.001) and M/I (r: -0.41, P = 0.03).

LIMITATIONS

Small sample size and cross-sectional design.

CONCLUSIONS

Adults with ADPKD and preserved kidney function exhibited impaired renal perfusion and kidney oxidative metabolism across a wide range of cysts and kidney enlargements.

FUNDING

Grants from government (National Institutes of Health, Centers for Disease Control and Prevention) and not-for-profit (JDRF) entities.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study numbers NCT04407481 and NCT04074668.

PLAIN-LANGUAGE SUMMARY

In our study, we explored how a common genetic kidney condition, autosomal dominant polycystic kidney disease (ADPKD), relates to kidney metabolism. ADPKD leads to the growth of numerous cysts in the kidneys, which can impact their ability to work properly. We wanted to understand the kidneys' ability to process oxygen and blood flow in ADPKD. Our approach involved using advanced imaging techniques to observe kidney metabolism and blood flow in people with ADPKD compared with healthy individuals. We discovered that those with ADPKD had significant changes in kidney oxygen metabolism even when their kidney function was still normal. These findings are crucial as they provide deeper insights into ADPKD, potentially guiding future treatments to target these changes.

The Impact of Autosomal Dominant Polycystic Kidney Disease in Children: A Nephrological, Nutritional, and Psychological Point of View

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary disorder characterized by the formation of numerous fluid-filled cysts in the kidneys, leading to progressive renal failure and various extrarenal complications, including hypertension. This review explores the genetic basis of ADPKD, including emerging evidence of epigenetic mechanisms in modulating gene expression and disease progression in ADPKD. Furthermore, it proposes to examine the pathological characteristics of this condition at the nephrological, cardiovascular, nutritional, and psychological levels, emphasizing that the follow-up of patients with ADPKD should be multidisciplinary from a young pediatric age.

Dapagliflozin administration for 1 year promoted kidney enlargement in patient with ADPKD

To date, there is insufficient evidence regarding use of sodium-glucose cotransporter-2 (SGLT2) inhibitors for patients with autosomal-dominant polycystic kidney disease (ADPKD), as such cases have been excluded from previous clinical trials exploring the kidney protection effects of such medications. Here, findings of an ADPKD patient who received dapagliflozin, a selective SGLT2 inhibitor, for 1 year are presented. A 38-year-old woman with a family history of ADPKD wished for treatment with dapagliflozin. After starting administration at 10 mg/day, total kidney volume (TKV) continued to increase, from 1641 to 1764 mL after 84 days and then to 2297 mL after 340 days. The estimated glomerular filtration rate (eGFR) was also decreased from 67.3 to 56.2 mL/min/1.73 m2, and then to 51.4 mL/min/1.73 m2 at those times. Immediately after discontinuation of dapagliflozin, TKV and eGFR were slightly improved to 2263 mL and 55.1 mL/min/1.73 m2, respectively. Following a review of basic research studies, we consider that increased intratubular urinary osmotic pressure, compensatory glucose reabsorption by sodium-glucose cotransporter-1 in the late proximal tubule, and hypertrophy shown in collected cells caused by increased vasopressin may be associated with ADPKD disease progression. Caution may be needed when administering dapagliflozin to patients with ADPKD.

Progressive Polycystic Kidney Disease in an Infant Girl With TSC2/PKD1 Contiguous Gene Syndrome

TSC2/PKD1 contiguous gene syndrome is caused by deletions involving the TSC2 and PKD1 genes that lead to tuberous sclerosis complex and autosomal dominant polycystic kidney disease. It is characterized by early-onset severe cystic kidney disease with progressive enlargement of the kidneys and the cysts. As it can lead to early hypertension and an accelerated decline of kidney function, early genetic testing is needed for early diagnosis of this syndrome, and more frequent imaging-based examinations are necessary to assess disease progression and determine appropriate management. We report the case of an infant girl with TSC2/PKD1 contiguous gene syndrome who presented with epileptic seizures. Brain magnetic resonance imaging (MRI) revealed subependymal nodules and cortical tubers, and abdominal MRI revealed polycystic kidney lesions and enlargement of both kidneys. TSC2/PKD1 contiguous gene syndrome was suspected from her radiological features, and we confirmed the presence of a deletion in the girl's genome, which included the TSC2 and PKD1 genes, via microarray analysis. Thereafter, we evaluated the change in kidney size via repeated abdominal MRI. The polycystic kidney lesions enlarged, and the patient developed hypertension in early childhood, for which we administered an angiotensin-converting enzyme inhibitor. We emphasize the importance of evaluation with longitudinal abdominal imaging because renal cysts tend to enlarge rapidly and induce hypertension, as demonstrated in our case.

Implementation and Evaluation of a National Multidisciplinary Kidney Genetics Clinic Network Over 10 Years

Introduction

Diagnostic genomic sequencing is the emerging standard of care in nephrology. There is a growing need to scale up the implementation of genomic diagnostics nationally to improve patient outcomes.

Methods

This pragmatic study provided genomic or genetic testing to patients with suspected monogenic kidney disease through a national network of kidney genetics clinics (KGCs). We sought to evaluate the experiences of implementing genomic diagnostics across Australia and associated diagnostic outcomes between 2013 and 2022.

Results

We successfully established and expanded a nationwide network of 20 clinics as of 2022; concurrently developing laboratory, research, and education programs to scale the clinical application of genomics in nephrology. We report on an Australian cohort of 1506 kidney patients, of whom 1322 received their test results. We assessed barriers to implementation in the nephrology context, and where possible, applied real-time solutions to improve clinical processes over 10 years.

Conclusion

Developing a multidisciplinary kidney genetics model across multiple health services nationally was highly successful. This model supported optimal care of individuals with monogenic kidney disease in an economically responsible way. It has continued to evolve with technological and service developments and is now set to scale further as genomic testing for kidney patients transitions to health care system funding.

Quantitative susceptibility mapping for detection of kidney stones, hemorrhage differentiation, and cyst classification in ADPKD

BACKGROUND AND PURPOSE

The objective is to demonstrate feasibility of quantitative susceptibility mapping (QSM) in autosomal dominant polycystic kidney disease (ADPKD) patients and to compare imaging findings with traditional T1/T2w magnetic resonance imaging (MRI).

METHODS

Thirty-three consecutive patients (11 male, 22 female) diagnosed with ADPKD were initially selected. QSM images were reconstructed from the multiecho gradient echo data and compared to co-registered T2w, T1w, and CT images. Complex cysts were identified and classified into distinct subclasses based on their imaging features. Prevalence of each subclass was estimated.

RESULTS

QSM visualized two renal calcifications measuring 9 and 10 mm and three pelvic phleboliths measuring 2 mm but missed 24 calcifications measuring 1 mm or less and 1 larger calcification at the edge of the field of view. A total of 121 complex T1 hyperintense/T2 hypointense renal cysts were detected. 52 (43%) Cysts appeared hyperintense on QSM consistent with hemorrhage; 60 (49%) cysts were isointense with respect to simple cysts and normal kidney parenchyma, while the remaining 9 (7%) were hypointense. The presentation of the latter two complex cyst subtypes is likely indicative of proteinaceous composition without hemorrhage.

CONCLUSION

Our results indicate that QSM of ADPKD kidneys is possible and uniquely suited to detect large renal calculi without ionizing radiation and able to identify properties of complex cysts unattainable with traditional approaches.