Developments in the management of autosomal dominant polycystic kidney disease

Acute renal intracystic hemorrhage in patients with autosomal dominant polycystic kidney disease

BACKGROUND

Renal cyst bleeding is a frequent problem in patients with autosomal dominant polycystic kidney disease (ADPKD). However, information is still limited on its frequency, causative factors, and effects on enlargement of polycystic kidneys in ADPKD.

METHODS

We investigated the total volume of acute renal intracystic hemorrhage and its association with total kidney volume (TKV) in a large series of patients with ADPKD on dialysis, referred for renal transcatheter arterial embolization. All patients had undergone CT scan and MRI scan before the procedure. We evaluated factors potentially associated with acute renal intracystic hemorrhage. The association between the  volume of acute renal intracystic hemorrhage and the potential predisposing and associated factors was analysed by univariable and multivariable regressions.  RESULTS: We enrolled 199 patients who underwent renal transcatheter arterial embolization from 2014 to 2018 (107 men, 92 women; mean age 59.1 ± 8.6 years). The median volume of acute renal intracystic hemorrhage was 97.3 ml (interquartile range 36.6-261.7 ml). Multivariable analysis revealed that body weight, kidney stones, systolic blood pressure, and total volume of acute renal intracystic hemorrhage were significantly associated with TKV; age, body mass index, smoking, renal cyst infection, serum alkaline phosphatase, and TKV were significantly associated with the volume of acute renal intracystic hemorrhage ; and sex, age, dialysis vintage, TKV, and total volume of acute renal intracystic hemorrhage were significantly associated with the number of microcoils required to achieve renal  transcatheter arterial embolization. Total volume of acute renal intracystic hemorrhage was significantly associated with TKV (r = 0.15, p = 0.0325) and was greater in younger patients (r= - 0.32, p < 0.0001). Total volume of acute renal intracystic hemorrhage was also correlated with the number of microcoils required for renal transcatheter arterial embolization (r = 0.23, p = 0.0012).

CONCLUSION

Acute renal intracystic hemorrhage is frequent among ADPKD patients on dialysis, and total volume of acute renal intracystic hemorrhage significantly associated with  TKV. Total volume of acute renal intracystic hemorrhage  was greater in younger patients with higher renal artery luminal size. These results suggest that renal cyst bleeding and renal artery blood flow may synergistically accelerate the enlargement of polycystic kidneys in ADPKD patients on dialysis.

Delayed diagnosis of bladder cancer in a patient with autosomal dominant polycystic kidney disease

ABSTRACT

Approximately 50% of autosomal dominant polycystic kidney disease (ADPKD) patients have gross hematuria, but few cases of bladder cancer complications are known. We report a case of a 49-year-old female ADPKD patient with bladder cancer, who was presented to our hospital 4 months after the onset of gross hematuria. A computed tomography (CT) scan showed a bladder mass, enlarged pelvic and left inguinal lymph nodes, multiple liver cysts, and a polycystic kidney. Based on family history, CT scan results, and lymph node biopsy, we diagnosed the patient with uroplakin III-negative bladder cancer with squamous metaplasia and ADPKD. The patient was treated with systemic chemotherapy but died 2 months after the definitive diagnosis. The delayed diagnosis was disastrous, and malignancy should be considered in the differential diagnosis when symptoms suggestive of malignancy such as hematuria appear. Particularly, uroplakin III-negative advanced bladder cancer has a poor prognosis and requires early diagnosis and treatment.

Consensus document on autosomal dominant polycystic kindey disease from the Spanish Working Group on Inherited Kindey Diseases. Review 2020

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent cause of genetic renal disease and accounts for 6-10% of patients on kidney replacement therapy (KRT). Very few prospective, randomized trials or clinical studies address the diagnosis and management of this relatively frequent disorder. No clinical guidelines are available to date. This is a revised consensus statement from the previous 2014 version, presenting the recommendations of the Spanish Working Group on Inherited Kidney Diseases, which were agreed to following a literature search and discussions. Levels of evidence mostly are C and D according to the Centre for Evidence-Based Medicine (University of Oxford). The recommendations relate to, among other topics, the use of imaging and genetic diagnosis, management of hypertension, pain, cyst infections and bleeding, extra-renal involvement including polycystic liver disease and cranial aneurysms, management of chronic kidney disease (CKD) and KRT and management of children with ADPKD. Recommendations on specific ADPKD therapies are provided as well as the recommendation to assess rapid progression.

Shedding the Light on the Natural History of Intracranial Aneurysms: An Updated Overview

The exact molecular pathways underlying the multifactorial natural history of intracranial aneurysms (IAs) are still largely unknown, to the point that their understanding represents an imperative challenge in neurovascular research. Wall shear stress (WSS) promotes the genesis of IAs through an endothelial dysfunction causing an inflammatory cascade, vessel remodeling, phenotypic switching of the smooth muscle cells, and myointimal hyperplasia. Aneurysm growth is supported by endothelial oxidative stress and inflammatory mediators, whereas low and high WSS determine the rupture in sidewall and endwall IAs, respectively. Angioarchitecture, age older than 60 years, female gender, hypertension, cigarette smoking, alcohol abuse, and hypercholesterolemia also contribute to growth and rupture. The improvements of aneurysm wall imaging techniques and the implementation of target therapies targeted against inflammatory cascade may contribute to significantly modify the natural history of IAs. This narrative review strives to summarize the recent advances in the comprehension of the mechanisms underlying the genesis, growth, and rupture of IAs.

Oral delivery of metformin by chitosan nanoparticles for polycystic kidney disease

Nanoparticle drug delivery has many advantages over small molecule therapeutics, including reducing off-target side effects and increasing drug potency. However, many nanoparticles are administered parenterally, which is challenging for chronic diseases such as polycystic kidney disease (PKD), the most common hereditary disease worldwide in which patients need continuous treatment over decades. To address this clinical need, we present the development of nanoparticles synthesized from chitosan, a widely available polymer chosen for its ability to improve oral bioavailability. Specifically, we optimized the synthesis parameters of chitosan nanoparticles and demonstrate mucoadhesion and permeation across an intestinal barrier model in vitro. Furthermore, when administered orally to mice, ex vivo imaging of rhodamine-loaded chitosan nanoparticles showed significantly higher accumulation in the intestines compared to the free model drug, as well as 1.3 times higher serum area under the curve (AUC), demonstrating controlled release and improved serum delivery over 24 h. To test its utility for chronic diseases such as PKD, we loaded the candidate PKD drug, metformin, into chitosan nanoparticles, and upon oral administration to a PKD murine model (Pkd1fl/fl;Pax8-rtTA;Tet-O cre), a lower cyst burden was observed compared to free metformin, and was well tolerated upon repeated dosages. Blood urea nitrogen (BUN) and creatinine levels were similar to untreated mice, demonstrating kidney and biocompatibility health. Our study builds upon previous chitosan-based drug delivery approaches, and demonstrates a novel, oral nanoformulation for PKD.

Autosomal dominant polycystic kidney disease and pioglitazone for its therapy: a comprehensive review with an emphasis on the molecular pathogenesis and pharmacological aspects

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited chronic kidney disorder (CKD) that is characterized by the development of numerous fluid-filled cysts in kidneys. It is caused either due to the mutations in the PKD1 or PKD2 gene that encodes polycystin-1 and polycystin-2, respectively. This condition progresses into end-stage renal disorder if the renal or extra-renal clinical manifestations remain untreated. Several clinical trials with a variety of drugs have failed, and the only Food and Drugs Administration (FDA) approved drug to treat ADPKD to date is tolvaptan that works by antagonizing the vasopressin-2 receptor (V2R). The pathology of ADPKD is complex and involves the malfunction of different signaling pathways like cAMP, Hedgehog, and MAPK/ERK pathway owing to the mutated product that is polycystin-1 or 2. A measured yet substantial number of preclinical studies have found pioglitazone to decrease the cystic burden and improve the renal function in ADPKD. The peroxisome proliferator-activated receptor-gamma is found on the epithelial cells of renal collecting tubule and when it gets agonized by pioglitazone, confers efficacy in ADPKD treatment through multiple mechanisms. There is only one clinical trial (ongoing) wherein it is being assessed for its benefits and risk in patients with ADPKD, and is expected to get approval from the regulatory body owing to its promising therapeutic effects. This article would encompass the updated information on the epidemiology, pathophysiology of ADPKD, different mechanisms of action of pioglitazone in the treatment of ADPKD with preclinical and clinical shreds of evidence, and related safety updates.

'A sword of Damocles': patient and caregiver beliefs, attitudes and perspectives on presymptomatic testing for autosomal dominant polycystic kidney disease: a focus group study

BACKGROUND AND OBJECTIVES

Presymptomatic testing is available for early diagnosis of hereditary autosomal dominant polycystic kidney disease (ADPKD). However, the complex ethical and psychosocial implications can make decision-making challenging and require an understanding of patients' values, goals and priorities. This study aims to describe patient and caregiver beliefs and expectations regarding presymptomatic testing for ADPKD.

DESIGN, SETTING AND PARTICIPANTS

154 participants (120 patients and 34 caregivers) aged 18 years and over from eight centres in Australia, France and Korea participated in 17 focus groups. Transcripts were analysed thematically.

RESULTS

We identified five themes: avoiding financial disadvantage (insecurity in the inability to obtain life insurance, limited work opportunities, financial burden); futility in uncertainty (erratic and diverse manifestations of disease limiting utility, taking preventive actions in vain, daunted by perplexity of results, unaware of risk of inheriting ADPKD); lacking autonomy and support in decisions (overwhelmed by ambiguous information, medicalising family planning, family pressures); seizing control of well-being (gaining confidence in early detection, allowing preparation for the future, reassurance in family resilience); and anticipating impact on quality of life (reassured by lack of symptoms, judging value of life with ADPKD).

CONCLUSIONS

For patients with ADPKD, presymptomatic testing provides an opportunity to take ownership of their health through family planning and preventive measures. However, these decisions can be wrought with tensions and uncertainty about prognostic implications, and the psychosocial and financial burden of testing. Healthcare professionals should focus on genetic counselling, mental health and providing education to patients' families to support informed decision-making. Policymakers should consider the cost burden and risk of discrimination when informing government policies. Finally, patients are recommended to focus on self-care from an early age.

Systems biology approaches toward autosomal dominant polycystic kidney disease (ADPKD)

Background

Autosomal dominant polycystic kidney disease (ADPKD), a common of monogenetic disorder caused by the polycystic kidney disease-1 (PKD1) or PKD2 genes deficiency. In this study, we have re-analyzed a microarray dataset to generate a holistic view of this disease.

Methodology

GSE7869, an expression profiling dataset was downloaded from the Gene Expression Omnibus (GEO) database. After quality control assessment, using GEO2R tool of GEO, genes with adjusted p-value ≤ 0.05 were determined as differentially expressed (DE). The expression profiles from ADPKD samples in different sizes were compared. Using CluePedia plugin of Cytoscape software, the protein–protein interaction (PPI) networks were constructed and analyzed by Cytoscape NetworkAnalyzer tool and MCODE application. Pathway enrichment analysis of clustered genes by MCODE with the high centrality parameters in PPI networks was performed using Cytoscape ClueGO plugin. Moreover, by Enrichr database, microRNAs (miRNAs) and transcription factors (TFs) targeted DE genes were identified.

Results

In this study to explore the molecular pathogenesis of kidney in ADPKD, mRNA expression profiles of cysts from patients in different sizes were re-analyzed. The comparisons were performed between normal with minimally cystic tissue (MCT) samples, MCTs with small cysts, and small cysts with large cysts. 512, 7024, and 655 DE genes were determined, respectively. The top central genes, e.g. END1, EGFR, and FOXO1 were identified with topology and clustering analysis. DE genes that were significantly enriched in PPI networks are critical genes and their roles in ADPKD remain to be assessed in future experimental studies beside miRNAs and TFs predicted. Furthermore, the functional analysis resulted in which most of them are expected to be associated with ADPKD pathogenesis, such as signal pathways that involved in cell growth, inflammation, and cell polarity.

Conclusion

We have here explored systematic approaches for molecular mechanisms assay of ADPKD as a monogenic disease, which may also be used for other monogenetic diseases beside complex diseases to provide suitable therapeutic targets.

Ciliotherapy: Remote Control of Primary Cilia Movement and Function by Magnetic Nanoparticles

Patients with polycystic kidney disease (PKD) are characterized with uncontrolled hypertension. Hypertension in PKD is a ciliopathy, an abnormal function and/or structure of primary cilia. Primary cilia are cellular organelles with chemo and mechanosensory roles. In the present studies, we designed a cilia-targeted (CT) delivery system to deliver fenoldopam specifically to the primary cilia. We devised the iron oxide nanoparticle (NP)-based technology for ciliotherapy. Live imaging confirmed that the CT-Fe₂O₃-NPs specifically targeted primary cilia in cultured cells in vitro and vascular endothelia in vivo. Importantly, the CT-Fe₂O₃-NPs enabled the remote control of the movement and function of a cilium with an external magnetic field, making the nonmotile cilium exhibit passive movement. The ciliopathic hearts displayed hypertrophy with compromised functions in left ventricle pressure, stroke volume, ejection fraction, and overall cardiac output because of prolonged hypertension. The CT-Fe₂O₃-NPs significantly improved cardiac function in the ciliopathic hypertensive models, in which the hearts also exhibited arrhythmia, which was corrected with the CT-Fe₂O₃-NPs. Intraciliary and cytosolic Ca²⁺ were increased when cilia were induced with fluid flow or magnetic field, and this served as a cilia-dependent mechanism of the CT-Fe₂O₃-NPs. Fenoldopam-alone caused an immediate decrease in blood pressure, followed by reflex tachycardia. Pharmacological delivery profiles confirmed that the CT-Fe₂O₃-NPs were a superior delivery system for targeting cilia more specifically, efficiently, and effectively than fenoldopam-alone. The CT-Fe₂O₃-NPs altered the mechanical properties of nonmotile cilia, and these nano-biomaterials had enormous clinical potential for ciliotherapy. Our studies further indicated that ciliotherapy provides a possibility toward personalized medicine in ciliopathy patients.

Plasma metabolites and lipids associate with kidney function and kidney volume in hypertensive ADPKD patients early in the disease course

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and is characterized by gradual cyst growth and expansion, increase in kidney volume with an ultimate decline in kidney function leading to end stage renal disease (ESRD). Given the decades long period of stable kidney function while cyst growth occurs, it is important to identify those patients who will progress to ESRD. Recent data from our and other laboratories have demonstrated that metabolic reprogramming may play a key role in cystic epithelial proliferation resulting in cyst growth in ADPKD. Height corrected total kidney volume (ht-TKV) accurately reflects cyst burden and predicts future loss of kidney function. We hypothesize that specific plasma metabolites will correlate with eGFR and ht-TKV early in ADPKD, both predictors of disease progression, potentially indicative of early physiologic derangements of renal disease severity.

Methods

To investigate the predictive role of plasma metabolites on eGFR and/or ht-TKV, we used a non-targeted GC-TOF/MS-based metabolomics approach on hypertensive ADPKD patients in the early course of their disease. Patient data was obtained from the HALT-A randomized clinical trial at baseline including estimated glomerular filtration rate (eGFR) and measured ht-TKV. To identify individual metabolites whose intensities are significantly correlated with eGFR and ht-TKV, association analyses were performed using linear regression with each metabolite signal level as the primary predictor variable and baseline eGFR and ht-TKV as the continuous outcomes of interest, while adjusting for covariates. Significance was determined by Storey’s false discovery rate (FDR) q-values to correct for multiple testing.

Results

Twelve metabolites significantly correlated with eGFR and two triglycerides significantly correlated with baseline ht-TKV at FDR q-value < 0.05. Specific significant metabolites, including pseudo-uridine, indole-3-lactate, uric acid, isothreonic acid, and creatinine, have been previously shown to accumulate in plasma and/or urine in both diabetic and cystic renal diseases with advanced renal insufficiency.

Conclusions

This study identifies metabolic derangements in early ADPKD which may be prognostic for ADPKD disease progression.

Clinical trial

HALT Progression of Polycystic Kidney Disease (HALT PKD) Study A; Clinical www.clinicaltrials.gov identifier: NCT00283686; first posted January 30, 2006, last update posted March 19, 2015.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1249-6) contains supplementary material, which is available to authorized users.

A Case Report: Successful Management of an Aortic Saddle Embolism in a 28-Year-Old Female

The obstruction of blood flow at the aortic bifurcation by an embolus defines aortic saddle embolism (ASE). This rare entity occurs preferentially in individuals with cardiovascular diseases such as the middle aged and the elderly. Conversely, its occurrence is sporadic in younger patients. As a result, the diagnosis of ASE is often overlooked or delayed in this age group; therefore, putting these patients at significant risk of neurologic impairment and potential limb loss. Following an extensive literature review, we have found only one reported case of ASE in a patient younger than 30 years. This patient died within 24 hours of admission and was diagnosed with ASE at autopsy. Here, we report for the first time, a case of a successful management of an ASE in a 28-year-old female who presented at our emergency room with acute weakness and numbness of the lower extremities. After vascular consult, the diagnosis of ASE was made and the patient was treated successfully. A week later, the patient was discharged home in stable condition without complications. The purpose of this report is to raise awareness about this potentially fatal condition and emphasize the importance of rapid assessment and treatment. The treatment options are heparin infusion, thrombolytic therapy, and embolectomy.

Understanding the physical and emotional impact of early-stage ADPKD: experiences and perspectives of patients and physicians

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder; however, at the time this research was conducted, no disease-modifying treatment was currently available. Medical texts often describe early-stage disease (Stages 1 and 2) as asymptomatic, but there is evidence from patients of considerable physical and emotional effects.

Methods

In-depth interviews were conducted with 80 ADPKD patients, 72 nephrologists and 85 primary care physicians (PCPs) from nine European countries to explore the experience and impact of early-stage ADPKD. Interviews were transcribed, translated and analysed centrally using thematic analysis. An additional 600 physicians completed standardised online questionnaires to investigate perceptions of symptom severity and management of early-stage ADPKD.

Results

Eighty-eight per cent of patients with early-stage disease reported physical symptoms including pain, fatigue, breathlessness, weakness and a general malaise. However, 24% of nephrologists and 16% of PCPs perceived that the patients with early-stage disease did not experience any physical symptoms at all. There was a greater awareness of the emotional impact of disease, but this was still underestimated when compared with patient-reported experiences, which highlighted widespread feelings of loss, uncertainty and fear.

Patients and physicians experienced frustration due to the lack of treatment options, especially in the long latent period. For many patients, the inability to affect their disease course whilst living with a diagnosis resulted in feelings of hopelessness, helplessness and depression. Physicians identified a need for improved cooperation between health-care professionals, and increased psychological support for patients.

Conclusions

Early-stage ADPKD can have a significant physical and emotional impact on patients. Whilst some physicians have an awareness of patient experience during early-stage disease, most underestimate the impact of ADPKD. Both patients and physicians are negatively affected by their inability to alter disease progression.

MicroRNAs in the pathogenesis of cystic kidney disease

PURPOSE OF REVIEW

Cystic kidney diseases are common renal disorders characterized by the formation of fluid-filled epithelial cysts in the kidneys. The progressive growth and expansion of the renal cysts replace existing renal tissue within the renal parenchyma, leading to reduced renal function. While several genes have been identified in association with inherited causes of cystic kidney disease, the molecular mechanisms that regulate these genes in the context of post-transcriptional regulation are still poorly understood. There is increasing evidence that microRNA (miRNA) dysregulation is associated with the pathogenesis of cystic kidney disease.

RECENT FINDINGS

In this review, recent studies that implicate dysregulation of miRNA expression in cystogenesis will be discussed. The relationship of specific miRNAs, such as the miR-17∼92 cluster and cystic kidney disease, miR-92a and von Hippel-Lindau syndrome, and alterations in LIN28-LET7 expression in Wilms tumor will be explored.

SUMMARY

At present, there are no specific treatments available for patients with cystic kidney disease. Understanding and identifying specific miRNAs involved in the pathogenesis of these disorders may have the potential to lead to the development of novel therapies and biomarkers.

The effect of tolvaptan on autosomal dominant polycystic kidney disease patients: a subgroup analysis of the Japanese patient subset from TEMPO 3:4 trial

BACKGROUND

Japan is the first country in the world to approve tolvaptan for the treatment of autosomal dominant polycystic kidney disease (ADPKD), which was based on the results of Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes (TEMPO) 3:4 trial. To evaluate the safety and efficacy of tolvaptan, we performed a subgroup analysis in the participating Japanese ADPKD patient population.

METHODS

The primary outcome was the annual rate of percentage change in the total kidney volume (TKV). The secondary endpoint was the rate of kidney function change.

RESULTS

The tolvaptan and placebo groups included 118 and 59 patients, respectively. The annual rate of percentage changes in TKV were 1.3 % [95 % confidence interval (CI) 0.4-2.1] in the tolvaptan group, and 5.0 % (95 % CI 3.9-6.2) in the placebo group (P < 0.001). The annual estimated glomerular filtration rate change was -3.83 mL/min/1.73 m(2) in the tolvaptan group and -5.05 mL in the placebo group for a treatment effect of +1.22 mL/min/1.73 m(2) (95 % CI 0.41-2.02: P = 0.003). Hepatic function abnormal as a serious adverse event was observed in 3 patients (2.5 %) in the tolvaptan group.

CONCLUSIONS

Administration of tolvaptan in the Japanese sub-population reduced the annual rate of TKV growth and slowed the rate of kidney function decline over 36 months compared to patients on placebo, thus providing a novel and effective therapy for the treatment of ADPKD. (TEMPO 3:4 ClinicalTrials.gov number, NCT00428948).

Combined liver and kidney transplant in a patient with budd-Chiari syndrome secondary to autosomal dominant polycystic kidney disease associated with polycystic liver disease: report of a case with a 9-year follow-up

Polycystic liver disease (PLD) is a hereditary disease inherited by autosomal dominant trait that occurs as a frequent extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). We report a case of a 59-year-old woman diagnosed with ADPKD associated with PLD. End-stage chronic renal failure with a secondary Budd-Chiari syndrome developed during the patient's clinical course. She underwent combined liver and kidney transplantation, with a successful response over a 9-year follow-up period.

Nontraumatic subarachnoid hemorrhage in maintenance dialysis hospitalizations: trends and outcomes

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) is associated with high mortality, and patients on maintenance dialysis have been shown to be at higher risk for stroke including SAH. However, the outcomes of patients on maintenance dialysis with SAH are not well known. This study was designed to look at incidence and outcomes of SAH in those on maintenance dialysis.

METHODS

Using the Nationwide Inpatient Sample Database, hospitalizations with nontraumatic SAH were identified. Age-adjusted incidence rates were calculated by direct standardization to the 2000 US standard population. Logistic regression was used to assess the risk factors for mortality.

RESULTS

Of an estimated 149,091 hospitalizations with SAH, 1631 patients (10.9%) were on maintenance dialysis. Unadjusted incidence of SAH hospitalizations was higher in maintenance dialysis than in the general population (73.5 versus 11.2 per 100,000 population), and similar results were seen on age-adjusted analysis. The unadjusted all-cause inpatient mortality rate for SAH admissions was higher in maintenance dialysis versus the general population (38.4% versus 21.9%; P<0.001). Maintenance dialysis was an independent predictor of mortality (odds ratio, 2.48; 95% confidence interval, 1.85-3.34), although other significant predictors of mortality were similar in both subgroups. Incidence of SAH hospitalizations has been relatively stable during the study period, but mortality seems to be decreasing.

CONCLUSIONS

SAH hospitalizations are more common and associated with higher mortality in patients on maintenance dialysis than in the general population. Although being on maintenance dialysis is an independent predictor for mortality in patients with SAH, other predictors of mortality evaluated in this study are not necessarily different between the 2 groups.

TRP channels

TRP channels constitute a large superfamily of cation channel forming proteins, all related to the gene product of the transient receptor potential (trp) locus in Drosophila. In mammals, 28 different TRP channel genes have been identified, which exhibit a large variety of functional properties and play diverse cellular and physiological roles. In this article, we provide a brief and systematic summary of expression, function, and (patho)physiological role of the mammalian TRP channels.

Reduced ciliary polycystin-2 in induced pluripotent stem cells from polycystic kidney disease patients with PKD1 mutations

Heterozygous mutations in PKD1 or PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively, cause autosomal dominant PKD (ADPKD), whereas mutations in PKHD1, which encodes fibrocystin/polyductin (FPC), cause autosomal recessive PKD (ARPKD). However, the relationship between these proteins and the pathogenesis of PKD remains unclear. To model PKD in human cells, we established induced pluripotent stem (iPS) cell lines from fibroblasts of three ADPKD and two ARPKD patients. Genetic sequencing revealed unique heterozygous mutations in PKD1 of the parental ADPKD fibroblasts but no pathogenic mutations in PKD2. Undifferentiated PKD iPS cells, control iPS cells, and embryonic stem cells elaborated primary cilia and expressed PC1, PC2, and FPC at similar levels, and PKD and control iPS cells exhibited comparable rates of proliferation, apoptosis, and ciliogenesis. However, ADPKD iPS cells as well as somatic epithelial cells and hepatoblasts/biliary precursors differentiated from these cells expressed lower levels of PC2 at the cilium. Additional sequencing confirmed the retention of PKD1 heterozygous mutations in iPS cell lines from two patients but identified possible loss of heterozygosity in iPS cell lines from one patient. Furthermore, ectopic expression of wild-type PC1 in ADPKD iPS-derived hepatoblasts rescued ciliary PC2 protein expression levels, and overexpression of PC1 but not a carboxy-terminal truncation mutant increased ciliary PC2 expression levels in mouse kidney cells. Taken together, these results suggest that PC1 regulates ciliary PC2 protein expression levels and support the use of PKD iPS cells for investigating disease pathophysiology.

Surgical cyst decortication in autosomal dominant polycystic kidney disease

PURPOSE

To provide a summary of the relevant literature regarding the impact of surgical cyst decortication on hypertension, renal function, and pain management in patients with autosomal dominant polycystic kidney disease (ADPKD).

METHODS

Data collection was conducted via a Medline search using the subject headings autosomal dominant polycystic kidney disease, surgery, decortication, and marsupialization. Additional reports were derived from references included within these articles.

RESULTS

Despite a trend for improved blood pressure control after cyst decortication in some studies, this cumulative review of the literature did not provide consistent evidence supporting the role of this procedure in blood pressure management in patients with ADPKD. Surgical cyst decortication was associated with renal deterioration in a subset of patients with compromised baseline renal function but did not otherwise appear to have a significant impact on renal function in the majority of studies reviewed. Improvement in chronic pain after this procedure was ubiquitously reported across all studies examined.

CONCLUSIONS

Despite a potential role in blood pressure management in the setting of ADPKD, surgical cyst decortication has not been definitively shown to alleviate hypertension in this clinical setting. Renal function does not appear to improve following this surgery. Patients with compromised baseline renal function appear to be at increased risk for further deterioration in renal function after cyst decortication, although the role of this procedure in altering the natural trajectory of renal failure in this patient subset needs further investigation. Cyst decortication is highly effective in the management of disease-related chronic pain for the majority of patients with ADPKD, providing durable pain relief in this patient population.

A comparison of the effects of losartan and ramipril on blood pressure, renal volume and progression in polycystic kidney disease: A 5-Year follow-up

BACKGROUND

The major cause of hereditary renal failure is autosomal dominant polycystic kidney disease (ADPKD). Many factors affect renal progression in these patients. Among these, hypertension and an increase in renal volume are interrelated in terms of their effects on renal progression. We aimed to investigate the effects of losartan and ramipril on renal volume and progression in patients with ADPKD.

MATERIALS AND METHODS

Data from 18 hypertensive patients with ADPKD were evaluated. Eleven of the 18 hypertensive patients were on losartan and 7 on ramipril treatment. Demographic parameters, use of antihypertensives and other medications, the course of blood pressure (BP), biochemical parameters, creatinine clearance (CrCL), findings at computed tomography and renal volume were recorded at baseline and at 1 and 5 years.

RESULTS

Target BP values were maintained over 5 years. The annual decrease in CrCL was 1.33 mL/min in the losartan group compared with 6.59 mL/min in the ramipril group. There was no significant difference between the groups in terms of annual decrease in CrCL. Annual increase in renal volume was 252.04 cm³ in the losartan group and 167.36 cm³ in the ramipril group. There was no significant difference between the groups in terms of the increase in renal volumes at 1 and 5 years.

CONCLUSION

Our study demonstrated that losartan and ramipril provided effective BP control. In addition, the results of our study demonstrated that despite the increase in renal volume, losartan and ramipril may have regressed renal progression via other factors.

Human Evaluation of the Glu298Asp Polymorphism in NOS3 Gene and its Relationship with Onset age of ESRD in Iranian Patients Suffering from ADPKD

One of the most striking features in autosomal dominant polycystic kidney disease (ADPKD) is the difference at onset age of end-stage renal disease (ESRD). Modifier genes may play a role in this phenotypic variability. The mutated nitric oxide synthase 3 gene (NOS3), have a modifier effect on the severity of ADPKD by impairment of NOS3 activity and decreasing of renal vascular nitric oxide production and, subsequently, reduced kidney function. In order to test this hypothesis, we investigated the relationship between Glu298Asp polymorphism in exon 7 of this gene and ESRD in ADPKD patients refered from Shahid Labbafi Nedjad Hospital in Tehran. The polymorphism was examined by PCR, followed by RFLP (with MboI) in three groups of ADPKD with ESRD; ADPKD without ESRD patients and normal individual as the cases, case-controls and controls, respectively. The frequencies of GG, GT, and TT genotypes in cases were 66.7%, 33.3% and 0%, in case-controls were 78.6%, 19%, 2.4%, and in controls were 64.3%, 35.7% and 0%, respectively. Our findings revealed that there was no significant difference in the genotype frequency of NOS3 gene in ADPKD patients (p=0.311).The age of onset of ESRD in ADPKD patients, harbouring the T allele of this polymorphism, was two years lower than G/G patients, but this difference was not significant (p =0.641). In conclusion, our results suggest that there is no evidence of relationship between Glu298Asp polymorphism and onset age of ESRD in Iranian ADPKD patients.

The mechanosensory role of primary cilia in vascular hypertension

Local regulation of vascular tone plays an important role in cardiovascular control of blood pressure. Aside from chemical or hormonal regulations, this local homeostasis is highly regulated by fluid-shear stress. It was previously unclear how vascular endothelial cells were able to sense fluid-shear stress. The cellular functions of mechanosensory cilia within vascular system have emerged recently. In particular, hypertension is insidious and remains a continuous problem that evolves during the course of polycystic kidney disease (PKD). The basic and clinical perspectives on primary cilia are discussed with regard to the pathogenesis of hypertension in PKD.

Clinical and molecular insights into tuberous sclerosis complex renal disease

Patients with tuberous sclerosis complex are at great risk of developing renal lesions as part of their disease. These lesions include renal cysts and tumors. Significant advances in understanding the cell biology of these renal lesions has already led to clinical trials demonstrating that pharmacological interventions are likely possible. This review focuses on the pathology of these renal lesions, their underlying cell biology, and the possible therapeutic strategies that may prove to significantly improve care for these patients.

Unraveling the role of polycystin-2/inositol 1,4,5-trisphosphate receptor interaction in Ca signaling

Autosomal dominant polycystic kidney disease (ADPKD) arises as a consequence of mutations of the genes PKD1 and PKD2, encoding respectively the integral membrane proteins polycystin-1 and polycystin-2 (TRPP2), resulting in a disturbance in intracellular Ca(2+) signaling. Previously we investigated the interaction between TRPP2 and the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R), an intracellular Ca(2+) channel in the endoplasmic reticulum (ER). We identified the molecular determinants of this interaction and observed an enhanced IP(3)-induced Ca(2+) release (IICR). Since we found that TRPP2 strongly bound to a cluster of positively charged amino acids in the N-terminal ligand-binding domain (LBD) of the IP(3)R, we now investigated whether TRPP2 would interfere with the binding of IP(3) to the IP(3)R. In in vitro experiments we observed that TRPP2 partially inhibited the binding of IP(3) to the LBD of the IP(3)R with an IC(50) of ∼350 nM. The suppressor domain, i.e., the N-terminal 225 amino acids of the LBD of the IP(3)R, mediated this inhibitory effect of TRPP2 on IP(3) binding. The observation that the interaction between the IP(3)R and TRPP2 decreased IP(3) binding is in apparent contrast to the increased IICR. The data can be explained however by a subsequent activation of Ca(2+)-induced Ca(2+) release (CICR) via TRPP2. Implications of this mechanism for cellular Ca(2+) signaling are discussed in this addendum.

Chronic treatment with lisinopril decreases proliferative and apoptotic pathways in autosomal recessive polycystic kidney disease

Angiotensin converting enzyme (ACE) inhibition is a common therapeutic modality in the treatment of autosomal recessive polycystic kidney disease (ARPKD). This study was designed to investigate whether chronic inhibition of ACE would have a therapeutic effect in attenuating the progression of renal cystogenesis in an orthologous rat model of ARPKD, the polycystic kidney (PCK) rat. Lisinopril (3 mg/kg per day) was administered orally for a period of 12 weeks, beginning at post-natal week 4. Lisinopril treatment resulted in an approximately 30% improvement in the collecting duct cystic indices (CT CI) of PCK animals. Activation of extracellular signal-regulated kinase 1 (ERK1) and 2 (ERK2), proliferative signaling markers, and proliferating cell nuclear antigen (PCNA), an end-point marker for proliferation, was reduced following chronic treatment with lisinopril compared to that in vehicle-treated PCK rats. To assess whether apoptotic pathways were altered due to chronic ACE inhibition, we examined p38 mitogen activated protein kinase (MAPK) and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), which are markers of apoptotic signaling cascades. p38 MAPK was significantly reduced (P < 0.0001) following chronic treatment with lisinopril, but no change in the activation of SAPK/JNK could be detected by immunoblot analysis. Lisinopril treatment resulted in a significant reduction (P < 0.01) in cleaved caspase-7 levels, but not caspase-3 activity, in PCK rat kidneys compared to the vehicle-treated PCK rat kidneys. Proteinuria was completely ameliorated in the presence of chronic ACE inhibition in the lisinopril-treated rats compared with the vehicle-treated PCK rats. In all, these findings demonstrated that chronic ACE inhibition can beneficially alter proliferative and apoptotic pathways to promote therapeutic reductions in renal cyst development in ARPKD.

Hypertension in Autosomal Dominant Polycystic Kidney Disease: A Clinical and Basic Science Perspective

Cardiovascular complications are major causes of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). In particular, hypertension is insidious and remains a continuous problem that evolves during the course of the disease. Hypertension in ADPKD has been associated with abnormality in the renin-angiotensin-aldosterone system (RAAS). Early vascular changes have also been reported in young ADPKD patients. In addition, the cellular functions of mechanosensory cilia within vascular system have emerged recently. The basic and clinical perspectives of RAAS, vascular remodeling and sensory cilia are reviewed with regard to hypertension in ADPKD.

Autosomal dominant polycystic kidney disease: the last 3 years

Autosomal dominant polycystic kidney disease is the most prevalent, potentially lethal monogenic disorder. It has large inter- and intra-familial variability explained to a large extent by its genetic heterogeneity and modifier genes. An increased understanding of its underlying genetic, molecular, and cellular mechanisms and a better appreciation of its progression and systemic manifestations have laid out the foundation for the development of clinical trials and potentially effective therapies. The purpose of this review is to update the core of knowledge in this area with recent publications that have appeared during 2006-2009.