Familial clustering of ruptured intracranial aneurysms in autosomal dominant polycystic kidney disease

TRPP2 ion channels: The roles in various subcellular locations

TRPP2 (PC2, PKD2 or Polycytin-2), encoded by PKD2 gene, belongs to the nonselective cation channel TRP family. Recently, the three-dimensional structure of TRPP2 was constructed. TRPP2 mainly functions in three subcellular compartments: endoplasmic reticulum, plasma membrane and primary cilia. TRPP2 can act as a calcium-activated intracellular calcium release channel on the endoplasmic reticulum. TRPP2 also interacts with other Ca²⁺ release channels to regulate calcium release, like IP3R and RyR2. TRPP2 acts as an ion channel regulated by epidermal growth factor through activation of downstream factors in the plasma membrane. TRPP2 binding to TRPC1 in the plasma membrane or endoplasmic reticulum is associated with mechanosensitivity. In cilium, TRPP2 was found to combine with PKD1 and TRPV4 to form a complex related to mechanosensitivity. Because TRPP2 is involved in regulating intracellular ion concentration, TRPP2 mutations often lead to autosomal dominant polycystic kidney disease, which may also be associated with cardiovascular disease. In this paper, we review the molecular structure of TRPP2, the subcellular localization of TRPP2, the related functions and mechanisms of TRPP2 at different sites, and the diseases related to TRPP2.

Cardiac Involvement in Autosomal Dominant Polycystic Kidney Disease

Cardiovascular disorders are the main complication in autosomal dominant polycystic kidney disease (ADPKD). contributing to both morbidity and mortality. This review considers clinical studies unveiling cardiovascular features in patients with ADPKD. Additionally, it focuses on basic science studies addressing the dysfunction of the polycystin proteins located in the cardiovascular system as a contributing factor to cardiovascular abnormalities. In particular, the effects of polycystin proteins’ deficiency on the cardiomyocyte function have been considered.

Cerebral Aneurysms in Autosomal Dominant Polycystic Kidney Disease: A Comparison of Management Approaches

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a risk factor for formation of intracranial aneurysms (IAs), though the ideal screening and treatment strategies in this population are unclear.

OBJECTIVE

To report outcomes of observation, open surgical, or endovascular management of ruptured and unruptured aneurysms in patients with ADPKD.

METHODS

We performed a retrospective analysis of all patients with ADPKD and IAs at a single center from 2000 to 2016.

RESULTS

Forty-five patients with ADPKD harboring 71 aneurysms were identified, including 11 patients with subarachnoid hemorrhage (SAH). Of 22 aneurysms managed with observation, none ruptured in 136 yr of clinical follow-up. Thirty-five aneurysms were treated with open surgery and 14 with an endovascular approach. Among treated aneurysms, poor neurologic outcome (modified Rankin scale >2) was seen only in patients presenting with SAH (17% SAH vs 0% elective, P = .06). Acute kidney injury (AKI) was also significantly associated with SAH presentation (22% SAH vs 0% elective, P = .05). Neither procedural complications nor AKI were associated with treatment modality. Among 175 yr of radiographic follow-up in patients with known IAs, 8 de novo aneurysms were found, including 3 that were treated. Of 11 patients with SAH, 7 ruptured in the setting of previously known ADPKD, including 2 with prior angiographic screening and 5 without screening.

CONCLUSION

Poor outcomes occurred only with ruptured presentation but were equivalent between treatment modalities. Screening is performed only selectively, and 64% (7 of 11) of patients presenting with SAH had previously known ADPKD.

Polycystic kidney disease

Cystic kidneys are common causes of end-stage renal disease, both in children and in adults. Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are cilia-related disorders and the two main forms of monogenic cystic kidney diseases. ADPKD is a common disease that mostly presents in adults, whereas ARPKD is a rarer and often more severe form of polycystic kidney disease (PKD) that usually presents perinatally or in early childhood. Cell biological and clinical research approaches have expanded our knowledge of the pathogenesis of ADPKD and ARPKD and revealed some mechanistic overlap between them. A reduced 'dosage' of PKD proteins is thought to disturb cell homeostasis and converging signalling pathways, such as Ca²⁺, cAMP, mechanistic target of rapamycin, WNT, vascular endothelial growth factor and Hippo signalling, and could explain the more severe clinical course in some patients with PKD. Genetic diagnosis might benefit families and improve the clinical management of patients, which might be enhanced even further with emerging therapeutic options. However, many important questions about the pathogenesis of PKD remain. In this Primer, we provide an overview of the current knowledge of PKD and its treatment.

A Large Database Analysis of Rates of Aneurysm Screening, Elective Treatment, and Subarachnoid Hemorrhage in Patients With Polycystic Kidney Disease

BACKGROUND

Professional societies provide conflicting guidelines on aneurysm screening in patients with polycystic kidney disease (PKD), and the rate of subarachnoid hemorrhage (SAH) is poorly understood.

OBJECTIVE

To evaluate screening, elective treatment, and the rate of SAH in patients with known PKD.

METHODS

We examined longitudinally linked claims data from a large private insurer, identifying screening, elective treatment, aneurysmal subarachnoid hemorrhage (aSAH) and secured aneurysmal SAH (saSAH) in 2004 to 2014 amongst patients with known PKD.

RESULTS

We identified 20 704 patients diagnosed with PKD. Among patients with an initial PKD diagnosis, 51/446 (15.9%) underwent angiographic screening within 2 yr. Forty aneurysms were treated electively in 48 868 yr at risk in PKD patients (82/100K patient yr, 95% confidence interval [CI] 60-112) vs 24 elective treatments in 349 861 yr at risk in age- and sex-matched controls (7/100K patient yr, 95% CI 5-10, P < .0001). Eleven admissions for aSAH were identified in PKD patients (23/100K patient yr, 95% CI 13-41) and 22 admissions for aSAH in controls (6/100K patient yr, 95% CI 4-10), giving an incidence rate ratio (IRR) of 3.6 (95% CI 1.7-7.4, P < .0001) and a comorbidity-adjusted IRR of 3.1 (95% CI 1.4-6.9). The incidence of saSAH was proportionally even higher in PKD patients than controls, 16 vs 2/100K patient years, IRR 9.5 (95% CI 3.3-27.5, P < .0001).

CONCLUSION

Screening in PKD is performed only selectively, though resulting rates of elective treatment were over 10× those of controls. Despite screening and treatment, the rate of SAH remains significantly elevated over that of controls.

Surgical Outcome of Cerebral Aneurysm Clipping Treated with Immunosuppressants: Report of 11 Cases and Review of the Literature

There are no reports on the outcomes of clippings in patients who receive immunosuppressants, for example, due to connective tissue diseases or following organ transplantation. We thoroughly reviewed these cases focusing on the perioperative management phase. The study included 11 patients with intracranial aneurysms who were taking immunosuppressants; between 2007 and 2014. We performed 12 clipping surgeries. Their clinical records were reviewed for age and gender, aneurysms' location and size, perioperative management of the immunosuppressive drugs, and surgical complications. The study included nine females and two males, aged between 52 and 71 years (mean 60.1 ± 8.5 years). The clinical presentation in five cases was subarachnoid hemorrhage (SAH); the aneurysm was incidentally diagnosed in six patients (7 aneurysms). The reasons for taking immunosuppressants were autoimmune disorder in nine patients and liver transplantation in two patients. Daily intake of oral immunosuppressants for the patients with liver transplantation was discontinued for 2-4 days, and no infectious complications were evidenced. The weekly course of immunosuppressive drugs for the patients with autoimmune disorder was continued in eight of nine patients. Caution must be exercised when considering the suitability of clipping for patients taking immunosuppressants, but surgery outcomes are generally favorable; when operative treatment is required, we believe it to be comparatively safe, if the perioperative management is conducted in close collaboration with the relevant departments.

Screening for Unruptured Intracranial Aneurysms in Autosomal Dominant Polycystic Kidney Disease: A Survey of 420 Nephrologists

Background

Despite a high prevalence of intracranial aneurysm (ICA) in autosomal dominant polycystic kidney disease (ADPKD), rupture events are rare. The current recommendations for ICA screening are based on expert opinions and studies with low levels of evidence.

Objectives

The aim of our study was to describe the attitudes of practicing nephrologists in Europe towards screening for ICA using magnetic resonance angiography (MRA).

Methods

We conducted a web-based survey among 1315 European French-speaking nephrologists and nephrology residents. An anonymous, electronic questionnaire including 24 independent questions related to ICA screening modalities, indications and participant profiles was sent by email between September and December 2014. Four hundred and twenty nephrologists (mostly from France) participated, including 31 nephrology residents; the response rate was 32%.

Results

Systematic screening for ICA was advocated by 28% of the nephrologists. A family history of ICA rupture, sudden death, stroke and migraine were consensual indications for screening (> 90% of the panel). In other clinical situations largely not covered by the recommendations (pregnancy, nephrectomy, kidney transplantation, cardiac or hepatic surgery, uncontrolled hypertension, lack of familial ADPKD history, at-risk activity, tobacco use), the attitudes towards screening were highly divergent. ICA screening was influenced by nephrologists experience with ADPKD and by their practice setting. The majority of participants (57%) would not repeat a normal ICA screening. Only a few participants (22%) knew that non-contrast MRA was the reference diagnostic tool for ICA screening, whereas most participants thought that contrast enhancement was necessary to screen for ICA. The results from the nephrology residents were analyzed separately and yielded similar results.

Conclusion

This practice survey revealed that most nephrologists follow the current recommendations for the initial screening of ICAs. However, more than a quarter of the panel was in favor of systematic ICA screening, most nephrologists did not know that contrast medium was not necessary to screen for ICA using MRA, and many areas of uncertainty remain.

Sudden death due to subarachnoid haemorrhage in an infant with autosomal dominant polycystic kidney disease

Intracranial aneurysm rupture is the most serious and potentially lethal extra-renal manifestation of autosomal dominant polycystic kidney disease (ADPKD). Almost all cases of ruptured intracranial aneurysm occur in adult patients with a median age of rupture of 40 years. We report the occurrence of sudden death in a newborn infant born to a mother with typical ADPKD in the first week of life. Post-mortem examination revealed the cause of death to be subarachnoid haemorrhage with focal glomerular and tubular cysts detected in the kidney. This is the earliest reported case of intracranial aneurysm rupture in ADPKD and should raise awareness of this rare but lethal complication in younger patients.

Translational research in ADPKD: lessons from animal models

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2, which encode polycystin-1 and polycystin-2, respectively. Rodent models are available to study the pathogenesis of polycystic kidney disease (PKD) and for preclinical testing of potential therapies-either genetically engineered models carrying mutations in Pkd1 or Pkd2 or models of renal cystic disease that do not have mutations in these genes. The models are characterized by age at onset of disease, rate of disease progression, the affected nephron segment, the number of affected nephrons, synchronized or unsynchronized cyst formation and the extent of fibrosis and inflammation. Mouse models have provided valuable mechanistic insights into the pathogenesis of PKD; for example, mutated Pkd1 or Pkd2 cause renal cysts but additional factors are also required, and the rate of cyst formation is increased in the presence of renal injury. Animal studies have also revealed complex genetic and functional interactions among various genes and proteins associated with PKD. Here, we provide an update on the preclinical models commonly used to study the molecular pathogenesis of ADPKD and test potential therapeutic strategies. Progress made in understanding the pathophysiology of human ADPKD through these animal models is also discussed.

An autopsy case of subarachnoid hemorrhage due to ruptured cerebral aneurysm associated with polycystic kidney disease caused by a novel PKD1 mutation

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic disorders and is characterized by the development and progressive enlargement of cysts in the kidneys. ADPKD is caused by mutations of either PKD1 or PKD2. The prevalence of brain aneurysm in patients with ADPKD is increased, and subarachnoid hemorrhage (SAH) from a ruptured intracranial aneurysm is one of the frequent complications. We describe an autopsy case of death of a 31-year-old woman by aneurysmal SAH. ADPKD as an underlining disease was suggested by the autopsy findings. Sequence analysis of the PKD1 and PKD2 genes revealed deletion of a guanine at position 8019 in PKD1 (8019delG) in a heterozygous state resulting in a shift in the reading frame and generation of a premature termination codon at amino acid 2684 (G2673fs12X). This mutation is novel and highly suspected as the causal mutation of ADPKD of this case.

Predictors of autosomal dominant polycystic kidney disease progression

Autosomal dominant polycystic kidney disease is a genetic disorder associated with substantial variability in its natural course within and between affected families. Understanding predictors for rapid progression of this disease has become increasingly important with the emergence of potential new treatments. This systematic review of the literature since 1988 evaluates factors that may predict and/or effect autosomal dominant polycystic kidney disease progression. Predicting factors associated with early adverse structural and/or functional outcomes are considered. These factors include PKD1 mutation (particularly truncating mutation), men, early onset of hypertension, early and frequent gross hematuria, and among women, three or more pregnancies. Increases in total kidney volume and decreases in GFR and renal blood flow greater than expected for a given age also signify rapid disease progression. Concerning laboratory markers include overt proteinuria, macroalbuminuria, and perhaps, elevated serum copeptin levels in affected adults. These factors and others may help to identify patients with autosomal dominant polycystic kidney disease who are most likely to benefit from early intervention with novel treatments.

Risk of intracranial hemorrhage associated with autosomal dominant polycystic kidney disease in patients with end stage renal disease

BACKGROUND

An analysis of intracranial hemorrhage (ICH) in a national sample of autosomal dominant polycystic kidney disease (ADPKD) patients receiving long-term dialysis has not been reported. It is often assumed that patients with ADPKD are not at increased risk of ICH after starting dialysis. We hypothesized that patients with ADPKD would have a higher subsequent risk of ICH even after the start of chronic dialysis.

METHODS

Retrospective cohort study of Medicare primary patients with and without ADPKD in the United States Renal Data System (USRDS), initiated on chronic dialysis or transplanted between 1 January 1999 and 3 July 2009, and followed until 31 December 2009. Covariates included age, gender, race, prior stroke, diabetes mellitus, dialysis modality, body mass index, serum albumin and other co-morbid conditions from the Medical Evidence Form. Primary outcome was ICH, based on inpatient and outpatient Medicare claims, and all-cause mortality. Kaplan-Meier analysis was used for unadjusted assessment of time to events. Cox regression was used for assessment of factors associated with ICH and mortality. We performed competing risk regression using kidney transplant and death as competing risks. Kidney transplant was also modeled as a time-dependent covariate in Cox regression.

RESULTS

Competing risk regression demonstrated that ADPKD had a subhazard ratio 2.97 for ICH (95% CI 2.27-3.89). Adjusted Cox analysis showed that ADPKD patients had an AHR for death of 0.59 vs. non-ADPKD patients (95% CI 0.57-0.61).

CONCLUSIONS

ADPKD is a significant risk factor for ICH among patients on maintenance dialysis. Our Medicare primary cohort was older than in previous studies of intracranial aneurysm rupture among ADPKD patients. There are also limitations inherent to using the USRDS database.

Extra-renal manifestations of autosomal dominant polycystic kidney disease (ADPKD): considerations for routine screening and management

Autosomal-dominant polycystic kidney disease (ADPKD) is a systemic disease, marked by progressive increase of bilateral renal cysts, resulting in chronic kidney disease (CKD) and often leading to end-stage renal disease (ESRD). Apart from renal cysts, patients often have extra-renal disease, involving the liver, heart and vasculature. Other less common but equally important extra-renal manifestations of ADPKD include diverticular disease, hernias, male infertility and pain. Extra-renal disease burden is often asymptomatic, but may result in increased morbidity and mortality. If the disease burden is significant, screening may prove beneficial. We review the rationale for current screening recommendations and propose some guidelines for screening and management of ADPKD patients.

ADPKD: Prototype of Cardiorenal Syndrome Type 4

The cardiorenal syndrome type 4 (Chronic Renocardiac Syndrome) is characterized by a condition of primary chronic kidney disease (CKD) that leads to an impairment of the cardiac function, ventricular hypertrophy, diastolic dysfunction, and/or increased risk of adverse cardiovascular events. Clinically, it is very difficult to distinguish between CRS type 2 (Chronic Cardiorenal Syndrome) and CRS type 4 (Chronic Renocardiac Syndrome) because often it is not clear whether the primary cause of the syndrome depends on the heart or the kidney. Autosomal dominant polycystic kidney disease (ADPKD), a genetic disease that causes CKD, could be viewed as an ideal prototype of CRS type 4 because it is certain that the primary cause of cardiorenal syndrome is the kidney disease. In this paper, we will briefly review the epidemiology of ADPKD, conventional and novel biomarkers which may be useful in following the disease process, and prevention and treatment strategies.

Polycystic kidney disease: inheritance, pathophysiology, prognosis, and treatment

Both autosomal dominant and recessive polycystic kidney disease are conditions with severe associated morbidity and mortality. Recent advances in the understanding of the genetic and molecular pathogenesis of both ADPKD and ARPKD have resulted in new, targeted therapies designed to disrupt cell signaling pathways responsible for the abnormal cell proliferation, dedifferentiation, apoptosis, and fluid secretion characteristic of the disease. Herein we review the current understanding of the pathophysiology of these conditions, as well as the current treatments derived from our understanding of the mechanisms of these diseases.

Unruptured intracranial aneurysms: initial and follow-up screening

Subarachnoid hemorrhage (SAH) from a ruptured intracranial aneurysm is a devastating disease that causes death or severe disability in half of patients. Intracranial aneurysms are not present at birth but develop during life. Actively searching and treating intracranial aneurysms before rupture may prevent SAH as a result of these aneurysms. The prevalence of intracranial aneurysms is approximately 2% in the general population, but higher in subgroups such as patients who have survived an episode of SAH, persons with a family history of SAH and patients with polycystic kidney disease. Screening for intracranial aneurysms should be considered in these high-risk groups. Some of the intracranial aneurysms detected with screening will be too small to be treated, and may therefore be followed over time, which can cause anxiety in the patient. In this article, we discuss current knowledge, remaining questions and future perspectives in screening and follow-up imaging for unruptured intracranial aneurysms.

Determinants of renal disease variability in ADPKD

In common with other Mendelian diseases, the presentation and progression of autosomal dominant polycystic kidney disease (ADPKD) vary widely in the population. The typical course is of adult-onset disease with ESRD in the 6th decade. However, a small proportion has adequate renal function into the 9th decade, whereas others present with enlarged kidneys as neonates. ADPKD is genetically heterogeneous, and the disease gene is a major determinant of severity; PKD1 on average is associated with ESRD 20 years earlier than PKD2. The majority of PKD1 and PKD2 mutations are likely fully inactivating although recent studies indicate that some alleles retain partial activity (hypomorphic alleles). Homozygotes for such alleles are viable and in combination with an inactivating allele can result in early-onset disease. Hypomorphic alleles and mosaicism may also account for some cases with unusually mild disease. The degree of phenotypic variation detected in families indicates that genetic background influences disease severity. Genome-wide association studies are planned to map common variants associated with severity. Although ADPKD is a simple genetic disease, fully understanding the phenotypic variability requires consideration of influences at the genic, allelic, and genetic background level, and so, ultimately, it is complex.

Molecular diagnostics for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common nephropathy caused by mutations in either PKD1 or PKD2. Mutations in PKD1 account for approximately 85% of cases and cause more severe disease than mutations in PKD2. Diagnosis of ADPKD before the onset of symptoms is usually performed using renal imaging by either ultrasonography, CT or MRI. In general, these modalities are reliable for the diagnosis of ADPKD in older individuals. However, molecular testing can be valuable when a definite diagnosis is required in young individuals, in individuals with a negative family history of ADPKD, and to facilitate preimplantation genetic diagnosis. Although linkage-based diagnostic approaches are feasible in large families, direct mutation screening is generally more applicable. As ADPKD displays a high level of allelic heterogeneity, complete screening of both genes is required. Consequently, such screening approaches are expensive. Screening of individuals with ADPKD detects mutations in up to 91% of cases. However, only approximately 65% of patients have definite mutations with approximately 26% having nondefinite changes that require further evaluation. Collation of known variants in the ADPKD mutation database and systematic scoring of nondefinite variants is increasing the diagnostic value of molecular screening. Genic information can be of prognostic value and recent investigation of hypomorphic PKD1 alleles suggests that allelic information may also be valuable in some atypical cases. In the future, when effective therapies are developed for ADPKD, molecular testing may become increasingly widespread. Rapid developments in DNA sequencing may also revolutionize testing.

Cardiovascular abnormalities in autosomal-dominant polycystic kidney disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal-dominant polycystic kidney disease (ADPKD). Hypertension is a common early symptom of ADPKD, and occurs in approximately 60% of patients before renal function has become impaired. Hypertension is associated with an increased rate of progression to end-stage renal disease and is the most important potentially treatable variable in ADPKD. Left ventricular hypertrophy, which is a powerful, independent risk factor for cardiovascular morbidity and mortality, also occurs frequently in patients with ADPKD. Both hypertension and left ventricular hypertrophy have important roles in cardiovascular complications in these individuals. Moreover, biventricular diastolic dysfunction, endothelial dysfunction, increased carotid intima-media thickness, and impaired coronary flow velocity reserve are present even in young patients with ADPKD who have normal blood pressure and well-preserved renal function. These findings suggest that cardiovascular involvement starts very early in the course of ADPKD. Intracranial and extracranial aneurysms and cardiac valvular defects are other potential cardiovascular problems in patients with ADPKD. Early diagnosis and treatment of hypertension, with drugs that block the renin-angiotensin-aldosterone system, has the potential to decrease the cardiovascular complications and slow the progression of renal disease in ADPKD.

Developments in the management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent life- threatening, hereditary disease. ADPKD is more common than sickle cell anemia, cystic fibrosis, muscular dystrophy, hemophilia, Down's syndrome, and Huntington's disease combined. ADPKD is a multisystemic disorder characterized by the progressive development of renal cysts and marked renal enlargement. Structural and functional renal deterioration occurs in ADPKD patients and is the fourth leading cause of end-stage renal disease (ESRD) in adults. Aside from the renal manifestations, extrarenal structural abnormalities, such as liver cysts, cardiovascular abnormalities, and intracranial aneurysms may lead to morbidity and mortality. Recent studies have identified prognostic factors for progressive renal impairment including gender, race, age, proteinuria, hematuria, hypertension and increased left ventricular mass index (LVMI). Early diagnosis and better understanding of the pathophysiology of the disease provides the opportunity to aggressivly treat hypertension with renin-angiotensin-aldosterone system inhibitors and thereby potentially reduce LVMI, prevent cardiovascular morbidity and mortality and slow progression of the renal disease.

Risk of intracranial aneurysm bleeding in autosomal-dominant polycystic kidney disease

Patients with autosomal-dominant polycystic kidney disease (ADPKD) carry an increased risk of developing intracranial aneurysms. Bleeding from these sites is a significant complication with the events reported to cluster in some families. In this study we determined if individualized risk of aneurysm rupture can be estimated based on family history using a Bayesian random effects model. Previously reported data were used to define distributions and to construct a model that fit these data. Our results confirm that intracerebral aneurysm bleeding in ADPKD patients tends to cluster in families and that basic family history can provide a simple estimate of family-specific risk.

Cardiovascular characterization of Pkd2+/LacZ mice, an animal model for the autosomal dominant polycystic kidney disease type 2 (ADPKD2)

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2. Patients with ADPKD have an increased incidence of cardiac valve abnormalities and left ventricular hypertrophy. Systematic analyses of cardiovascular involvement have so far been performed only on genetically unclassified patients or on ADPKD1 patients, but not on genetically defined ADPKD2 patients. Even existing Pkd1 or Pkd2 mouse models were not thoroughly analyzed in this respect. Therefore, the aim of this project was the noninvasive functional cardiovascular characterization of a mouse model for ADPKD2.

METHODS

Pkd2(+/LacZ) mice and wildtype controls were classified into 8 groups with respect to gender, age and genotype. In addition, two subgroups of female mice were analyzed for cardiac function before and during advanced pregnancy. Doppler-echocardiographic as well as histological studies were performed.

RESULTS

Doppler-echocardiography did not reveal significant cardiovascular changes. Heart rate and left ventricular (LV) length, LV mass, LV enddiastolic and LV endsystolic diameters did not differ significantly among the various groups when comparing wildtype and knockout mice. There were no significant differences except for a tendency towards higher maximal early and late flow velocities over the mitral valve in old wildtype mice.

CONCLUSIONS

Non-invasive phenotyping using ultrasound did not reveal significant cardiovascular difference between adult Pkd2(+/LacZ) and WT mice. Due to the lack of an obvious renal phenotype in heterozygous mice, it is likely that in conventional ADPKD knock out mouse models severe cardiac problems appear too late to be identified during the reduced lifespan of the animals.

Optimal care of autosomal dominant polycystic kidney disease patients

Autosomal dominant polycystic kidney disease (ADPKD) is the most common life-threatening, hereditary disease. The prevalence of ADPKD is more common than Huntington disease, haemophilia, sickle cell disease, cystic fibrosis, myotonic dystrophy and Down syndrome combined. In recent years there have not only been advances in the understanding of the genetic and molecular events involved in ADPKD, but some diagnostic and therapeutic advances have also emerged. In the genetics area, the gene for PKD1 was localised to chromosome 16, is associated with polycystin-2 protein, and found to account for approximately 85% of patients with ADPKD. The gene for PKD2, found in chromosome 4, accounts for approximately 15% of ADPKD, and is associated with the polycystin-2 protein. While these genetic and molecular biology findings have stimulated a great deal of exciting basic research in ADPKD, therapies to decrease morbidity and mortality in ADPKD patients have yet to emerge from these findings. In contrast, the early diagnosis and treatment of hypertension with inhibitors of the renin-angiotensin-aldosterone system have the potential to decrease or prevent left ventricular hypertrophy cardiac complications and slow the progression of the renal disease.

Familial hypertensive intracerebral hemorrhage and autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a generalized disease known to be associated with intracranial aneurysms. Non-aneurysmal intracerebral hemorrhage (ICH) has also been reported in ADPKD. We report a familial clustering of ICH and symptomatic ADPKD. This pedigree had at least six affected family members who suffered from ADPKD, hypertension and non-aneurysmal ICH. The proband demonstrated ADPKD, hypertension and cerebral hemorrhage. To our knowledge, this is the first report of familial ICH in ADPKD, which may have underlying genetic and environmental etiologies.

Neurological complications in renal failure: a review

Neurological complications whether due to the uremic state or its treatment, contribute largely to the morbidity and mortality in patients with renal failure. Despite continuous therapeutic advances, many neurological complications of uremia, like uremic encephalopathy, atherosclerosis, neuropathy and myopathy fail to fully respond to dialysis. Moreover, dialytic therapy or kidney transplantation may even induce neurological complications. Dialysis can directly or indirectly be associated with dialysis dementia, dysequilibrium syndrome, aggravation of atherosclerosis, cerebrovascular accidents due to ultrafiltration-related arterial hypotension, hypertensive encephalopathy, Wernicke's encephalopathy, hemorrhagic stroke, subdural hematoma, osmotic myelinolysis, opportunistic infections, intracranial hypertension and mononeuropathy. Renal transplantation itself can give rise to acute femoral neuropathy, rejection encephalopathy and neuropathy in graft versus host disease. The use of immunosuppressive drugs after renal transplantation can cause encephalopathy, movement disorders, opportunistic infections, neoplasms, myopathy and progression of atherosclerosis. We address the clinical, pathophysiological and therapeutical aspects of both central and peripheral nervous system complications in uremia.

Genetics of cerebrovascular disorders

Physicians must be able to recognize stroke caused by a mendelian or mitochondrial disorder. Some genetic disorders such as sickle cell anemia and Fabry disease have proven disease-specific treatments, whereas others have no effective treatment, including cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Proper diagnosis of a genetic disorder has prognostic value and prevents patient exposure to unnecessary and potentially harmful therapeutic agents and diagnostic tests. This article reviews the clinical and genetic features of some mendellan and mitochondrial disorders associated with ischemic stroke, hemorrhagic stroke, and cerebrovascular malformations.

Analysis of the polycystins in aortic vascular smooth muscle cells

The leading cause of death in autosomal dominant polycystic kidney disease (ADPKD) is cardiovascular. However, little is known about the pathogenesis of these manifestations. The present study was undertaken to characterize the ADPKD proteins, the polycystins, in vascular smooth muscle cells. It was demonstrated that the expression of polycystin-1 is developmentally regulated, whereas polycystin-2 has a more constant level of expression. A polycystin-1 subpopulation was immunoprecipitated by polycystin-2, indicating an in vivo interaction of these two proteins. Analysis with glycosidase and cell surface biotinylation indicates that some polycystin-1 products, but not polycystin-2, are located on the plasma membrane. Immunofluorescence showed that most of the polycystin-1 and polycystin-2 was cytoplasmic but that persistent polycystin-1 staining was located in proximity to the cell surface after a Triton-X extraction, whereas no clear surface localization of polycystin-2 was detected. Immuno-gold electron microscopy revealed that polycystin-1 was localized at the plasma membrane and sarcoplasmic reticulum, whereas polycystin-2 was mainly located in the sarcoplasmic reticulum. Both polycystins were found to be associated with dense plaques. These observations are consistent with an important role of the polycystins in the development, maintenance, and function of the myoelastic arterial organization and with the vascular phenotype associated with ADPKD.

Screening for intracranial aneurysms in autosomal dominant polycystic kidney disease. Review Article

Screening patients with autosomal dominant polycystic kidney disease (ADPKD) for asymptomatic intracranial aneurysms has been proposed as a method of reducing the morbidity and mortality associated with aneurysm rupture. However, recent studies have shown lower spontaneous rupture rates of small aneurysms and higher risks of significant complications with interventions than previously reported. Risk-benefit analysis has not demonstrated any benefit of screening ADPKD patients without a history of subarachnoid haemorrhage (SAH) for intracranial aneurysms, and has suggested that screening might cause harm.

Pkd2 haploinsufficiency alters intracellular calcium regulation in vascular smooth muscle cells

Autosomal-dominant polycystic kidney disease is a multiorgan disease and its vascular manifestations are common and life-threatening. Despite this, little is known about their pathogenesis. Somatic mutations to the normal PKD allele in cystic epithelia and cyst development associated with the unstable Pkd2(WS25) allele suggest a two-hit model of cystogenesis. However, it is unclear if this model can account for the cardiovascular pathology or if haploinsufficiency alone is disease-associated. In the present study, we found a decreased polycystin-2 (PC2, protein encoded by Pkd2 gene) expression in Pkd2( +/-) vessels, roughly half the wild-type level, and an enhanced level of intracranial vascular abnormalities in Pkd2 (+/-) mice when induced to develop hypertension. Consistent with these observations, freshly dissociated Pkd2 (+/-) vascular smooth muscle cells have significantly altered intracellular Ca(2+) homeostasis. The resting [Ca(2+)](i) is 17.1% lower in Pkd2 (+/-) compared with wild-type cells (P=0.0003) and the total sarcoplasmic reticulum Ca(2+) store (emptied by caffeine plus thapsigargin) is decreased (P<0.0001). The store operated Ca(2+) (SOC) channel activity is also decreased in Pkd2 (+/-) cells (P=0.008). These results indicate that inactivation of just one Pkd2 allele is sufficient to significantly alter intracellular Ca(2+) homeostasis, and that PC2 is necessary to maintain normal SOC activity and the SR Ca(2+) store in VSMCs. Based on these findings, and the fact that [Ca(2+)](i) signaling is essential to the regulation of contraction, production and secretion of extracellular matrix, cellular proliferation and apoptosis, we propose that the abnormal intracellular Ca(2+) regulation associated with Pkd2 haploinsufficiency is directly related to the vascular phenotype.

Association of mutation position in polycystic kidney disease 1 (PKD1) gene and development of a vascular phenotype

BACKGROUND

Patients with autosomal dominant polycystic kidney disease (ADPKD) are at risk of developing intracranial aneurysms, and subarachnoid haemorrhage is a major cause of death and disability. Familial clustering of intracranial aneurysms suggests that genetic factors are important in the aetiology. We tested whether the germline mutation predisposes to this vascular phenotype.

METHODS

DNA samples from patients with ADPKD and vascular complications were screened for mutations throughout the PKD1 and PKD2 genes. Comparisons were made between the PKD1 and PKD2 populations and with a control PKD1 cohort (without the vascular phenotype).

FINDINGS

Mutations were characterised in 58 ADPKD families with vascular complications; 51 were PKD1 (88%) and seven PKD2 (12%). The median position of the PKD1 mutation was significantly further 59 in the vascular population than in the 87 control pedigrees (aminoacid position 2163 vs 2773, p=0.0034). Subsets of the vascular population with aneurysmal rupture, early rupture, or families with more than one vascular case had median mutation locations further 59 (aminoacid position 1811, p=0.0018; 1671, p=0.0052; and 1587, p=0.0003).

INTERPRETATION

Patients with PKD2, as well as those with PKD1, are at risk of intracranial aneurysm. The position of the mutation in PKD1 is predictive for development of intracranial aneurysms (59 mutations are more commonly associated with vascular disease) and is therefore of prognostic importance. Since the PKD1 phenotype is associated with mutation position, the disease is not simply due to loss of all disease allele products.

Familial intracranial aneurysms: an analysis of 346 multiplex Finnish families

BACKGROUND AND PURPOSE

Genetic risk factors are considered important in the development, growth, and rupture of intracranial aneurysms; however, few have been identified. We analyzed intracranial aneurysm families with at least 2 affected persons and determined relationships between affected persons and assessed the inheritance patterns of aneurysms.

METHODS

Families with > or =2 members with verified diagnoses of intracranial aneurysms were recruited from Kuopio and Helsinki, Finland. Families with a diagnosis of other heritable disorders that have associated intracranial aneurysms, such as autosomal dominant polycystic kidney disease, were excluded.

RESULTS

We identified 346 Finnish multiplex families with 160 (46.2%) male and 186 (53.8%) female index cases. There were a total of 937 aneurysm cases, with an average of 2.7 cases per family. The majority of the families had only 2 affected relatives (n=206; 59.5%), although there were families with up to 6 (n=10), 7 (n=1), 8 (n=1), or 10 (n=2) affected persons. The affected relatives of the index cases included 108 sisters, 116 brothers, 105 parents, 30 children, 15 grandparents, 102 aunts or uncles, and 64 cousins. Of the 937 affected persons, 569 (60.7%) were alive and available for genetic analysis. Inheritance patterns consistent with autosomal recessiveness were observed in 198 (57.2%), autosomal dominance in 126 (36.4%), and autosomal dominance with incomplete penetrance in 19 (5.5%) of the families.

CONCLUSIONS

The collection is the most extensive published to date and extends previous observations of familial aggregation that are consistent with a major gene effect.

Molecular basis of polycystic kidney disease: PKD1, PKD2 and PKHD1

Recent developments have helped elucidate the function of the autosomal dominant polycystic kidney disease proteins, polycystin-1 and polycystin-2, and have revealed the primary defect in autosomal recessive polycystic kidney disease, by positional cloning of the gene, PKHD1. Several studies demonstrating that polycystin-2 can act as a calcium-ion-permeable cation channel, and that polycystin-1 may be involved in regulating/localizing this channel, have provided compelling evidence of the function of these proteins. A role in regulating intracellular calcium levels seems likely, with the many cellular abnormalities associated with cystogenesis due to a disruption of calcium homeostasis. Improved mutation analysis in autosomal dominant polycystic kidney disease has led to the finding of genotype/phenotype correlations which could be related to possible cleavage of polycystin-1. A major recent breakthrough has revealed the primary defect in autosomal recessive polycystic kidney disease. Genetic analysis showed that the PCK rat model is orthologous to autosomal recessive polycystic kidney disease, and allowed the human gene, PKHD1, to be precisely localized and identified. PKHD1 is a large gene, encoding a protein, fibrocystin, of 4074 amino acids, which is predicted to have a large extracellular region, a single transmembrane domain and a short cytoplasmic tail. Fibrocystin may act as a receptor with critical roles in collecting-duct and biliary development.