Polycystins, ADPKD, and Cardiovascular Disease

Spontaneous Coronary Artery Dissection in Patients with Autosomal Dominant Polycystic Kidney Disease: A Systematic Review of the Literature

Spontaneous coronary artery dissection (SCAD) is a spontaneous intimal tear of the coronary artery wall. A factor rarely associated with SCAD is autosomal dominant polycystic kidney disease (ADPKD). Using the PRISMA guidelines, we identified 10 unique cases of SCAD in ADPKD patients reported between 1998 and 2021. Ages ranged from 36 to 59 years, with an average of 44.6 years. The majority of patients were female (80%). Each case was diagnosed with a cardiovascular event: ST-elevation myocardial infarction (STEMI) in 40%, non-ST elevation myocardial infarction (NSTEMI) in 50%, and stable angina in 10%. Conservative management was used in 60% of cases. There is a significant gap in our understanding of the relationship between SCAD and ADPKD. Polycystin complex can lead to structural abnormalities in blood vessels, resulting in vascular leaks and vessel rupture. This suggests that ADPKD patients may have an elevated risk of arteriopathies, including coronary artery dissection.

Long-term health outcomes associated with hydration status

Body water balance is determined by fundamental homeostatic mechanisms that maintain stable volume, osmolality and the composition of extracellular and intracellular fluids. Water balance is maintained by multiple mechanisms that continuously match water losses through urine, the skin, the gastrointestinal tract and respiration with water gains achieved through drinking, eating and metabolic water production. Hydration status is determined by the state of the water balance. Underhydration occurs when a decrease in body water availability, due to high losses or low gains, stimulates adaptive responses within the water balance network that are aimed at decreasing losses and increasing gains. This stimulation is also accompanied by cardiovascular adjustments. Epidemiological and experimental studies have linked markers of low fluid intake and underhydration - such as increased plasma concentration of vasopressin and sodium, as well as elevated urine osmolality - with an increased risk of new-onset chronic diseases, accelerated aging and premature mortality, suggesting that persistent activation of adaptive responses may be detrimental to long-term health outcomes. The causative nature of these associations is currently being tested in interventional trials. Understanding of the physiological responses to underhydration may help to identify possible mechanisms that underlie potential adverse, long-term effects of underhydration and inform future research to develop preventative and treatment approaches to the optimization of hydration status.

Utilization of the genetically encoded calcium indicator Salsa6F in cardiac applications

Calcium signaling is a critical process required for cellular mechanisms such as cardiomyocyte contraction. The inability of the cell to properly activate or regulate calcium signaling can lead to contractile dysfunction. In isolated cardiomyocytes, calcium signaling has been primarily studied using calcium fluorescent dyes, however these dyes have limited applicability to whole organs. Here, we crossed the Salsa6f mouse which expresses a genetically encoded ratiometric cytosolic calcium indicator with a cardiomyocyte specific inducible cre to temporally-induce expression and studied cytosolic calcium transients in isolated cardiomyocytes and modified Langendorff heart preparations. Isolated cardiomyocytes expressing Salsa6f or Fluo-4AM loaded were compared. We also crossed the Salsa6f mouse with a floxed Polycystin 2 (PC2) mouse to test the feasibility of using the Salsa6f mouse to measure calcium transients in PC2 heterozygous or homozygous knock out mice. Although there are caveats in the applicability of the Salsa6f mouse, there are clear advantages to using the Salsa6f mouse to measure whole heart calcium signals.

The screening, diagnosis, and management of patients with autosomal dominant polycystic kidney disease: A national consensus statement from Taiwan

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited cause of end-stage kidney disease (ESKD) worldwide. Guidelines for the diagnosis and management of ADPKD in Taiwan remains unavailable. In this consensus statement, we summarize updated information on clinical features of international and domestic patients with ADPKD, followed by suggestions for optimal diagnosis and care in Taiwan. Specifically, counselling for at-risk minors and reproductive issues can be important, including ethical dilemmas surrounding prenatal diagnosis and pre-implantation genetic diagnosis. Studies reveal that ADPKD typically remains asymptomatic until the fourth decade of life, with symptoms resulting from cystic expansion with visceral compression, or rupture. The diagnosis can be made based on a detailed family history, followed by imaging studies (ultrasound, computed tomography, or magnetic resonance imaging). Genetic testing is reserved for atypical cases mostly. Common tools for prognosis prediction include total kidney volume, Mayo classification and PROPKD/genetic score. Screening and management of complications such as hypertension, proteinuria, urological infections, intracranial aneurysms, are also crucial for improving outcome. We suggest that the optimal management strategies of patients with ADPKD include general medical care, dietary recommendations and ADPKD-specific treatments. Key points include rigorous blood pressure control, dietary sodium restriction and Tolvaptan use, whereas the evidence for somatostatin analogues and mammalian target of rapamycin (mTOR) inhibitors remains limited. In summary, we outline an individualized care plan emphasizing careful monitoring of disease progression and highlight the need for shared decision-making among these patients.

Cardiovascular perspectives of the TRP channel polycystin 2

Calcium release from the endoplasmic reticulum (ER) is predominantly driven by two key ion channel receptors, inositol 1, 4, 5-triphosphate receptor (InsP3R) in non-excitable cells and ryanodine receptor (RyR) in excitable and muscle-based cells. These calcium transients can be modified by other less-studied ion channels, including polycystin 2 (PC2), a member of the transient receptor potential (TRP) family. PC2 is found in various cell types and is evolutionarily conserved with paralogues ranging from single-cell organisms to yeasts and mammals. Interest in the mammalian form of PC2 stems from its disease relevance, as mutations in the PKD2 gene, which encodes PC2, result in autosomal dominant polycystic kidney disease (ADPKD). This disease is characterized by renal and liver cysts, and cardiovascular extrarenal manifestations. However, in contrast to the well-defined roles of many TRP channels, the role of PC2 remains unknown, as it has different subcellular locations, and the functional understanding of the channel in each location is still unclear. Recent structural and functional studies have shed light on this channel. Moreover, studies on cardiovascular tissues have demonstrated a diverse role of PC2 in these tissues compared to that in the kidney. We highlight recent advances in understanding the role of this channel in the cardiovascular system and discuss the functional relevance of PC2 in non-renal cells.

Autosomal Dominant Polycystic Kidney Disease: Extrarenal Involvement

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder, but kidneys are not the only organs involved in this systemic disorder. Individuals with the condition may display additional manifestations beyond the renal system, involving the liver, pancreas, and brain in the context of cystic manifestations, while involving the vascular system, gastrointestinal tract, bones, and cardiac valves in the context of non-cystic manifestations. Despite kidney involvement remaining the main feature of the disease, thanks to longer survival, early diagnosis, and better management of kidney-related problems, a new wave of complications must be faced by clinicians who treated patients with ADPKD. Involvement of the liver represents the most prevalent extrarenal manifestation and has growing importance in the symptom burden and quality of life. Vascular abnormalities are a key factor for patients' life expectancy and there is still debate whether to screen or not to screen all patients. Arterial hypertension is often the earliest onset symptom among ADPKD patients, leading to frequent cardiovascular complications. Although cardiac valvular abnormalities are a frequent complication, they rarely lead to relevant problems in the clinical history of polycystic patients. One of the newest relevant aspects concerns bone disorders that can exert a considerable influence on the clinical course of these patients. This review aims to provide the "state of the art" among the extrarenal manifestation of ADPKD.

The Han:SPRD Rat: A Preclinical Model of Polycystic Kidney Disease

Autosomal Dominant Polycystic Kidney Disease (ADPKD) stands as the most prevalent hereditary renal disorder in humans, ultimately culminating in end-stage kidney disease. Animal models carrying mutations associated with polycystic kidney disease have played an important role in the advancement of ADPKD research. The Han:SPRD rat model, carrying an R823W mutation in the Anks6 gene, is characterized by cyst formation and kidney enlargement. The mutated protein, named Samcystin, is localized in cilia of tubular epithelial cells and seems to be involved in cystogenesis. The homozygous Anks6 mutation leads to end-stage renal disease and death, making it a critical factor in kidney development and function. This review explores the utility of the Han:SPRD rat model, highlighting its phenotypic similarity to human ADPKD. Specifically, we discuss its role in preclinical trials and its importance for investigating the pathogenesis of the disease and developing new therapeutic approaches.

Cardiac Localized Polycystin-2 plays a Functional Role in Natriuretic Peptide Production and its Absence Contributes to Hypertension

Cardiovascular complications are the most common cause of mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Hypertension is seen in 70% of patients by the age of 30 prior to decline in kidney function. The natriuretic peptides (NPs), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by cardiomyocytes in response to membrane stretch, increasing urinary excretion of sodium and water. Mice heterozygous for Pkd2 have attenuated NP responses and we hypothesized that cardiomyocyte-localized polycystin proteins contribute to production of NPs. Cardiomyocyte-specific knock-out models of polycystin-2 (PC2), one of the causative genes of ADPKD, demonstrate diurnal hypertension. These mice have decreased ANP and BNP expression in the left ventricle. Analysis of the pathways involved in production, maturation, and activity of NPs identified decreased transcription of CgB, PCSK6, and NFAT genes in cPC2-KOs. Engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 KO of PKD2 failed to produce ANP. These results suggest that PC2 in cardiomyocytes are involved in NP production and lack of cardiac PC2 predisposes to a hypertensive volume expanded phenotype, which may contribute to the development of hypertension in ADPKD.

Utilization of the genetically encoded calcium indicator Salsa6F in cardiac applications

Calcium signaling is a critical process required for cellular mechanisms such as cardiac contractility. The inability of the cell to properly activate or regulate calcium signaling can lead to contractile dysfunction. In isolated cardiomyocytes, calcium signaling has been primarily studied using calcium fluorescent dyes, however these dyes have limited applicability to whole organs. Here, we crossed the Salsa6f mouse which expresses a genetically encoded ratiometric cytosolic calcium indicator with a cardiomyocyte specific inducible cre to temporally-induce expression and studied cytosolic calcium transients in isolated cardiomyocytes and modified Langendorff heart preparations. Isolated cardiomyocytes expressing Salsa6f or Fluo-4AM loaded were compared. We also crossed the Salsa6f mouse with a floxed Polycystin 2 (PC2) mouse to test the feasibility of using the Salsa6f mouse to measure calcium transients in PC2 heterozygous or homozygous knock out mice. Although there are caveats in the applicability of the Salsa6f mouse, there are clear advantages to using the Salsa6f mouse to measure whole heart calcium signals.

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

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

Cardiometabolic comorbidities in autosomal dominant polycystic kidney disease: a 16-year retrospective cohort study

BACKGROUND

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent hereditary kidney disease and the fourth leading cause of end-stage renal disease (ESRD) requiring renal replacement therapy (RRT). Nevertheless, there is a paucity of epidemiological research examining the risk factors and survival on RRT for ADPKD. Thus, we aimed to investigate the cumulative effects of cardiometabolic comorbidities, including hypertension (HTN), type 2 diabetes mellitus (DM), and dyslipidemia (DLP) to clinical outcomes in ADPKD.

METHODS

We identified 6,142 patients with ADPKD aged ≥ 20 years from 2000 to 2015 using a nationwide population-based database. HTN, DM, and DLP diagnoses before or at the time of ADPKD diagnosis and different combinations of the three diagnoses were used as the predictors for the outcomes. Survival analyses were used to estimate the adjusted mortality risk from cardiometabolic comorbidities and the risk for renal survival.

RESULTS

Patients with ADPKD who developed ESRD had the higher all-cause mortality (HR, 5.14; [95% CI: 3.88-6.80]). Patients with all three of the diseases had a significantly higher risk of entering ESRD (HR:4.15, [95% CI:3.27-5.27]), followed by those with HTN and DM (HR:3.62, [95% CI:2.82-4.65]), HTN and DLP (HR:3.54, [95% CI:2.91-4.31]), and HTN alone (HR:3.10, [95% CI:2.62-3.66]) compared with those without any three cardiometabolic comorbidities.

CONCLUSIONS

Our study discovered the cumulative effect of HTN, DM, and DLP on the risk of developing ESRD, which reinforces the urgency of proactive prevention of cardiometabolic comorbidities to improve renal outcomes and overall survival in ADPKD patients.

Cardiovascular Manifestations and Management in ADPKD

Cardiovascular disease (CVD) is the major cause of mortality in autosomal dominant polycystic kidney disease (ADPKD) and contributes to significant burden of disease. The manifestations are varied, including left ventricular hypertrophy (LVH), intracranial aneurysms (ICAs), valvular heart disease, and cardiomyopathies; however, the most common presentation and a major modifiable risk factor is hypertension. The aim of this review is to detail the complex pathogenesis of hypertension and other extrarenal cardiac and vascular conditions in ADPKD drawing on preclinical, clinical, and epidemiological evidence. The main drivers of disease are the renin-angiotensin-aldosterone system (RAAS) and polycystin-related endothelial cell dysfunction, with the sympathetic nervous system (SNS), nitric oxide (NO), endothelin-1 (ET-1), and asymmetric dimethylarginine (ADMA) likely playing key roles in different disease stages. The reported rates of some manifestations, such as LVH, have decreased likely due to the use of antihypertensive therapies; and others, such as ischemic cardiomyopathy, have been reported with increased prevalence likely due to longer survival and higher rates of chronic disease. ADPKD-specific screening and management guidelines exist for hypertension, LVH, and ICAs; and these are described in this review.

Calcium signaling in polycystic kidney disease- cell death and survival

Polycystic kidney disease is typified by cysts in the kidney and extra-renal manifestations including hypertension and heart failure. The main genetic underpinning this disease are loss-of function mutations to the two polycystin proteins, polycystin 1 and polycystin 2. Molecularly, the disease is characterized by changes in multiple signaling pathways including down regulation of calcium signaling, which, in part, is contributed by the calcium permeant properties of polycystin 2. These signaling pathways enable the cystic cells to survive and avoid cell death. This review focuses on the studies that have emerged in the past 5 years describing how the structural insights gained from PC-1 and PC-2 inform the calcium dependent molecular pathways of autophagy and the unfolded protein response that are regulated by the polycystin proteins and how it leads to cell survival and/or cell death.

A Case Report of Successful Kidney Transplantation in a Patient With Autosomal Dominant Polycystic Kidney Disease Who Underwent Thoracic Endovascular Aortic Repair for Type B Aortic Dissection

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is associated with several cardiovascular disorders, including aortic dissection, which preferentially occurs at the thoracic or abdominal level. Because there are few case reports describing surgical repair for aortic dissection followed by renal transplantation in patients with ADPKD, kidney transplantation performed after repair for aortic dissection remains challenging.

CASE PRESENTATION

A 34-year-old Japanese man with end-stage renal disease secondary to ADPKD underwent thoracic endovascular aortic repair for complicated acute type B aortic dissection 12 months earlier. A contrast computed tomography scan before transplantation revealed an aortic dissection involving the descending aorta proximal to the common iliac arteries and confirmed multiple large bilateral renal cysts. After simultaneous right native nephrectomy, the patient underwent preemptive living-donor kidney transplantation obtained from his mother. Intraoperatively, we noted that dissection of the external iliac vessels was difficult because of dense adhesions. Arterial clamping was performed immediately below the bifurcation of the internal iliac artery to prevent further aortic dissection of the external iliac artery. After end-to-end anastomosis to the internal iliac artery was completed and the vascular clamp was released, the kidney began to produce urine immediately.

CONCLUSION

This case suggests that kidney transplantation in patients undergoing endovascular aortic repair for aortic dissection can be performed by adequately applying a vascular clamp proximal to the internal iliac artery during vascular anastomosis.

Autosomal dominant and autosomal recessive polycystic kidney disease: hypertension and secondary cardiovascular effect in children

Autosomal dominant (ADPKD) and autosomal recessive (ARPKD) polycystic kidney disease are the most widely known cystic kidney diseases. They are significantly different from each other in terms of genetics and clinical manifestations. Hypertension is one of the main symptoms in both diseases, but the age of onset and secondary cardiovascular complications are significantly different. Most ARPKD children are hypertensive in the first year of life and need high doses of hypertensive drugs. ADPKD patients with a very early onset of the disease (VEOADPKD) develop hypertension similarly to patients with ARPKD. Conversely, a significantly lower percentage of patients with classic forms of ADPKD develops hypertension during childhood, although probably more than originally thought. Data published in the past decades show that about 20%–30% of ADPKD children are hypertensive. Development of hypertension before 35 years of age is a known risk factor for more severe disease in adulthood. The consequences of hypertension on cardiac geometry and function are not well documented in ARPKD due to the rarity of the disease, the difficulties in collecting homogeneous data, and differences in the type of parameters evaluated in different studies. Overall, left ventricular hypertrophy (LVH) has been reported in 20%–30% of patients and does not always correlate with hypertension. Conversely, cardiac geometry and cardiac function are preserved in the vast majority of hypertensive ADPKD children, even in patients with faster decline of kidney function. This is probably related to delayed onset of hypertension in ADPKD, compared to ARPKD. Systematic screening of hypertension and monitoring secondary cardiovascular damage during childhood allows initiating and adapting antihypertensive treatment early in the course of the disease, and may limit disease burden later in adulthood.

Electrical Remodeling in Right Ventricular Failure Due to Pulmonary Hypertension: Unraveling Novel Therapeutic Targets

Arrhythmias in the setting of right-ventricular (RV) remodeling contribute to majority of deaths in patients with pulmonary hypertension. However, the underlying mechanism of electrical remodeling remains elusive, especially ventricular arrhythmias. Here, we analyzed the RV transcriptome of pulmonary arterial hypertension (PAH) patients with compensated RV or decompensated RV and identified 8 and 45 differentially expressed genes known to be involved in regulating the electrophysiological properties of excitation and contraction of cardiac myocytes, respectively. Transcripts encoding voltage-gated Ca²⁺ and Na⁺ channels were notably decreased in PAH patients with decompensated RV, along with significant dysregulation of K_V and K_ir channels. We further showed similarity of the RV channelome signature with two well-known animal models of PAH, monocrotaline (MCT)- and Sugen-hypoxia (SuHx)-treated rats. We identified 15 common transcripts among MCT, SuHx, and PAH patients with decompensated RV failure. In addition, data-driven drug repurposing using the channelome signature of PAH patients with decompensated RV failure predicted drug candidates that may reverse the altered gene expression. Comparative analysis provided further insight into clinical relevance and potential preclinical therapeutic studies targeting mechanisms involved in arrhythmogenesis.

Polycystin Channel Complexes

Polycystin subunits can form hetero- and homotetrameric ion channels in the membranes of various compartments of the cell. Homotetrameric polycystin channels are voltage- and calcium-modulated, whereas heterotetrameric versions are proposed to be ligand- or autoproteolytically regulated. Their importance is underscored by variants associated with autosomal dominant polycystic kidney disease and by vital roles in fertilization and embryonic development. The diversity in polycystin assembly and subcellular distribution allows for a multitude of sensory functions by this class of channels. In this review, we highlight their recent structural and functional characterization, which has provided a molecular blueprint to investigate the conformational changes required for channel opening in response to unique stimuli. We consider each polycystin channel type individually, discussing how they contribute to sensory cell biology, as well as their impact on the physiology of various tissues.

Mutation Analysis of Autosomal-Dominant Polycystic Kidney Disease Patients

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

Cardiac Manifestations in Patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD): A Single-Center Study

Key Points

Cardiovascular disease—a key driver of morbidity in CKD—is common in patients with autosomal dominant polycystic kidney disease (ADPKD). Pathologic echocardiography findings, including valvular defects, aortic root dilation, and hypertrophy, are found in most patients with ADPKD. These findings correlate with parameters indicating disease progression in ADPKD. Echocardiography should be offered to all patients with ADPKD.

Background

ADPKD is the most common monogenetic kidney disease and results in kidney failure in >75% of affected individuals. As a systemic disorder, ADPKD is associated with a variety of extrarenal manifestations, including cardiac manifestations, that affect the majority of patients. We characterized the cardiac involvement in patients with ADPKD from the German AD(H)PKD registry and compared them with kidney donor candidates as controls.

Methods

In this single-center cohort study, we evaluated 141 patients with ADPKD (44.17±11.23 years) from the German AD(H)PKD registry and 60 kidney donor candidates (55.08±10.21 years). All patients underwent clinical examination, abdominal MRI, and transthoracic echocardiography.

Results

Of the patients with ADPKD, 65% showed hypertrophy of the left ventricle (as defined by an end-diastolic interventricular septal wall thickness [IVSd] >10 mm) compared with 55% in control patients. Mitral regurgitation was the most common finding among 54% of patients with ADPKD who exhibited valvular dysfunction, albeit mild in most patients. Interestingly, left ventricular ejection fraction (LV-EF) differed significantly between both groups, with higher values in patients with ADPKD (64%±6% versus 60%±6%), whereas other parameters, including IVSd, left ventricular end-diastolic diameter (LVEDD), tricuspid annular plane systolic excursion (TAPSE), and pressure gradients across the aortic and tricuspid valve were similar between groups. Correlations of echocardiographic parameters with markers of disease progression revealed statistically significant associations for aortic root diameter (P =0.01), the pressure gradient across the aortic valve (AV dPmax; P =0.0003), and IVSd (P =0.0001), indicating rapid kidney disease progression may also be associated with cardiac findings.

Conclusion

Cardiovascular abnormalities are prevalent in patients with ADPKD. Considering the importance of cardiovascular disease for outcomes in CKD, early management and possibly prevention are important goals of any treatment scheme. Consequently, echocardiography should be offered to all patients with ADPKD in routine management.

Polycystin-1 Is a Crucial Regulator of BIN1 Expression and T-Tubule Remodeling Associated with the Development of Dilated Cardiomyopathy

Cardiomyopathy is commonly observed in patients with autosomal dominant polycystic kidney disease (ADPKD), even when they have normal renal function and arterial pressure. The role of cardiomyocyte polycystin-1 (PC1) in cardiovascular pathophysiology remains unknown. PC1 is a potential regulator of BIN1 that maintains T-tubule structure, and alterations in BIN1 expression induce cardiac pathologies. We used a cardiomyocyte-specific PC1-silenced (PC1-KO) mouse model to explore the relevance of cardiomyocyte PC1 in the development of heart failure (HF), considering reduced BIN1 expression induced T-tubule remodeling as a potential mechanism. PC1-KO mice exhibited an impairment of cardiac function, as measured by echocardiography, but no signs of HF until 7-9 months of age. Of the PC1-KO mice, 43% died suddenly at 7 months of age, and 100% died after 9 months with dilated cardiomyopathy. Total BIN1 mRNA, protein levels, and its localization in plasma membrane-enriched fractions decreased in PC1-KO mice. Moreover, the BIN1 + 13 isoform decreased while the BIN1 + 13 + 17 isoform was overexpressed in mice without signs of HF. However, BIN1 + 13 + 17 overexpression was not observed in mice with HF. T-tubule remodeling and BIN1 score measured in plasma samples were associated with decreased PC1-BIN1 expression and HF development. Our results show that decreased PC1 expression in cardiomyocytes induces dilated cardiomyopathy associated with diminished BIN1 expression and T-tubule remodeling. In conclusion, positive modulation of BIN1 expression by PC1 suggests a novel pathway that may be relevant to understanding the pathophysiological mechanisms leading to cardiomyopathy in ADPKD patients.

Trans-epithelial fluid flow and mechanics of epithelial morphogenesis

Active fluid transport across epithelial monolayers is emerging as a major driving force of tissue morphogenesis in a variety of healthy and diseased systems, as well as during embryonic development. Cells use directional transport of ions and osmotic gradients to drive fluid flow across the cell surface, in the process also building up fluid pressure. The basic physics of this process is described by the osmotic engine model, which also underlies actin-independent cell migration. Recently, the trans-epithelial fluid flux and the hydraulic pressure gradient have been explicitly measured for a variety of cellular and tissue model systems across various species. For the kidney, it was shown that tubular epithelial cells behave as active mechanical fluid pumps: the trans-epithelial fluid flux depends on the hydraulic pressure difference across the epithelial layer. When a stall pressure is reached, the fluid flux vanishes. Hydraulic forces generated from active fluid pumping are important in tissue morphogenesis and homeostasis, and could also underlie multiple morphogenic events seen in other developmental contexts. In this review, we highlight findings that examined the role of trans-epithelial fluid flux and hydraulic pressure gradient in driving tissue-scale morphogenesis. We also review organ pathophysiology due to impaired fluid pumping and the loss of hydraulic pressure sensing at the cellular scale. Finally, we draw an analogy between cellular fluidic pumps and a connected network of water pumps in a city. The dynamics of fluid transport in an active and adaptive network is determined globally at the systemic level, and transport in such a network is best when each pump is operating at its optimal efficiency.

Endothelium-Specific Deficiency of Polycystin-1 Promotes Hypertension and Cardiovascular Disorders

Background:

Autosomal dominant polycystic kidney disease is the most frequent hereditary kidney disease and is generally due to mutations in PKD1 and PKD2 , encoding polycystins 1 and 2. In autosomal dominant polycystic kidney disease, hypertension and cardiovascular disorders are highly prevalent, but their mechanisms are partially understood.

Methods:

Since endothelial cells express the polycystin complex, where it plays a central role in the mechanotransduction of blood flow, we generated a murine model with inducible deletion of Pkd1 in endothelial cells ( Cdh5-Cre ERT2 ; Pkd1 fl/fl ) to specifically determine the role of endothelial polycystin-1 in autosomal dominant polycystic kidney disease.

Results:

Endothelial deletion of Pkd1 induced endothelial dysfunction, as demonstrated by impaired flow-mediated dilatation of resistance arteries and impaired relaxation to acetylcholine, increased blood pressure and prevented the normal development of arteriovenous fistula. In experimental chronic kidney disease induced by subtotal nephrectomy, endothelial deletion of Pkd1 further aggravated endothelial dysfunction, vascular remodeling, and heart hypertrophy.

Conclusions:

Altogether, this study provides the first in vivo demonstration that specific deletion of Pkd1 in endothelial cells promotes endothelial dysfunction and hypertension, impairs arteriovenous fistula development, and potentiates the cardiovascular alterations associated with chronic kidney disease.

Echocardiographic Abnormalities in Autosomal Dominant Polycystic Kidney Disease (ADPKD) Patients

Cardiovascular abnormalities, such as left ventricular hypertrophy and valvular disorders, particularly mitral valve prolapse, have been described as highly prevalent among adult patients with autosomal dominant polycystic kidney disease (ADPKD). The present study aimed to assess echocardiographic parameters in a large sample of both normotensive and hypertensive ADPKD patients, regardless of kidney function level, and evaluate their association with clinical and laboratorial parameters. A retrospective study consisted of the analysis of clinical, laboratorial, and transthoracic echocardiograms data retrieved from the medical records of young adult ADPKD outpatients. A total of 294 patients (120 M/174 F, 41.0 ± 13.8 years old, 199 hypertensive and 95 normotensive) with a median estimated glomerular filtration rate (eGFR) of 75.5 mL/min/1.73 m² were included. The hypertensive group (67.6%) was significantly older and exhibited significantly lower eGFR than the normotensive one. Increased left ventricular mass index (LVMI) was seen in 2.0%, mitral valve prolapse was observed in 3.4%, mitral valve regurgitation in 15.3%, tricuspid valve regurgitation in 16.0%, and aortic valve regurgitation in 4.8% of the whole sample. The present study suggested that the prevalence of mitral valve prolapse was much lower than previously reported, and increased LVMI was not seen in most adult ADPKD patients.

Cardiovascular Outcomes in Kidney Transplant Recipients With ADPKD

Introduction

Cardiovascular disease leads to high morbidity and mortality in patients with kidney failure. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a systemic disease with various cardiac abnormalities. Details on the cardiovascular profile of patients with ADPKD who are undergoing kidney transplantation (KT) and its progression are limited.

Methods

Echocardiographic data within 2 years before KT (1993-2020), and major adverse cardiovascular events (MACEs) after transplantation were retrieved. The primary outcome is to assess cardiovascular abnormalities on echocardiography at the time of transplantation in ADPKD as compared with patients without ADPKD matched by sex (male, 59.4%) and age at transplantation (57.2 ± 8.8 years).

Results

Compared with diabetic nephropathy (DN, n = 271) and nondiabetic, patients without ADPKD (NDNA) (n = 271) at the time of KT, patients with ADPKD (n = 271) had lower rates of left ventricular hypertrophy (LVH) (39.4% vs. 66.4% vs. 48.6%), mitral (2.7% vs. 6.3% vs. 7.45) and tricuspid regurgitations (1.8% vs. 6.6% vs. 7.2%). Patients with ADPKD had less diastolic (25.3%) and systolic (5.6%) dysfunction at time of transplantation. Patients with ADPKD had the most favorable post-transplantation survival (median 18.7 years vs. 12.0 for diabetic nephropathy [DN] and 13.8 years for nondiabetic non-ADPKD [NDNA]; P < 0.01) and the most favorable MACE-free survival rate (hazard ratio = 0.51, P < 0.001). Patients with ADPKD had worsening of their valvular function and an increase in the sinus of Valsalva diameter post-transplantation (38.2 vs. 39.9 mm, P < 0.01).

Conclusion

ADPKD transplant recipients have the most favorable cardiac profile pretransplantation with better patient survival and MACE-free survival rates but worsening valvular function and increasing sinus of Valsalva diameter, as compared with patients with other kidney diseases.

Is autosomal dominant polycystic kidney disease an early sweet disease?

The clinical course of autosomal dominant polycystic kidney disease (ADPKD) starts in childhood. Evidence of the beneficial impact of early nephron-protective strategies and lifestyle modifications on ADPKD prognosis is accumulating. Recent studies have described the association of overweight and obesity with rapid disease progression in adults with ADPKD. Moreover, defective glucose metabolism and metabolic reprogramming have been reported in distinct ADPKD models highlighting these pathways as potential therapeutic targets in ADPKD. Several "metabolic" approaches are currently under evaluation in adults, including ketogenic diet, food restriction, and metformin therapy. No data are available on the impact of these approaches in childhood thus far. Yet, according to World Health Organization (WHO), we are currently facing a childhood obesity crisis with an increased prevalence of overweight/obesity in the pediatric population associated with a cardio-metabolic risk profile. The present review summarizes the knowledge about the role of glucose metabolism in the pathophysiology of ADPKD and underscores the possible harm of overweight and obesity in ADPKD especially in terms of long-term cardiovascular outcomes and renal prognosis.

Echocardiographic Findings and Genotypes in Autosomal Dominant Polycystic Kidney Disease

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease and is well known to have extrarenal complications. Cardiovascular complications are of particular clinical relevance because of their morbidity and mortality; however, unclear is why they occur so frequently in patients with ADPKD and whether they are related to the genotypes.

Methods

We extracted and retrospectively analyzed clinical data on patients with ADPKD who underwent echocardiography and whose genotype was confirmed by genetic testing between April 2016 and December 2020. We used next-generation sequencing to compare cardiac function, structural data, and the presence of cardiac valvular disease in patients with 1 of 3 genotypes: PKD1, PKD2, and non-PKD1, 2.

Results

This retrospective study included 65 patients with ADPKD. Patients were divided into 3 groups: PKD1, n = 32; PKD2, n = 12; and non-PKD1, 2, n = 21. The prevalence of mitral regurgitation (MR) was significantly higher in the PKD1 group than in the PKD2 and non-PKD1, 2 group (46.9% vs. 8.3% vs. 19.0%, respectively; p = 0.02). In contrast, no significant difference was found for other cardiac valve complications.

Conclusion

This study found a significantly higher prevalence of MR in patients with the PKD1 genotype than in those with the PKD2 or non-PKD1, 2 genotypes. Physicians may need to perform echocardiography earlier and more frequently in patients with ADPKD and the PKD1 genotype and to control fluid volume and blood pressure more strictly in these patients to prevent future cardiac events.

Insights Into the Molecular Mechanisms of Polycystic Kidney Diseases

Autosomal dominant (AD) and autosomal recessive (AR) polycystic kidney diseases (PKD) are severe multisystem genetic disorders characterized with formation and uncontrolled growth of fluid-filled cysts in the kidney, the spread of which eventually leads to the loss of renal function. Currently, there are no treatments for ARPKD, and tolvaptan is the only FDA-approved drug that alleviates the symptoms of ADPKD. However, tolvaptan has only a modest effect on disease progression, and its long-term use is associated with many side effects. Therefore, there is still a pressing need to better understand the fundamental mechanisms behind PKD development. This review highlights current knowledge about the fundamental aspects of PKD development (with a focus on ADPKD) including the PC1/PC2 pathways and cilia-associated mechanisms, major molecular cascades related to metabolism, mitochondrial bioenergetics, and systemic responses (hormonal status, levels of growth factors, immune system, and microbiome) that affect its progression. In addition, we discuss new information regarding non-pharmacological therapies, such as dietary restrictions, which can potentially alleviate PKD.

Safety Profile of Tolvaptan in the Treatment of Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease constitutes the most prevalent hereditary kidney disease, associated with high rates of morbidity leading eventually to end-stage renal disease. Tolvaptan is a selective vasopressin antagonist and has emerged as a promising therapeutic option for patients with autosomal dominant polycystic kidney disease. The present review summarized current evidence regarding the safety profile of tolvaptan in patients with the disease. Consistent with its pharmacological action, aquaretic adverse events represent the most common side effects of tolvaptan, consisting of polyuria, pollakiuria and polydipsia. Gradual dose titration based on urinary osmolality, as well as dietary interventions aiming to reduce solute excretion, have been proposed as potential strategies to mitigate polyuria. In addition, tolvaptan administration may be complicated by liver injury, characterized by alanine aminotransferase and bilirubin elevations. Hepatotoxicity has been suggested to be triggered by impaired biliary clearance, activation of innate immunity and increased oxidative stress. Frequent monitoring of liver function tests has been shown to be effective in preventing Hy’s Law and liver failure cases. Uric acid elevation due to reduced renal excretion may lead to hyperuricemia and gout, although no drug discontinuations have been linked to these events. Future studies should confirm the safety profile of tolvaptan in large-scale real-world studies, clarify the pathogenetic pathways leading to hepatotoxicity and define its role in special populations, especially pediatric patients.

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.

Cardiovascular risk factors and the impact on prognosis in patients with chronic kidney disease secondary to autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent hereditary renal disease. There is an increased rate of cardiovascular disease (CVD) in ADPKD. In this study, we evaluate the prevalence of cardiovascular risk factors, the achievement rates for treatment goals and cardiovascular events (CVE) in ADPKD and their relations with asymptomatic CVD in CKD from other etiologies (CKDoe) and controls.

METHODS

We evaluated 2445 CKD patients (2010-2012). The information collected was: clinical, anthropometric and analytical parameters, treatments and CVD evaluation (intima-media thickness (IMT), atheromatous plaque presence and ankle-brachial index (ABI)). Laboratory, vital status, CVE and hospitalizations were collected for 4 years.

RESULTS

ADPKD patients had a worse renal function and worst achievement of blood pressure, higher parathormone levels but lower proteinuria compared to CKDoe. ADPKD patients presented lower IMT values than other groups, however, an intermediate rate of pathologic ABI and atheromatous plaque was present. More than half of the patients received statins, achieving LDL-c levels < 100 only in 50 and 39.8% of them (ADPKD and CKDoe respectively). The number of CVE during the follow-up period was low. In adjusted Cox regression model, ADPDK had the lowest occurrence of CVE of all three groups (HR:0.422, 95%CI 0.221-0.808, p = 0.009).

CONCLUSION

ADPKD patients show intermediate control rates of CVD. A better control of CVD risk seems to be related with a lower load of CVD compared to other groups, which may lead in the long term to a better prognosis. Further investigation is necessary to determine cardiovascular prognosis in ADPKD.

Cardiovascular Disease in Chronic Kidney Disease: Pathophysiological Insights and Therapeutic Options

Patients with chronic kidney disease (CKD) exhibit an elevated cardiovascular risk manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. Although the incidence and prevalence of cardiovascular events is already significantly higher in patients with early CKD stages (CKD stages 1-3) compared with the general population, patients with advanced CKD stages (CKD stages 4-5) exhibit a markedly elevated risk. Cardiovascular rather than end-stage kidney disease (CKD stage 5) is the leading cause of death in this high-risk population. CKD causes a systemic, chronic proinflammatory state contributing to vascular and myocardial remodeling processes resulting in atherosclerotic lesions, vascular calcification, and vascular senescence as well as myocardial fibrosis and calcification of cardiac valves. In this respect, CKD mimics an accelerated aging of the cardiovascular system. This overview article summarizes the current understanding and clinical consequences of cardiovascular disease in CKD.

Increased mTOR and suppressed autophagic flux in the heart of a hypomorphic Pkd1 mouse model of autosomal dominant polycystic kidney disease

Cardiac hypertrophy is common in autosomal dominant polycystic kidney disease (ADPKD) patients. We found increased heart weight in Pkd1^RC/RC and Pkd2^WS25/+ mouse models of ADPKD. As there is a link between increased heart weight and mammalian target of rapamycin (mTOR), the aim of the study was to determine mTOR complex 1 and 2 signaling proteins in the heart in the Pkd1^RC/RC mouse model of PKD. In 70 day old Pkd1^RC/RC hearts, on immunoblot analysis, there was a large increase in p-AMPK^Thr172, a known autophagy inducer, and an increase in p-Akt^Ser473 and p-Akt^Thr308, but no increase in other mTORC1/2 proteins (p-S6^Ser240/244, p-mTOR^Ser2448). In 150 day old Pkd1^RC/RC hearts, there was an increase in mTORC1 (p-S6^Ser240/244) and mTOR-related proteins (p-Akt^Thr308, p-GSK3β^Ser9, p-AMPK^Thr172). As the mTOR pathway is the master regulator of autophagy, autophagy proteins were measured. There was an increase in p-Beclin-1 (BECN1), an autophagy regulator and activating molecule in Beclin-1-regulated autophagy (AMBRA1), a regulator of Beclin that play a role in autophagosome formation, an early stage of autophagy. There was a defect in the later stage of autophagy, the fusion of the autophagosome with the lysosome, known as autophagic flux, as evidenced by the lack of an increase in LC3-II, a marker of autophagosomes, with the lysosomal inhibitor bafilomycin, in both 70 day old and 150 day old hearts. To determine the role of autophagy in causing increased heart weight, Pkd1^RC/RC were treated with 2-deoxyglucose (2-DG) or Tat-Beclin1 peptide, agents known to induce autophagy. 2-DG treatment from 150 to 350 days of age, a time period when increased heart weight developed, did not reduce the increased heart weight. Unexpectedly, Tat-Beclin 1 peptide treatment from 70 to 120 days of age resulted in increased heart weight. In summary, there is suppressed autophagic flux in the heart at an early age in Pkd1^RC/RC mice. Increased mTOR signaling in older mice is associated suppressed autophagic flux. There was a large increase in p-AMPK^Thr172, a known autophagy inducer, in both young and old mice. 2-DG treatment did not impact increased heart weight and Tat-Beclin1 peptide increased heart weight.