Pasireotide is more effective than octreotide in reducing hepatorenal cystogenesis in rodents with polycystic kidney and liver diseases

Autosomal Dominant Polycystic Kidney Disease Therapies on the Horizon

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the formation of numerous kidney cysts which leads to kidney failure. ADPKD is responsible for approximately 10% of patients with kidney failure. Overwhelming evidence supports that vasopressin and its downstream cyclic adenosine monophosphate signaling promote cystogenesis, and targeting vasopressin 2 receptor with tolvaptan and other antagonists ameliorates cyst growth in preclinical studies. Tolvaptan is the only drug approved by Food and Drug Administration to treat ADPKD patients at the risk of rapid disease progression. A major limitation of the widespread use of tolvaptan is aquaretic events. This review discusses the potential strategies to improve the tolerability of tolvaptan, the progress on the use of an alternative vasopressin 2 receptor antagonist lixivaptan, and somatostatin analogs. Recent advances in understanding the pathophysiology of PKD have led to new approaches of treatment via targeting different signaling pathways. We review the new pharmacotherapies and dietary interventions of ADPKD that are promising in the preclinical studies and investigated in clinical trials.

Renal ciliopathies: promising drug targets and prospects for clinical trials

INTRODUCTION

Renal ciliopathies represent a collection of genetic disorders characterized by deficiencies in the biogenesis, maintenance, or functioning of the ciliary complex. These disorders, which encompass autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD), and nephronophthisis (NPHP), typically result in cystic kidney disease, renal fibrosis, and a gradual deterioration of kidney function, culminating in kidney failure.

AREAS COVERED

Here we review the advances in basic science and clinical research into renal ciliopathies which have yielded promising small compounds and drug targets, within both preclinical studies and clinical trials.

EXPERT OPINION

Tolvaptan is currently the sole approved treatment option available for ADPKD patients, while no approved treatment alternatives exist for ARPKD or NPHP patients. Clinical trials are presently underway to evaluate additional medications in ADPKD and ARPKD patients. Based on preclinical models, other potential therapeutic targets for ADPKD, ARPKD, and NPHP look promising. These include molecules targeting fluid transport, cellular metabolism, ciliary signaling and cell-cycle regulation. There is a real and urgent clinical need for translational research to bring novel treatments to clinical use for all forms of renal ciliopathies to reduce kidney disease progression and prevent kidney failure.

Multi-omics profiling of cholangiocytes reveals sex-specific chromatin state dynamics during hepatic cystogenesis in polycystic liver disease

BACKGROUND & AIMS

Cholangiocytes transit from quiescence to hyperproliferation during cystogenesis in polycystic liver disease (PLD), the severity of which displays prominent sex differences. Epigenetic regulation plays important roles in cell state transition. We aimed to investigate the sex-specific epigenetic basis of hepatic cystogenesis and to develop therapeutic strategies targeting epigenetic modifications for PLD treatment.

METHODS

Normal and cystic primary cholangiocytes were isolated from wild-type and PLD mice of both sexes. Chromatin states were characterized by analyzing chromatin accessibility (ATAC sequencing) and multiple histone modifications (chromatin immunoprecipitation sequencing). Differential gene expression was determined by transcriptomic analysis (RNA sequencing). Pharmacologic inhibition of epigenetic modifying enzymes was undertaken in PLD model mice.

RESULTS

Through genome-wide profiling of chromatin dynamics, we revealed a profound increase of global chromatin accessibility during cystogenesis in both male and female PLD cholangiocytes. We identified a switch from H3K9me3 to H3K9ac on cis-regulatory DNA elements of cyst-associated genes and showed that inhibition of H3K9ac acetyltransferase or H3K9me3 demethylase slowed cyst growth in male, but not female, PLD mice. In contrast, we found that H3K27ac was specifically increased in female PLD mice and that genes associated with H3K27ac-gained regions were enriched for cyst-related pathways. In an integrated epigenomic and transcriptomic analysis, we identified an estrogen receptor alpha-centered transcription factor network associated with the H3K27ac-regulated cystogenic gene expression program in female PLD mice.

CONCLUSIONS

Our findings highlight the multi-layered sex-specific epigenetic dynamics underlying cholangiocyte state transition and reveal a potential epigenetic therapeutic strategy for male PLD patients.

IMPACT AND IMPLICATIONS

In the present study, we elucidate a sex-specific epigenetic mechanism underlying the cholangiocyte state transition during hepatic cystogenesis and identify epigenetic drugs that effectively slow cyst growth in male PLD mice. These findings underscore the importance of sex difference in the pathogenesis of PLD and may guide researchers and physicians to develop sex-specific personalized approaches for PLD treatment.

Drug repurposing in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease is characterized by progressive kidney cyst formation that leads to kidney failure. Tolvaptan, a vasopressin 2 receptor antagonist, is the only drug approved to treat patients with autosomal dominant polycystic kidney disease who have rapid disease progression. The use of tolvaptan is limited by reduced tolerability from aquaretic effects and potential hepatotoxicity. Thus, the search for more effective drugs to slow down the progression of autosomal dominant polycystic kidney disease is urgent and challenging. Drug repurposing is a strategy for identifying new clinical indications for approved or investigational medications. Drug repurposing is increasingly becoming an attractive proposition because of its cost-efficiency and time-efficiency and known pharmacokinetic and safety profiles. In this review, we focus on the repurposing approaches to identify suitable drug candidates to treat autosomal dominant polycystic kidney disease and prioritization and implementation of candidates with high probability of success. Identification of drug candidates through understanding of disease pathogenesis and signaling pathways is highlighted.

Combining Metformin and Drug-Loaded Kidney-Targeting Micelles for Polycystic Kidney Disease

Introduction

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease that leads to eventual renal failure. Metformin (MET), an AMP-activated protein kinase (AMPK) activator already approved for type 2 diabetes, is currently investigated for ADPKD treatment. However, despite high tolerability, MET showed varying therapeutic efficacy in preclinical ADPKD studies. Thus, newer strategies have combined MET with other ADPKD small molecule drug candidates, thereby targeting multiple ADPKD-associated signaling pathways to enhance therapeutic outcomes through potential drug synergy. Unfortunately, the off-target side effects caused by these additional drug candidates pose a major hurdle. To address this, our group has previously developed kidney-targeting peptide amphiphile micelles (KMs), which displayed significant kidney accumulation in vivo, for delivering drugs to the site of the disease.

Methods

To mitigate the adverse effects of ADPKD drugs and evaluate their therapeutic potential in combination with MET, herein, we loaded KMs with ADPKD drug candidates including salsalate, octreotide, bardoxolone methyl, rapamycin, tolvaptan, and pioglitazone, and tested their in vitro therapeutic efficacy when combined with free MET. Specifically, after determining the 40% inhibitory concentration for each drug (IC40), the size, morphology, and surface charge of drug-loaded KMs were characterized. Next, drug-loaded KMs were applied in combination with MET to treat renal proximal tubule cells derived from Pkd1flox/-:TSLargeT mice in 2D proliferation and 3D cyst model.

Results

MET combined with all drug-loaded KMs demonstrated significantly enhanced efficacy as compared to free drugs in inhibiting cell proliferation and cyst growth. Notably, synergistic effects were found for MET and KMs loaded with either salsalate or rapamycin as determined by Bliss synergy scores.

Conclusion

Together, we show drug synergy using drug-loaded nanoparticles and free MET for the first time and present a novel nanomedicine-based combinatorial therapeutic approach for ADPKD with enhanced efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00753-9.

Emerging therapies for autosomal dominant polycystic kidney disease with a focus on cAMP signaling

Autosomal dominant polycystic kidney disease (ADPKD), with an estimated genetic prevalence between 1:400 and 1:1,000 individuals, is the third most common cause of end stage kidney disease after diabetes mellitus and hypertension. Over the last 3 decades there has been great progress in understanding its pathogenesis. This allows the stratification of therapeutic targets into four levels, gene mutation and polycystin disruption, proximal mechanisms directly caused by disruption of polycystin function, downstream regulatory and signaling pathways, and non-specific pathophysiologic processes shared by many other diseases. Dysfunction of the polycystins, encoded by the PKD genes, is closely associated with disruption of calcium and upregulation of cyclic AMP and protein kinase A (PKA) signaling, affecting most downstream regulatory, signaling, and pathophysiologic pathways altered in this disease. Interventions acting on G protein coupled receptors to inhibit of 3',5'-cyclic adenosine monophosphate (cAMP) production have been effective in preclinical trials and have led to the first approved treatment for ADPKD. However, completely blocking cAMP mediated PKA activation is not feasible and PKA activation independently from cAMP can also occur in ADPKD. Therefore, targeting the cAMP/PKA/CREB pathway beyond cAMP production makes sense. Redundancy of mechanisms, numerous positive and negative feedback loops, and possibly counteracting effects may limit the effectiveness of targeting downstream pathways. Nevertheless, interventions targeting important regulatory, signaling and pathophysiologic pathways downstream from cAMP/PKA activation may provide additive or synergistic value and build on a strategy that has already had success. The purpose of this manuscript is to review the role of cAMP and PKA signaling and their multiple downstream pathways as potential targets for emergent therapies for ADPKD.

Liver and spleen volume and stiffness in patients post-Fontan procedure and patients with ARPKD compared to normal controls

PURPOSE

Both congestive (patients post-Fontan hepatopathy) and congenital (patients with ARPKD) disease can lead to hepatic fibrosis and portal hypertension with eventual development of splenomegaly. We investigated liver and spleen stiffness as measured by MRE between post-Fontan, ARPKD patients and controls independent of organ volume.

METHODS

Our study included 122 subjects (70 Fontan patients, 14 ARPKD patients, and 38 controls). The mean MRE liver and spleen stiffness values of Fontan patients and patients with ARPKD were compared to controls. Similarly, the liver and spleen volumes of the Fontan patients and patients with ARPKD were then compared to the volumes of controls.

RESULTS

Post-Fontan and ARPKD patients, mean liver stiffness, mean liver volume as well as mean spleen stiffness and mean spleen volume were higher than mean liver stiffness, mean liver volume, mean spleen stiffness, and mean spleen volume of controls. While liver stiffness correlated to liver volume in controls, we found no correlation between stiffness and volume in either Fontan or ARPKD patients, which indicates MRE's ability to act as an independent biomarker. However, these findings are not true in the spleen, where there is significant association between volume and stiffness in patients with ARPKD, but not in Fontan patients or controls.

CONCLUSION

Liver and spleen stiffness and volumes are significantly different among Fontan patients, ARPKD patients, and controls. Our findings suggest that beyond diagnosing fibrosis, MRE cut-off values could be disease-specific since not only the severity but the underlying pathology causing organ congestion or fibrosis influences MRE results.

Genetics, pathobiology and therapeutic opportunities of polycystic liver disease

Polycystic liver diseases (PLDs) are inherited genetic disorders characterized by progressive development of intrahepatic, fluid-filled biliary cysts (more than ten), which constitute the main cause of morbidity and markedly affect the quality of life. Liver cysts arise in patients with autosomal dominant PLD (ADPLD) or in co-occurrence with renal cysts in patients with autosomal dominant or autosomal recessive polycystic kidney disease (ADPKD and ARPKD, respectively). Hepatic cystogenesis is a heterogeneous process, with several risk factors increasing the odds of developing larger cysts. Depending on the causative gene, PLDs can arise exclusively in the liver or in parallel with renal cysts. Current therapeutic strategies, mainly based on surgical procedures and/or chronic administration of somatostatin analogues, show modest benefits, with liver transplantation as the only potentially curative option. Increasing research has shed light on the genetic landscape of PLDs and consequent cholangiocyte abnormalities, which can pave the way for discovering new targets for therapy and the design of novel potential treatments for patients. Herein, we provide a critical and comprehensive overview of the latest advances in the field of PLDs, mainly focusing on genetics, pathobiology, risk factors and next-generation therapeutic strategies, highlighting future directions in basic, translational and clinical research.

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

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

2021 White Paper on Recent Issues in Bioanalysis: ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry (Part 2 - Recommendations on Biomarkers/CDx Assays Development & Validation, Cytometry Validation & Innovation, Biotherapeutics PK LBA Regulated Bioanalysis, Critical Reagents & Positive Controls Generation)

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included three Main Workshops and seven Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term "context of use" [COU]); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and critical reagent and positive control generation were the special features of the 15th edition. This 2021 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry. Part 1A (Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC), Part 1B (Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine) and Part 3 (TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparability & Cut Point Appropriateness) are published in volume 14 of Bioanalysis, issues 9 and 11 (2022), respectively.

Autophagy promotes hepatic cystogenesis in polycystic liver disease by depletion of cholangiocyte ciliogenic proteins

BACKGROUNDS AND AIMS

Polycystic liver disease (PLD) is characterized by defective cholangiocyte cilia that regulate progressive growth of hepatic cysts. Because formation of primary cilia is influenced by autophagy through degradation of proteins involved in ciliogenesis, we hypothesized that ciliary defects in PLD cholangiocytes (PLDCs) originate from autophagy-mediated depletion of ciliogenic proteins ADP-ribosylation factor-like protein 3 (ARL3) and ADP-ribosylation factor-like protein 13B (ARL13B) and ARL-dependent mislocation of a ciliary-localized bile acid receptor, Takeda G-protein-coupled receptor 5 (TGR5), the activation of which enhances hepatic cystogenesis (HCG). The aims here were to determine whether: (1) ciliogenesis is impaired in PLDC, is associated with increased autophagy, and involves autophagy-mediated depletion of ARL3 and ARL13B; (2) depletion of ARL3 and ARL13B in PLDC cilia impacts ciliary localization of TGR5; and (3) pharmacological inhibition of autophagy re-establishes cholangiocyte cilia and ciliary localization of ARL3, ARL3B, and TGR5 and reduces HCG.

APPROACH AND RESULTS

By using liver tissue from healthy persons and patients with PLD, in vitro and in vivo models of PLD, and in vitro models of ciliogenesis, we demonstrated that, in PLDCs: ciliogenesis is impaired; autophagy is enhanced; ARL3 and ARL13B are ubiquitinated by HDAC6, depleted in cilia, and present in autophagosomes; depletion of ARL3 and ARL13B impacts ciliary localization of TGR5; and pharmacological inhibition of autophagy with mefloquine and verteporfin re-establishes cholangiocyte cilia and ciliary localization of ARL3, ARL13B, and TGR5 and reduces HCG.

CONCLUSIONS

The intersection between autophagy, defective cholangiocyte cilia, and enhanced HCG contributes to PLD progression and can be considered a target for therapeutic interventions.

Polycystic Liver Disease: Advances in Understanding and Treatment

Polycystic liver disease (PLD) is a group of genetic disorders characterized by progressive development of cholangiocyte-derived fluid-filled hepatic cysts. PLD is the most common manifestation of autosomal dominant and autosomal recessive polycystic kidney diseases and rarely occurs as autosomal dominant PLD. The mechanisms of PLD are a sequence of the primary (mutations in PLD-causative genes), secondary (initiation of cyst formation), and tertiary (progression of hepatic cystogenesis) interconnected molecular and cellular events in cholangiocytes. Nonsurgical, surgical, and limited pharmacological treatment options are currently available for clinical management of PLD. Substantial evidence suggests that pharmacological targeting of the signaling pathways and intracellular processes involved in the progression of hepatic cystogenesis is beneficial for PLD. Many of these targets have been evaluated in preclinical and clinical trials. In this review, we discuss the genetic, molecular, and cellular mechanisms of PLD and clinical and preclinical treatment strategies. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Two-dimensional (2D) morphologic measurements can quantify the severity of liver disease in children with autosomal recessive polycystic kidney disease (ARPKD)

PURPOSE

To evaluate the correlation of 2D shape-based features with magnetic resonance elastography (MRE)-derived liver stiffness and portal hypertension (pHTN) in children with ARPKD-associated congenital hepatic fibrosis.

METHODS

In a prospective IRB-approved study, 14 children with ARPKD (mean age ± SD = 13.8 ± 5.8 years) and 14 healthy controls (mean age ± SD = 13.7 ± 3.9 years) underwent liver MRE. A 2D region of interest (ROI) outlining the left liver lobe at the level of the abdominal aorta was drawn on sagittal T2-weighted images. Eight shape features (perimeter, major axis length, maximum diameter, perimeter to surface ratio (PSR), elongation, sphericity, minor axis length, and mesh surface) describing the 2D-ROI were calculated. Spearman's correlation was calculated between shape features and MRE-derived liver stiffness (kPa) (n = 28). Shape features were compared between participants with ARPKD with pHTN (splenomegaly and thrombocytopenia), (n = 4) and without pHTN (n = 8) using the Mann Whitney U test. Receiver operating characteristic (ROC) curves were generated to examine the diagnostic accuracy of shape features in identifying cases with liver stiffness > 2.9 kPa.

RESULTS

In ARPKD participants and healthy controls, all eight shape features, except elongation, showed moderate to strong correlation with liver stiffness (kPa); the perimeter surface ratio had the strongest correlation (rho = - 0.75, p < 0.001). In ROC analysis, a cut-off of PSR ≤ 0.057 mm^-1 gave 100% (95% CI: 59.0-100.0) sensitivity and 100% (95% CI: 83.9-100.0) specificity in identifying ARPKD participants with liver stiffness > 2.9 kPa, with an area under the ROC curve (AUC) of 1.0 (95% CI: 0.88-1.00). Individuals with pHTN had a lower median PSR (mean ± SD = 0.05 ± 0.01) than those without (0.07 ± 0.01; p = 0.027) with an AUC of 0.91 (95% CI: 0.60-0.99) in differentiating the participants with and without pHTN.

CONCLUSION

Shape-based features of the left liver lobe show potential as non-invasive biomarkers of liver fibrosis and portal hypertension in children with ARPKD.

Autophagy-mediated reduction of miR-345 contributes to hepatic cystogenesis in polycystic liver disease

Background & Aims

Polycystic liver disease (PLD) is characterised by increased autophagy and reduced miRNA levels in cholangiocytes. Given that autophagy has been implicated in miRNA regulation, we tested the hypothesis that increased autophagy accounts for miRNA reduction in PLD cholangiocytes (PLDCs) and accelerated hepatic cystogenesis.

Methods

We assessed miRNA levels in cultured normal human cholangiocytes (NHCs), PLDCs, and isolated PLDC autophagosomes by miRNA-sequencing (miRNA-seq), and miRNA targets by mRNA-seq. Levels of miR-345 and miR-345-targeted proteins in livers of animals and humans with PLD, in NHCs and PLDCs, and in PLDCs transfected with pre-miR-345 were assessed by in situ hybridisation (ISH), quantitative PCR, western blotting, and fluorescence confocal microscopy. We also assessed cell proliferation and cyst growth in vitro, and hepatic cystogenesis in vivo.

Results

In total, 81% of miRNAs were decreased in PLDCs, with levels of 10 miRNAs reduced by more than 10 times; miR-345 was the most-reduced miRNA. In silico analysis and luciferase reporter assays showed that miR-345 targets included cell-cycle and cell-proliferation-related genes [i.e. cell division cycle 25A (CDC25A), cyclin-dependent kinase 6 (CDK6), E2F2, and proliferating cell nuclear antigen (PCNA)]; levels of 4 studied miR-345 targets were increased in PLDCs at both the mRNA and protein levels. Transfection of PLDCs with pre-miR-345 increased miR-345 and decreased the expression of miR-345-targeted proteins, cell proliferation, and cyst growth in vitro. MiR-345 accumulated in autophagosomes in PLDCs but not NHCs. Inhibition of autophagy increased miR-345 levels, decreased the expression of miR-345-targeted proteins, and reduced hepatic cystogenesis in vitro and in vivo.

Conclusion

Autophagy-mediated reduction of miR-345 in PLDCs (i.e. miRNAutophagy) accelerates hepatic cystogenesis. Inhibition of autophagy restores miR-345 levels, decreases cyst growth, and is beneficial for PLD.

Lay summary

Polycystic liver disease (PLD) is an incurable genetic disorder characterised by the progressive growth of hepatic cysts. We found that hepatic cystogenesis is increased when the levels of miR-345 in PLD cholangiocytes (PLDCs) are reduced by autophagy. Restoration of miR-345 in PLDCs via inhibition of autophagy decreases hepatic cystogenesis and thus, is beneficial for PLD.

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The miRNA profile is altered in PLD.

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MiR-345 is the most-reduced miRNA in PLDCs.

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The reduction of miR-345 increases PLDC proliferation and hepatic cystogenesis.

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MiR-345 in PLDCs is regulated by autophagy, termed ‘miRNAutophagy’.

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Restoration of miR-345 in PLDC is beneficial for PLD.

Predictors of progression in autosomal dominant and autosomal recessive polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are characterized by bilateral cystic kidney disease leading to progressive kidney function decline. These diseases also have distinct liver manifestations. The range of clinical presentation and severity of both ADPKD and ARPKD is much wider than was once recognized. Pediatric and adult nephrologists are likely to care for individuals with both diseases in their lifetimes. This article will review genetic, clinical, and imaging predictors of kidney and liver disease progression in ADPKD and ARPKD and will briefly summarize pharmacologic therapies to prevent progression.

Inhibition of NAE-dependent protein hyper-NEDDylation in cystic cholangiocytes halts cystogenesis in experimental models of polycystic liver disease

Background

Polycystic liver diseases (PLDs) are genetic inherited disorders characterized by the progressive growth of numerous intrahepatic biliary cysts, which are the main cause of morbidity. Previous studies revealed that cystic cholangiocytes are characterized by endoplasmic reticulum stress and aberrant posttranslational modification (PTM) of proteins, in particular hyper‐SUMOylation, that promote PLD pathobiology. Protein NEDDylation is a newly characterized PTM that modulates a plethora of biological processes and its dysregulation is associated with the development and progression of several human diseases. However, the role of NEDDylation in PLD remains elusive.

Objective

To explore the role of protein NEDDylation in PLD and its potential therapeutic regulatory value.

Methods

Levels and functional effects of NEDDylation, including response to Pevonedistat (first‐in‐class selective inhibitor of the NEDDylation E1 enzyme NAE), were assessed in vitro, in vivo, and/or in patients with PLD. NEDDylated protein levels in normal and cystic human cholangiocytes were assessed by immunoprecipitation, and the proteomic profile was further analyzed by mass spectrometry.

Results and Conclusion

The genes involved in the NEDDylation pathway were found overexpressed (mRNA) in polycystic human and rat liver tissue, as well as in cystic cholangiocytes in culture, compared to controls. Elevated levels of NEDDylated proteins were further confirmed in cystic cholangiocytes in vitro, which diminished under Pevonedistat incubation. Pevonedistat promoted apoptotic cell death and reduced proliferation in cystic cholangiocytes in vitro. Comparative proteomic profiling of NEDD8‐immunoprecipitated proteins between normal and cystic cholangiocytes in culture reported candidate proteins involved in cystogenesis, mostly associated with protein biogenesis and quality control. All these data indicate that cystic cholangiocytes display increased protein NEDDylation, contributing to cell survival and proliferation, ultimately supporting hepatic cystogenesis. Targeting of protein hyper‐NEDDylation in cystic cholangiocytes inhibits cystogenesis in experimental models, representing a novel therapeutic opportunity in PLD.

The cellular pathways and potential therapeutics of Polycystic Kidney Disease

Polycystic Kidney Disease (PKD) refers to a group of disorders, driven by the formation of cysts in renal tubular cells and is currently one of the leading causes of end-stage renal disease. The range of symptoms observed in PKD is due to mutations in cilia-localising genes, resulting in changes in cellular signalling. As such, compounds that are currently in preclinical and clinical trials target some of these signalling pathways that are dysregulated in PKD. In this review, we highlight these pathways including cAMP, EGF and AMPK signalling and drugs that target them and may show promise in lessening the disease burden of PKD patients. At present, tolvaptan is the only approved therapy for ADPKD, however, it carries several adverse side effects whilst comparatively, no pharmacological drug is approved for ARPKD treatment. Aside from this, drugs that have been the subject of multiple clinical trials such as metformin, which targets AMPK signalling and somatostatins, which target cAMP signalling have shown great promise in reducing cyst formation and cellular proliferation. This review also discusses other potential and novel targets that can be used for future interventions, such as β-catenin and TAZ, where research has shown that a reduction in the overexpression of these signalling components results in amelioration of disease phenotype. Thus, it becomes apparent that well-designed preclinical investigations and future clinical trials into these pathways and other potential signalling targets are crucial in bettering disease prognosis for PKD patients and could lead to personalised therapy approaches.

Fibrocystic liver disease: novel concepts and translational perspectives

Fibrocystic liver diseases (FLDs) comprise a heterogeneous group of rare diseases of the biliary tree, having in common an abnormal development of the embryonic ductal plate caused by genetically-determined dysfunctions of proteins expressed in the primary cilia of cholangiocytes (and therefore grouped among the "ciliopathies"). The ductal dysgenesis may affect the biliary system at multiple levels, from the small intrahepatic bile ducts [congenital hepatic fibrosis (CHF)], to the larger intrahepatic bile ducts [Caroli disease (CD), or Caroli syndrome (CS), when CD coexists with CHF], leading to biliary microhamartomas and segmental bile duct dilations. Biliary changes are accompanied by progressive deposition of abundant peribiliary fibrosis. Peribiliary fibrosis and biliary cysts are the fundamental lesions of FLDs and are responsible for the main clinical manifestations, such as portal hypertension, recurrent cholangitis, cholestasis, sepsis and eventually cholangiocarcinoma. Furthermore, FLDs often associate with a spectrum of disorders affecting primarily the kidney. Among them, the autosomal recessive polycystic kidney disease (ARPKD) is the most frequent, and the renal function impairment is central in disease progression. CHF, CD/CS, and ARPKD are caused by a number of mutations in polycystic kidney hepatic disease 1 (PKHD1), a gene that encodes for fibrocystin/polyductin, a protein of unclear function, but supposedly involved in planar cell polarity and other fundamental cell functions. Targeted medical therapy is not available yet and thus the current treatment aims at controlling the complications. Interventional radiology or surgical treatments, including liver transplantation, are used in selected cases.

Limitations and opportunities in the pharmacotherapy of ciliopathies

Ciliopathies are a family of rather diverse conditions, which have been grouped based on the finding of altered or dysfunctional cilia, potentially motile, small cellular antennae extending from the surface of postmitotic cells. Cilia-related disorders include embryonically arising conditions such as Joubert, Usher or Kartagener syndrome, but also afflictions with a postnatal or even adult onset phenotype, i.e. autosomal dominant polycystic kidney disease. The majority of ciliopathies are syndromic rather than affecting only a single organ due to cilia being found on almost any cell in the human body. Overall ciliopathies are considered rare diseases. Despite that, pharmacological research and the strive to help these patients has led to enormous therapeutic advances in the last decade. In this review we discuss new treatment options for certain ciliopathies, give an outlook on promising future therapeutic strategies, but also highlight the limitations in the development of therapeutic approaches of ciliopathies.

New insights on the role of vascular endothelial growth factor in biliary pathophysiology

The family of vascular endothelial growth factors (VEGFs) includes 5 members (VEGF-A to -D, and placenta growth factor), which regulate several critical biological processes. VEGF-A exerts a variety of biological effects through high-affinity binding to tyrosine kinase receptors (VEGFR-1, -2 and -3), co-receptors and accessory proteins. In addition to its fundamental function in angiogenesis and endothelial cell biology, VEGF/VEGFR signalling also plays a role in other cell types including epithelial cells. This review provides an overview of VEGF signalling in biliary epithelial cell biology in both normal and pathologic conditions. VEGF/VEGFR-2 signalling stimulates bile duct proliferation in an autocrine and paracrine fashion. VEGF/VEGFR-1/VEGFR-2 and angiopoietins are involved at different stages of biliary development. In certain conditions, cholangiocytes maintain the ability to secrete VEGF-A, and to express a functional VEGFR-2 receptor. For example, in polycystic liver disease, VEGF secreted by cystic cells stimulates cyst growth and vascular remodelling through a PKA/RAS/ERK/HIF1α-dependent mechanism, unveiling a new level of complexity in VEFG/VEGFR-2 regulation in epithelial cells. VEGF/VEGFR-2 signalling is also reactivated during the liver repair process. In this context, pro-angiogenic factors mediate the interactions between epithelial, mesenchymal and inflammatory cells. This process takes place during the wound healing response, however, in chronic biliary diseases, it may lead to pathological neo-angiogenesis, a condition strictly linked with fibrosis progression, the development of cirrhosis and related complications, and cholangiocarcinoma. Novel observations indicate that in cholangiocarcinoma, VEGF is a determinant of lymphangiogenesis and of the immune response to the tumour. Better insights into the role of VEGF signalling in biliary pathophysiology might help in the search for effective therapeutic strategies.

Magnetic resonance elastography to quantify liver disease severity in autosomal recessive polycystic kidney disease

OBJECTIVES

To evaluate whether liver and spleen magnetic resonance elastography (MRE) can measure the severity of congenital hepatic fibrosis (CHF) and portal hypertension (pHTN) in individuals with autosomal recessive polycystic kidney disease (ARPKD), and to examine correlations between liver MRE and ultrasound (US) elastography.

METHODS

Cross-sectional study of nine individuals with ARPKD and 14 healthy controls. MRE was performed to measure mean liver and spleen stiffness (kPa); US elastography was performed to measure point shear wave speed (SWS) in both liver lobes. We compared: (1) MRE liver and spleen stiffness between controls vs. ARPKD; and (2) MRE liver stiffness between participants with ARPKD without vs. with pHTN, and examined correlations between MRE liver stiffness, spleen length, platelet counts, and US elastography SWS. Receiver operating characteristic (ROC) analysis was performed to examine diagnostic accuracy of liver MRE.

RESULTS

Participants with ARPKD (median age 16.8 [IQR 13.3, 18.9] years) had higher median MRE liver stiffness than controls (median age 14.7 [IQR 9.7, 16.7 years) (2.55 vs. 1.92 kPa, p = 0.008), but MRE spleen stiffness did not differ. ARPKD participants with pHTN had higher median MRE liver stiffness than those without (3.60 kPa vs 2.49 kPa, p = 0.05). Liver MRE and US elastography measurements were strongly correlated. To distinguish ARPKD vs. control groups, liver MRE had 78% sensitivity and 93% specificity at a proposed cut-off of 2.48 kPa [ROC area 0.83 (95% CI 0.63-1.00)].

CONCLUSION

Liver MRE may be a useful quantitative method to measure the severity of CHF and pHTN in individuals with ARPKD.

Prostaglandins as potential targets for the treatment of polycystic kidney disease

Polycystic kidney disease (PKD) is characterized by the proliferation of fluid-filled kidney cysts that enlarge over time, causing damage to the surrounding kidney and ultimately resulting in kidney failure. Both increased cell proliferation and fluid secretion are stimulated by increased cyclic adenosine monophosphate (cAMP) in PKD kidneys, so many treatments for the disease target cAMP lowering. Prostaglandins (PG) levels are elevated in multiple animal models of PKD and mediate many of their effects by elevating cAMP levels. Inhibiting the production of PG with cyclooxygenase 2 (COX2) inhibitors reduces PG levels and reduces disease progression. However, COX inhibitors also block beneficial PG and can cause nephrotoxicity. In an orthologous model of the main form of PKD, PGD₂ and PGI₂ were the two PG highest in kidneys and most affected by a COX2 inhibitor. Future studies are needed to determine whether specific blockage of PGD₂ and/or PGI₂ activity would lead to more targeted and effective treatments with fewer undesirable side-effects.

Somatostatin in renal physiology and autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation, leading to growth in kidney volume and renal function decline. Although therapies have emerged, there is still an important unmet need for slowing the rate of disease progression in ADPKD. High intracellular levels of adenosine 3′,5′-cyclic monophosphate (cAMP) are involved in cell proliferation and fluid secretion, resulting in cyst formation. Somatostatin (SST), a hormone that is involved in many cell processes, has the ability to inhibit intracellular cAMP production. However, SST itself has limited therapeutic potential since it is rapidly eliminated in vivo. Therefore analogues have been synthesized, which have a longer half-life and may be promising agents in the treatment of ADPKD. This review provides an overview of the complex physiological effects of SST, in particular renal, and the potential therapeutic role of SST analogues in ADPKD.

Pansomatostatin Agonist Pasireotide Long-Acting Release for Patients with Autosomal Dominant Polycystic Kidney or Liver Disease with Severe Liver Involvement: A Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

We assessed safety and efficacy of another somatostatin receptor analog, pasireotide long-acting release, in severe polycystic liver disease and autosomal dominant polycystic kidney disease. Pasireotide long-acting release, with its broader binding profile and higher affinity to known somatostatin receptors, has potential for greater efficacy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Individuals with severe polycystic liver disease were assigned in a 2:1 ratio in a 1-year, double-blind, randomized trial to receive pasireotide long-acting release or placebo. Primary outcome was change in total liver volume; secondary outcomes were change in total kidney volume, eGFR, and quality of life.

RESULTS

Of 48 subjects randomized, 41 completed total liver volume measurements (n=29 pasireotide long-acting release and n=12 placebo). From baseline, there were -99±189 ml/m absolute and -3%±7% change in annualized change in height-adjusted total liver volume (from 2582±1381 to 2479±1317 ml/m) in the pasireotide long-acting release group compared with 136±117 ml/m absolute and 6%±7% increase (from 2387±759 to 2533±770 ml/m) in placebo (P<0.001 for both). Total kidney volumes decreased by -12±34 ml/m and -1%±4% in pasireotide long-acting release compared with 21±21 ml/m and 4%±5% increase in the placebo group (P=0.05 for both). Changes in eGFR were similar between groups. Among the n=48 randomized, adverse events included hyperglycemia (26 of 33 [79%] in pasireotide long-acting release versus four of 15 [27%] in the placebo group; P<0.001), and among the 47 without diabetes at baseline, 19 of 32 (59%) in the pasireotide long-acting release group versus one of 15 (7%) in the placebo group developed diabetes (P=0.001).

CONCLUSIONS

Another somatostatin analog, pasireotide long-acting release, slowed progressive increase in both total liver volume/total kidney volume growth rates without affecting GFR decline. Participants experienced higher frequency of adverse events (hyperglycemia and diabetes).

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Pasireotide LAR in Severe Polycystic Liver Disease, NCT01670110 PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2020_08_28_CJN13661119.mp3.

Modulation of polycystic kidney disease by G-protein coupled receptors and cyclic AMP signaling

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a systemic disorder associated with polycystic liver disease (PLD) and other extrarenal manifestations, the most common monogenic cause of end-stage kidney disease, and a major burden for public health. Many studies have shown that alterations in G-protein and cAMP signaling play a central role in its pathogenesis. As for many other diseases (35% of all approved drugs target G-protein coupled receptors (GPCRs) or proteins functioning upstream or downstream from GPCRs), treatments targeting GPCR have shown effectiveness in slowing the rate of progression of ADPKD. Tolvaptan, a vasopressin V2 receptor antagonist is the first drug approved by regulatory agencies to treat rapidly progressive ADPKD. Long-acting somatostatin analogs have also been effective in slowing the rates of growth of polycystic kidneys and liver. Although no treatment has so far been able to prevent the development or stop the progression of the disease, these encouraging advances point to G-protein and cAMP signaling as a promising avenue of investigation that may lead to more effective and safe treatments. This will require a better understanding of the relevant GPCRs, G-proteins, cAMP effectors, and of the enzymes and A-kinase anchoring proteins controlling the compartmentalization of cAMP signaling. The purpose of this review is to provide an overview of general GPCR signaling; the function of polycystin-1 (PC1) as a putative atypical adhesion GPCR (aGPCR); the roles of PC1, polycystin-2 (PC2) and the PC1-PC2 complex in the regulation of calcium and cAMP signaling; the cross-talk of calcium and cAMP signaling in PKD; and GPCRs, adenylyl cyclases, cyclic nucleotide phosphodiesterases, and protein kinase A as therapeutic targets in ADPKD.

Polycystic liver disease: Classification, diagnosis, treatment process, and clinical management

Polycystic liver disease (PLD) is a rare hereditary disease that independently exists in isolated PLD, or as an accompanying symptom of autosomal dominant polycystic kidney disease and autosomal recessive polycystic kidney disease with complicated mechanisms. PLD currently lacks a unified diagnostic standard. The diagnosis of PLD is usually made when the number of hepatic cysts is more than 20. Gigot classification and Schnelldorfer classification are now commonly used to define severity in PLD. Most PLD patients have no clinical symptoms, and minority with severe complications need treatments. Somatostatin analogues, mammalian target of rapamycin inhibitor, ursodeoxycholic acid and vasopressin-2 receptor antagonist are the potentially effective medical therapies, while cyst aspiration and sclerosis, transcatheter arterial embolization, fenestration, hepatic resection and liver transplantation are the options of invasion therapies. However, the effectiveness of these therapies except liver transplantation are still uncertain. Furthermore, there is no unified strategy to treat PLD between medical centers at present. In order to better understand recent study progresses on PLD for clinical practice and obtain potential directions for future researches, this review mainly focuses on the recent progress in PLD classification, clinical manifestation, diagnosis and treatment. For information, we also provided medical treatment processes of PLD in our medical center.

The positive effect of selective prostaglandin E2 receptor EP2 and EP4 blockade on cystogenesis in vitro is counteracted by increased kidney inflammation in vivo

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major cause of end-stage kidney disease in man. The central role of cyclic adenosine monophosphate (cAMP) in ADPKD pathogenesis has been confirmed by numerous studies including positive clinical trial data. Here, we investigated the potential role of another major regulator of renal cAMP, prostaglandin E₂ (PGE₂), in modifying disease progression in ADPKD models using selective receptor modulators to all four PGE₂ receptor subtypes (EP1-4). In 3D-culture model systems utilizing dog (MDCK) and patient-derived (UCL93, OX161-C1) kidney cell lines, PGE₂ strikingly promoted cystogenesis and inhibited tubulogenesis by stimulating proliferation while reducing apoptosis. The effect of PGE₂ on tubulogenesis and cystogenesis in 3D-culture was mimicked or abolished by selective EP2 and EP4 agonists or antagonists but not those specific to EP1 or EP3. In a Pkd1 mouse model (Pkd1^nl/nl), kidney PGE₂ and COX-2 expression were increased by two-fold at the peak of disease (week four). However, Pkd1^nl/nl mice treated with selective EP2 (PF-04418948) or EP4 (ONO-AE3-208) antagonists from birth for three weeks had more severe cystic disease and fibrosis associated with increased cell proliferation and macrophage infiltration. A similar effect was observed for the EP4 antagonist ONO-AE3-208 in a second Pkd1 model (Pax8rtTA-TetO-Cre-Pkd1^f/f). Thus, despite the positive effects of slowing cyst growth in vitro, the more complex effects of inhibiting EP2 or EP4 in vivo resulted in a worse outcome, possibly related to unexpected pro-inflammatory effects.

Long-acting somatostatin analogue treatments in autosomal dominant polycystic kidney disease and polycystic liver disease: a systematic review and meta-analysis

OBJECTIVES

A number of randomised control trials (RCTs) investigating the effects of long-acting somatostatin analogues in autosomal dominant polycystic kidney disease (ADPKD) and polycystic liver disease (PLD) have been recently reported. We sought to evaluate all available RCTs investigating the efficacy of somatostatin analogues treatment in ADPKD and PLD.

DATA SOURCES

Electronic databases; Pubmed, Clincaltrials.gov and Cochrane Central Register of Controlled Trials ELIGIBILITY CRITERIA FOR SELECTING STUDIES: RCTs and randomised cross-over trials comparing the effects of somatostatin analogue treatment with controls in patients with ADPKD or PLD.

DATA EXTRACTION AND SYNTHESIS

Data extraction and bias assessments were performed by two independent reviewers between January and May 2019. Outcomes assessed included estimated glomerular filtration rate (eGFR), total kidney volume (TKV), total liver volume (TLV), progression to end stage renal failure (ESRF) and adverse effects. Data were pooled using a random-effects model and reported as relative risk or mean difference with 95% CIs.

RESULTS

Meta-analysis was performed of six RCTs or randomised cross-over trials and three secondary analyses. A total of 592 patients were included. Compared with controls, somatostatin analogue treatment significantly reduced TLV (mean difference -0.15 L, 95% CI -0.26 to -0.03, p=0.01). There was no significant effect on TKV (mean difference -0.19 L, 95% CI -0.50 to 0.12, p=0.23) or eGFR (mean difference 0.27 mL/min/1.73 m², 95% CI -2.03 to 2.57, p=0.82). There was no effect on progression to ESRF. Somatostatin analogues were associated with known adverse effects such as gastrointestinal symptoms.

CONCLUSIONS

The available RCT data show improvement in TLV with somatostatin analogue treatment. There was no benefit to TKV or eGFR in patients with ADPKD, while being associated with various side effects. Further studies are needed to assess potential benefit in reducing cyst burden in patients with PLD.

The relationship between liver cyst volume and QOL in Japanese ADPKD patients

BACKGROUND

Although it is widely accepted that the autosomal dominant polycystic kidney disease (ADPKD) patients with large liver cysts have a significant decrement in quality of life (QOL), there is insufficient evidence that clearly demonstrates the relationship between the size of the liver cysts and QOL. Therefore, we started this prospective longitudinal study to investigate the impact of liver cysts on QOL.

METHODS

We grouped the 111 included ADPKD patients into 4 groups (control group A; < 25%, group B; 25-49%, group C; 50-75%, group D; > 75%) according to liver cysts-parenchyma ratio (CPR). QOL was measured by FANLTC + FACT-Hep scores. We compared QOL scores and several clinical parameters amongst these groups for 3 years.

RESULTS

The number of patients in group A, B, C, and D was 31, 14, 14, and 23, respectively. Although there were no significant differences in AST (p = 0.107), ALT (p = 0.925), and serum albumin (p = 0.212) between the four groups, platelet count was significantly decreased along with the extension of cyst volume (p = 0.030). Overall, the mean FANLTC and FACT-Hep scores were 71.8 ± 12.5, and 32.4 ± 5.8, respectively. FANLTC (p = 0.017) and FACT-Hep scores (p = 0.003) were significantly decreased with increasing cyst volume. From the data collected at the time of registration, multivariate linear regression analysis demonstrated that the CPR had a significant influence on FANLTC and FACT-Hep scores.

CONCLUSION

In this cross-sectional and prospective longitudinal study, we demonstrate the relationship between liver cyst volume and QOL in ADPKD patients. We hope to establish the long-term influence on QOL in this ongoing prospective longitudinal study.

The pathobiology of polycystic kidney disease from a metabolic viewpoint

Autosomal dominant polycystic kidney disease (ADPKD) affects an estimated 1 in 1,000 people and slowly progresses to end-stage renal disease (ESRD) in about half of these individuals. Tolvaptan, a vasopressin 2 receptor blocker, has been approved by regulatory authorities in many countries as a therapy to slow cyst growth, but additional treatments that target dysregulated signalling pathways in cystic kidney and liver are needed. Metabolic reprogramming is a prominent feature of cystic cells and a potentially important contributor to the pathophysiology of ADPKD. A number of pathways previously implicated in the pathogenesis of the disease, such as dysregulated mTOR and primary ciliary signalling, have roles in metabolic regulation and may exert their effects through this mechanism. Some of these pathways are amenable to manipulation through dietary modifications or drug therapies. Studies suggest that polycystin-1 and polycystin-2, which are encoded by PKD1 and PKD2, respectively (the genes that are mutated in >99% of patients with ADPKD), may in part affect cellular metabolism through direct effects on mitochondrial function. Mitochondrial dysfunction could alter the redox state and cellular levels of acetyl-CoA, resulting in altered histone acetylation, gene expression, cytoskeletal architecture and response to cellular stress, and in an immunological response that further promotes cyst growth and fibrosis.

Pathobiology of inherited biliary diseases: a roadmap to understand acquired liver diseases

Bile duct epithelial cells, also known as cholangiocytes, regulate the composition of bile and its flow. Acquired, congenital and genetic dysfunctions in these cells give rise to a set of diverse and complex diseases, often of unknown aetiology, called cholangiopathies. New knowledge has been steadily acquired about genetic and congenital cholangiopathies, and this has led to a better understanding of the mechanisms of acquired cholangiopathies. This Review focuses on findings from studies on Alagille syndrome, polycystic liver diseases, fibropolycystic liver diseases (Caroli disease and congenital hepatic fibrosis) and cystic fibrosis-related liver disease. In particular, knowledge on the role of Notch signalling in biliary repair and tubulogenesis has been advanced by work on Alagille syndrome, and investigations in polycystic liver diseases have highlighted the role of primary cilia in biliary pathophysiology and the concept of biliary angiogenic signalling and its role in cyst growth and biliary repair. In fibropolycystic liver disease, research has shown that loss of fibrocystin generates a signalling cascade that increases β-catenin signalling, activates the NOD-, LRR- and pyrin domain-containing 3 inflammasome, and promotes production of IL-1β and other chemokines that attract macrophages and orchestrate the process of pericystic and portal fibrosis, which are the main mechanisms of progression in cholangiopathies. In cystic fibrosis-related liver disease, lack of cystic fibrosis transmembrane conductance regulator increases the sensitivity of epithelial Toll-like receptor 4 that sustains the secretion of nuclear factor-κB-dependent cytokines and peribiliary inflammation in response to gut-derived products, providing a model for primary sclerosing cholangitis. These signalling mechanisms may be targeted therapeutically and they offer a possibility for the development of novel treatments for acquired cholangiopathies.

Ultrasound Elastography to Quantify Liver Disease Severity in Autosomal Recessive Polycystic Kidney Disease

OBJECTIVES

To evaluate the diagnostic accuracy of ultrasound elastography with acoustic radiation force impulse (ARFI) to detect congenital hepatic fibrosis and portal hypertension in children with autosomal recessive polycystic kidney disease (ARPKD).

STUDY DESIGN

Cross-sectional study of 25 children with ARPKD and 24 healthy controls. Ultrasound ARFI elastography (Acuson S3000, Siemens Medical Solutions USA, Inc, Malvern, Pennsylvania) was performed to measure shear wave speed (SWS) in the right and left liver lobes and the spleen. Liver and spleen SWS were compared in controls vs ARPKD, and ARPKD without vs with portal hypertension. Linear correlations between liver and spleen SWS, spleen length, and platelet counts were analyzed. Receiver operating characteristic analysis was used to evaluate diagnostic accuracy of ultrasound ARFI elastography.

RESULTS

Participants with ARPKD had significantly higher median liver and spleen SWS than controls. At a proposed SWS cut-off value of 1.56 m/s, the left liver lobe had the highest sensitivity (92%) and specificity (96%) for distinguishing participants with ARPKD from controls (receiver operating characteristic area 0.92; 95% CI 0.82-1.00). Participants with ARPKD with portal hypertension (splenomegaly and low platelet counts) had significantly higher median liver and spleen stiffness than those without portal hypertension. The left liver lobe also had the highest sensitivity and specificity for distinguishing subjects with ARPKD with portal hypertension.

CONCLUSIONS

Ultrasound ARFI elastography of the liver and spleen, particularly of the left liver lobe, is a useful noninvasive biomarker to detect and quantify liver fibrosis and portal hypertension in children with ARPKD.

Cyclooxygenase 2 inhibition slows disease progression and improves the altered renal lipid mediator profile in the Pkd2WS25/- mouse model of autosomal dominant polycystic kidney disease

BACKGROUND

Increased levels of cyclooxygenase (COX) derived oxylipins is the earliest and most consistent alteration in the renal oxylipin profile in diverse models of cystic kidney diseases. Therefore, we examined whether a COX2 inhibitor would reduce disease progression in the Pkd2WS25/- mouse model of autosomal dominant polycystic kidney disease (ADPKD).

METHODS

Weanling normal and diseased male Pkd2 mice were provided diets that provided 0 or 50 mg celecoxib/kg body weight/day, for 13 weeks. Renal disease and function were assessed by histomorphometric analysis of renal cysts and measurement of serum creatinine and urea nitrogen (SUN) levels. Targeted lipidomic analysis of renal oxylipins was performed by HPLC-MS/MS.

RESULTS

Diseased mice had significant cyst involvement and reduced renal function as indicated by elevated serum creatinine and SUN. Celecoxib reduced cyst area by 48%, cyst volume by 70%, and serum creatinine and SUN by 20% and 16%, respectively. Consistent with our previous studies, 8 of the 11 COX derived oxylipins were higher in diseased kidneys. In addition, 24 of 33 lipoxygenase (LOX) derived oxylipins and 7 of 16 cytochrome P450 (CYP) derived oxylipins were lower in diseased kidneys. Celecoxib reduced total and five of the eight individual elevated COX oxylipins and increased 5 of 24 LOX and 5 of 7 CYP oxylipins that were reduced by disease.

CONCLUSIONS

COX2 inhibition ameliorates disease progression, improves renal function and improves the altered oxylipins in Pkd2 mice. This represents a potential new approach for treatment of ADPKD, a disorder for which no effective treatment currently exists.

Diffusion tensor imaging of the kidney in healthy controls and in children and young adults with autosomal recessive polycystic kidney disease

OBJECTIVE

To compare diffusion tensor imaging (DTI) of the kidneys and its derived parameters in children with autosomal recessive polycystic kidney disease (ARPKD) versus healthy controls.

METHODS

In a prospective IRB-approved study, we evaluated the use of DTI to compare kidney parenchyma FA values in healthy controls (age-matched children with no history of renal disease) versus patients with ARPKD. A 20-direction DTI with b-values of b = 0 s/mm² and b = 400 s/mm² was used to acquire data in coronal direction using a fat-suppressed spin-echo echo-planar sequence. Diffusion Toolkit and TrackVis were used for analysis and segmentation. TrackVis was used to draw regions of interest (ROIs) covering the entire volume of the renal parenchyma, excluding the collecting system. Fibers were reconstructed using a deterministic fiber tracking algorithm. The FA values based on the ROI data, mean length, and volume of the tracks based on the fiber tracking data were recorded.

RESULTS

Eight healthy controls (mean age = 12.9 years ± 4.0; 1/8 males) and six ARPKD participants (mean age = 13.8 years ± 8.5; 5/6 males) were included in the study. Compared to healthy controls, patients with ARPKD had significantly lower FA values (0.33 ± 0.03 vs. 0.25 ± 0.02, p = 0.002) and mean track length (16.73 ± 3.43 vs. 11.61 ± 1.29 mm, p = 0.005).

CONCLUSION

DTI of the kidneys shows significantly lower FA values and mean track length in children and young adults with ARPKD compared to normal subjects. DTI of the kidney offers a novel approach for characterizing renal disease based on changes in diffusion anisotropy and kidney structure.

Management of autosomal-dominant polycystic kidney disease-state-of-the-art

Autosomal-dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of end-stage renal disease in adults. Affected individuals and families face a significant medical and psychosocial burden due to both renal and extrarenal manifestations. Consequently, interventions that ameliorate the course of the disease and specifically slow down the loss of kidney function are of special interest. Major research efforts in both the clinical and pre-clinical setting in the last two decades resulted in a number of pivotal clinical trials aimed to ameliorate the disease. These studies have underlined the important role of specific supportive measures and provided the basis for first targeted pharmacological therapies. Very recently, the concept of repurposing drugs approved for other conditions for a use in ADPKD has gained increasing attention. Here, we review the current best-practice management of ADPKD patients with a focus on interventions that have reached clinical use to maintain kidney function and give an outlook on future trials and potential novel treatment strategies.

Effect of Lanreotide on Kidney Function in Patients With Autosomal Dominant Polycystic Kidney Disease: The DIPAK 1 Randomized Clinical Trial

Importance

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation in both kidneys and loss of renal function, eventually leading to a need for kidney replacement therapy. There are limited therapeutic management options.

Objective

To examine the effect of the somatostatin analogue lanreotide on the rate of kidney function loss in patients with later-stage ADPKD.

Design, Setting, and Participants

An open-label randomized clinical trial with blinded end point assessment that included 309 patients with ADPKD from July 2012 to March 2015 at 4 nephrology outpatient clinics in the Netherlands. Eligible patients were 18 to 60 years of age and had an estimated glomerular filtration rate (eGFR) of 30 to 60 mL/min/1.73 m2. Follow-up of the 2.5-year trial ended in August 2017.

Interventions

Patients were randomized to receive either lanreotide (120 mg subcutaneously once every 4 weeks) in addition to standard care (n = 153) or standard care only (target blood pressure <140/90 mm Hg; n = 152).

Main Outcomes and Measures

Primary outcome was annual change in eGFR assessed as slope through eGFR values during the 2.5-year treatment phase. Secondary outcomes included change in eGFR before vs after treatment, incidence of worsening kidney function (start of dialysis or 30% decrease in eGFR), change in total kidney volume and change in quality of life (range: 1 [not bothered] to 5 [extremely bothered]).

Results

Among the 309 patients who were randomized (mean [SD] age, 48.4 [7.3] years; 53.4% women), 261 (85.6%) completed the trial. Annual rate of eGFR decline for the lanreotide vs the control group was -3.53 vs -3.46 mL/min/1.73 m2 per year (difference, -0.08 [95% CI, -0.71 to 0.56]; P = .81). There were no significant differences for incidence of worsening kidney function (hazard ratio, 0.87 [95% CI, 0.49 to 1.52]; P = .87), change in eGFR (-3.58 vs -3.45; difference, -0.13 mL/min/1.73 m2 per year [95% CI, -1.76 to 1.50]; P = .88), and change in quality of life (0.05 vs 0.07; difference, -0.03 units per year [95% CI, -0.13 to 0.08]; P = .67). The rate of growth in total kidney volume was lower in the lanreotide group than the control group (4.15% vs 5.56%; difference, -1.33% per year [95% CI, -2.41% to -0.24%]; P = .02). Adverse events in the lanreotide vs control group included injection site discomfort (32% vs 0.7%), injection site papule (5.9% vs 0%), loose stools (91% vs 6.6%), abdominal discomfort (79% vs 20%), and hepatic cyst infections (5.2% vs 0%).

Conclusions and Relevance

Among patients with later-stage autosomal dominant polycystic kidney disease, treatment with lanreotide compared with standard care did not slow the decline in kidney function over 2.5 years of follow-up. These findings do not support the use of lanreotide for treatment of later-stage autosomal dominant polycystic kidney disease.

Trial Registration

ClinicalTrials.gov Identifier: NCT01616927.

The expression of somatostatin receptor 2 decreases during cyst growth in mice with polycystic kidney disease

IMPACT STATEMENT

Somatostatin (SST) analogs have been shown to halt cyst growth and progression of autosomal dominant polycystic kidney disease by several clinical trials. However, two studies suggest that the effect of the SST analog octreotide on kidney growth during the first year of treatment is reduced in the subsequent follow-ups and the kidney enlargement resumes. This biphasic change in kidney growth during octreotide treatment may be partially explained by alterations in SSTR2 expression. Here, we found that SSTR2 is mainly expressed in distal tubules and collecting ducts in murine kidneys, and the expression of SSTR2 decreases during cyst growth in two PKD mouse models. Our data may thus provide possible explanations for the lack of efficacy in long-term treatment with SST analogs.

Engineered Kidney Tubules for Modeling Patient-Specific Diseases and Drug Discovery

The lack of engineering systems able to faithfully reproduce complex kidney structures in vitro has made it difficult to efficiently model kidney diseases and development. Using polydimethylsiloxane (PDMS) scaffolds and a kidney-derived cell line we developed a system to rapidly engineer custom-made 3D tubules with typical renal epithelial properties. This system was successfully employed to engineer patient-specific tubules, to model polycystic kidney disease (PKD) and test drug efficacy, and to identify a potential new pharmacological treatment. By optimizing our system we constructed functional ureteric bud (UB)-like tubules from human induced pluripotent stem cells (iPSCs), and identified a combination of growth factors that induces budding morphogenesis like embryonic kidneys do. Finally, we applied this assay to investigate budding defects in UB-like tubules derived from a patient with a PAX2 mutation. Our system enables the modeling of human kidney disease and development, drug testing and discovery, and lays the groundwork for engineering anatomically correct kidney tissues in vitro and developing personalized medicine applications.

Quantitative magnetic resonance imaging assessments of autosomal recessive polycystic kidney disease progression and response to therapy in an animal model

BackgroundAutosomal recessive polycystic kidney disease (ARPKD) is associated with significant mortality and morbidity, and currently, there are no disease-specific treatments available for ARPKD patients. One major limitation in establishing new therapies for ARPKD is a lack of sensitive measures of kidney disease progression. Magnetic resonance imaging (MRI) can provide multiple quantitative assessments of the disease.MethodsWe applied quantitative image analysis of high-resolution (noncontrast) T2-weighted MRI techniques to study cystic kidney disease progression and response to therapy in the PCK rat model of ARPKD.ResultsSerial imaging over a 2-month period demonstrated that renal cystic burden (RCB, %)=[total cyst volume (TCV)/total kidney volume (TKV) × 100], TCV, and, to a lesser extent, TKV detected cystic kidney disease progression, as well as the therapeutic effect of octreotide, a clinically available medication shown previously to slow both kidney and liver disease progression in this model. All three MRI measures correlated significantly with histologic measures of renal cystic area, although the correlation of RCB and TCV was stronger than that of TKV.ConclusionThese preclinical MRI results provide a basis for applying these quantitative MRI techniques in clinical studies, to stage and measure progression in human ARPKD kidney disease.

Therapeutic Targets in Polycystic Liver Disease

Polycystic liver diseases (PLD) are a group of genetic disorders initiated by mutations in several PLD-related genes and characterized by the presence of multiple cholangiocyte-derived hepatic cysts that progressively replace liver tissue. PLD co-exists with Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Autosomal Recessive PKD as well as occurs alone (i.e., Autosomal Dominant Polycystic Liver Disease [ADPLD]). PLD associated with ADPKD and ARPKD belong to a group of disorders known as cholangiociliopathies since many disease-causative and disease-related proteins are expressed in primary cilia of cholangiocytes. Aberrant expression of these proteins in primary cilia affects their structures and functions promoting cystogenesis. Current medical therapies for PLD include symptomatic management and surgical interventions. To date, the only available drug treatment for PLD patients that halt disease progression and improve quality of life are somatostatin analogs. However, the modest clinical benefits, need for long-term maintenance therapy, and the high cost of treatment justify the necessity for more effective treatment options. Substantial evidence suggests that experimental manipulations with components of the signaling pathways that influence cyst development (e.g., cAMP, intracellular calcium, receptor tyrosine kinase, transient receptor potential cation channel subfamily V member 4 (TRPV4) channel, mechanistic target of rapamycin (mTOR), histone deacetylase (HDAC6), Cdc25A phosphatase, miRNAs and metalloproteinases) attenuate growth of hepatic cysts. Many of these targets have been evaluated in pre-clinical trials suggesting their value as potential new therapies. This review outlines the current clinical and preclinical treatment strategies for PLD.

Canonical Wnt inhibitors ameliorate cystogenesis in a mouse ortholog of human ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) can be caused by mutations in the PKD1 or PKD2 genes. The PKD1 gene product is a Wnt cell-surface receptor. We previously showed that a lack of the PKD2 gene product, PC2, increases β-catenin signaling in mouse embryonic fibroblasts, kidney renal epithelia, and isolated renal collecting duct cells. However, it remains unclear whether β-catenin signaling plays a role in polycystic kidney disease phenotypes or if a Wnt inhibitor can halt cyst formation in ADPKD disease models. Here, using genetic and pharmacologic approaches, we demonstrated that the elevated β-catenin signaling caused by PC2 deficiency contributes significantly to disease phenotypes in a mouse ortholog of human ADPKD. Pharmacologically inhibiting β-catenin stability or the production of mature Wnt protein, or genetically reducing the expression of Ctnnb1 (which encodes β-catenin), suppressed the formation of renal cysts, improved renal function, and extended survival in ADPKD mice. Our study clearly demonstrates the importance of β-catenin signaling in disease phenotypes associated with Pkd2 mutation. It also describes the effects of two Wnt inhibitors, XAV939 and LGK974, on various Wnt signaling targets as a potential therapeutic modality for ADPKD, for which there is currently no effective therapy.

Cholangiocyte autophagy contributes to hepatic cystogenesis in polycystic liver disease and represents a potential therapeutic target

Polycystic liver disease (PLD) is a group of genetic disorders with limited treatment options and significant morbidity. Hepatic cysts arise from cholangiocytes exhibiting a hyperproliferative phenotype. Considering that hyperproliferation of many cell types is associated with alterations in autophagy, we hypothesized that autophagy is altered in PLD cholangiocytes, contributes to hepatic cystogenesis, and might represent a potential therapeutic target. We employed functional pathway cluster analysis and next-generation sequencing, transmission electron microscopy, immunofluorescence confocal microscopy, and western blotting to assess autophagy in human and rodent PLD cholangiocytes. A three-dimensional culture model was used to study the effects of molecular and pharmacologic inhibition of autophagy on hepatic cystogenesis in vitro, and the polycystic kidney disease-specific rat, an animal model of PLD, to study the effects of hydroxychloroquine, a drug that interferes with the autophagy pathway, on disease progression in vivo. Assessment of the transcriptome of PLD cholangiocytes followed by functional pathway cluster analysis revealed that the autophagy-lysosomal pathway is one of the most altered pathways in PLD. Direct evaluation of autophagy in PLD cholangiocytes both in vitro and in vivo showed increased number and size of autophagosomes, lysosomes, and autolysosomes; overexpression of autophagy-related proteins (Atg5, Beclin1, Atg7, and LC3); and enhanced autophagic flux associated with activation of the cAMP-protein kinase A-cAMP response element-binding protein signaling pathway. Molecular and pharmacologic intervention in autophagy with ATG7 small interfering RNA, bafilomycin A₁ , and hydroxychloroquine reduced proliferation of PLD cholangiocytes in vitro and growth of hepatic cysts in three-dimensional cultures. Hydroxychloroquine also efficiently inhibited hepatic cystogenesis in the polycystic kidney disease-specific rat.

CONCLUSION

Autophagy is increased in PLD cholangiocytes, contributes to hepatic cystogenesis, and represents a potential therapeutic target for disease treatment. (Hepatology 2018;67:1088-1108).

Expanding the role of vasopressin antagonism in polycystic kidney diseases: From adults to children?

Polycystic kidney disease (PKD) encompasses a group of genetic disorders that are common causes of renal failure. The two classic forms of PKD are autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD). Despite their clinical differences, ARPKD and ADPKD share many similarities. Altered intracellular Ca²⁺ and increased cyclic adenosine monophosphate (cAMP) concentrations have repetitively been described as central anomalies that may alter signaling pathways leading to cyst formation. The vasopressin V2 receptor (V2R) antagonist tolvaptan lowers cAMP in cystic tissues and slows renal cystic progression and kidney function decline when given over 3 years in adult ADPKD patients. Tolvaptan is currently approved for the treatment of rapidly progressive disease in adult ADPKD patients. On the occasion of the recent initiation of a clinical trial with tolvaptan in pediatric ADPKD patients, we aim to describe the most important aspects in the literature regarding the AVP-cAMP axis and the clinical use of tolvaptan in PKD.

Combination of a Histone Deacetylase 6 Inhibitor and a Somatostatin Receptor Agonist Synergistically Reduces Hepatorenal Cystogenesis in an Animal Model of Polycystic Liver Disease

Hepatic cystogenesis in polycystic liver disease (PLD) is associated with abnormalities in multiple cellular processes, including elevated cAMP and overexpression of histone deacetylase 6 (HDAC6). Disease progression in polycystic kidney (PCK) rats (an animal model of PLD) is attenuated by inhibition of either cAMP production or HDAC6. Therefore, we hypothesized that concurrent targeting of HDAC6 and cAMP would synergistically reduce cyst growth. Changes in hepatorenal cystogenesis were examined in PCK rats treated with a pan-HDAC inhibitor, panobinostat; three specific HDAC6 inhibitors, ACY-1215, ACY-738, and ACY-241; and a combination of ACY-1215 and the somatostatin receptor analogue, pasireotide. We also assessed effects of ACY-1215 and pasireotide alone and in combination on cell proliferation, cAMP production, and expression of acetylated α-tubulin in vitro in cultured cholangiocytes and the length of primary cilia and the frequency of ciliated cholangiocytes in vivo in PCK rats. Panobinostat and all three HDAC6 inhibitors decreased hepatorenal cystogenesis in PCK rats. ACY-1215 was more effective than other HDAC inhibitors and was chosen for combinational treatment. ACY-1215 + pasireotide combination synergistically reduced cyst growth and increased length of primary cilia in PCK rats. In cultured cystic cholangiocytes, ACY-1215 + pasireotide combination concurrently decreased cell proliferation and inhibited cAMP levels. These data suggest that the combination of drugs that inhibit HDAC6 and cAMP may be an effective therapy for PLD.

Pasireotide does not improve efficacy of aspiration sclerotherapy in patients with large hepatic cysts, a randomized controlled trial

OBJECTIVES

We tested whether complementary use of the somatostatin analogue pasireotide would augment efficacy of aspiration sclerotherapy of hepatic cysts.

METHODS

We conducted a double-blind, placebo-controlled trial in patients who underwent aspiration sclerotherapy of a large (>5 cm) symptomatic hepatic cyst. Patients were randomized to either intramuscular injections of pasireotide 60 mg long-acting release (n = 17) or placebo (sodium chloride 0.9 %, n = 17). Injections were administered 2 weeks before and 2 weeks after aspiration sclerotherapy. The primary endpoint was proportional cyst diameter reduction (%) from baseline to 6 weeks. Secondary outcomes included long-term cyst reduction at 26 weeks, patient-reported outcomes including the polycystic liver disease-questionnaire (PLD-Q) and safety.

RESULTS

Thirty-four patients (32 females; 53.6 ± 7.8 years) were randomized between pasireotide or placebo. Pasireotide did not improve efficacy of aspiration sclerotherapy at 6 weeks compared to controls (23.6 % [IQR 12.6-30.0] vs. 21.8 % [9.6-31.8]; p = 0.96). Long-term cyst diameter reduction was similar in both groups (49.1 % [27.0-73.6] and 45.6 % [29.6-59.6]; p = 0.90). Mean PLD-Q scores improved significantly in both groups (p < 0.01) without differences between arms (p = 0.92).

CONCLUSIONS

In patients with large symptomatic hepatic cysts, complementary pasireotide to aspiration sclerotherapy did not improve cyst reduction or clinical response.

KEY POINTS

• Complementary pasireotide treatment does not improve efficacy of aspiration sclerotherapy. • Cyst fluid reaccumulation after aspiration sclerotherapy is a transient phenomenon. • Aspiration sclerotherapy strongly reduces symptoms and normalizes quality of life.

Development and characterization of cholangioids from normal and diseased human cholangiocytes as an in vitro model to study primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an incurable, fibroinflammatory biliary disease for which there is no effective pharmacotherapy. We recently reported cholangiocyte senescence as an important phenotype in PSC while others showed that portal macrophages accumulate in PSC. Unfortunately, our ability to explore cholangiocyte senescence and macrophage accumulation has been hampered by limited in vitro models. Thus, our aim was to develop and characterize a three-dimensional (3D) model of normal and diseased bile ducts (cholangioids) starting with normal human cholangiocytes (NHC), senescent NHC (NHC-sen), and cholangiocytes from PSC patients. In 3D culture, NHCs formed spheroids of ~5000 cells with a central lumen of ~150 μm. By confocal microscopy and western blot, cholangioids retained expression of cholangiocyte proteins (cytokeratin 7/19) and markers of epithelial polarity (secretin receptor and GM130). Cholangioids are functionally active, and upon secretin stimulation, luminal size increased by ~80%. Cholangioids exposed to hydrogen peroxide exhibited cellular senescence and the senescence-associated secretory phenotype (SASP; increased IL-6, p21, SA-β-Gal, yH2A.x and p16 expression). Furthermore, cholangioids derived from NHC-sen or PSC patients were smaller and had slower growth than the controls. When co-cultured with THP-1 macrophages, the number of macrophages associated with NHC-sen or PSC cholangioids was five- to seven-fold greater compared to co-culture with non-senescent NHC. We observed that NHC-sen and PSC cholangioids release greater number of extracellular vesicles (EVs) compared to controls. Moreover, conditioned media from NHC-sen cholangioids resulted in an ~2-fold increase in macrophage migration. In summary, we developed a method to generate normal and diseased cholangioids, characterized them morphologically and functionally, showed that they can be induced to senescence and SASP, and demonstrated both EV release and macrophage attraction. This novel model mimics several features of PSC, and thus will be useful for studying the pathogenesis of PSC and potentially identifying new therapeutic targets.