Polycystic kidney disease

Autosomal dominant polycystic kidney disease: an overview of recent genetic and clinical advances

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inherited kidney disease, characterized by the progressive development of multiple kidney cysts, leading to a gradual decline in kidney function. ADPKD is also the fourth leading cause of kidney failure (KF) in adults. In addition to kidney manifestations, ADPKD is associated with various extrarenal features, including liver cysts, cardiovascular abnormalities, intracranial aneurysms, and chronic pain with significant impact on patients' quality of life. While several disease-modifying agents have been tested in ADPKD, tolvaptan remains the only approved drug by the US Food and Drug Administration. The Mayo Imaging Classification is currently the most practical tool for predicting rate of kidney disease progression in ADPKD. This review provides a comprehensive overview of ADPKD, focusing on its genetics, pathophysiology, clinical presentation, management, and prognostic tools. Advances in diagnostic imaging and genetic testing have improved the early detection of ADPKD, allowing better classification of patients and prediction of KF. The review also discusses current therapeutic approaches to ADPKD, including tolvaptan, a vasopressin V2-receptor antagonist. Additionally, we address specific issues in children and pregnant individuals with ADPKD. Despite substantial progress in understanding ADPKD, there is a large need for additional effective treatments and prognostic markers to provide a more personalized care for these patients.

Therapeutic opportunities in polycystic kidney and liver disease through extracellular matrix dynamics

Autosomal Dominant and Autosomal Recessive Polycystic Kidney Disease (ADPKD and ARPKD) are, respectively, common and rare forms of polycystic disorders, characterized by the formation and progressive growth of cysts from tubules in the kidneys and bile ducts in the liver. Alterations in the extracellular matrix (ECM) and in the activity of matrix metalloproteases (MMPs), both associated with fibrosis, have been shown to be important factors in cystic growth and progression of these diseases. We used tandem mass spectrometry (LC-MS/MS) to identify the most enriched proteins and pathways in an orthologous rapidly progressive mouse model of ADPKD: Pkd1flox/floxTamCre. This information was used to discover and validate novel therapeutic targets in orthologous models of ADPKD (Pkd1flox/floxTamCre) and ARPKD (Pkdh1del3-4/del3-4). ECM related pathways and expression levels of MMPs were among the most dysregulated cellular processes in polycystic kidney and liver. Selective inhibition of MMPs by marimastat (MTT) altered the ECM response and resulted in inhibition of collecting duct-derived cyst growth, delay of global kidney cyst progression and rescue of liver phenotype by normalized MMPs expression and significant reduction in fibrosis. This phenotypic improvement was further enhanced by treatment of MTT and tolvaptan, indicating an additive benefit to targeting the fibrotic and growth pathways in cysts. As conclusion, targeting of MMPs are important in ECM dysregulation and offers a new potential therapeutic strategy for both kidney and bile duct derived fibrocystic disease in ADPKD and ARPKD. Such approaches can have additive benefits with other treatment approaches, such as tolvaptan.

Metabolic reprogramming in polycystic kidney disease and other renal ciliopathies

Primary cilia are solitary organelles formed by a microtubule-based skeleton protruding in a single copy on the surface of most cells. Alterations in their function cause a plethora of human conditions collectively called the ciliopathies. The kidney is frequently and severely affected in the ciliopathies, presenting with a spectrum of phenotypes. Cyst formation is a common trait of all renal ciliopathies. Besides this common manifestation, however, the renal ciliopathies present with profoundly different phenotypes, resulting in either polycystic kidney disease (PKD) or nephronophthisis (NPH) phenotypes. The past decade has seen a surge of studies highlighting metabolic reprogramming as a major feature of PKD, with a distinct involvement of mitochondrial dysfunction. This discovery has brought forward the development of novel therapeutic approaches. More recent evidence suggests that primary cilia modulate the mitochondrial production of energy in response to environmental cues. Here, we summarize the evidence available to date and propose a more general involvement of metabolic and mitochondrial alterations in the renal ciliopathies that might in principle help defining the profoundly different, and potentially opposite, manifestations observed.

Polycystins recruit cargo to distinct ciliary extracellular vesicle subtypes in C. elegans

Therapeutic use of tiny extracellular vesicles (EVs) requires understanding cargo loading mechanisms. Here, we use a modular proximity labeling approach to identify the cargo of ciliary EVs associated with the transient receptor potential channel polycystin-2 PKD-2 of C. elegans. Polycystins are conserved ciliary proteins and cargo of EVs; dysfunction causes polycystic kidney disease in humans and mating deficits in C. elegans. We discover that polycystins localize with specific cargo on ciliary EVs: polycystin-associated channel-like protein PACL-1, dorsal and ventral polycystin-associated membrane C-type lectins PAMLs, and conserved tumor necrosis factor receptor-associated factor (TRAF) TRF-1 and TRF-2. Loading of these components to EVs relies on polycystin-1 LOV-1. Our modular EV-TurboID approach can be applied in both cell- and tissue-specific manners to define the composition of distinct EV subtypes, addressing a major challenge of the EV field.

Establishing Meaningful Patient-Centered Outcomes with Relevance for Patients with Polycystic Kidney Disease: Patient, Caregiver, and Researcher Priorities for Research in Polycystic Kidney Disease

Key Points

Background

Patient involvement in research can help to ensure that the evidence generated aligns with their needs and priorities. In the Establishing Meaningful Patient-Centered Outcomes with Relevance for Patients with Polycystic Kidney Disease (PKD) project, we aimed to identify patient-important outcomes and discuss the effect of PKD on patients.

Methods

Nine focus groups were held with adult patients with PKD, caregivers, and clinical or research experts in PKD. We used a nominal, multivote technique to rank patient-important outcomes to be prioritized by future PKD research. We conducted a thematic analysis of verbatim transcriptions to identify themes regarding the effect of PKD on their daily lives. Other focus group topics included insurability and patient engagement.

Results

Ninety patients and/or caregivers and eight clinicians and/or researchers participated in the focus groups. Nine focus groups yielded 35 outcomes important to patients that were grouped into six categories, ranked in order of importance: kidney health, comorbidities, lifestyle, psychological effect, family and awareness, and mortality. Regarding the effect of PKD on the patient's daily lives, we identified five themes, listed in order of importance: psychological effect, effect on daily living, issues affecting decision making, health care-related issues, and PKD-specific testing dilemmas.

Conclusions

This study of stakeholder engagement in patients with PKD revealed important priorities and values that should be considered for future research and when caring for patients with PKD. Future research should focus on kidney health and managing comorbidities in patients with PKD. This will help to bridge the knowledge gap and develop meaningful comparative effectiveness research in PKD.

Longitudinal assessment of measured and estimated glomerular filtration-rate in autosomal dominant polycystic kidney disease: Real practice experience

BACKGROUND

Equations for estimation glomerular filtration rate (eGFR) have been associated with poor clinical performance and their clinical accuracy and reliability have been called into question.

AIM

To assess the longitudinal changes in measured glomerular filtration rate (mGFR) in patients with autosomal dominant polycystic kidney disease (ADPKD).

METHODS

Analysis of an ambispective data base conducted on consecutive patients diagnosed with ADPKD. The mGFR was assessed by iohexol clearance; while eGFR was calculated by three different formulas: (1) The chronic kidney disease epidemiology collaboration (CKD-EPI); (2) Modification of diet in renal disease (MDRD); and (3) The 24-hour urine creatinine clearance (CrCl). The primary end-points were the mean change in mGFR between the baseline and final visit, as well as the comparison of the mean change in mGFR with the change estimated by the different formulas.

RESULTS

Thirty-seven patients were included in the study. As compared to baseline, month-6 mGFR was significantly decrease by -4.4 mL/minute ± 10.3 mL/minute (P = 0.0132). However, the CKD-EPI, MDRD, and CrCl formulas underestimated this change by 48.3%, 89.0%, and 45.8% respectively, though none of these differences reached statistical significance (P = 0.3647; P = 0.0505; and P = 0.736, respectively). The discrepancies between measured and estimated glomerular filtration rate values, as evaluated by CKD-EPI (r = 0.29, P = 0.086); MDRD (r = 0.19, P = 0.272); and CrCl (r = 0.09, P = 0.683), were not correlated with baseline mGFR values.

CONCLUSION

This study indicated that eGFR inaccurately reflects the decline in mGFR and cannot reliably track changes over time. This poses significant challenges for clinical decision-making, particularly in treatment strategies.

Lysine crotonylation in disease: mechanisms, biological functions and therapeutic targets

Lysine crotonylation (Kcr), a previously unknown post-translational modification (PTM), plays crucial roles in regulating cellular processes, including gene expression, chromatin remodeling, and cellular metabolism. Kcr is associated with various diseases, including neurodegenerative disorders, cancer, cardiovascular conditions, and metabolic syndromes. Despite advances in identifying crotonylation sites and their regulatory enzymes, the molecular mechanisms by which Kcr influences disease progression remain poorly understood. Understanding the interplay between Kcr and other acylation modifications may reveal opportunities for developing targeted therapies. This review synthesizes current research on Kcr, focusing on its regulatory mechanisms and disease associations, and highlights insights into future exploration in epigenetics and therapeutic interventions.

Ciliary Ion Channels in Polycystic Kidney Disease

Polycystic kidney disease (PKD) is the most common hereditary disorder that disrupts renal function and frequently progresses to end-stage renal disease. Recent advances have elucidated the critical role of primary cilia and ciliary ion channels, including transient receptor potential (TRP) channels, cystic fibrosis transmembrane conductance regulator (CFTR), and polycystin channels, in the pathogenesis of PKD. While some channels primarily function as chloride conductance channels (e.g., CFTR), others primarily regulate calcium (Ca+2) homeostasis. These ion channels are essential for cellular signaling and maintaining the normal kidney architecture. Dysregulation of these pathways due to genetic mutations in PKD1 and PKD2 leads to disrupted Ca+2 and cAMP signaling, aberrant fluid secretion, and uncontrolled cellular proliferation, resulting in tubular cystogenesis. Understanding the molecular mechanisms underlying these dysfunctions has opened the door for innovative therapeutic strategies, including TRPV4 activators, CFTR inhibitors, and calcimimetics, to mitigate cyst growth and preserve renal function. This review summarizes the current knowledge on the roles of ciliary ion channels in PKD pathophysiology, highlights therapeutic interventions targeting these channels, and identifies future research directions for improving patient outcomes.

Polycystic Kidney Disease in Children: The Current Status and the Next Horizon

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are inherited disorders that share many features such as kidney cysts, hypertension, urinary concentrating defects, and progressive chronic kidney disease. Underlying pathogenic mechanisms for both include cilia dysfunction and dysregulated intracellular signaling. ADPKD has been traditionally regarded as an adult-onset disease, whereas ARPKD has been classically described as an infantile or childhood condition. However, clinicians must recognize that both disorders can present across all age groups ranging from fetal life and infancy to childhood and adolescence, as well as adulthood. Here we highlight the points of overlap and distinct features for these disorders with respect to pathogenesis, diagnostic modalities (radiological and genetic), clinical assessment, and early therapeutic management. In particular, we consider key issues at two critical points for transition of care, i.e., fetal life to infancy and adolescence to adulthood. These timepoints are poorly covered in the extant literature. Therefore, we recommend guiding principles for transitions of clinical care at these critical junctures in the lifespan. While there is no cure for polycystic kidney disease (PKD), recent insights into pathogenic mechanisms have identified promising therapeutic targets that are currently being evaluated in a growing portfolio of clinical trials. We summarize the key findings from these largely adult-based trials and discuss the implications for designing child-focused studies. Finally, we look forward to the next horizon for childhood PKD, highlighting gaps in our current knowledge, and discussing future directions and strategies to attenuate the full burden of disease for children affected with PKD.

Renal ciliopathies

Primary cilia are essential cellular organelles with pivotal roles in many signalling pathways. Here we provide an overview of the role of primary cilia within the kidney, starting with primary ciliary structure and key protein complexes. We then highlight the specialised functions of primary cilia, emphasising their role in a group of diseases known as renal ciliopathies. These conditions include forms of polycystic kidney disease, nephronophthisis, and other syndromic ciliopathies, such as Joubert syndrome and Bardet-Biedl syndrome. We explore models of renal ciliopathies, both in vitro and in vivo, shedding light on the molecular mechanisms underlying these diseases including Wnt and Hedgehog signalling pathways, inflammation, and cellular metabolism. Finally, we discuss therapeutic approaches, from current treatments to cutting-edge preclinical research and clinical trials.

Design of Selective BRD4 Inhibitors for the Treatment of Autosomal Dominant Polycystic Kidney Disease

Epigenetic modulation plays a pivotal role in restraining tumor progression by governing gene expression and protein function. Autosomal dominant polycystic kidney disease (ADPKD), characterized by neoplastic-like progression, can be managed by inhibiting cyst expansion. Of note, the epigenetic regulator BRD4 has been implicated in ADPKD's development. Our prior research unveiled a class of (pyrazol-3-yl) pyrimidin-4-amine compounds as potent BRD4 inhibitors with additional kinase inhibition, which might induce unwanted biological activities. To address this, this study focused on creating selective BRD4 inhibitors through structure-guided design, minimizing off-target kinase interactions. Specifically, compound 23 emerged as an efficacious and selective BRD4 inhibitor in cellular and embryonic kidney models of ADPKD, along with encouraging outcomes in murine models. Collectively, these results highlight the therapeutic potential of targeted BRD4 inhibition as a safe and efficacious strategy for managing ADPKD.

BICC1 Interacts with PKD1 and PKD2 to Drive Cystogenesis in ADPKD

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

Bilateral Polycystic Kidney Disease and Inferior Vena Cava (IVC) Thrombosis: A Cadaveric Study

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease and one of the most common causes of end-stage kidney disease. The occurrence of bilateral polycystic kidney disease with liver cysts is uncommon. A case of bilateral polycystic kidney disease, found to have liver cysts and inferior vena cava thrombosis in a cadaveric study, is presented in this study. Dissection was performed on a 90-year-old Caucasian male cadaver. Both kidneys were enlarged and contained multiple cysts with normal renal tissue interposed. When comparing the two kidneys, the cysts on the left were notably larger. There was a partial absence of renal capsules. Additionally, a polycystic liver and an inferior vena cava filter were found during the dissection. The patient's history of venous thrombosis is indicated by the previously inserted inferior vena cava filter.

A Rare Coexisting Presentation of Autosomal Dominant Polycystic Kidney Disease With Rapid Deterioration of Renal Function and Neurofibromatosis Type 1

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common hereditary kidney disorders, characterized by progressive cyst development. Neurofibromatosis type 1 (NF1) is another autosomal dominant disorder, characterized by café-au-lait spots, neurofibromas, and multisystem involvement. We report the case of an 18-year-old male with ADPKD and NF1, referred due to progressively worsening renal dysfunction. His initial estimated glomerular filtration rate (eGFR) was 71.9 mL/min/1.73m², with MRI showing bilateral cystic renal enlargement (total kidney volume: 758 mL). One year later, his eGFR declined to 56.7 mL/min/1.73m², and kidney volume increased by 10.4% over one year. Tolvaptan was initiated, and he remains under follow-up. Mutations in the PKD1/PKD2, which are responsible for ADPKD, affect intracellular signaling, including the mammalian target of the rapamycin (mTOR) pathway, leading to cyst formation and progression, while NF1 mutations overactivate the Ras proteins. His disease progression was more severe than that of his father with ADPKD alone, suggesting NF1 may have accelerated cyst enlargement. The co-occurrence of ADPKD and NF1 is extremely rare, with only a few cases reported in the past.

A Challenging Case of Inferior Vena Cava Compression in an Adult Polycystic Kidney Disease Patient. A Case Report

Adult polycystic kidney disease (ADPKD) is a multi-system genetic disorder characterized by the development and progressive enlargement of fluid-filled cysts in both kidneys, along with other organs. As one of the main causes of kidney failure, ADPKD can progress to end-stage renal disease (ESRD), with over 50% of affected individuals progressing to ESRD by age 50. The symptoms in ADPKD are variable, with some patients experiencing nonspecific signs, while others present with symptoms related to the mass effect of enlarged kidneys on surrounding structures. This case report highlights an unusual presentation of ADPKD in a patient who developed symptoms of inferior vena cava (IVC) compression. Remarkably, these symptoms improved after bilateral nephrectomies, suggesting that bilateral nephrectomy would provide help in these situations.

The primary cilia: Orchestrating cranial neural crest cell development

Primary cilia (hereafter "cilia") are microtubule-based antenna-like organelles projecting from the surface of vertebrate cells. Cilia can serve as cellular antennae controlling cell growth and differentiation. Absent or dysfunctional cilia frequently lead to craniofacial anomalies known as craniofacial ciliopathies. However, the detailed pathological mechanisms of craniofacial ciliopathies remain unclear. This perspective discusses our current understanding of the role of cilia in cranial neural crest cells. We also describe potential mechanisms of ciliogenesis in cranial neural crest cells, which may contribute to unraveling the complex pathogenesis of craniofacial ciliopathies.

A miRNA-Based Approach in Autosomal Dominant Polycystic Kidney Disease: Challenges and Insights from Adult to Pediatric Evidence

Autosomal dominant polycystic kidney disease (ADPKD) represents the most common inherited kidney disorder leading to kidney failure in a significant percentage of patients over time. Although previously considered as an adult disease, robust evidence demonstrated that clinical manifestations might occur during childhood and adolescence. Therefore, early identification and treatment of the disease are of cardinal importance for pediatricians to ensure the best long-term outcomes. To date, licensed treatment options are limited but promising potential therapeutic targets are emerging. Among these, an intriguing pathophysiological role for microRNAs as small molecules with a critical role in regulating gene expression has been considered possible in ADPKD. Indeed, numerous circulating microRNAs have been found to be dysregulated in ADPKD, suggesting their potential role as biomarkers and therapeutic targets. Based on this background, further detailed insights into the mechanisms of miRNAs contributing to ADPKD development might pave the way for their effective application as a targeted treatment in young patients with ADPKD. We aimed to summarize the most recent evidence in this fascinating research area, providing a comprehensive overview of the current landscape of specific microRNAs in ADPKD as a potential innovative therapeutic strategy for these young patients.

Matching clinical and genetic data in pediatric patients at risk of developing cystic kidney disease

BACKGROUND

Cystic kidney disease is a heterogeneous group of hereditary and non-hereditary pathologic conditions, associated with the development of renal cysts. These conditions may be present both in children and adults. Cysts can even be observed already during the prenatal age, and pediatric patients with cysts need to be clinically monitored. An early clinical and genetic diagnosis is therefore mandatory for optimal patient management. The aim of this study was to perform genetic analyses in patients with echographic evidence of kidney cysts to provide an early molecular diagnosis.

METHODS

A cohort of 70 pediatric patients was enrolled and clinically studied at the time of first recruitment and at follow-up. Genetic testing by clinical exome sequencing was performed and a panel of genes responsible for "cystic kidneys" was analyzed to identify causative variants. Sanger validation and segregation studies were exploited for the final classification of the variants and accurate genetic counseling.

RESULTS

Data showed that 53/70 of pediatric patients referred with a clinical suspicion of cystic kidney disease presented a causative genetic variant. In a significant proportion of the cohort (24/70), evidence of hyper-echogenic/cystic kidneys was already present in the prenatal period, even in the absence of a positive family history.

CONCLUSIONS

This study suggests that cystic kidney disease may develop since the very early stages of life and that screening programs based on ultrasound scans and genetic testing play a critical role in diagnosis, allowing for better clinical management and tailored genetic counseling to the family.

Optical Genome Mapping (OGM) Identifies Multiple Structural Variants in a Case With Atypical Phelan-McDermid Syndrome

Here we describe a neonate exhibiting hypotonia, macrocephaly, renal cysts, and respiratory failure requiring tracheostomy and ventilator support. Genetic analysis via rapid genome sequencing (rGS) identified a loss on chromosome 4 encompassing polycystin-2 (PKD2) and a loss on chromosome 22 encompassing SH3 and Multiple Ankyrin Repeat Domains 3 (SHANK3), indicative of Phelan-McDermid syndrome. Further analysis via traditional karyotyping, Optical Genome Mapping (OGM), and PacBio long-read sequencing revealed a more complex landscape of chromosomal rearrangements in this individual, including a balanced 3;12 translocation, and an unbalanced 17;22 translocation. The proband's phenotypic presentation is thought to be the result of Phelan-McDermid syndrome and represents an expansion of the described phenotypes to include significant respiratory failure. This study underscores the challenges and importance of comprehensive genetic testing in elucidating complex presentations and highlights the need for complementary testing methods to overcome limitations in resolution.

Impact of Chronic Kidney Disease on Aortic Dissection in Patients with Polycystic Kidney Disease: A Fifteen-year Nationwide Population-based Cohort Study in Taiwan

Background: Aortic dissection is a life-threatening condition associated with polycystic kidney disease (PKD). Additionally, PKD often progresses to chronic kidney disease (CKD), a known risk factor for cardiovascular disease. However, the impact of CKD on aortic dissection, particularly in patients with PKD, remains unclear. This study aims to investigate the effects of both CKD and PKD on aortic dissection. Materials and methods: This nationwide, population-based, retrospective cohort study used data from the National Health Insurance Research Database (NHIRD) in Taiwan. The primary outcome evaluated in this study was the cumulative incidence of aortic dissection, compared between PKD patients and a control group without PKD over a 15-year follow-up period. CKD subgroup analyses were performed to further assess the impact of CKD progression on the development of aortic dissection. Results: From 2000 to 2015, this study included 9,192 PKD patients and 36,768 matched controls without PKD from the NHIRD. Our findings demonstrated that PKD patients who developed aortic dissection had a higher incidence of comorbidities, including hypertension and coronary artery disease. Aortic dissection was more prevalent among male patients, individuals over 45 years of age, and those in the lowest insured premium group. PKD patients had a 2.53-fold higher adjusted hazard ratio (HR) for developing aortic dissection compared to the control group (95% CI: 1.74 to 3.66, p < 0.001). Notably, PKD patients with concurrent hypertension had a 7.77-fold increased risk of aortic dissection (95% CI: 4.97 to 12.13, p < 0.001). In CKD subgroup analyses, PKD patients without CKD and those with CKD had adjusted HRs of 1.74 and 3.38, respectively (p < 0.001). Among PKD patients with CKD, those who initiated hemodialysis (HD) and those who did not showed adjusted HRs of 3.95 and 2.74, respectively, for aortic dissection (p < 0.001). Conclusion: These findings indicate that the risk of aortic dissection in PKD patients significantly increases with CKD progression. Additionally, hypertension is an independent risk factor for aortic dissection in PKD patients. Careful management of blood pressure and strategies to prevent CKD progression may reduce the incidence of aortic dissection in this population.

The Influence of Phosphoinositide Lipids in the Molecular Biology of Membrane Proteins: Recent Insights from Simulations

The phosphoinositide family of membrane lipids play diverse and critical roles in eukaryotic molecular biology. Much of this biological activity derives from interactions of phosphoinositide lipids with integral and peripheral membrane proteins, leading to modulation of protein structure, function, and cellular distribution. Since the discovery of phosphoinositides in the 1940s, combined molecular biology, biophysical, and structural approaches have made enormous progress in untangling this vast and diverse cellular network of interactions. More recently, in silico approaches such as molecular dynamics simulations have proven to be an asset in prospectively identifying, characterising, explaining the structural basis of these interactions, and in the best cases providing atomic level testable hypotheses on how such interactions control the function of a given membrane protein. This review details a number of recent seminal discoveries in phosphoinositide biology, enabled by advanced biomolecular simulation, and its integration with molecular biology, biophysical, and structural biology approaches. The results of the simulation studies agree well with experimental work, and in a number of notable cases have arrived at the key conclusion several years in advance of the experimental structures. SUMMARY: Hedger and Yen review developments in simulations of phosphoinositides and membrane proteins.

Commentary: Tolvaptan for Autosomal Dominant Polycystic Kidney Disease (ADPKD) - an update

Autosomal Dominant Polycystic Kidney Disease (ADPKD) affects up to 70 000 people in the UK and the most common inherited cause of end-stage kidney disease (ESKD). It is generally a late-onset multisystem disorder characterised by bilateral kidney cysts, liver cysts and an increased risk of intracranial aneurysms. Approximately 50% of people with ADPKD reach ESKD by age 60. Disease-associated pain, discomfort, fatigue, emotional distress and, impaired mobility can impact health-related quality of life. The approval of tolvaptan, a vasopressin V2 receptor antagonist, has greatly advanced the care for people with ADPKD, shifting the focus from general chronic kidney disease management to targeted therapeutic approaches. While guidance from NICE and SMC provides a foundational framework, this is not clear or comprehensive enough to offer practical guidance for healthcare professionals in real-world settings. This commentary expands on the previous United Kingdom Kidney Association (UKKA) commentary in 2016 with an updated evidence base, the incorporation of real-world data and expert opinion to provide practical guidance to healthcare professionals. Through co-development with people affected by ADPKD, it now incorporates valuable patient perspectives and offers practical recommendations for the UK kidney community seeking to harmonise the quality of care of all people with ADPKD.

Electrolyte and metabolite composition of cystic fluid from a rat model of ARPKD

Fluid-filled cysts are the key feature of polycystic kidney disease, which eventually leads to renal failure. We analyzed the composition of cyst fluid from a rat model of autosomal recessive polycystic kidney disease, the PCK rat, and identified sexual differences. Our results demonstrate that the ion composition of cyst fluid differs from that of urine or plasma. Untargeted metabolomics combined with transcriptomic data identified tryptophan metabolism, enzyme metabolism, steroid hormone biosynthesis, and fatty acid metabolism as pathways differing between male and female PCK rats. We quantified 42 amino acids in the cyst fluid (PCK only), plasma, and urine of male and female PCK rats and Sprague Dawley rats. Taurine was the most concentrated amino acid present in the cyst fluid, and PCK rat urinary taurine excretion was over 3-fold greater than Sprague Dawley rats. Understanding the composition of cyst fluid provides valuable insights into disease pathophysiology and may help identify potential dietary or pharmacological interventions to mitigate disease progression and improve patient outcomes.

Iron and ferroptosis in kidney disease: molecular and metabolic mechanisms

Maintaining iron homeostasis is necessary for kidney functioning. There is more and more research indicating that kidney disease is often caused by iron imbalance. Over the past decade, ferroptosis' role in mediating the development and progression of renal disorders, such as acute kidney injury (renal ischemia-reperfusion injury, drug-induced acute kidney injury, severe acute pancreatitis induced acute kidney injury and sepsis-associated acute kidney injury), chronic kidney disease (diabetic nephropathy, renal fibrosis, autosomal dominant polycystic kidney disease) and renal cell carcinoma, has come into focus. Thus, knowing kidney iron metabolism and ferroptosis regulation may enhance disease therapy. In this review, we discuss the metabolic and molecular mechanisms of iron signaling and ferroptosis in kidney disease. We also explore the possible targets of ferroptosis in the therapy of renal illness, as well as their existing limitations and future strategies.

Moving toward a better understanding of renal lymphatics: challenges and opportunities

The development of lymphatic-specific markers has enabled detailed visualization of the lymphatic vascular network that has greatly enhanced our ability to explore this often-overlooked system. Lymphatics remove fluid, solutes, macromolecules, and cells from the interstitium and return them to circulation. The kidneys have lymphatics. As in other organs, the kidney lymphatic vessels are highly sensitive to changes in the local microenvironment. The sensitivity to its milieu may be especially relevant in kidneys because they are central in regulating fluid homeostasis and clearance of metabolites delivered into and eliminated from the renal interstitial compartment. Numerous physiologic conditions and diseases modify the renal interstitial volume, pressure, and composition that can, in turn, influence the growth and function of the renal lymphatics. The impact of the renal microenvironment is further heightened by the fact that kidneys are encapsulated. This review considers the development, structure, and function of the renal lymphatic vessels and explores how factors within the kidney interstitial compartment modify their structure and functionality. Moreover, although currently there are no pharmaceutical agents that specifically target the lymphatic network, we highlight several medications currently used in children with kidney disease and hypertension that have significant but underappreciated effects on lymphatics.

Identification of polycystin 2 missense mutants targeted for endoplasmic reticulum-associated degradation

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder leading to end-stage renal disease. ADPKD arises from mutations in the PKD1 and PKD2 genes, which encode polycystin 1 (PC1) and polycystin 2 (PC2), respectively. PC2 is a nonselective cation channel, and disease-linked mutations disrupt normal cellular processes, including signaling and fluid secretion. In this study, we investigate whether disease-causing missense mutations compromise PC2 folding, an event that can lead to endoplasmic reticulum-associated degradation (ERAD). To this end, we first developed a new yeast PC2 expression system. We show that the yeast system provides a tractable model to investigate PC2 biogenesis and that a disease-associated PC2 mutant, D511V, exhibits increased polyubiquitination and accelerated proteasome-dependent degradation compared with wild-type PC2. In contrast to wild-type PC2, the PC2 D511V variant also failed to improve the growth of yeast strains that lack endogenous potassium transporters, highlighting a loss of channel function at the cell surface and a new assay for loss-of-function PKD2 variants. In HEK293 cells, both D511V along with another disease-associated mutant, R322Q, were targeted for ERAD. Consistent with defects in protein folding, the surface localization of these PC2 variants was increased by incubation at low-temperature in HEK293 cells, underscoring the potential to pharmacologically rescue these and perhaps other misfolded PC2 alleles. Together, our study supports the hypothesis that select PC2 missense variants are degraded by ERAD, the potential for screening PKD2 alleles in a new genetic system, and the possibility that chemical chaperone-based therapeutic interventions might be used to treat ADPKD.NEW & NOTEWORTHY This study indicates that select missense mutations in PC2, a protein that when mutated leads to ADPKD, result in protein misfolding and degradation via the ERAD pathway. Our work leveraged a new yeast model and an HEK293 cell model to discover the mechanism underlying PC2 instability and demonstrates the potential for pharmacological rescue. We also suggest that targeting the protein misfolding phenotype with chemical chaperones may offer new therapeutic strategies to manage ADPKD-related protein dysfunction.

KDIGO 2025 clinical practice guideline for the evaluation, management, and treatment of autosomal dominant polycystic kidney disease (ADPKD): executive summary

The Kidney Disease: Improving Global Outcomes (KDIGO) 2025 Clinical Practice Guideline for the Evaluation, Management, and Treatment of Autosomal Dominant Polycystic Kidney Disease (ADPKD) represents the first KDIGO guideline on this subject. Its scope includes nomenclature, diagnosis, prognosis, and prevalence; kidney manifestations; chronic kidney disease (CKD) management and progression, kidney failure, and kidney replacement therapy; therapies to delay progression of kidney disease; polycystic liver disease; intracranial aneurysms and other extrarenal manifestations; lifestyle and psychosocial aspects; pregnancy and reproductive issues; pediatric issues; and approaches to the management of people with ADPKD. The guideline has been developed with patient partners, clinicians, and researchers around the world, with the goal to generate a useful resource for healthcare providers and patients by providing actionable recommendations. The development of this guideline followed an explicit process of evidence review and appraisal, based on a rigorous, formal systematic literature review. The strength of recommendations follows the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. The guideline also provides practice points serving to direct clinical care or activities relating to areas for which a systematic review was not conducted. Limitations of the evidence are discussed. Research recommendations to address gaps in knowledge, and implications for policy and payment, are provided. The guideline targets a broad audience of healthcare providers, people living with ADPKD, and stakeholders involved in the various aspects of ADPKD care.

A Snake Toxin Derivative for Treatment of Hyponatremia and Polycystic Kidney Diseases

Key Points

MQ232, a disulfide-bond reticulated peptide derived from a natural snake toxin, was optimized as a new aquaretic drug candidate. MQ232 showed very low acute and chronic toxicity in rat and a biodistribution in mice strongly in favor of the kidney organs. MQ232 induced a sole aquaretic effect and demonstrated high in vivo activities on hyponatremia and polycystic kidney disease models.

Background

Vaptans were developed at the end of the previous century as vasopressin type 2 receptor antagonists. Tolvaptan is the most prescribed vaptan for hyponatremia and autosomal dominant polycystic kidney disease (ADPKD). However, its use is not as widespread as it should be due to price issues, a narrow therapeutic window, and some side effects. With the aim of discovering new efficient and safer vasopressin type 2 receptor antagonists, we screened animal venoms and identified several peptide toxins. Among them, mambaquaretin 1 (MQ1) displayed unique biological properties in that regard that it was the starting point for the development of a potential drug candidate.

Methods

Human T-cell assays and bioinformatics were used to mitigate MQ1 immunogenicity risk. MQ232 biodistribution in mice was performed by positron emission tomography. Pharmacodynamics, pharmacokinetics, and acute and chronic toxicity tests were performed on control rats. A rat experimental model of desmopressin-induced hyponatremia, ex vivo mice model of kidney cysts, and mice orthologous model of ADPKD were used to validate MQ232 efficacy in these pathologies.

Results

Three mutations were introduced in MQ1 to mitigate its immunogenicity risk. A fourth gain-of-function mutation was added to generate MQ232. MQ232's safety was demonstrated by a first toxic dose as high as 3000 nmol/kg and a strong kidney organ selectivity by positron emission tomography imaging, while showing almost no interaction with the liver. MQ232's efficacy was first demonstrated with an effective dose of 3 nmol/kg in a hyponatremic model and then in polycystic kidney models, on which MQ232 significantly reduced cyst growth.

Conclusions

We demonstrated, using diverse translational techniques and minimizing animal use, MQ232's safety and efficacy in several rodent models of hyponatremia and ADPKD.

Phenotypic outcomes of PKD1 compared with non-PKD1 genetically confirmed autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal Dominant Polycystic Kidney Disease (ADPKD) represents the most common monogenic cause of kidney failure. While identifying genetic variants predicts disease progression, characterization of recently described ADPKD-like variants is limited. We explored disease progression and genetic spectrum of genetically-confirmed ADPKD families with PKD1 and non-PKD1 variants.

METHODS

In this observational study, we evaluated the clinical (ADPKD-related complications, estimated glomerular filtration rate (eGFR) decline, and progression to kidney failure), radiological (height-adjusted total kidney volume (ht-TKV)), and genetic characteristics of ADPKD families referred to the Irish Kidney Gene Project. Logistic regression and Kaplan-Meier analyses examined relationships between genetic variants and disease progression.

RESULTS

Genomic sequencing was performed on 261 ADPKD families, and 75.8% (198/261 families, comprising 391 individuals) were identified to harbor pathogenic/likely pathogenic variants; 74.2% (147/198) PKD1 families and 23.2% (46/198) non-PKD1 families, which include PKD2 (n = 29 families), IFT140 variants (n = 4), ALG5, DNAJB11 and NEK8 (n = 3 each), ALG8 and ALG9 variants (n = 2 each). The remaining 2.6% (5/198) accounted for non-ADPKD variants. Compared to PKD1, non-PKD1 families were characterized by a milder phenotype; milder eGFR decline (- 1.4 mL/min/1.73m2/year vs. - 3.2; p < 0.001), smaller ht-TKV (449.7 mL/m vs. 1769; p 0.002) and a delayed progression towards kidney failure (73 vs. 52 years; HR: 0.12, p < 0.001 [95% CI: 0.07-0.19]). ADPKD-NEK8 heterozygotes demonstrated earlier progression to kidney failure (average age 8 vs. 49 years for PKD1; Bonferroni-corrected p 0.017).

CONCLUSION

Non-PKD1 variants have heterogeneous phenotypic and genotypic attributes resulting in milder disease, although ADPKD-NEK8 is an important exception with early progression.

Elucidating the Molecular Landscape of Cystic Kidney Disease: Old Friends, New Friends and Some Surprises

Cystic kidney diseases (CyKD) are a diverse group of disorders affecting more than 1 in 1000 individuals. Over 120 genes are implicated, primarily encoding components of the primary cilium, transcription factors, and morphogens. Prognosis varies greatly by molecular diagnosis. Causal variants are not identified in 10%-60% of individuals due to our limited understanding of CyKD. To elucidate the molecular landscape of CyKD, we queried the CAG Biobank using the ICD10 codes N28.1, Q61.1, Q61.11, Q61.19, Q61.2, Q61.3, and Q61.8 to identify individuals with CyKD. One hundred eight individuals met clinical criteria for CyKD and underwent proband-only exome sequencing. Causal variants were identified in 86/108 (80%) individuals. The most common molecular diagnoses were PKD1-related autosomal dominant polycystic kidney disease (32/108; 30%) and autosomal recessive polycystic kidney disease (21/108; 19%). Other common molecular diagnoses were ciliopathy syndromes (7/108; 6.5%) and Tuberous Sclerosis (6/108; 5.6%). Seven individuals had variants in genes not previously associated with CyKD (7/108; 6.5%). Candidate genes were identified in five individuals (5/108; 4.5%). Discordance between molecular and clinical diagnosis was present in two individuals. We demonstrate a high molecular diagnosis rate in individuals with CyKD that can result in diagnostic reclassification, supporting a role for genetic testing in CyKD.

Defining the Polycystin Pharmacophore Through HTS & Computational Biophysics

Background and Purpose

Polycystins (PKD2, PKD2L1) are voltage-gated and Ca2+-modulated members of the transient receptor potential (TRP) family of ion channels. Loss of PKD2L1 expression results in seizure-susceptibility and autism-like features in mice, whereas variants in PKD2 cause autosomal dominant polycystic kidney disease. Despite decades of evidence clearly linking their dysfunction to human disease and demonstrating their physiological importance in the brain and kidneys, the polycystin pharmacophore remains undefined. Contributing to this knowledge gap is their resistance to drug screening campaigns, which are hindered by these channels' unique subcellular trafficking to organelles such as the primary cilium. PKD2L1 is the only member of the polycystin family to form constitutively active ion channels on the plasma membrane when overexpressed.

Experimental Approach

HEK293 cells stably expressing PKD2L1 F514A were pharmacologically screened via high-throughput electrophysiology to identify potent polycystin channel modulators. In-silico docking analysis and mutagenesis were used to define the receptor sites of screen hits. Inhibition by membrane-impermeable QX-314 was used to evaluate PKD2L1's binding site accessibility.

Key Results

Screen results identify potent PKD2L1 antagonists with divergent chemical core structures and highlight striking similarities between the molecular pharmacology of PKD2L1 and voltage-gated sodium channels. Docking analysis, channel mutagenesis, and physiological recordings identify an open-state accessible lateral fenestration receptor within the pore, and a mechanism of inhibition that stabilizes the PKD2L1 inactivated state.

Conclusion and Implication

Outcomes establish the suitability of our approach to expand our chemical knowledge of polycystins and delineates novel receptor moieties for the development of channel-specific antagonists in TRP channel research.

Plasma proteome fingerprint in kidney diseases

Introduction

Kidney diseases pose a serious healthcare problem because of their high prevalence, worsening of patients' quality of life, and high mortality. Patients with kidney diseases are often asymptomatic until disease progression starts. Expensive renal replacement therapy options, such as dialysis or kidney transplant, are required for end-stage kidney disease. Early diagnosis of kidney pathology is crucial for slowing down or curbing further damage. This study aimed to analyze the features of the protein composition of blood plasma in patients with the most common kidney pathologies: kidney calculus, kidney cyst, and kidney cancer.

Methods

The study involved 75 subjects. Proteins associated with kidney pathologies (CFB, SERPINA3, HPX, HRG, SERPING1, HBB, ORM2, and CP) were proposed. These proteins are important participants of complement and coagulation cascade activation and lipid metabolism.

Results

The revealed phosphorylated proteoforms (CFB, C4A/C4B, F2, APOB, TTR, and NRAP) were identified. For them, modification sites were mapped on 3D protein models, and the potential role in formation of complexes with native partner proteins was assessed.

Discussion

The study demonstrates that the selected kidney pathologies have a similar proteomic profile, and patients can be classified into kidney pathology groups with an accuracy of (70-80)%.

A feedback loop between Paxillin and Yorkie sustains Drosophila intestinal homeostasis and regeneration

Balanced self-renewal and differentiation of stem cells are crucial for maintaining tissue homeostasis, but the underlying mechanisms of this process remain poorly understood. Here, from an RNA interference (RNAi) screen in adult Drosophila intestinal stem cells (ISCs), we identify a factor, Pax, which is orthologous to mammalian PXN, coordinates the proliferation and differentiation of ISCs during both normal homeostasis and injury-induced midgut regeneration in Drosophila. Loss of Pax promotes ISC proliferation while suppressing its differentiation into absorptive enterocytes (ECs). Mechanistically, our findings demonstrate that Pax is a conserved target gene of the Hippo signaling pathway in both Drosophila and mammals. Subsequent investigations have revealed Pax interacts with Yki and enhances its cytoplasmic localization, thereby establishing a feedback regulatory mechanism that attenuates Yki activity and ultimately inhibits ISCs proliferation. Additionally, Pax induces the differentiation of ISCs into ECs by activating Notch expression, thus facilitating the differentiation process. Overall, our study highlights Pax as a pivotal component of the Hippo and Notch pathways in regulating midgut homeostasis, shedding light on this growth-related pathway in tissue maintenance and intestinal function.

Generic residue numbering of the GAIN domain of adhesion GPCRs

The GPCR autoproteolysis inducing (GAIN) domain is an ancient protein fold ubiquitous in adhesion G protein-coupled receptors (aGPCR). It contains a tethered agonist necessary and sufficient for receptor activation. The GAIN domain is a hotspot for pathological mutations. However, the low primary sequence conservation of GAIN domains has thus far hindered the knowledge transfer across different GAIN domains in human receptors as well as species orthologs. Here, we present a scheme for generic residue numbering of GAIN domains, based on structural alignments of over 14,000 modeled GAIN domain structures. This scheme is implemented in the GPCR database (GPCRdb) and elucidates the domain topology across different aGPCRs and their homologs in a large panel of species. We identify conservation hotspots and statistically cancer-enriched positions in human aGPCRs and show the transferability of positional and structural information between GAIN domain homologs. The GAIN-GRN scheme provides a robust strategy to allocate structural homologies at the primary and secondary levels also to GAIN domains of polycystic kidney disease 1/PKD1-like proteins, which now renders positions in both GAIN domain types comparable to one another. In summary, our work enables researchers to generate hypothesis and rationalize experiments related to GAIN domain function and pathology.

A Computational Protocol for the Knowledge-Based Assessment and Capture of Pathologies

We propose that one of the main hurdles in delivering comprehensively informed care results from the challenges surrounding the extraction, representation, and retention of prior clinical experience and basic medical knowledge, as well as its translation into time- and context-informed actionable interventions. While emerging applications in artificial intelligence-based techniques, for example, large language models, offer impressive pattern association capabilities, they often fall short in producing human-readable explanations crucial to their integration into clinical care. Moreover, they require large well-defined and well-integrated data sets that typically conflict with the availability of such data in all but a few areas of medicine, for example, medical imaging and neuroimaging, noninvasive monitoring of bio-electrical activity, etc. In this chapter, we argue that approximate reasoning rooted in the knowledge that is explainable to the human clinician may offer attractive avenues for the introduction of such knowledge in a systematic way that supports formal retention, sharing, and reuse of new clinical and basic medical experience. We outline a conceptual protocol that targets the use of sparse and disparate data of different types and from different sources, seamlessly drawing on our collective experience and that of others. We illustrate the utility of such an integrative approach by applying the latter to the assessment and reconciliation of data from different experimental models, human and animal, in the example use case of a complex health condition.

Regulation of INPP5E in Ciliogenesis, Development, and Disease

Inositol polyphosphate-5-phosphatase E (INPP5E) is a 5-phosphatase critically involved in diverse physiological processes, including embryonic development, neurological function, immune regulation, hemopoietic cell dynamics, and macrophage proliferation, differentiation, and phagocytosis. Mutations in INPP5E cause Joubert and Meckel-Gruber syndromes in humans; these are characterized by brain malformations, microphthalmia, situs inversus, skeletal abnormalities, and polydactyly. Recent studies have demonstrated the key role of INPP5E in governing intracellular processes like endocytosis, exocytosis, vesicular trafficking, and membrane dynamics. Moreover, it regulates cellular signaling pathways by dephosphorylating the 5-phosphate of phosphatidylinositol-3,4,5-trisphosphate, phosphatidylinositol 4,5-bisphosphate, and phosphatidylinositol 3,5-bisphosphate. Despite recent advances, knowledge gaps persist regarding the function and molecular mechanism of INPP5E in various cells and species. This review integrates recent findings on the role of INPP5E in regulating cellular function, development, and the pathogenesis of various human disorders, emphasizing the molecular mechanism by which INPP5E regulates primary cilia assembly and function and critical signaling pathways. Identifying the importance of INPP5E in healthy and diseased states can advance our understanding of cellular processes and disease pathogenesis and provide a foundation for developing targeted therapeutic interventions.

Prospects for gene therapy in polycystic kidney disease

PURPOSE OF REVIEW

We aim to provide an updated perspective on the recent advancements in gene therapy for polycystic kidney disease (PKD), a genetic disorder with significant morbidity. Given the rapid evolution of gene therapy technologies and their potential for treating inherited diseases, this review explores the therapeutic prospects and challenges in applying these technologies to PKD.

RECENT FINDINGS

Significant progress has been made in understanding the genetic underpinnings of PKD, making it a prime candidate for gene therapy. Re-expression of the PKD genes, treatment with the C-terminal tail of polycystin 1 protein and antagomir therapy against miR-17 have shown promise in reducing cyst formation and preserving kidney function. The rapid development of gene-editing tools, antisense oligonucleotide-based strategies, programmable RNA, and advanced gene delivery systems has opened new possibilities for PKD treatment. However, challenges such as off-target effects, delivery efficiency, and long-term safety remain significant barriers to clinical application.

SUMMARY

Current research highlights the transformative potential of gene therapy for PKD. Ongoing studies are crucial to overcoming existing challenges and translating these findings into clinical practice. We highlight the need for multidisciplinary efforts to optimize gene-editing technologies and ensure their safety and efficacy in treating PKD.

The cystogenic effects of ouabain in autosomal dominant polycystic kidney disease require cell caveolae

We have previously shown that the hormone ouabain is a circulating factor which can accelerate the progression of autosomal dominant polycystic kidney disease (ADPKD). At physiologic concentrations, ouabain increases cyst area and fibrosis in kidneys from ADPKD but not wildtype mice. These effects are due to an increased affinity for ouabain by its receptor, Na,K-ATPase (NKA), in the kidneys of ADPKD mice which leads to over-activation of NKA signaling function. Previous studies suggested that ouabain's stimulation of NKA signal transduction is mediated by NKA located within cell caveolae. Here, we determined whether caveolae are involved in the ouabain-induced progression of ADPKD cysts. We generated an ADPKD mouse with a global knockout of the main structural component of caveolae, caveolin-1 (CAV1), which we confirmed lacks caveolae in the kidney. When given physiological amounts of ouabain for 5 months, Pkd1RC/RCCav1-/- mice did not exhibit any changes in cyst progression, contrasting with the Pkd1RC/RC mice which showed a significant increase in cystic area and kidney fibrosis. Also, measures of ouabain-induced cell proliferation, including the number of Ki67-positive nuclei and phosphorylation of the extracellular regulated kinase (ERK) and protein kinase B (Akt), did not increase in the Pkd1RC/RCCav1-/- mice compared with the Pkd1RC/RC mice. Moreover, the abnormally increased affinity for ouabain of NKA in Pkd1RC/RC mice was restored to wildtype levels in the Pkd1RC/RCCav1-/- mice. This work highlights the role of caveolae in ouabain-induced NKA signaling and ADPKD cyst progression.

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

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

Cardiac Localized Polycystin-2 in the Natriuretic Peptide Signaling Pathway and Hypertension

Key Points

Cardiac localized polycystin facilitates natriuretic peptide signaling pathways. Hypertension associated with autosomal dominant polycystic kidney disease may arise from impaired cardiac natriuretic peptide signaling.

Background

Hypertension is seen in 70% of patients with autosomal dominant polycystic kidney disease by age of 30 years before decline in kidney function. However, cardiac origins of hypertension, such as the natriuretic peptide signaling pathway, have not been fully investigated. We hypothesized that cardiomyocyte localized polycystin proteins contribute to production of natriuretic peptides, and loss of this pathway would contribute to hypertension.

Methods

Telemetry, echocardiography, and a molecular analysis of the natriuretic peptide pathway from left ventricular tissue of cardiomyocyte specific knockout models of polycystin-2 (cPC2-KO) mice and Cre control littermates were conducted. Complementary studies were conducted in ex vivo murine hearts, engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 knockout of PKD2 and in in vitro cell lines.

Results

cPC2-KO mice demonstrated diurnal hypertension. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide were unchanged between cPC2-KO and Cre mice. Analysis of the pathways involved in production, maturation, and activity of natriuretic peptides identified decreased transcription of chromogranin B, PCSK6, NPR1, and NFAT genes in cPC2-KOs. Human iPSC-derived cardiomyocytes with PC2-KO failed to produce ANP. Re-expression of polycystin-2 in a myoblast cell line, but not pathogenic forms of polycystin-2, restored ANP production.

Conclusions

Natriuretic peptide production required cardiac localized polycystin-2, and loss of this pathway may contribute to the development of hypertension in autosomal dominant polycystic kidney disease.

Podcast

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2024_10_08_ASN0000000000000490.mp3

Reduction of elevated Gli3 does not alter the progression of autosomal recessive polycystic kidney disease

Polycystic kidney diseases (PKD) are genetic disorders which disrupt kidney architecture and function. Autosomal recessive PKD (ARPKD) is a rare form of PKD, caused by mutations in PKHD1, and clinically more severe than the more common autosomal dominant PKD (ADPKD). Prior studies have implicated Hedgehog (Hh) signaling in ADPKD, with increased levels of Hh components in experimental ADPKD and reduced cystogenesis following pharmacological Hh inhibition. In contrast, the role of the Hh pathway in ARPKD is poorly understood. We hypothesized that Hh pathway activity would be elevated during ARPKD pathogenesis, and its modulation may slow disease progression. We utilized Cpk mice which phenocopy ARPKD and generated a PKHD1-mutant spheroid model in human collecting ducts. Significantly elevated levels of the Hh transcriptional effector Gli3 were found in Cpk mice, a finding replicated in PKHD1-mutant spheroids. In Cpk mice, total GLI3 and GLI3 repressor protein levels were also increased. Reduction of increased Gli3 levels via heterozygous genetic deletion in Cpk mice did not affect cyst formation. Additionally, lowering GLI3 transcripts to wildtype levels did not influence PKHD1-mutant spheroid size. Collectively, these data suggest attenuation of elevated Gli3 does not modulate murine and human models of ARPKD.

Progress of Induced Pluripotent Stem Cell-Derived Renal Organoids in Clinical Application

Background

Kidney disease has become a growing public health problem worldwide, and there is an urgent need to develop reliable models for investigating novel and effective treatment strategies. In recent years, kidney organoids, as novel models different from traditional two-dimensional cells and model animals, have attracted more and more attention. Current advances have allowed the generation of kidney organoids from the directed differentiation of induced pluripotent stem cells (iPSCs), which possess similar characteristics to embryonic stem cells, but bypass ethical constraints and have a wide range of sources.

Summary

Herein, the methods of generating renal organoids from iPSCs, the applications of iPSC-derived renal organoids in disease modeling, drug effectiveness detection, and regenerative medicine as well as the challenges were reviewed.

Key Messages

iPSC-derived renal organoids can be used to model kidney diseases and are great models for studying kidney injury and toxicity. Many efforts are needed to finally apply organoids into clinical application.

Therapeutic Potential of Ketogenic Interventions for Autosomal-Dominant Polycystic Kidney Disease: A Systematic Review

BACKGROUND

Recent findings have highlighted that abnormal energy metabolism is a key feature of autosomal-dominant polycystic kidney disease (ADPKD). Emerging evidence suggests that nutritional ketosis could offer therapeutic benefits, including potentially slowing or even reversing disease progression. This systematic review aims to synthesise the literature on ketogenic interventions to evaluate the impact in ADPKD.

METHODS

A systematic search was conducted in Medline, Embase, and Scopus using relevant Medical Subject Headings (MeSH) and keywords. Studies assessing ketogenic interventions in the management of ADPKD in both human and animal models were selected for data extraction and analysis.

RESULTS

Three animal reports and six human studies were identified. Ketogenic diets (KD) significantly slowed polycystic kidney disease (PKD) progression in rats with improved renal function and reduced cystic areas. There was reduced renal fibrosis and cell proliferation. The supplementation of beta-hydroxybutyrate (BHB) in rats also reduced PKD progression in a dose-dependent manner. Human studies (n = 129) on KD in ADPKD reported consistent body mass index (BMI) reduction across trials, with an average weight loss of ∼4 kg. Improvements in blood pressure were also noted. Ketosis was achieved in varying degrees. Effects on kidney function (eGFR) were beneficial. Results for kidney volume were mixed but most studies were underpowered for this outcome. Lipid profiles showed increases in total cholesterol (∼1 mmol/L) and LDL cholesterol (∼0.4 mmol/L) in most studies. Safety concerns such as "keto flu" symptoms, elevated uric acid levels, and occasional kidney stones were noted. Overall feasibility and adherence to the KD were rated positively by most participants.

CONCLUSIONS

Human studies are promising; however, they have been limited by small sample sizes and short durations. Larger, long-term trials are needed to assess the efficacy, adherence, and safety of ketogenic diets in people with ADPKD.

Gene therapy and kidney diseases

Chronic kidney disease (CKD) poses a significant global health challenge, projected to become one of the leading causes of death by 2040. Current treatments primarily manage complications and slow progression, highlighting the urgent need for personalized therapies targeting the disease-causing genes. Our increased understanding of the underlying genomic changes that lead to kidney diseases coupled with recent successful gene therapies targeting specific kidney cells have turned gene therapy and genome editing into a promising therapeutic approach for treating kidney disease. This review paper reflects on different delivery routes and systems that can be exploited to target specific kidney cells and the ways that gene therapy can be used to improve kidney health.

Atypical noncontiguous TSC2/PKD1 gene deletions presenting as tuberous sclerosis/polycystic kidney disease contiguous gene syndrome

Tuberous sclerosis complex (TSC) and autosomal dominant polycystic kidney disease (ADPKD) are genetically distinct disorders typically associated with pathogenic variants in TSC1 and TSC2 for the former and PKD1 and PKD2 for the latter. TSC2 and PKD1 lie adjacent to each other, and large deletions comprising both genes lead to TSC2/PKD1 contiguous gene deletion syndrome (CGS). In this study, we describe a young female patient exhibiting symptoms of TSC2/PKD1 CGS in which genetic analysis disclosed two noncontiguous partial gene deletions in TSC2 and PKD1 that putatively are responsible for the manifestations of the syndrome. Further analysis revealed that both deletions appear to be de novo on the maternal chromosome, presumably with a germline origin. Despite extensive analysis, no maternal chromosomal rearrangement triggering these pathogenic variants was detected. This case elucidates a unique pathogenesis for TSC2/PKD1 CGS, diverging from the common contiguous deletions typically observed, marking the first reported instance of TSC2/PKD1 CGS caused by independent, functionally significant partial gene deletions.

Kidney transplantation in patients with polycystic kidney disease: increased risk of infection does not compromise graft and patient survival

Background

Patients with autosomal dominant polycystic kidney disease (ADPKD) represent >10% of patients awaiting kidney transplantation. These patients are prone to potentially severe urinary tract (UTI) and liver cyst infections after transplantation. Whether such infections compromise outcome is unclear.

Methods

Between 2000 and 2017 we performed 193 kidney transplantations in patients with ADPKD. In 189 patients, we assessed the occurrence, frequency, and severity of infection episodes requiring inpatient treatment and their impact on graft and patient outcomes compared with 189 matched controls. Risk factors were analyzed by uni- and multivariable analyses.

Results

During a mean observation period of 77 months UTIs occurred more frequently in ADPKD patients (39.1% vs. 26.7%, P = .022; 0.8 ± 1.4 vs. 0.5 ± 1.1 episodes, P < .001). Eight ADPKD patients suffered from 19 episodes of liver cyst infection. Steroid medication (RR 3.04; P < .001) and recipient age (RR 1.05; P = .003) increased the risk for UTI/urosepsis, while nephrectomy reduced it (unilateral, RR 0.60; P = .088; bilateral, RR 0.45; P = .020). Patient survival was similar in both groups. The risk of graft failure was lower in ADPKD patients [hazard ratio (HR) 0.67; P = .047] due to a lower risk of death-censored graft loss (HR 0.47; P = .014). Donor age (HR 1.34; P = .002) and rejection (HR 8.47; P < .001) were risk factors for death-censored graft loss.

Conclusions

ADPKD patients are at increased risk of UTI and liver cyst infection after transplantation. Steroid medication and recipient age seem to increase the risk of UTI/urosepsis, while nephrectomy seems to reduce it. Nevertheless, patient survival was similar compared to non-ADPKD patients and death-censored graft survival even better.