Harris, Peter C

The progression of autosomal dominant polycystic kidney disease (ADPKD), an inherited kidney disease, is associated with renal interstitial inflammation and fibrosis. CD74 has been known not only as a receptor of macrophage migration inhibitory factor (MIF) it can also have MIF independent functions. In this study, we report unknown roles and function of CD74 in ADPKD. We show that knockout of CD74 delays cyst growth in Pkd1 mutant kidneys. Knockout and knockdown of CD74 (1) normalize PKD associated signaling pathways, including ERK, mTOR and Rb to decrease Pkd1 mutant renal epithelial cell proliferation, (2) decrease the activation of NF-κB and the expression of MCP-1 and TNF-alpha (TNF-α) which decreases the recruitment of macrophages in Pkd1 mutant kidneys, and (3) decrease renal fibrosis in Pkd1 mutant kidneys. We show for the first time that CD74 functions as a transcriptional factor to regulate the expression of fibrotic markers, including collagen I (Col I), fibronectin, and α-smooth muscle actin (α-SMA), through binding on their promoters. Interestingly, CD74 also regulates the transcription of MIF to form a positive feedback loop in that MIF binds with its receptor CD74 to regulate the activity of intracellular signaling pathways and CD74 increases the expression of MIF in ADPKD kidneys during cyst progression. We further show that knockout of MIF and targeting MIF with its inhibitor ISO-1 not only delay cyst growth but also ameliorate renal fibrosis through blocking the activation of renal fibroblasts and CD74 mediated the activation of TGF-β-Smad3 signaling, supporting the idea that CD74 is a key and novel upstream regulator of cyst growth and interstitial fibrosis. Thus, targeting MIF-CD74 axis is a novel therapeutic strategy for ADPKD treatment.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder worldwide and progresses to end-stage renal disease (ESRD). However, its precise mechanism is not fully understood. In recent years, epigenetic reprogramming has drawn increasing attention regarding its effect on cyst growth. However, considering the complexity of epigenetic mechanisms and the broad range of alterations of epigenetic components in ADPKD, identifying more specific epigenetic factors and understanding how they are mechanistically linked to promote cyst growth is relevant for the development of treatment for ADPKD. Here, we find that the histone methyltransferase SMYD3, which activates gene transcription via histone H3 lysine 4 trimethylation (H3K4me3), is upregulated in PKD1 mutant mouse and human ADPKD kidneys. Genetic knockout of SMYD3 in a PKD1 knockout mouse model delayed cyst growth and improved kidney function compared with PKD1 single knockout mouse kidneys. Immunostaining and Western blot assays indicated that SMYD3 regulated PKD1-associated signaling pathways associated with proliferation, apoptosis, and cell cycle effectors in PKD1 mutant renal epithelial cells and tissues. In addition, we found that SMYD3 localized to the centrosome and regulated mitosis and cytokinesis via methylation of α-tubulin at lysine 40. In addition, SMYD3 regulated primary cilia assembly in PKD1 mutant mouse kidneys. In summary, our results demonstrate that overexpression of SMYD3 contributes to cyst progression and suggests targeting SMYD3 as a potential therapeutic strategy for ADPKD.

AbstractBackgroundAutosomal dominant polycystic kidney disease (ADPKD) is the most prevalent monogenic renal disease progressing to end‐stage renal disease. There is a pressing need for the identification of early ADPKD biomarkers to enable timely intervention and the development of effective therapeutic approaches. Here, we profiled human urinary extracellular vesicles small RNAs by small RNA sequencing in patients with ADPKD and compared their differential expression considering healthy control individuals to identify dysregulated small RNAs and analyze downstream interaction to gain insight about molecular pathophysiology.MethodsThis is a cross‐sectional study where urine samples were collected from a total of 23 PKD1‐ADPKD patients and 28 healthy individuals. Urinary extracellular vesicles were purified, and small RNA was isolated and sequenced. Differentially expressed Small RNA were identified and functional enrichment analysis of the critical miRNAs was performed to identify driver genes and affected pathways.ResultsmiR‐320b, miR‐320c, miR‐146a‐5p, miR‐199b‐3p, miR‐671‐5p, miR‐1246, miR‐8485, miR‐3656, has_piR_020497, has_piR_020496 and has_piR_016271 were significantly upregulated in ADPKD patient urine extracellular vesicles and miRNA‐29c was significantly downregulated. Five ‘driver’ target genes (FBRS, EDC3, FMNL3, CTNNBIP1 and KMT2A) were identified.ConclusionsThe findings of the present study make significant contributions to the understanding of ADPKD pathogenesis and to the identification of novel biomarkers and potential drug targets aimed at slowing disease progression in ADPKD.

ABSTRACT Introduction Our main objective was to identify baseline prognostic factors predictive of rapid disease progression in a large unselected clinical autosomal dominant polycystic kidney disease (ADPKD) cohort. Methods A cross-sectional analysis was performed in 618 consecutive ADPKD patients assessed and followed-up for over a decade. A total of 123 patients (19.9%) had reached kidney failure by the study date. Data were available for the following: baseline eGFR (n = 501), genotype (n = 549), baseline ultrasound mean kidney length (MKL, n = 424) and height-adjusted baseline MKL (HtMKL, n = 377). Rapid disease progression was defined as an annualized eGFR decline (∆eGFR) of >2.5 mL/min/year by linear regression over 5 years (n = 158). Patients were further divided into slow, rapid and very rapid ∆eGFR classes for analysis. Genotyped patients were classified into several categories: PKD1 (T, truncating; or NT, non-truncating), PKD2, other genes (non-PKD1 or -PKD2), no mutation detected or variants of uncertain significance. Results A PKD1-T genotype had the strongest influence on the probability of reduced baseline kidney function by age. A multivariate logistic regression model identified PKD1-T genotype and HtMKL (>9.5 cm/m) as independent predictors for rapid disease progression. The combination of both factors increased the positive predictive value for rapid disease progression over age 40 years and of reaching kidney failure by age 60 years to 100%. Exploratory analysis in a subgroup with available total kidney volumes showed higher positive predictive value (100% vs 80%) and negative predictive value (42% vs 33%) in predicting rapid disease progression compared with the Mayo Imaging Classification (1C–E). Conclusion Real-world longitudinal data confirm the importance of genotype and kidney length as independent variables determining ∆eGFR. Individuals with the highest risk of rapid disease progression can be positively selected for treatment based on this combination.

There is a broad phenotypic spectrum of monogenic polycystic kidney diseases (PKDs). These disorders often involve cilia-related genes and lead to the development of fluid-filled cysts and eventual kidney function decline and failure. Preimplantation genetic testing for monogenic (PGT-M) disorders has moved into the clinical realm. It allows prospective parents to avoid passing on heritable diseases to their children, including monogenic PKD. The PGT-M process involves embryo generation through in vitro fertilization, with subsequent testing of embryos and selective transfer of those that do not harbor the specific disease-causing variant(s). There is a growing body of literature supporting the success of PGT-M for autosomal-dominant and autosomal-recessive PKD, although with important technical limitations in some cases. This technology can be applied to many other types of monogenic PKD and ciliopathies despite the lack of existing reports in the literature. PGT-M for monogenic PKD, like other forms of assisted reproductive technology, raises important ethical questions. When considering PGT-M for kidney diseases, as well as the potential to avoid disease in future generations, there are regulatory and ethical considerations. These include limited government regulation and unstandardized consent processes, potential technical errors, high cost and equity concerns, risks associated with pregnancy for mothers with kidney disease, and the impact on all involved in the process, including the children who were made possible with this technology.

ABSTRACT Background Autosomal dominant polycystic kidney disease (ADPKD) presents with variable disease severity and progression. Advanced imaging biomarkers may provide insights into cystic and non-cystic processes leading to kidney failure in different age groups. Methods This pilot study included 39 ADPKD patients with kidney failure, stratified into three age groups (<46, 46–56, >56 years old). Advanced imaging biomarkers were assessed using an automated instance cyst segmentation tool. The biomarkers were compared with an age- and sex-matched ADPKD cohort in early chronic kidney disease (CKD). Results Ht-total parenchymal volume correlated negatively with age at kidney failure. The median Ht-total parenchymal volume was significantly lower in patients older than 56 years. Cystic burden was significantly higher at time of kidney failure, especially in patients who reached it before age 46 years. The cyst index at kidney failure was comparable across age groups and Mayo Imaging Classes. Advanced imaging biomarkers showed higher correlation with Ht-total kidney volume in early CKD than at kidney failure. Cyst index and parenchymal index were relatively stable over 5 years prior to kidney failure, whereas Ht-total cyst volume and cyst parenchymal surface area increased significantly. Conclusion Age-related differences in advanced imaging biomarkers suggest variable pathophysiological mechanisms in ADPKD patients with kidney failure. Further studies are needed to validate the utility of these biomarkers in predicting disease progression and guiding treatment strategies.

Abstract Development of autosomal dominant polycystic kidney disease (ADPKD) involves renal epithelial cell abnormalities. Cystic fluid contains a high level of ATP that, among other effects, leads to a reduced reabsorption of electrolytes in cyst‐lining cells, and thus results in cystic fluid accumulation. Earlier, we demonstrated that Pkd1 RC/RC mice, a hypomorphic model of ADPKD, exhibit increased expression of pannexin‐1, a membrane channel capable of ATP release. In the current study, we found that human ADPKD cystic epithelia have higher pannexin‐1 abundance than normal collecting ducts. We hypothesized that inhibition of pannexin‐1 function with probenecid can be used to attenuate ADPKD development. Renal function in male and female Pkd1 RC/RC and control mice was monitored between 9 and 20 months of age. To test the therapeutic effects of probenecid (a uricosuric agent and a pannexin‐1 blocker), osmotic minipumps were implanted in male and female Pkd1 RC/RC mice, and probenecid or vehicle was administered for 42 days until 1 year of age. Probenecid treatment improved glomerular filtration rates and slowed renal cyst formation in male mice (as shown in histopathology). The mechanistic effects of probenecid on sodium reabsorption and fluid transport were tested on polarized mpkCCD cl4 cells subjected to short‐circuit current measurements, and in 3D cysts grown in Matrigel. In the mpkCCD cl4 epithelial cell line, probenecid elicited higher ENaC currents and attenuated in vitro cyst formation, indicating lower sodium and less fluid retention in the cysts. Our studies open new avenues of research into targeting pannexin‐1 in ADPKD pathology.

Background Height-adjusted total kidney volume (htTKV) measured by imaging defined as Mayo Imaging Class (MIC) is a validated prognostic measure for autosomal dominant polycystic kidney disease (ADPKD) in adults to predict and stratify disease progression. However, no stratification tool is currently available in pediatric ADPKD. Because magnetic resonance imaging and computed tomography in children are difficult, we propose a novel 3D ultrasound-based pediatric Leuven Imaging Classification to complement the MIC. Methods A prospective study cohort of 74 patients with genotyped ADPKD (37 female) was followed longitudinally with ultrasound, including 3D ultrasound, and they underwent in total 247 3D ultrasound assessments, with patients' median age (interquartile range [IQR]) at diagnosis of 3 (IQR, 0–9) years and at first 3D ultrasound evaluation of 10 (IQR, 5–14) years. First, data matching was done to the published MIC classification, followed by subsequent optimization of parameters and model type. Results PKD1 was confirmed in 70 patients (95%), PKD2 in three (4%), and glucosidase IIα unit only once (1%). Over these 247 evaluations, the median height was 143 (IQR, 122–166) cm and total kidney volume was 236 (IQR, 144–344) ml, leading to an htTKV of 161 (IQR, 117–208) ml/m. Applying the adult Mayo classification in children younger than 15 years strongly underestimated ADPKD severity, even with correction for height. We therefore optimized the model with our pediatric data and eventually validated it with data of young patients from Mayo Clinic and the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease used to establish the MIC. Conclusions We proposed a five-level Leuven Imaging Classification ADPKD pediatric model as a novel classification tool on the basis of patients' age and 3D ultrasound-htTKV for reliable discrimination of childhood ADPKD severity.

Total kidney volume (TKV) is a valuable readout in preclinical studies for autosomal dominant and autosomal recessive polycystic kidney diseases (ADPKD and ARPKD). Since conventional TKV assessment by manual contouring of kidney areas in all images is time-consuming, we developed a template-based semiautomatic image segmentation method (SAM) and validated it in three commonly used ADPKD and ARPKD models. SAM-based TKV measurements were fast, highly reproducible, and accurate across mouse and rat ARPKD and ADPKD models.

ABSTRACT Background Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal monogenic disease, characterized by bilateral accumulation of renal fluid-filled cysts leading to progressive renal volume enlargement and gradual impairment of kidney function, often resulting in end-stage renal disease. Kuwait could provide valuable genetic insights about ADPKD, including intrafamilial phenotypic variation, given its large household size. This study aims to provide a comprehensive description of the pathogenic variants linked to ADPKD in the Kuwaiti population using multiple genetic analysis modalities and to describe and analyse the ADPKD phenotypic spectrum in terms of kidney function, kidney volume and renal survival. Methods A total of 126 ADPKD patients from 11 multiplex families and 25 singletons were recruited into the study. A combination of targeted next-generation sequencing (tNGS), long-range polymerase chain reaction, Sanger sequencing and multiplex ligation-dependent probe amplification were utilized for genetic diagnosis. Clinical evaluation was conducted through renal function testing and ultrasonographic kidney volume analysis. Results We identified 29 ADPKD pathogenic mutations from 36 families achieving an overall molecular genetic diagnostic rate of 112/126 (88.9%), including 29/36 (80.6%) in families. A total of 28/36 (77.8%) families had pathogenic mutations in PKD1, of which 17/28 (60.7%) were truncating, and 1/36 (2.8%) had a pathogenic variant in the IFT140 gene. A total of 20/29 (69%) of the identified ADPKD mutations were novel and described for the first time, including a TSC2-PKD1 contiguous syndrome. Clinical analysis indicated that genetically unresolved ADPKD cases had no apparent association between kidney volume and age. Conclusion We describe for the first time the genetic landscape of ADPKD in Kuwait. The observed genetic heterogeneity underlining ADPKD along with the wide phenotypic spectrum reveal the level of complexity in disease pathophysiology. ADPKD genetic testing could improve the care of patients through improved disease prognostication, guided treatment and genetic counselling. However, to fulfil the potential of genetic testing, it is important to overcome the hurdle of genetically unresolved ADPKD cases.