[Show abstract][Hide abstract] ABSTRACT: In total, 1 in 1000 individuals carries a germline mutation in the PKD1 or PKD2 gene, which leads to autosomal dominant polycystic kidney disease (ADPKD). Cysts can form early in life and progressively increase in number and size during adulthood. Extensive research has led to the presumption that somatic inactivation of the remaining allele initiates the formation of cysts, and the progression is further accelerated by renal injury. However, this hypothesis is primarily on the basis of animal studies, in which the gene is inactivated simultaneously in large percentages of kidney cells. To mimic human ADPKD in mice more precisely, we reduced the percentage of Pkd1-deficient kidney cells to 8%. Notably, no pathologic changes occurred for 6 months after Pkd1 deletion, and additional renal injury increased the likelihood of cyst formation but never triggered rapid PKD. In mildly affected mice, cysts were not randomly distributed throughout the kidney but formed in clusters, which could be explained by increased PKD-related signaling in not only cystic epithelial cells but also, healthy-appearing tubules near cysts. In the majority of mice, these changes preceded a rapid and massive onset of severe PKD that was remarkably similar to human ADPKD. Our data suggest that initial cysts are the principal trigger for a snowball effect driving the formation of new cysts, leading to the progression of severe PKD. In addition, this approach is a suitable model for mimicking human ADPKD and can be used for preclinical testing.
Journal of the American Society of Nephrology 10/2014; · 9.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2, which encode polycystin-1 and polycystin-2, respectively. Rodent models are available to study the pathogenesis of polycystic kidney disease (PKD) and for preclinical testing of potential therapies-either genetically engineered models carrying mutations in Pkd1 or Pkd2 or models of renal cystic disease that do not have mutations in these genes. The models are characterized by age at onset of disease, rate of disease progression, the affected nephron segment, the number of affected nephrons, synchronized or unsynchronized cyst formation and the extent of fibrosis and inflammation. Mouse models have provided valuable mechanistic insights into the pathogenesis of PKD; for example, mutated Pkd1 or Pkd2 cause renal cysts but additional factors are also required, and the rate of cyst formation is increased in the presence of renal injury. Animal studies have also revealed complex genetic and functional interactions among various genes and proteins associated with PKD. Here, we provide an update on the preclinical models commonly used to study the molecular pathogenesis of ADPKD and test potential therapeutic strategies. Progress made in understanding the pathophysiology of human ADPKD through these animal models is also discussed.
[Show abstract][Hide abstract] ABSTRACT: Background
Rubinstein-Taybi syndrome (RSTS) is a multiple congenital anomalies-intellectual disability syndrome. One of the complications is keloid formation. Keloids are proliferative fibrous growths resulting from excessive tissue response to skin trauma.Objectives
To describe the clinical characteristics of keloids in individuals with RSTS reported in literature and in a cohort of personally evaluated RSTS individuals.Methods
We performed a literature search for descriptions of RSTS individuals with keloids. All known RSTS individuals in the Netherlands filled out three dedicated questionnaires. All individuals with (possible) keloids were personally evaluated. A further series of RSTS individuals from the UK were personally evaluated.ResultsReliable data were available on 62 of the 83 Dutch RSTS individuals and showed 15 RSTS individuals (24%) to have keloids. The 15 Dutch and 12 UK RSTS individuals with keloids demonstrated that most patients have multiple keloids (n>1: 82%; n>5: 30%). Mean age of onset is 11.9 years. The majority are located on shoulders and chest. Mean length x width of the largest keloid was 7.1 x 2.8 cm, mean thickness was 0.7 cm. All affected individuals complained of itching. Generally, treatment results were disappointing.Conclusions
Keloids occur in 24% of individuals with RSTS, either spontaneously or after a minor trauma, usually starting in early puberty. Management schedules have disappointing results. RSTS is a Mendelian disorder of known molecular basis, and offers excellent opportunities to study the pathogenesis of keloids in general and search for treatments.This article is protected by copyright. All rights reserved.
British Journal of Dermatology 08/2014; · 3.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autosomal-dominant polycystic kidney disease is characterized by progressive cyst formation and fibrosis in the kidneys. Here we describe an orthologous Pkd1nl,nl mouse model, with reduced expression of the normal Pkd1 transcript, on a fixed genetic background of equal parts C57Bl/6 and 129Ola/Hsd mice (B6Ola-Pkd1nl,nl). In these mice, the first cysts develop from mature proximal tubules around birth. Subsequently, larger cysts become visible at day 7, followed by distal tubule and collecting duct cyst formation, and progressive cystic enlargement to develop into large cystic kidneys within 4 weeks. Interestingly, cyst expansion was followed by renal volume regression due to cyst collapse. This was accompanied by focal formation of fibrotic areas, an increased expression of genes involved in matrix remodeling and subsequently an increase in infiltrating immune cells. After an initial increase in blood urea within the first 4 weeks, renal function remained stable over time and the mice were able to survive up to a year. Also, in kidneys of ADPKD patients collapsed cysts were observed, in addition to massive fibrosis and immune infiltrates. Thus, B6Ola-Pkd1nl,nl mice show regression of cysts and renal volume that is not accompanied by a reduction in blood urea levels.Kidney International advance online publication, 6 March 2013; doi:10.1038/ki.2013.13.
Kidney International 03/2013; · 8.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations in PKD1 (85%) or PKD2 (15%) account for almost all cases of autosomal dominant polycystic kidney disease (ADPKD). The ADPKD proteins, termed polycystin-1 (PC1) and polycystin-2 (PC2), interact via their C-termini to form a receptor-ion channel complex whose function and regulation is not fully understood. Here we report the first phosphorylated residue (Ser(829)) in PC2, whose dephosphorylation is mediated by PC1 binding through the recruitment of protein phosphatase-1 alpha (PP1α). Using a new phosphospecific antibody (pPC2) to this site, we demonstrate that Ser(829) is phosphorylated by Protein kinase A (PKA) but remains constitutively phosphorylated in cells and tissues lacking PC1. cAMP increased pSer(829) basolateral localization in MDCK cells in a time dependent manner and was essential for pronephric development in Xenopus embryos. When constitutively expressed, a complex phenotype associated with enhanced ATP-dependent ER Ca(2+) release and loss of growth suppression was observed in cycling cells. These results reveal a reciprocal functional link between PC1 and PC2 which is critically dependent on their interaction. Unopposed cAMP stimulated hyperphosphorylation of PC2 in the absence of functional PC1 could contribute to cyst initiation in PKD1 patients and represents a new molecular paradigm in understanding ADPKD pathogenesis.
Human Molecular Genetics 02/2013; · 6.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
There are limited therapeutic options to slow the progression of autosomal dominant polycystic kidney disease (ADPKD). Recent clinical studies indicate that somatostatin analogues are promising for treating polycystic liver disease and potentially also for the kidney phenotype. We report on the design of the DIPAK 1 (Developing Interventions to Halt Progression of ADPKD 1) Study, which will examine the efficacy of the somatostatin analogue lanreotide on preservation of kidney function in ADPKD.
The DIPAK 1 Study is an investigator-driven, randomized, multicenter, controlled, clinical trial.
Setting & Participants
We plan to enroll 300 individuals with ADPKD and estimated glomerular filtration rate (eGFR) of 30-60 mL/min/1.73 m2 who are aged 18-60 years.
Patients will be randomly assigned (1:1) to standard care or lanreotide, 120 mg, subcutaneously every 28 days for 120 weeks, in addition to standard care.
Main study outcome is the slope through serial eGFR measurements starting at week 12 until end of treatment for lanreotide versus standard care. Secondary outcome parameters include change in eGFR from pretreatment versus 12 weeks after treatment cessation, change in kidney volume, change in liver volume, and change in quality of life.
Blood and urine will be collected and questionnaires will be filled in following a fixed scheme. Magnetic resonance imaging will be performed for assessment of kidney and liver volume.
Assuming an average change in eGFR of 5.2 ± 4.3 (SD) mL/min/1.73 m2 per year in untreated patients, 150 patients are needed in each group to detect a 30% reduction in the rate of kidney function loss between treatment groups with 80% power, 2-sided α = 0.05, and 20% protocol violators and/or dropouts.
The design is an open randomized controlled trial and measurement of our primary end point does not begin at randomization.
The DIPAK 1 Study will show whether subcutaneous administration of lanreotide every 4 weeks attenuates disease progression in patients with ADPKD.
American Journal of Kidney Diseases 01/2013; · 5.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cilia are cell organelles that play important roles in cell motility, sensory and developmental functions and are involved in a range of human diseases, known as ciliopathies. Here, we search for novel human genes related to cilia using a strategy that exploits the previously reported tendency of cell type-specific genes to be coexpressed in the transcriptome of complex tissues. Gene coexpression networks were constructed using the noise-resistant WGCNA algorithm in 12 publicly available microarray datasets from human tissues rich in motile cilia: airways, fallopian tubes and brain. A cilia-related coexpression module was detected in 10 out of the 12 datasets. A consensus analysis of this module's gene composition recapitulated 297 known and predicted 74 novel cilia-related genes. 82% of the novel candidates were supported by tissue-specificity expression data from GEO and/or proteomic data from the Human Protein Atlas. The novel findings included a set of genes (DCDC2, DYX1C1, KIAA0319) related to a neurological disease dyslexia suggesting their potential involvement in ciliary functions. Furthermore, we searched for differences in gene composition of the ciliary module between the tissues. A multidrug-and-toxin extrusion transporter MATE2 (SLC47A2) was found as a brain-specific central gene in the ciliary module. We confirm the localization of MATE2 in cilia by immunofluorescence staining using MDCK cells as a model. While MATE2 has previously gained attention as a pharmacologically relevant transporter, its potential relation to cilia is suggested for the first time. Taken together, our large-scale analysis of gene coexpression networks identifies novel genes related to human cell cilia.
PLoS ONE 04/2012; 7(4):e35618. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Experimental studies have suggested that vasopressin plays a detrimental role in autosomal dominant polycystic kidney disease (ADPKD). It is, however, unknown whether endogenous vasopressin concentration is associated with kidney function decline in subjects with ADPKD.METHODS: We measured plasma copeptin (a marker of vasopressin) in 79 ADPKD subjects with renal function assessed during short-term follow-up by inulin clearance measured glomerular filtration rate (mGFR) and during long-term follow-up by Modification of Diet in Renal Disease (MDRD) equation estimated GFR (eGFR).RESULTS: In these subjects (43% male, age 36.8 ± 10.1 years, GFR 96.8 ± 18.2 mL/min/1.73 m(2)), median copeptin concentration at baseline was 2.71 [interquartile ranges (IQR) 1.63-5.46] pmol/L. Baseline copeptin concentration was inversely associated both with change in mGFR during follow-up for 3.3 (3.1-3.5) years, (R = -0.300, P = 0.01), as well as with change in eGFR during follow-up for 11.2 (4.5-14.3) years, (R = -0.302, P < 0.01). These associations were independent of age, gender and baseline GFR. Nine subjects started renal replacement therapy during follow-up of which eight had at baseline a copeptin concentration above the median in this population.CONCLUSION: In ADPKD subjects, a higher copeptin concentration is associated with kidney function decline during follow-up, suggesting that copeptin may be a new marker to predict kidney outcome in ADPKD.
[Show abstract][Hide abstract] ABSTRACT: How renal epithelial cells respond to increased pressure and the link with kidney disease states remain poorly understood. Pkd1 knockout or expression of a PC2 pathogenic mutant, mimicking the autosomal dominant polycystic kidney disease, dramatically enhances mechanical stress-induced tubular apoptotic cell death. We show the presence of a stretch-activated K(+) channel dependent on the TREK-2 K(2P) subunit in proximal convoluted tubule epithelial cells. Our findings further demonstrate that polycystins protect renal epithelial cells against apoptosis in response to mechanical stress, and this function is mediated through the opening of stretch-activated K(2P) channels. Thus, to our knowledge, we establish for the first time, both in vitro and in vivo, a functional relationship between mechanotransduction and mechanoprotection. We propose that this mechanism is at play in other important pathologies associated with apoptosis and in which pressure or flow stimulation is altered, including heart failure or atherosclerosis.
[Show abstract][Hide abstract] ABSTRACT: How renal epithelial cells respond to increased pressure
and the link with kidney disease states remain
poorly understood. Pkd1 knockout or expression of
a PC2 pathogenic mutant, mimicking the autosomal
dominant polycystic kidney disease, dramatically
enhances mechanical stress-induced tubular apoptotic
cell death. We show the presence of a
stretch-activated K+ channel dependent on the
TREK-2 K2P subunit in proximal convoluted tubule
epithelial cells. Our findings further demonstrate
that polycystins protect renal epithelial cells against
apoptosis in response to mechanical stress, and
this function is mediated through the opening of
stretch-activated K2P channels. Thus, to our knowledge,
we establish for the first time, both in vitro
and in vivo, a functional relationship between mechanotransduction
and mechanoprotection. We propose
that this mechanismis at play in other important
pathologies associated with apoptosis and in which
pressure or flow stimulation is altered, including
heart failure or atherosclerosis.
[Show abstract][Hide abstract] ABSTRACT: Inhibition of the mammalian target of rapamycin (mTOR) shows beneficial effects in animal models of polycystic kidney disease (PKD); however, two clinical trials in patients with autosomal dominant PKD failed to demonstrate a short-term benefit in either the early or progressive stages of disease. The stage of disease during treatment and the dose of mTOR inhibitors may account for these differing results. Here, we studied the effects of a conventional low dose and a higher dose of sirolimus (blood levels of 3 ng/ml and 30-60 ng/ml, respectively) on mTOR activity and renal cystic disease in two Pkd1-mutant mouse models at different stages of the disease. When initiated at early but not late stages of disease, high-dose treatment strongly reduced mTOR signaling in renal tissues, inhibited cystogenesis, accelerated cyst regression, and abrogated fibrosis and the infiltration of immune cells. In contrast, low-dose treatment did not significantly reduce renal cystic disease. Levels of p-S6Rp(Ser240/244), which marks mTOR activity, varied between kidneys; severity of the renal cystic phenotype correlated with the level of mTOR activity. Taken together, these data suggest that long-term treatment with conventional doses of sirolimus is insufficient to inhibit mTOR activity in renal cystic tissue. Mechanisms to increase bioavailability or to target mTOR inhibitors more specifically to kidneys, alone or in combination with other compounds, may improve the potential for these therapies in PKD.
Journal of the American Society of Nephrology 02/2012; 23(5):842-53. · 9.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Planar cell polarity (PCP) is the polarization of cells within the plane of an epithelial cell layer. PCP is important in many tissues in different processes. In the kidney, it is hypothesized to be important in acquiring and maintaining correct tubular diameter. Aberrant PCP has been shown to be involved in polycystic kidney disease. Therefore, research in this field requires a method to study PCP. As PCP and outward-in signaling via the cilia are interconnected, the position of the centrosome, the base of the cilium can be used as a read-out system for PCP. Here, we provide a method in which the position of the centrosome is measured as read-out for PCP.
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD), due to a heterozygous mutation in PKD1 or PKD2, is usually an adult onset disease. Renal cystic disease is generally milder in PKD2 patients than in PKD1 patients. Recently, several PKD1 patients with a severe renal cystic phenotype due to a second modifying PKD1 allele, or carrying two incomplete penetrant PKD1 alleles, have been described. This study reports for the first time a patient with neonatal onset of PKD homozygous for an incomplete penetrant PKD2 missense variant due to uniparental disomy.
Journal of Medical Genetics 11/2011; 49(1):37-40. · 5.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is an inherited systemic disease with intrarenal cystogenesis as its primary characteristic. A variety of mouse models provided information on the requirement of loss of balanced polycystin levels for initiation of cyst formation, the role of proliferation in cystogenesis and the signaling pathways involved in cyst growth and expansion. Here we will review the involvement of different signaling pathways during renal development, renal epithelial regeneration and cyst formation in ADPKD, focusing on planar cell polarity (PCP) and oriented cell division (OCD). This will be discussed in context of the hypothesis that aberrant PCP signaling causes cyst formation. In addition, the role of the Hippo pathway, which was recently found to be involved in cyst growth and tissue regeneration, and well-known for regulating organ size control, will be reviewed. The fact that Hippo signaling is linked to PCP signaling makes the Hippo pathway a novel cascade in cystogenesis. The newly gained understanding of the complex signaling network involved in cystogenesis and disease progression, not only necessitates refining of the current hypothesis regarding initiation of cystogenesis, but also has implications for therapeutic intervention strategies. This article is part of a Special Issue entitled: Polycystic Kidney Disease.
Biochimica et Biophysica Acta 05/2011; 1812(10):1249-55. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We introduce a framework for predicting novel protein-protein interactions (PPIs), based on Fisher's method for combining probabilities of predictions that are based on different data sources, such as the biomedical literature, protein domain and mRNA expression information. Our method compares favorably to our previous method based on text-mining alone and other methods such as STRING. We evaluated our algorithms through the prediction of experimentally found protein interactions underlying Muscular Dystrophy, Huntington's Disease and Polycystic Kidney Disease, which had not yet been recorded in protein-protein interaction databases. We found a 1.74-fold increase in the mean average prediction precision for dysferlin and a 3.09-fold for huntingtin when compared to STRING. The top 10 of predicted interaction partners of huntingtin were analysed in depth. Five were identified previously, and the other five were new potential interaction partners. The full matrix of human protein pairs and their prediction scores are available for download. Our framework can be extended to predict other types of relationships such as proteins in a complex, pathway or related disease mechanisms.
[Show abstract][Hide abstract] ABSTRACT: The renoprotective effect of vasopressin V2 receptor antagonist (V2RA) is currently being tested in a clinical trial in early autosomal dominant polycystic kidney disease (ADPKD). If efficacious, this warrants life-long treatment with V2RA, however, with associated side effects as polydipsia and polyuria. We questioned whether we could reduce the side effects without influencing the renoprotective effect by starting the treatment later in the disease or by lowering drug dosage.
To investigate this, we administered V2RA OPC-31260 at a high (0.1%) and low (0.05%) dose to a tamoxifen-inducible kidney epithelium-specific Pkd1-deletion mouse model starting treatment at Day 21 (early) or 42 (advanced). After 3 and 6 weeks of treatment, we monitored physiologic and potential renoprotective effects.
Initiation of V2RA treatment at advanced stage of the disease lacked renoprotective effects and had less pronounced physiologic effects than early initiation. After 3 weeks on a high dose, cyst ratio and kidney weight were reduced versus untreated controls (18 versus 25%, P = 0.05, and 0.33 versus 0.45 g, P = 0.03, respectively). After 6 weeks of treatment, however, this did not reach significance anymore, even at a high dose (cyst ratio 24 versus 27%, P = 0.12, and kidney weight 0.55 versus 0.66 g, P = 0.38).
Our results suggest that intervention with V2RA should be instituted early in ADPKD and that it might be necessary to further increase the dosage of this drug later in the disease to decrease cyst growth.
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD) caused by mutations in either the PKD1 or PKD2 gene is a major cause of end-stage renal failure. A number of compounds targeting specific signaling pathways were able to inhibit cystogenesis in rodent models and are currently being tested in clinical trials. However, given the complex signaling in ADPKD, an ideal therapy would likely have to comprise several pathways at once. Therefore, multitarget compounds may provide promising therapeutic interventions for the treatment of ADPKD. To test this hypothesis, we treated Pkd1-deletion mice with diferuloylmethane (curcumin), a compound without appreciable side effects and known to modulate several pathways that are also altered in ADPKD, e.g., mammalian target of rapamycin (mTOR) and Wnt signaling. After conditional inactivation of Pkd1, mTOR signaling was indeed elevated in cystic kidneys. Interestingly, also activation of signal transducers and activator of transcription 3 (STAT3) strongly correlated with cyst progression. Both pathways were effectively inhibited in vitro by curcumin. Importantly, Pkd1-deletion mice that were treated with curcumin and killed at an early stage of PKD displayed improved renal histology and reduced STAT3 activation, proliferation index, cystic index, and kidney weight/body weight ratios. In addition, renal failure was significantly postponed in mice with severe PKD. These data suggest that multitarget compounds hold promising potential for safe and effective treatment of ADPKD.
[Show abstract][Hide abstract] ABSTRACT: We identified a deletion of a gene encoding a subunit of RNA polymerases I and III, POLR1D, in an individual with Treacher Collins syndrome (TCS). Subsequently, we detected 20 additional heterozygous mutations of POLR1D in 252 individuals with TCS. Furthermore, we discovered mutations in both alleles of POLR1C in three individuals with TCS. These findings identify two additional genes involved in TCS, confirm the genetic heterogeneity of TCS and support the hypothesis that TCS is a ribosomopathy.
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive deterioration of renal function and formation of cysts, and is an important cause of end-stage renal disease. Previously we showed that tubular epithelial injury accelerates cyst formation in inducible Pkd1-deletion mice. In these mice, expression of the planar cell polarity (PCP) component Four-jointed (Fjx1) is decreased during epithelial repair, while in control mice Fjx1 expression is increased and may be required during tissue regeneration. In cystic kidneys, however, Fjx1 expression is also increased. Besides a PCP component, Four-jointed is also implicated in the Hippo-signalling pathway. This pathway is involved in organ size control by regulating proliferation and apoptosis. The role of Hippo signalling, together with the opposing expression pattern of Fjx1 during epithelial repair and at cystic stages, triggered us to investigate the activity of the Hippo pathway during these processes. Therefore, we examined its final effector molecule, the transcriptional co-activator Yes-associated protein (YAP) and observed that during tissue repair, YAP expression was not different between Pkd1-deletion mice and controls, ie during tissue regeneration YAP expression was increased and predominantly localized in the cytoplasm but normalized after tissue repair. At a later stage, however, in cystic epithelia and epithelia of dilated tubules, strong nuclear YAP accumulation was observed, accompanied by up-regulation of the YAP transcriptional targets Birc-3, Ctgf, InhbA, and Fjx1. Altered activity of the Hippo pathway was confirmed in renal tissues from human ADPKD and ARPKD patients, as well as in cystic renal tumours. Our data strengthen the concept that during epithelial repair Four-jointed is involved in PCP signalling, while in cystic kidneys it is related to Hippo signalling and cyst growth.
The Journal of Pathology 01/2011; 224(1):133-42. · 7.33 Impact Factor