[Show abstract][Hide abstract] ABSTRACT: Polycystic kidney diseases are characterized by the development of numerous bilateral renal cysts that continuously enlarge resulting in a decline of kidney function due to compression of intact nephrons. Cyst growth is driven by transepithelial chloride secretion which depends on both intracellular cAMP and calcium. Mechanisms that are involved in the regulation of the underlying secretory pathways remain incompletely understood. Here we show that glucose concentration has a strong impact on cyst growth of renal tubular cells within a collagen matrix as well as in embryonic kidneys deficient or competent for Pkd1. Glucose-dependent cyst growth correlates with the transcriptional induction of the calcium-activated chloride channel anoctamin 1 (ANO1) and its increased expression in the apical membrane of cyst-forming cells. Inhibition of ANO1 with the specific inhibitor CaCCinh-AO1 significantly decreases glucose-dependent cyst growth in both models. Ussing chamber analyses revealed increased apical chloride secretion of renal tubular cells upon exposure to high glucose medium which can also be inhibited by the use of CaCCinh-AO1. These data suggest that glycemic control may help to reduce renal cyst growth in patients with polycystic kidney disease.
Renal cyst growth depends on glucose concentration in two in vitro cyst models. High glucose leads to upregulation of the calcium-activated chloride channel ANO1. High glucose promotes calcium-activated chloride secretion via ANO1. Glucose-dependent secretion can be inhibited by a specific inhibitor of ANO1.
Journal of Molecular Medicine 09/2015; DOI:10.1007/s00109-015-1337-4 · 5.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal cyst formation, inflammation, and fibrosis. Macrophages infiltrate cystic kidneys, but the role of these and other inflammatory factors in disease progression are poorly understood. Here, we identified macrophage migration inhibitory factor (MIF) as an important regulator of cyst growth in ADPKD. MIF was upregulated in cyst-lining epithelial cells in polycysitn-1-deficient murine kidneys and accumulated in cyst fluid of human ADPKD kidneys. MIF promoted cystic epithelial cell proliferation by activating ERK, mTOR, and Rb/E2F pathways and by increasing glucose uptake and ATP production, which inhibited AMP-activated protein kinase signaling. MIF also regulated cystic renal epithelial cell apoptosis through p53-dependent signaling. In polycystin-1-deficient mice, MIF was required for recruitment and retention of renal macrophages, which promoted cyst expansion, and Mif deletion or pharmacologic inhibition delayed cyst growth in multiple murine ADPKD models. MIF-dependent macrophage recruitment was associated with upregulation of monocyte chemotactic protein 1 (MCP-1) and inflammatory cytokine TNF-α. TNF-α induced MIF expression, and MIF subsequently exacerbated TNF-α expression in renal epithelial cells, suggesting a positive feedback loop between TNF-α and MIF during cyst development. Our study indicates MIF is a central and upstream regulator of ADPKD pathogenesis and provides a rationale for further exploration of MIF as a therapeutic target for ADPKD.
The Journal of clinical investigation 05/2015; 125(6). DOI:10.1172/JCI80467 · 13.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polycystic kidney disease (PKD) is one of the most common life-threatening genetic diseases. Jared J. Grantham, M.D., has done more than any other individual to promote PKD research around the world. However, despite decades of investigation there is still no approved therapy for PKD in the United States. In May 2014, the University of Kansas Medical Center hosted a symposium in Kansas City honoring the occasion of Dr. Grantham's retirement and invited all the awardees of the Lillian Jean Kaplan International Prize for Advancement in the Understanding of Polycystic Kidney Disease to participate in a forward-thinking and interactive forum focused on future directions and innovations in PKD research. This article summarizes the contributions of the 12 Kaplan awardees and their vision for the future of PKD research.
Journal of the American Society of Nephrology 05/2015; 26(9). DOI:10.1681/ASN.2014121192 · 9.34 Impact Factor
[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; 26(6). DOI:10.1681/ASN.2013080864 · 9.34 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; 171(3). DOI:10.1111/bjd.13124 · 4.28 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; 83(6). DOI:10.1038/ki.2013.13 · 8.56 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; 22(10). DOI:10.1093/hmg/ddt031 · 6.39 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; 63(3). DOI:10.1053/j.ajkd.2013.10.011 · 5.90 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. DOI:10.1371/journal.pone.0035618 · 3.23 Impact Factor
[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. DOI:10.1681/ASN.2011040340 · 9.34 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. DOI:10.1136/jmedgenet-2011-100452 · 6.34 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.