Model Of Autosomal Dominant Polycystic Kidney Disease Research Articles

Integrin-Linked Kinase Signaling Promotes Cyst Growth and Fibrosis in Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by innumerous fluid-filled cysts and progressive deterioration of renal function. Previously, we showed that periostin, a matricellular protein involved in tissue repair, is markedly overexpressed by cyst epithelial cells. Periostin promotes cell proliferation, cyst growth, interstitial fibrosis, and the decline in renal function in PKD mice. Here, we investigated the regulation of these processes by the integrin-linked kinase (ILK), a scaffold protein that links the extracellular matrix to the actin cytoskeleton and is stimulated by periostin. Pharmacologic inhibition or shRNA knockdown of ILK prevented periostin-induced Akt/mammalian target of rapamycin (mTOR) signaling and ADPKD cell proliferation in vitro Homozygous deletion of ILK in renal collecting ducts (CD) of Ilkfl/fl ;Pkhd1-Cre mice caused tubule dilations, apoptosis, fibrosis, and organ failure by 10 weeks of age. By contrast, Ilkfl/+ ;Pkhd1-Cre mice had normal renal morphology and function and survived >1 year. Reduced expression of ILK in Pkd1fl/fl ;Pkhd1-Cre mice, a rapidly progressive model of ADPKD, decreased renal Akt/mTOR activity, cell proliferation, cyst growth, and interstitial fibrosis, and significantly improved renal function and animal survival. Additionally, CD-specific knockdown of ILK strikingly reduced renal cystic disease and fibrosis and extended the life of pcy/pcy mice, a slowly progressive PKD model. We conclude that ILK is critical for maintaining the CD epithelium and renal function and is a key intermediate for periostin activation of signaling pathways involved in cyst growth and fibrosis in PKD.

Rapamycin treatment dose-dependently improves the cystic kidney in a new ADPKD mouse model via the mTORC1 and cell-cycle-associated CDK1/cyclin axis.

Although translational research into autosomal dominant polycystic kidney disease (ADPKD) and its pathogenesis has made considerable progress, there is presently lack of standardized animal model for preclinical trials. In this study, we developed an orthologous mouse model of human ADPKD by cross‐mating Pkd2 conditional‐knockout mice (Pkd2 f3) to Cre transgenic mice in which Cre is driven by a spectrum of kidney‐related promoters. By systematically characterizing the mouse model, we found that Pkd2 f3/f3 mice with a Cre transgene driven by the mouse villin‐1 promoter (Vil‐Cre;Pkd2 f3/f3) develop overt cysts in the kidney, liver and pancreas and die of end‐stage renal disease (ESRD) at 4–6 months of age. To determine whether these Vil‐Cre;Pkd2 f3/f3 mice were suitable for preclinical trials, we treated the mice with the high‐dose mammalian target of rapamycin (mTOR) inhibitor rapamycin. High‐dose rapamycin significantly increased the lifespan, lowered the cystic index and kidney/body weight ratio and improved renal function in Vil‐Cre;Pkd2 f3/f3 mice in a time‐ and dose‐dependent manner. In addition, we further found that rapamycin arrested aberrant epithelial‐cell proliferation in the ADPKD kidney by down‐regulating the cell‐cycle‐associated cyclin‐dependent kinase 1 (CDK1) and cyclins, namely cyclin A, cyclin B, cyclin D1 and cyclin E, demonstrating a direct link between mTOR signalling changes and the polycystin‐2 dysfunction in cystogenesis. Our newly developed ADPKD model provides a practical platform for translating in vivo preclinical results into ADPKD therapies. The newly defined molecular mechanism by which rapamycin suppresses proliferation via inhibiting abnormally elevated CDK1 and cyclins offers clues to new molecular targets for ADPKD treatment.

MicroRNA-17 family promotes polycystic kidney disease progression through modulation of mitochondrial metabolism

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of renal failure. Here we identify miR-17 as a target for the treatment of ADPKD. We report that miR-17 is induced in kidney cysts of mouse and human ADPKD. Genetic deletion of the miR-17∼92 cluster inhibits cyst proliferation and PKD progression in four orthologous, including two long-lived, mouse models of ADPKD. Anti-miR-17 treatment attenuates cyst growth in short-term and long-term PKD mouse models. miR-17 inhibition also suppresses proliferation and cyst growth of primary ADPKD cysts cultures derived from multiple human donors. Mechanistically, c-Myc upregulates miR-17∼92 in cystic kidneys, which in turn aggravates cyst growth by inhibiting oxidative phosphorylation and stimulating proliferation through direct repression of Pparα. Thus, miR-17 family is a promising drug target for ADPKD, and miR-17-mediated inhibition of mitochondrial metabolism represents a potential new mechanism for ADPKD progression.

STAT5 drives abnormal proliferation in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) leads to renal failure. The hallmark of ADPKD is increased epithelial proliferation, which has been proposed to be due to atypical signaling including abnormal JAK-STAT activity. However, the relative contribution of JAK-STAT family members in promoting proliferation in ADPKD is unknown. Here, we present siRNA JAK-STAT-focused screens discovering a previously unknown proliferative role for multiple JAK-STAT components (including STAT1, STAT2, STAT4, STAT5a, and STAT5b). Amongst these, we selected to study the growth hormone/growth hormone receptor/STAT5-axis because of its known role as a regulator of growth in nonrenal tissues. Loss of STAT5 function, facilitated by pharmacological inhibition or siRNAs, significantly reduced proliferation with an associated reduction in cyst growth invitro. To study whether STAT5 is abnormally activated invivo, we analyzed its expression using two independent mouse models of ADPKD. STAT5 was nuclear, thus activated, in renal epithelial cyst lining cells in both models. To test whether forced activation of STAT5 can modulate proliferation of renal cells invivo, irrespective of the Pkd1 status, we overexpressed growth hormone. These mice showed increased STAT5 activity in renal epithelial cells, which correlated with de novo expression of cyclin D1, a STAT5 target gene. Chromatin immunoprecipitation experiments revealed that STAT5 transcriptionally activated cyclin D1 in a growth hormone-dependent fashion, thus providing a mechanism into how STAT5 enhances proliferation. Finally, we provide evidence of elevated serum growth hormone in Pkd1 mutant mice. Thus, the growth hormone/STAT5 signaling axis is a novel therapeutic target in ADPKD.

Autophagy activators suppress cystogenesis in an autosomal dominant polycystic kidney disease model.

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in either PKD1 or PKD2. It is one of the most common heritable human diseases with eventual development of renal failure; however, effective treatment is lacking. While inhibition of mechanistic target of rapamycin (mTOR) effectively slows cyst expansions in animal models, results from clinical studies are controversial, prompting further mechanistic studies of mTOR-based therapy. Here, we aim to establish autophagy, a downstream pathway of mTOR, as a new therapeutic target for PKD. We generated zebrafish mutants for pkd1 and noted cystic kidney and mTOR activation in pkd1a mutants, suggesting a conserved ADPKD model. Further assessment of the mutants revealed impaired autophagic flux, which was conserved in kidney epithelial cells derived from both Pkd1-null mice and ADPKD patients. We found that inhibition of autophagy by knocking down the core autophagy protein Atg5 promotes cystogenesis, while activation of autophagy using a specific inducer Beclin-1 peptide ameliorates cysts in the pkd1a model. Treatment with compound autophagy activators, including mTOR-dependent rapamycin as well as mTOR-independent carbamazepine and minoxidil, markedly attenuated cyst formation and restored kidney function. Finally, we showed that combination treatment with low doses of rapamycin and carbamazepine was able to attenuate cyst formation as effectively as a single treatment with a high dose of rapamycin alone. In summary, our results suggested a modifying effect of autophagy on ADPKD, established autophagy activation as a novel therapy for ADPKD, and presented zebrafish as an efficient vertebrate model for developing PKD therapeutic strategies.

Differences in the timing and magnitude of Pkd1 gene deletion determine the severity of polycystic kidney disease in an orthologous mouse model of ADPKD.

Development of a disease‐modifying therapy to treat autosomal dominant polycystic kidney disease (ADPKD) requires well‐characterized preclinical models that accurately reflect the pathology and biochemical changes associated with the disease. Using a Pkd1 conditional knockout mouse, we demonstrate that subtly altering the timing and extent of Pkd1 deletion can have a significant impact on the origin and severity of kidney cyst formation. Pkd1 deletion on postnatal day 1 or 2 results in cysts arising from both the cortical and medullary regions, whereas deletion on postnatal days 3–8 results in primarily medullary cyst formation. Altering the extent of Pkd1 deletion by modulating the tamoxifen dose produces dose‐dependent changes in the severity, but not origin, of cystogenesis. Limited Pkd1 deletion produces progressive kidney cystogenesis, accompanied by interstitial fibrosis and loss of kidney function. Cyst growth occurs in two phases: an early, rapid growth phase, followed by a later, slow growth period. Analysis of biochemical pathway changes in cystic kidneys reveals dysregulation of the cell cycle, increased proliferation and apoptosis, activation of Mek‐Erk, Akt‐mTOR, and Wnt‐β‐catenin signaling pathways, and altered glycosphingolipid metabolism that resemble the biochemical changes occurring in human ADPKD kidneys. These pathways are normally active in neonatal mouse kidneys until repressed around 3 weeks of age; however, they remain active following Pkd1 deletion. Together, this work describes the key parameters to accurately model the pathological and biochemical changes associated with ADPKD in a conditional mouse model.

Lack of Benefit of Early Intervention with Dietary Flax and Fish Oil and Soy Protein in Orthologous Rodent Models of Human Hereditary Polycystic Kidney Disease.

Rationale for dietary advice in polycystic kidney disease (PKD) is based in part on animal studies that have examined non-orthologous models with progressive development of cystic disease. Since no model completely mimics human PKD, the purpose of the current studies was to examine the effects of dietary soy protein (compared to casein) or oils enriched in omega-3 fatty acids (fish or flax oil compared to soy oil) on early disease progression in two orthologous models of PKD. The models studied were Pkd2WS25/- mice as a model of autosomal dominant PKD, and PCK rats as a model of autosomal recessive PKD. After 13 weeks of feeding, dietary fish (but not flax) oil resulted in larger kidneys and greater kidney water content in female Pkd2WS25/- compared to control mice. After 12 weeks of feeding male PCK compared to control rats, both fish and flax compared to soy oil resulted in enlarged kidneys and livers, greater kidney water content and higher kidney cyst area in diseased rats. Dietary soy protein compared to casein had no effects in Pkd2WS25/- compared to control mice. In PCK rats, kidney and liver histology were not improved, but lower proteinuria and higher urine pH suggest that soy protein could be beneficial in the long term. Therefore, in contrast to studies in non-orthologous models during the progressive development phase, these studies in orthologous PKD models do not support dietary advice to increase soy protein or oils enriched in omega-3 oils in early PKD.

Effect of resveratrol on progression of polycystic kidney disease: a case of cautious optimism.

NDT Advance Access published May 17, 2016 Nephrol Dial Transplant (2016) 0: 1–4 doi: 10.1093/ndt/gfw097 In Focus Effect of resveratrol on progression of polycystic kidney disease: a case of cautious optimism Division of Nephrology and Hypertension, University of California, Irvine, 333 City Blvd West, Orange, CA 92868, USA and 2 Long Beach VA Healthcare System, Nephrology Section, Long Beach, CA, USA Correspondence and offprint requests to: Hamid Moradi; E-mail: hmoradi@uci.edu Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited genetic cause of chronic kidney disease, af- fecting 1 in 500 individuals in the USA. In addition, ADPKD is the most common genetic cause of end-stage renal disease (ESRD), accounting for ∼7–10% of patients on renal replace- ment therapy [1]. It is characterized by the development of fluid-filled cysts in the renal tubules and their progressive en- largement over time leading to the distortion of renal tissue and ongoing kidney damage and culminating in ESRD [2, 3]. At the molecular level, ADPKD is caused by mutations in the PKD1 (85%) or PKD2 (15%) genes, which encode the cilia-associated polycystin-1 (PC1) and polycystin-2 (PC2) pro- teins [4]. PC1 and PC2 are membrane proteins that are located in the primary cilia of the tubular epithelial cells, and while the ligand for PC1 has not been identified, PC2 is most likely a non- selective calcium channel [2, 3]. There are multiple mechan- isms by which mutations in the PKD1 and PKD2 genes result in cystogenesis, including increased cell proliferation, enhanced fluid secretion, abnormal cell–matrix interaction, alterations in cell polarity and abnormal ciliary structure and function [2]. However, there are also several nongenetic pathways that can contribute to the progression and modify the severity of ADPKD. This is evidenced by the fact that patients with ADPKD have large intrafamilial variability in renal function even between monozygotic twins and siblings [5]. In addition, in monozygotic twins, there can be significant differences in the age at which ESRD is reached, thereby highlighting the role of nonhereditary pathways in ADPKD-associated renal injury and progression of disease [5]. These include pathways related to growth factor and cytokine signaling [6]. The importance of in- flammation and cytokine signaling in PKD has been established in numerous studies over the past few decades. Gardner et al. [7] noted high concentrations of inflammatory chemokines and © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. cytokines in the cyst fluid from patients with ADPKD. Cowley et al. [8] subsequently demonstrated that increased expression of monocyte chemoattractant protein-1 (MCP-1) was accom- panied by accumulation of macrophages in the kidneys of rats with ADPKD. It is now known that MCP-1 is present in the urine of patients with ADPKD and that high levels of urinary MCP-1 correlate with the rate of cyst growth and progression of disease [9, 10]. In line with these discoveries, large numbers of activated macrophages have been found around renal cysts in animal models of ADPKD whose depletion inhibited epithelial cell proliferation and cyst growth and improved renal function [11]. Furthermore, Swenson-Fields et al. [12] demonstrated that increased numbers of macrophages expressing the M2 marker CD163 are also present in the interstitium of kidneys of patients with both AD and autosomal recessive PKD, some of which are in close proximity to the cysts. In turn, the cyst epithelial cells stimulated macrophage differentiation toward a distinct M2-like phenotype that, based on in vitro studies, pro- moted proliferation and microcyst formation. Furthermore, re- cent studies have demonstrated that macrophage migration inhibitory factor (MIF) is upregulated in the epithelial cells lining renal cysts and that this protein accumulates in the cyst fluid of patients with ADPKD [13]. MIF was found to be a key regulator of cyst growth in ADPKD via several converging mechanisms, including cytokine signaling. It was shown that MIF-dependent macrophage recruitment was associated with increased MCP-1 and tumor necrosis factor α (TNF-α) production, which in turn increased expression of MIF. Hence, a positive feedback loop between inflammation, inflam- matory cytokines and MIF was identified, with the end result being progression of the disease [13]. Therefore, besides the gen- etic abnormalities that instigate the underlying disease in ADPKD, inflammation, macrophage activation, differentiation Downloaded from http://ndt.oxfordjournals.org/ at University of California, Irvine on May 18, 2016 Hamid Moradi 1,2 and Nosratola D. Vaziri 2

Inhibition of histone deacetylase 6 activity reduces cyst growth in polycystic kidney disease

Abnormal proliferation of cyst-lining epithelium and increased intracystic fluid secretion via the cystic fibrosis transmembrane conductance regulator (CFTR) are thought to contribute to cyst growth in autosomal dominant polycystic kidney disease (ADPKD). Histone deacetylase 6(HDAC6) expression and activity are increased in certain cancers, neurodegenerative diseases, and in Pkd1-mutant renal epithelial cells. Inhibition of HDAC6 activity with specific inhibitors slows cancer growth. Here we studied the effect of tubacin, a specific HDAC6 inhibitor, on cyst growth in polycystic kidney disease. Treatment with tubacin prevented cyst formation in MDCK cells, an invitro model of cystogenesis. Cyclic AMP stimulates cell proliferation and activates intracystic CFTR-mediated chloride secretion in ADPKD. Treatment with tubacin downregulated cyclic AMP levels, inhibited cell proliferation, and inhibited cyclic AMP-activated CFTR chloride currents in MDCK cells. We also found that tubacin reduced cyst growth by inhibiting proliferation ofcyst-lining epithelial cells, downregulated cyclic AMP levels, and improved renal function in a Pkd1-conditional mouse model of ADPKD. Thus, HDAC6 could play a role in cyst formation and could serve as a potential therapeutic target in ADPKD.

Relationship of urinary endothelin-1 with estimated glomerular filtration rate in autosomal dominant polycystic kidney disease: a pilot cross-sectional analysis.

BackgroundThe pathogenesis of progressive renal insufficiency in autosomal dominant polycystic kidney disease (ADPKD) is unclear. Evidence from experimental models of ADPKD suggests that elevated endothelin-1 (ET-1) drives cyst growth, renal fibrosis and loss of renal function, but whether ET-1 is elevated in humans with ADPKD is uncertain.MethodsIn a cross-sectional study of ADPKD we measured urinary ET-1, a surrogate for ET-1 in kidney cortex, in spot collections corrected for creatinine. The volume of each kidney was measured using MRI-based stereology. The relationship of urine ET-1 with MDRD eGFR and kidney volume was modeled by multiple linear regression with adjustment for clinical covariates.ResultsPatients with ADPKD were ages 18 to 53 with eGFRs (median, interquartile range) of 63.2 (43.5–80.2) ml/min/1.73 m2 and albumin/creatinine ratios (ACR) of 115.0 (7.5–58.5) μg/mg. Urine ET-1 was inversely associated with eGFR (r = −0.480, P < 0.05) and positively (r = 0.407, P = 0.066) with ACR independent of age and female sex (P < 0.01). ET-1 appeared to be positively associated with total kidney volume (r = 0.426, P = 0.100), with a test for trend across urine ET-1 quartiles yielding z = 1.83, P = 0.068. ET-1 strongly correlated with NAGase (r = 0. 687, P = 0.001), a marker of tubular damage and a surrogate marker of renal disease progression in ADPKD. Of note, ET-1 levels in urine were not correlated with hypertension.ConclusionsIn a translational study of patients with ADPKD, urinary ET-1 was inversely associated with eGFR and positively correlated with total kidney volume. Taken together with results from experimental models, these findings suggest that the role of ET-1 in ADPKD warrants further investigation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0232-8) contains supplementary material, which is available to authorized users.

Fat Burning Problem in Cystic Kidneys: an Emerging Common Mechanism of Chronic Kidney Disease

Fat Burning Problem in Cystic Kidneys: an Emerging Common Mechanism of Chronic Kidney Disease

A mild reduction of food intake slows disease progression in an orthologous mouse model of polycystic kidney disease.

Autosomal-dominant polycystic kidney disease (ADPKD) is a common cause of end-stage renal disease, and no approved treatment is available in the United States to slow disease progression. The mammalian target of rapamycin (mTOR) signaling pathway is aberrantly activated in renal cysts, and while mTOR inhibitors are highly effective in rodent models, clinical trials in ADPKD have been disappointing due to dose-limiting extrarenal side effects. Since mTOR is known to be regulated by nutrients and cellular energy status, we hypothesized that dietary restriction may affect renal cyst growth. Here, we show that reduced food intake (RFI) by 23% profoundly affects polycystic kidneys in an orthologous mouse model of ADPKD with a mosaic conditional knockout of PKD1. This mild level of RFI does not affect normal body weight gain, cause malnutrition, or have any other apparent side effects. RFI substantially slows disease progression: relative kidney weight increase was 41 vs. 151% in controls, and proliferation of cyst-lining cells was 7.7 vs. 15.9% in controls. Mice on an RFI diet maintained kidney function and did not progress to end-stage renal disease. The two major branches of mTORC1 signaling, S6 and 4EBP1, are both suppressed in cyst-lining cells by RFI, suggesting that this dietary regimen may be more broadly effective than pharmacological mTOR inhibition with rapalogs, which primarily affects the S6 branch. These results indicate that polycystic kidneys are exquisitely sensitive to minor reductions in nutrient supply or energy status. This study suggests that a mild decrease in food intake represents a potential therapeutic intervention to slow disease progression in ADPKD patients.

MicroRNA-21 Aggravates Cyst Growth in a Model of Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD), one of the most common monogenetic disorders, is characterized by kidney failure caused by bilateral renal cyst growth. MicroRNAs (miRs) have been implicated in numerous diseases, but the role of these noncoding RNAs in ADPKD pathogenesis is still poorly defined. Here, we investigated the role of miR-21, an oncogenic miR, in kidney cyst growth. We found that transcriptional activation of miR-21 is a common feature of murine PKD. Furthermore, compared with renal tubules from kidney samples of normal controls, cysts in kidney samples from patients with ADPKD had increased levels of miR-21. cAMP signaling, a key pathogenic pathway in PKD, transactivated miR-21 promoter in kidney cells and promoted miR-21 expression in cystic kidneys of mice. Genetic deletion of miR-21 attenuated cyst burden, reduced kidney injury, and improved survival of an orthologous model of ADPKD. RNA sequencing analysis and additional in vivo assays showed that miR-21 inhibits apoptosis of cyst epithelial cells, likely through direct repression of its target gene programmed cell death 4 Thus, miR-21 functions downstream of the cAMP pathway and promotes disease progression in experimental PKD. Our results suggest that inhibiting miR-21 is a potential new therapeutic approach to slow cyst growth in PKD.

Food Restriction Ameliorates the Development of Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by the accumulation of kidney cysts that ultimately leads to loss of renal function and kidney failure. At present, the treatment for ADPKD is largely supportive. Multiple studies have focused on pharmacologic approaches to slow the development of the cystic disease; however, little is known about the role of nutrition and dietary manipulation in PKD. Here, we show that food restriction (FR) effectively slows the course of the disease in mouse models of ADPKD. Mild to moderate (10%-40%) FR reduced cyst area, renal fibrosis, inflammation, and injury in a dose-dependent manner. Molecular and biochemical studies in these mice indicate that FR ameliorates ADPKD through a mechanism involving suppression of the mammalian target of the rapamycin pathway and activation of the liver kinase B1/AMP-activated protein kinase pathway. Our data suggest that dietary interventions such as FR, or treatment that mimics the effects of such interventions, may be potential and novel preventive and therapeutic options for patients with ADPKD.

Opposing Effects of Inhibitors of Aurora-A and EGFR in Autosomal-Dominant Polycystic Kidney Disease.

Aurora-A kinase (AURKA) overexpression in numerous tumors induces aneuploidy, in part because of cytokinetic defects. Alisertib and other small-molecule inhibitors targeting AURKA are effective in some patients as monotherapies or combination therapies. Epidermal growth factor receptor (EGFR) pro-proliferative signaling activity is commonly elevated in cancer, and the EGFR inhibitor erlotinib is commonly used as a standard of care agent for cancer. An erlotinib/alisertib combination therapy is currently under assessment in clinical trials, following pre-clinical studies that indicated synergy of these drugs in cancer. We were interested in further exploring the activity of this drug combination. Beyond well-established functions for AURKA in mitotic progression, additional non-mitotic AURKA functions include control of ciliary stability and calcium signaling. Interestingly, alisertib exacerbates the disease phenotype in mouse models for autosomal-dominant polycystic kidney disease (ADPKD), a common inherited syndrome induced by aberrant signaling from PKD1 and PKD2, cilia-localized proteins that have calcium channel activity. EGFR is also more active in ADPKD, making erlotinib also of potential interest in this disease setting. In this study, we have explored the interaction of alisertib and erlotinib in an ADPKD model. These experiments indicated erlotinib-­restrained cystogenesis, opposing alisertib action. Erlotinib also interacted with alisertib to regulate proliferative signaling proteins, albeit in a complicated manner. Results suggest a nuanced role of AURKA signaling in different pathogenic conditions and inform the clinical use of AURKA inhibitors in cancer patients with comorbidities.

Human Polycystin-2 Transgene Dose-Dependently Rescues ADPKD Phenotypes in Pkd2 Mutant Mice

Although much is known about the molecular genetic mechanisms of autosomal-dominant polycystic kidney disease (ADPKD), few effective treatment is currently available. Here, we explore the invivo effects of causal gene replacement in orthologous gene models of ADPKD in mice. Wild-type mice with human PKD2 transgene (PKD2(tg)) overexpressed polycystin (PC)-2 in several tissues, including the kidney and liver, and showed no significant cyst formation in either organ. We cross-mated PKD2(tg) with a Pkd2-null mouse model, which is embryonically lethal and forms renal and pancreatic cysts. Pkd2(-/-) mice with human PKD2 transgene (Pkd2(-/-);PKD2(tg)) were born in expected Mendelian ratios, indicating that the embryonic lethality of the Pkd2(-/-) mice was rescued. Pkd2(-/-);PKD2(tg) mice survived up to 12 months and exhibited moderate to severe cystic phenotypes of the kidney, liver, and pancreas. Moreover, Pkd2(-/-) mice with homozygous PKD2(tg)-transgene alleles (Pkd2(-/-);PKD2(tg/tg)) showed significant further amelioration of the cystic severity compared to that in Pkd2(-/-) mice with a hemizygous PKD2(tg) allele (Pkd2(-/-);PKD2(tg)), suggesting that the ADPKD phenotype was improved by increased transgene dosage. On further analysis, cystic improvement mainly resulted from reduced proliferation, rather apoptosis, of cyst-prone epithelial cells in the mouse model. The finding that the functional restoration of human PC2 significantly rescued ADPKD phenotypes in a dose-dependent manner suggests that increasing PC2 activity may be beneficial in some forms of ADPKD.

Suppressing angiotensinogen synthesis attenuates kidney cyst formation in a Pkd1 mouse model.

Activation of the intrarenal renin angiotensin system (RAS) is believed to play an important role in the development of hypertension and cystogenesis in autosomal dominant polycystic kidney disease (ADPKD). Results of clinical studies testing RAS inhibitors in slowing the progression of cystic disease in ADPKD are inconclusive, and we hypothesized that current RAS inhibitors do not adequately suppress intrarenal RAS. For this study, we compared a novel Gen 2 antisense oligonucleotide (ASO) that inhibits angiotensinogen (Agt) synthesis to lisinopril in adult conditional Pkd1 systemic-knockout mice, a model of ADPKD. Six weeks after Pkd1 global gene knockout, the mice were treated with Agt-ASO (66 mg/kg/wk), lisinopril (100 mg/kg/d), PBS (control), or scrambled ASO (66 mg/kg/wk) for 10 wk, followed by tissue collection. Agt ASO resulted in significant reduction in plasma, liver, and kidney Agt, and increased kidney renin compared with control treatments. Kidneys from Agt-ASO-treated mice were not as enlarged and showed reduced cystic volume compared with lisinopril or control treatments. Blood pressure was better controlled with lisinopril than with Agt-ASO. Agt-ASO suppressed cell proliferation in both cystic and noncystic cells compared with lisinopril and control treatments. However, Agt-ASO did not reduce cell proliferation in liver, which indicates that Agt-ASO targets cell signaling pathways that specifically suppresses cystogenesis in the kidney. These data suggest that Agt-ASO effectively attenuates intrarenal RAS and therefore can be a novel and effective agent for treating ADPKD.

Utilizing magnetization transfer imaging to investigate tissue remodeling in a murine model of autosomal dominant polycystic kidney disease

PurposeNoninvasive imaging techniques that quantify renal tissue composition are needed to more accurately ascertain prognosis and monitor disease progression in polycystic kidney disease (PKD). Given the success of magnetization transfer (MT) imaging to characterize various tissue remodeling pathologies, it was tested on a murine model of autosomal dominant PKD.MethodsC57Bl/6 Pkd1 R3277C mice at 9, 12, and 15 months were imaged with a 16.4T MR imaging system. Images were acquired without and with RF saturation in order to calculate MT ratio (MTR) maps. Following imaging, the mice were euthanized and kidney sections were analyzed for cystic and fibrotic indices, which were compared with statistical parameters of the MTR maps.ResultsThe MTR‐derived mean, median, 25th percentile, skewness, and kurtosis were all closely related to indices of renal pathology, including kidney weight/body weight, cystic index, and percent of remaining parenchyma. The correlation between MTR and histology‐derived cystic and fibrotic changes was R2 = 0.84 and R2 = 0.70, respectively.ConclusionMT imaging provides a new, noninvasive means of measuring tissue remodeling PKD changes and may be better suited for characterizing renal impairment compared with conventional MR techniques. Magn Reson Med 75:1466–1473, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.

Macrophage migration inhibitory factor promotes cyst growth in polycystic kidney disease.

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 polycystin-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.

Urine Fetuin-A is a biomarker of autosomal dominant polycystic kidney disease progression.

BackgroundAutosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by numerous fluid-filled cysts that frequently result in end-stage renal disease. While promising treatment options are in advanced clinical development, early diagnosis and follow-up remain a major challenge. We therefore evaluated the diagnostic value of Fetuin-A as a new biomarker of ADPKD in human urine.ResultsWe found that renal Fetuin-A levels are upregulated in both Pkd1 and Bicc1 mouse models of ADPKD. Measurement by ELISA revealed that urinary Fetuin-A levels were significantly higher in 66 ADPKD patients (17.5 ± 12.5 μg/mmol creatinine) compared to 17 healthy volunteers (8.5 ± 3.8 μg/mmol creatinine) or 50 control patients with renal diseases of other causes (6.2 ± 2.9 μg/mmol creatinine). Receiver operating characteristics (ROC) analysis of urinary Fetuin-A levels for ADPKD rendered an optimum cut-off value of 12.2 μg/mmol creatinine, corresponding to 94% of sensitivity and 60% of specificity (area under the curve 0.74 ; p = 0.0019). Furthermore, urinary Fetuin-A levels in ADPKD patients correlated with the degree of renal insufficiency and showed a significant increase in patients with preserved renal function followed for two years.ConclusionsOur findings establish urinary Fetuin-A as a sensitive biomarker of the progression of ADPKD. Further studies are required to examine the pathogenic mechanisms of elevated renal and urinary Fetuin-A in ADPKD.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0463-7) contains supplementary material, which is available to authorized users.