Pathogenesis Of Cyst Formation Research Articles

Quantification of Urinary Protein Biomarkers of Autosomal Dominant Polycystic Kidney Disease by Parallel Reaction Monitoring.

Autosomal dominant polycystic kidney disease (ADPKD) is a life-long disease in which the genes responsible are known, but the pathogenesis of cyst formation and cyst growth are not understood. Cyst growth ultimately leads to end-stage renal failure in most patients. Analysis of the urinary proteome offers the potential to identify proteins that indicate the presence of cysts (and thus provides diagnosis) as well as the rates of cyst growth (providing prognostic information). A scheduled parallel reaction monitoring (sPRM) assay is performed on urine samples from 14 patients and 18 normal controls. For relative quantification, stable isotope-labeled synthetic peptides are spiked in the urinary protein digests prior to data collection. The data are subsequently normalized to creatinine and protein concentration in the respective urine samples to control for variations in water intake between individuals. Out of the 143 urinary proteins targeted for sPRM assay, 69 proteins are observed to be significantly dysregulated in ADPKD. The dysregulated proteins are used to cluster ADPKD patients into those who are more or less similar to normal controls. This study shows that sPRM is a promising approach to rapidly screen large numbers of proteins in urine in order to provide earlier diagnosis and potentially better understand the pathogenesis of ADPKD development and progression.

Identification of novel glycans with disialylated structures in α3 integrin from mouse kidney cells with the phenotype of polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder caused by mutations in the Pkd1 or Pkd2 genes, in which large cysts replace normal kidney tissue, leading to end-stage kidney disease. In this study we have utilized a powerful nano-HPLC-mass spectrometric approach to characterize patterns of normal and abnormal N-linked glycosylation of α3 integrin subunit in Pkd1(-/-) cells derived from mouse kidneys. Higher molecular weight glycan structures with a different monosaccharide composition were observed at two sites, namely, Asn-925 and Asn-928 sites in α3 integrin isolated from Pkd1(+/+) cells compared with Pkd1(-/-) cells. In addition, an unusual and unique disialic acid glycan structure was observed solely in Pkd1(-/-) cells. Thus, these studies suggest that abnormal protein glycosylation may have a role on the pathogenesis of cyst formation in ADPKD.

The ciliary flow sensor and polycystic kidney disease

Since the discovery that proteins mutated in different forms of polycystic kidney disease (PKD) are tightly associated with primary cilia, strong efforts have been made to define the role of this organelle in the pathogenesis of cyst formation. Cilia are filiform microtubular structures, anchored in the basal body and extending from the apical membrane into the tubular lumen. Early work established that cilia act as flow sensors, eliciting calcium transients in response to bending, which involve the two proteins mutated in autosomal dominant PKD (ADPKD), polycystin-1 and -2. Loss of cilia alone is insufficient to cause cyst formation. Nevertheless, a large body of evidence links flow sensing by cilia to aspects relevant for cyst formation such as cell polarity, Stat6- and mammalian target of rapamycin signalling. This review summarizes the current literature on cilia and flow sensing with respect to PKD and discusses how these findings intercalate with different aspects of cyst formation.

Calcimimetics inhibit renal pathology in rodent nephronophthisis

The development and progression of renal cysts appears to be driven by reduced cellular calcium and increased cyclic adenosine monophosphate (cAMP) from G-protein-coupled receptors. To test whether treatment with a calcimimetic that stimulates the G-protein-coupled calcium-sensing receptor might normalize cystic epithelial cell intracellular calcium and cAMP, thereby inhibiting cyst progression, we used pcy mice. These animals develop cysts principally in the collecting duct, as do humans with nephronophthisis (NPHP). We administered the calcimimetic R-568 mixed in their food at early or late stages in the pathogenesis of cyst formation. The treatment reduced cyst enlargement, and the early treatment inhibited development of renal fibrosis. Although the effect of later treatment was more modest, both stages of the disease responded positively to treatment. Additionally, R-568 decreased total kidney cAMP in the pcy mice and, in vitro, decreased cAMP levels and cell proliferation, while increasing intracellular calcium in immortalized human autosomal recessive polycystic kidney disease renal epithelial cells. The latter two effects were unique to R-568 and not replicated by raising extracellular calcium. Thus, treating pcy mice with R-568 was effective in reducing cyst progression in this rodent model of NPHP. Direct studies will be needed to determine whether these results can be applied to the human disease.

Association of IPMN with Other Non-pancreatic Cystic Lesions: Is it a Systemic Cystic Disorder?

Purpose: To compare the incidence of liver and kidney cysts among patients with IPMN to an age and sex matched control group. Methods: In this study, computer tomography (CT) scans of 40 patients with surgically proven pancreatic IPMN were reviewed for presence of liver and kidney cysts. A control group of 40 patients undergoing CT scan for indications other than suspected pancreatic disease during the same time period were used for comparison. The demographic characteristics were collected among both groups. The continuous variables were compared by student t test and categorical variables by Fisher's Exact test. Results: IPMN and control groups had no age or gender differences (Table 1). The prevalence of liver and kidney cysts in IPMN patients was 20% and 63%, respectively. There was no statistical difference compared to controls (P>0.05), although multi-organ cysts were common in both groups.Table 1Conclusion: Based on the results of this small case-control study, it does not appear that patients with IPMN have any increased association with cystic lesions of the liver and kidneys. The pathogenesis of cyst formation in solid organs is not well understood. However, the formation of mucinous cysts such as IPMN and non-mucinous liver and kidney cysts are likely unrelated. This study is limited by a small sample size, but the incidence of extra-pancreatic cysts will be followed through an ongoing international IPMN registry.

Advances in the pathogenesis and treatment of polycystic kidney disease

Polycystic kidney disease (PKD) is the most common genetic cause of chronic renal failure. Mouse models of PKD, especially those with mutations in genes that are orthologous to human disease genes, have provided insights into the pathogenesis of cyst formation and advanced the preclinical testing of new drugs. PKD is a ciliopathy that arises from abnormalities in the primary cilium, a sensory organelle present on the surface of most cells. The primary cilium is required for the maintenance of planar cell polarity, which regulates tubular diameter. Acute kidney injury stimulates cell proliferation and promotes cyst formation in a mouse model of PKD. Studies of signaling pathways that are perturbed in PKD have identified new potential therapeutic targets. Drugs that have shown beneficial effects in orthologous animal models of PKD include tolvaptan, octreotide, src inhibitors, CFTR inhibitors, pioglitazone, etanercept, and triptolide. Abnormalities in the primary cilium perturb signaling pathways that regulate renal epithelial cell growth and differentiation and lead to the formation of kidney cysts. Acute kidney injury promotes cyst formation and may underlie the variability in disease progression that is observed in affected individuals. Several promising new therapeutic agents that have been validated in orthologous animal models have entered clinical trials in humans.

Molecular pathogenesis of ADPKD and development of targeted therapeutic options

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disease characterized by formation and progressive enlargement of cysts in kidneys, liver and other organs, leading to end stage renal disease by the fifth decade [1]. Mutations in the PKD1 gene encoding polycystin-1 are responsible for 85% of ADPKD cases, while mutations in the PKD2 gene cause 15% of ADPKD cases with a less severe phenotype. Autosomal recessive polycystic kidney disease (ARPKD) affects newborns and results from mutations in the PKHD1 gene encoding fibrocystin [2]. Regardless of the genetic defect underlying PKD, cystic epithelia seem to display common abnormalities. Cellular mechanisms of cystogenesis have been studied for decades and suggest that cystic epithelia are characterized by a secretory phenotype with increased proliferation, apoptosis, loss of cellular differentiation and polarity. Considerable progress towards understanding the molecular pathogenesis of cyst formation has been made since the cloning of the PKD1 and PKD2 genes as well as other cystogenes responsible for multiple forms of PKD in animal models. Based on the enhanced understanding of the signalling pathways involved in cystogenesis, novel therapeutic approaches targeting mTOR activity, and cAMP activated signalling pathways are being tested in the clinic [3]. Also, recent studies highlight the importance of the primary cilium as a common trigger of cystic diseases [4]. The molecular link between cilia, mechanosensation and the cell cycle can now be explored for novel targeted therapeutic intervention in PKD. Here we focus on reviewing recent advances in understanding the molecular pathways of cystogenesis and therapeutic approaches to interfere with these pathways in preclinical and clinical trials.

Cystic vestibular schwannomas: a possible role of matrix metalloproteinase–2 in cyst development and unfavorable surgical outcome

The authors evaluated the clinical manifestations and surgical results in patients with cystic vestibular schwannoma (VS), and investigated the matrix metalloproteinase (MMP) expression of the cyst fluid and wall in an attempt to elucidate the pathogenesis and characteristics of this disease. The clinical and neuroimaging features, perioperative findings, and surgical outcomes in 24 cases of cystic VS and 82 cases of solid VS, all of which were treated using the suboccipital approach, were retrospectively compared. To evaluate the role of MMP in cystic VS, gelatin zymography and immunohistochemical studies of the cyst fluid, wall, and solid portion were performed in nine cases of this disease. The mean duration of symptoms was shorter (14.0 months compared with 26.1 months; p = 0.04) and the mean size of the tumor was larger (43.8 mm compared with 34.2 mm; p = 0.048) in the cystic than the solid VS group. Although gross-total resection was easier to accomplish in this group (100% compared with 84.1%), adhesion to the facial nerve was more frequent (62.5% compared with 48.8%; p = 0.042). On gelatin zymography studies, MMP-2 expression was ubiquitously observed in all cyst fluids. Immunohistochemical analysis of the cyst wall showed that MMP-2 was apparently localized to the tumor cells on the luminal inner surface, adjacent to the cyst cavity. Resection of cystic VS is complicated by severe adhesion of the tumor capsule to the facial nerve and the large size of the lesion. The authors believe that MMP-2 may be involved in the pathogenesis of cyst formation or in its enlargement and may aggravate adhesion to the facial nerve, either by promoting the enlargement of the tumor or engendering the degradation of the tumor-nerve barrier proteolytically.

VEGF receptor 2 blockade leads to renal cyst formation in mice

Polycystic kidney disease (PKD) is associated with mutations in PKD1 and PKD2 and vascular abnormalities. The links between the epithelial and vascular defects, however, are poorly understood. Vascular endothelial growth factor (VEGF) has been shown to be critical for normal kidney development. In animal models, blockade of VEGF in the perinatal period can lead to abnormal glomerular development, impaired nephrogenesis, proteinuria, and renal failure. We hypothesized that brief blockade of VEGF signaling during early postnatal kidney development can lead to renal cyst development. On days 2 and 4 of life, CD-1 mice were treated with antibodies generated against the extracellular portion of the VEGF receptor 2 (DC101), the area of the receptor where VEGF binding occurs. Mice developed renal cysts between 2 and 3 weeks. The DC101-treated mice also had increased cell proliferation in the renal tubule epithelium. In addition, mice receiving DC101 developed abnormal glomeruli, proteinuria, and patchy cellular infiltrates. Early disruption of VEGFR-2 signaling during the perinatal period results in renal cyst formation, impaired glomerulogenesis, and inflammation. VEGF could be a key link between vascular and cystic changes in kidney cyst formation.

Announcement

ANNOUNCEMENTSAnnouncementPublished Online:01 Apr 2006https://doi.org/10.1152/ajprenal.00005.2006MoreSectionsPDF (40 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Dr. Peter Igarashi has been named the 2006 Carl W. Gottschalk Distinguished Lecturer of the American Physiological Society (APS) Renal Section. Dr. Igarashi will deliver the lecture, entitled “Transcriptional mechanisms of renal cystogenesis,” on Sunday, April 2, 2006, during the Experimental Biology Meeting in San Francisco, California. Dr. Igarashi will also be honored during the Renal Dinner on Tuesday, April 4, 2006.Dr. Igarashi received his B.S. degree with Highest Honors from the University of California, Riverside, in 1978. He attended medical school at the University of California, Los Angeles, earning the M.D. degree in 1981. After internship and residency training in Internal Medicine at the University of California, Davis Medical Center, he completed a nephrology fellowship at Yale University School of Medicine (1984–1987). During this period, he received research training in the laboratory of Dr. Peter S. Aronson. Dr. Igarashi accepted a faculty position as Assistant Professor of Medicine at the Yale University School of Medicine in 1987 and was promoted to Associate Professor in 1992. He moved to the University of Texas Southwestern Medical Center in 1999 as Professor in the Department of Internal Medicine and Chief of the Division of Nephrology. In 2000, he was named the Robert Tucker Hayes Distinguished Chair in Nephrology, in Honor of Dr. Floyd C. Rector, Jr. He has published more that 45 peer-reviewed manuscripts, 5 book chapters, and 9 review articles. Dr. Igarashi has served on several study sections, advisory committees, and editorial boards, including the American Journal of Physiology-Renal Physiology, and he is currently Associate Editor of the Journal of the American Society of Nephrology.Dr. Igarashi's research focuses on kidney development, kidney-specific gene regulation, and polycystic kidney disease. He has been working to define the genetic pathways that regulate normal kidney development and to identify alterations in the pathways that are responsible for cyst formation in polycystic kidney disease. In particular, his studies are probing the roles of hepatocyte nuclear factor-1β and renal cilia in the pathogenesis of cyst formation. This work uses a combination of biochemical and genetic approaches in transgenic, knockout, and conditional knockout mice to identify and characterize the transcription factors that regulate clinically relevant genes.The APS Renal Section's Distinguished Lectureship Committee was composed of Pamela K. Carmines (Renal Section Chair), P. Darwin Bell (Renal Section representative to the APS Joint Program Committee), Jeff M. Sands (Editor, American Journal of Physiology-Renal Physiology), and Douglas C. Eaton (APS President). Download figureDownload PowerPointThis article has no references to display. Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 290Issue 4April 2006Pages F946-F946 Copyright & PermissionsCopyright © 2006 the American Physiological Societyhttps://doi.org/10.1152/ajprenal.00005.2006History Published online 1 April 2006 Published in print 1 April 2006 Metrics Downloaded 61 times

Epidermal growth factor receptor tyrosine kinase inhibition is not protective in PCK rats

Advances in the understanding of cystogenesis, identification of the PKHD1 gene and availability of a rat model (the PCK rat) caused by a Pkhd1 mutation facilitate testing of therapies for autosomal-recessive polycystic kidney disease (ARPKD). Considerable support exists for the importance of the epidermal growth factor (EGF)/transforming growth factor-alpha (TGF-alpha)/EGF receptor (EGFR) axis and of the adenylyl cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) pathway in the pathogenesis of cyst formation and progressive enlargement. To determine whether EGFR tyrosine kinase inhibition is protective in the PCK rat, male and female animals were treated with EKI-785 or EKB-569 or with vehicle alone between 3 and 10 weeks of age. Biochemical and histomorphometric analysis, immunohistochemistry, immunoblotting, enzyme immunoassay, and quantitative reverse transcription-polymerase chain reaction (RT-PCR) were used to ascertain the effects of treatment. Contrary to other murine models of ARPKD, overexpression and apical mislocalization of EGFR were not detected in the PCK rats. Consistent with these expression results, EKI-785 or EKB-569 administration had no effect or worsened PKD, and had no effect on the development of fibrocystic liver disease. Increased renal cAMP and vasopressin V2 receptor expression were observed in the EKI-785-treated animals. EGFR tyrosine kinase inhibition did not protect PCK rats from the development of PKD. This may be due to effects on collecting duct cAMP that counteract possible beneficial effects on the extracellular-regulated protein kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway, particularly in the absence of EGFR overexpression or mislocalization. The relevance of these observations to the treatment of human cystic kidney diseases deserves further study.

Polycystins, calcium signaling, and human diseases

Autosomal dominant polycystic kidney disease (ADPKD) is a major, inherited nephropathy affecting over 1:1000 of the worldwide population. It is a systemic condition with frequent hepatic and cardiovascular manifestations in addition to the progressive development of fluid-filled cysts from the tubules and collecting ducts of affected kidneys. The pathogenesis of cyst formation is currently thought to involve increased proliferation of epithelial cells, mild dedifferentiation, and fluid accumulation. In the past decade, study of ADPKD led to the discovery of a unique family of highly complex proteins, the polycystins. Loss-of-function mutations in either of two polycystin proteins, polycystin-1 or polycystin-2, give rise to ADPKD. These proteins are thought to function together as part of a multiprotein complex that may initiate Ca 2+ signals, directing attention to the regulation of intracellular Ca 2+ as a possible misstep that participates in cyst formation. Here we review what is known about the Ca 2+ signaling functions of polycystin proteins and focus on findings that have significantly advanced our physiological insight. Special attention is paid to the recently discovered role of these proteins in the mechanotransduction of the renal primary cilium and the model it suggests.

The genetics and physiology of polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a major, inherited disorder that is characterized by the growth of large, fluid-filled cysts from the tubules and collecting ducts of affected kidneys, and by a number of extrarenal manifestations including liver and pancreatic cysts, hypertension, heart valve defects, and cerebral and aortic aneurysms. Mutations in either of 2 different genes (PKD1 or PKD2) give rise to ADPKD. Most mutations identified in affected families appear to inactivate the PKD genes, and accumulating evidence suggests that a 2-hit mechanism, in which the normal PKD1 or PKD2 allele is also mutated, may be required for cyst growth. The protein products of the PKD genes (polycystin-1 and polycystin-2) are thought to function together as part of a multiprotein membrane-spanning complex involved in cell-cell or cell-matrix interactions. Polycystin-1 and polycystin-2 can initiate signal transduction, leading to the activation of a number of downstream effectors, including heterotrimeric G-proteins, protein kinase C, mitogen-activated protein kinases, beta-catenin, and the AP-1 transcription factor. In addition, polycystin-2 may function in mediating calcium flux. The pathogenesis of cyst formation is currently thought to involve increased cell proliferation, fluid accumulation, and basement membrane remodeling. It now appears that cyclic adenosine monophosphate (cAMP) metabolism is a central component of cyst formation, stimulating apical chloride secretion and driving the accumulation of cyst fluid. Recent evidence has shown that ADPKD cells also have an altered responsiveness to cyclic AMP. In contrast to normal kidney cells whose cell proliferation is inhibited by cyclic AMP, ADPKD cells are stimulated to proliferate. Thus, it is likely that an alteration in polycystin function transforms the normal cellular phenotype to one that responds to elevated cyclic AMP by an increased rate of cell proliferation and that the enlarging cyst expands by an increased rate of cyclic AMP-driven fluid secretion. Cyclic AMP and growth factors, including epidermal growth factor, have complementary effects to accelerate the enlargement of ADPKD cysts, and thereby to contribute to the progression of the disease. This knowledge should facilitate the discovery of inhibitors of signal transduction cascades that can be used in the treatment of ADPKD.

An ever-expanding story of cyst formation.

Autosomal-dominant polycystic kidney disease represents one of the most common monogenetic human disorders. The cloning of the PKD1 and PKD2 genes, which are mutated in far more than 90% of the patients affected by this disease, has generated high hopes for a quick understanding of the pathogenesis of cyst formation. However, these expectations have not yet been fulfilled, since the function of both polycystin-1 and polycystin-2, the two proteins encoded by PKD1 and PKD2, still remains a puzzle. In this review, we will highlight some of the characteristics of polycystic kidney disease, briefly touch on polycystin-1, and then go on to describe recent results of experiments with polycystin-2, since the latter is the major focus of our work. We will discuss new evidence which suggests that autosomal-dominant polycystic kidney disease actually behaves recessively on a cellular level. Finally, a model will be presented that tries to explain the available data.

Analysis of fluid in cysts accompanying various primary and metastatic brain tumours: proteins, lactate and pH.

There is a growing interest in cystic lesions of the brain. By examining the cyst content of brain tumours more insight into the pathogenesis of cyst formation has been found. In this study, 39 samples of cyst fluid of 34 patients with a cyst accompanying a brain tumour were collected and studied biochemically regarding their protein content, lactate and pH. In this study we investigated the relation between the grade of malignancy and the lactate-concentration and the discrepancy between the high levels of lactate in cysts and their alkaline environment. The results of the measurements of the concentrations of albumin, immunoglobulines (IgG, IgA, IgM) and alpha 2-macroglobulin in cysts compared to those in sera suggest that cyst formation associated with tumour is based upon a disruption of the blood-brain barrier with exudation of plasma proteins into the brain parenchyma resulting in accumulation of fluid (oedema) and eventually in formation of a cyst. There appears to be a positive relation between the grade of malignancy and the concentration of lactate in the cysts with a significant 2-fold increase in lactate concentration in malignant tumour cysts compared to the more benign tumour cysts (p < 0.001) probably on account of aerobic glycolysis with production of lactate by the tumour. The measured pH values in the cysts were above normal, resulting in a discrepancy of the high levels of lactate in the cyst with the alkaline environment and this suggests efflux of H(+)-ions by a Na/H exchange mechanism to compensate for the change of pH.

A role for Na/K adenosine triphosphatase in the pathogenesis of cyst formation in experimental polycystic kidney disease

Multiple cyst formation with fluid retention is a characteristic structural abnormality in polycystic kidney disease (PKD). Na/K adenosine triphosphatase (ATPase) is a major transporting membrane protein that is ubiquitous in the epithelial cell, which has been thought to be involved in cystogenesis. We have investigated the molecular and histologic basis of Na/K ATPase activity in experimental PKD in vivo. Rats were treated with diphenylthiazole (100 mg/100 gm body weight), and cyst formation was examined histologically. Na/K ATPase activity was measured enzymatically by using a fluorometric method, and reverse transcription-competitive polymerase chain reaction (RT-PCR) analysis was used to quantitate mRNA levels in the isolated single nephron segment. Kidneys were immunostained with subunit-specific antibodies to determine the localization of Na/K ATPase in the epithelial cell. The enzyme activity increased in the cortical collecting duct from 25.9 ± 3.5 mmol/Lpmol/mm/min to 72.9 ± 6.8 pmol/mm/min and in the outer medullary collecting duct from 13.0 ± 3.9 mmol/Lpmol/mm/min to 58.5 ± 9.8 pmol/mm/min (n = 6, p < 0.01); however, all other segments showed no significant changes. No significant alternation in α1- and β1-subunits of Na/K ATPase mRNA levels was observed by competitive PCR assay in either segment. The enzyme was stained at the basolateral membrane even in the cystic tubules. Na/K ATPase activity was up-regulated in the cyst-formed kidney, but this was not accompanied with transcriptional up-regulation. Increased Na/K ATPase activity at normal locations may play a role in abnormal net fluid transport in the development and progression of experimental PKD.

Cystic Degeneration and Carcinogenesis of the Kidney

Multiple theories concerning the pathogenesis of cyst formation in the kidney have been proposed, each waxing and waning in popularity over the past four centuries. Electron microscopy and microdissection techniques provided great progress as diagnostic tools in examining renal cystogenesis and further insight into cystogenesis has recently been brought about by more sophisticated techniques including cell biology and molecular genetics. My scientific interest in renal cysts was kindled about two decades ago by the appearance of a book edited by E.L. Potter entitled Normal and Abnormal Development of the Kidney in which she classified the pathogenesis of cystic kidneys into four types. I The purpose of this article is to highlight areas of research in renal cystogenesis including its association with carcinogenesis.

Cystic Meningioma

Cystic meningiomas are rare. The authors presented a case of cystic meningioma in the right frontal convexity of a 36-year-old female. The patient was admitted because of progressive headache, foggy sight, diplopia, and left-sided motor weakness of two months' duration. The preoperative diagnosis of cystic meningioma was made by plain skull X-rays, CT scans, and cerebral arteriograms. At surgery, a tumor was found adherent to the dura in the right frontal convexity with multiloculated intratumoral cysts containing xanthochromic fluid. Histologically, the tumor was a transitional meningioma with intratumoral infarction in the vicinity of the cysts. The pathogenesis of the intratumoral cysts in this particular case were considered intratumoral infarction resulting in microcysts and then finally macrocysts. Ninety-six cases of cystic meningiomas reported in the literature were reviewed and the pathogenesis of cyst formation was discussed. Nauta's classification of four types of cystic meningiomas is important when considering the different pathogenesis of cyst formation in meningiomas. Adding to the four types of cystic meningiomas classified by Nauta et al., the authors suggested another type, namely, the subdural cyst mainly seen in infant meningiomas.