Murine Polycystic Kidney Disease Research Articles

Targeting of Receptor for Advanced Glycation End Products Suppresses Cyst Growth in Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disorder. Although a myriad of research groups have attempted to identify a new therapeutic target for ADPKD, no drug has worked well in clinical trials. Our research group has focused on the receptor for advanced glycation end products (RAGE) gene as a novel target for ADPKD. This gene is involved in inflammation and cell proliferation. We have already confirmed that blocking RAGE function attenuates cyst growth in vitro. Based on this previous investigation, our group examined the effect of RAGE on cyst enlargement in vivo. PC2R mice, a severe ADPKD mouse model that we generated, were utilized. An adenovirus containing anti-RAGE shRNA was injected intravenously into this model. We observed that RAGE gene knockdown resulted in loss of kidney weight and volume. Additionally, the cystic area that originated from different nephron segments decreased in size because of down-regulation of the RAGE gene. Blood urea nitrogen and creatinine values tended to be lower after inhibiting RAGE. Based on these results, we confirmed that the RAGE gene could be an effective target for ADPKD treatment.

Pkd2 mesenteric vessels exhibit a primary defect in endothelium-dependent vasodilatation restored by rosiglitazone

Patients with autosomal dominant polycystic kidney disease have a high prevalence of hypertension and structural vascular abnormalities, such as intracranial aneurysms. Hypertension can develop in childhood and often precedes a significant reduction in the glomerular filtration rate. The major aim of this study was to investigate whether a primary endothelial defect or a vascular smooth muscle (VSM) defect was present in murine polycystic kidney disease (Pkd)2 heterozygous mesenteric vessels before the development of renal failure or hypertension. Using pressure myography, we observed a marked defect in ACh-stimulated endothelium-dependent vasodilatation in Pkd2 arterioles. In contrast, Pkd2 vessels responded normally to sodium nitroprusside, phenylephrine, KCl, and pressure, indicating unaltered VSM-dependent responses. Pretreatment with the peroxisome proliferator-activated receptor-γ agonist rosiglitazone significantly restored ACh-dependent vasodilation in Pkd2 mice. Isolated heterozygous Pkd2 endothelial cells displayed normal ACh-stimulated Ca(2+) and nitric oxide production. However, isolated Pkd2 heterozygous VSM cells displayed basal increases in superoxide and sodium nitroprusside-stimulated peroxynitrite formation, which were both suppressed by rosiglitazone. Furthermore, we observed a defective response of Pkd2 mesenteric venules to ACh in vivo, which was more marked after ischemia-reperfusion injury. In conclusion, the results of our study suggest that the defect in vasodilatation in Pkd2 heterozygous vessels is primarily due to a reduction in nitric bioavailability secondary to increased vascular oxidative stress. The ability of rosiglitazone to correct this phenotype suggests that this defect is potentially reversible in patients with autosomal dominant polycystic kidney disease.

Genotype–phenotype correlations in fetuses and neonates with autosomal recessive polycystic kidney disease

The prognosis of autosomal recessive polycystic kidney disease is known to correlate with genotype. The presence of two truncating mutations in the PKHD1 gene encoding the fibrocystin protein is associated with neonatal death while patients who survive have at least one missense mutation. To determine relationships between genotype and renal and hepatic abnormalities we correlated the severity of renal and hepatic histological lesions to the type of PKHD1 mutations in 54 fetuses (medical pregnancy termination) and 20 neonates who died shortly after birth. Within this cohort, 55.5% of the mutations truncated fibrocystin. The severity of cortical collecting duct dilatations, cortical tubule and glomerular lesions, and renal cortical and hepatic portal fibrosis increased with gestational age. Severe genotypes, defined by two truncating mutations, were more frequent in patients of less than 30 weeks gestation compared to older fetuses and neonates. When adjusted to gestational age, the extension of collecting duct dilatation into the cortex and cortical tubule lesions, but not portal fibrosis, was more prevalent in patients with severe than in those with a non-severe genotype. Our results show the presence of two truncating mutations of the PKHD1 gene is associated with the most severe renal forms of prenatally detected autosomal recessive polycystic kidney disease. Their absence, however, does not guarantee survival to the neonatal period.

Long-lasting arrest of murine polycystic kidney disease with CDK inhibitor roscovitine

Long-lasting arrest of murine polycystic kidney disease with CDK inhibitor roscovitine

Roscovitine Prevents TCR-Mediated T Cell Clonal Expansion In-Vitro and Protects Against GvHD In-Vivo.

Cell cycle re-entry of quiescent T lymphocytes is required for generation of productive T cell responses. Cyclin-dependent kinases (cdk), particularly cdk2, have an essential role in cell cycle re-entry. Cdk2 promotes phosphorylation of Rb and related pocket proteins thereby reversing their ability to sequester E2F transcription factors. Besides Rb, cdk2 phosphorylates Smad2 and Smad3. Smad3 inhibits cell cycle progression from G1 to S phase, and impaired phosphorylation on the cdk-mediated sites renders it more effective in executing this function. In contrast, cdk-mediated phosphorylation of Smad3 reduces Smad3 transcriptional activity and antiproliferative function. Recently, we determined that induction of T cell tolerance resulted in impaired cdk2 activity, leading to reduced levels of Smad3 phosphorylation on cdk-specific sites and increased Smad3 antiproliferative function due to upregulation of p15. We hypothesized that pharmacologic inhibition of cdk2 during antigen-mediated T cell stimulation might provide an effective strategy to control T cell expansion and induce tolerance. (R)-roscovitine (CYC202) is a potent inhibitor of cdk2-cyclin E, which in higher concentrations also inhibits other cdk-cyclin complexes including cdk7, cdk9 and cdk5. It is currently in clinical trials as anticancer drug and recently was shown to induce long-lasting arrest of murine polycystic kidney disease. We examined the effect of roscovitine on T cell responses in vitro and in vivo. We stimulated C57BL/6 T cells with anti-CD3-plus-anti-CD28 mAbs, DO11.10 TCR-transgenic T cells with OVA peptide or C57BL/6 T cells with MHC disparate Balb/c splenocytes. Addition of roscovitine in these cultures resulted in blockade of cell proliferation without induction of apoptosis. Biochemical analysis revealed that roscovitine prevented phosphorylation of cdk2, downregulation of p27, phosphorylation of Rb and synthesis of cyclin A, suggesting an effective G1/S cell cycle block. To determine whether roscovitine could also inhibit clonal expansion of activated T cells in vivo, we employed a mouse model of GvHD. Recipient (C57BL/6 x DBA/2) F1 mice were lethally irradiated and were subsequently infused with bone marrow cells and splenocytes, as source of allogeneic T cells, from parental C57BL/6 donors. Roscovitine or vehicle-control was given at the time of allogeneic BMT and on a trice-weekly basis thereafter for a total of three weeks. Administration of roscovitine protected against acute GvHD resulting in a median survival of 49 days in the roscovitine-treated group compared to 24 days in the control group (p=0.005), and significantly less weight loss. Importantly, roscovitine treatment had no adverse effects on engraftment, resulting in full donor chimerism in the treated mice. To examine whether tolerance had been induced by in vivo treatment with roscovitine, we examined in vitro rechallenge responses. While control C57BL/6 T cells exhibited robust responses when stimulated with (C57BL/6 x DBA/2) F1 splenocytes, responses of T cells isolated from roscovitine-treated recipients against (C57BL/6 x DBA/2) F1 splenocytes were abrogated. These results indicate that roscovitine has direct effects on preventing TCR-mediated clonal expansion in vitro and in vivo and may provide a novel therapeutic approach for control of GvHD.

Long-lasting arrest of murine polycystic kidney disease with CDK inhibitor roscovitine

Polycystic kidney diseases (PKDs) are primarily characterized by the growth of fluid-filled cysts in renal tubules leading to end-stage renal disease. Mutations in the PKD1 or PKD2 genes lead to autosomal dominant PKD (ADPKD), a slowly developing adult form. Autosomal recessive polycystic kidney disease results from mutations in the PKHD1 gene, affects newborn infants and progresses very rapidly. No effective treatment is currently available for PKD. A previously unrecognized site of subcellular localization was recently discovered for all proteins known to be disrupted in PKD: primary cilia. Because ciliary functions seem to be involved in cell cycle regulation, disruption of proteins associated with cilia or centrioles may directly affect the cell cycle and proliferation, resulting in cystic disease. We therefore reasoned that the dysregulated cell cycle may be the most proximal cause of cystogenesis, and that intervention targeted at this point could provide significant therapeutic benefit for PKD. Here we show that treatment with the cyclin-dependent kinase (CDK) inhibitor (R)-roscovitine does indeed yield effective arrest of cystic disease in jck and cpk mouse models of PKD. Continuous daily administration of the drug is not required to achieve efficacy; pulse treatment provides a robust, long-lasting effect, indicating potential clinical benefits for a lifelong therapy. Molecular studies of the mechanism of action reveal effective cell-cycle arrest, transcriptional inhibition and attenuation of apoptosis. We found that roscovitine is active against cysts originating from different parts of the nephron, a desirable feature for the treatment of ADPKD, in which cysts form in multiple nephron segments. Our results indicate that inhibition of CDK is a new and effective approach to the treatment of PKD.

Heightened epithelial Na+ channel-mediated Na+ absorption in a murine polycystic kidney disease model epithelium lacking apical monocilia

The Tg737 degrees (rpk) autosomal recessive polycystic kidney disease (ARPKD) mouse carries a hypomorphic mutation in the Tg737 gene. Because of the absence of its protein product Polaris, the nonmotile primary monocilium central to the luminal membrane of ductal epithelia, such as the cortical collecting duct (CCD) principal cell (PC), is malformed. Although the functions of the renal monocilium remain elusive, primary monocilia or flagella on neurons act as sensory organelles. Thus we hypothesized that the PC monocilium functions as a cellular sensor. To test this hypothesis, we assessed the contribution of Polaris and cilium structure and function to renal epithelial ion transport electrophysiology. Properties of Tg737 degrees (rpk) mutant CCD PC clones were compared with clones genetically rescued with wild-type Tg737 cDNA. All cells were grown as polarized cell monolayers with similarly high transepithelial resistance on permeable filter supports. Three- to fourfold elevated transepithelial voltage (V(te)) and short-circuit current (I(sc)) were measured in mutant orpk monolayers vs. rescued controls. Pharmacological and cell biological examination of this enhanced electrical end point in mutant monolayers revealed that epithelial Na(+) channels (ENaCs) were upregulated. Amiloride, ENaC-selective amiloride analogs (benzamil and phenamil), and protease inhibitors (aprotinin and leupeptin) attenuated heightened V(te) and I(sc). Higher concentrations of additional amiloride analogs (ethylisopropylamiloride and dimethylamiloride) also revealed inhibition of V(te). Cell culture requirements and manipulations were also consistent with heightened ENaC expression and function. Together, these data suggest that ENaC expression and/or function are upregulated in the luminal membrane of mutant, cilium-deficient orpk CCD PC monolayers vs. cilium-competent controls. When the genetic lesion causes loss or malformation of the monocilium, ENaC-driven Na(+) hyperabsorption may explain the rapid emergence of severe hypertension in a majority of patients with ARPKD.

Transforming Growth Factor Alpha (TGF-α) and Other Targets of Tumor Necrosis Factor-Alpha Converting Enzyme (TACE) in Murine Polycystic Kidney Disease

Transforming growth factor-alpha (TGF-alpha) is abnormally expressed in autosomal recessive polycystic kidney disease (ARPKD). Tumor necrosis factor-alpha converting enzyme (TACE), a metalloproteinase, mediates TGF-alpha processing. In this study, we sought to determine whether TGF-alpha was an absolute requirement for renal cystogenesis and whether its absence would modulate disease severity or related growth factors/receptors expression. Bpk heterozygotes were bred with TGF-alpha null mice to produce cystic and noncystic offspring with or without TGF-alpha. Assessments included kidney weight (KW), body weight (BW), blood urea nitrogen (BUN), and kidney and liver immunohistology. Western analysis assessed kidney expression of amphiregulin (AR), epidermal growth factor (EGF), heparin-binding EGF (HB-EGF), and their receptors, EGFR and ErbB4. A PCR-based methodology for genotyping bpk mice was also developed. No significant differences in KW, BW, KW/BW%, or BUN were seen in cystic mice with versus without TGF-alpha. Cystic kidney disease and liver disease histology were similar. AR, EGF, HB-EGF, EGFR, and ErbB4 were abnormally expressed to an equal degree in kidneys of mice with versus without TGF-alpha. Although previous data suggest a critical role of TGF-alpha in murine PKD, these data show that TGF-alpha is not required for renal cyst formation or kidney or liver disease progression. We speculate that the therapeutic effect of WTACE2 could have been due to effects on several TACE targets, including TGF-alpha, AR, and ErbB4, as well as metalloproteinases other than TACE.

Matrilysin (MMP-7) expression in renal tubular damage: Association with Wnt4

Matrilysin, a secreted matrix metalloproteinase and target gene of Wnt signaling, functions in epithelial repair and host defense, but no role in renal injury has been described. Matrilysin expression was assessed in human kidney specimens by immunohistochemistry, and in experimental renal injury in mice by immunohistochemistry, Northern blotting, and RNase protection assays (RPA). A relationship to Wnt4, which is also induced in renal injury, was determined by RPA and in situ hybridization. Matrilysin was not detected in the normal human renal tubular epithelium by immunohistochemistry. However, prominent staining was detected in sections from autosomal-dominant polycystic kidney disease in the cyst lining epithelium, atrophic tubules, and cyst micropolyps, and from hydronephrosis in dilated and atrophic tubules. Matrilysin expression was also induced by acute folic acid nephropathy and unilateral ureteral obstruction (UUO) in the mouse, and expression increased as acute injury progressed to tubulointerstitial fibrosis. Matrilysin staining was primarily localized to epithelium of distal tubule/collecting duct origin in both human and murine renal disease. Wnt signaling can induce matrilysin expression, and we found that the pattern of matrilysin expression during progression of renal fibrosis in the mouse after UUO or folic acid nephropathy, and in the jck model of murine polycystic kidney disease, closely paralleled that of Wnt4. These observations suggest that matrilysin may have a role in renal tubular injury and progression of tubulointerstitial fibrosis, and that Wnt4 may regulate matrilysin expression in the kidney.

Murine models of polycystic kidney disease: molecular and therapeutic insights

Numerous murine (mouse and rat) models of polycystic kidney disease (PKD) have been described in which the mutant phenotype results from a spontaneous mutation or engineering via chemical mutagenesis, transgenic technologies, or gene-specific targeting in mouse orthologs of human PKD genes. These murine phenotypes closely resemble human PKD, with common abnormalities observed in tubular epithelia, the interstitial compartment, and the extracellular matrix of cystic kidneys. In both human and murine PKD, genetic background appears to modulate the renal cystic phenotype. In murine models, these putative modifying effects have been dissected into discrete factors called quantitative trait loci and genetically mapped. Several lines of experimental evidence support the hypothesis that PKD genes and their modifiers may define pathways involved in cystogenesis and PKD progression. Among the various pathway abnormalities described in murine PKD, recent provocative data indicate that structural and/or functional defects in the primary apical cilia of tubular epithelia may play a key role in PKD pathogenesis. This review describes the most widely studied murine models; highlights the data regarding specific gene defects and genetic modifiers; summarizes the data from these models that have advanced our understanding of PKD pathogenesis; and examines the effect of various therapeutic interventions in murine PKD.

Kidney injury molecule-1 expression in murine polycystic kidney disease.

Kidney injury molecule-1 (Kim-1) is a type 1 membrane protein maximally upregulated in proliferating and dedifferentiated tubular cells after renal ischemia. Because epithelial dedifferentiation, proliferation, and local ischemia may play a role in the pathophysiology of autosomal dominant polycystic kidney disease, we investigated Kim-1 expression in a mouse model of this disease. In the Pkd2(WS25/-) mouse model for autosomal dominant polycystic kidney disease, cystic kidneys show markedly upregulated Kim-1 levels compared with noncystic control kidneys. Kim-1 is present in a subset of cysts of different sizes and segmental origins and in clusters of proximal tubules near cysts. Kim-1-expressing tubular cells show decreased complexity and quantity of basolateral staining for Na-K-ATPase. Other changes in polarity characteristic of ischemic injury are not present in Kim-1-expressing pericystic tubules. Polycystin-2 expression is preserved in Kim-1-expressing tubules. The interstitium surrounding Kim-1-expressing tubules shows high proliferative activity and staining for smooth muscle alpha-actin, characteristic of myofibroblasts. Although the functional role of the protein in cysts remains unknown, Kim-1 expression in tubules is strongly associated with partial dedifferentiation of epithelial cells and may play a role in the development of interstitial fibrosis.

C-myc antisense oligonucleotide treatment ameliorates murine ARPKD

Overexpression of c-myc is postulated to play a role in the pathogenesis of polycystic kidney disease (PKD). c-myc expression is increased in all rodent models of PKD that have been examined as well as in human ADPKD. To determine whether overexpression of renal c-myc contributes to renal cyst formation, C57BL/6J-cpk litters (an animal model of ARPKD) were treated with an antisense oligomer (ASO) to c-myc mRNA. Injections of 30 microg of a c-myc ASO were given to C57BL/6J-cpk litters on postnatal days 7-20. Control mice received either sham injections or injections of an equal amount of a scrambled ASO. At 20 days, kidney weight, body weight, serum urea nitrogen (SUN), hematocrit, and renal concentration of ASO were determined. In kidney, c-Myc and PCNA protein were assessed by immunoblotting and steady state levels of renal RNA for c-myc, EGF, SGP-2, and histone H4 were assessed by northern blot hybridization. c-Myc and PCNA proteins were localized by immunohistochemistry. Cystic mice treated with the c-myc ASO had a decreased relative kidney weight, improved renal function, and a reduced amount of cystic change compared with sham and scrambled ASO controls. The abnormal expression of several PKD related proteins and mRNAs were partially reversed by c-myc antisense treatment. c-myc staining appeared to be reduced in the noncystic tubules. Treatment with the c-myc ASO did not cause a reduction in hematocrit or total body weight indicating that the beneficial effects were not due to a generalized inhibition of cell proliferation in rapidly growing tissue. c-Myc appears to play a role in the cystogenesis of cpk-induced murine PKD and antisense targeting the overexpression of c-myc partially ameliorated the renal changes.

Progressive renal fibrosis in murine polycystic kidney disease: An immunohistochemical observation

The appearance of interstitial fibrosis in polycystic kidneys is emblematic of progressive disease. Matrix forming this scar tissue is derived from local renal cells in response to cystogenesis. We investigated the phenotype of collagen-producing cells in the cystic kidneys of DBA/2-pcy mice to better characterize the spectrum of interstitial cells associated with renal fibrogenesis. The extent of interstitial fibrosis and the number of fibroblasts in cystic kidneys were first quantitated over time using computer-assisted image analysis. Subsequently, antisera to four cell protein markers were studied by coexpression immunohistochemistry during progression of fibrosis using confocal microscopy. The antisera included fibroblast-specific protein 1 (FSP1) for fibroblast phenotype, alpha-smooth muscle actin (alpha-SMA) for contractile phenotype, vimentin (VIM) for mesenchymal phenotype, and heat shock protein 47 (HSP47) for interstitial collagen-producing phenotype. Interstitial fibrosis in cystic kidneys gradually increased throughout the 30-week observation period of our study. With progression of cystogenesis, most of the tubules in pcy mice either dilated or disappeared with time. FSP1+ fibroblasts were distributed sparsely throughout the renal interstitium of young pcy and wild-type mice. Their number increased in the widening fibrotic septa by 18 weeks of age and persisted through 30 weeks of the study interval. Some epithelia among remnant tubules trapped within fibrotic septa around adjacent cysts also acquired the phenotype of FSP1+, HSP47+ collagen-producing fibroblasts, suggesting a possible role for epithelial-mesenchymal transformation (EMT) in this process. Most FSP1+ fibroblasts were alpha-SMA-, but HSP47+, suggesting they were producing collagen proteins for the extracellular matrix. alpha-SMA+, FSP1-, HSP47+ or HSP47- cells were also observed, and the latter tended to distribute independently in a linear pattern, reminiscent of vasculature adjacent to forming cysts. VIM+ expression was not observed in alpha-SMA+ cells. Many nonoverlapping as well as fewer overlapping populations of FSP1+ and alpha-SMA+ cells shared in the collagen expression associated with progressive fibrogenesis in pcy mice undergoing cystogenesis. Some FSP1+ fibroblasts are likely derived from tubular epithelium undergoing EMT, while alphaSMA+, VIM- cells probably represent vascular smooth muscle cells or pericytes surviving vessel attenuation during the chaos of fibrogenesis. Importantly, not all interstitial cells producing collagens are alpha-SMA+.

Distinct and common developmental expression patterns of the murine Pkd2 and Pkd1 genes

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most commonly inherited renal diseases. At least two genes, PKD2 and PKD1 are implicated in the development of this disease. Our pathogenetic studies showed that the human and murine polycystic kidney disease (PKD) involves failure to switch out of a renal developmental program. We have thus undertaken a detailed comparative expression analysis of Pkd2 and Pkd1 from the morula stage to adulthood. Pkd2 expression was detected as early as the morula and blastocyst stages as observed for Pkd1. Strong Pkd2 expression, similar to Pkd1, was displayed in all mesenchymal and cartilaginous tissues during mouse development. However major differences in Pkd2 expression in comparison to Pkd1 were identified. First, in contrast to Pkd1, the neural crest cell-derived tissues displayed a low to undetectable Pkd2 expression at all ages. Second, no increase in Pkd2 expression was detected during mesenchymal condensation. Third, high Pkd2 expression in the kidneys was localized mainly to the tubular epithelium of the cortical region from murine development to adulthood.

In vitro modulation of cyst formation by a novel tyrosine kinase inhibitor

Recessively transmitted polycystic kidney disease (PKD) in many murine models is characterized by the initial formation of proximal tubular cysts (stage 1), followed by growth and enlargement of renal collecting tubule (CT) cysts (stage 2). Previous studies have reported that stage 1 cyst formation and growth could be manipulated in vitro by using embryonic kidney explants and newborn explant microslices in organ culture. Microslices of postnatal kidneys cultured on Transwell tissue culture inserts allow experimental manipulation of stage 2 CT cyst development and growth. This system was used to test a potential therapeutic compound for treatment of PKD. This compound, EKI-785, modulates altered epidermal growth factor receptor (EGFR) expression in CT cysts by inhibition of EGFR autophosphorylation. These studies demonstrate that: (a) minor modifications of the previously described organ culture system permit successful culture of more mature renal tissue, and (b) cystic explants treated with EGF and EKI-785 demonstrated a marked reduction in CT cystic lesions compared with cystic explants treated with EGF alone. This study suggests that pharmacological strategies can be used to decrease EGFR tyrosine kinase activity and CT cyst formation and enlargement in murine PKD.

Murine Pkd1 is a developmentally regulated gene from morula to adulthood: role in tissue condensation and patterning.

PKD1 is the most common genetically mutated gene involved in autosomal dominant polycystic kidney disease (ADPKD). Our previous studies have shown that the pathogenesis of human and murine polycystic kidney disease (PKD) involves failure to switch out of a renal developmental program, suggesting a role for PKD1 in development. To investigate this hypothesis, we have cloned a portion of the murine Pkd1 gene and characterized the fetal to adult tissue expression pattern of Pkd1. We chose to clone the transmembrane region of Pkd1, a region prone to mutations in ADPKD. The transmembrane coding region (2.6 kb) has 80.3% nucleotide homology with human PKD1 and 85.3% amino acid similarity. The cloned murine Pkd1 fragment closely resembles that of human PKD1 with respect to both genomic size and exon/intron position. We have demonstrated that this Pkd1 region is not conserved in lower organisms and is mammalian specific. A detailed expression analysis of Pkd1 revealed expression as early as the morula stage and in ES cells with differential expression levels in various tissues/organs throughout development. Highest expression levels were observed in the early condensing mesenchyme of primitive mesoderm and ectoderm. Pkd1 was also expressed at high levels in developing neural tube, neural crest derivatives, prechondrogenic tissue, metanephros, bladder, salivary glands, lung, and blood vessels with lower expression levels in other organs and tissues. Specific spatial and temporal patterns of Pkd1 expression were demonstrated in individual organs, such as lung, kidney, brain, indicating it is highly developmentally regulated. Particularly high levels persisted in mature derivatives of neural tube, neural crest, chondrogenic tissue, metanephros, and lung. In summary, our data suggest that Pkd1 has at least two cellular functions, one a basic function involved in early tissue condensation processes, and the other a mammalian-specific function, that evolved with tissue patterning and tubulogenesis in metanephric and pulmonary development.

Characterization of the murine polycystic kidney disease (Pkd2) gene.

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequent genetically transmitted disorders among Europeans with an attributed frequency of 0.1%. The two most common genetic determinants for ADPKD are the PKD1 and PKD2 genes. In this study we report the genomic structure and pattern of expression of the Pkd2 gene, the murine homolog of the human PKD2 gene. Pkd2 is localized on mouse Chromosome (Chr) 5 proximal to anchor marker D5Mit175, spans at least 35 kb of the mouse genome, and consists of 15 exons. Its translation product consists of 966 amino acids, and the peptide shows a 95% homology to human polycystin2. Functional domains are particularly well conserved in the mouse homolog. The expression of mouse polycystin2 in the developing embryo at day 12.5 post conception is localized in mesenchymally derived structures. In the adult mouse, the protein is mostly expressed in kidney, which suggests its functional relevance for this organ.

The detection of murine autosomal recessive polycystic kidney disease using real-time ultrasound.

Using currently available ultrasound equipment, 38 BPK and CPK mice were evaluated at 7 days of age for the presence of autosomal recessive polycystic kidney disease (ARPKD). The kidneys were less echogenic than adjacent soft tissues and measured between 5.1 and 6.3 mm from pole to pole in 32 unaffected mice and 1 with ARPKD. In 5 mice with ARPKD, the kidneys were similar in echogenicity to adjacent soft tissues and measured between 6.9 and 8.4 mm from pole to pole. Renal sonography is able to identify most mice with polycystic kidney disease prior to the development of abdominal enlargement and laboratory abnormalities, and shows promise for future applications in animal research.

Transforming growth factor alpha and epidermal growth factor expression in experimental murine polycystic kidney disease.

Cystic change in polycystic kidney disease (PKD) is associated with epithelial hyperplasia, altered fluid and electrolyte transport, and de-differentiation of renal tubular epithelium. The role of polypeptide growth factors as potential modulators of cystic change remains an area of controversy. In this study, the expression of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) were assessed by immunohistochemistry and image analysis in glucocorticoid-induced PKD in the newborn mouse. Newborn C3H mice received either 200 mg/kg methylprednisolone acetate (MPA) or 0.9% saline as a control. EGF expression was not detected in significant quantities in either MPA-treated or control animals. TGF alpha, however, was expressed in immature control kidney in a largely basolateral distribution. Expression increased significantly in association with cystic change in MPA-treated animals and was localized to the apical cell surface, implying altered polarity of secretion. There is no evidence that EGF is a mitogen in this early developmental model of PKD. TGF alpha, however, may be an important mediator of cystic change in immature or de-differentiated renal tubular epithelium.

Transforming growth factor ? and epidermal growth factor expression in experimental murine polycystic kidney disease

Transforming growth factor ? and epidermal growth factor expression in experimental murine polycystic kidney disease