Expression of secreted frizzled related protein 4 and effect of induced-apoptosis in autosomal dominant polycystic kidney disease

Objective To evaluate the expression of secreted frizzled related protein 4 (sFRP4) in autosomal dominant polycystic kidney disease(ADPKD) and the effect of sFRP4 induced apoptosis in ADPKD. Methods (1)Serological method: serum samples of 12 healthy people and 20 ADPKD patients were collected and the levels of sFRP4 in serum were detected by ELSIA assay. (2)Tissue experiments: normal renal tissue was collected from radical nephrectomy for renal carcinoma; polycystic renal tissues were taken from ADPKD patients. The expression of sFRP4 in renal tissues was observed by immunohistochemistry; Real-time PCR was used to explore the mRNA level of sFRP4 and caspase-3; TUNEL method was applied to observe the apoptosis cells existing in ADPKD. (3)studies in vitro: HEK-293T cells were transfected with PcDNA6 and Flag. sFRP4.PcDNA6 respectively, after which Western blotting was performed to detect the expression of caspase-3 protein and flow cytometry was performed to estimate cell apoptosis rate. Results (1)ELISA results showed serum concentrations of sFRP4 in ADPKD were markedly higher than normal control (P＜0.05). (2)Compared with normal renal tissues, the sFRP4 expression was dramatically increased in ADPKD and mainly distributed in the cytoplasm of renal tubular epithelial cells. (3)Real-time PCR showed the expression of sFRP4 and Caspase-3 mRNA in ADPKD were up-regulated comparing with those in normal control (P＜0.05). (4)TUNEL assays revealed that elevated apoptosis appeared in tubular epithelial cells of ADPKD. (5)The level of caspase-3 protein and apoptosis rate were significantly increased after over-expressed sFRP4 in HEK-293T cells (all P＜0.05). Conclusions The expression of sFRP4 is strikingly up-regulated in ADPKD. In addition, abnormal apoptosis of tubular epithelial cells exists in ADPKD and over-expressed sFRP4 can induce apoptosis of HEK-293T cells. This phenomenon may be attributed to the elevated sFRP4.     

Progression of kidney disease varies between families with defects in the polycystic kidney disease type 1 gene in eastern Finland

OBJECTIVE: To characterize, for the first time, the phenotype and clinical course of autosomal dominant polycystic kidney disease (ADPKD) in Finnish patients. MATERIAL AND METHODS: All patients underwent an abdominal sonographic examination and most of those with ADPKD underwent magnetic resonance angiography of the head. Haplotype analysis was used to classify 20 ADPKD families into those with defects in either the polycystic kidney disease type 1 (PKD1) or polycystic kidney disease type 2 (PKD2) genes. Evaluation of the rate of progression of kidney disease in patients with ADPKD was based on creatinine values. RESULTS: Haplotype analysis showed that 16 families had defects in the PKD1 gene and one had defects in the PKD2 gene. Three families were excluded because of uninformative haplotypes. The final study population consisted of 79 unaffected family members, 109 patients with defects in the PKD1 gene and 10 with defects in the PKD2 gene. Higher prevalences of hepatic cysts (3% in healthy relatives, 60% in PKD1 patients and 90% in PKD2 patients; p < 0.001), subarachnoid hemorrhage or cerebral aneurysms (1%, 12% and 0%, respectively; p < 0.001), proteinuria (1%, 23% and 0%, respectively; p < 0.001) and hematuria (5%, 30% and 0%, respectively; p < 0.001) were found in PKD1 patients compared to the healthy relatives. PKD1 patients had a faster progression of kidney disease than PKD2 patients (p < 0.001). The progression of kidney disease varied substantially among the PKD1 families. CONCLUSION: The relative proportions of PKD1 and PKD2 patients and the phenotype of ADPKD were similar in our Finnish patients compared to previous studies in other populations. However, the progression of kidney disease differed substantially among PKD1 families, indicating a heterogeneic genetic background of PKD1 in Finnish patients.     

Analysis of gene mutations in PKD1/PKD2 by multiplex ligation-dependent probe amplification: some new findings

Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is a serious genetic disorder that can lead to chronic renal disease. Protein dysfunction caused by mutations in the genes polycystic kidney disease 1 (PKD1) and polycystic kidney disease 2 (PKD2) is an important factor in the pathogenesis of ADPKD. In the present study, 30 Chinese patients with confirmed diagnosis of ADPKD, based on ultrasound or computerized tomography (CT) findings were selected, and the exon copy numbers of PKD1 and PKD2 were determined using multiplex ligation-dependent probe amplification (MLPA). MLPA identified exon deletion in 1 case, suspected exon deletion in 4 cases, and suspected duplications in 3 cases. One case of suspected exon deletion was confirmed using quantitative real-time polymerase chain reaction (q-PCR) and sequencing (PKD2 exon 8). A missense mutation was observed in 1 case of exon deletion using q-PCR and sequencing (PKD1 exon 40, c.11333 C>A). The cases of suspected duplications were verified by q-PCR, and the copy number of exon 6 of PKD1 in 1 case of suspected duplication was 3.8 times greater than that in normal controls. Our findings provide new insights into ADPKD screening and mark a possibly meaningful step toward improved diagnosis and treatment of patients with ADPKD.     

Mutations in multiple PKD genes may explain early and severe polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is typically a late-onset disease caused by mutations in PKD1 or PKD2, but about 2% of patients with ADPKD show an early and severe phenotype that can be clinically indistinguishable from autosomal recessive polycystic kidney disease (ARPKD). The high recurrence risk in pedigrees with early and severe PKD strongly suggests a common familial modifying background, but the mechanisms underlying the extensive phenotypic variability observed among affected family members remain unknown. Here, we describe severely affected patients with PKD who carry, in addition to their expected familial germ-line defect, additional mutations in PKD genes, including HNF-1β, which likely aggravate the phenotype. Our findings are consistent with a common pathogenesis and dosage theory for PKD and may propose a general concept for the modification of disease expression in other so-called monogenic disorders.     

Protective effect of C5a receptor 1 antagonist on ascending urinary tract infection in mice

Objective To investigate the protective effect of complement 5a receptor 1 (C5aR1) antagonist on ascending urinary tract infection in mice. Methods (1) Female C57BL/6 mice were randomly divided into experimental and control groups: 38 mice in each group, and inoculated with E. coli by urethral catheterization to set up the ascending urinary tract infection model. C5aR1 antagonist (W54011 or PMX53) and corresponding control (PBS or control peptide) were initially given either at 2 h before or 3 h after infection by intraperitoneal injection. Mice were sacrificed to assess the infection in bladder and kidney at 24 or 48 h after infection. The bacterial load of bladder and kidney tissue was measured by agar plate assay. The mRNA expression of renal inflammatory factors was detected by real-time RCR. The renal tissue injury and inflammatory cell infiltration were assessed by HE staining and pathological scores. (2) Primary cultured renal tubular epithelial cells were randomly divided into antagonist and control groups to detect and compare the bacterial adhesion to renal tubular epithelial cells in vitro. Results Compared with control groups, the initial delivery of C5aR1 antagonist (W54011 or PMX53) before E.coli inoculation reduced the bacterial load in bladder and kidney tissue 48 h after infection (all P＜0.01). In experimental group given W54011 before infection, the renal pathological scores were reduced (both P＜0.05), as well as renal inflammatory factor expressions: CXCL-1 mRNA, IL-6 mRNA and TNF-α mRNA (all P＜0.05). Compared with corresponding control groups, the initial delivery of PMX53 after E. coli inoculation could also reduce the bacterial load in bladder and kidney tissue 48 h after infection (both P＜0.01). Furthermore, C5aR1 antagonists W54011 and PMX53 could decrease bacteria adhesion to renal tubular epithelial cells in vitro, compared with control groups (both P＜0.05). Conclusions C5aR1 antagonists can significantly attenuate renal tissue injury, ameliorate renal inflammation and the adhesion of bacteria to renal epithelial cells. C5aR1 may be an effective target for the prevention and treatment of urinary tract infection.     

JAK2-STAT3 pathway regulates the expression of complement factor B in autosomal dominant polycystic kidney disease

Objective To investigate the role of JAK2-STAT3 pathway in the expression of complement factor B (CFB) in autosomal dominant polycystic kidney disease (ADPKD). Methods Renal tissue samples of patients with ADPKD after nephrectomy were collected. Normal renal tissue samples as control were taken from patients after radical nephrectomy. Renal tissue samples of Han: SPRD Cy/+ rats (ADPKD model) and wild-type Han: SPRD +/+ rats were also collected at 4, 8, 16 week. Han:SPRD Cy/+ rat renal tubular epithelial cells (16 w) were primarily cultured in vitro, then stimulated with the JAK2 inhibitor (WP1066) and STAT3 inhibitor (pyrimethamine) for 24 h respectively. Western blotting was used to detect the expression of p-JAK2, JAK2, p-STAT3, STAT3, CFB protein. Results Compared with control group, the protein expressions of p-JAK2, p-STAT3, STAT3, CFB significantly increased in the renal tissue of ADPKD patients (all P＜0.05). The protein expressions of p-JAK2, JAK2, p-STAT3, STAT3 and CFB also significantly increased in the renal tissue of Cy/+ rats compared with wild-type rats (all P＜0.01). When the Cy/+ renal tubular epithelial cells were treated with WP1066, the expressions of p-JAK2, p-STAT3, CFB were suppressed (P＜0.05) and the degree of inhibition was correlated with the WP1066 dose. Pyrimethamine inhibited the protein expressions of p-STAT3 and CFB in the tubular epithelial cells of Cy/+ rats (all P＜0.05) and the degree of inhibition was correlated with the pyrimethamine dose. Conclusions The JAK2-STAT3 pathway is abnormally activated in ADPKD and increases the protein expression of CFB. CFB protein level is correlated with the progress of ADPKD, suggesting that it may take part in the growth and development of ADPKD vesicles.     

A missense mutation in PKD1 attenuates the severity of renal disease

Mutations of PKD1 and PKD2 account for most cases of autosomal dominant polycystic kidney disease (ADPKD). Compared with PKD2, patients with PKD1 typically have more severe renal disease. Here, we report a follow-up study of a unique multigeneration family with bilineal ADPKD (NFL10) in which a PKD1 disease haplotype and a PKD2 (L736X) mutation co-segregated with 18 and 14 affected individuals, respectively. In our updated genotype-phenotype analysis of the family, we found that PKD1-affected individuals had uniformly mild renal disease similar to the PKD2-affected individuals. By sequencing all the exons and splice junctions of PKD1, we identified two missense mutations (Y528C and R1942H) from a PKD1-affected individual. Although both variants were predicted to be damaging to the mutant protein, only Y528C co-segregated with all of the PKD1-affected individuals in NFL10. Studies in MDCK cells stably expressing wild-type and mutant forms of PKD found that cell lines expressing the Y528C variant formed cysts in culture and displayed increased rates of growth and apoptosis. Thus, Y528C functions as a hypomorphic PKD1 allele. These findings have important implications for pathogenic mechanisms and molecular diagnostics of ADPKD.     

Looking at the (w)hole: magnet resonance imaging in polycystic kidney disease

Inherited cystic kidney diseases, including autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD), are the most common monogenetic causes of end-stage renal disease (ESRD) in children and adults. While ARPKD is a rare and usually severe pediatric disease, the more common ADPKD typically shows a slowly progressive course leading to ESRD in adulthood. At the present time there is no established disease-modifying treatment for either ARPKD or ADPKD. Various therapeutic approaches are currently under investigation, such as V2 receptor antagonists, somatostatins, and mTOR inhibitors. Renal function remains stable for decades in ADPKD, and thus clinically meaningful surrogate markers to assess therapeutic efficacy are needed. Various studies have pointed out that total kidney volume (TKV) is a potential surrogate parameter for disease severity in ADPKD. Recent trials have therefore measured TKV by magnet resonance imaging (MRI) to monitor and to predict disease progression. Here, we discuss novel insights on polycystic kidney disease (PKD), the value of MRI, and the measurement of TKV in the diagnosis and follow-up of PKD, as well as novel emerging therapeutic strategies for ADPKD.     

Inheritance of a stable mutation in a family with early-onset disease

Autosomal/dominant polycystic kidney disease (ADPKD) exhibits a high inter- and intrafamilial heterogeneity partly explained by the involvement of at least 3 different genes in the disorder transmission. PKD1, the major locus, is located on chromosome 16p. The occurrence of very early-onset cases of ADPKD (sometimes in utero) in a few PKD1 families or the increased severity of the disease in successive generations raise the question of anticipation. This is a subject of controversial discussion. This report deals with the molecular analysis in families with very early-onset ADPKD. The finding of the same stable mutation with such different phenotypes rules out a dynamic mutation. The molecular basis of severe childhood PKD in typical ADPKD families remains unclear; it may include segregation of modifying genes or unidentified factors and the two-hit mechanism.     

Comprehensive PKD1 and PKD2 Mutation Analysis in Prenatal Autosomal Dominant Polycystic Kidney Disease

Prenatal forms of autosomal dominant polycystic kidney disease (ADPKD) are rare but can be recurrent in some families, suggesting a common genetic modifying background. Few patients have been reported carrying, in addition to the familial mutation, variation(s) in polycystic kidney disease 1 (PKD1) or HNF1 homeobox B (HNF1B), inherited from the unaffected parent, or biallelic polycystic kidney and hepatic disease 1 (PKHD1) mutations. To assess the frequency of additional variations in PKD1, PKD2, HNF1B, and PKHD1 associated with the familial PKD mutation in early ADPKD, these four genes were screened in 42 patients with early ADPKD in 41 families. Two patients were associated with de novo PKD1 mutations. Forty patients occurred in 39 families with known ADPKD and were associated with PKD1 mutation in 36 families and with PKD2 mutation in two families (no mutation identified in one family). Additional PKD variation(s) (inherited from the unaffected parent when tested) were identified in 15 of 42 patients (37.2%), whereas these variations were observed in 25 of 174 (14.4%, P=0.001) patients with adult ADPKD. No HNF1B variations or PKHD1 biallelic mutations were identified. These results suggest that, at least in some patients, the severity of the cystic disease is inversely correlated with the level of polycystin 1 function.     

Pathways of apoptosis in human autosomal recessive and autosomal dominant polycystic kidney diseases

Autosomal dominant polycystic kidney disease (ADPKD) is a major cause of end-stage renal disease in adults. Autosomal recessive (AR) PKD affects approximately 1:20,000 live-born children with high perinatal mortality. Both diseases have abnormalities in epithelial proliferation, secretion, and cell-matrix interactions, leading to progressive cystic expansion and associated interstitial fibrosis. Cell number in a kidney reflects the balance between proliferation and apoptosis. Apoptosis results from extrinsic (ligand-induced, expression of caspase-8) and intrinsic (mitochondrial damage, expression of caspase-9) triggers. Previous studies have suggested a role for apoptosis in PKD cyst formation and parenchymal destruction. Mechanisms underlying apoptosis in human ADPKD and ARPKD were examined by quantitative immunohistochemistry and Western immunoblot analyses of age-matched normal and PKD tissues. Caspase-8 expression was significantly greater in small cysts and normal-appearing tubules than in larger cysts in ADPKD kidneys. Caspase-8 also appeared early in the disease process of ADPKD. In ARPKD, expression of caspase-8 was most pronounced in later stages of the disease and was not confined to a specific cyst size. In conclusion, apoptosis in human ADPKD is an early event, occurring predominantly in normal-appearing tubules and small cysts, and is triggered by an extrinsic factor, but it occurs later in ARPKD.     

Identification of gene mutations in autosomal dominant polycystic kidney disease through targeted resequencing

Mutations in two large multi-exon genes, PKD1 and PKD2, cause autosomal dominant polycystic kidney disease (ADPKD). The duplication of PKD1 exons 1-32 as six pseudogenes on chromosome 16, the high level of allelic heterogeneity, and the cost of Sanger sequencing complicate mutation analysis, which can aid diagnostics of ADPKD. We developed and validated a strategy to analyze both the PKD1 and PKD2 genes using next-generation sequencing by pooling long-range PCR amplicons and multiplexing bar-coded libraries. We used this approach to characterize a cohort of 230 patients with ADPKD. This process detected definitely and likely pathogenic variants in 115 (63%) of 183 patients with typical ADPKD. In addition, we identified atypical mutations, a gene conversion, and one missed mutation resulting from allele dropout, and we characterized the pattern of deep intronic variation for both genes. In summary, this strategy involving next-generation sequencing is a model for future genetic characterization of large ADPKD populations.     

An efficient linkage analysis strategy for autosomal dominant polycystic kidney disease

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited renal disorders in the world. Mutations in PKD1 are responsible for 80-95% of all autosomal dominant polycystic kidney disease (ADPKD). Although the need for linkage analysis of ADPKD is decreasing after the success of mutation detection at whole exons of PKD1, linkage analysis still has some advantages in detecting non-PKD1 families, thereby avoiding hopeless mutation analysis. METHODS: We evaluated ten microsatellite markers beside or inside PKD1 on chromosome 16p. Allele frequency and heterozygosity of each marker were calculated based on the 100 genotypes obtained from 50 normal Japanese. Automated microsatellite genotyping using ABI Prism 377 and GeneScan software was applied. Markers were mapped using radiation hybrid mapping. Finally, this strategy was applied in the linkage analysis of 6 independent Japanese ADPKD families. RESULTS: D16S3024, D16S3082, D16S3027 and D16S423 showed high heterozygosity (> 0.80) in a normal Japanese population and sufficient proximity to the PKD1 gene for linkage analysis. We could successfully analyze 144 genotypes within 7 hours. This strategy produced theoretically near-maximum LOD scores in 4 independent Japanese families inheriting ADPKD. CONCLUSIONS: Automated genotyping using microsatellite markers, D16S3024, D16S3082, D16S3027 and D16S423 are very useful in the linkage analysis of ADPKD.     

Polycystic kidney diseases: molecular genetics and counselling

Autosomal dominant polycystic kidney disease (ADPKD) affects 1 newborn in 400 to 1000 making it the most common inherited form of genetic kidney disease and an important cause of medical morbidity and account for about 10% of end-stage renal disease. Autosomal recessive polycystic kidney disease (ARPKD) is a rare (1/20,000 to 1/40,000) inherited disease in children characterized by the association of dilation of collecting ducts and biliary dysgenesis. The clinical spectrum is variable but it represents an important cause of renal and liver-related morbidity and mortality in neonates and infancy. Symptoms of autosomal recessive PKD can begin before birth. ARPKD is genetically different from ADPKD. Parents who do not have the disease can have a child with the disease if both parents carry the abnormal gene and both pass the gene to their baby. Recently important advances in understanding the molecular basis of ADPKD (i.e. ADPKD1 and ADPKD2) and autosomal recessive PKD (i.e. PKHD1) have been done and are reported here. Genetic counselling is particularly advised in early onset disease families. It permits to determine the type of transmission, to describe the course and the major complications of the disease and to explain currents therapeutics possibilities.     

Familial phenotype differences in PKD11.

Familial phenotype differences in PKD1. BACKGROUND: Mutations within the PKD1 gene are responsible for the most common and most severe form of autosomal dominant polycystic kidney disease (ADPKD). Although it is known that there is a wide range of disease severity within PKD1 families, it is uncertain whether differences in clinical severity also occur among PKD1 families. METHODS: Ten large South Wales ADPKD families with at least 12 affected members were included in the study. From affected members, clinical information was obtained, including survival data and the presence of ADPKD-associated complications. Family members who were at risk of having inherited ADPKD but were proven to be non-affected were included as controls. Linkage and haplotype analysis were performed with highly polymorphic microsatellite markers closely linked to the PKD1 gene. Survival data were analyzed by the Kaplan-Meier method and the log rank test. Logistic regression analysis was used to test for differences in complication rates between families. RESULTS: Haplotype analysis revealed that each family had PKD1-linked disease with a unique disease-associated haplotype. Interfamily differences were observed in overall survival (P = 0.0004), renal survival (P = 0.0001), hypertension prevalence (P = 0.013), and hernia (P = 0.048). Individuals with hypertension had significantly worse overall (P = 0.0085) and renal (P = 0.03) survival compared with those without hypertension. No statistically significant differences in the prevalence of hypertension and hernia were observed among controls. CONCLUSION: We conclude that phenotype differences exist between PKD1 families, which, on the basis of having unique disease-associated haplotypes, are likely to be associated with a heterogeneous range of underlying PKD1 mutations.     

肾移植治疗常染色体显性遗传性多囊肾病患者的临床效果分析（附43例报告）

目的探讨肾移植治疗常染色体显性遗传性多囊肾病（多囊肾）患者的疗效。方法多囊肾患者43例（多囊肾组）,在不切除原双侧肾脏的前提下,进行肾移植,以同期50例原发病为非多囊肾的肾移植患者作为对照组,进行随访研究。比较两组的术后1、3、5年人、肾存活率及排斥反应发生情况,通过肾脏B超检查多囊肾组患者术前与术后移植肾的体积变化,记录多囊肾组的并发症发生情况。结果多囊肾组肾移植术后1、3、5年人存活率分别为95.3%、90.6%、90.6%,术后1、3、5年肾存活率分别为95.3%、88.3%、83.7%。对照组相应为96.0%、92.0%、90.0%,94.0%、92.0%、88.0%,两组比较差异无统计学意义（P〉0.05）。两组的急性排斥反应发生率比较差异亦无统计学意义（P〉0.05）。多囊肾组术后3～6个月原肾明显缩小,1年后体积基本稳定,跟踪观察1～15年肾脏体积变化不明显。移植后血尿逐渐减轻,7～10d后消失。12例在移植后5～10周反复出现肉眼血尿,均经抗感染治疗后消失。多囊肾患者移植后仍需要应用药物控制血压。多囊肾组尿路感染发生率高达40%。32例多囊肾合并多囊肝,术后发生肝功能损害7例。结论多囊肾患者采用不切除原肾的肾移植效果满意,移植后应严密观察患者移植物肾功能、血尿和感染情况,及时对症处理。     

Facilitated diagnosis of the contiguous gene syndrome: tuberous sclerosis and polycystic kidneys by means of haplotype studies

Tuberous sclerosis (TSC) and autosomal dominant polycystic kidney disease (ADPKD) are genetically heterogeneous diseases. The major gene for ADPKD (PKD1) lies adjacent to the TSC2 gene on chromosome 16p13. Some reports in the literature referred to an unusual presentation of TSC with enlarged cystic kidneys at birth, but it was not until the localization of the TSC2 and PKD1 genes that it was possible to analyze the interaction between both genes. We describe a case of a child with TSC and enlarged cystic kidneys. The study of genetic marker segregation in the family pointed to the presence of a deletion involving the 3' region of PKD1. A further study of the region showed a deletion of 40 kb involving both PKD1 and TSC2. We suggest that an additive or synergistic effect between PKD1 and TSC2 may cause this renal phenotype. A contiguous gene syndrome involving PKD1 and TSC2 should be suspected in children with TSC and enlarged polycystic kidneys at birth. The first approach to identify a deletion of both genes could be the analysis of the segregation of PKD1 and TSC2 markers in the family.     

ADPKD: molecular characterization and quest for treatment

Autosomal-dominant polycystic kidney disease (ADPKD) is a common hereditary disease that features multiple cystogenesis in various organs and vascular defects. The genes responsible for ADPKD, PKD1, and PKD2 have been identified, and the pathological processes of the disease are becoming clearer. This review focuses on recent findings about the molecular and cellular biology of ADPKD, and especially on PKD1. PKD1 and its product, polycystin-1, play pivotal roles in cellular differentiation because they regulate the cell cycle and because polycystin-1 is a component of adherens junctions. A possible link between polycystin-1 and PPARγ is discussed. The extraordinarily fast research progress in this area in the last decade has now reached a stage where the development of a remedy for ADPKD might become possible in the near future.