Imaging-Based Diagnosis of Autosomal Dominant Polycystic Kidney Disease

The clinical use of conventional ultrasonography (US) in autosomal dominant polycystic kidney disease (ADPKD) is currently limited by reduced diagnostic sensitivity, especially in at-risk subjects younger than 30 years of age. In this single-center prospective study, we compared the diagnostic performance of MRI with that of high-resolution (HR) US in 126 subjects ages 16–40 years born with a 50% risk of ADPKD who underwent both these renal imaging studies and comprehensive PKD1 and PKD2 mutation screening. Concurrently, 45 healthy control subjects without a family history of ADPKD completed the same imaging protocol. We analyzed 110 at-risk subjects whose disease status was unequivocally defined by molecular testing and 45 unaffected healthy control subjects. Using a total of >10 cysts as a test criterion in subjects younger than 30 years of age, we found that MRI provided both a sensitivity and specificity of 100%. Comparison of our results from HR US with those from a previous study of conventional US using the test criterion of a total of three or more cysts found a higher diagnostic sensitivity (approximately 97% versus approximately 82%) with a slightly decreased specificity (approximately 98% versus 100%) in this study. Similar results were obtained in test subjects between the ages of 30 and 40 years old. These results suggest that MRI is highly sensitive and specific for diagnosis of ADPKD. HR US has the potential to rival the diagnostic performance of MRI but is both center- and operator-dependent.     

Predictors of Autosomal Dominant Polycystic Kidney Disease Progression

Autosomal dominant polycystic kidney disease is a genetic disorder associated with substantial variability in its natural course within and between affected families. Understanding predictors for rapid progression of this disease has become increasingly important with the emergence of potential new treatments. This systematic review of the literature since 1988 evaluates factors that may predict and/or effect autosomal dominant polycystic kidney disease progression. Predicting factors associated with early adverse structural and/or functional outcomes are considered. These factors include PKD1 mutation (particularly truncating mutation), men, early onset of hypertension, early and frequent gross hematuria, and among women, three or more pregnancies. Increases in total kidney volume and decreases in GFR and renal blood flow greater than expected for a given age also signify rapid disease progression. Concerning laboratory markers include overt proteinuria, macroalbuminuria, and perhaps, elevated serum copeptin levels in affected adults. These factors and others may help to identify patients with autosomal dominant polycystic kidney disease who are most likely to benefit from early intervention with novel treatments.     

尿肾损伤分子-1预示常染色体显性多囊肾病早期发展速度

目的：探讨尿KIM-1水平与早期ADPKD患者病情进展的相关性,及其预示作用。方法：（1）收集临床确诊为ADPKD患者（CKD1,2期）及体检健康人群各40例,并取其晨起后第2次尿液标本,采用ELISA方法测定尿液中Kim-1浓度,比较多囊肾病人群与正常人群在Kim-1表达程度的差异;（2）用多囊肾患者肾脏体积增长速度判断疾病进展状况,用MRI肾脏成像的方法计算6个月间隔后肾脏体积增长情况;（3）去除肾脏总体积大于1500cm3的患者,以肾脏体积半年增长率2.7%为界,将患者划分为高平均速度组和低平均速度组,比较两组间KIM-1水平差异。结果：（1）多囊肾患者与正常人群相比,eGFR水平（采用CKD-EPI公式计算）差异无统计学意义（P〉0.05）,但尿中Kim-1水平多囊肾病组显著升高[（837.9±821.5）pg/mlvs（440.3±270.2）pg/ml,P〈0.05];（2）多囊肾患者半年肾脏体积增长速度为（4.88±3.86）%,显著高于国外报道的多囊肾患者半年体积增长速度;（3）高平均速度组KIM-1水平高于低平均速度组（P〈0.05）。结论：Kim-1作为肾小管损伤后出现的一种重要的生物标记物在多囊肾病患者群中表达显著升高,能预示早期肾脏体积并未发展到一定程度的多囊肾患者肾体积的增长快慢,但Kim-1在疾病进展中的作用机制仍需要进一步的实验研究阐明。     

TWEAK Signaling Pathway Blockade Slows Cyst Growth and Disease Progression in Autosomal Dominant Polycystic Kidney Disease

BackgroundIn autosomal dominant polycystic kidney disease (ADPKD), cyst development and enlargement lead to ESKD. Macrophage recruitment and interstitial inflammation promote cyst growth. TWEAK is a TNF superfamily (TNFSF) cytokine that regulates inflammatory responses, cell proliferation, and cell death, and its receptor Fn14 (TNFRSF12a) is expressed in macrophage and nephron epithelia.MethodsTo evaluate the role of the TWEAK signaling pathway in cystic disease, we evaluated Fn14 expression in human and in an orthologous murine model of ADPKD. We also explored the cystic response to TWEAK signaling pathway activation and inhibition by peritoneal injection.ResultsMeta-analysis of published animal-model data of cystic disease reveals mRNA upregulation of several components of the TWEAK signaling pathway. We also observed that TWEAK and Fn14 were overexpressed in mouse ADPKD kidney cysts, and TWEAK was significantly high in urine and cystic fluid from patients with ADPKD. TWEAK administration induced cystogenesis and increased cystic growth, worsening the phenotype in a murine ADPKD model. Anti-TWEAK antibodies significantly slowed the progression of ADPKD, preserved renal function, and improved survival. Furthermore, the anti-TWEAK cystogenesis reduction is related to decreased cell proliferation–related MAPK signaling, decreased NF-κB pathway activation, a slight reduction of fibrosis and apoptosis, and an indirect decrease in macrophage recruitment.ConclusionsThis study identifies the TWEAK signaling pathway as a new disease mechanism involved in cystogenesis and cystic growth and may lead to a new therapeutic approach in ADPKD.     

Improvement of Endothelial Dysfunction with Simvastatin in Patients with Autosomal Dominant Polycystic Kidney Disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Endothelial dysfunction (ED), which is an early manifestation of vascular injury, has been shown in patients with ADPKD. Statins have a beneficial effect in the reversal of ED. The aim of this study was to investigate the effects of a statin, simvastatin, on ED in patients with ADPKD. Sixteen patients with ADPKD having well-preserved renal function were included in the study. Endothelial function of the brachial artery was evaluated by using high-resolution vascular ultrasound. Endothelial-dependent dilatation (EDD) was expressed as the percentage change in the brachial artery diameter from baseline to reactive hyperemia. After the baseline evaluations of EDDs, patients were started treatment with simvastatin at a dose of 40 mg/day and were treated for six months. EDDs were recalculated after one and six months of therapy. Interleukin-6 (IL-6) and high-sensitivity C-reactive protein were also measured as markers of inflammation. Baseline EDD was 11.3 ± 6.9% in patients with ADPKD. After one month of simvastatin treatment, EDD increased significantly to 14.6 ± 4.6 % (P = 0.016 versus baseline). Endothelial-dependent dilatation further increased significantly to 18.9 ± 7.5 % (P = 0.011 versus baseline, P = 0.048 versus first month) after six months of therapy. There was also a significant decrease in the level of IL-6 from 21.6 ± 21.7 pg/mL to 9.1 ± 3.5 pg/mL (P= 0.002).

Six months of simvastatin therapy resulted in a significant improvement of ED in patients with ADPKD. This finding may be in part related to the pleiotropic effects of simvastatin.     

Scattered Deletion of PKD1 in Kidneys Causes a Cystic Snowball Effect and Recapitulates Polycystic Kidney Disease

In total, 1 in 1000 individuals carries a germline mutation in the PKD1 or PKD2 gene, which leads to autosomal dominant polycystic kidney disease (ADPKD). Cysts can form early in life and progressively increase in number and size during adulthood. Extensive research has led to the presumption that somatic inactivation of the remaining allele initiates the formation of cysts, and the progression is further accelerated by renal injury. However, this hypothesis is primarily on the basis of animal studies, in which the gene is inactivated simultaneously in large percentages of kidney cells. To mimic human ADPKD in mice more precisely, we reduced the percentage of Pkd1-deficient kidney cells to 8%. Notably, no pathologic changes occurred for 6 months after Pkd1 deletion, and additional renal injury increased the likelihood of cyst formation but never triggered rapid PKD. In mildly affected mice, cysts were not randomly distributed throughout the kidney but formed in clusters, which could be explained by increased PKD-related signaling in not only cystic epithelial cells but also, healthy-appearing tubules near cysts. In the majority of mice, these changes preceded a rapid and massive onset of severe PKD that was remarkably similar to human ADPKD. Our data suggest that initial cysts are the principal trigger for a snowball effect driving the formation of new cysts, leading to the progression of severe PKD. In addition, this approach is a suitable model for mimicking human ADPKD and can be used for preclinical testing.     

Ambulatory Blood Pressure and Endothelial Dysfunction in Patients with Autosomal Dominant Polycystic Kidney Disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Endothelial dysfunction (ED), which is an early manifestation of vascular injury, has been shown in patients with ADPKD. However, the association between ambulatory blood pressure and ED has not been investigated in these patients. Forty-one patients with ADPKD having well-preserved renal function were included in the study. Ambulatory blood pressure monitoring was performed in all patients. Patients were divided into dipper and non-dipper groups. Endothelial function of the brachial artery was evaluated by using high-resolution vascular ultrasound. Endothelial-dependent dilatation was expressed as the percentage change in the brachial artery diameter from baseline to reactive hyperemia. The mean 24-hour systolic blood pressure was similar in both groups (125.5 ± 10.7 mmHg in dippers and 121.2 ± 14.3 in non-dippers, p > 0.05). There was also no significant difference between the mean 24-hour diastolic blood pressures in both groups (82.3 ± 9.6 mmHg in dippers and 77.1 ± 8.6 mmHg in non-dippers, p > 0.05). The nocturnal fall rate in systolic blood pressure was 11.1 ± 1.2% in dippers and 0.98 ± 0.9% in non-dippers (p = 0.001). The nocturnal fall rate in diastolic blood pressure was 14.0 ± 0.9% in dippers and 3.8 ± 0.8% in non-dippers (p = 0.001). Endothelial-dependent dilatation was significantly higher in dippers compared to non-dippers (6.22 ± 4.14% versus 3.57 ± 2.52%, p = 0.025). Non-dipper patients with ADPKD show significant ED, which has an important impact on cardiovascular morbidity and mortality.     

羧酸类化合物DJ5对人肾囊肿衬里上皮细胞的增殖抑制作用

目的：观察羧酸类化合物DJ5对人肾囊肿衬里上皮细胞WT9—12的增殖抑制作用并探讨其作用机制。方法：Mvr法检测细胞增殖,LDH释放实验检测细胞毒性,流式细胞术检测细胞周期和细胞凋亡,Westernblot检测周期相关蛋白P2l、cyclinA,凋亡蛋白队RP,通路蛋白Akt、Fox03a蛋白表达。结果：实验表明100p,mol／L的DJ5作用WT9—12细胞72h,细胞增殖抑制率为59．2％,DJ5使细胞周期阻滞在S期并促进细胞早期凋亡。DJ5可上调WT9—12细胞周期抑制蛋白P2l表达、下调cyclinA表达;使PARP活性片段89kD表达明显增加。DJ5可下调磷酸化Akt、磷酸化Fox03a表达、上调Fox03a表达。结论：DJ5通过阻滞细胞周期、促进细胞凋亡及抑制Akt—Fox03a通路蛋白发挥抑制WT9—12细胞增殖作用。     

The Influence of the Endothelin-Converting Enzyme-1 Gene Polymorphism on the Progression of Autosomal Dominant Polycystic Kidney Disease

Background. A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD), the most common renal hereditary disease. Endothelin-1 (ET-1) has been suggested to be an important disease-promoting factor of the kidney. Endothelin-converting enzyme-1 (ECE-1) is the main protease responsible for ET-1 generation by cleavage of its functionally inactive precursor. We examined the influence of the ECE-1b C-338A polymorphism on the progression of ADPKD toward end-stage renal disease (ESRD). The A allele was suggested to be associated with higher plasma level of ET-1. Methods. 200 ADPKD patients (107 males, 93 females) who had reached ESRD were analyzed. Patients were divided into three groups: (1) 47 patients (23 males, 24 females) with ESRD later than in 63 yr (slow progressors); (2) 71 patients (38 males, 33 females) with ESRD before 45 yr (rapid progressors); and (3) 82 patients (46 males, 36 females) with ESRD between 45–63 yr. Moreover, we analyzed 160 genetically unrelated healthy Czech subjects as the control group (82 males, 78 females, mean age 51.4 ± 8.2 yr). DNA samples from collected blood were genotyped for ECE-1b C-338A polymorphism using described polymerase chain reaction (PCR) followed by restriction enzyme digestion. We compared the frequencies of different genotypes between the groups of slow and rapid progressors and the ages of ESRD with regard to different genotypes. Results. The ECE-1b C-338A genotype distribution showed no differences among the groups of slow progressors, rapid progressors, ADPKD group with ESRD between 45–63 yr and control group. Comparing the ages of ESRD of all patients, we did not find significant differences in the ages with regard to different genotypes: CC (51.5 ± 10.1 yr), AC (51.6 ± 11.4 yr), AA (48.2 ± 5.9 yr). There was a tendency to lower age of ESRD in AA homozygotes in comparison with other genotypes (t-test, p = 0.12). We found no influence of gender. Conclusion. We excluded the effect of ECE-1b C-338A polymorphism on the progression of ADPKD. We could observe a mild tendency toward faster decline of renal function in AA homozygous individuals.