Protocol for the nationwide registry of patients with polycystic kidney disease: japanese national registry of PKD (JRP).

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are major genetic polycystic kidney diseases that can progress to end-stage kidney disease (ESKD). Longitudinal data on the clinical characteristics associated with clinical outcomes in polycystic kidney disease (PKD), including the development of ESKD and cardiovascular disease (CVD) are lacking in Japan. To address this unmet need the authors are establishing a novel, web-based, Nationwide Cohort Registry Study-the Japanese Registry of PKD (JRP). METHODS: The JRP is a prospective cohort study for ADPKD (aim to recruit n = 1000 patients), and both a retrospective and prospective study for ARPKD (aim to recruit n = 100). In the prospective registry, patients will be followed-up for 10 years every 6 months and 12 months for patients with ADPKD and ARPKD, respectively. Data collection will be recorded on Research Electronic Data Capture (REDCap) starting on April 1, 2024, with recruitment ending on March 31, 2029. (jRCT 1030230618). RESULTS: Data to be collected include: baseline data, demographics, diagnostic and genetic information, radiological and laboratory findings, and therapeutic interventions. During follow-up, clinical events such as development of ESKD, hospitalization, occurrence of extra kidney complications including CVD events, and death will be recorded, as well as patient-reported health-related quality of life for patients with ADPKD. CONCLUSIONS: The JRP is the first nationwide registry study for patients with ADPKD and ARPKD in Japan, providing researchers with opportunities to advance knowledge and treatments for ADPKD and ARPKD, and to inform disease management and future clinical practice.

Public support for patients with intractable diseases in Japan: impact on clinical indicators from nationwide registries in patients with autosomal dominant polycystic kidney disease.

BACKGROUND: Clinical practice guidelines recommend antihypertensive and tolvaptan therapies for patients with autosomal dominant polycystic kidney disease (ADPKD) in Japan. However, tolvaptan therapy may pose an economic burden. The Japanese Ministry of Health, Labour and Welfare supports patients with intractable diseases. This study aimed to confirm the impact of the intractable disease system in Japan on the clinical treatment of ADPKD. METHODS: We analyzed the data of 3768 patients with ADPKD having a medical subsidy certificate from the Japanese Ministry of Health, Labour and Welfare in 2015-2016. The following quality indicators were use: the adherence rate to the 2014 clinical practice guideline for polycystic kidney disease (prescription rates of antihypertensive agents and tolvaptan in this cohort) and the number of Japanese patients with ADPKD nationwide started on renal replacement therapy in 2014 and 2020. RESULTS: Compared with new applications from 2015 to 2016, the prescription rates of antihypertensives and tolvaptan for the indicated patients at the 2017 renewal application increased by 2.0% (odds ratio = 1.41, p = 0.008) and 47.4% (odds ratio = 10.1, p > 0.001), respectively. These quality indicators improved with antihypertensive treatment, especially in patients with chronic kidney disease stages 1-2 (odds ratio = 1.79, p = 0.013) and in those aged < 50 years (odds ratio = 1.70, p = 0.003). The number of patients with ADPKD who were started on renal replacement therapy in Japan decreased from 999 in 2014 to 884 in 2020 in the nationwide database (odds ratio = 0.83, p < 0.001). CONCLUSIONS: The Japanese public intractable disease support system contributes to improvement of ADPKD treatment.

Cystic Kidney Diseases That Require a Differential Diagnosis from Autosomal Dominant Polycystic Kidney Disease (ADPKD).

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease, with patients often having a positive family history that is characterized by a similar phenotype. However, in atypical cases, particularly those in which family history is unclear, a differential diagnosis between ADPKD and other cystic kidney diseases is important. When diagnosing ADPKD, cystic kidney diseases that can easily be excluded using clinical information include: multiple simple renal cysts, acquired cystic kidney disease (ACKD), multilocular renal cyst/multilocular cystic nephroma/polycystic nephroma, multicystic kidney/multicystic dysplastic kidney (MCDK), and unilateral renal cystic disease (URCD). However, there are other cystic kidney diseases that usually require genetic testing, or another means of supplementing clinical information to enable a differential diagnosis of ADPKD. These include autosomal recessive polycystic kidney disease (ARPKD), autosomal dominant tubulointerstitial kidney disease (ADTKD), nephronophthisis (NPH), oral-facial-digital (OFD) syndrome type 1, and neoplastic cystic kidney disease, such as tuberous sclerosis (TSC) and Von Hippel-Lindau (VHL) syndrome. To help physicians evaluate cystic kidney diseases, this article provides a review of cystic kidney diseases for which a differential diagnosis is required for ADPKD.

Factors predicting decline in renal function and kidney volume growth in autosomal dominant polycystic kidney disease: a prospective cohort study (Japanese Polycystic Kidney Disease registry: J-PKD).

BACKGROUND: Factors affecting decline in renal function and cyst growth in patients with autosomal polycystic kidney disease (ADPKD) are not fully described, particularly in Japan. METHODS: This was the first multi-facility, prospective, observational cohort study conducted in ADPKD patients at 14 centers in Japan. Patients in the J-PKD registry were assessed from December 2009 to June 2012 (follow-up until June 2017). Patients' data including estimated glomerular filtration rate (eGFR) and total kidney volume (TKV) were assessed initially and a maximum of five times annually. Contributing factors to eGFR decline and TKV growth were identified using multiple linear regression analysis. RESULTS: Of the 340 patients in the J-PKD registry, data analysis was performed for 192 patients in whom serial changes for both eGFR and TKV were obtained. eGFR slope, eGFR change, and TKV change values were as follows: - 2.7 (- 4.2 to - 1.5) (ml/min/1.73 m2/year), - 5.0 (- 9.6 to - 2.3) (%/year), and 4.78 (0.86-8.22) (%/year), respectively. Lower high-density lipoprotein (HDL) cholesterol was an independent predictor of eGFR decline, using both eGFR slope and change (P = 0.04, P = 0.02, respectively), whereas lower hemoglobin and higher uric acid were significantly associated with greater eGFR change only (P = 0.02, P = 0.002, respectively). Younger age and higher fasting blood sugar were independent predictors of greater TKV change (P = 0.01, P = 0.02, respectively). CONCLUSIONS: This real-world study in Japan identified risk factors for renal function decline in ADPKD patients. These included lower HDL cholesterol, lower hemoglobin and higher uric acid for eGFR decline, and youth and higher blood sugar levels for TKV growth.

Etiology and impact on outcomes of polycystic kidney disease in abdominal aortic aneurysm.

PURPOSE: We investigated the etiology and impact on outcomes of polycystic kidney disease in patients with abdominal aortic aneurysm. METHODS: Eight-hundred patients who underwent open (n = 603) or endovascular aortic repair (n = 197) were divided into three groups: no cyst (n = 204), non-polycystic kidney (n = 503), and polycystic kidney (≥ 5 cysts in the bilateral kidneys, n = 93). The characteristics and outcomes were compared among the groups. RESULTS: In the polycystic kidney group, the age was increased and the proportions of patients with male sex, hypertension, and estimated glomerular filtration rate < 30 mL/min/1.73 m2 were greater. The overall hospital mortality rates were similar. The incidence of acute kidney injury after elective open aortic repair was increased in the polycystic kidney group (12%, 17%, and 29%, P = 0.020). In the polycystic kidney group, 80 patients did not have renal enlargement or a family history of renal disease, while 13 (corresponding to 1.6% [13/800] of the overall patients), had renal enlargement, suggesting the possibility of hereditary polycystic kidney disease. CONCLUSIONS: In our cohort, 1.6% of the patients with abdominal aortic aneurysm who underwent surgery were at risk of hereditary polycystic kidney disease. Polycystic kidney disease was associated with acute kidney injury after open aortic repair.

The relationship between liver cyst volume and QOL in Japanese ADPKD patients.

BACKGROUND: Although it is widely accepted that the autosomal dominant polycystic kidney disease (ADPKD) patients with large liver cysts have a significant decrement in quality of life (QOL), there is insufficient evidence that clearly demonstrates the relationship between the size of the liver cysts and QOL. Therefore, we started this prospective longitudinal study to investigate the impact of liver cysts on QOL. METHODS: We grouped the 111 included ADPKD patients into 4 groups (control group A; < 25%, group B; 25-49%, group C; 50-75%, group D; > 75%) according to liver cysts-parenchyma ratio (CPR). QOL was measured by FANLTC + FACT-Hep scores. We compared QOL scores and several clinical parameters amongst these groups for 3 years. RESULTS: The number of patients in group A, B, C, and D was 31, 14, 14, and 23, respectively. Although there were no significant differences in AST (p = 0.107), ALT (p = 0.925), and serum albumin (p = 0.212) between the four groups, platelet count was significantly decreased along with the extension of cyst volume (p = 0.030). Overall, the mean FANLTC and FACT-Hep scores were 71.8 ± 12.5, and 32.4 ± 5.8, respectively. FANLTC (p = 0.017) and FACT-Hep scores (p = 0.003) were significantly decreased with increasing cyst volume. From the data collected at the time of registration, multivariate linear regression analysis demonstrated that the CPR had a significant influence on FANLTC and FACT-Hep scores. CONCLUSION: In this cross-sectional and prospective longitudinal study, we demonstrate the relationship between liver cyst volume and QOL in ADPKD patients. We hope to establish the long-term influence on QOL in this ongoing prospective longitudinal study.

Maternally inherited diabetes and deafness complicated by mesangial galactose-deficient IgA1 deposits: a case report.

BACKGROUND: Maternally inherited diabetes and deafness (MIDD), a mitochondrial genetic disorder, typically affects the kidneys and results in end-stage renal disease. Early diagnosis of MIDD is challenging when renal manifestations precede other key clinical features such as diabetes and deafness and/or when the disease is complicated by other renal pathologies. CASE PRESENTATION: Here, we present the case of a 33-year-old Japanese woman who had initially been diagnosed with IgA nephropathy but was found to have MIDD 6 years later. Two renal biopsies were conducted six years apart. While assessment of the first biopsy specimen with the monoclonal antibody (KM55) revealed mesangial IgA deposits (containing the galactose-deficient IgA1 variant [Gd-IgA1]), examination of the second specimen showed no mesangial IgA deposits and newly-developed glomerular global scleroses and tubular damage. Granular swollen epithelial cells (GSECs), characterised by abnormal mitochondria, were observed among the tubules and collecting ducts in both biopsy specimens. Mitochondrial DNA analysis revealed an m.3243A > G mutation. CONCLUSIONS: We rediscovered the usefulness of GSECs as a pathologically distinctive feature of mitochondrial nephropathy and reviewed the literature regarding MIDD complicated by mesangial IgA deposition. Furthermore, we demonstrate that the mesangial IgA deposits in this patient consisted of the galactose-deficient IgA1 variant. The monoclonal antibody (KM55) might be a useful tool to distinguish IgAN from latent IgA deposits.

Tonsillectomy reduces recurrence of IgA nephropathy in mesangial hypercellularity type categorized by the Oxford classification.

BACKGROUND: In patients with IgA nephropathy (IgAN), recurrence after steroid pulse therapy is associated with reduced renal survival. However, the predictors of recurrence have not yet been clarified. METHODS: All patients who received 6-month steroid pulse therapy from 2004 to 2010 in our four affiliated hospitals and achieved a reduction of proteinuria to <0.4 g/day 1 year after treatment were retrospectively evaluated. The primary outcome was proteinuria ≥1.0 g/day during follow-up or additional antiproteinuric therapy. Two histological classifications were evaluated, the Oxford Classification with a split system and Japanese histological grades (HGs) with a lumped system. RESULTS: During a median follow-up of 3.4 years, 27 (26.7 %) of the 101 patients showed recurrence. Multivariate analysis showed that HG was the only significant predictor of recurrence, with HG 2+3+4 vs HG 1 having a hazard ratio of 7.38 (95 % confidence interval 1.52-133). Furthermore, in patients with mesangial hypercellularity according to the Oxford Classification, cumulative rate of recurrence-free survival was greater in patients with steroid therapy plus tonsillectomy compared with those who received steroid therapy alone (Log-rank test, P = 0.022). However, this association was not observed in patients without mesangial hypercellularity. CONCLUSIONS: HG is a novel predictor of recurrence after steroid pulse therapy in patients with IgAN. Moreover, the combination of steroid pulse therapy plus tonsillectomy may indicate a lower risk of recurrence in patients with mesangial hypercellularity, as defined by the Oxford Classification.

Social functioning and socioeconomic changes after introduction of regular dialysis treatment and impact of dialysis modality: a multi-centre survey of Japanese patients.

AIM: Patient socialization and preservation of socioeconomic status are important patient-centred outcomes for those who start dialysis, and retention of employment is a key enabler. This study examined the influence of dialysis inception and modality upon these outcomes in a contemporary Japanese cohort. METHODS: We conducted a survey of prevalent chronic dialysis patients from 5 dialysis centres in Japan. All patients who had been on peritoneal dialysis (PD) since dialysis inception were recruited, and matched with a sample of those on in-centre haemodialysis (ICHD). We assessed patients' current social functioning (Short Form 36 Health Survey), and evaluated changes to patient employment status, annual income, and general health condition from the pre-dialysis period to the current time. RESULTS: A total of 179 patients were studied (102 PD and 77 ICHD). There were no differences in social functioning by modality. Among them, 113 were employed in the pre-dialysis period with no difference by modality. Of these, 22% became unemployed after dialysis inception, with a corresponding decline in average working hours and annual income. The odds of unemployment after dialysis inception were 5.02 fold higher in those on ICHD compared to those on PD, after adjustment for covariates. There were no changes for those who were already unemployed in the pre-dialysis period. CONCLUSIONS: Employment status is significantly hampered by dialysis inception, although PD was associated with superior retention of employment and greater income compared to ICHD. This supports a positive role for PD in preservation of socioeconomic status and potentially other patient-centred outcomes.

Angiotensin receptor blocker (ARB)-diuretic versus ARB-calcium channel blocker combination therapy for hypertension uncontrolled by ARB monotherapy.

Diuretics or calcium channel blockers (CCBs) are used concomitantly with an angiotensin II receptor blocker (ARB). However, it is not established which ARB-based combination therapy is the most effective and safe. This prospective randomized open-label study compared the efficacy and safety of a fixed-dose tablet of losartan (LST)-hydrochlorothiazide (HCTZ) (n = 99) and LST-amlodipine (AML) (n = 77) in Japanese patients whose hypertension was uncontrolled by ARB monotherapy. Blood pressure changed similarly over the 12-month study period. Only LST-HCTZ significantly increased serum uric acid (SUA) in patients with low baseline SUA (<5.6 mg/dL) but not in patients with high baseline SUA.

Replication study for the association of 3 SNP loci identified in a genome-wide association study for diabetic nephropathy in European type 1 diabetes with diabetic nephropathy in Japanese patients with type 2 diabetes.

BACKGROUND: A recent genome-wide association study for diabetic nephropathy in European type 1 diabetes identified 3 candidate loci for diabetic nephropathy. In this study, we examined the association of the 3 single nucleotide polymorphism (SNP) loci with susceptibility to diabetic nephropathy in Japanese subjects with type 2 diabetes. METHODS: We genotyped 3 SNPs, rs7583877 in AFF3, rs12437854 in the RGMA-MCTP2 locus and rs7588550 in ERBB4, for 2,300 Japanese patients with type 2 diabetes [initial study, 1,055 nephropathy cases with overt proteinuria or with end-stage renal disease (ESRD) and 1,245 control patients with normoalbuminuria]. The association of these SNPs with diabetic nephropathy was examined by using a logistic regression analysis. RESULTS: We observed a significant association of rs7588550 in ERBB4 with diabetic nephropathy in the Japanese patients with type 2 diabetes, although the effect direction was not consistent with that in the European study [p = 0.0126, odds ratio (OR) = 0.79, 95 % confidence interval (CI): 0.65-0.95]. We further examined the association of rs7588550 with diabetic nephropathy in an independent Japanese cohort (596 nephropathy cases and 311 controls) and observed the same trend of the association with the initial study. We did not observe any association of the remaining 2 SNP loci with diabetic nephropathy in the present Japanese sample. CONCLUSION: The association of SNP loci derived from GWAS in European type 1 diabetes with diabetic nephropathy was not replicated in the Japanese patients with type 2 diabetes, although the ERBB4 locus may have some effect also in Japanese type 2 diabetes.

The influence of a single nucleotide polymorphism within CNDP1 on susceptibility to diabetic nephropathy in Japanese women with type 2 diabetes.

BACKGROUND: Several linkage analyses have mapped a susceptibility locus for diabetic nephropathy to chromosome 18q22-23, and polymorphisms within the carnosine dipeptidase 1 gene (CNDP1), located on 18q22.3, have been shown to be associated with diabetic nephropathy in European subjects with type 2 diabetes. However, the association of this locus with diabetic nephropathy has not been evaluated in the Japanese population. In this study, we examined the association of polymorphisms within the CNDP1/CNDP 2 locus with diabetic nephropathy in Japanese subjects with type 2 diabetes. METHODOLOGY/PRINCIPAL FINDINGS: We genotyped a leucine repeat polymorphism (D18S880) that is within CNDP1 along with 29 single nucleotide polymorphisms (SNPs) in the CNDP1/CNDP2 locus for 2,740 Japanese subjects with type 2 diabetes (1,205 nephropathy cases with overt nephropathy or with end-stage renal disease [ESRD], and 1,535 controls with normoalbuminuria). The association of each polymorphism with diabetic nephropathy was analysed by performing logistic regression analysis. We did not observe any association between D18S880 and diabetic nephropathy in Japanese subjects with type 2 diabetes. None of the 29 SNPs within the CNDP1/CNDP2 locus were associated with diabetic nephropathy, but a subsequent sex-stratified analysis revealed that 1 SNP in CNDP1 was nominally associated with diabetic nephropathy in women (rs12604675-A; p = 0.005, odds ratio [OR] = 1.76, 95% confidence interval [CI], 1.19-2.61). Rs12604675 was associated with overt proteinuria (p = 0.002, OR = 2.18, 95% CI, 1.32-3.60), but not with ESRD in Japanese women with type 2 diabetes. CONCLUSIONS/SIGNIFICANCE: Rs12604675-A in CNDP1 may confer susceptibility to overt proteinuria in Japanese women with type 2 diabetes.

The predictive value of attenuated proteinuria at 1 year after steroid therapy for renal survival in patients with IgA nephropathy.

BACKGROUND: The relationship between the urinary protein excretion (UPE) initially achieved after steroid therapy and the long-term renal outcome of IgA nephropathy (IgAN) has not been clarified. We investigated the threshold UPE at 1 year after steroid therapy which predicts a favorable renal survival. METHODS: We enrolled 141 IgAN patients who received 6 months of steroid therapy. The endpoint was defined as a 50 % increase in serum creatinine from baseline. The spline model was used to define the threshold UPE predicting renal survival. RESULTS: Thirteen patients (9.2 %) reached the endpoint at a median follow-up of 3.8 years. When evaluating the relative hazard ratio (HR) of the UPE at 1 year for the endpoint, we found an inflection point at 0.40 g/day on the spline curve. The multivariate Cox model revealed that, in addition to the Disappeared category of UPE (range <0.30 g/day), the Mild category (range 0.30-0.39 g/day) was associated with more reduced risk of the endpoint [HR 0.02, 95 % confidence intervals (CI) 0.00-0.29] relative to the Severe category (range ≥1.00 g/day), whereas the Moderate category (range 0.40-0.99 g/day) was not. The estimated glomerular filtration rate <60 ml/min/1.73 m(2) was also an independent predictor of the endpoint. When renal survival was adjusted with pathological parameters in the Cox model, UPE <0.40 g/day was still an independent favorable predictor (HR 0.08, 95 % CI 0.01-0.45). CONCLUSIONS: In IgAN patients receiving 6 months of steroid therapy, the achievement of proteinuria <0.4 g/day at 1 year could be a therapeutic indicator for a favorable renal outcome.

Successful treatment of adult IgA nephropathy with nephrotic-level proteinuria by combination therapy including long-term coadministration of mizoribine.

A 41-year-old male patient was admitted to our hospital due to massive proteinuria and hematuria. His 24-hour urinary protein excretion and the number of urinary erythrocytes were 3.91 g/day and 50-99/high-power field, respectively. A renal biopsy showed a severe pathological pattern of immunoglobulin A nephropathy (IgAN) that involved marked endocapillary proliferation and segmental sclerosis (Oxford-MEST score: M0, E1, S1, T0). Because he had nephrotic-level proteinuria with severe pathological findings, which are tonsillectomy and corticosteroid pulse therapy-resistant characteristics, he received mizoribine for a long period as part of the combination therapy using corticosteroid, tonsillectomy, dipyridamole, warfarin and renin-angiotensin-aldosterone system blockers. Twelve months after the beginning of treatment, his urinary findings were normal. In this report, we describe the pathological findings and successful treatment course, and discuss the potential effects of long-term coadministration of mizoribine for adult IgAN treatment.

Characteristics of spontaneous calcium oscillations in renal tubular epithelial cells.

BACKGROUND: The kidney is a major organ involved in calcium (Ca(2+)) metabolism. Ca(2+) is transported through renal tubular epithelial cells. The intracellular free calcium concentration ([Ca(2+)](i)) is tightly controlled at a low concentration, but transient increases and oscillations in [Ca(2+)](i) are induced by various conditions. In this study, we investigated the mechanisms underlying the spontaneous [Ca(2+)](i) oscillations observed in MDCK cells. METHODS: [Ca(2+)](i) was monitored in fura-2-loaded Madin-Darby canine kidney (MDCK) cells using a calcium imaging system. We investigated the mechanism by which [Ca(2+)](i) changed by applying drugs or by changing the extracellular Ca(2+) concentration. RESULTS: Spontaneous [Ca(2+)](i) oscillations occurred in MDCK cells. The oscillations occurred irregularly and were not transmitted to neighboring cells. Spontaneous [Ca(2+)](i) oscillations in MDCK cells were initiated by Ca(2+) release from ryanodine/IP(3)-sensitive intracellular calcium stores, and their frequency was largely unaffected by the extracellular Ca(2+) concentration. Moreover, the frequency of the oscillations was increased by extracellular nucleotide, but was decreased when the nucleotides were removed. CONCLUSIONS: Our study suggested that [Ca(2+)](i) release from ryanodine/IP(3)-sensitive intracellular calcium stores mediates spontaneous [Ca(2+)](i) oscillations in MDCK cells. Calcium oscillations may be associated with the function of the renal tubular epithelial cells.