Sevinç Emre

Strict blood-pressure control and progression of renal failure in children.

BACKGROUND Although inhibition of the renin-angiotensin system delays the progression of renal failure in adults with chronic kidney disease, the blood-pressure target for optimal renal protection is controversial. We assessed the long-term renoprotective effect of intensified blood-pressure control among children who were receiving a fixed high dose of an angiotensin-converting-enzyme (ACE) inhibitor. METHODS After a 6-month run-in period, 385 children, 3 to 18 years of age, with chronic kidney disease (glomerular filtration rate of 15 to 80 ml per minute per 1.73 m(2) of body-surface area) received ramipril at a dose of 6 mg per square meter of body-surface area per day. Patients were randomly assigned to intensified blood-pressure control (with a target 24-hour mean arterial pressure below the 50th percentile) or conventional blood-pressure control (mean arterial pressure in the 50th to 95th percentile), achieved by the addition of antihypertensive therapy that does not target the renin-angiotensin system; patients were followed for 5 years. The primary end point was the time to a decline of 50% in the glomerular filtration rate or progression to end-stage renal disease. Secondary end points included changes in blood pressure, glomerular filtration rate, and urinary protein excretion. RESULTS A total of 29.9% of the patients in the group that received intensified blood-pressure control reached the primary end point, as assessed by means of a Kaplan-Meier analysis, as compared with 41.7% in the group that received conventional blood-pressure control (hazard ratio, 0.65; confidence interval, 0.44 to 0.94; P=0.02). The two groups did not differ significantly with respect to the type or incidence of adverse events or the cumulative rates of withdrawal from the study (28.0% vs. 26.5%). Proteinuria gradually rebounded during ongoing ACE inhibition after an initial 50% decrease, despite persistently good blood-pressure control. Achievement of blood-pressure targets and a decrease in proteinuria were significant independent predictors of delayed progression of renal disease. CONCLUSIONS Intensified blood-pressure control, with target 24-hour blood-pressure levels in the low range of normal, confers a substantial benefit with respect to renal function among children with chronic kidney disease. Reappearance of proteinuria after initial successful pharmacologic blood-pressure control is common among children who are receiving long-term ACE inhibition. (ClinicalTrials.gov number, NCT00221845.)

MYO1E Mutations and Childhood Familial Focal Segmental Glomerulosclerosis

BACKGROUND Focal segmental glomerulosclerosis is a kidney disease that is manifested as the nephrotic syndrome. It is often resistant to glucocorticoid therapy and progresses to end-stage renal disease in 50 to 70% of patients. Genetic studies have shown that familial focal segmental glomerulosclerosis is a disease of the podocytes, which are major components of the glomerular filtration barrier. However, the molecular cause in over half the cases of primary focal segmental glomerulosclerosis is unknown, and effective treatments have been elusive. METHODS We performed whole-genome linkage analysis followed by high-throughput sequencing of the positive-linkage area in a family with autosomal recessive focal segmental glomerulosclerosis (index family) and sequenced a newly discovered gene in 52 unrelated patients with focal segmental glomerulosclerosis. Immunohistochemical studies were performed on human kidney-biopsy specimens and cultured podocytes. Expression studies in vitro were performed to characterize the functional consequences of the mutations identified. RESULTS We identified two mutations (A159P and Y695X) in MYO1E, which encodes a nonmuscle class I myosin, myosin 1E (Myo1E). The mutations in MYO1E segregated with focal segmental glomerulosclerosis in two independent pedigrees (the index family and Family 2). Patients were homozygous for the mutations and did not have a response to glucocorticoid therapy. Electron microscopy showed thickening and disorganization of the glomerular basement membrane. Normal expression of Myo1E was documented in control human kidney-biopsy specimens in vivo and in glomerular podocytes in vitro. Transfection studies revealed abnormal subcellular localization and function of the A159P-Myo1E mutant. The Y695X mutation causes loss of calmodulin binding and of the tail domains of Myo1E. CONCLUSIONS MYO1E mutations are associated with childhood-onset, glucocorticoid-resistant focal segmental glomerulosclerosis. Our data provide evidence of a role of Myo1E in podocyte function and the consequent integrity of the glomerular filtration barrier.

Circulating suPAR in Two Cohorts of Primary FSGS

Overexpression of soluble urokinase receptor (suPAR) causes pathology in animal models similar to primary FSGS, and one recent study demonstrated elevated levels of serum suPAR in patients with the disease. Here, we analyzed circulating suPAR levels in two cohorts of children and adults with biopsy-proven primary FSGS: 70 patients from the North America-based FSGS clinical trial (CT) and 94 patients from PodoNet, the Europe-based consortium studying steroid-resistant nephrotic syndrome. Circulating suPAR levels were elevated in 84.3% and 55.3% of patients with FSGS patients in the CT and PodoNet cohorts, respectively, compared with 6% of controls (P<0.0001); inflammation did not account for this difference. Multiple regression analysis suggested that lower suPAR levels associated with higher estimated GFR, male sex, and treatment with mycophenolate mofetil. In the CT cohort, there was a positive association between the relative reduction of suPAR after 26 weeks of treatment and reduction of proteinuria, with higher odds for complete remission (P=0.04). In the PodoNet cohort, patients with an NPHS2 mutation had higher suPAR levels than those without a mutation. In conclusion, suPAR levels are elevated in geographically and ethnically diverse patients with FSGS and do not reflect a nonspecific proinflammatory milieu. The associations between a change in circulating suPAR with different therapeutic regimens and with remission support the role of suPAR in the pathogenesis of FSGS.

SIX2 and BMP4 Mutations Associate With Anomalous Kidney Development

Renal hypodysplasia (RHD) is characterized by reduced kidney size and/or maldevelopment of the renal tissue following abnormal organogenesis. Mutations in renal developmental genes have been identified in a subset of affected individuals. Here, we report the first mutations in BMP4 and SIX2 identified in patients with RHD. We detected 3 BMP4 mutations in 5 RHD patients, and 3 SIX2 mutations in 5 different RHD patients. Overexpression assays in zebrafish demonstrated that these mutations affect the function of Bmp4 and Six2 in vivo. Overexpression of zebrafish six2.1 and bmp4 resulted in dorsalization and ventralization, respectively, suggesting opposing roles in mesendoderm formation. When mutant constructs containing the identified human mutations were overexpressed instead, these effects were attenuated. Morpholino knockdown of bmp4 and six2.1 affected glomerulogenesis, suggesting specific roles for these genes in the formation of the pronephros. In summary, these studies implicate conserved roles for Six2 and Bmp4 in the development of the renal system. Defects in these proteins could affect kidney development at multiple stages, leading to the congenital anomalies observed in patients with RHD.

Hemostatic problems and thromboembolic complications in nephrotic children.

Abstract A hypercoagulable state and the risk of thromboembolism in both arterial and venous circulation is a relatively frequent and serious feature of nephrotic syndrome (NS) in children and adults. The aim of this study was to evaluate the coagulation states of children with NS before and after corticosteroid (CS) therapy and to compare the results with a healthy control group. The first group consisted of 49 nephrotic children (30 boys and 19 girls) with a mean age of 6.5±4.9 years (range 1–16 years). The control group included 17 healthy children (9 boys and 8 girls). At the time of admission, all patients were evaluated for the presence of clinical thromboembolism, hematological and biochemical indicators of a hypercoagulative state, and renal disease. This was repeated after CS treatment. Deep vein thrombosis was observed in 2 nephrotic patients who had very low plasma antithrombin III (AT III) levels and fibrinogen levels above 750 mg/dl. Thus, the prevalence of thromboembolism was 4% in our pediatric nephrotic population. The mean AT III level of the study group was 68.2±23.4% at the onset of the disease, which was significantly lower than the level of the control group (84.0±7.6%). Plasma AT III levels increased to 74.4±15.3% after CS treatment, which correlated with the serum albumin levels. However, there was no correlation with urinary protein excretion. Protein C levels were higher than controls during all stages of the disease in both steroid-responsive and -unresponsive patients. The mean protein S level was similar in both groups. Plasma fibrinogen and cholesterol levels were significantly higher in the study group but decreased to within normal limits with remission. Our study suggests that thromboembolic complications are not infrequent in children with NS, and may be related to low plasma AT III and albumin and high fibrinogen and cholesterol levels.

Lupus Nephritis in Children: Prognostic Significance of Clinicopathological Findings

Background: We aimed to review our experience with childhood lupus nephritis (LN) in respect to the analysis of the clinical and histopathological presentation of LN and prognostic factors affecting the kidney and patient outcomes. Method: Forty-three children (39 girls, 4 boys) with biopsy-proven LN were included in the study. The mean age of the children was 12.0 ± 2.8 years. Based on the renal histopathology and clinical presentation, patients were treated with oral prednisone, intravenous pulses of methylprednisolone or intravenous cyclophosphamide. The final clinical status was classified as follows: (1) renal and extrarenal remission; (2) clinically active renal disease, or (3) adverse outcome, i.e., end-stage renal failure (ESRF) or death. Results: The mean duration of follow-up was 7.2 ± 2.8 years (1 month to 14.2 years). All 43 children had hematuria and 53.5% had proteinuria at admission. Fourteen children were in nephrotic status at the onset of disease. Class IV (diffuse proliferative) nephritis was observed in 29 patients as the most frequent histopathology (67.4%). The patients with class IV nephritis had a tendency to develop nephrotic syndrome, heavy proteinuria, increased Cr levels and persistent hypertension at initial evaluation. Thirty-two of 43 children (74.4%) were in renal remission at the last visit. Five-year kidney and patient survival rates from the time of diagnosis to the endpoints of ESRF or death were 83.7 and 90.7% respectively in the whole group while it was 75.9 and 86.2% respectively in the class IV group. Adverse outcome was significantly associated with the persistent hypertension, anemia, high serum Cr level, heavy proteinuria, nephrotic syndrome and class IV nephritis at presentation. Conclusion: We can conclude that the prognosis of LN in children is primarily dependent on the histopathological lesions. Severity of the clinical renal disease at admission and presence of persistent hypertension are the main poor prognostic factors rather than age, gender, low C3 and C4 levels, ANA positivity and the treatment modalities in Turkish children.

Etiology of chronic renal failure in Turkish children

The etiology of chronic renal failure (CRF) was studied in 459 Turkish children (205 girls, 254 boys) for the period January 1979-December 1993. Their mean age at onset of CRF was 9.5±4.2 years (range 1–16 years); CRF was defined as a glomerular filtration rate (GFR) below 50 ml/min per 1.73 m2 for at least 6 months. When a GFR determination was not available, the serum creatinine concentration was used: greater than 1 mg/dl for children aged 1–3 years, greater than 1.5 mg/dl for those 3–10 years and greater than 2 mg/dl for those 10–16 years. Primary renal disorders were as follows: reflux nephropathy 32.4% glomerular diseases 22.2%, hereditary renal disorders 11.4%, amyloidosis 10.6%, urinary stones 8% and other renal disorders 15.4%. Twenty-three cases of reflux nephropathy (15.4%) were associated with neural tube defects (NTD) and 20 (13.4%) were caused by infravesical obstruction. CRF caused vesicoureteral reflux associated with NTD and amyloidosis are more frequent in our series compared with west European and Nordic countries.

Genetic screening in adolescents with steroid-resistant nephrotic syndrome

Genetic screening paradigms for congenital and infantile nephrotic syndrome are well established; however, screening in adolescents has received only minor attention. To help rectify this, we analyzed an unselected adolescent cohort of the international PodoNet registry to develop a rational screening approach based on 227 patients with nonsyndromic steroid-resistant nephrotic syndrome aged 10-20 years. Of these, 21% had a positive family history. Autosomal dominant cases were screened for WT1, TRPC6, ACTN4, and INF2 mutations. All other patients had the NPHS2 gene screened, and WT1 was tested in sporadic cases. In addition, 40 sporadic cases had the entire coding region of INF2 tested. Of the autosomal recessive and the sporadic cases, 13 and 6%, respectively, were found to have podocin-associated nephrotic syndrome, and 56% of them were compound heterozygous for the nonneutral p.R229Q polymorphism. Four percent of the sporadic and 10% of the autosomal dominant cases had a mutation in WT1. Pathogenic INF2 mutations were found in 20% of the dominant but none of the sporadic cases. In a large cohort of adolescents including both familial and sporadic disease, NPHS2 mutations explained about 7% and WT1 4% of cases, whereas INF2 proved relevant only in autosomal dominant familial disease. Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.

Frequency of renal malformations in Turner syndrome: analysis of 82 Turkish children

Abstract We evaluated the frequency of renal malformations in relation to nonmosaic 45,X (group A, 45 patients, 54.9%) and mosaic/structural abnormalities of X (group B, 37 patients, 45.1%) in 82 Turkish patients with Turner syndrome (TS). Ultrasonography of the kidneys and collecting system was performed in all patients. Of the 82 patients, 31 had different renal malformations (37.8%). Horse-shoe kidney was observed in 9 (29.0%) of the 31 patients, and 17 patients (54.8%) had various collecting system malformations, while 5 (16.2%) had malrotation and other positional abnormalities. The prevalence of renal malformations was significantly higher in group A (51.1%) than group B (21.6%) (2:7.94, P<0.05). Although 8 of the 9 patients with horse-shoe kidney had the 45,X karyotype, collecting system malformations were observed more frequently in group B. Recurrent urinary tract infections (UTIs) were detected during follow-up in 7 patients, and hypertension developed in 3 patients. In patients who had a normal baseline nephrological evaluation, no problem suggesting renal disease developed during follow-up. We conclude that all forms of TS should have routine nephrological screening on diagnosis, since structural malformations of the kidney occur more frequently in nonmosaic 45,X TS, while collecting system malformations are mostly seen in mosaic/structural X forms. Those included in the group for nephrological follow-up had an increased risk for hypertension and/or UTI.

Superior consistency of ambulatory blood pressure monitoring in children: implications for clinical trials.

Background Casual office blood pressure (CBP) measurements are still standard in antihypertensive drug trials. In pediatric hypertensive trials, ethical considerations, very low disease prevalence and the marked impact of white-coat hypertension create the need for very sensitive and reproducible techniques of BP assessment. We hypothesized that ambulatory BP monitoring (ABPM) may identify treatment effects more sensitively than CBP and thereby reduce sample sizes required in pediatric antihypertensive trials. Methods Standard deviations (SDs) were used to assess population variability of CBP and ABPM at baseline and after 6 months standardized antihypertensive treatment from a trial investigating the BP-lowering effect of ramipril in children with chronic kidney disease. Results In 157 hypertensive children, ramipril had a similar mean BP-lowering effect on clinic and ambulatory 24-h BP for systolic (−10 vs. −11 mmHg, P = NS) and diastolic values (−9 vs. −11 mmHg, P = NS). However, the SDs of the CBP responses were up to 39% larger than those of ABPM (SBP 15.5 vs. 9.4; DBP 13.8 vs. 8.8; both P < 0.0001). Using power analysis, we demonstrate that, depending on the magnitude of the expected antihypertensive effect and trial design, the utilization of ABPM in antihypertensive drug efficacy studies allows reduction of sample sizes by 57–75%. This reduction of cohort size with ABPM is substantially greater than previously observed for adults. Conclusion The primary use of ABPM can substantially reduce the number of children put at potential risk in blinded antihypertensive drug trials by up to three quarters.