Anti-glutathione S-transferase theta 1 antibodies correlate with graft loss in non-sensitized pediatric kidney recipients

Introduction

Immunity to Human leukocyte antigen (HLA) cannot explain all cases of ABMR, nor the differences observed in the outcome of kidney recipients with circulating DSAs endowed with similar biologic characteristics. Thus, increasing attention has recently been focused on the role of immunity to non-HLA antigenic targets.

Methods

We analyzed humoral auto- and alloimmune responses to the non-HLA antigen glutathione S-transferase theta 1 (GSTT1), along with development of de novo (dn)HLA-DSAs, in a cohort of 146 pediatric non-sensitized recipients of first kidney allograft, to analyze its role in ABMR and graft loss. A multiplex bead assay was employed to assess GSTT1 antibodies (Abs).

Results

We observed development of GSTT1 Abs in 71 recipients after transplantation, 16 with MFI > 8031 (4th quartile: Q4 group). In univariate analyses, we found an association between Q4-GSTT1Abs and ABMR and graft loss, suggesting a potential role in inducing graft damage, as GSTT1 Abs were identified within ABMR biopsies of patients with graft function deterioration in the absence of concomitant intragraft HLA-DSAs. HLA-DSAs and GSTT1 Abs were independent predictors of graft loss in our cohort. As GSTT1 Ab development preceded or coincided with the appearance of dnHLA-DSAs, we tested and found that a model with the two combined parameters proved more fit to classify patients at risk of graft loss.

Discussion

Our observations on the harmful effects of GSTT1Abs, alone or in combination with HLA-DSAs, add to the evidence pointing to a negative role of allo- and auto-non-HLA Abs on kidney graft outcome.

FC040: Kidney Transplantation in Childhood-Onset ANCA-Associated Vasculitis: Outcomes in a Multicentre Cohort

BACKGROUND AND AIMS

ANCA-associated vasculitis (AAV) is rare among children but leads to kidney failure (KF) in almost 30% of cases with renal involvement [1]. Kidney transplantation (KT) is the treatment of choice in adults with AAV and KF, while data among children are limited to small case series [2, 3]. We report the outcomes of KT in a multicentre cohort of patients with childhood-onset AAV.

METHOD

Patients with AAV diagnosed before the age of 18 years who had undergone KT were identified at one Canadian and 20 European centres. We analysed patient and graft survival and the rates of rejection, AAV relapse and infections. Eighteen patients from this cohort had already been reported in previous articles [1, 2]; their follow-up was extended and further relevant data were retrieved.

RESULTS

We included 55 patients, of whom 38 (69%) had microscopic polyangiitis (MPA) and 17 (31%) granulomatosis with polyangiitis (GPA). Their median age at diagnosis and transplantation was, respectively, 12 (interquartile range, IQR 9–14) and 14 (IQR 12–16) years (Table 1). Living donor transplantation was performed in 20 cases (36%) and deceased donor transplantation in 35 (64%). At the time of transplantation, all patients were in clinical remission and ANCA was positive in 14/54 (26%). As immunosuppressive therapy, 46 patients (84%) received glucocorticoids, tacrolimus and either mycophenolate mofetil or azathioprine.

The median follow-up after transplantation was 54 months (IQR 21–91). Acute rejection was reported in 22 patients (40%), 12 of whom experienced it during the first post-transplant year, while chronic rejection was established in two (4%). AAV relapsed in five cases (9%) and involved the graft in 4/5. Positive ANCA at transplantation was significantly associated with relapse (29% versus 2%; P = 0.02). Infections occurred in 34 patients (62%), and were mainly bacterial infections of the urinary tract or viral infections due to CMV (8/34), EBV (5/34) and BK virus (4/34). No patient developed malignancy. At last visit, all patients were alive and 48 (87%) had a functioning graft. Graft function impairment (eGFR <60 mL/min/1.73 m2) developed in 21 patients and seven (13%) of these lost their graft due to acute (6/7) and chronic rejection (1/7). Outcomes and complication rates did not differ significantly between the MPA and the GPA group (Table 1). Graft function impairment was associated with rejection and positive ANCA at transplantation, but not with age at diagnosis and at transplantation, ANCA specificity, the type of donor or the immunosuppressive regimen (Figure. 1).

CONCLUSION

KT in childhood-onset AAV has a relatively good graft and patient survival, while the rate of complications and the risk of vasculitis relapse appear low. Positive ANCA at the time of transplantation may be a risk factor for both AAV relapse and graft function impairment.

Post-transplant de novo non donor-specific HLA antibodies are not associated with poor graft outcome in non-sensitized pediatric recipients of kidney transplantation

While de novo donor-specific HLA antibodies (dnDSAs) have a detrimental impact on kidney graft outcome, the clinical significance of de novo non donor-specific antibodies (dnNDSAs) is more controversial. We retrospectively evaluated for Ab development and characteristics of dnNDSAs serially collected post-transplant sera and, when available, graft biopsy eluates, from 144 non-sensitized, primary pediatric kidney recipients, consecutively transplanted at a single center between 2003 and 2017, using HLA class I and class II single-antigen flow-bead assays (SAB). The results were compared with clinical-pathologic data from HLA antibody negative and HLA dnDSA-positive patients. Forty-five out of 144 patients developed dnNDSAs (31%). Among the dnNDSA-positive patients, 86% displayed one or more class I/II antibodies recognizing antigens included in the CREG/shared epitope groups that also comprise the mismatched donor HLA antigens. Despite potential pathogenicity, as suggested by their occasional presence within the graft, dnNDSAs displayed significantly lower MFI, and limited complement binding and graft homing properties, when compared with dnDSAs. In parallel, the graft survival probability was significantly lower in patients with dnDSA than in those with dnNDSA or without HLA antibodies (p < 0.005). Indeed, the dnNDSA-positive patients remaining dnDSA-negative throughout the posttransplant period did not develop clinical antibody mediated rejection and graft loss, and maintained good graft function at a median follow-up of 9 years. The biological characteristics of dnNDSAs may account for the low graft damaging capability when compared to dnDSAs.

Nutritional Status in Children Receiving Chronic Peritoneal Dialysis

Chronic peritoneal dialysis (CPD), widely used in uremic children, may have contrasting effects on the nutritional status of patients. Metabolic and nutritional abnormalities due to the combined effects of uremia per se, glucose absorption from the dialysate and catabolic factors, such as protein and amino acid losses into dialysate, poor appetite, and recurrent episodes of peritonitis are the most important.

Although CPD allows for fewer dietary restrictions and supplies an extra amount of calories by glucose absorbed with the peritoneal fluid, when protein and energy intakes are assessed the protein intake was almost sufficient or more than that prescribed, whereas the energy intake was low.

In CPD children the standard deviation score for weight, height, triceps skinfold thickness, and midarm circumference has been reported as more severely impaired in children less than ten years old. Anthropometric parameters did not worsen during CPD treatment.

Plasma proteins and albumin are reported as being low in CPD children. The dietary intake and protein losses have been considered to be the most important determinants of the albumin level in CPD patients.

The reported average dialysate losses of free amino acids (AA) during CPD in children vary from 0.02 to 0.03 g/kg/day in different studies. The patterns of plasma AA in CPD is represented by reduced levels of branched chain AA and of other essential amino acids and increased concentrations of some nonessential AA. Several factors may influence plasma AA profile: uremia per se, hormonal alterations, protein and AA losses, and dietary intake. A more specific uremic AA pattern is found in muscle, the largest pool of free AA in the body. Studies on muscle AA in adults on CPD are conflicting: some authors have reported several muscle AA alterations, but others have shown an almost normal pattern. Low valine and leucine muscle levels have been reported in children on CPD.

Failure to remove de novo donor-specific HLA antibodies is influenced by antibody properties and identifies kidney recipients with late antibody-mediated rejection destined to graft loss - a retrospective study

Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody-mediated rejection (AMR). We retrospectively investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor-specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low-dose IVIG + Rituximab or high-dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow-up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d-binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti-humoral treatment. In the multivariable analysis, C3d-binding ability (P < 0.05), but not C1q-binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high-MFI DSAs.

The Italian Society for Pediatric Nephrology (SINePe) consensus document on the management of nephrotic syndrome in children: Part I - Diagnosis and treatment of the first episode and the first relapse

This consensus document is aimed at providing an updated, multidisciplinary overview on the diagnosis and treatment of pediatric nephrotic syndrome (NS) at first presentation. It is the first consensus document of its kind to be produced by all the pediatric nephrology centres in Italy, in line with what is already present in other countries such as France, Germany and the USA. It is based on the current knowledge surrounding the symptomatic and steroid treatment of NS, with a view to providing the basis for a separate consensus document on the treatment of relapses. NS is one of the most common pediatric glomerular diseases, with an incidence of around 2-7 cases per 100000 children per year. Corticosteroids are the mainstay of treatment, but the optimal therapeutic regimen for managing childhood idiopathic NS is still under debate. In Italy, shared treatment guidelines were lacking and, consequently, the choice of steroid regimen was based on the clinical expertise of each individual unit. On the basis of the 2015 Cochrane systematic review, KDIGO Guidelines and more recent data from the literature, this working group, with the contribution of all the pediatric nephrology centres in Italy and on the behalf of the Italian Society of Pediatric Nephrology, has produced a shared steroid protocol that will be useful for National Health System hospitals and pediatricians. Investigations at initial presentation and the principal causes of NS to be screened are suggested. In the early phase of the disease, symptomatic treatment is also important as many severe complications can occur which are either directly related to the pathophysiology of the underlying NS or to the steroid treatment itself. To date, very few studies have been published on the prophylaxis and treatment of these early complications, while recommendations are either lacking or conflicting. This consensus provides indications for the prevention, early recognition and treatment of these complications (management of edema and hypovolemia, therapy and prophylaxis of infections and thromboembolic events). Finally, recommendations about the clinical definition of steroid resistance and its initial diagnostic management, as well as indications for renal biopsy are provided.

Infants Requiring Maintenance Dialysis: Outcomes of Hemodialysis and Peritoneal Dialysis

BACKGROUND

The impact of different dialysis modalities on clinical outcomes has not been explored in young infants with chronic kidney failure.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

Data were extracted from the ESPN/ERA-EDTA Registry. This analysis included 1,063 infants 12 months or younger who initiated dialysis therapy in 1991 to 2013.

FACTOR

Type of dialysis modality.

OUTCOMES & MEASUREMENTS

Differences between infants treated with peritoneal dialysis (PD) or hemodialysis (HD) in patient survival, technique survival, and access to kidney transplantation were examined using Cox regression analysis while adjusting for age at dialysis therapy initiation, sex, underlying kidney disease, and country of residence.

RESULTS

917 infants initiated dialysis therapy on PD, and 146, on HD. Median age at dialysis therapy initiation was 4.5 (IQR, 0.7-7.9) months, and median body weight was 5.7 (IQR, 3.7-7.5) kg. Although the groups were homogeneous regarding age and sex, infants treated with PD more often had congenital anomalies of the kidney and urinary tract (CAKUT; 48% vs 27%), whereas those on HD therapy more frequently had metabolic disorders (12% vs 4%). Risk factors for death were younger age at dialysis therapy initiation (HR per each 1-month later initiation, 0.95; 95% CI, 0.90-0.97) and non-CAKUT cause of chronic kidney failure (HR, 1.49; 95% CI, 1.08-2.04). Mortality risk and likelihood of transplantation were equal in PD and HD patients, whereas HD patients had a higher risk for changing dialysis treatment (adjusted HR, 1.64; 95% CI, 1.17-2.31).

LIMITATIONS

Inability to control for unmeasured confounders not included in the Registry database and missing data (ie, comorbid conditions). Low statistical power because of relatively small number of participants.

CONCLUSIONS

Despite a widespread preconception that HD should be reserved for cases in which PD is not feasible, in Europe, we found 1 in 8 infants in need of maintenance dialysis to be initiated on HD therapy. Patient characteristics at dialysis therapy initiation, prospective survival, and time to transplantation were very similar for infants initiated on PD or HD therapy.

Acquisition of C3d-Binding Activity by De Novo Donor-Specific HLA Antibodies Correlates With Graft Loss in Nonsensitized Pediatric Kidney Recipients

Alloantibody-mediated graft injury is a major cause of kidney dysfunction and loss. The complement-binding ability of de novo donor-specific antibodies (dnDSAs) has been suggested as a prognostic tool to stratify patients for clinical risk. In this study, we analyzed posttransplant kinetics of complement-fixing dnDSAs and their role in antibody-mediated rejection development and graft loss. A total of 114 pediatric nonsensitized recipients of first kidney allograft were periodically monitored for dnDSAs using flow bead assays, followed by C3d and C1q assay in case of positivity. Overall, 39 patients developed dnDSAs, which were C1q(+) and C3d(+) in 25 and nine patients, respectively. At follow-up, progressive acquisition over time of dnDSA C1q and C3d binding ability, within the same antigenic specificity, was observed, paralleled by an increase in mean fluorescence intensity that correlated with clinical outcome. C3d-fixing dnDSAs were better fit to stratify graft loss risk when the different dnDSA categories were evaluated in combined models because the 10-year graft survival probability was lower in patients with C3d-binding dnDSA than in those without dnDSAs or with C1q(+) /C3d(-) or non-complement-binding dnDSAs (40% vs. 94%, 100%, and 100%, respectively). Based on the kinetics profile, we favor dnDSA removal or modulation at first confirmed positivity, with treatment intensification guided by dnDSA biological characteristics.

Normal 25-Hydroxyvitamin D Levels Are Associated with Less Proteinuria and Attenuate Renal Failure Progression in Children with CKD

Angiotensin-converting enzyme inhibitors (ACEi) for renin-angiotensin-aldosterone system (RAAS) blockade are routinely used to slow CKD progression. However, vitamin D may also promote renoprotection by suppressing renin transcription through cross-talk between RAAS and vitamin D-fibroblast growth factor-23 (FGF-23)-Klotho pathways. To determine whether vitamin D levels influence proteinuria and CKD progression in children, we performed a post hoc analysis of the Effect of Strict Blood Pressure Control and ACE Inhibition on Progression of CKD in Pediatric Patients (ESCAPE) cohort. In 167 children (median eGFR 51 ml/min per 1.73 m(2)), serum 25-hydroxyvitamin D (25(OH)D), FGF-23, and Klotho levels were measured at baseline and after a median 8 months on ACEi. Children with lower 25(OH)D levels had higher urinary protein/creatinine ratios at baseline (P=0.03) and at follow-up (P=0.006). Levels of 25(OH)D and serum vitamin D-binding protein were not associated, but 25(OH)D ≤50 nmol/L associated with higher diastolic BP (P=0.004). ACEi therapy also associated with increased Klotho levels (P<0.001). The annualized loss of eGFR was inversely associated with baseline 25(OH)D level (P<0.001, r=0.32). Five-year renal survival was 75% in patients with baseline 25(OH)D ≥50 nmol/L and 50% in those with lower 25(OH)D levels (P<0.001). This renoprotective effect remained significant but attenuated with ACEi therapy (P=0.05). Renal survival increased 8.2% per 10 nmol/L increase in 25(OH)D (P=0.03), independent of eGFR; proteinuria, BP, and FGF-23 levels; and underlying renal diagnosis. In children with CKD, 25(OH)D ≥50 nmol/L was associated with greater preservation of renal function. This effect was present but attenuated with concomitant ACEi therapy.

Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome

BACKGROUND

Atypical hemolytic-uremic syndrome is a genetic, life-threatening, chronic disease of complement-mediated thrombotic microangiopathy. Plasma exchange or infusion may transiently maintain normal levels of hematologic measures but does not treat the underlying systemic disease.

METHODS

We conducted two prospective phase 2 trials in which patients with atypical hemolytic-uremic syndrome who were 12 years of age or older received eculizumab for 26 weeks and during long-term extension phases. Patients with low platelet counts and renal damage (in trial 1) and those with renal damage but no decrease in the platelet count of more than 25% for at least 8 weeks during plasma exchange or infusion (in trial 2) were recruited. The primary end points included a change in the platelet count (in trial 1) and thrombotic microangiopathy event-free status (no decrease in the platelet count of >25%, no plasma exchange or infusion, and no initiation of dialysis) (in trial 2).

RESULTS

A total of 37 patients (17 in trial 1 and 20 in trial 2) received eculizumab for a median of 64 and 62 weeks, respectively. Eculizumab resulted in increases in the platelet count; in trial 1, the mean increase in the count from baseline to week 26 was 73×10(9) per liter (P<0.001). In trial 2, 80% of the patients had thrombotic microangiopathy event-free status. Eculizumab was associated with significant improvement in all secondary end points, with continuous, time-dependent increases in the estimated glomerular filtration rate (GFR). In trial 1, dialysis was discontinued in 4 of 5 patients. Earlier intervention with eculizumab was associated with significantly greater improvement in the estimated GFR. Eculizumab was also associated with improvement in health-related quality of life. No cumulative toxicity of therapy or serious infection-related adverse events, including meningococcal infections, were observed through the extension period.

CONCLUSIONS

Eculizumab inhibited complement-mediated thrombotic microangiopathy and was associated with significant time-dependent improvement in renal function in patients with atypical hemolytic-uremic syndrome. (Funded by Alexion Pharmaceuticals; C08-002 ClinicalTrials.gov numbers, NCT00844545 [adults] and NCT00844844 [adolescents]; C08-003 ClinicalTrials.gov numbers, NCT00838513 [adults] and NCT00844428 [adolescents]).

Failure of regulation results in an amplified oxidation burst by neutrophils in children with primary nephrotic syndrome

The mechanism responsible for proteinuria in non-genetic idiopathic nephrotic syndrome (iNS) is unknown. Animal models suggest an effect of free radicals on podocytes, and indirect evidence in humans confirm this implication. We determined the oxidative burst by blood CD15+ polymorphonucleates (PMN) utilizing the 5-(and-6)-carboxy-2',7'-dichlorofluorescin diacetate (DCF-DA) fluorescence assay in 38 children with iNS. Results were compared with PMN from normal subjects and patients with renal pathologies considered traditionally to be models of oxidative stress [six anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis, seven post-infectious glomerulonephritis]. Radicals of oxygen (ROS) production was finally determined in a patient with immunodeficiency, polyendocrinopathy, enteropathy X-linked (IPEX) and in seven iNS children after treatment with Rituximab. Results demonstrated a 10-fold increase of ROS production by resting PMN in iNS compared to normal PMN. When PMN were separated from other cells, ROS increased significantly in all conditions while a near-normal production was restored by adding autologous cells and/or supernatants in controls, vasculitis and post-infectious glomerulonephritis but not in iNS. Results indicated that the oxidative burst was regulated by soluble factors and that this regulatory circuit was altered in iNS. PMN obtained from a child with IPEX produced 100 times more ROS during exacerbation of clinical symptoms and restored to a near normal-level in remission. Rituximab decreased ROS production by 60%. In conclusion, our study shows that oxidant production is increased in iNS for an imbalance between PMN and other blood cells. Regulatory T cells (Tregs) and CD20 are probably involved in this regulation. Overall, our observations reinforce the concept that oxidants deriving from PMN are implicated in iNS.

Autoimmunity in membranous nephropathy targets aldose reductase and SOD2

Glomerular targets of autoimmunity in human membranous nephropathy are poorly understood. Here, we used a combined proteomic approach to identify specific antibodies against podocyte proteins in both serum and glomeruli of patients with membranous nephropathy (MN). We detected specific anti-aldose reductase (AR) and anti-manganese superoxide dismutase (SOD2) IgG(4) in sera of patients with MN. We also eluted high titers of anti-AR and anti-SOD2 IgG(4) from microdissected glomeruli of three biopsies of MN kidneys but not from biopsies of other glomerulonephritides characterized by IgG deposition (five lupus nephritis and two membranoproliferative glomerulonephritis). We identified both antigens in MN biopsies but not in other renal pathologies or normal kidney. Confocal and immunoelectron microscopy (IEM) showed co-localization of anti-AR and anti-SOD2 with IgG(4) and C5b-9 in electron-dense podocyte immune deposits. Preliminary in vitro experiments showed an increase of SOD2 expression on podocyte plasma membrane after treatment with hydrogen peroxide. In conclusion, our data support AR and SOD2 as renal antigens of human MN and suggest that oxidative stress may drive glomerular SOD2 expression.

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.)

Clinical features and long-term outcome of nephrotic syndrome associated with heterozygous NPHS1 and NPHS2 mutations

BACKGROUND AND OBJECTIVES

Mutations in nephrin (NPHS1) and podocin (NPHS2) genes represent a major cause of idiopathic nephrotic syndrome (NS) in children. It is not yet clear whether the presence of a single mutation acts as a modifier of the clinical course of NS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We reviewed the clinical features of 40 patients with NS associated with heterozygous mutations or variants in NPHS1 (n = 7) or NPHS2 (n = 33). Long-term renal survival probabilities were compared with those of a concurrent cohort with idiopathic NS.

RESULTS

Patients with a single mutation in NPHS1 received a diagnosis before those with potentially nongenetic NS and had a good response to therapies. Renal function was normal in all cases. For NPHS2, six patients had single heterozygous mutations, six had a p.P20L variant, and 21 had a p.R229Q variant. Age at diagnosis and the response to drugs were comparable in all NS subgroups. Overall, they had similar renal survival probabilities as non-NPHS1/NPHS2 cases (log-rank chi(2) 0.84, P = 0.656) that decreased in presence of resistance to therapy (P < 0.001) and in cases with renal lesions of glomerulosclerosis and IgM deposition (P < 0.001). Cox regression confirmed that the only significant predictor of dialysis was resistance to therapy.

CONCLUSIONS

Our data indicate that single mutation or variant in NPHS1 and NPHS2 does not modify the outcome of primary NS. These patients should be treated following consolidated schemes and have good chances for a good long-term outcome.

Protracted remission of proteinuria after combined therapy with plasmapheresis and anti-CD20 antibodies/cyclophosphamide in a child with oligoclonal IgM and glomerulosclerosis

We describe a child presenting with oligoclonal plasma IgM (1.2 g%) and nephrotic syndrome with focal segmental glomerulosclerosis. Oligoclonality was demonstrated by the analysis of the complementary determining region 3 (CDR 3) on immunoglobulin heavy chains and by two dimensional electrophoresis and Western blot analysis that showed the bulk of isoforms having a cationic muU chain compared with the normal homologue (pI 7.5 vs 6.5). Urinary light chains were absent, and bone marrow aspirate was normal. Usual therapies for nephrotic syndrome with steroids and cyclosporin were useless. At the age of 9 years the patient was treated with plasmapheresis plus cyclophosphamide (2 mg/kg per day for 60 days), which temporarily reduced plasma IgM, and proteinuria was normal for 3 years. After this period, due to new recurrence of nephrotic syndrome, the patient received a cycle with anti-CD20 antibodies (500 mg/m(2) every week for a month) associated with a cycle of plasmapheresis that normalized proteinuria again, and, after 3 years, the proteinuria is still in remission. This is the first case of nephrotic syndrome associated with oligoclonal plasma IgM and mesangial IgM deposits. Both cyclophosphamide and anti-CD20 antibodies associated with plasmapheresis induced, at different stages, stable and protracted remission of proteinuria without evident side effects. Long term efficacy and safety of the association are still to be determined.

Laparoscopic-Assisted Peritoneal Dialysis Catheter Implantation in Pediatric Patients

OBJECTIVES

To assess the feasibility and complications of laparoscopic-assisted placement of peritoneal dialysis catheters (PDCs) in pediatric patients.

METHODS

A total of 15 patients undergoing laparoscopic-assisted PDC insertion were studied. A single 10-mm epigastric port was used, unless concomitant diseases were present. A double-cuffed straight Tenckhoff catheter was implanted, with the deep cuff placed within a preperitoneal tunnel underneath the left rectus muscle. The catheter tip was positioned in the left iliac fossa by stylet wire manipulation under laparoscopic control, with the exit site oriented laterally or downward. Subtotal omentectomy was performed by way of the epigastric port site. The findings were compared with those of a group of patients undergoing open PDC insertion.

RESULTS

The median operating time was not different in the two groups. In the laparoscopic group, a single port was used in 9 cases, and adhesiolysis was performed in 2. The median time to PD initiation was not different in the two groups, nor were any significant differences found in the infectious complications, leak or obstruction rates, or need for secondary surgical revisions between the two groups. Surgical revision was necessary because of peritonitis in 1, persistent leak in 1, and dislodgement in 2 in the open group and because of blockages in 3 in the laparoscopic group. Laparoscopy allowed for the rescue of two such catheters.

CONCLUSIONS

The results of our study have shown that laparoscopy allows for careful assessment of the abdominal cavity, recognition and treatment of intraabdominal diseases, and precise placement of PDCs. However, it does not seem to reduce the early catheter-related complication rate. Mechanical obstruction remains a common cause of early catheter malfunction. However, laparoscopy can allow for the rescue of blocked catheters.

Hyponatremic-hypertensive syndrome with extensive and reversible renal defects

Two young children with renal artery stenosis and severe hypertension who presented with the so-called hyponatremic-hypertensive syndrome (HHS), with marked urine and solute loss during the acute phase, are described. Both children also presented with severe high molecular proteinuria, glycosuria, and hypercalciuria, only the first symptom having prompt remission after normalization of blood pressure. In children with renal artery stenosis, HHS is associated with severe proteinuria due to hyperfiltration and more extensive tubular functional alterations. Hyponatremia and acute tubulopathy may mask the presenting clinical picture of renal artery stenosis.

Acute effects of simultaneous intraperitoneal infusion of glucose and amino acids

BACKGROUND

The feasibility of simultaneously infusing glucose and amino acid (AA)-based peritoneal dialysis solutions was tested to determine whether peritoneal dialysis patients could achieve an adequate nonprotein calorie/nitrogen ratio while preventing a marked increase in blood urea nitrogen (BUN), which is usually seen if the AAs are administered without glucose.

METHODS

An automatic peritoneal dialysis cycler was used to infuse glucose and AA solutions (3:1) simultaneously during the night. Eight infusions of 1000 mL m2 of body surface area (BSA), with a 60 minute dwell time, were performed in 10 children on peritoneal dialysis. The dialytic effluent was analyzed at every exchange and totaled at eight hours to evaluate volume, glucose, and AA concentration. Blood samples for plasma, glucose, insulin, and free AA determination were drawn at the beginning of automated peritoneal dialysis (APD) session and at each instillation of peritoneal dialysate.

RESULTS

The mean glucose absorption was 33.7 +/- 10.0% and the AA absorption was 55.2 +/- 13.2% of the infused amount, and the ratio of nonprotein calorie (derived from glucose) to nitrogen (derived from AA) was 115.4:1. The insulin levels returned to normal only three hours after the beginning of APD. The free AA plasma levels were already increased two hours after dinner and remained high for the entire APD treatment because of the continuous absorption of AA from the peritoneum. The BUN levels did not increase despite the supply of AA.

CONCLUSIONS

This APD procedure may improve utilization of AA for protein synthesis, as suggested by the lack of increase of the BUN levels with this regimen.

The use of the PD Adequest mathematical model in pediatric patients on chronic peritoneal dialysis

OBJECTIVE

To test the accuracy of the PD ADEQUEST kinetic model in calculating peritoneal transport parameters and to quantify the differences between the results of software simulations and direct measurements in order to assess the reliability of this tool in chronic peritoneal dialysis (PD) pediatric patients.

PATIENTS

Twenty-nine patients (mean age: 10 +/- 4 years; range: 4-17), 5 on continuous ambulatory PD, 4 on continuous cycling PD, 19 on nocturnal intermittent PD and 1 in nocturnal tidal PD, all free from peritonitis in the previous 2 months. Fourteen patients were anuric and 15 had a mean glomerular filtration rate of 1.79 +/- 1.23 mL/min, range 0.25-4.82.

METHODS

In all patients, 24-hour dialysate and urine collections associated to standard peritoneal equilibration test (PET) were performed using their usual dialytic regimen and fill volume (1023 +/- 159 mL/m2 BSA, range 614-1361). PD ADEQUEST kinetic parameters were compared with pediatric and adult data from literature. The measured weekly normalized total creatinine clearance (CRCL), weekly total Kt/V, and daily net ultrafiltration (UF) were compared with corresponding mathematically modeled values.

RESULTS

Kinetic parameters calculated by the PD ADEQUEST program were comparable to adult and pediatric values from previous studies after normalization for BSA. Measured and modeled CRCL and Kt/V showed a good agreement [concordance correlation (rc) 0.937 and 0.768, respectively] with limited median percentage absolute errors (11.6% and 10.2%, respectively). Ultrafiltration showed less favorable results (rc = 0.600 and median percentage absolute error 45%) probably owing to the wide variability of this parameter. When the analysis was restricted to the peritoneal component, the rc coefficients results were 0.745 for CRCL and 0.512 for Kt/V (median absolute error: 11.6% and 15.2%, respectively).

CONCLUSIONS

The overall findings of our study show that the PD ADEQUEST kinetic model can be used in pediatric patients for the calculation of kinetic indexes and for mathematical simulation of the various regimens. We also feel that the results yielded by the PD ADEQUEST program are reliable enough for this computerized mathematical model to be used in the prescription management of pediatric patients. Only UF prediction needs to be used with a certain caution on account of the marked variability of this parameter.

Effects of peritoneal effluents on mesothelial cells in culture: cell proliferation and extracellular matrix regulation

Peritoneal fibrosis in patients on peritoneal dialysis is the result of interstitial collagen accumulation within the peritoneal membrane and in mural spaces. Hypothetically, collagen expression by target cells may be regulated by specific endoperitoneal factors, though the existence of such factors has not yet been demonstrated. We evaluated the effects of cell-free peritoneal effluents obtained from six children undergoing peritoneal dialysis on several mesothelial cell functions in vitro. Human peritoneal mesothelial cells (MC) were obtained from the omental tissue of six uraemic children who were undergoing surgery for insertion of a peritoneal catheter. Cells at confluence were utilized to determine cytotoxicity (LDH release), viability (trypan blue), proliferation (3H-thymidine incorporation), collagen expression (3H-proline incorporation, SDS-Page) and mRNA (dot-blot). A preliminary series of experiments, was undertaken to define which of the successive fluid collections during a dialytic procedures induces the greatest changes; this revealed maximal effects of the effluent from the long stasis period. Exposure to peritoneal effluents obtained from four patients with acute peritonitis induced marked changes in cell morphology, stimulated by (3H)-thymidine incorporation into DNA by 300% and upregulated the expression and transcription of type III collagen (6-fold increment in COL3A1 mRNA). Qualitatively but not quantitatively comparable changes in cell proliferation (+100%) and collagen expression were induced by peritoneal effluents from patients without peritonitis. In an effort to reproduce the effect of peritoneal effluents in vitro, we exposed mesothelial cells to various cytokines putatively present in infected peritoneal effluents, namely IL-2, TGF beta and TNF alpha; in no case did we find stimulation of cell proliferation. Finally TGF beta but not TNF alpha or IL2 upregulated collagen synthesis by these cells. These findings demonstrate a direct influence of cell-free peritoneal effluents on mesothelial cell functions, including stimulation of interstitial collagen expression. All these changes were more evident upon exposure to effluents collected during acute peritonitis, which suggests a link between recurrent peritoneal infection and collagen deposition, the most typical precursor of peritoneal fibrosis.

Is the response to rhGH in peritoneal dialysis patients less effective than in patients with chronic renal insufficiency

Data on the effects of rhGH treatment in children on peritoneal dialysis are limited. In general rhGH therapy seems to be less effective compared with results on patients with chronic renal failure on conservative treatment. Our experience suggests that rhGH can stimulate growth in children on CPD, and that the efficacy of such therapy is reduced after the first year of treatment, although the rhGH is still active.

Protein and calorie intake, nitrogen losses, and nitrogen balance in children undergoing chronic peritoneal dialysis

We performed 22 nitrogen balance (NB) studies of three days' duration in 19 children (8.7 +/- 3.8 years) on chronic peritoneal dialysis (CPD) for 19.4 +/- 16.4 months. The dietary intakes were assessed by the double weighing method. Total nitrogen, protein, urea, and creatinine were analyzed in the dialysate and urine collected daily. Total nitrogen was also determined in the feces collected over the whole NB study period, using vegetable charcoal as a marker. The protein intake was 1.64 +/- 0.50 g/kg/day, corresponding to 126 +/- 40% of the recommended daily allowance (RDA) for normal children of the same age, and the calorie intake (diet+glucose from dialysate) reached 75 +/- 26% of RDA. Nitrogen losses were: 0.177 +/- 0.052 g/kg/day with peritoneal fluid and urine, and 0.028 +/- 0.018 g/kg/day with feces. The NB, positive in 17 out of 22 studies, ranged from -116 to +167 mg/kg/day (mean 44.0 +/- 66.2 mg/kg/day). A direct and significant correlation between NB and nitrogen intake (g/kg/day) (r = 0.562, p < 0.05) and total calorie intake (cal/kg/day) (r = 0.483, p < 0.05) has been observed. These data confirm the need to ensure in children on CPD an adequate nutritional intake, and further support the efforts to improve calorie intake.

Protracted high-dose interferon gamma therapy for chronic experimental nephropathy

This study focused on the utility of interferon gamma (IFN gamma) as an anti-fibrotic drug in renal experimental fibrosis; the nephropathy was induced by two doses of Adriamycin (ADR) in 20 Sprague Dawley rats, 10 of which were randomly assigned to receive IFN gamma (45,000 UI) on alternate day for 16 weeks. At the end of the follow up, ADR rats treated with IFN gamma developed massive proteinuria, slight renal insufficiency, and presented diffuse glomerulosclerosis, tubulo interstitial infiltration and fibrosis. No difference was found in the composition of tubulo-interstitial infiltrates, mainly consisting in CD4+T lymphocytes with a minor component of CD8+T cells, in comparison with rats treated with ADR alone. These observations demonstrate the inefficacy of a protracted high-dose treatment with IFN gamma in chronic experimental nephropathy with interstitial fibrosis.

Progression of chronic adriamycin nephropathy in leukopenic rats

In this study, we examined the progression of chronic Adriamycin (ADR) nephropathy in mild leukopenic rats and tried to define the possible relationship between tubulointerstitial lesions and proteinuria in this model. Chronic ADR nephropathy was induced by 2 doses of ADR (2 mg/kg) in 32 Sprague-Dawley rats. Eight of these were randomly assigned to cyclophosphamide treatment (50 mg/kg), given intravenously every week, to keep the blood leukocyte count constantly lower than 5,000/mm3. Serial parameters were followed for 16 weeks including clearance studies with iothalamate and p-aminohippurate and the analysis of urinary protein composition by: (a) an enzymatic assay for beta-glucosidase; (b) specific ELISA using antibodies against rat albumin and RBP, and finally (c) two-dimensional electrophoresis. ADR-treated rats rapidly (within 2 weeks) developed massive proteinuria which was in constant increment throughout the disease evolution in each single component (i.e., high and low molecular weight proteinuria, enzymuria) and developed renal insufficiency. At week 8, in ADR rats, glomerulosclerosis was mild whereas tubulointerstitial infiltrates predominated, characterized mainly by CD4+ T lymphocytes while CD8+ T lymphocytes were inconspicuous, and macrophages were only occasionally present. All such alterations had worsened after 16 weeks when the tubulointerstitial infiltration was associated with marked interstitial fibrosis and tubular atrophy. Leukopenia induced by cyclophosphamide was in all cases associated with a net amelioration of renal histopathology reducing tubulointerstitial infiltrates (by 40%) and glomerulosclerosis (33 +/- 5 vs. 52.2 +/- 7.5% sclerotic glomeruli) and also ameliorated glomerular filtration indexes (Cl 780 +/- 40 vs. 447 +/- 66 microliters/min/kg-1). In spite of these differences, albuminuria and urinary-retinol-binding protein were comparable at weeks 4, 8 and 16 in this group, while urinary beta-glucosidase was decreased at week 16 (p < 0.001) in cyclophosphamide-treated rats. No other qualitative changes in urinary proteins were detectable by 2-dimensional electrophoresis during the disease development. We concluded that chronic leukopenia prevents interstitial cellular infiltration by lymphocytes, interstitial fibrosis and slows down the decline of renal function typical of chronic ADR nephropathy. Glomerulosclerosis is also reduced in leukopenic rats without any appreciable changes in the urinary excretion of high molecular weight proteins deriving from the glomerulus. Finally, the improvement in tubulointerstitial alteration is associated with the reduction in urinary lysosomal enzymes. Tubulointerstitial alterations are implicated with a prominent role in the progression towards renal failure in chronic ADR glomerulopathy.

Multiple mechanisms for doxorubicin cytotoxicity on glomerular epithelial cells 'in vitro'

This study was planned to define the metabolic pathways for free radical production by isolated glomeruli and glomerular epithelial cells in vitro after exposure to cytotoxic doses of doxorubicin. A net increment in glomerular superoxide anion (O2.) synthesis was observed at doxorubicin doses between 10 and 30 micrograms/ml, a drug level which also induced a parallel increment in uric acid synthesis. Since the synthesis of O2. with production of uric acid implies an activity of xanthine oxidase, a few experiments were performed with glomeruli which had been deprived of xanthine oxidase activity. In this case doxorubicin-inducible O2. and uric acid synthesis by glomeruli was practically nil. A similar stimulatory effect of O2. synthesis was induced by doxorubicin on glomerular epithelial cells and also in this case O2. synthesis was suppressed by pre-treating cells with deoxyconformicin, a selective inhibitor of adenosine deaminase. Finally, equimolar amounts of the drug were equally cytotoxic even when kept constantly outside the cell by a stable linkage with an agarose macroporous bed. In summary, these data demonstrate that O2. is generated by isolated glomeruli and glomerular epithelial cells 'in vitro' when exposed to cytotoxic amounts of doxorubicin and that purine degradation to uric acid furnish the metabolic pathways for glomerular O2. generation. However, doxorubicin is comparably cytotoxic on glomerular epithelial cells from outside cells thus suggesting that also a membrane perturbation may activate the series of events leading to cell injury.

Modulation of proteinuria and renal xanthine oxidase activity by dietary proteins in acute adriamycin nephrosis in rats: lack of correlation with intra- and extracellular amino acids

Protein restriction ameliorates proteinuria in acute adriamycin (ADR) nephrosis and decreases the renal levels of xanthine oxidase (XO), a putative mediator of ADR nephrotoxicity. Hypothetically, the effect of protein restriction on renal XO levels may be due to variations in plasma and tissue proteic amino acids (AA). To elucidate this point, the levels of AA in plasma and in renal homogenates were determined in rats with ADR nephrosis and fed diets with different protein contents: (a) high (35%) casein; (b) standard (21%) casein; (c) low (9%) casein; (d) low casein plus a synthetic mixture of Val, Leu and Ile. The protein content of the diet determined certain marked variations in plasma AA: high levels of Val, Leu and Ile were found in rats fed on a high protein diet, while the same AA were low, in rats on low protein regimen. Supplementation of the low protein diet with a synthetic mixture of branched-chain AA (Val, Leu and Ile) normalized the plasma levels of these AA. In spite of these changes, tissue AA were similar in all groups, regardless of the protein contents of the diets. Furthermore, the levels of renal XO and proteinuria were unrelated to variations in plasma AA, since both parameters were low in protein-restricted and protein-restricted AA-supplemented rats while high in rats fed a high or normoproteic diet. These data demonstrate that low protein diets induce marked alterations in plasma AA composition which are similar in may respects to those found in protein malnutrition.(ABSTRACT TRUNCATED AT 250 WORDS)

Puromycin aminonucleoside metabolism by glomeruli and glomerular epithelial cells in vitro

Two puromycin aminonucleoside (PAN) excretion products were purified by HPLC from urine of PAN-treated rats and characterized by nuclear magnetic resonance as N6-dimethyl-3'amino-3'deoxyadenosine (DA-Ado) and N6-methyl-3'amino-3'deoxyadenosine (MA-Ado), respectively, the former corresponding to unmodified PAN. DA-Ado was not a substrate for adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) or xanthine oxidase (XO), while MA-Ado was consecutively converted into hypoxanthine by a mixture of ADA and PNP. A different rate of transformation of DA-Ado and MA-Ado into hypoxanthine by isolated glomeruli was observed and was higher for the monomethylated analogue by a factor of 3 (79% vs. 21%); this was ascribed to the rate-limiting level of a demethylase activity acting on DA-Ado. Furthermore, DA-Ado was not transformed by glomerular epithelial cells in culture, while a little amount of MA-Ado was converted into hypoxanthine after six hours of incubation. In spite of this different metabolic behavior, the same order of cytotoxicity on glomerular epithelial cells in culture was observed for MA-Ado, DA-Ado and commercial PAN. All these molecules induced a dose response inhibition of [3H]thymidine incorporation into DNA after exposure for two hours and a marked alteration of cell viability which was not inhibited by free radical scavengers and deferoxamine. This study provides the first evidence for a glomerular metabolism of PAN and its urinary metabolite MA-Ado involving their transformation via the purine cycle enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)