General prognostic models may neglect vulnerable subgroups in ANCA-associated vasculitis.

BACKGROUND: ANCA-associated vasculitis is an organ and life-threatening disease with the highest incidence in elderly patients. However, few studies have focussed on characteristics and treatment outcomes in a direct comparison of elderly and younger patients. METHODS: In a retrospective, single-centre, renal biopsy-cohort, patients were dichotomized by age ≥ 65 years to analyse baseline clinical, histological, laboratory and immunological characteristics and outcome differences in elderly and younger patients as regard to mortality, renal recovery from dialysis and eGFR after two years. RESULTS: In the biopsy registry, n = 774 patients were identified, of whom 268 were ≥ 65 years old. Among them, ANCA-associated vasculitis was the most prevalent kidney disease (n = 54 ≈ 20%). After a follow-up of 2 years, overall mortality was 13.4%, with 19% and 4% in patients ≥ and < 65 years of age, respectively. While 41% of elderly and 25% of younger patients were dialysis-dependent at the time of biopsy, renal recovery was achieved in 41% and 57% of patients, respectively. The accuracy of prediction differed significantly between the whole cohort and elderly patients as regard to mortality (sensitivity 46% vs. 90%, respectively) and between younger and elderly patients as regard to eGFR (r2 = 0.7 vs. 0.46, respectively). Age-group-wise analysis revealed patients above 80 years of age to have particularly dismal renal outcome and survival. CONCLUSION: In our cohort, ANCA-associated vasculitis is the single most frequent histopathological diagnosis among the elderly patients in our cohort. Elderly and younger patients have comparable chances of recovering from dialysis-dependent renal failure, with comparable residual independent kidney function after two years. This study suggests (1) relevant predictors differ between age groups and hence (2) models involving all patients with ANCA-associated vasculitis neglect important features of vulnerable subgroups, i.e., patients above 80 years old.

Efficacy of Double Membrane Filtration Immunoadsorption in Severe C1q-Binding Donor-Specific Antibody-Positive Acute Humoral Kidney Allograft Rejection: A Case Series.

INTRODUCTION: Acute antibody-mediated rejection (ABMR) is an important threat to renal allograft survival in the early transplant period and the major single cause of graft loss in the first postoperative year. Semi-selective immunoadsorption (IA) remains one of the commonly applied treatments in ABMR, reducing allo-reactive antibody load. Adding double filtration plasmapheresis (DFPP) to IA might enhance therapeutic efficacy by also addressing innate humoral effectors like complement factors. METHODS: Four patients with ABMR were treated with DFPP + IA. Clinical, histological, and immunological data and adverse events were retrospectively collected. RESULTS: Here we present four high-risk treatment-refractory ABMR cases with C1q-binding donor-specific antibodies and histology of humoral rejection under treatment with DFPP + IA. While the earlier cases (within the first year after transplantation) showed marked reduction in ABMR severity and improvement of kidney function, the later cases did not respond accordingly. Late ABMR patient 1 stabilized, whereas late ABMR patient 2 did not respond to treatment. CONCLUSIONS: Our data support the consideration of DFPP + IA as a rescue treatment option in early, severe, high-risk ABMR cases in which other treatments failed.

Renal outcomes of STOP-IgAN trial patients in relation to baseline histology (MEST-C scores).

BACKGROUND: The Oxford classification of IgA nephropathy (IgAN) defines histologic criteria (MEST-C) that provide prognostic information based on the kidney biopsy. There are few data on the predictive impact of this classification in randomized clinical trial settings. METHODS: We performed an exploratory analysis of MEST-C scores in 70 available renal biopsies from 162 randomized STOP-IgAN trial participants and correlated the results with clinical outcomes. Analyses were performed by researchers blinded to the clinical outcome of the patients. Biopsies had been obtained 6.5 to 95 (median 9.4) months prior to randomization. RESULTS: Mesangial hypercellularity (M1) associated with higher annual eGFR-loss during the 3-year trial (M1: - 5.06 ± 5.17 ml/min/1.73 m2, M0: - 0.79 ± 4.50 ml/min/1.73 m2, p = 0.002). An M0-score additionally showed a weak association with full clinical remission, whereas the percentage of patients losing ≥15 ml/min/1.73 m2 over the 3-year trial phase was higher among those scored as M1. Among patients with additional immunosuppression, ESRD occurred more frequently in patients when tubulointerstitial fibrosis (T1/2) was present (T1/2 = 33%, T0 = 0%, p = 0.008). In patients receiving supportive care only, ESRD frequencies were similar (T1/2 = 18%, T0 = 7%, p = 0.603). At randomization, eGFR was significantly lower when tubulointerstitial fibrosis was present (T1/2: 45.2 ± 15.7 ml/min/1.73 m2, T0: 74.6 ± 28.2 ml/min/1.73 m2, p < 0.0001). Endocapillary hypercellularity (E), and glomerular segmental sclerosis (S) were not associated with any clinical outcome parameter. In the analyzed cohort, patients with glomerular crescents (C1/2 scores) in their biopsies were more likely to develop ESRD during the 3-year trial phase, but this trend was only significant in patients under supportive care. CONCLUSIONS: This secondary analysis of STOP-IgAN biopsies indicates that M1, T1/2 and C1/2 scores associate with worse renal outcomes.

Impact of AMP-Activated Protein Kinase α1 Deficiency on Tissue Injury following Unilateral Ureteral Obstruction.

BACKGROUND: AMP-activated protein kinase (Ampk) is a sensor of the cellular energy status and a powerful regulator of metabolism. Activation of Ampk was previously shown to participate in monocyte-to-fibroblast transition and matrix protein production in renal tissue. Thus, the present study explored whether the catalytic Ampkα1 isoform participates in the regulation of the renal fibrotic response following unilateral ureteral obstruction (UUO). METHODS: UUO was induced in gene-targeted mice lacking functional Ampkα1 (Ampkα1-/-) and in corresponding wild-type mice (Ampkα1+/+). In the obstructed kidney and, for comparison, in the non-obstructed control kidney, quantitative RT-PCR, Western blotting and immunostaining were employed to determine transcript levels and protein abundance, respectively. RESULTS: In Ampkα1+/+ mice, UUO significantly up-regulated the protein abundance of the Ampkα1 isoform, but significantly down-regulated the Ampkα2 isoform in renal tissue. Phosphorylated Ampkα protein levels were significantly increased in obstructed kidney tissue of Ampkα1+/+ mice but not of Ampkα1-/- mice. Renal expression of α-smooth muscle actin was increased following UUO, an effect again less pronounced in Ampkα1-/- mice than in Ampkα1+/+ mice. Histological analysis did not reveal a profound effect of Ampkα1 deficiency on collagen 1 protein deposition. UUO significantly increased phosphorylated and total Tgf-ß-activated kinase 1 (Tak1) protein, as well as transcript levels of Tak1-downstream targets c-Fos, Il6, Pai1 and Snai1 in Ampkα1+/+ mice, effects again significantly ameliorated in Ampkα1-/- mice. Moreover, Ampkα1 deficiency inhibited the UUO-induced mRNA expression of Cd206, a marker of M2 macrophages and of Cxcl16, a pro-fibrotic chemokine associated with myeloid fibroblast formation. The effects of Ampkα1 deficiency during UUO were, however, paralleled by increased tubular injury and apoptosis. CONCLUSIONS: Renal obstruction induces an isoform shift from Ampkα2 towards Ampkα1, which contributes to the signaling involved in cell survival and fibrosis.

Renal allograft failure in a hyperparathyroid patient following initiation of a calcimimetic.

BACKGROUND: A 47-year-old man with a 6-year history of chronic dialysis for end-stage renal disease of unknown etiology presented for renal transplantation. While on dialysis, he had developed secondary hyperparathyroidism, which persisted after transplantation despite treatment with cinacalcet. INVESTIGATIONS: Physical examination, serum and urine analysis, ultrasound of the renal transplant, renal biopsy, bone scintigraphy. DIAGNOSIS: Severe persistent hyperparathyroidism associated with mild hypercalcemia following renal transplantation. Initiation of a calcimimetic followed by fulminant graft failure. Extensive tubular calcinosis. MANAGEMENT: Renal transplantation (with immunosuppressant medications: basiliximab, tacrolimus, mycophenolate mofetil, prednisolone), cinacalcet (halted on day 26 after transplantation), angiotensinconverting-enzyme inhibitor, angiotensin-receptor blocker, hydrochlorothiazide, emergency dialysis, subtotal parathyroidectomy.

The putative role of human peritoneal adipocytes in the fight against bacteria: synthesis of the antimicrobial active peptide DEFA1-3.

BACKGROUND: Spontaneous peritonitis is a rather rare event, even in peritoneal dialysis (PD). As defensins are natural antimicrobial peptides, we hypothesized that adipocytes as the major constituents of the omentum could play an important role in protecting against infection by generating defensin (DEFA1-3). METHODS: We isolated adipocytes from the omentum majus and conducted qualitative and quantitative RT-PCR and immunohistochemical analyses. RESULTS: For the first time described, we were able to detect DEFA1-3 mRNA in highly purified isolated omental adipocytes. The expression of DEFA1-3 in adipocytes was confirmed on the protein level by immunohistochemistry. CONCLUSION: Our report of DEFA1-3 expression by human omental adipocytes adds to the role of adipocytes in the primary defense against bacterial infection. This may include PD, where the presence of the catheter as a foreign body and the nonphysiological dialysis solution may require constant defense measures to prevent peritonitis, a hypothesis that will require further testing.

The Oxford classification of IgA nephropathy: pathology definitions, correlations, and reproducibility.

Pathological classifications in current use for the assessment of glomerular disease have been typically opinion-based and built on the expert assumptions of renal pathologists about lesions historically thought to be relevant to prognosis. Here we develop a unique approach for the pathological classification of a glomerular disease, IgA nephropathy, in which renal pathologists first undertook extensive iterative work to define pathologic variables with acceptable inter-observer reproducibility. Where groups of such features closely correlated, variables were further selected on the basis of least susceptibility to sampling error and ease of scoring in routine practice. This process identified six pathologic variables that could then be used to interrogate prognostic significance independent of the clinical data in IgA nephropathy (described in the accompanying article). These variables were (1) mesangial cellularity score; percentage of glomeruli showing (2) segmental sclerosis, (3) endocapillary hypercellularity, or (4) cellular/fibrocellular crescents; (5) percentage of interstitial fibrosis/tubular atrophy; and finally (6) arteriosclerosis score. Results for interobserver reproducibility of individual pathological features are likely applicable to other glomerulonephritides, but it is not known if the correlations between variables depend on the specific type of glomerular pathobiology. Variables identified in this study withstood rigorous pathology review and statistical testing and we recommend that they become a necessary part of pathology reports for IgA nephropathy. Our methodology, translating a strong evidence-based dataset into a working format, is a model for developing classifications of other types of renal disease.

The Oxford classification of IgA nephropathy: rationale, clinicopathological correlations, and classification.

IgA nephropathy is the most common glomerular disease worldwide, yet there is no international consensus for its pathological or clinical classification. Here a new classification for IgA nephropathy is presented by an international consensus working group. The goal of this new system was to identify specific pathological features that more accurately predict risk of progression of renal disease in IgA nephropathy, thus enabling both clinicians and pathologists to improve individual patient prognostication. In a retrospective analysis, sequential clinical data were obtained on 265 adults and children with IgA nephropathy who were followed for a median of 5 years. Renal biopsies from all patients were scored by pathologists blinded to the clinical data for pathological variables identified as reproducible by an iterative process. Four of these variables: (1) the mesangial hypercellularity score, (2) segmental glomerulosclerosis, (3) endocapillary hypercellularity, and (4) tubular atrophy/interstitial fibrosis were subsequently shown to have independent value in predicting renal outcome. These specific pathological features withstood rigorous statistical analysis even after taking into account all clinical indicators available at the time of biopsy as well as during follow-up. The features have prognostic significance and we recommended they be taken into account for predicting outcome independent of the clinical features both at the time of presentation and during follow-up. The value of crescents was not addressed due to their low prevalence in the enrolled cohort.

Ambulatory blood pressure, proteinuria and uric acid in children with IgA nephropathy and their correlation with histopathological findings.

BACKGROUND/AIMS: In adults, nighttime hypertension and hyperuricemia are new risk factors for progression of IgA nephropathy (IgAN). In children, nighttime blood pressure (BP) and serum uric acid have never been investigated. The aim of the study was to investigate nighttime BP and uric acid in children with IgAN. METHODS: Data on children with IgAN from two pediatric nephrology centers were retrospectively reviewed (renal biopsy - subclasses according Hass I-V, ambulatory blood pressure monitoring ABPM, serum uric acid, proteinuria). RESULTS: Twenty-eight untreated children with IgAN were included. Hypertension was diagnosed on the basis of ABPM in 54% of children, 50% were nondippers and 25% have isolated nighttime hypertension. The mean ambulatory BP was higher at nighttime than during daytime (systolic nighttime BP 1.11 +/- 0.79 SDS vs. daytime 0.59 +/- 0.79, diastolic nighttime BP 1.16 +/- 0.95 vs. daytime 0.52 +/- 1.10, p < 0.01 for systolic and p = 0.01 for diastolic). Children with severe histological subclasses (III-IV) tended to have higher prevalence of hypertension than children with mild subclasses (I-II), 67% vs. 38%, p = 0.13. Hyperuricemia was diagnosed in 14% of children. A significant correlation was found between proteinuria and histopathological subclasses (r = 0.44, p < 0.05). CONCLUSION: Children with IgAN have often nighttime hypertension. Hypertension and proteinuria are associated with severe histopathological findings. Hyperuricemia is a rare finding in children.

Absence of tissue reaction after focal high-dose irradiation of rabbit liver.

BACKGROUND: A focal reaction of the liver is radiologically seen after stereotactic high dose radiotherapy of liver tumors. The histological counterpart of this reaction should be clarified using an animal model. MATERIALS AND METHODS: Six New Zealand white rabbits were positioned on a special stereotactic set-up. Parts of the liver (1.5-8 ml) were irradiated with either 20-24 Gy/80% (n = 3) or 36 Gy/80% (n = 3). The animals were followed by CT examination up to 2 years after radiotherapy. Finally, the animals were sacrificed and the liver macroscopically and microscopically inspected. RESULTS: No focal reaction could be observed in any liver at any time by CT examination. The liver macroscopically and microscopically showed no changes 6 months or 2 years after radiotherapy. CONCLUSION: Up to a single dose of 36 Gy/80%, rabbits seem to show no focal tissue reaction after high dose radiation therapy of small parts of the liver.

SBA-positive fibers between the CD ampulla, mesenchyme, and renal capsule.

During kidney development, the CD shows two peculiarities. First, the tip of the CD ampulla is always found at a specific distance from the organ capsule. Second, the CD growth occurs as a perfectly straight elongation. It is unknown whether the CD-specific growth is dependent on hormonal action or on structural elements. Histochemical experiments on neonatal rabbit kidney yielded new insight into the interface of the CD ampulla and the surrounding nephrogenic mesenchyme. Incubation of tissue sections with soybean lectin (SBA) showed the existence of fibers extending in a radial course from the ampullar tip through the mesenchyme toward the organ capsule. SBA labeling did not colocalize with collagen type I, III, IV, V, and VI, laminin, fibronectin, and tenascin. It is assumed that while the kidney increases in volume the structural fixation of the ampullar tip by the SBA-positive fibers causes CD ampullae to maintain a constant distance from the organ capsule. The connection would explain the linear extension of the CD in relation to the organ capsule. In addition, the presented data suggest that the SBA-positive fibers between ampullar tip and organ capsule create a structural microcompartmentation of the nephrogenic zone.