Basement Membrane Duplication Research Articles

Quantitative scoring of progression in transplant glomerulopathy using digital pathology may be superior to Banff cg scoring

Antibody-mediated rejection (ABMR) is a major cause of kidney allograft failure. Biopsy-based surrogate endpoints reflecting ABMR progression on sequential biopsies that predict long-term outcome offer the potential to make treatment trials for ABMR feasible. However, the Banff transplant glomerulopathy (TG) scoring system (chronic glomerular injury score [cg]) relies on relatively crude and arbitrary ordinal grades and has low inter-observer concordance that currently limits its usefulness as a surrogate endpoint for ABMR progression in clinical drug trials. Here, we describe and validate a novel quantitative method for quantifying progression of TG in ABMR. Using digital pathology in sequential biopsies from 75 patients at various stages of ABMR, we scored all capillaries in the most affected glomeruli for basement membrane duplication that were correlated with allograft function, outcome, Banff lesion scores, and gene expression. Our digital scoring reflected TG progression better than the categorical Banff cg score and correlated with Banff ABMR and chronicity lesions, but not transcript changes. In multivariate analysis, the delta change between biopsies with serum creatinine and mean percent duplicated glomerular basement membranes was significantly associated with graft loss. Neither the delta in any Banff lesion scores (including cg) nor in gene expression was associated with outcome. Receiver operating characteristic curve analysis showed that the digital pathology approach was superior to the conventional score for predicting graft failure. Thus, our digital pathology-based approach for scoring TG accurately assessed progression in TG. However, further validation as a potential surrogate endpoint in clinical trials for the treatment of ABMR is warranted.

A Donor With Green Kidneys—To Transplant or Not to Transplant: A Case Report

A Donor With Green Kidneys—To Transplant or Not to Transplant: A Case Report

Genetic Background and Clinicopathologic Features of Adult-onset Nephronophthisis

IntroductionRecently, nephronophthisis (NPH) has been considered a monogenic cause of end-stage renal disease (ESRD) in adults. However, adult-onset NPH is difficult to accurately diagnose and has not been reported in a cohort study. In this study, we assessed the genetic background and clinicopathologic features of adult NPH.MethodsWe investigated 18 sporadic adult patients who were suspected as having NPH by renal biopsy. We analyzed 69 genes that cause hereditary cystic kidney disease and compared clinicopathologic findings between patients with and without pathogenic mutations in NPH-causing genes.ResultsSeven of 18 patients had pathogenic NPH-causing mutations in NPHP1, NPHP3, NPHP4, or CEP164. Compared with patients without pathogenic mutations, those with pathogenic mutations were significantly younger but did not significantly differ in the classic NPH pathologic findings, such as tubular cysts. On the other hand, the number of tubules with thick tubular basement membrane (TBM) duplication, which was defined as >10-μm thickness, was significantly higher in patients with genetically proven adult NPH than in those without pathogenic mutations. α-Smooth muscle actin (α-SMA)-positive myofibroblasts were detected inside thick TBM duplication.ConclusionsIn adult patients with NPH, thick TBM duplication was the specific finding. Our analysis also suggested that older patients tended to have no pathogenic mutations, even when they were suspected to have NPH by renal biopsy. These findings could be the novel clinical clue for the diagnosis of NPH in adult patients.

Pathological Analysis of Early Transplant Glomerulopathy in Renal Allografts Using Low-Vacuum Scanning Electron Microscopy

Aim: Low-vacuum scanning electron microscopy (LVSEM) has been reported to aid in diagnosis of renal biopsy. This study evaluated early transplant glomerulopathy in kidney transplant recipients using LVSEM. Methods: We selected 4 biopsies of cg0, 5 biopsies of cg1a, 5 biopsies of cg1b, and 4 biopsies of cg2 lesions that had been evaluated by light microscopy (LM) and transmission electron microscopy from recipients with acute/active or chronic, active antibody-mediated rejection (AABMR or CAABMR). Renal allograft paraffin sections (1 µm thickness) were stained with periodic acid-methenamine silver and observed using LVSEM. The cg score was based on the Banff classification. The parameter “percentage of duplicated capillary number” was calculated as follows: in 1 glomerulus with glomerular basement membrane (GBM) duplication, the total duplicated capillary number/the total number of capillaries ×100. Results: In all 4 biopsy specimens with AABMR showing cg0, LVSEM revealed GBM duplication not identified by LM. The average percentage of duplicated capillary number per glomerulus with GBM duplication was higher when observed by LVSEM than when observed by LM in all cg1b and cg2 biopsy specimens. Conclusion: LVSEM revealed early GBM duplication in AABMR. Early GBM duplication might progress in the very early phase of AABMR. GBM duplication was more frequently detected by LVSEM than by LM in biopsy specimens with early chronic, active antibody mediated rejection. Thus, LVSEM may be useful in diagnosis of early transplant glomerulopathy.

N-glycosylated IgG in patients with kidney transplants increases calcium/calmodulin kinase IV in podocytes and causes injury.

Transplant glomerulopathy (TG) is a major cause of late allograft loss. Increased urine podocin/creatinine ratio in TG signifies accelerated podocyte loss. The mechanisms that lead to podocyte injury in TG remain unclear. We report that IgG from kidney transplant recipients with TG, but not from those without TG, cause a reduction in the expression of nephrin, significant podocyte actin cytoskeleton, and motility changes. These changes are preceded by increased expression of calcium/calmodulin kinase IV (CAMK4). Mechanistically, we found that CAMK4 phosphorylates GSK3β (glycogen synthase kinase 3 beta), activates the Wnt pathway and stabilizes the nephrin transcriptional repressor SNAIL. Silencing neonatal Fc Receptor (FcRn) or CAMK4 prevented the podocyte-damaging effects of IgG from patients with TG. Furthermore, we show that removal of N-linked glycosyl residues from these IgG did not interfere with its entry into the podocytes but eliminated its ability to upregulate CAMK4 and cause podocyte injury. The translational value of these findings is signified by the fact that CAMK4 is increased in podocytes of patients with TG but not in those without TG despite other forms of renal dysfunction. Our results offer novel considerations to limit podocyte injury in patients with kidney transplants, which may lead to eventual glomerular destabilization and transplant glomerulopathy.

Retinal and choroidal capillaries contribution to age-related macular degeneration (AMD) phenotypes in murine models of the disease

ABSTRACTMouse models of age-related macular degeneration (AMD) such as Ccl2−/- and Ccl2−/-/Cx3cr1−/- have not yet been fully characterized ultrastructurally. Although we have previously shown extranuclear DNA (enDNA) leakage into the cytoplasm and damaged mitochondria in the retinal pigment epithelium (RPE) of these AMD mouse models, little is known about the state of their vascular capillaries of the retina and choroid. Our ultrastructural survey shows that the aberrations were not restricted to the RPE cells, but also extended to the vasculature of the retina and choroid. Their endothelial aberrations included cytoplasmic degeneration, pyknotic DNA, hypertrophic nuclei, and loss of fenestration in addition to duplication of basement membrane and loss of density in Bruch’s membrane. Moreover, the state of the vasculature in the mutant mice models suggests that the capillaries could also be active contributors to the pathological findings seen in AMD. The goal of this study is to gain insights into the early events of AMD that may lead to a better understanding of AMD’s pathogenesis, improve our preventative measures, and formulate designed therapeutic regimens that are tailored to target the initial pathological events.Abbreviations: AMD: age-related macular degeneration; BM: Bruch’s membrane; DPC: degenerate pericyte; EN: endothelial nucleus; enDNA: extranuclear DNA; GCL: ganglion cell layer; HEN: hypertrophic endothelial nucleus; IPL: inner plexiform layer; NFL: nerve fiber layer; OPL: outer plexiform layer; RBC: red blood cell; RPE: retinal pigment epithelium; SNPs: Single nucleotide polymorphisms.

Roles of the matricellular protein Tenascin-C in T-lymphocyte trafficking and etiopathogenesis of Oral Lichen Planus

ObjectiveThis study was aimed at examining the role of Tenascin-C in T cell trafficking in Oral Lichen Planus (OLP). DesignFor the in vivo immunohistochemical analyses, 115 OLP samples were collected from patients and immunostaining was performed. The intensity and distribution of TN-C expression were quantified and correlated with histological analyses of basement membrane integrity and presence of inflammatory infiltrate. For the in vitro study, TN-C and collagen were coated on culture plates and migration of T lymphocytes was assessed. ResultsTN-C immunoexpression was increased in terms of both distribution and intensity along the basement membrane zone. These changes were significantly associated with basement membrane duplication (distribution p < 0.002 and intensity p < 0.001) and bands of inflammation (distribution p < 0.002 and intensity p < 0.001) assessed by Chi-square test. T lymphocytes demonstrated significant migration towards TN-C as compared to collagen (n = 3, p < 0.05). ConclusionsThese findings indicate TN-C may have a key role in promoting T cell migration at the epithelial-mesenchymal junction in OLP. These observations suggest TN-C could be a good target for therapeutic intervention, either in itself or synergistically with anti-inflammatory directed strategies in this chronic disease management.

Early identification of transplant glomerulopathy in pediatric kidney transplant biopsies: A single-center experience with electron microscopy analysis.

Banff 2013 criteria recommend performing ultrastructural studies with electron microscopy (EM) in kidney transplant biopsies if the technology is available. We sought to determine the impact of EM on enhancing diagnostic findings in pediatric kidney transplant biopsies and the prognostic information gained from the additional findings. All kidney transplant biopsies since routine EM use started on June 1, 2014, until October 31, 2016, were reviewed. Primary outcome measures included the positive yield frequency of EM use defined as an upgraded diagnosis based on EM findings relative to light microscopy, and 12-month kidney allograft outcome of progression to ESRD or doubling of serum creatinine stratified by transplant glomerulopathy (TG) status on EM. Eighty unique kidney transplant biopsies were reviewed. EM studies were completed for 61 biopsies (76%). Complication rate was low (3.7%). In 61 biopsies where EM was completed, EM findings included foot process fusion (62%), endothelial cell swelling (38%), subendothelial lucencies (31%), and glomerular basement membrane duplication (41%). EM confirmed FSGS recurrence in three cases. In the remaining 58 cases, there was a positive yield of 31% where 18 biopsies were upgraded to a worse category after TG identification on EM. Kidney allograft outcome was poor regardless whether TG was detected early on EM or advanced on LM. Routine EM use in analyzing pediatric kidney transplant biopsies proved safe and provided valuable additional diagnostic information in almost one-third of cases. Additional studies are needed to determine if clinical interventions for early TG identified on EM can improve long-term outcomes.

C5b9 Deposition in Glomerular Capillaries Is Associated With Poor Kidney Allograft Survival in Antibody-Mediated Rejection.

C4d deposition in peritubular capillaries (PTC) reflects complement activation in antibody-mediated rejection (ABMR) of kidney allograft. However, its association with allograft survival is controversial. We hypothesized that capillary deposition of C5b9—indicative of complement-mediated injury—is a severity marker of ABMR. This pilot study aimed to determine the frequency, location and prognostic impact of these deposits in ABMR. We retrospectively selected patients diagnosed with ABMR in two French transplantation centers from January 2005 to December 2014 and performed C4d and C5b9 staining by immunohistochemistry. Fifty-four patients were included. Median follow-up was 52.5 (34.25–73.5) months. Thirteen patients (24%) had C5b9 deposits along glomerular capillaries (GC). Among these, seven (54%) had a global and diffuse staining pattern. Twelve of the C5b9+ patients also had deposition of C4d in GC and PTC. C4d deposits along GC and PTC were not associated with death-censored allograft survival (p = 0.42 and 0.69, respectively). However, death-censored allograft survival was significantly lower in patients with global and diffuse deposition of C5b9 in GC than those with a segmental pattern or no deposition (median survival after ABMR diagnosis, 6 months, 40.5 months and 44 months, respectively; p = 0.015). Double contour of glomerular basement membrane was diagnosed earlier after transplantation in C5b9+ ABMR than in C5b9– ABMR (median time after transplantation, 28 vs. 85 months; p = 0.058). In conclusion, we identified a new pattern of C5b9+ ABMR, associated with early onset of glomerular basement membrane duplication and poor allograft survival. Complement inhibitors might be a therapeutic option for this subgroup of patients.

Glomerular basement membrane duplication is a predictor of the prognosis of diabetic nephropathy in patients with type 2 diabetes.

Several clinical parameters and pathological findings are known to be predictors of the deterioration of diabetic nephropathy (DN). Glomerular basement membrane duplication (GBM-DP) is a pathological feature representing endothelial injury, which is commonly observed in DN. In the present study, we investigated the association between GBM-DP and the renal prognosis in DN. The study enrolled 80 patients with renal biopsy-proven DN who were managed at Chiba-East Hospital from 2005 to 2012. We confirmed the pathological findings according to the Renal Pathology Society classifications, and we further evaluated the GBM-DP, which was defined as double contours of the GBM that expanded more than 10% of capillary loops in the most affected nonsclerotic glomerulus. We used Cox regression models to estimate hazard ratios (HRs) for end-stage renal disease (ESRD), with adjustment for age, sex, systolic blood pressure, HbA1c, estimated glomerular filtration rate (eGFR), and urinary protein excretion (UP) at baseline. Of the 80 patients, 56 were male (70.0%) and the mean age was 59.1years. The median eGFR and UP were 42ml/min/1.73m2 (IQR 30, 59) and 3.1g/gCr (IQR 1.2, 5.2). Twenty-seven patients progressed to ESRD and one patient died during the median observational period of 2.9years (IQR 1.5, 4.3). The multivariable analyses showed that GBM-DP was significantly associated with ESRD (HR 3.18 [95% confidence interval (CI): 1.02-9.87], p = 0.045). We newly identified GBM-DP as a strong prognostic predictor in DN patients. Further study is needed to clarify the pathogenic mechanism of GBM-DP in DN.

Fluorescence in situ hybridization for the diagnosis of NPHP1 deletion–related nephronophthisis on renal biopsy

Nephronophthisis is an autosomal recessive tubulointerstitial nephropathy that is a leading genetic etiology of end-stage renal disease in children and young adults. Approximately 60% of patients with a known genetic etiology of nephronophthisis are due to homozygous deletion of the NPHP1 gene. We identified a total of 45 renal biopsies from young patients with chronic kidney disease of undetermined etiology and analyzed them for the possibility of nephronophthisis due to NPHP1 deletion using interphase fluorescence in situ hybridization and/or polymerase chain reaction. Homozygous NPHP1 deletion was identified in 9 patients (20%). In cases with adequate tissue, both assays were performed and showed 100% agreement. Blinded histopathologic analysis was then performed and identified 6 lesions that were significantly more common in biopsies from patients with NPHP1 deletion-proven nephronophthisis than chronic kidney injury of other known etiologies. Many of the classically described nephronophthisis biopsy lesions such as tubular basement membrane duplication, presence of cysts, and mononuclear interstitial inflammation were not significantly associated with this disease when compared with biopsies from patients with chronic kidney injury due to other etiologies. There were, however, morphologic lesions that were strongly associated with NPHP1 deletion including tubular abnormalities such as diverticulum, florets, and macula densa-like change as well as interstitial Tamm-Horsfall aggregates, periglomerular fibrosis, and the absence of arteriosclerosis. Awareness of the histopathologic pattern of injury in nephronophthisis combined with testing for NPHP1 deletion enables renal pathologists to provide a definitive pathologic and genetic diagnosis in a subset of patients with this disease.

A Case of Immunotactoid Glomerulopathy (ITG) Associated with Monoclonal B-Cell Lymphocytosis (MBL) with Chronic Lymphocytic Leukemia (CLL) Phenotype Treated with Obinutuzumab

Abstract Introduction: Although 44 to 90% of CLL cases have kidney infiltration on autopsy, renal involvement generally goes undetected and renal failure is unusual (Da'As N et al, Eur J Haematol 2001). There is no standard therapy for nephrotic syndrome (NS) in CLL. Treatment of CLL itself may result in regression of NS in most patients and treatment with alkylating agents, cyclosporine A, fludarabine and even splenectomy have been shown to be effective. Controversy exists regarding effectiveness of rituximab in CLL-associated nephrotic syndrome. (Yahata et al, Am J Nephrol 2000). Here we report the first case, to our knowledge, of MBL/CLL-associated NS successfully treated with obinutuzumab. Case Report: 71 years old female presented to ER with hypertensive urgency and anasarca. Past medical history was relevant for progressive hypertension (HTN) for 1 year prior. Creatinine (Cr) was 1.9mg/dL, BUN 45mg/dL, urine protein was >300mg/dl on urinalysis and subsequent 24hr urine protein was 9824mg/24hrs. Patient (pt) had renal ultrasound revealing morphologically normal kidneys without evidence of renal artery stenosis. Echocardiogram was normal. CBC revealed anemia (Hgb 9.2mg/dl) and mild thrombocytopenia (plt 121), WBC count was 7.6 x 10e3/mcl with relative lymphocytosis (47.46 %, ALC 3.594 x10e3 /mcl). On left kidney core biopsy 25 glomeruli were seen by light microscopy, 1 of which was globally sclerotic. The remaining glomeruli showed diffuse duplication of basement membranes with cellular interposition and mild to moderate intracapillary hypercellularity with endothelial cell swelling and/or leukocyte accumulation (Figure 1). Proximal tubules displayed patchy degenerative and regenerative changes including loss of apical brush border, nuclear enlargement and prominent nucleoli, and few interstitial foam cells (Figure 2). By immunofluorescence microscopy, glomeruli stained for IgG, C3, C1 and kappa light chain. There was no staining for lambda light chain. Stains for IgG heavy chain subtypes were positive for IgG1 only (Figure 3), consistent with monoclonal IgG1-kappa deposition. Electron microscopy revealed electron dense deposits in the mesangium, also in subendothelial and subepithelial locations in the capillary walls. On high-power magnification, these deposits revealed a microtubular substructure (i.e., with a central lumen) (Figure 4). These pathologic findings were consistent with ITG. Findings of ITG with IgG1 deposit as well as bicytopenia with relative lymphocytosis warranted further workup for gammopathy. SPEP revealed nonselective protein loss (total protein was 4.5g/dL, Albumin 2.9g/dL, total globulin 1.6g/dL, Albumin/Globulin ratio 1.8) with non-detectable M spike. UPEP was negative. IgG was 203mg/dL, IgA 45mg/dL, IgM 50mg/dL. Serum free kappa light chain was 35.79mg/L with normal Lambda light chain level of 20.08 mg/L with Kappa/Lambda ratio 1.78. Beta-2 microglobulin level was 6.4mg/L. Peripheral blood flow cytometry was ordered, which revealed 20% monoclonal B-cells (CD5+/CD23+) with CLL phenotype. Pt was started on prednisone 60mg daily for 7 days for ITG and decision was made to start CLL-targeted treatment with Obinutuzumab for 6 cycles, with the intent of improving the glomerulopathy, as pt did not meet IWCLL-2008 criteria for initiation of treatment for CLL. Obinutuzumab was given in the usual schedule of 100 mg on day 1, 900 mg on day 2 and 1000 mg on day 8 and 15 of first month, followed by 1000 mg every 28 days for 5 additional cycles. Repeat flow cytometry in 6 months after diagnosis showed complete response of monoclonal lymphocytosis (minimal residual disease negative). There was complete normalization of kidney function (Cr 0.73mg/dl and glomerular filtration rate 78ml/min) and no further evidence of proteinuria or edema. Hypertension has fully resolved, without additional need for anti-hypertensives. 30 months post treatment pt remains in remission for both MBL and nephrotic syndrome. Discussion: Treatment with obinutuzumab may lead to complete resolution and sustained remission of nephrotic syndrome associated with CLL. The more efficient B-cell depletion achieved with obinutuzumab may make this a better treatment choice for CLL associated NS than rituximab. Further evaluation with clinical trials is warranted. Download : Download high-res image (128KB) Download : Download full-size image Disclosures Skarbnik: Novartis: Speakers Bureau; Abbvie: Other: Ad board, Speakers Bureau; Genentech: Speakers Bureau; Gilead: Speakers Bureau; Seattle Genetics: Speakers Bureau.

Antibody-Mediated Rejection: A Review.

Chronic antibody injury is a serious threat to allograft outcomes and is therefore the center of active research. In the continuum of allograft rejection, the development of antibodies plays a critical role. In recent years, an increased recognition of molecular and histologic changes has provided a better understanding of antibody-mediated rejection (AMR), as well as potential therapeutic interventions. However, several pathways are still unknown, which accounts for the lack of efficacy of some of the currently available agents that are used to treat rejection. We review the current diagnostic criteria for AMR; AMR paradigms; and desensitization, treatment, and prevention strategies. Chronic antibody-mediated endothelial injury results in transplant glomerulopathy, manifested as glomerular basement membrane duplication, double contouring, or splitting. Clinical manifestations of AMR include proteinuria and a rise in serum creatinine. Current strategies for the treatment of AMR include antibody depletion with plasmapheresis (PLEX), immunoadsorption (IA), immunomodulation with intravenous immunoglobulin (IVIG), and T cell- or B cell-depleting agents. Some treatment benefits have been found in using PLEX and IA, and some small nonrandomized trials have identified some benefits in using rituximab and the proteasome inhibitor-based therapy bortezomib. More recent histologic follow-ups of patients treated with bortezomib have not shown significant benefits in terms of allograft outcomes. Furthermore, no specific treatment approaches have been approved by the US Food and Drug Administration. Other agents used for more difficult rejections include bortezomib and eculizumab (an anti-C5 monoclonal antibody). AMR is a fascinating field with ample opportunities for research and progress in the future. Despite the use of advanced techniques for the detection of human leukocyte antigen (HLA) or non-HLA donor-specific antibodies, alloimmune response remains an important barrier for successful long-term allograft function. Treatment of AMR with currently available therapies has produced a variety of results, some of them suboptimal, precluding the development of standardized protocols. New therapies are promising, but randomized controlled trials are needed to find surrogate markers and improve the efficacy of therapy.

AJKD Atlas of Renal Pathology: Systemic Sclerosis

Systemic sclerosis (scleroderma) has a strong predilection in women, with onset typically between ages 30-50 years. Scleroderma kidney disease occurs in 60%-70% of patients with systemic scleroderma, mostly in those with a diffuse, rather than limited, form of cutaneous scleroderma. Kidney disease is evident by hypertension, proteinuria, and loss of glomerular filtration rate. Scleroderma kidney crisis develops in about 10%-20%, and presents as new onset malignant hypertension with acute kidney injury. Antinuclear antibody is positive in >90% of these patients. Anti-topoisomerase 1 and anti-RNA polymerase antibodies are often associated with kidney involvement. Patients with scleroderma kidney crisis may require dialysis. Use of angiotensin-converting enzyme inhibitors has improved prognosis of patients with kidney crisis, but mortality at 5 years remained at 30%-40%. Light microscopy: Medium- and large-sized arteries are affected by thrombotic microangiopathy. Fibrin thrombi with fibrinoid necrosis of the vessel wall without associated wall inflammation are characteristic. Intimal mucoid change, endothelial swelling, and fragmented red blood cells within the vessel wall occur acutely. Later, there is intimal proliferation, resulting in an “onion skin” concentric appearance with luminal narrowing. Glomeruli typically show ischemic collapse, but may also have mesangiolysis and fibrin thrombi. Glomerular basement membrane duplication is present in chronic cases. Tubular injury occurs with acute injury, and tubular atrophy and interstitial fibrosis are proportional to vascular injury in the chronic stages. Immunofluorescence microscopy: Nonspecific staining for immunoglobulin M and C3 may be seen. Fibrinogen staining can be observed in glomeruli and arteries associated with fibrinoid necrosis or acute thrombotic microangiopathy. Electron microscopy: Endothelial swelling and expansion of lamina rara interna are present. Glomerular basement membrane duplication with cellular interposition is present in chronic stages. Injury from scleroderma is related to endothelial injury of uncertain etiology. About half of patients have anti-endothelial antibodies. Endothelial injury leads to altered vascular permeability and platelet aggregation. Increased renin production exacerbates hypertension. Thrombotic microangiopathy of other causes has similar morphologic findings, including malignant hypertension, drug etiology, complement dysregulation, hemolytic uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP), and transplant rejection. Scleroderma mostly affects interlobular arteries in contrast to HUS/TTP, which predominantly affects glomeruli. Malignant hypertension-associated thrombotic microangiopathy may have an identical appearance to that seen in scleroderma, although this is more often associated with underlying arterionephrosclerosis. Clinical history and serologic data help to distinguish these etiologies. •Fibrin thrombi with fibrinoid necrosis, mostly in interlobular arteries•Interlobular arteries with “onion skin” concentric appearance with luminal narrowing in chronic stage•Endothelial injury by electron microscopyFigure 2Scleroderma with artery showing early organization with “onion skin” change caused by lamellation and mucoid change with swelling of the intimal layer. There is corrugation of the glomerular basement membrane (Jones silver stain).Reproduced with permission from AJKD 34(2):e4.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Scleroderma with early arterial changes with swollen endothelium and mucoid appearance of the subintima with red blood cell fragments (Jones silver stain).Reproduced with permission from AJKD 34(2):e4.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Scleroderma in a chronic stage with fibrous organization of intimal injury resulting in a lamellated “onion skin” appearance of arteries (periodic acid–Schiff stain).Reproduced with permission from AJKD 34(2):e4.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 5Scleroderma with corrugation and expansion of the lamina rara interna, evidence of endothelial injury and ischemia (electron microscopy).Reproduced with permission from AJKD 34(2):e4.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

AJKD Atlas of Renal Pathology: Chronic Antibody-Mediated Rejection

Chronic antibody-mediated rejection is commonly associated with progressive loss of kidney function and proteinuria, although early stages may be subclinical and recognizable only through protocol biopsies. Diagnostic criteria according to the Banff 2013 classification (Haas et al, Am J Transplant 2014:14(2):272-283) include the presence of all of the following:1.Histologic evidence of chronic tissue injury, defined by the presence of at least one of the following:a.Transplant glomerulopathy (cg > 0) in the absence of chronic thrombotic microangiopathyb.Severe peritubular capillary basement membrane multilayering by electron microscopyc.New-onset arterial intimal fibrosis with no other known etiology2.Current/recent histologic evidence of antibody interaction with vascular endothelium, defined by the presence of at least one of the following:a.Linear C4d staining in peritubular capillaries (at least 10% by immunofluorescence [IF] on frozen sections or any positivity by immunohistochemistry on paraffin sections)b.At least moderate microvascular inflammation (g + ptc > 2)c.Increased expression of tissue gene transcripts indicative of endothelial injury3.Presence of donor-specific antibodies (DSA; HLA or non-HLA) in the serum Similar to acute antibody-mediated rejection, endothelial injury results from interaction between DSA with primarily mismatched HLA or non-HLA molecules. Repetitive and chronic endothelial damage is associated with new basement membrane formation, which in glomeruli manifests as glomerular basement membrane duplication (transplant glomerulopathy), often with resulting segmental sclerosis, and multilayering of the peritubular capillary basement membrane. Podocyte injury and foot process effacement are common findings. Glomerular basement membrane duplication is also found in other conditions associated with chronic endothelial damage, causing a membranoproliferative pattern of injury. Chronic thrombotic microangiopathy may be indistinguishable from transplant glomerulopathy on a morphologic basis unless features of concomitant acute thrombotic microangiopathy or vascular changes are present. In such cases, correlation with clinical history will be important. Membranoproliferative glomerulonephritis due to immune complex processes (lupus nephritis, immunoglobulin A nephropathy, cryoglobulinemic glomerulonephritis, etc) must be ruled out by IF and electron microscopy. Peritubular capillary basement membrane multilayering, especially if not severe (<7 layers), is not specific to chronic antibody-mediated rejection. Arterial intimal fibrosis is a common finding, often associated with chronic hypertension and aging. Scattered T cells and foam cells may be present in the expanded intima, but are not specific for chronic antibody-mediated rejection and may also be seen in chronic T-cell–mediated rejection. •Transplant glomerulopathy•Peritubular capillary basement membrane multilayering•Peritubular capillary C4d stainingFigure 2Transplant glomerulopathy with prominent glomerular basement membrane duplication and cellular interposition in a capillary loop. Podocytes show significant foot process effacement (electron microscopy).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Chronic antibody-mediated rejection with severe peritubular capillary multilayering (>7 layers of basement membrane), representing response to repetitive and chronic endothelial injury. Note that the endothelial cell is swollen and has lost its normal fenestrations (electron microscopy).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Chronic antibody-mediated rejection with diffuse linear C4d staining in peritubular capillaries (immunofluorescence microscopy, C4d).View Large Image Figure ViewerDownload Hi-res image Download (PPT)

AJKD Atlas of Renal Pathology: Glomerulonephritis With Dominant C3

Glomerulonephritis with dominant C3, a form of C3 glomerulopathy, typically presents with subnephrotic proteinuria and hematuria. Although a minority of patients may present with nephrotic syndrome, about half present with hypertension and impaired glomerular filtration rate. Up to 15% progress to end-stage renal disease. C3 glomerulopathy is rare with a typical age of onset of 30 years (range, 7-70 years). Light microscopy: Most biopsies show a membranoproliferative pattern. Other less common histologic patterns include mesangial proliferative, diffuse endocapillary hypercellularity, and crescentic. Immunofluorescence microscopy: Dominant or only C3 mesangial and capillary loop staining, at least 2+ stronger than immunoglobulin and C1q staining. Electron microscopy: Mesangial and subendothelial deposits with occasional subepithelial deposits, possibly hump-like, without dense transformation of the deposits. Abnormalities in alternative complement pathway regulation, genetic or acquired. Dense deposit disease can present with similar light microscopy and immunofluorescence findings, but has diagnostic ribbon-like dense deposits within the glomerular basement membrane, not seen in this form of C3 glomerulopathy. Postinfectious glomerulonephritis can present with a similar pattern of C3 dominant staining by immunofluorescence; however, endocapillary hypercellularity with numerous neutrophils and subepithelial hump-like deposits revealed by electron microscopy are features that help distinguish it from glomerulonephritis with dominant C3. Some patients with pathologic features indistinguishable from typical postinfectious glomerulonephritis have an atypical prolonged clinical course, and may have underlying complement dysregulation, indicative of a C3 glomerulopathy. •Only C3 or dominant C3 staining, 2+ greater than immunoglobulin or C1q shown by immunofluorescence•No dense transformation of the glomerular basement membranes revealed by electron microscopyFigure 2Glomerulonephritis with dominant C3 showing contour duplication of glomerular basement membranes (Jones silver stain).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Glomerulonephritis with dominant C3, with strong mesangial and capillary wall C3 staining (immunofluorescence microscopy, C3).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Glomerulonephritis with dominant C3, with subendothelial deposits associated with interposed cell (asterisk) and new basement membrane material between the interposed cell and endothelium (arrow; electron microscopy).View Large Image Figure ViewerDownload Hi-res image Download (PPT)

PD20-12 MICROVASCULAR INJURY IN KETAMINE-INDUCED BLADDER DYSFUNCTION

PD20-12 MICROVASCULAR INJURY IN KETAMINE-INDUCED BLADDER DYSFUNCTION

HLA-DR and -DQ Eplet Mismatches and Transplant Glomerulopathy: A Nested Case–Control Study

We conducted a nested case-control study from a cohort of adult kidney transplant recipients to assess the risk of transplant glomerulopathy (TG) as a function of donor and recipient HLA-DR and -DQ incompatibility at the eplet level. Cases (n = 52) were defined as patients diagnosed with transplant glomerulopathy based on biopsies showing glomerular basement membrane duplication without immune complex deposition. Controls (n = 104) with a similar follow-up from transplantation were randomly selected from the remaining cohort. HLAMatchmaker was used to ascertain the number of DRB1/3/4/5, DQA1 and DQB1 related eplet mismatches (eplet load). Multivariable conditional logistic regression models demonstrated an increase in the odds of TG (odds ratios [OR] of 2.84 [95% confidence interval (CI): 1.03, 7.84] and 4.62 [95% CI: 1.51, 14.14]) in the presence of 27-43 and >43 HLA-DR + DQ related eplet mismatches versus <27 eplet mismatches, respectively. When the eplet load was modeled as a continuous variable, the OR for TG was 1.25 (95% CI: 1.04, 1.50) for every 10 additional HLA-DR + DQ eplet mismatches. Our study suggests that minimization of HLA-DR + DQ eplet mismatches may decrease the incidence of transplant glomerulopathy diagnosed by indication biopsies. The role of eplet immunogenicity/antigenicity as determinants of allograft outcomes requires further study.

A.P.13: Myotonic discharges in autophagic vacuolar myopathies: A potential electrophysiologic marker

Disordered lysosomal function within muscle cells is the basis for a group of diseases referred to as autophagic vacuolar myopathies. These disorders include acid maltase deficiency (Pompe disease), LAMP-2 deficiency (Danon disease), and X-linked myopathy with excess autophagy (XMEA). We present a 65year old diabetic woman with bilateral leg weakness evolving over 2years to the point she was unable to ambulate without assistance. There was no family history of a similar disorder. She had prominent weakness in her legs proximally>distally while arms and bulbar muscles had normal strength. Mild percussion myotonia of forearm muscles was present but not hand grasp myotonia. CK was 914. Acid alpha-glucosidase activity was normal. Nerve conduction studies showed evidence of a largely axonal neuropathy likely related to her poorly controlled diabetes. Needle exam demonstrated fibrillations and frequent short duration myotonic discharges in arm and leg muscles. Quadriceps muscle biopsy showed basophilic cytoplasmic stippling within myofibers that corresponded to small vacuoles discernable by enzyme histochemical staining for acetylcholinesterase and immunostaining for dystrophin and other sarcolemmal proteins. Cytoplasmic clusters of lysosomes and autophagosome extrusion with duplication of basement membranes were observed with electron microscopy. The biopsy findings are those of an autophagic vacuolar myopathy, the underlying nature of which has not been defined. Frequent short duration myotonic discharges were a remarkable feature. The presence of myotonic discharges has been previously reported to occur in patients with Pompe disease, Danon disease, and XMEA. These discharges indicate hyperexcitability of the muscle membranes and may reflect structural sarcoplasmic changes. Their occurrence in the various disorders involving autophagy suggests that short myotonic discharges may be a diagnostically useful electrophysiologic marker for this group of disorde.

Class II HLA Eplet Load Is a Risk Factor for Transplant Glomerulopathy.

Study purpose: The objective of this study was to assess the risk of developing transplant glomerulopathy as a function of donor and recipient class II HLA incompatibility at the eplet level. Methods: We conducted a nested case-control study from a cohort of kidney transplant recipients (KTR) transplanted at the University Health Network (UHN) January 1, 2000 to December 31, 2012. Cases (n=52) were defined as adult KTR diagnosed with transplant glomerulopathy based on kidney allograft biopsies showing glomerular basement membrane duplication without immune complex deposition. Controls (n=104) were randomly selected from the remaining cohort at the time of case diagnosis. HLAMatchmaker was used to ascertain the number of class II (DR and DQ) eplet mismatches, or the class II “eplet load,” from donors and recipients' 4-digit HLA typing. DRB1, DR3/4/5, DQA, and DQB typing was updated using molecular methods when absent. Class II eplet load was modeled both as a categorical (DR and DQ eplet load: <27, 27 to 43, >43) and continuous variable. We fit conditional logistic regression models adjusting for recipient, donor, and transplant characteristics to assess the association between transplant glomerulopathy and eplet load. Results: A significant increase in the odds of transplant glomerulopathy was observed across ascending categories of eplet load. The fully adjusted model showed odds ratios of transplant glomerulopathy of 2.84 (95% confidence interval: 1.03, 7.84) and 4.62 (95% CI: 1.51, 14.14) in the presence of 27 to 43 and >43 class II eplet mismatches vs. <27 eplet mismatches, respectively. When the eplet load was modelled as a continuous variable, the odds ratios for transplant glomerulopathy were 1.25 (95% CI: 1.04, 1.50), 1.63 (95% CI: 1.14, 2.33), and 1.27 (95% CI: 0.95, 1.69) for every 10 additional class II (DR and DQ), DR, and DQ eplet mismatches, respectively. Conclusions: Class II eplet load is an independent risk factor for transplant glomerulopathy. Minimization of class II HLA mismatches between donors and recipients at the eplet level and tailoring of immunosuppression regimens to eplet load may decrease the incidence of transplant glomerulopathy in kidney transplant recipients.