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Nili F, Farahani E, Moghimian M, Jahanzad I, Minoo FS, Salarvand S, Abdollahi A, Mirshahvalad SA. Spectrum and Distribution of Biopsy-proven Kidney Diseases: A 12-year Survey of a Single Center in Iran. SAUDI JOURNAL OF KIDNEY DISEASES AND TRANSPLANTATION 2023; 34:346-354. [PMID: 38345590 DOI: 10.4103/1319-2442.395451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2024] Open
Abstract
Data about the prevalence of biopsy-proven kidney diseases in Iran are rare, and none of the previous studies used electron microscopy for diagnosis. This study aimed to analyze the prevalence of biopsy-proven kidney diseases in Iran's primary referral center. To the best of our knowledge, this is the most extensive study carried out in Iran. Reports of kidney biopsy samples from patients referred to our center in 2007-2018 were reviewed for demographic data, clinical presentation, and final diagnosis. Statistical analyses were performed. Among the 3455 samples received, 2975 were analyzed. Nephrotic syndrome (39%) was the most common cause of biopsy, followed by subnephrotic proteinuria (18%), hematuria in association with proteinuria (15%), renal failure (9%), isolated hematuria (6%), and lupus nephritis (LN) (4%). The most common diagnoses were membranous glomerulonephritis (17.9%), focal segmental glomerulosclerosis (FSGS) (15.9%), LN (13.7%), minimal histopathological findings (unsampled FSGS vs. minimal change disease, 12.1%), Immunoglobin A nephropathy (IgAN) (6.5%) and Alport syndrome (6.1%). NS and proteinuria were the most common indications for a kidney biopsy. IgAN and LN were the most common causes of primary and secondary glomerulonephritis, presenting with hematuria and proteinuria, respectively. Although membranous glomerulonephritis was the most common disease, it has been replaced by FSGS in recent years.
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Affiliation(s)
- Fatemeh Nili
- Department of Pathology, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
| | - Elham Farahani
- Department of Radiology, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mehran Moghimian
- Department of Urology, Hasheminejad Kidney Center, Iran University of Medical Sciences, Tehran, Iran
| | - Issa Jahanzad
- Department of Pathology, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Samaneh Salarvand
- Department of Pathology, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Abdollahi
- Department of Pathology, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
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Planinc I, Ilic I, Dejea H, Garcia-Canadilla P, Gasparovic H, Jurin H, Milicic D, Skoric B, Stampanoni M, Bijnens B, Bonnin A, Cikes M. A Novel Three-Dimensional Approach Towards Evaluating Endomyocardial Biopsies for Follow-Up After Heart Transplantation: X-Ray Phase Contrast Imaging and Its Agreement With Classical Histopathology. Transpl Int 2023; 36:11046. [PMID: 36762268 PMCID: PMC9904361 DOI: 10.3389/ti.2023.11046] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/09/2023] [Indexed: 01/26/2023]
Abstract
Endomyocardial biopsies are the gold standard for surveillance of graft rejection following heart transplantation, and are assessed by classical histopathology using a limited number of previously stained slices from several biopsies. Synchrotron propagation-based X-ray phase contrast imaging is a non-destructive method to image biological samples without tissue preparation, enabling virtual 2D and 3D histopathology. We aimed to show the feasibility of this method to assess acute cellular rejection and its agreement to classical histopathology. Right ventricular biopsies were sampled from 23 heart transplantation recipients (20 males, mean age 54±14 years) as part of standard follow-up. The clinical diagnosis of potential rejection was made using classical histopathology. One additional study sample was harvested and imaged by X-ray phase contrast imaging, producing 3D datasets with 0.65 μm pixel size, and up to 4,320 images per sample. An experienced pathologist graded both histopathological and X-ray phase contrast images in a blinded fashion. The agreement between methods was assessed by weighted kappa, showing substantial agreement (kappa up to 0.80, p < 0.01) between X-ray phase contrast imaging and classical histopathology. X-ray phase contrast imaging does not require tissue processing, allows thorough analysis of a full myocardial sample and allows identification of acute cellular rejection.
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Affiliation(s)
- Ivo Planinc
- Department of Cardiovascular Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Ivana Ilic
- Department of Pathology and Cytology, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Hector Dejea
- Paul Scherrer Institute (PSI), Villigen, Switzerland,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Patricia Garcia-Canadilla
- Institut de Recerca Biomèdica August Pi i Sunyer (IDIBAPS), Barcelona, Spain,BCNatal-Barcelona Center for Maternal-Fetal and Neonatal Medicine, Hospital Sant Joan de Déu and Hospital Clínic, University of Barcelona, Barcelona, Spain,Cardiovascular Diseases and Child Development, Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Hrvoje Gasparovic
- Department of Cardiac Surgery, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Hrvoje Jurin
- Department of Cardiovascular Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Davor Milicic
- Department of Cardiovascular Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Bosko Skoric
- Department of Cardiovascular Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia
| | - Marco Stampanoni
- Paul Scherrer Institute (PSI), Villigen, Switzerland,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Bart Bijnens
- Institut de Recerca Biomèdica August Pi i Sunyer (IDIBAPS), Barcelona, Spain,Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Anne Bonnin
- Paul Scherrer Institute (PSI), Villigen, Switzerland
| | - Maja Cikes
- Department of Cardiovascular Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia,*Correspondence: Maja Cikes,
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Roufosse C, Becker JU, Rabant M, Seron D, Bellini MI, Böhmig GA, Budde K, Diekmann F, Glotz D, Hilbrands L, Loupy A, Oberbauer R, Pengel L, Schneeberger S, Naesens M. Proposed Definitions of Antibody-Mediated Rejection for Use as a Clinical Trial Endpoint in Kidney Transplantation. Transpl Int 2022; 35:10140. [PMID: 35669973 PMCID: PMC9163810 DOI: 10.3389/ti.2022.10140] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 03/03/2022] [Indexed: 12/15/2022]
Abstract
Antibody-mediated rejection (AMR) is caused by antibodies that recognize donor human leukocyte antigen (HLA) or other targets. As knowledge of AMR pathophysiology has increased, a combination of factors is necessary to confirm the diagnosis and phenotype. However, frequent modifications to the AMR definition have made it difficult to compare data and evaluate associations between AMR and graft outcome. The present paper was developed following a Broad Scientific Advice request from the European Society for Organ Transplantation (ESOT) to the European Medicines Agency (EMA), which explored whether updating guidelines on clinical trial endpoints would encourage innovations in kidney transplantation research. ESOT considers that an AMR diagnosis must be based on a combination of histopathological factors and presence of donor-specific HLA antibodies in the recipient. Evidence for associations between individual features of AMR and impaired graft outcome is noted for microvascular inflammation scores ≥2 and glomerular basement membrane splitting of >10% of the entire tuft in the most severely affected glomerulus. Together, these should form the basis for AMR-related endpoints in clinical trials of kidney transplantation, although modifications and restrictions to the Banff diagnostic definition of AMR are proposed for this purpose. The EMA provided recommendations based on this Broad Scientific Advice request in December 2020; further discussion, and consensus on the restricted definition of the AMR endpoint, is required.
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Affiliation(s)
- Candice Roufosse
- Department of Immunology and Inflammation, Centre for Inflammatory Disease, Imperial College London, London, United Kingdom
| | - Jan Ulrich Becker
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Marion Rabant
- Department of Pathology, Hôpital Necker-Enfants Malades, Paris, France
| | - Daniel Seron
- Department of Nephrology and Kidney Transplantation, Vall d'Hebrón University Hospital, Barcelona, Spain
| | | | - Georg A Böhmig
- Division of Nephrology and Dialysis, Department of Internal Medicine, Medical University of Vienna, Vienna, Austria
| | - Klemens Budde
- Department of Nephrology and Medical Intensive Care, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Fritz Diekmann
- Department of Nephrology and Kidney Transplantation, Hospital Clinic Barcelona, Barcelona, Spain
| | - Denis Glotz
- Paris Translational Research Center for Organ Transplantation, Hôpital Saint Louis, Paris, France
| | - Luuk Hilbrands
- Department of Nephrology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Alexandre Loupy
- Paris Translational Research Center for Organ Transplantation, Hôpital Necker, Paris, France
| | - Rainer Oberbauer
- Division of Nephrology and Dialysis, Department of Internal Medicine, Medical University of Vienna, Vienna, Austria
| | - Liset Pengel
- Centre for Evidence in Transplantation, University of Oxford, Oxford, United Kingdom
| | - Stefan Schneeberger
- Department of General, Transplant and Thoracic Surgery, Medical University of Innsbruck, Innsbruck, Austria
| | - Maarten Naesens
- Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
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Broecker V, Bardsley V, Torpey N, Perera R, Montero R, Dorling A, Bentall A, Neil D, Willicombe M, Berry M, Roufosse C. Clinical-pathological correlations in post-transplant thrombotic microangiopathy. Histopathology 2020; 75:88-103. [PMID: 30851188 DOI: 10.1111/his.13855] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 03/06/2019] [Indexed: 12/25/2022]
Abstract
AIMS Post-transplant thrombotic microangiopathy (TMA) is a rare and clinically challenging finding in renal transplant biopsies. In addition to recurrent atypical haemolytic uraemic syndrome, TMA in renal transplants is associated with various conditions, such as calcineurin inhibitor (CNI) treatment, antibody-mediated rejection (ABMR), viral infections, sepsis, pregnancy, malignancies, and surgery. The therapeutic implications of this diagnosis are considerable. In order to better understand post-transplant TMA and to identify histological or clinical differences between associated causes, we conducted a multicentre retrospective study. METHODS AND RESULTS Clinical parameters and transplant renal biopsy findings from 81 patients with TMA were analysed. Biopsies from 38 patients were also analysed with electron microscopy. On the basis of clinical-pathological correlation, TMA was attributed to a main aetiology, whenever possible. TMA occurred at a median of 30 days post-transplantation. Systemic features of TMA were present in only 18% of cases. Twenty-two per cent of cases were attributed to CNI and 11% to ABMR. Although other potentially contributing factors were found in 56% of patients, in most cases (63%) no clearly attributable cause of TMA was identified. Histological differences between groups were minimal. The detection of ultrastructural features that are usually associated with ABMR may help to establish ABMR as the cause of TMA. CONCLUSIONS Although CNI and ABMR appear to be the main contributors to post-transplant TMA, the aetiology of most cases is probably multifactorial, and TMA cannot be unequivocally attributed to a single underlying aetiology. Morphological features of TMA are not discriminating, but electron microscopy may help to identify ABMR-associated TMA.
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Affiliation(s)
- Verena Broecker
- Department of Clinical Pathology, Sahlgrenska University Hospital, Gothenburg, Sweden.,Department of Histopathology, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Victoria Bardsley
- Department of Histopathology, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Nicholas Torpey
- Department of Clinical Nephrology and Transplantation, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Ranmith Perera
- Department of Cellular Pathology, St Thomas' Hospital, London, UK
| | - Rosa Montero
- Department of Nephrology, Guy's Hospital, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - Anthony Dorling
- MRC Centre for Transplantation, King's College London, London, UK
| | - Andrew Bentall
- Department of Nephrology and Transplantation, University Hospital Birmingham, NHS Foundation Trust, Birmingham, UK
| | - Desley Neil
- Department of Histopathology, University Hospital Birmingham, NHS Foundation Trust, Birmingham, UK
| | - Michelle Willicombe
- Department of Medicine, Hammersmith Hospital, Imperial College Health Care NHS Trust, London, UK
| | - Miriam Berry
- Department of Clinical Nephrology and Transplantation, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Candice Roufosse
- Faculty of Medicine, Imperial College, London, UK.,Department of Cellular Pathology, North West London Pathology, London, UK
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Molecular Assessment of C4d-Positive Renal Transplant Biopsies Without Evidence of Rejection. Kidney Int Rep 2018; 4:148-158. [PMID: 30596178 PMCID: PMC6308373 DOI: 10.1016/j.ekir.2018.09.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 08/17/2018] [Accepted: 09/10/2018] [Indexed: 12/28/2022] Open
Abstract
Introduction Immunohistochemical staining for C4d in peritubular capillaries has been part of antibody-mediated rejection (AbMR) definition in the Banff Classification for Allograft Pathology since 2003. However, it has limited sensitivity and specificity, therefore the clinical significance of C4d-positive biopsies without evidence of rejection (C4d+ WER) is unknown. We investigated the transcript levels of genes associated with AbMR in C4d+ WER biopsies from both ABO-compatible and incompatible renal transplant patients. Methods RNA was extracted from formalin-fixed paraffin-embedded renal transplant biopsies (n = 125) and gene expression analysis of 35 AbMR-associated transcripts carried out using the NanoString nCounter system. Results AbMR-associated transcripts were significantly increased in samples with AbMR or suspicious AbMR. A subgroup of 17 of 35 transcripts that best distinguished AbMR from C4d-negative biopsies without evidence of rejection was used to study C4d+ WER samples. There was no differential expression between C4d-negative and C4d+ WER from both ABO-incompatible and -compatible transplants. The geometric mean of 17 differentially expressed genes was used to assign the C4d+ WER biopsies a high- or low-AbMR transcript score. Follow-up biopsies showed AbMR within 1 year of initial biopsy in 5 of 7 high-AbMR transcript patients but only 2 of 46 low-AbMR transcript patients. In multivariate logistic regression analysis, elevated transcript levels in a C4d+ WER biopsy were associated with increased odds for biopsy-proven AbMR on follow-up (P = 0.032, odds ratio 16.318), whereas factors including donor-specific antibody (DSA) status and time since transplantation were not. Conclusion Gene expression analysis in C4d+ WER samples has the potential to identify patients at higher risk of developing AbMR.
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Masum MA, Ichii O, Elewa YHA, Nakamura T, Kon Y. Local CD34-positive capillaries decrease in mouse models of kidney disease associating with the severity of glomerular and tubulointerstitial lesions. BMC Nephrol 2017; 18:280. [PMID: 28870174 PMCID: PMC5584339 DOI: 10.1186/s12882-017-0694-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 08/21/2017] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The renal vasculature plays important roles in both homeostasis and pathology. In this study, we examined pathological changes in the renal microvascular in mouse models of kidney diseases. METHODS Glomerular lesions (GLs) in autoimmune disease-prone male BXSB/MpJ-Yaa (Yaa) mice and tubulointerstitial lesions (TILs) in male C57BL/6 mice subjected to unilateral ureteral obstruction (UUO) for 7 days were studied. Collected kidneys were examined using histopathological techniques. A nonparametric Mann-Whitney U test (P < 0.05) was performed to compare healthy controls and the experimental mice. The Kruskal-Wallis test was used to compare three or more groups, and multiple comparisons were performed using Scheffe's method when significant differences were observed (P < 0.05). RESULTS Yaa mice developed severe autoimmune glomerulonephritis, and the number of CD34+ glomerular capillaries decreased significantly in GLs compared to that in control mice. However, UUO-treated mice showed severe TILs only, and CD34+ tubulointerstitial capillaries were decreased significantly in TILs with the progression of tubulointerstitial fibrosis compared to those in untreated control kidneys. Infiltrations of B-cells, T-cells, and macrophages increased significantly in the respective lesions of both disease models (P < 0.05). In observations of vascular corrosion casts by scanning electron microscopy and of microfil rubber-perfused thick kidney sections by fluorescence microscopy, segmental absences of capillaries were observed in the GLs and TILs of Yaa and UUO-treated mice, respectively. Further, transmission electron microscopy revealed capillary endothelial injury in the respective lesions of both models. The numbers of CD34+ glomerular and tubulointerstitial capillaries were negatively correlated with all examined parameters in GLs (P < 0.05) and TILs (P < 0.01), respectively. CONCLUSIONS From the analysis of mouse models, we identified inverse pathological correlations between the number of local capillaries in GLs and TILs and the severity of kidney diseases.
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Affiliation(s)
- Md Abdul Masum
- Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Japan
| | - Osamu Ichii
- Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Japan
| | - Yaser Hosny Ali Elewa
- Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Japan
- Department of Histology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt
| | - Teppei Nakamura
- Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Japan
- Section of Biological Safety Research, Chitose Laboratory, Japan Food Research Laboratories, Tokyo, Japan
| | - Yasuhiro Kon
- Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo, Japan
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Go H, Shin S, Kim YH, Han DJ, Cho YM. Refinement of the criteria for ultrastructural peritubular capillary basement membrane multilayering in the diagnosis of chronic active/acute antibody-mediated rejection. Transpl Int 2017; 30:398-409. [PMID: 28109026 DOI: 10.1111/tri.12921] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 08/06/2016] [Accepted: 01/12/2017] [Indexed: 12/17/2022]
Abstract
Chronic active/acute antibody-mediated rejection (cABMR) is the main cause of late renal allograft loss. Severe peritubular capillary basement membrane multilayering (PTCML) assessed on electron microscopy is one diagnostic feature of cABMR according to the Banff 2013 classification. We aimed to refine the PTCML criteria for an earlier diagnosis of cABMR. We retrospectively investigated ultrastructural features of 159 consecutive renal allografts and 44 nonallografts. The presence of serum donor-specific antibodies at the time of biopsy of allografts was also examined. Forty-three patients (27.0%) fulfilled the criteria of cABMR, regardless of PTCML, and comprised the cABMR group. Forty-one patients (25.8%) did not exhibit cABMR features and comprised the non-cABMR allograft control group. In addition, 15 zero-day wedge resections and 29 native kidney biopsies comprised the nonallograft control group. When the diagnostic accuracies of various PTCML features were assessed using the cABMR and non-cABMR allograft control groups, ≥4 PTCML, either circumferential or partial, in ≥2 peritubular capillaries of the three most affected capillaries exhibited the highest AUC value (0.885), greater than the Banff 2013 classification (0.640). None of the nonallograft control groups exhibited PTCML features. We suggest that ≥4 PTCML in ≥2 peritubular capillaries of the three most affected cortical capillaries represents the proper cutoff for cABMR.
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Affiliation(s)
- Heounjeong Go
- Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Sung Shin
- Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Young Hoon Kim
- Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Duck Jong Han
- Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Yong Mee Cho
- Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
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Peritubular Capillary Basement Membrane Multilayering in Renal Allograft Biopsies of Patients With De Novo Donor-Specific Antibodies. Transplantation 2016; 100:889-97. [PMID: 26413993 DOI: 10.1097/tp.0000000000000908] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Severe peritubular capillary basement membrane multilayering (PTCBML) is part of the Banff definition of chronic antibody-mediated rejection. We retrospectively investigated whether assessment of the mean number of layers of basement membrane (BM) around peritubular capillaries (PTC) can be used in a cohort of patients with de novo donor-specific antibodies (dnDSA) as an early marker to predict long-term antibody-mediated injury. METHODS This is a retrospective cohort study with 151 electron microscopy samples from 54 patients with dnDSA, assessed at around 1 year after transplantation, for a mean number of BM layers around PTC and in serial biopsies. Graft survival and time to transplant glomerulopathy (TG) development were estimated in survival analyses. RESULTS We found that a mean PTCBML count greater than 2.5 layers assessed in a sample of 25 PTCs around 1 year after transplantation is indicative of the development of TG in patients with dnDSA (P = 0.001). In addition, in patients with serial biopsies available for electron microscopy analysis, we could distinguish 2 groups: patients with a mean PTCBML count of 2.5 or less on all biopsies, and patients who developed greater than 2.5 layers at any time after transplantation. The latter group reflected dnDSA patients at risk for TG development (P < 0.001). In patients with dnDSA, PTCBML score added significantly to the sensitivity and specificity of prediction of TG compared with microcirculation injury score alone. CONCLUSIONS Our results highlight the potential value of assessing the mean number of BM in PTC for early prediction of progression to chronic antibody-mediated injury.
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