Determinants of long-term graft outcome in transplant glomerulopathy

Proposed Definitions of Antibody-Mediated Rejection for Use as a Clinical Trial Endpoint in Kidney Transplantation

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.

Focal Segmental Glomerulosclerosis Superimposed on Transplant Glomerulopathy: Implications for Graft Survival

INTRODUCTION

Transplant glomerulopathy (TG) is a morphological lesion resulting from chronic glomerular endothelium injury, and it is strongly associated with poor graft survival. TG coexisting with focal segmental glomerulosclerosis (FSGS) can be found in renal allograft biopsies, but few related studies are available.

METHODS

Consecutive kidney transplant recipients with biopsy-proven TG were studied retrospectively. Patients concomitant with FSGS were identified and compared with those without FSGS. The influence of FSGS on allograft outcomes was assessed using univariate and multivariate Cox regression models.

RESULTS

Of the 66 patients with TG, 40 (60.6%) had concomitant FSGS. TG patients with FSGS had higher proteinuria (median, 2.6 vs. 0.8 g/24 h, p < 0.001) and serum creatinine levels (median, 2.5 vs. 2.1 mg/dL, p = 0.04), lower serum albumin levels, higher chronic glomerulopathy (cg) score, larger glomerular tuft area, lower number of podocytes, and higher incidences of podocyte hyperplasia, pseudotubule formation, and diffuse foot process effacement than those without FSGS (all p < 0.05). The kidney allograft loss rate of patients with FSGS was higher than that of patients without FSGS (65.7% vs. 37.5%, p = 0.03). The presence of FSGS was independently associated with allograft loss in TG (hazard ratio (HR) = 3.42, 95% confidence interval (CI): 1.30-8.98, p = 0.01). Other independent predictors were proteinuria (HR = 1.18, 95% CI: 1.02-1.37, p = 0.02), estimated glomerular filtration rate (HR = 0.94, 95% CI: 0.91-0.97, p < 0.001), and panel reactive antibody (HR = 3.99, 95% CI: 1.14-13.99, p = 0.03). Moreover, FSGS (odds ratio (OR) = 4.39, 95% CI: 1.29-14.92, p = 0.02) and cg (OR = 5.36, 95% CI: 1.56-18.40, p = 0.01) were independent risk factors for proteinuria.

CONCLUSION

In this cohort of patients with TG, the presence of FSGS was strongly associated with more severe clinicopathological features and worse allograft survival.

Clinicopathologic Features and Risk Factors of Proteinuria in Transplant Glomerulopathy

Background: Transplant glomerulopathy (TG) is one of the main causes of post-transplant proteinuria (PU). The features and possible risk factors for proteinuria in TG patients are uncertain.

Methods: We investigated all patients who had biopsy-proven TG from 2000 to 2018 in our center. The clinical and histological data were compared between two groups with or without PU (cut-off = 0.3 g/day). Spearman correlation analysis was used to evaluate the relationship between PU and pathological changes. The risk factors for PU in TG patients were determined by multivariable logistic regression analysis.

Results: One hundred and twenty-five (75.76%) of all enrolled 165 TG patients had proteinuria ≥0.3 g/day at the time of biopsy. TG patients' PU level was significantly correlated with Banff lesion score cg (ρ = 0.247, P = 0.003), and mm (ρ = 0.257, P = 0.012). Systolic blood pressure ≥140 mmHg (OR 2.72, 95% CI 1.04–7.10, P = 0.041), diastolic blood pressure ≥90 mmHg (OR 4.84, 95% CI 1.39–16.82, P = 0.013), peak PRA ≥5% (OR 6.47, 95% CI 1.67–25.01, P = 0.007), positive C4d staining (OR 4.55, 95% CI 1.29–16.11, 0.019), tacrolimus-based regimen (OR 3.5, 95% CI 1.28–9.54, P = 0.014), and calcium channel blocker usage (OR 4.38, 95% CI 1.59–12.09, P = 0.004) were independent risk factors for PU.

Conclusions: Proteinuria is common in TG patients. systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, peak PRA ≥5%, positive C4d staining, tacrolimus-based regimen, and calcium channel blocker usage are associated with proteinuria in TG patients.

The relationship between proteinuria and allograft survival in patients with transplant glomerulopathy: a retrospective single-center cohort study

Proteinuria and transplant glomerulopathy (TG) are common in kidney transplantation. To date, there is limited knowledge regarding proteinuria in different types of TG and its relationship to allograft survival. A retrospective cohort analysis of TG patients from indication biopsies was performed to investigate the relationship of proteinuria, histology, and graft survival. One hundred and seven (57.5%) out of 186 TG patients lost their grafts with a median survival of 14 [95% confidence interval (CI) 10-22] months after diagnosis. Proteinuria ≥1 g/24 h at the time of biopsy was detected in 87 patients (46.8%) and the median of proteinuria was 0.89 (range 0.05-6.90) g/24 h. TG patients with proteinuria ≥1 g/24 h had worse 5-year graft survival (29.9% vs. 53.5%, P = 0.001) compared with proteinuria <1 g/24 h. Proteinuria was associated with graft loss in univariable Cox regression [hazard ratio (HR) 1.25, 95% CI, 1.11-1.41, P < 0.001], and in multivariable analysis (adjusted HR 1.26, 95% CI 1.11-1.42, P < 0.001) independent of other risk factors including creatinine at biopsy, positive C4d, history of rejection, and Banff lesion score mesangial matrix expansion. In this cohort of TG patients, proteinuria at indication biopsy is common and associated with a higher proportion of graft loss.

Urinary vitronectin identifies patients with high levels of fibrosis in kidney grafts

BACKGROUND

In kidney transplantation, fibrosis represents the final and irreversible consequence of the pathogenic mechanisms that lead to graft failure, and in the late stages it irremediably precedes the loss of renal function. The invasiveness of kidney biopsy prevents this condition from being frequently monitored, while clinical data are rather unspecific. The objective of this study was to find noninvasive biomarkers of kidney rejection.

METHODS

We carried out proteomic analysis of the urinary Extracellular Vesicles (uEVs) from a cohort of kidney transplant recipients (n = 23) classified according to their biopsy-based diagnosis and clinical parameters as interstitial fibrosis and tubular atrophy (IFTA), acute cellular rejection (ACR), calcineurin inhibitors toxicity (CNIT) and normal kidney function (NKF).

RESULTS

Shotgun mass spectrometry of uEV-proteins identified differential expression of several proteins among these different groups. Up to 23 of these proteins were re-evaluated using targeted proteomics in a new independent cohort of patients (n = 41) classified in the same diagnostic groups. Among other results, we found a differential expression of vitronectin (VTN) in patients displaying chronic interstitial and tubular lesions (ci and ct mean > 2 according to Banff criteria). These results were further confirmed by a pilot study using enzyme-linked immunosorbent assay (ELISA).

CONCLUSION

Urinary vitronectin levels are a potential stand-alone biomarker to monitor fibrotic changes in kidney transplant recipients in a non-invasive fashion.

Extracellular Matrix Injury of Kidney Allografts in Antibody-Mediated Rejection: A Proteomics Study

BACKGROUND

Antibody-mediated rejection (AMR) accounts for >50% of kidney allograft loss. Donor-specific antibodies (DSA) against HLA and non-HLA antigens in the glomeruli and the tubulointerstitium cause AMR while inflammatory cytokines such as TNFα trigger graft injury. The mechanisms governing cell-specific injury in AMR remain unclear.

METHODS

Unbiased proteomic analysis of laser-captured and microdissected glomeruli and tubulointerstitium was performed on 30 for-cause kidney biopsy specimens with early AMR, acute cellular rejection (ACR), or acute tubular necrosis (ATN).

RESULTS

A total of 107 of 2026 glomerular and 112 of 2399 tubulointerstitial proteins was significantly differentially expressed in AMR versus ACR; 112 of 2026 glomerular and 181 of 2399 tubulointerstitial proteins were significantly dysregulated in AMR versus ATN (P<0.05). Basement membrane and extracellular matrix (ECM) proteins were significantly decreased in both AMR compartments. Glomerular and tubulointerstitial laminin subunit γ-1 (LAMC1) expression decreased in AMR, as did glomerular nephrin (NPHS1) and receptor-type tyrosine-phosphatase O (PTPRO). The proteomic analysis revealed upregulated galectin-1, which is an immunomodulatory protein linked to the ECM, in AMR glomeruli. Anti-HLA class I antibodies significantly increased cathepsin-V (CTSV) expression and galectin-1 expression and secretion in human glomerular endothelial cells. CTSV had been predicted to cleave ECM proteins in the AMR glomeruli. Glutathione S-transferase ω-1, an ECM-modifying enzyme, was significantly increased in the AMR tubulointerstitium and in TNFα-treated proximal tubular epithelial cells.

CONCLUSIONS

Basement membranes are often remodeled in chronic AMR. Proteomic analysis performed on laser-captured and microdissected glomeruli and tubulointerstitium identified early ECM remodeling, which may represent a new therapeutic opportunity.

Predicting Clinical Outcome in Expanded Criteria Donor Kidney Transplantation: A Retrospective Cohort Study

Background:

The gaps in organ supply and demand necessitate the use of expanded criteria donor (ECD) kidneys.

Objective:

To identify which pre-transplant and post-transplant predictors are most informative regarding short- and long-term ECD transplant outcomes.

Design:

Retrospective cohort study.

Setting:

Single center, Quebec, Canada.

Patients:

The patients were 163 consecutive first-time ECD kidney only transplant recipients who underwent transplantation at McGill University Health Centre (MUHC) between January 1, 2008 and December 31, 2014 and had frozen section wedge procurement biopsies.

Measurements:

Short-term graft outcomes, including delayed graft function and 1-year estimated glomerular filtration rate (eGFR), as well as long-term outcomes including all-cause graft loss (defined as return to dialysis, retransplantation, and death with function).

Methods:

Pre-transplant donor, recipient, and transplant characteristics were assessed as predictors of transplant outcomes. The added value of post-transplant predictors, including longitudinal eGFR, was also assessed using time-varying Cox proportional hazards models.

Results:

In univariate analyses, among the pre-transplant donor characteristics, histopathologic variables did not show evidence of association with delayed graft function, 1-year post-transplant eGFR or all cause graft loss. Recipient age was associated with all-cause graft loss (hazard ratio: 1.038 [95% confidence interval: 1.002-1.075] and the model produced only modest discrimination (C-index: 0.590; standard error [SE]: 0.045). Inclusion of time-dependent post-transplant eGFR improved the model’s prediction accuracy (C-index: 0.711; SE = 0.047). Pre-transplant ECD characteristics were not associated with long-term survival, whereas post-transplant characteristics allowed better model discrimination.

Limitations:

Single-center study, small sample size, and potential incomplete capture of all covariate data.

Conclusions:

Incorporation of dynamic prediction models into electronic health records may enable timely mitigation of ECD graft failure risk and/or facilitate planning for renal replacement therapies. Histopathologic findings on preimplantation biopsies have a limited role in predicting long-term ECD outcomes.

Trial registration:

Not applicable.

Treatment with intravenous immunoglobulins and methylprednisolone may significantly decrease loss of renal function in chronic-active antibody-mediated rejection

Background

Chronic-active antibody mediated rejection (c-aABMR) is a major contributor to long-term kidney allograft loss. We conducted a retrospective analysis to establish the efficacy of treatment with intravenous immunoglobulins (IVIG) and pulse methylprednisolone (MP) of patients with c-aABMR.

Methods

Sixty-nine patients, in the period 2005–2017, with the diagnosis (suspicious for) c-aABMR that were treated with IVIG and MP were included. Patients were administered three doses of 1 g intravenous MP combined with a single dose of IVIG (1 g/kg body weight). Primary outcome was the decline in allograft function one year post treatment. Responders to IVIG-MP therapy were defined by an eGFR one year after treatment which was at least 25% above the projected allograft function.

Results

Patients showed an average decline in eGFR of 9.8 ml/min/1.73m² the year prior to treatment. Following treatment, a significant reduction (p < 0.001) in eGFR decline was observed (6.3 ml/min/1.73m²). Furthermore, a significant improvement in proteinuria was observed upon treatment (p < 0.001). Sixty-two percent (n = 43) of the patients were considered a responder and showed considerable slowing of graft function deterioration in the year after treatment (p < 0.001). Three and 5-year graft survival was significantly superior in responders.

Conclusions

More than 60% of patients with c-aABMR with a progressive decline in eGFR respond favorably to treatment with IVIG-MP resulting in a significant improvement of graft survival (Sablik, Am J Transplant 18, 2018).

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1385-z) contains supplementary material, which is available to authorized users.

Donor-specific Antibody Surveillance and Graft Outcomes in Pediatric Kidney Transplant Recipients

BACKGROUND

The development of de novo donor-specific antibodies (dnDSA) has been associated with rejection and graft loss in kidney transplantation, and DSA screening is now recommended in all kidney transplant recipients. However, the clinical significance of dnDSA detected by screening patients with a stable creatinine remains unclear.

METHODS

One hundred three patients younger than 18years receiving a first, kidney alone transplant between December 1, 2007, and December 31, 2013, underwent DSA screening every 3months for 2years posttransplant, with additional testing as clinically indicated. No treatment was given for DSAs in the absence of biopsy-proven rejection.

RESULTS

Twenty (19%) patients had dnDSA first detected on a screening test, and 13 (13%) patients had dnDSA first detected on a for-cause test. Mean follow-up time posttransplant was 4.4years. Screening-detected dnDSA was associated with an increased risk of rejection within 3years, microvascular inflammation, and C4d staining on a 2-year protocol biopsy. In a Cox proportional hazards regression, screening-detected dnDSA was not associated with time to 30% decline in estimated glomerular filtration rate (adjusted hazard ratio, 0.88; 95% confidence interval [CI], 0.30-2.00; P=0.598) or graft loss. dnDSA first detected on for-cause testing was associated with a 2.8 times increased risk of decline in graft function (95% CI, 1.08-7.27; P=0.034) and a 7.34 times increased risk of graft loss (95% CI, 1.37-39.23 P=0.020) compared with those who did not develop dnDSA.

CONCLUSIONS

The clinical setting in which dnDSA is first detected impacts the association between dnDSA and graft function. Further research is needed to clarify the role of dnDSA screening in pediatric kidney transplantation.

Switching renal transplant recipients to belatacept therapy: results of a real-life gradual conversion protocol

Conversion to belatacept immunosuppression is a therapeutic option for renal-transplant recipients with calcineurin inhibitors (CNI) toxicity, but it associates with high risk of acute rejection. Gradual conversion and serial immune monitoring with urinary chemokine CXCL9 may allow increasing safety of this maneuver. We converted kidney transplant recipients with signs of toxicity to CNI or other immunosuppressive drugs to belatacept over a 2-month period. We monitored renal function, metabolic profile, and circulating lymphocyte subsets. We also quantified urinary CXCL9 over a 12-month follow-up period. Between September 2016 and March 2017, 35 patients were successfully switched to belatacept immunosuppression at 3.3 (1.3-7.2) years after transplant. Two patients had a reversible rise in serum creatinine, associated with acute rejection in one case. Urinary CXCL9 increased before serum creatinine. After conversion, blood pressure and HbA1c significantly declined while eGFR and proteinuria remained stable. The percentage of circulating effector T cells and memory B cells significantly declined. Conversion from CNI to belatacept, in this setting, was feasible and safe, provided it was performed over a 2-month time-period. Monitoring urinary CXCL9 may further increase safety through earlier identification of patients at risk for acute rejection. The procedure associates with improved blood pressure, metabolic profile, and reduced circulating effector T and B cells.

Glomerular C3 Deposition Is an Independent Risk Factor for Allograft Failure in Kidney Transplant Recipients With Transplant Glomerulopathy

Introduction

Transplant glomerulopathy (TG) becomes increasingly prevalent in kidney transplant recipients over time, and it is strongly associated with allograft failure. To date, our prognostic biomarkers and understanding of the processes of immunologic injury in TG are limited.

Methods

This is a retrospective cohort analysis of kidney transplant recipients with TG (double contours of the glomerular basement membrane as defined by the chronic glomerulopathy score). Glomerular deposition of the complement protein C3 was determined, and its association with allograft survival was analyzed by Cox regression analysis.

Results

Of the 111 patients with TG, 72 (65%) had allograft failure, with a median follow-up time of 3 years from biopsy diagnosis of TG. C3-positive compared to C3-negative patients did not differ with respect to cause of end-stage renal disease, induction or maintenance immunosuppression, or sensitization. A greater proportion of patients with glomerular C3 deposition developed allograft failure compared to those with no C3 deposition (78% vs. 55%, P = 0.01). C3 deposition was independently associated with allograft failure in multivariate analyses (adjusted hazard ratio [HR] = 1.38, 95% confidence interval [CI] = 1.13−1.69, P = 0.002). There was no association between C4d or C1q deposition and allograft failure. Chronicity score was also associated with allograft failure in multivariate analysis (adjusted HR 1.26, 95% CI 1.12-1.41, P = 0.0001).

Conclusion

In this cohort of patients with TG, glomerular C3 deposition was independently associated with a higher risk of allograft failure. These findings identify glomerular C3 as a novel prognostic indicator in patients with TG.

Rituximab, plasma exchange and immunoglobulins: an ineffective treatment for chronic active antibody-mediated rejection

Background

Chronic active antibody-mediated rejection (c-aABMR) is an important cause of allograft failure and graft loss in long-term kidney transplants.

Methods

To determine the efficacy and safety of combined therapy with rituximab, plasma exchange (PE) and intravenous immunoglobulins (IVIG), a cohort of patients with transplant glomerulopathy (TG) that met criteria of active cABMR, according to BANFF’17 classification, was identified.

Results

We identified 62 patients with active c-aABMR and TG (cg ≥ 1). Twenty-three patients were treated with the combination therapy and, 39 patients did not receive treatment and were considered the control group. There were no significant differences in the graft survival between the two groups. The number of graft losses at 12 and 24 months and the decline of eGFR were not different and independent of the treatment. A decrease of eGFR≥13 ml/min between 6 months before and c-aABMR diagnosis, was an independent risk factor for graft loss at 24 months (OR = 5; P = 0.01). Infections that required hospitalization during the first year after c-aABMR diagnosis were significantly more frequent in treated patients (OR = 4.22; P = 0.013), with a ratio infection/patient-year of 0.65 and 0.20 respectively.

Conclusions

Treatment with rituximab, PE, and IVIG in kidney transplants with c-aABMR did not improve graft survival and was associated with a significant increase in severe infectious complications.

Trial registration

Agencia Española de Medicametos y Productos Sanitarios (AEMPS): 14566/RG 24161. Study code: UTR-INM-2017-01.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1057-4) contains supplementary material, which is available to authorized users.

Association between post-transplant uric acid level and renal allograft fibrosis: Analysis using Banff pathologic scores from renal biopsies

Several experimental studies implicate uric acid in renal injury and fibrosis. The objective of this study was to examine the association between uric acid level and allograft fibrosis after kidney transplantation. 241 adult patients who underwent kidney transplantation between 2003 and 2014 were divided into three groups according to the sex specific tertiles of mean uric acid level within the first post-transplant year. The renal biopsies performed during 1 to 5 post-transplant year were analyzed to compare the degree of interstitial fibrosis and tubular atrophy (IF/TA). Mean interval between kidney transplantation and biopsy was similar between groups (23.7 ± 15.3 vs. 30.0 ± 18.6 vs. 27.5 ± 18.5 months, P = 0.072). The higher tertile uric acid level was, the more advanced grade of IF/TA was shown (P = 0.001). Multivariate analysis identified uric acid tertile was independent risk factor for severe IF/TA (odds ratio [95% confidence interval] was 3.16 [1.13-8.82] for tertile 2 and 3.70 [1.25-10.93] for tertile 3, versus tertile 1, respectively). Other independent factors were estimated glomerular filtration rate at 1year post-transplant (0.80 [CI 0.65-0.98]) and biopsy-proven rejection (2.34 [1.05-5.21]). Graft survival over 10 years was significantly lower in tertile 3 (P = 0.041). The results showed that higher uric acid level after kidney transplantation was associated with more severe IF/TA.

Correlations between donor-specific antibodies and non-adherence with chronic active antibody-mediated rejection phenotypes and their impact on kidney graft survival

Chronic-active antibody-mediated rejection (CAABMR) is associated with poor kidney graft survival and has no clear effective treatment. Forty-one cases of CAABMR were detected in indication graft biopsies and evaluated according to current Banff classification. We investigated the impact of concurrent donor-specific antibodies (DSA) and their characteristics, together with non-adherence regarding immunosuppression on CAABMR histopathological phenotypes and prognosis. Twenty-four (59%) patients had detectable DSA at biopsy, with 15 of them being considered non-adherent. Graft function at biopsy was similar in DSA (+) and (-) patients. DSA (+) patients had significantly higher tubulointerstitial inflammation (i and ti) and acute humoral (g+ptc+v+C4d) composite score than DSA (-). DSA (+)/non-adherent cases presented additionally with increased microvascular inflammation (ptc and v), besides having a distinctively lower ah score. C1q DSA strength was higher (P = .046) in non-adherent patients and correlated closely with C4d score (P = .002). Lower graft function and ah score, higher proteinuria and ci + ct score, and, separately per each model, DSA (+) (HR = 2.446, P = .034), DSA (+)/non-adherent (HR = 3.657, P = .005) and DSA (+)/C1q (+) (HR = 4.831, P = .003) status were independent predictors of graft failure. CAABMR with concomitant DSA pose a higher risk of graft failure. Adherence should be evaluated, and histopathological phenotyping and DSA characterization may add critical information.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Interstitial fibrosis is the critical determinant of impaired renal function in transplant glomerulopathy

AIM

Transplant glomerulopathy (TG) is a feature of chronic antibody-mediated injury in the glomerular capillaries in renal transplant recipients. TG is generally associated with proteinuria; however, renal function at the diagnosis of TG varies. This study aimed to determine which morphological abnormalities are associated with renal function and proteinuria at the diagnosis of TG.

METHODS

A total of 871 renal transplantations were performed at Tokyo Women's Medical University between 2005 and 2013. TG was diagnosed in 127 biopsies from 58 (6.7%) recipients. Renal function was evaluated by the estimated glomerular filtration rate (eGFR). Proteinuria was assessed by a dipstick test: positive for +1 and over.

RESULTS

At diagnosis, of 127 biopsies, 72, 37, and 18 had mild, moderate, and severe TG (Banff cg). The severity of TG was not associated with decreased eGFR at the time of biopsy (cg1: 36.1 ± 14.8, cg2-3: 38.8 ± 14.5 mL/min per 1.73 m(2) , P = 0.25), whereas the severity of interstitial fibrosis (IF) (Banff ci) was significantly associated with decreased eGFR (ci0-1: 42.75 ± 13.32, ci2-3: 27.69 ± 11.94 mL/min per 1.73 m(2) , P < 0.0001). The multivariate analysis revealed that IF was the only independent risk factors for decreased eGFR (OR = 4.38, P = 0.0006). Meanwhile, TG was identified as the only independent risk factor for the incidence of proteinuria (OR = 2.67, P = 0.014).

CONCLUSION

Interstitial fibrosis was a critical determinant of impaired renal function at the diagnosis of TG. The severity of TG was significantly associated with proteinuria, but did not contribute to renal dysfunction.

Six-year outcomes in broadly HLA-sensitized living donor transplant recipients desensitized with intravenous immunoglobulin and rituximab

Desensitization with intravenous immunoglobulin (IVIG) and rituximab can improve transplantation rates in broadly sensitized kidney transplant recipients. However, long-term outcomes are lacking. Here we analyze long-term outcomes in living donor kidney transplant recipients desensitized with this regimen and compare them to low-risk recipients. Living donor kidney transplants that took place between July 2006 and December 2010 were considered retrospectively. The primary end point of the study was death-censored allograft survival at last follow-up. Secondary end points included patient survival, incidence of rejection, glomerular filtration rate (GFR), and proteinuria. There were 66 sensitized and 111 low-risk patients included. Average follow-up was 68 months. There was no difference in long-term patient or graft survival. The rate of rejection was similar in the groups with more early rejection in the sensitized group and more late rejection in the low-risk group. There was more antibody-mediated rejection in the sensitized group. Estimated GFR was similar during the follow-up period. Risk factors for rejection included a positive cross-match (HR: 2.4 CI: 1.35-4.40) and age (HR: 0.97 CI: 0.95-0.99). Desensitization with IVIG and rituximab has good long-term results with graft outcomes similar to non-HLA-sensitized patients despite higher immunologic risk.

2013 Banff Criteria for Chronic Active Antibody-Mediated Rejection: Assessment in a Real-Life Setting

Significant changes in the criteria for chronic active antibody-mediated rejection (CAABMR) were made in the Banff 2013 classification. These modifications expanded the number of patients diagnosed with CAABMR, with undetermined clinical significance. We compared the 2007 and 2013 criteria for the composite end point of death-censored graft failure or doubling of serum creatinine in 123 patients meeting the criterion related to the morphologic evidence of chronic tissue injury. In all, 18% and 36% of the patients met the 2007 and 2013 criteria, respectively. For the criterion related to antibody interaction with endothelium, only 25% were positive based on the 2007 definition compared with 82% using the 2013 definition. Cox modeling revealed that a 2013 but not a 2007 diagnosis was associated with the composite end point (adjusted hazard ratio 2.5 [95% confidence interval (CI) 1.2-5.2] vs. 1.6 [95% CI 0.7-3.8], respectively). The 2013 criterion based on both the C4d score and the glomerulitis plus peritubular capillaritis score (g+ptc) was more strongly associated with the end point than the 2007 criterion based only on C4d; however, when dissected by component, only the C4d component was significant. The association with clinical outcomes improved with the 2013 criteria. This is related to the new C4d threshold but not to the g+ptc ≥2 component.

MicroRNA biomarkers in clinical renal disease: from diabetic nephropathy renal transplantation and beyond

Chronic Kidney Disease (CKD) is a common health problem affecting 1 in 12 Americans. It is associated with elevated risks of mortality, cardiovascular disease, and high costs for the treatment of renal failure with dialysis or transplantation. Advances in CKD care are impeded by the lack of biomarkers for early diagnosis, assessment of the extent of tissue injury, estimation of disease progression, and evaluation of response to therapy. Such biomarkers should improve the performance of existing measures of renal functional impairment (estimated glomerular filtration rate, eGFR) or kidney damage (proteinuria). MicroRNAs (miRNAs) a class of small, non-coding RNAs that act as post-transcriptional repressors are gaining momentum as biomarkers in a number of disease areas. In this review, we examine the potential utility of miRNAs as promising biomarkers for renal disease. We explore the performance of miRNAs as biomarkers in two clinically important forms of CKD, diabetes and the nephropathy developing in kidney transplant recipients. Finally, we highlight the pitfalls and opportunities of miRNAs and provide a broad perspective for the future clinical development of miRNAs as biomarkers in CKD beyond the current gold standards of eGFR and albuminuria.

Clinical, Histological, and Molecular Markers Associated With Allograft Loss in Transplant Glomerulopathy Patients

BACKGROUND

We aimed to investigate the clinical, histopathological, and molecular factors associated with allograft loss in transplant glomerulopathy (TGP) patients.

METHODS

Of the 525 patients who underwent clinically indicated kidney biopsies, 52 (10%) had diagnosis of TGP. Gene expression profiles of 28 TGP and 11 normal transplant kidney biopsy samples were analyzed by Affymetrix HuGene 1.0 ST expression arrays.

RESULTS

Over a median follow up of 23 months (1-46 months) after the diagnosis of TGP by biopsy, 17 patients (32%) lost their allografts at a median of 16 months (1-44 months). There was no difference between the 2 groups in terms of any demographic variables, serum creatinine, panel reactive antibody levels, donor-specific antibody frequency, or mean fluorescence intensity values. Patients who lost their allograft had a significantly higher median spot protein to creatinine ratio 2.81 (1.20-6.00) compared to no graft loss patients 1.16 (0.15-2.53), (P < 0.01), and a trends toward a higher mean chronic glomerulopathy (cg) score (1.65 ± 0.93 vs 1.11 ± 0.93) (P = 0.05). There was also no difference in microvascular inflammation or any other Banff injury scores between the 2 groups. Although 117 gene transcripts were upregulated in both groups, 86 and 57 were upregulated in graft loss and functioning allograft groups, respectively. There were significantly increased levels of intragraft endothelial cell-associated transcripts, gene transcripts associated with complement cascade, interleukins and their receptors and granulysin in graft loss patients compared to patients with a functioning allograft.

CONCLUSION

Our results demonstrate differential intragraft gene expression profiles in TGP patients with allograft loss.

New insights regarding chronic antibody-mediated rejection and its progression to transplant glomerulopathy

PURPOSE OF THIS REVIEW

To discuss new insights regarding chronic antibody-mediated rejection (CAMR) and its progression to transplant glomerulopathy. We will describe the progression to transplant glomerulopathy from a histologic perspective and provide updates on what is known about its pathophysiology, prognosis, and potential therapy.

RECENT FINDINGS

Transplant glomerulopathy is a major contributor to long-term renal allograft loss and is most often associated with CAMR. On the basis of protocol biopsies, we have found that 3.5% of conventional transplants and 27.5% of positive crossmatch kidney transplants have transplant glomerulopathy at 1 year. The pathophysiology of the process is largely unknown, but complement activation was previously thought to be essential. However, CAMR appears to develop despite terminal complement blockade and many C4d negative cases of CAMR have been identified. Thus, complement independent mechanisms, such as direct endothelial cell activation and the infiltration of natural killer cells and monocytes, are likely key to the development of transplant glomerulopathy.

SUMMARY

Transplant glomerulopathy is often the result of CAMR and leads to allograft loss. It is characterized by distinctive histologic changes, and its pathophysiology is a multifaceted process involving both innate and adaptive immunity. Despite advances in the understanding of this condition, no effective therapy exists.

Acute and chronic antibody-mediated rejection in pediatric kidney transplantation

Acute antibody-mediated rejection is a diagnostic challenge in renal transplantation medicine. However, it is an important diagnosis to make, since chronic antibody-mediated rejection (CAMR) is the main cause of long-term graft loss. Antibody-mediated rejection is diagnosed by detecting donor-specific antibodies (DSAs) in the blood in combination with observing typical histomorphological signs in kidney biopsy, as described in the Banff classification. Therapy is based on the removal of DSAs by administering intravenous immunoglobulins (IVIGs), plasmapheresis, or immunoadsorption. Reoccurrence of antibodies is diminished by the use of rituximab, increased immunosuppression, and in some cases additional experimental substances. A combination of these techniques has been shown to be successful in the majority of cases of acute and chronic antibody-mediated rejection. Routine DSA monitoring is warranted for early detection of antibody-mediated rejection.

Renal function decline in recipients and donors of kidney grafts: role of aortic stiffness

BACKGROUND/AIMS

Renal function decreases over time as a result of reduction in the number of functioning nephrons with age. In recipients and donors of kidney grafts, renal function decline may be linked differently to various parameters, namely arterial stiffness.

METHODS

We conducted a prospective cohort study including 101 recipients of kidney grafts and their donors aiming at determining the factors correlated to the renal function decline over time. Aortic stiffness was evaluated by the non-invasive measurement of aortic pulse wave velocity. The glomerular filtration rate was estimated using the Modification of Diet in Renal Disease (MDRD) equation and the annualized change was determined.

RESULTS

Decline in renal function was estimated at 1-year post-transplantation and annually thereafter (median follow-up 8 years, range 3.6-18.3), as the mean of the annualized decrease in the glomerular filtration rate. In recipients, filtration rate decreased by 4.8 ± 19.7 ml/min/1.73 m(2) the first post-transplant year and at a yearly rate of 2.2 ± 3.8 ml/min/1.73 m(2) thereafter. The first-year decline was related to smoking and acute rejection. Later decline was significantly associated with donor age and aortic stiffness. In living donors, renal function decline after the first year corresponded to 0.7 ml/min/1.73 m(2), was significantly lower than that of recipients (p < 0.001), and was determined by donor age at nephrectomy.

CONCLUSION

Recipients of kidney grafts show a glomerular filtration rate decline over time that is significantly associated with donor age and aortic stiffness after the first post-transplant year, while donors demonstrate a lower decline that is mostly determined by age at nephrectomy.

Electron microscopy contribution to diagnosing transplant glomerulopathy: a single-center experience

BACKGROUND

Transplant glomerulopathy (TG) may occur early after transplantation, and electron microscopy may contribute to diagnose it.

METHODS

We analyzed kidney transplant biopsies from September 2009 to September 2012 to identify the presence of histologic changes associated with TG.

RESULTS

Forty-eight biopsies from 65 patients, met the study criteria and were evaluated. The average evolution time of transplantation was 13.6 months. Sixty percent of patients received deceased-donor renal transplants, and biopsies were performed per protocol in most cases. Electron microscopy diagnosed the presence of changes associated with TG in 23% of patients. Light microscopy was not useful in the diagnosis of such graft pathology. The average transplantation time was significantly higher in patients with TG compared to patients without TG (20.6 mo vs 11.5 mo; P = .03). Light microscopy diagnosed mild interstitial fibrosis/tubular atrophy in 27 patients, of which 6 had early changes of TG according to the analysis by electron microscopy.

CONCLUSIONS

Electron microscopy improves accurate diagnosis of TG, in patients both with and without graft dysfunction. It also allows diagnosis of early TG and thereby identification of patients who may have lower graft survival.

A systematic review of the role of C4d in the diagnosis of acute antibody-mediated rejection

In this study, we conducted a systematic review of the literature to re-evaluate the role of C4d in the diagnosis of acute antibody-mediated rejection of kidney allografts. Electronic databases were searched until September 2013. Eligible studies allowed derivation of diagnostic tables for the performance of C4d by immunofluorescence or immunohistochemistry with comparison to histopathological features of acute antibody-mediated rejection and/or donor-specific antibody (DSA) assays. Of 3492 unique abstracts, 29 studies encompassing 3485 indication and 868 surveillance biopsies were identified. Assessment of C4d by immunofluorescence and immunohistochemistry exhibited slight to moderate agreement with glomerulitis, peritubular capillaritis, solid-phase DSA assays, DSA with glomerulitis, and DSA with peritubular capillaritis. The sensitivity and specificity of C4d varied as a function of C4d and comparator test thresholds. Prognostically, the presence of C4d was associated with inferior allograft survival compared with DSA or histopathology alone. Thus, our findings support the presence of complement-dependent and -independent phenotypes of acute antibody-mediated rejection. Whether the presence of C4d in combination with histopathology or DSA should be considered for the diagnosis of acute antibody-mediated rejection warrants further study.

Histopathologic features of transplant glomerulopathy associated with response to therapy with intravenous immune globulin and rituximab

Transplant glomerulopathy (TG) is associated with poor long-term allograft survival and is often accompanied by microcirculation inflammation. Histopathologic scoring may inform prognosis and help guide therapy. We retrospectively assessed 33 patients with biopsy-proven TG. All biopsies were given a glomerulitis (g) and peritubular capillaritis (ptc) score. We determined allograft survival and serum creatinine stability in three different score groups: g < 2 and ≥ 2, ptc < 2 and ≥ 2, and (g + ptc) < 4 and ≥ 4. We assessed the impact of treatment with intravenous immune globulin (IVIG) and rituximab on outcomes. Graft survival and serum creatinine stability did not differ in each of the histopathologic score groups. Higher-score groups were associated with the presence of concomitant antibody-mediated rejection and were more likely to receive IVIG and rituximab. Treatment with IVIG and rituximab resulted in stability of serum creatinine within the higher-score groups, but not in the lower-score groups. Stabilization of serum creatinine was associated with an improvement in donor-specific antibody. Histopathologic scoring in kidney allograft biopsies with TG may help guide treatment. The combination of IVIG and rituximab appears to be beneficial in patients whose biopsies have moderate or severe microvascular injury.

Transplant glomerulopathy: the interaction of HLA antibodies and endothelium

Transplant glomerulopathy (TG) is a major cause of chronic graft dysfunction without effective therapy. Although the histological definition of TG is well characterized, the pathophysiological pathways leading to TG development are still poorly understood. Electron microscopy suggests an earlier appearance of TG and suggests that endothelial cell injury is the first sign of the disease. The pathogenic role of human leukocyte antigen (HLA) antibodies in endothelial cells has been described in acute vascular and humoral rejection. However the mechanisms and pathways of endothelial cell injury by HLA antibodies remain unclear. Despite the description of different causes of the morphological lesion of TG (hepatitis, thrombotic microangiopathy), the strong link between TG and chronic antibody mediated rejection suggests a major role for HLA antibodies in TG formation. In this review, we describe the effect of classes I or II HLA-antibodies in TG and especially the implication of donor specific antibodies (DSA). We update recent studies about endothelial cells and try to explain the different signals and intracellular pathways involved in the progression of TG.

Picking transplant glomerulopathy out of the CAN: evidence from a clinico-pathological evaluation

Background

Since the term chronic allograft nephropathy (CAN) was removed from the Banff scheme in 2005, transplant glomerulopathy (TG) has been regarded as a clinicopathological entity that is one of the major causes of graft loss. To assess the distinction between CAN and TG, we performed a comprehensive evaluation comparing TG with traditional CAN.

Methods

We compared the clinicopathological features of 43 cases of TG with 43 matched cases of non-TG CAN (non-TG group) after renal transplantation. TG was diagnosed by light microscopy based on the double contours of the glomerular basement membranes, and the Banff 97 classification system was used to score TG severity (cg0-3).

Results

Compared to the control group, we found a significantly higher incidence of positivity for human leukocyte antigen class-I and II antibodies, a higher incidence of hepatitis C virus (HCV) infection, and poorer graft survival in TG patients. Clinically, TG was associated with a higher prevalence of proteinuria, hematuria, anaemia and hypoalbuminemia. Histologically, TG strongly correlated with antibody related microcirculatory injuries, including glomerulitis, peritubular capillaritis and peritubular capillary (PTC) C4d deposition. Interestingly, the TG patients showed a significantly higher incidence of IgA deposition than the control patients. C4d-positive TG was correlated with higher TG and PTC scores, and PTC C4d deposition was correlated with a more rapid progression to graft dysfunction. TG accompanied by HCV infection was associated with heavier proteinuria, higher TG and C4d scores, and poorer graft survival.

Conclusions

TG presents clinicopathological features that are distinct from non-TG cases and leads to poorer outcomes. PTC C4d deposition is related to a more rapid progression to graft loss, suggesting ongoing antibody reactivity. HCV-positive TG is a more severe sub-entity, that requires further investigation.

Intragraft gene expression in positive crossmatch kidney allografts: ongoing inflammation mediates chronic antibody-mediated injury

We studied intragraft gene expression profiles of positive crossmatch (+XM) kidney transplant recipients who develop transplant glomerulopathy (TG) and those who do not. Whole genome microarray analysis and quantitative rt-PCR were performed on RNA from protocol renal allograft biopsies in three groups: (1) +XM/TG+ biopsies before and after TG; (2) +XM/NoTG; and (3) negative crossmatch kidney transplants (control). Microarray comparisons showed few differentially expressed genes between paired biopsies from +XM/TG+ recipients before and after the diagnosis of TG. Comparing +XM/TG+ and control groups, significantly altered expression was seen for 2447 genes (18%) and 3200 genes (24%) at early and late time points, respectively. Canonical pathway analyses of differentially expressed genes showed inflammatory genes associated with innate and adaptive immune responses. Comparing +XM/TG+ and +XM/NoTG groups, 3718 probe sets were differentially expressed but these were over-represented in only four pathways. A classic accommodation phenotype was not identified. Using rt-PCR, the expression of inflammatory genes was significantly increased in +XM/TG+ recipients compared to the +XM/NoTG and control groups. In conclusion, pretransplant donor-specific anti-HLA antibodies results in a gene expression profile characterized by inflammation and cellular infiltration and the majority of +XM grafts are exposed to chronic injury.

Accompanying renal injuries did not impact graft survival in patients with transplant glomerulopathy

Transplant glomerulopathy (TG) a morphological feature of chronic active antibody-mediated rejection, is associated with donor-specific antibody, peritubular capillary deposition of C4d, and multilayering of peritubular capillary basement membranes. To evaluate the significance of accompanying nonimmunologic injuries in TG, we retrospectively reviewed 2839 renal allograft cases at our institute among which TG was diagnosed in 81 patients (2.9%). Among TG cases, 48 samples showed accompanying diseases such as chronic calcineurin inhibitor toxicity, hepatitis viral infection, posttransplant diabetes, and glomerulonephritis. Comparing the pure form of TG with TG-mixed diseases, there was no difference in patient demography, serum creatinine values, and proteinuria. Among histological parameters, severe hyalinosis was more frequently observed among the TG plus other diseases group. The two groups did not show significant difference in graft survival (P = .216).

Overlapping pathways to transplant glomerulopathy: chronic humoral rejection, hepatitis C infection, and thrombotic microangiopathy

Transplant glomerulopathy (TG) has received much attention in recent years as a symptom of chronic humoral rejection; however, many cases lack C4d deposition and/or circulating donor-specific antibodies (DSAs). To determine the contribution of other causes, we studied 209 consecutive renal allograft indication biopsies for chronic allograft dysfunction, of which 25 met the pathological criteria of TG. Three partially overlapping etiologies accounted for 21 (84%) cases: C4d-positive (48%), hepatitis C-positive (36%), and thrombotic microangiopathy (TMA)-positive (32%) TG. The majority of patients with confirmed TMA were also hepatitis C positive, and the majority of hepatitis C-positive patients had TMA. DSAs were significantly associated with C4d-positive but not with hepatitis C-positive TG. The prevalence of hepatitis C was significantly higher in the TG group than in 29 control patients. Within the TG cohort, those who were hepatitis C-positive developed allograft failure significantly earlier than hepatitis C-negative patients. Thus, TG is not a specific diagnosis but a pattern of pathological injury involving three major overlapping pathways. It is important to distinguish these mechanisms, as they may have different prognostic and therapeutic implications.

Chronic calcineurin inhibitor nephrotoxicity-lest we forget

Calcineurin inhibitor (CNI) nephrotoxicity was recognized in Cambridge in the late 1970s. The vasoconstrictor impact of cyclosporine (CsA) and to a lesser extent tacrolimus, in both acute and chronic settings, results from a decrease in vasodilators and increase in vasconconstrictors while direct tubular toxicity results from blockade of mitochondrial permeability transition pores and inhibition of prolyl isomerase. A biopsy of native kidneys of recipients of CNIs reveals nephrotoxicity as the most common pathological diagnosis with chronic CNI toxicity and hypertension the primary problems. A long-term study of randomized clinical trials with up to 20 years of follow-up shows inferiority of both renal function and graft survival for continuous CsA compared to either CsA withdrawal or continuous azathioprine and prednisolone. Pathological hallmarks of chronic CNI nephrotoxicity include stripped interstitial fibrosis, arteriolar hyalinosis and glomerular sclerosis, but with the exception of nodular arteriolar hyalinosis the findings are non specific. The model for chronic renal allograft loss must be multifactorial with both immune and nonimmune factors operating dependent upon an individual's risk factors for cell and/or antibody-mediated rejection, CNI nephrotoxicity and recurrent disease. Better outcomes will require early diagnosis and individualization of therapy dependent upon the dominant mechanisms impacting each patient. The revisionist view put forward by some senior, experienced and thoughtful individuals, challenges the concept of chronic CNI nephrotoxicity as an important clinical entity. By implication, the view that appears to be promoted is as follows: we need not fear-prolonged exposure to CNIs, and in seeking better long-term solutions for transplant recipients, we have forgotten alloimmunity. It is thus apparent that we must revisit the data and again question the basis for chronic CNI nephrotoxicity in current clinical practice. This contribution to the debate will focus on the evidence that CNIs are nephrotoxic and that their impact needs to be limited if we are to improve long-term outcomes after transplantation, leaving others to promote the contrary perspective and perhaps also to reflect on the largely unproven impact of the steroid avoidance and other minimization strategies so prevalent today.