Reproducibility studies on arteriolar hyaline thickening scoring in calcineurin inhibitor-treated renal allograft recipients

Metabolomic Profiling of Plasma, Urine, and Saliva of Kidney Transplantation Recipients

Kidney biopsy is commonly used to diagnose kidney transplant dysfunction after transplantation. Therefore, the development of minimally invasive and quantitative methods to evaluate kidney function in transplant recipients is necessary. Here, we used capillary electrophoresis-mass spectrometry to analyze the biofluids collected from transplant recipients with impaired (Group I, n = 31) and stable (Group S, n = 19) kidney function and from donors (Group D, n = 9). Metabolomics analyses identified and quantified 97 metabolites in plasma, 133 metabolites in urine, and 108 metabolites in saliva. Multivariate analyses revealed apparent differences in the metabolomic profiles of the three groups. In plasma samples, arginine biosynthesis and purine metabolism between the I and S Groups differed. In addition, considerable differences in metabolomic profiles were observed between samples collected from participants with T cell-mediated rejection (TCR), antibody-mediated rejection, and other kidney disorders (KD). The metabolomic profiles in the three types of biofluids showed different patterns between TCR and KD, wherein 3-indoxyl sulfate showed a significant increase in TCR consistently in both plasma and urine samples. These results suggest that each biofluid has different metabolite features to evaluate kidney function after transplantation and that 3-indoxyl sulfate could predict acute rejection.

Impacts of dosing and drug withdrawal period on tacrolimus-based triple therapy in a non-human primate renal transplantation model

Non-human primate (NHP) renal transplantation models are widely used vivo models for researching new immunosuppressive therapies including allograft tolerance strategies. To enroll animals into a tolerance study, an immunosuppressive regimen that efficiently establishes stable renal function in NHPs is needed. Here, we assessed the effect of triple therapy comprising 2.0 mg/kg tacrolimus, mycophenolate mofetil and a steroid and its success rate for achieving stable renal function. In addition, to predict the pathophysiological consequences of withdrawing immunosuppressants, an indispensable process after induction of tolerance, we also assessed changes in the stable renal state maintained by triple therapy after drug withdrawal. Six cynomolgus monkeys were used. The median survival time was >176 days over the dosing period and 45 days after drug withdrawal. The triple therapy successfully induced stable graft function without calcineurin inhibitor nephrotoxicity in three of six recipients, although adopting trough-dependent tacrolimus dose adjustment rather than a preset dose regimen could improve on the present strategy. Further, drug withdrawal led to deterioration of renal function, de novo donor specific antibody production and increased the memory/naïve T cell ratio within two weeks post drug withdrawal. We expect that these findings contribute to establish one of the choices for animal model for evaluating future tolerance therapy for renal transplantation.

CKD in Recipients of Nonkidney Solid Organ Transplants: A Review

Chronic kidney disease (CKD) after solid organ transplant is a common clinical presentation, affecting 10% to 20% of liver, heart and lung transplant recipients and accounting for approximately 5% of the kidney transplant waiting list. The causes of CKD are different for different types of transplants and are not all, or even predominantly, due to calcineurin inhibitor toxicity, with significant heterogeneity particularly in liver transplant recipients. Many solid organ transplant recipients with advanced CKD benefit from kidney transplantation, but have a higher rate of death while waitlisted and higher mortality following transplant than the general kidney failure population. Recent organ allocation policies and proposals have attempted to address the appropriate identification and prioritization of candidates in need of a kidney transplant, either simultaneous with or following non-kidney transplant. Future research should focus on predictive factors for individuals identified at high risk for progression to kidney failure and death, and strategies to preserve kidney function and minimize the CKD burden in this unique patient population.

Impact of primary diabetic nephropathy on arteriolar hyalinosis lesions in patients following kidney transplantation

AIM

Arteriolar hyalinosis (AH) is a common lesion in allograft biopsies taken following kidney transplantation. Recent studies have shown that severe AH may predict transplant outcomes and provide information about previous exposure to certain drugs, such as calcineurin inhibitors (CNI). However, the incidence of AH as a direct result of diabetic nephropathy (DN) after kidney transplantation has not been fully evaluated. This study aimed to assess the impact of primary DN on the development of AH lesions in patients who underwent kidney transplantation.

METHODS

Eighty-three patients who underwent living-donor kidney transplantation between April 2005 and June 2015 were enrolled in this study. A total of 33 patients had DN prior to transplantation. Allograft biopsies were scored according to the Banff classification, and the relationship between the individual histological lesions and clinical baseline data was assessed.

RESULTS

At early biopsy (3-12 months), there were no differences in the rates of AH lesions between the DN group and the non-DN group (ah ≥ 1: 37% vs. 41.3%, P = 0.719; aah ≥ 1: 14.8% vs. 6.5%; P = 0.453). However, there were significant differences between the groups in biopsies taken more than 3 years after the transplant (ah ≥ 2: 83.3% vs. 36.8%, P = 0.013; aah ≥ 2: 66.7% vs. 21.1%, P = 0.011). Multivariable analysis showed that both the length of time after transplantation and the presence of DN were independent risk factors for ah ≥ 2 (odds ratio [OR]: 2.55, 95% confidence interval [CI]: 1.47-19.54, P = 0.011) and aah ≥ 2 (OR: 7.55, 95% CI: 1.49-38.33, P = 0.015).

CONCLUSION

This is the first report showing that the presence of primary DN disease contributes to the development of severe AH late in the course after kidney allografts.

Procurement Biopsy Findings Versus Kidney Donor Risk Index for Predicting Renal Allograft Survival

BACKGROUND

Efforts to maximize transplantation by matching organ quality to recipient longevity require reliable tools. The US kidney allocation system uses the Kidney Donor Risk Index (KDRI) for this purpose, and many centers additionally rely on donor biopsies. The Leuven score combines donor age with procurement histology (glomerulosclerosis and interstitial fibrosis/tubular atrophy) to predict allograft survival.

METHODS

We compared KDRI with Leuven scores for associations with kidney discard, delayed graft function, and allograft function and survival. We used Cox, modified Poisson, and linear regression to calculate risks based on KDRI and (separately) Leuven scores, adjusting for important transplant and recipient variables.

RESULTS

From 890 donors, 1729 kidneys were procured and biopsied. Five hundred eighty-five (34%) kidneys were discarded. Median donor age was 53 years (interquartile range [IQR], 44-61 years). Median KDRI and Leuven scores were 1.56 (IQR, 1.28-1.90) and 59 (IQR, 49-69). Relative risk for discard was 1.21 (95% confidence interval [CI], 1.17-1.24) per 0.2-unit increase in KDRI and 1.38 (1.31-1.46) per 10-unit increase in Leuven score. Adjusted relative risks for delayed graft function were 0.98 (95% CI, 0.94-1.02) and 0.94 (95% CI, 0.90-0.99), adjusted hazard ratios for graft failure were 1.10 (95% CI, 1.04-1.16) and 1.11 (95% CI, 1.02-1.21), and adjusted linear regression coefficients for 3-year estimated glomerular filtration rate were -3.88 (-4.63 to -3.13) and -5.18 (-6.19 to -4.18).

CONCLUSIONS

In kidneys clinically selected for procurement biopsy, the Leuven score was more strongly associated with discard but performed similarly to KDRI for predicting transplant outcomes, suggesting the need to reevaluate current procurement biopsy practices. Given modest associations for both tools; however, neither KDRI nor the Leuven score should be used in isolation for individual organ acceptance decisions.

A molecular biopsy test based on arteriolar under-hyalinosis reflects increased probability of rejection related to under-immunosuppression

Calcineurin inhibitor immunosuppressive drugs induce changes such as arteriolar hyalinosis (ah) in kidney transplants, raising the possibility that molecular changes in biopsies related to histologic ah can provide information about drug exposure. We hypothesized that molecular changes associated with less-than-expected hyalinosis might highlight a subpopulation of patients with under-immunosuppression/nonadherence at intermediate times of biopsy posttransplant (TxBx). Using gene expression data from 562 indication biopsies, we developed a molecular classifier for predicting the expected ah lesions (Mah ) at a particular TxBx. Mah -scores increased linearly with log(TxBx), but some biopsies had lower scores than expected for TxBx. The deviation of individual Mah -scores below the predicted regression line of Mah -scores vs TxBx is defined as "low hyalinosis index." Low hyalinosis indices were frequent in biopsies between 3 months and 3 years posttransplant, particularly among biopsies lacking histologic hyalinosis (ah0), and were associated with T cell-mediated rejection and a subset of recent-onset antibody-mediated rejection without glomerular double contours. In patients with medical records available for review, low hyalinosis indices were frequently associated with physician-recorded concerns about nonadherence (suspected or proven). We conclude that the Mah classifier and hyalinosis index identify indication biopsies with rejection for which the possibility of patient nonadherence should be considered.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

Nox2 and Cyclosporine-Induced Renal Hypoxia

BACKGROUND

We hypothesized that nicotinamide adenosine diphosphate oxidase 2 (Nox2) plays an important role in cyclosporine A (CsA)-induced chronic hypoxia.

METHODS

We tested this hypothesis in Fisher 344 rats, C57BL/6 J wild type and Nox2-/- mice, and in liver transplant recipients with chronic CsA nephrotoxicity. We used noninvasive molecular imaging (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging) and molecular diagnostic tools to assess intrarenal oxygenation and perfusion, and the molecular phenotype of CsA nephrotoxicity.

RESULTS

We observed that chemical and genetic inhibition of Nox2 in rats and mice resulted in the prevention of CsA-induced hypoxia independent of regional perfusion (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging, pimonidazole, HIF-1α). Nicotinamide adenosine diphosphate oxidase 2 knockout was also associated with decreased oxidative stress (Nox2, HIF-1α, hydrogen peroxide, hydroxynonenal), and fibrogenesis (α-smooth muscle actin, picrosirius red, trichrome, vimentin). The molecular signature of chronic CsA nephrotoxicity using transcriptomic analyses demonstrated significant changes in 40 genes involved in injury repair, metabolism, and oxidative stress in Nox2-/- mice. Immunohistochemical analyses of kidney biopsies from liver transplant recipients with chronic CsA nephrotoxicity showed significantly greater Nox2, α-smooth muscle actin and picrosirius levels compared with controls.

CONCLUSIONS

These studies suggest that Nox2 is a modulator of CsA-induced hypoxia upstream of HIF-1α and define the molecular characteristics that could be used for the diagnosis and monitoring of chronic calcineurin inhibitor nephrotoxicity.

Hyalinosis Lesions in Renal Transplant Biopsies: Time-Dependent Complexity of Interpretation

Because calcineurin inhibitor (CNI) immunosuppressive drugs induce arteriolar hyalinosis (ah) in kidney transplants, ah lesions can potentially provide information about drug exposure. We studied the relationship of ah lesions to findings and outcomes in 562 indication biopsies taken 3 days to 35 years after transplant. Prevalence of ah lesions increased with time of biopsy after transplant (TxBx). The ah scores correlated with arterial intimal thickening and atrophy-fibrosis but, unlike atrophy-fibrosis, did not increase until after 500 days because of a background of ah1 lesions in early biopsies reflecting donor aging. Correlation of ah scores with other features varied with TxBx-in early biopsies, donor age and related changes, and in very late biopsies, chronic antibody-mediated rejection and glomerulonephritis and associated lesions. After correction for TxBx, ah0 in intermediate time periods was associated with increased risk of T cell-mediated rejection and graft loss, probably because of underimmunosuppression and nonadherence. Thus, ah lesions in indication biopsies have multiple associations: donor age (early, usually ah1), chronic glomerular diseases (late, often ah2/3), and adequate exposure to CNIs at intermediate times. This threefold TxBx-dependent complexity must be considered when interpreting indication biopsies: ah lesions often indicate adequate CNI exposure, not toxicity, and unexpected ah0 should increase vigilance for nonadherence and underimmunosuppression.

Arteriosclerosis in zero-time biopsy is a risk factor for tacrolimus-induced chronic nephrotoxicity

AIM

Calcineurin inhibitors reduce the acute rejection rate and greatly improve renal allograft survival. However, they are associated with some adverse events, including nephrotoxicity, a risk factor for allograft failure. Chronic calcineurin inhibitor-induced nephrotoxicity causes irreversible damage to renal components, such as arteriolar hyaline thickening. The aim of this study is to investigate the risk factors for tacrolimus-induced chronic nephrotoxicity using zero-time biopsy specimens.

METHODS

Between January 2001 and December 2010, 483 patients who underwent living-related kidney transplantation and had also been placed on a tacrolimus-based regimen were enrolled in this study. There were 1859 specimens evaluated comprising 483 zero-time biopsy specimens and 1376 protocol and for-cause biopsy specimens. De novo arteriolar hyaline thickening due to tacrolimus-induced chronic nephrotoxicity was scored according to the Banff classification aah score. In this study, tacrolimus-induced nephrotoxicity was defined as a positive aah score.

RESULTS

Of the 483 patients, 108 patients (22.4%) had biopsy-proven tacrolimus-induced chronic nephrotoxicity. Multivariate analysis showed that interlobular arteriosclerosis proven by zero-time biopsy (OR: 2.23, 95%CI: 1.38-3.58, P < 0.01) and acute rejection episodes (OR: 1.58, 95%CI: 1.00-2.47, P = 0.04) were independent risk factors for tacrolimus-induced chronic nephrotoxicity. However, tacrolimus-induced chronic nephrotoxicity did not affect long-term graft survival.

CONCLUSION

This is the first report showing that arteriosclerosis in zero-time biopsy specimens is a risk factor for histological tacrolimus-induced chronic nephrotoxicity.

Impact of combination antiretroviral therapy in the NOD.c3c4 mouse model of autoimmune biliary disease

BACKGROUND & AIMS

The NOD.c3c4 mouse model develops autoimmune biliary disease characterized by spontaneous granulomatous cholangitis, antimitochondrial antibodies and liver failure. This model for primary biliary cirrhosis (PBC) has evidence of biliary infection with mouse mammary tumour virus (MMTV), suggesting that the virus may have a role in cholangitis development and progression of liver disease in this mouse model. We tested the hypothesis that MMTV infection is associated with cholangitis in the NOD.c3c4 mouse model by investigating whether antiretroviral therapy impacts on viral levels and liver disease.

METHODS

NOD.c3c4 mice were treated with combination antiretroviral therapy. Response to treatment was studied by measuring MMTV RNA in the liver, liver enzyme levels in serum and liver histology using a modified Ishak score.

RESULTS

Combination therapy with the reverse transcriptase inhibitors, tenofovir and emtricitabine, resulted in a significant reduction in serum liver enzyme levels, attenuation of cholangitis and decreased MMTV levels in the livers of NOD.c3c4 mice. Furthermore, treatment with the retroviral protease inhibitors, lopinavir and ritonavir, in addition to the reverse transcriptase inhibitors, resulted in further decrease in MMTV levels and attenuation of liver disease in this model.

CONCLUSIONS

The attenuation of cholangitis with regimens containing the reverse transcriptase inhibitors, tenofovir and emtricitabine, and the protease inhibitors, lopinavir and ritonavir, suggests that retroviral infection may play a role in the development of cholangitis in this model.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

Sirolimus conversion efficacy for graft function improvement and histopathology in renal recipients with mild to moderate renal insufficiency

This study was designed to evaluate whether sirolimus (SRL) conversion effectively improves renal function and histopathology in calcineurin inhibitor (CNI)-treated renal recipients with mild to moderate renal insufficiency. SRL conversion from CNI was performed in patients who underwent kidney transplantation from 6 months to 5 yr prior to screening. Forty-five patients were enrolled. The effect of SRL conversion on graft function was evaluated, and protocol biopsies were performed preconversion and 1 yr after conversion. Overall graft function after SRL conversion gradually improved, and the improvement in renal function was closely associated with the shorter duration of CNI exposure. When we divided the patients by the duration of CNI exposure, the patients with less than 1 yr of CNI exposure demonstrated significant improvement, but patients with a greater than 1 yr CNI exposure did not exhibit significant improvement. In contrast, protocol biopsies demonstrated no significant improvements in the modified "ah" score or other Banff scores after SRL conversion. Furthermore, the duration of CNI treatment prior to SRL conversion was not associated with histological findings 1 yr after SRL conversion. SRL conversion improved graft function in renal recipients with mild to moderate renal insufficiency, but this effect is not accompanied by histological improvement.

Calcineurin inhibitor sparing strategies in renal transplantation, part one: Late sparing strategies

Kidney transplantation improves quality of life and reduces the risk of mortality. A majority of the success of kidney transplantation is attributable to the calcineurin inhibitors (CNIs), cyclosporine and tacrolimus, and their ability to reduce acute rejection rates. However, long-term graft survival rates have not improved over time, and although controversial, evidence does suggest a role of chronic CNI toxicity in this failure to improve outcomes. Consequently, there is interest in reducing or removing CNIs from immunosuppressive regimens in an attempt to improve outcomes. Several strategies exist to spare calcineurin inhibitors, including use of agents such as mycophenolate mofetil (MMF), mycophenolate sodium (MPS), sirolimus, everolimus or belatacept to facilitate late calcineurin inhibitor withdrawal, beyond 6 mo post-transplant; or using these agents to plan early withdrawal within 6 mo; or to avoid the CNIs all together using CNI-free regimens. Although numerous reviews have been written on this topic, practice varies significantly between centers. This review organizes the data based on patient characteristics (i.e., the baseline immunosuppressive regimen) as a means to aid the practicing clinician in caring for their patients, by matching up their situation with the relevant literature. The current review, the first in a series of two, examines the potential of immunosuppressive agents to facilitate late CNI withdrawal beyond 6 mo post-transplant, and has demonstrated that the strongest evidence resides with MMF/MPS. MMF or MPS can be successfully introduced/maintained to facilitate late CNI withdrawal and improve renal function in the setting of graft deterioration, albeit with an increased risk of acute rejection and infection. Additional benefits may include improved blood pressure, lipid profile and serum glucose. Sirolimus has less data directly comparing CNI withdrawal to an active CNI-containing regimen, but modest improvement in short-term renal function is possible, with an increased risk of proteinuria, especially in the setting of baseline renal dysfunction and/or proteinuria. Renal outcomes may be improved when sirolimus is used in combination with MMF. Although data with everolimus is less robust, results appear similar to those observed with sirolimus.

The predictive value of kidney allograft baseline biopsies for long-term graft survival

The effect of baseline histology and individual histologic lesions at the time of transplantation on long-term graft survival has been evaluated using different scoring systems, but the predictive capacity of these systems has not been adequately validated. All kidney recipients transplanted in a single institution between 1991 and 2009 who underwent a baseline kidney allograft biopsy at transplantation were included in this prospective study (N=548). All baseline biopsies were rescored according to the updated Banff classification, and the relationship between the individual histologic lesions and donor demographics was assessed using hierarchical clustering and principal component analysis. Survival analysis was performed using Cox proportional hazards analysis and log-rank testing. Mean follow-up time was 6.7 years after transplantation. Interstitial fibrosis, tubular atrophy, and glomerulosclerosis associated significantly with death-censored graft survival, whereas arteriolar hyalinosis and vascular intimal thickening did not. Notably, donor age correlated significantly with interstitial fibrosis, tubular atrophy, and glomerulosclerosis and associated independently with graft survival. On the basis of these findings, a novel scoring system for prediction of 5-year graft survival was constructed by logistic regression analysis. Although the predictive performance of previously published histologic scoring systems was insufficient to guide kidney allocation in our cohort (receiver operating characteristic area under the curve ≤0.62 for each system), the new system based on histologic data and donor age was satisfactory for prediction of allograft loss (receiver operating characteristic area under the curve = 0.81) and may be valuable in the assessment of kidney quality before transplantation.

Partial therapeutic response to Rituximab for the treatment of chronic alloantibody mediated rejection of kidney allografts

BACKGROUND AND OBJECTIVES

Chronic rejection leads to kidney allograft failure and develops in many kidney transplant recipients. One cause of chronic rejection, chronic antibody mediated rejection (CAMR), is attributed to alloantibodies. Maintenance immunosuppression including prednisone, mycophenolate mofetil (MMF) and calcineurin inhibitors may limit alloantibody production in some patients, but many maintain or develop alloantibody production, leading to CAMR. Therefore, no efficacious therapy to treat CAMR is presently available to prevent the progression of CAMR to kidney allograft failure.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

We performed a retrospective review of 31 subjects with CAMR, of which 14 received Rituximab and 17 subjects did not. Response to Rituximab was defined as decline or stabilization of serum creatinine for at least one year. Data reviewed included demographic, clinical, allograft, post-transplant, and pathological variables. Pathological variables in the diagnostic allograft biopsy were scored according to Banff criteria.

RESULTS

The median survival time (MST) for allografts in the control group was 439 days, and for the Rituximab treated group was 685 days. The Rituximab group was dichotomous with 8 subjects showing a medial survival time of 1180 days, and 6 subjects having a median survival time of 431 days. The MST for the responders was statistically significant from the non-responders and controls. No pathological parameter distinguished any subset of subjects.

CONCLUSIONS

These data show that Rituximab followed by standard maintenance immunosuppression shows a therapeutic effect in the treatment of CAMR, which is confined to a subset of treated subjects, not identifiable a priori.

Nox2 is a mediator of chronic CsA nephrotoxicity

We hypothesized that Nox2, the classical phagocytic NADPH oxidase, plays an important role in calcineurin inhibitor (CNI)-induced renal fibrosis. We tested this hypothesis in vitro, in animal and in human studies. Cyclosporine A (CsA) and tacrolimus (TAC) were associated with greater levels of Nox2 mRNA and epithelial to mesenchymal transition (EMT) in NRK52E cells. CsA increased Nox2, α-SMA and phosphorylated-p38MAPK, Smad3 and NFκB proteins. Nox2 upregulation and EMT were inhibited in TGF-β1 knockout cells suggesting that TGF-β1 is required for Nox2 activation. Fisher344 rats treated with high dose CsA showed increased Nox2 in the tubulointerstitium and greater Nox2, α-SMA, phosphorylated Smad3 and nitrotyrosine by immunoblot analyses. Inhibition of Nox2 by coadministration of apocynin or diphenyleneiodonium was associated with reduced fibrogenesis. We validated these findings by treating wild type and Nox2 null (B6.129S-Cybb(Tm1Din)/J) mice with high dose CsA. Western blot analyses confirmed the absence of Nox2 and significantly lower levels of α-SMA and 4-hydroxynonenal (HNE) in CsA-treated knockout mice. These findings were clinically relevant since Nox2 and α-SMA were increased in the tubulointerstitium of kidneys from 15 liver transplant recipients with biopsy-confirmed chronic CsA or TAC nephrotoxicity. In conclusion, specific Nox2 inhibition strategies may improve chronic CNI nephrotoxicity in solid organ transplantation.

Clinical role of the renal transplant biopsy

Percutaneous needle core biopsy is the definitive procedure by which essential diagnostic and prognostic information on acute and chronic renal allograft dysfunction is obtained. The diagnostic value of the information so obtained has endured for over three decades and has proven crucially important in shaping strategies for therapeutic intervention. This Review provides a broad outline of the utility of performing kidney graft biopsies after transplantation, highlighting the relevance of biopsy findings in the immediate and early post-transplant period (from days to weeks after implantation), the first post-transplant year, and the late period (beyond the first year). We focus on how biopsy findings change over time, and the wide variety of pathological features that characterize the major clinical diagnoses facing the clinician. This article also includes a discussion of acute cellular and humoral rejection, the toxic effects of calcineurin inhibitors, and the widely varying etiologies and characteristics of chronic lesions. Emerging technologies based on gene expression analyses and proteomics, the in situ detection of functionally relevant molecules, and new bioinformatic approaches that hold the promise of improving diagnostic precision and developing new, refined molecular pathways for therapeutic intervention are also presented.

Specificity of histological markers of long-term CNI nephrotoxicity in kidney-transplant recipients under low-dose cyclosporine therapy

The specificity of chronic histological lesions induced by calcineurin inhibitors (CNI) is often questioned, but few studies have directly compared long-term lesions in renal-transplant patients who received this treatment and those who did not. We therefore conducted a retrospective study of 141 kidney-transplant recipients treated with (n = 48) or without (n = 93) cyclosporine (CsA) to compare the histological lesions observed at 3-month, 24-month and 10-year protocol biopsies. All of the chronic elementary lesions (glomerulosclerosis, interstitial fibrosis, tubular atrophy, arteriolar hyalinosis, fibrointimal thickening) progressed in frequency and severity in both groups, although significantly more in the CsA group. Ten-year biopsy results showed that 92% of patients in the CsA-treated group and 65% in the control group had arteriolar hyalinosis lesions. When we focused on muscular arteriolar hyaline deposits more specific to CsA arteriolopathy, we observed these lesions in 68% of CsA patients and 28% of patients who had never received CsA. CsA was not the sole factor involved in the development of arteriolar hyalinosis and was independently associated with an increased risk of graft loss. In summary, we observed that histological lesions commonly attributed to CsA nephrotoxicity were not sufficiently specific to definitively diagnose CNI nephrotoxicity.

Superiority of virtual microscopy versus light microscopy in transplantation pathology

Virtual microscopy has begun to change conventional pathology practice. We tested the reliability of this new technology in transplantation pathology. We studied 40 kidney transplant biopsies for cause and compared reproducibility of Banff scores using virtual slides versus glass slides. Three glass slides per biopsy were scanned as high-resolution digital slides using Aperio ScanScope. Three pathologists independently reviewed the biopsies: twice by glass slides and twice by virtual slides. Eleven histopathological lesions were scored and used to construct diagnosis according to Banff criteria. The intra-observer reproducibility of Banff scores was substantially good using either virtual slides or glass slides (mean κ: 0.69 vs. 0.64, p>0.05). The inter-observer reproducibility of Banff scores was better in virtual slides than in glass slides (mean κ: 0.42 vs. 0.28, p<0.001). Among the lesions, transplant glomerulopathy scoring by virtual slides showed the highest inter-observer reproducibility, with a similar accuracy to glass slides. The agreement for acute rejection between virtual and glass slides was not different from the agreement between two readings of glass slides. Thus, virtual microscopy is a reliable and more reproducible technology and has several advantages over glass slides, e.g., accessibility via internet, no fading. We recommend virtual microscopy for transplant diagnostics, including utilization for clinical trials.

The pharmacogenetics of calcineurin inhibitor-related nephrotoxicity

Chronic calcineurin inhibitor (CNI)-induced nephrotoxicity is associated with prolonged use of cyclosporine and tacrolimus and has been observed after all types of transplantation, as well as during treatment of autoimmune disease. Extensive alterations in the renal architecture including glomerular sclerosis, tubular atrophy and interstitial fibrosis may lead to end-stage renal failure. Increasing evidence shows that pharmacogenetic factors explain part of the between-patient differences in susceptibility to developing CNI-induced nephrotoxicity. In this paper this evidence is reviewed, with special emphasis on the role of genetic factors influencing metabolism and transportation of CNIs in both acceptor and donor.

Tacrolimus dose requirements and CYP3A5 genotype and the development of calcineurin inhibitor-associated nephrotoxicity in renal allograft recipients

OBJECTIVES

Prolonged calcineurin inhibitor maintenance therapy in kidney allograft recipients is complicated by the development of chronic irreversible drug-induced nephrotoxicity (CNIT).

METHODS

In 304 de novo renal graft recipients, the association among tacrolimus exposure indices (dose, C(0), AUC(0-12h)), CYP3A5, CYP3A4 and ABCB1 polymorphisms, clinical covariables and de novo arteriolar hyalinization as a histologic sign of CNIT was examined.

RESULTS

Tacrolimus C(0) and AUC(0-12h) at 3 and 12 months posttransplantation did not differ between patients with and without CNIT. Patients who developed CNIT more often carried the CYP3A5*1 allele (32.4% versus 15.2%, P = 0.01). Twenty-five percent of recipients with tacrolimus dose requirements exceeding 0.2 mg/kg per day at 3 months posttransplantation developed CNIT, whereas 16.2% of patients with dose requirements between 0.10 and 0.20 mg/kg per day and 4.5% of patients who needed less than 0.10 mg/kg per day developed CNIT (P < 0.0001). These early differences in tacrolimus dose requirements between recipients with and without CNIT persisted during subsequent follow-up. In a Cox proportional hazards analysis, the CYP3A5*1 allele (hazard ratio: 2.38; 95% confidence interval: 1.15-4.92) or tacrolimus dose range (hazard ratio: 2.06; 95% confidence interval: 1.30-3.27) and continued corticosteroid therapy (hazard ratio: 4.75; 95% confidence interval: 1.13-19.98) were independently associated with CNIT. A Kaplan-Meier survival curve demonstrated a significant difference in CNIT-free survival (93.5% versus 81.8% versus 66.9%; log-rank test: P = 0.0006) between patients with, respectively, tacrolimus dose requirements less than 0.1, 0.1 or greater, less than 0.2, and 0.2 mg/kg per day or greater. More patients with CNIT sustained graft loss during follow-up (32.3% versus13.7%, P = 0.004).

CONCLUSIONS

High early tacrolimus dose requirements, predominantly but not exclusively encountered in CYP3A5*1 expressers, are associated with the development of calcineurin inhibitor-related nephrotoxicity, especially in recipients who continue corticosteroid therapy.

Banff '09 meeting report: antibody mediated graft deterioration and implementation of Banff working groups

The 10th Banff Conference on Allograft Pathology was held in Banff, Canada from August 9 to 14, 2009. A total of 263 transplant clinicians, pathologists, surgeons, immunologists and researchers discussed several aspects of solid organ transplants with a special focus on antibody mediated graft injury. The willingness of the Banff process to adapt continuously in response to new research and improve potential weaknesses, led to the implementation of six working groups on the following areas: isolated v-lesion, fibrosis scoring, glomerular lesions, molecular pathology, polyomavirus nephropathy and quality assurance. Banff working groups will conduct multicenter trials to evaluate the clinical relevance, practical feasibility and reproducibility of potential changes to the Banff classification. There were also sessions on quality improvement in biopsy reading and utilization of virtual microscopy for maintaining competence in transplant biopsy interpretation. In addition, compelling molecular research data led to the discussion of incorporation of omics-technologies and discovery of new tissue markers with the goal of combining histopathology and molecular parameters within the Banff working classification in the near future.

[Nephrotoxicity of calcineurin inhibitors: presentation, diagnostic problems and risk factors]

Nephrotoxicity of calcineurin inhibitors (CNIs) is an acute, reversible and chronic, irreversible pathology. Histologically, acute nephrotoxicity manifests as hemodynamic modifications caused by vasoconstriction of the essentially afferent arterioles resulting in a drop in the glomerular filtration rate. Chronic nephrotoxicity is characterized by arteriolar hyalinosis resulting in a variety of tubulointerstitial and glomerular lesions with an essentially ischemic mechanism. However, these histological lesions, whether chronic or acute, are not specific of CNI toxicity and can be seen in the course of many pathological circumstances in kidney transplantation. This absence of specificity makes the histological diagnosis of CNI nephrotoxicity difficult. In addition, the individual risk of developing CNI nephrotoxicity, difficult to predict based solely on the pharmacokinetic parameters of systemic CNI exposure, also involves local exposure (CNI concentrations in the graft) modulated by several, notably pharmacogenetic factors. The difficulty of diagnosing CNI nephrotoxicity and the interindividual variability of its risk require development of new diagnostic tools so that the patients at highest risk of developing severe CNI nephrotoxicity lesions, in whom minimization protocols would produce the best risk-benefit ratio, can be identified.

Rosiglitazone prevents sirolimus-induced hypomagnesemia, hypokalemia, and downregulation of NKCC2 protein expression

Sirolimus, an antiproliferative immunosuppressant, induces hypomagnesemia and hypokalemia. Rosiglitazone activates renal sodium- and water-reabsorptive pathways. We evaluated whether sirolimus induces renal wasting of magnesium and potassium, attempting to identify the tubule segments in which this occurs. We tested the hypothesis that reduced expression of the cotransporter NKCC2 forms the molecular basis of this effect and evaluated the possible association between increased urinary excretion of magnesium and renal expression of the epithelial Mg2+ channel TRPM6. We then analyzed whether rosiglitazone attenuates these sirolimus-induced tubular effects. Wistar rats were treated for 14 days with sirolimus (3 mg/kg body wt in drinking water), with or without rosiglitazone (92 mg/kg body wt in food). Protein abundance of NKCC2, aquaporin-2 (AQP2), and TRPM6 was assessed using immunoblotting. Sirolimus-treated animals presented no change in glomerular filtration rate, although there were marked decreases in plasma potassium and magnesium. Sirolimus treatment reduced expression of NKCC2, and this was accompanied by greater urinary excretion of sodium, potassium, and magnesium. In sirolimus-treated animals, AQP2 expression was reduced. Expression of TRPM6 was increased, which might represent a direct stimulatory effect of sirolimus or a compensatory response. The finding that rosiglitazone prevented or attenuated all sirolimus-induced renal tubular defects has potential clinical implications.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Drug-induced Kidney Disease – Pathology and Current Concepts

The kidneys can be damaged by a large number of therapeutic agents. The aim of this article is to discuss the pathological features of drug-induced renal disease as diagnosed by kidney biopsy. The literature is reviewed and cases seen by the authors that have a known drug association are analysed. Mechanisms of injury are varied and all renal structures may be affected. The tubulointerstitial compartment is most frequently involved, but glomerular and vascular lesions are seen in a significant proportion of cases. Key words: Drug, Kidney, Nephrotoxicity, Pathology

[Screening biopsies in kidney transplantation: from subclinical acute rejection to chronic allograft lesions]

Kidney biopsies for screening purposes have the advantage of revealing the early appearance of lesions having a poor prognosis before kidney function is altered. Early screening of subclinical rejections allows preventive treatment of kidney transplantation in patients taking cyclosporine or azathioprine, thus improving their renal function and reducing the incidence of chronic histological lesions. However, this benefit has yet to be demonstrated in patients taking tacrolimus or mycophenolic acid. As for interstitial fibrosis lesions and tubular atrophy, biopsies can screen subclinical immunological lesions or those related to nephrotoxicity of anticalcineurins, which have a negative prognostic value in terms of graft survival. In addition, detection of these lesions could be a very useful criterion of efficacy in clinical studies. Moreover, they could help decide on modifying immunosuppressor treatment and evaluate the therapeutic strategies in patients at risk for humoral rejection. Finally, given the cost of biopsies and the inconvenience for the patient, the question of the timing and the number of screening biopsies is crucial. However, interventional studies evaluating notably immunosuppressor treatment modifications based on histological data are necessary to justify the daily use of screening biopsies.

Acute tubular injury in protocol biopsies of renal grafts: prevalence, associated factors and effect on long-term function

Acute tubular injury (ATI) is commonly observed in renal allografts, especially early after transplantation. This study analyzes prevalence and associated clinical conditions of ATI in serial protocol biopsies (pBx) and indication biopsies (iBx), and its impact on long-term graft function. 612 pBx from 204 patients taken at 6 weeks, 3 and 6 months, and 151 iBx performed within the first year of transplantation were evaluated. Prevalence of ATI in pBx was 40% (6 weeks), 34% (3 months) and 37% (6 months), and 46% in iBx. ATI was associated with delayed graft function and prolonged cold ischemia time in pBx, and with acute rejections in iBx. The GFR at 1 and 2 years after transplantation correlated inversely with the frequency of ATI in both pBx and iBx (p < 0.001). Prevalence of chronic changes at 6 months was not significantly related to ATI (patients without ATI: 36%, patients with multiple ATI findings: 54%). ATI is linked to inferior long-term graft function. While this suggests lack of recovery from ATI with permanent allograft damage, the underlying molecular mechanisms need yet to be uncovered. Prevention of the potential pathogenetic factors identified in this study might be the key point to attain good long-term graft function.

Banff 07 classification of renal allograft pathology: updates and future directions

The 9th Banff Conference on Allograft Pathology was held in La Coruna, Spain on June 23-29, 2007. A total of 235 pathologists, clinicians and scientists met to address unsolved issues in transplantation and adapt the Banff schema for renal allograft rejection in response to emerging data and technologies. The outcome of the consensus discussions on renal pathology is provided in this article. Major updates from the 2007 Banff Conference were: inclusion of peritubular capillaritis grading, C4d scoring, interpretation of C4d deposition without morphological evidence of active rejection, application of the Banff criteria to zero-time and protocol biopsies and introduction of a new scoring for total interstitial inflammation (ti-score). In addition, emerging research data led to the establishment of collaborative working groups addressing issues like isolated 'v' lesion and incorporation of omics-technologies, paving the way for future combination of graft biopsy and molecular parameters within the Banff process.

A comparison of the effects of fish oil and flaxseed oil on cardiac allograft chronic rejection in rats

Both fish and flaxseed oils are major sources of different n-3 fatty acids. Beneficial effects of fish oil on posttransplantation complications have been reported. The current study aimed to compare the effects of flaxseed and fish oils in a rat cardiac allograft model. Male Fischer and Lewis rats were used as donors and recipients, respectively, to generate a heterotopic cardiac allograft model. Animals were randomly assigned into three groups and fed a diet supplemented with 1) 5% (wt/wt) safflower oil (control, n = 7), 2) 5% (wt/wt) flaxseed oil ( n = 8), or 3) 2% (wt/wt) fish oil ( n = 7), and an intraperitoneal injection of cyclosporine A (CsA; 1.5 mg·kg−1·day−1) over 12 wk. Body weight, blood pressure, plasma levels of lipids, CsA, select cytokines, as well as graft function and chronic rejection features were assessed. Body weight and blood CsA levels were similar among the groups. Relative to controls, both treated groups had lower systolic and diastolic blood pressure and plasma levels of macrophage chemotactic protein-1. Treatment with fish oil significantly ( P < 0.05) lowered plasma levels of triglycerides, total cholesterol, and LDL-cholesterol. HDL-cholesterol concentrations were significantly higher ( P < 0.05) in the flaxseed oil-treated group compared with the other two groups. Both flaxseed oil and fish oil may provide similar biochemical, hemodynamic, and inflammatory benefits after heart transplantation; however, neither of the oils was able to statistically significantly impact chronic rejection or histological evidence of apparent cyclosporine-induced nephrotoxicity in this model.

Chronic kidney disease after nonrenal solid-organ transplantation

Chronic kidney disease (CKD) is a common complication after nonrenal solid-organ transplantation. The risk for CKD is influenced by many factors, some of which have a direct impact on how such patients are treated in the pre-, peri-, and posttransplantation settings. This review describes hazards for acute and chronic kidney injury, with particular emphasis on calcineurin inhibitor-mediated nephrotoxicity. Rather than a detailed description of management issues that are common to the general CKD population, highlighted are aspects that are more specific to nonrenal solid-organ transplant recipients with a focus on liver, heart, and lung recipients. Strategies to minimize nephrotoxic insults and retard progressive renal injury are discussed, as are issues that are pertinent to dialysis and transplantation. Finally, future approaches to prevent and treat CKD without compromising function of the transplanted organ are addressed.

Protocol biopsies in renal transplantation: insights into patient management and pathogenesis

A 1-day symposium on the application of protocol biopsies in renal transplantation was held in Boston, 21 July 2006. Representatives from centers with extensive experience in the use of protocol biopsies for routine patient care and research reported results on the pathological findings and their value in patient management. The consensus was that protocol biopsies, in experienced hands, are a safe and valuable means of detecting subclinical disease that can benefit from modification of therapy. Furthermore, molecular studies reveal evidence of activity or progression not readily appreciated by histological techniques. Wider application is expected in multicenter clinical trials to predict and validate outcomes. The principal barrier to wider use of protocol biopsies is knowledge of the benefits of intervention.