Identification of clinical and histopathologic risk factors for diminished renal function 2 years posttransplant

Effectiveness of T cell-mediated rejection therapy: A systematic review and meta-analysis

The effectiveness of T cell-mediated rejection (TCMR) therapy for achieving histological remission remains undefined in patients on modern immunosuppression. We systematically identified, critically appraised, and summarized the incidence and histological outcomes after TCMR treatment in patients on tacrolimus (Tac) and mycophenolic acid (MPA). English-language publications were searched in MEDLINE (Ovid), Embase (Ovid), Cochrane Central (Ovid), CINAHL (EBSCO), and Clinicaltrials.gov (NLM) up to January 2021. Study quality was assessed with the National Institutes of Health Study Quality Tool. We pooled results using an inverse variance, random-effects model and report the binomial proportions with associated 95% confidence intervals (95% CI). Statistical heterogeneity was explored using the I²  statistic. From 2875 screened citations, we included 12 studies (1255 participants). Fifty-eight percent were good/high quality while the rest were moderate quality. Thirty-nine percent of patients (95% CI 0.26-0.53, I² 77%) had persistent ≥Banff Borderline TCMR 2-9 months after anti-rejection therapy. Pulse steroids and augmented maintenance immunosuppression were mainstays of therapy, but considerable practice heterogeneity was present. A high proportion of biopsy-proven rejection exists after treatment emphasizing the importance of histology to characterize remission. Anti-rejection therapy is foundational to transplant management but well-designed clinical trials in patients on Tac/MPA immunosuppression are lacking to define the optimal therapeutic approach.

Improve in-depth immunological risk assessment to optimize genetic-compatibility and clinical outcomes in child and adolescent recipients of parental donor kidney transplants: protocol for the INCEPTION study

Background

Parental donor kidney transplantation is the most common treatment option for children and adolescents with kidney failure. Emerging data from observational studies have reported improved short- and medium-term allograft outcomes in recipients of paternal compared to maternal donors. The INCEPTION study aims to identify potential differences in immunological compatibility between maternal and paternal donor kidneys and ascertain how this affects kidney allograft outcomes in children and adolescents with kidney failure.

Methods

This longitudinal observational study will recruit kidney transplant recipients aged ≤18 years who have received a parental donor kidney transplant across 4 countries (Australia, New Zealand, United Kingdom and the Netherlands) between 1990 and 2020. High resolution human leukocyte antigen (HLA) typing of both recipients and corresponding parental donors will be undertaken, to provide an in-depth assessment of immunological compatibility. The primary outcome is a composite of de novo donor-specific anti-HLA antibody (DSA), biopsy-proven acute rejection or allograft loss up to 60-months post-transplantation. Secondary outcomes are de novo DSA, biopsy-proven acute rejection, acute or chronic antibody mediated rejection or Chronic Allograft Damage Index (CADI) score of > 1 on allograft biopsy post-transplant, allograft function, proteinuria and allograft loss. Using principal component analysis and Cox proportional hazards regression modelling, we will determine the associations between defined sets of immunological and clinical parameters that may identify risk stratification for the primary and secondary outcome measures among young people accepting a parental donor kidney for transplantation. This study design will allow us to specifically investigate the relative importance of accepting a maternal compared to paternal donor, for families deciding on the best option for donation.

Discussion

The INCEPTION study findings will explore potentially differential immunological risks of maternal and paternal donor kidneys for transplantation among children and adolescents. Our study will provide the evidence base underpinning the selection of parental donor in order to achieve the best projected long-term kidney transplant and overall health outcomes for children and adolescents, a recognized vulnerable population.

Trial registration

The INCEPTION study has been registered with the Australian New Zealand Clinical Trials Registry, with the trial registration number of ACTRN12620000911998 (14th September 2020).

The Utility of Donor-specific Antibody Monitoring and the Role of Kidney Biopsy in Simultaneous Liver and Kidney Recipients With De Novo Donor-specific Antibodies

BACKGROUND

There is limited information about the utility of donor-specific antibody (DSA) against HLA monitoring and the role of protocol kidney biopsy for de novo DSA (dnDSA) in simultaneous liver and kidney (SLK) transplant recipients.

METHODS

We analyzed SLK transplant recipients transplanted between January 2005 and December 2017, who had DSA checked posttransplant. Patients were divided into 2 groups based on whether they developed dnDSA posttransplant (dnDSA+) or not (dnDSA-). Kidney graft rejection ±45 d of dnDSA and a kidney death-censored graft survival were the primary endpoints.

RESULTS

A total of 83 SLK transplant recipients fulfilled our selection criteria. Of those, 23 were dnDSA+ and 60 were dnDSA-. Twenty-two of 23 dnDSA+ patients had DSA against class II HLA, predominantly against DQ. Fifteen recipients underwent kidney biopsy ±45 d of dnDSA. Six of these were clinically indicated due to kidney graft dysfunction. The other 9 had a protocol kidney biopsy only due to dnDSA, and 6 of these 9 had a rejection. Also, 3 recipients had sequential biopsies of both the kidney and liver grafts. Among those with sequential biopsies of both grafts, there was a difference between the organs in the rate and types of rejections. At last follow up, dnDSA was not associated with graft failure of either the kidney or liver.

CONCLUSIONS

Although our study was limited by a small sample size, it suggests the potential utility of DSA monitoring and protocol kidney biopsy for dnDSA.

Human kidney graft survival correlates with structural parameters in baseline biopsies: a quantitative observational cohort study with more than 14 years' follow-up

This prospective cohort study evaluates associations between structural and ultrastructural parameters in baseline biopsies from human kidney transplants and long-term graft survival after more than 14 years' follow-up. Baseline kidney graft biopsies were obtained prospectively from 54 consecutive patients receiving a kidney transplant at a single institution. Quantitative measurements were performed on the baseline biopsies by computer-assisted light microscopy and electron microscopy. Stereology-based techniques estimated the fraction of interstitial tissue, the volume of glomeruli, mesangial fraction, and basement membrane thickness of glomerular capillaries. The fraction of occluded glomeruli and scores according to the Banff classification were achieved. Kidney graft survival was analyzed by Kaplan-Meier estimates and Cox regression. Association to long-term kidney function was also analyzed. The long-term surviving kidney transplants were characterized at implantation by less arteriolar hyaline thickening (P < 0.001) and less interstitial fibrosis (P = 0.001), as well as a lower fraction of occluded glomeruli (P = 0.004) and lower glomerular volume (P = 0.03). At the latest follow-up, eGFR was decreased by 12 ml/min/1.73 m² per unit increase in the score for arteriolar hyalinosis at implantation (P = 0.02), and eGFR was decreased by 19 ml/min/1.73 m² per 10⁶ μm³ increase in glomerular volume at baseline (P = 0.03). The unbiased Cavalieri estimate of glomerular volume and the ultrastructural parameters are the first to be evaluated in a cohort study with prospective follow-up for more than 14 years. The study shows that baseline biopsies from human kidney grafts contain extraordinary long-term prognostic information, and it highlights the importance of these intrinsic graft factors.

Activity-based protein profiling guided identification of urine proteinase 3 activity in subclinical rejection after renal transplantation

Background

The pathophysiology of subclinical versus clinical rejection remains incompletely understood given their equivalent histological severity but discordant graft function. The goal was to evaluate serine hydrolase enzyme activities to explore if there were any underlying differences in activities during subclinical versus clinical rejection.

Methods

Serine hydrolase activity-based protein profiling (ABPP) was performed on the urines of a case control cohort of patients with biopsy confirmed subclinical or clinical transplant rejection. In-gel analysis and affinity purification with mass spectrometry were used to demonstrate and identify active serine hydrolase activity. An assay for proteinase 3 (PR3/PRTN3) was adapted for the quantitation of activity in urine.

Results

In-gel ABPP profiles suggested increased intensity and diversity of serine hydrolase activities in urine from patients undergoing subclinical versus clinical rejection. Serine hydrolases (n = 30) were identified by mass spectrometry in subclinical and clinical rejection patients with 4 non-overlapping candidates between the two groups (i.e. ABHD14B, LTF, PR3/PRTN3 and PRSS12). Western blot and the use of a specific inhibitor confirmed the presence of active PR3/PRTN3 in samples from patients undergoing subclinical rejection. Analysis of samples from normal donors or from several serial post-transplant urines indicated that although PR3/PRTN3 activity may be highly associated with low-grade subclinical inflammation, the enzyme activity was not restricted to this patient group.

Conclusions

There appear to be limited qualitative and quantitative differences in serine hydrolase activity in patients with subclinical versus clinical renal transplant rejection. The majority of enzymes identified were present in samples from both groups implying that in-gel quantitative differences may largely relate to the activity status of shared enzymes. However qualitative compositional differences were also observed indicating differential activities. The PR3/PRTN3 analyses indicate that the activity status of urine in transplant patients is dynamic possibly reflecting changes in the underlying processes in the transplant. These data suggest that differential serine hydrolase pathways may be active in subclinical versus clinical rejection which requires further exploration in larger patient cohorts. Although this study focused on PR3/PRTN3, this does not preclude the possibility that other enzymes may play critical roles in the rejection process.

Prediction of kidney transplant outcome based on different DGF definitions in Chinese deceased donation

Background

Delayed graft function (DGF) is an important complication of kidney transplantation and can be diagnosed according to different definitions. DGF has been suggested to be associated with the long-term outcome of kidney transplantation surgery. However, the best DGF definition for predicting renal transplant outcomes in Chinese donations after cardiac death (DCDs) remains to be determined.

Method

A total of 372 DCD kidney transplant recipients from June 2013 to July 2017 in the First Affiliated Hospital of Xi’an Jiaotong University were included in this retrospective study to compare 6 different DGF definitions. The relationships of the DGF definitions with transplant outcome were analyzed, including graft loss (GL) and death-censored graft loss (death-censored GL). Renal function indicators, including one-year estimated glomerular filtration rate (eGFR) and three-year eGFR, and were compared between different DGF groups.

Results

The incidence of DGF varied from 4.19 to 35.22% according to the different DGF diagnoses. All DGF definitions were significantly associated with three-year GL as well as death-censored GL. DGF based on requirement of hemodialysis within the first week had the best predictive value for GL (AUC 0.77), and DGF based on sCr variation during the first 3 days post-transplant had the best predictive value for three-year death-censored GL (AUC 0.79). Combination of the 48-h sCr reduction ratio and classical DGF can improve the AUC for GL (AUC 0.85) as well as the predictive accuracy for death-censored GL (83.3%).

Conclusion

DGF was an independent risk factor for poor transplant outcome. The combination of need for hemodialysis within the first week and the 48-h serum creatinine reduction rate has a better predictive value for patient and poor graft outcome.

Multicentre randomised controlled trial protocol of urine CXCL10 monitoring strategy in kidney transplant recipients

INTRODUCTION

Subclinical inflammation is an important predictor of death-censored graft loss, and its treatment has been shown to improve graft outcomes. Urine CXCL10 outperforms standard post-transplant surveillance in observational studies, by detecting subclinical rejection and early clinical rejection before graft functional decline in kidney transplant recipients.

METHODS AND ANALYSIS

This is a phase ii/iii multicentre, international randomised controlled parallel group trial to determine if the early treatment of rejection, as detected by urine CXCL10, will improve kidney allograft outcomes. Incident adult kidney transplant patients (n~420) will be enrolled to undergo routine urine CXCL10 monitoring postkidney transplant. Patients at high risk of rejection, defined as confirmed elevated urine CXCL10 level, will be randomised 1:1 stratified by centre (n=250). The intervention arm (n=125) will undergo a study biopsy to check for subclinical rejection and biopsy-proven rejection will be treated per protocol. The control arm (n=125) will undergo routine post-transplant monitoring. The primary outcome at 12 months is a composite of death-censored graft loss, clinical biopsy-proven acute rejection, de novo donor-specific antibody, inflammation in areas of interstitial fibrosis and tubular atrophy (Banff i-IFTA, chronic active T-cell mediated rejection) and subclinical tubulitis on 12-month surveillance biopsy. The secondary outcomes include decline of graft function, microvascular inflammation at 12 months, development of IFTA at 12 months, days from transplantation to clinical biopsy-proven rejection, albuminuria, EuroQol five-dimension five-level instrument, cost-effectiveness analysis of the urine CXCL10 monitoring strategy and the urine CXCL10 kinetics in response to rejection therapy.

ETHICS AND DISSEMINATION

The study has been approved by the University of Manitoba Health Research Ethics Board (HS20861, B2017:076) and the local research ethics boards of participating centres. Recruitment commenced in March 2018 and results are expected to be published in 2023. De-identified data may be shared with other researchers according to international guidelines (International Committee of Medical Journal Editors [ICJME]).

TRIAL REGISTRATION NUMBER

NCT03206801; Pre-results.

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.

Renin-Angiotensin System Blockage and Avoiding High Doses of Calcineurin Inhibitors Prevent Interstitial Fibrosis and Tubular Atrophy in Kidney Transplant Recipients

OBJECTIVES

Chronic allograft dysfunction is a complex and multifactorial process characterized by progressive interstitial fibrosis and tubular atrophy. The finding of interstitial fibrosis and tubular atrophy is prevalent among kidney transplant patients receiving a calcineurin inhibitor-based immunosuppressive regimen and may be considered as a surrogate of allograft survival. Both immune (acute rejection episodes, sensitization, and HLA incompatibility) and nonimmune (donor age, delayed graft function, calcineurin inhibitor toxicity, infections, and hypertension) mechanisms play a role in chronic allograft dysfunction, and different causes all lead to similar histologic and clinical final pathways, with the end result of graft loss. In our study, we aimed to compare the outcomes of kidney transplant recipients with or without interstitial fibrosis and tubular atrophy in protocol biopsies to determine the conditions that may affect allograft survival.

MATERIALS AND METHODS

We divided 192 kidney transplant recipients into 2 groups (96 patients with interstitial fibrosis and tubular atrophy; 96 patients without interstitial fibrosis and tubular atrophy) according to protocol biopsy at 6 months. Patient groups were compared according to their risk factors for chronic allograft dysfunction (cold ischemia time, delayed graft function, donor age, infections, mean blood calcineurin levels, and hypertension).

RESULTS

Cold ischemia time, delayed graft function, high 24-hour proteinuria levels, and higher mean blood calcineurin levels were found to be major risk factors for poor graft function in kidney transplant recipients with interstitial fibrosis and tubular atrophy. Renin-angiotensin system blockage with either angiotensin-converting enzyme inhibitors or angiotensin receptor blockers was found to be preventive for interstitial fibrosis and tubular atrophy after kidney transplant.

CONCLUSIONS

Preventing prolongation of cold ischemia time, lowering blood cholesterol levels, angiotensin-converting enzyme inhibitors and angiotensin receptor blocker treatment even without existing proteinuria and avoiding higher doses of calcineurin inhibitors should be major approaches in kidney transplant recipients.

A new method of modelling early plasma creatinine changes predicts 1-year graft function after kidney transplantation

BACKGROUND

Delayed graft function after renal transplantation is associated with inferior long-term outcome. To evaluate the impact of slow onset graft function, we aimed to model and correlate early changes in plasma creatinine (p-cr) with long-term graft function.

MATERIALS

In a single centre observational study of 100 kidney transplants we identified all p-cr measurements from the time of transplantation until 30 days post-transplant or last post-transplant dialysis, and correlated this with estimated glomerular filtration rate (eGFR) 1 year after transplantation. The initial changes in p-cr were modelled for each patient using an exponential, logistic, or linear model, and the time to a 50% decrease in p-cr (tCr50) was estimated.

RESULTS

Linear regression analysis showed a negative correlation between tCr50 and eGFR 1 year post-transplant (n = 96, r = -0.369, β = -0.112, p = 0.0002). The correlation was maintained when corrected for the relevant recipient and donor characteristics. tCr50 correlated positively with the number of hospitalisation days, the number of graft ultrasound examinations, and the number of biopsies.

CONCLUSIONS

A modelled time to a 50% decrease in p-cr predicts 1-year graft function. tCr50 may be a relevant surrogate endpoint in renal transplant studies aimed at improving long-term function by reducing the incidence of slow onset graft function.

Advances in pharmacotherapy to treat kidney transplant rejection

INTRODUCTION

Current immunosuppressive combination therapy provides excellent prevention of T-cell-mediated rejection following renal transplantation; however, antibody-mediated rejection remains of high concern and accounts for a large number of long-term allograft losses. The recent development of protocol biopsies resulted in the definition of subclinical rejection (SCR), showing histologic evidence for rejection but unremarkable clinical course.

AREAS COVERED

This review describes the current knowledge and evidence of pharmacotherapy to treat kidney allograft rejections and covers SCR treatment options. Each substance is analyzed with regard to its classical indication and further discussed for the treatment of other forms of rejection.

EXPERT OPINION

Despite a lack of randomized trials, early acute T-cell-mediated rejection can be treated effectively in most cases without graft loss. The necessity to treat SCR is currently unclear. Due to a lack of effective therapies, new treatment approaches for antibody-mediated rejection are an urgent medical need to improve long-term outcomes. Future research should aim to better define pathophysiology and histology, stratify risk, and develop rational treatment strategies from randomized controlled trials, in order to establish the value of novel therapies in the arsenal of rejection pharmacotherapy. However, the effective prevention of rejection with minimal side effects still remains the goal in immunosuppression.

Developing renal allograft surveillance strategies - urinary biomarkers of cellular rejection

Purpose of review

Developing tailored immunosuppression regimens requires sensitive, non-invasive tools for serial post-transplant surveillance as the current clinical standards with serum creatinine and proteinuria are ineffective at detecting subclinical rejection. The purpose of this review is: (i) to illustrate the rationale for allograft immune monitoring, (ii) to discuss key steps to bring a biomarker from bench-to-bedside, and (iii) to present an overview of promising biomarkers for cellular rejection.

Sources of information

PubMed.

Findings

Recent multicentre prospective observational cohort studies have significantly advanced biomarker development by allowing for the adequately powered evaluation of multiple biomarkers capable of detecting allograft rejection. These studies demonstrate that urinary CXCR3 chemokines (i.e. CXCL9 and CXCL10) are amongst the most promising for detecting subclinical inflammation; increasing up to 30 days prior to biopsy-proven acute rejection; decreasing in response to anti-rejection therapy; and having prognostic significance for the subsequent development of allograft dysfunction. Urinary CXCR3 chemokines are measured by simple and cost-effective ELISA methodology, which can readily be implemented in clinical labs.

Limitations

Many biomarker studies are performed in highly selected patient groups and lack surveillance biopsies to accurately classify healthy transplants. Few validation studies have been done in unselected, consecutive patient populations to characterize population-based diagnostic performance.

Implications

Based on these data, prospective interventional trials should be undertaken to determine if chemokine-based post-transplant monitoring strategies can improve long-term renal allograft outcomes. This last step will be necessary to move novel biomarkers from the bench-to-bedside.

Elevated urinary CXCL10-to-creatinine ratio is associated with subclinical and clinical rejection in pediatric renal transplantation

BACKGROUND

Subclinical and clinical T cell-mediated rejection (TCMR) has significant prognostic implications in pediatric renal transplantation. The goal of this study was to independently validate urinary CXCL10 as a noninvasive biomarker for detecting acute rejection in children and to extend these findings to subclinical rejection.

METHODS

Urines (n = 140) from 51 patients with surveillance or indication biopsies were assayed for urinary CXCL10 using enzyme-linked immunosorbent assay and corrected with urinary creatinine.

RESULTS

Median urinary CXCL10-to-creatinine (Cr) ratio (ng/mmol) was significantly elevated in subclinical TCMR (4.4 [2.6, 25.4], P < 0.001, n = 17); clinical TCMR (24.3 [11.2, 44.8], P < 0.001, n = 9); and antibody-mediated rejection (6.0 [3.3, 13.7], P = 0.002, n = 9) compared to noninflamed histology (1.4 [0.4, 4.2], normal and interstitial fibrosis and tubular atrophy, n = 52), and borderline tubulitis (3.3, [1.3, 4.9], n = 36). Elevated urinary CXCL10:Cr was independently associated with t scores (P < 0.001) and g scores (P = 0.006) on multivariate analysis. The area under receiver operating curve for subclinical and clinical TCMR was 0.81 (P = 0.045) and 0.88 (P = 0.019), respectively. This corresponded to a sensitivity-specificity of 0.59-0.67 and 0.77-0.60 for subclinical and clinical TCMR at cutoffs of 4.82 and 4.72 ng/mmol, respectively.

CONCLUSION

This study demonstrates that urinary CXCL10:Cr corresponds with microvascular inflammation and is a sensitive and specific biomarker for subclinical and clinical TCMR in children. This may provide a noninvasive monitoring tool for posttransplant immune surveillance for pediatric renal transplant recipients.

Limited efficacy of immunosuppressive drugs on CD8+ T cell-mediated and natural killer cell-mediated lysis of human renal tubular epithelial cells

BACKGROUND

Although CD8+ T cell-mediated and natural killer (NK) cell-mediated cytotoxicity against renal tubular epithelial cells (TECs) plays a crucial role during rejection, the degree of inhibition of these lytic immune responses by immunosuppressive drugs is unknown. We investigated the CD8 T-cell and NK cell responses induced by TECs in vitro and questioned how these processes are affected by immunosuppressive drugs.

METHODS

Donor-derived TECs were co-cultured with recipient peripheral blood monocyte cells. Proliferation of CD8+ T cells and NK cell subsets was assessed using PKH dilution assay. CD107a degranulation and europium release assay were performed to explore CD8+-mediated and NK cell-mediated TEC lysis. Experiments were conducted in the absence or presence of tacrolimus (10 ng/mL), everolimus (10 ng/mL), and prednisolone (200 ng/mL).

RESULTS

Tubular epithelial cells induce significant CD8+ T-cell and NK cell proliferation. All immunosuppressive drugs significantly inhibited TEC-induced CD8+ T-cell proliferation. Interestingly, prednisolone was the most powerful inhibitor of NK cell proliferation. CD8-mediated and NK cell-mediated early lytic responses were marked by strong degranulation after an encounter of unstimulated TECs, represented by a high cell surface expression of CD107a. However, with the use of interferon-γ-activated and tumor necrosis factor-α-activated TECs, the NK degranulation response was significantly reduced and CD8 degranulation response was even more enhanced (P<0.05). Tubular epithelial cell-induced CD8 degranulation and CD8-mediated TEC lysis were preferentially inhibited by tacrolimus and prednisolone, and not by everolimus. Although tacrolimus showed the most inhibitory effect on the degranulation of NK cells, NK cell-mediated TEC lysis was efficiently inhibited by prednisolone (P<0.05).

CONCLUSION

Overall, our data point to a limited efficacy of immunosuppressive drugs on CD8+ T cell-mediated and NK cell-mediated lysis of human renal TECs.

Inhibition of hyaluronan is protective against renal ischaemia-reperfusion injury

BACKGROUND

Ischaemia-reperfusion injury (IRI) to the kidney is a complex pathophysiological process that leads to acute renal failure and chronic dysfunction in renal allografts. It was previously demonstrated that during IRI, hyaluronan (HA) accumulates in the cortical and external medullary interstitium along with an increased expression of its main receptor, CD44, on inflammatory and tubular cells. The HA-CD44 pair may be involved in persistent post-ischaemic inflammation. Thus, we sought to determine the role of HA in the pathophysiology of ischaemia-reperfusion (IR) by preventing its accumulation in post-ischaemic kidney.

METHODS

C57BL/6 mice received a diet containing 4-methylumbelliferone (4-MU), a potent HA synthesis inhibitor. At the end of the treatment, unilateral renal IR was induced and mice were euthanized 48 h or 30 days post-IR.

RESULTS

4-MU treatment for 14 weeks reduced the plasma HA level and intra-renal HA content at 48 h post-IR, as well as CD44 expression, creatininemia and histopathological lesions. Moreover, inflammation was significantly attenuated and proliferation was reduced in animals treated with 4-MU. In addition, 4-MU-treated mice had a significantly reduced expression of α-SMA and collagen types I and III, i.e. less renal fibrosis, 30 days after IR compared with untreated mice.

CONCLUSION

Our results demonstrate that HA plays a significant role in the pathogenesis of IRI, perhaps in part through reduced expression of CD44. The suppression of HA accumulation during IR may protect renal function against ischaemic insults.

Urine free light chains as a novel biomarker of acute kidney allograft injury

BACKGROUND

We evaluated urine free light chains (FLC) as a potential biomarker for acute kidney allograft injury (AKAI).

METHODS

Urine κ and λ FLC were compared with urine β-2 microglobulin (β2-M), retinol-binding protein (RBP), kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and microalbuminuria (MAB) in biopsy-confirmed acute rejection (AR) and acute tubular necrosis (ATN). Healthy volunteers (normal) and transplant recipients with normal allograft function (control) were used as references.

RESULTS

Compared with control or normal group (N = 15), urine FLC, MAB, and RBP were higher in ATN (N = 29) and AR (N = 41) groups (p < 0.05). There was no difference in KIM-1, NGAL, or β2-M between four groups. In the AR group, urine κFLC demonstrated the highest predictive value with sensitivity of 95.12% and specificity of 87.5% (p < 0.0001). Urine κFLC also performed best with a sensitivity of 96.55% and specificity of 93.33% (p < 0.0001) in the ATN group. The area under the receiver operating characteristic (ROC) curves (AUC) by ROC analysis is greatest in urine RBP (100%) and FLC (99%), and lowest in KIM-1 (53.5%), then NGAL (71.5%) in the AR group. The AUC is also greatest in urine FLC (100%) and RBP (99%), and lowest in urine KIM-1 (55.6%) and NGAL (69.9%) in the ATN group.

CONCLUSIONS

Urine FLC appears sensitive for both AR and ATN, and it may be a novel AKAI biomarker.

Angiotensin II blockade in kidney transplant recipients

Interstitial fibrosis/tubular atrophy (IF/TA) contributes to the loss of kidney allografts, and treatment or preventive options are lacking. We conducted a double-blind, randomized, placebo-controlled trial to determine whether angiotensin II blockade prevents the expansion of the cortical interstitial compartment, the precursor of fibrosis. We randomly assigned 153 transplant recipients to receive losartan, 100 mg (n=77), or matching placebo (n=76) within 3 months of transplantation, continuing treatment for 5 years. The primary outcome was a composite of doubling of the fraction of renal cortical volume occupied by interstitium from baseline to 5 years or ESRD from IF/TA. In the intention-to-treat analysis, using only patients with adequate structural data, the primary endpoint occurred in 6 of 47 patients who received losartan and 12 of 44 who received placebo (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.13-1.15; P=0.08). We found no significant effect of losartan on time to a composite of ESRD, death, or doubling of creatinine level. In a secondary analysis, losartan seemed to reduce the risk of a composite of doubling of interstitial volume or all-cause ESRD (OR, 0.36; 95% CI, 0.13-0.99; P=0.05), but this finding requires validation. In conclusion, treatment with losartan did not lead to a statistically significant reduction in a composite of interstitial expansion or ESRD from IF/TA in kidney transplant recipients.

Rationale and design of the RIACT-study: a multi-center placebo controlled double blind study to test the efficacy of RItuximab in Acute Cellular tubulointerstitial rejection with B-cell infiltrates in renal Transplant patients: study protocol for a randomized controlled trial

BACKGROUND

Acute kidney allograft rejection is a major cause for declining graft function and has a negative impact on the long-term graft survival. The majority (90%) of acute rejections are T-cell mediated and, therefore, the anti-rejection therapy targets T-cell-mediated mechanisms of the rejection process. However, there is increasing evidence that intragraft B-cells are also important in the T-cell-mediated rejections. First, a significant proportion of patients with acute T-cell-mediated rejection have B-cells present in the infiltrates. Second, the outcome of these patients is inferior, which has been related to an inferior response to the conventional anti-rejection therapy. Third, treatment of these patients with an anti-CD20 antibody (rituximab) improves the allograft outcome as reported in single case observations and in one small study. Despite the promise of these observations, solid evidence is required before incorporating this treatment option into a general treatment recommendation.

METHODS/DESIGN

The RIACT study is designed as a randomized, double-blind, placebo-controlled, parallel group multicenter Phase III study. The study examines whether rituximab, in addition to the standard treatment with steroid-boli, leads to an improved one-year kidney allograft function, compared to the standard treatment alone in patients with acute T-cell mediated tubulointerstitial rejection and significant B-cell infiltrates in their biopsies. A total of 180 patients will be recruited.

DISCUSSION

It is important to clarify the relevance of anti-B cell targeting in T-cell mediated rejection and answer the question whether this novel concept should be incorporated in the conventional anti-rejection therapy.

TRIAL REGISTRATION

Clinical trials gov. number: NCT01117662.

Surveillance biopsies in children post-kidney transplant

Surveillance biopsies are increasingly used in the post-transplant monitoring of pediatric renal allograft recipients. The main justification for this procedure is to diagnose early and presumably modifiable acute and chronic renal allograft injury. Pediatric recipients are theoretically at increased risk for subclinical renal allograft injury due to their relatively large adult-sized kidneys and their higher degree of immunological responsiveness. The safety profile of this procedure has been well investigated. Patient morbidity is low, with macroscopic hematuria being the most common adverse event. No patient deaths have been attributed to this procedure. Longitudinal surveillance biopsy studies have revealed a substantial burden of subclinical immunological and non-immunological injury, including acute cellular rejection, interstitial fibrosis and tubular atrophy, microvascular lesions and transplant glomerulopathy. The main impediment to the implementation of surveillance biopsies as the standard of care is the lack of demonstrable benefit of early histological detection on long-term outcome. The considerable debate surrounding this issue highlights the need for multicenter, prospective, and randomized studies.

Treatment of subclinical injuries detected by protocol biopsy improves the long-term kidney allograft function: a single center prospective randomized clinical trial

BACKGROUND

The long-term benefit of early treatment of subclinical disorders detected in kidney allografts by protocol biopsy is controversial. We collected 145 protocol biopsies from 113 recipients for comparison with 51 control patients in a single-center, prospective, randomized trial.

METHODS

Ultrasound-guided biopsies were performed in recipients with stable renal function. Samples were taken at 3 (n=66) and/or 12 months (n=79) after transplantation. The biopsies were evaluated according to the Banff scheme, and patients were treated based on the diagnosis. Changes in glomerular filtration rate (GFR) were compared with 51 patients who were randomized as a control group.

RESULTS

The findings on 38 samples (29%) were considered to be normal. Based on the pathology findings, such as subclinical acute rejection (n=23), calcineurin inhibitor toxicity (n=28), chronic rejection (n=6), and other specific pathologies (n=23), including polyoma virus nephropathy (n=2), induced treatment among 82 recipients (57%). Significantly better graft function was observed at 3-year follow-up among the biopsy group, compared with controls: GFR = 46.0 ± 13.8 vs 35 ± 15 mL/min (P=.002). The 5-year graft survival was significantly higher in the biopsy (81%) than in the control (55.6%) group (P=.0012).

CONCLUSION

Early detection and treatment of subclinical pathologies improved graft function and long-term survival. Protocol biopsies were a valuable tool for posttransplantation management.

Interstitial fibrosis evolution on early sequential screening renal allograft biopsies using quantitative image analysis

Screening renal biopsies (RB) may assess early changes of interstitial fibrosis (IF) after transplantation. The aim of this study was to quantify IF by automatic color image analysis on sequential RB. We analyzed RB performed at day (D) 0, month (M) 3 and M12 from 140 renal transplant recipients with a program of color segmentation imaging. The mean IF score was 19 ± 9% at D0, 27 ± 11% at M3 and 32 ± 11% at M12 with a 8% progression during the first 3 months and 5% between M3 and M12. IF at M3 was correlated with estimated glomerular rate (eGFR) at M3, 12 and 24 (p < 0.02) and IF at M12 with eGFR at M12 and 48 (p < 0.05). Furthermore, IF evolution between D0 and M3 (ΔIFM3-D0) was correlated with eGFR at M24, 36 and 48 (p < 0.03). IF at M12 was significantly associated with male donor gender and tacrolimus dose (p = 0.03). ΔIFM3-D0 was significantly associated with male donor gender, acute rejection episodes (p = 0.04) and diabetes mellitus (p = 0.02). Thus, significant IF is already present before transplantation. IF evolution is more important during the first 3 months and has some predictive ability for change in GFR. Intervention to decrease IF should be applied early, i.e. before 3 months, after transplantation.

Intragraft tubular vimentin and CD44 expression correlate with long-term renal allograft function and interstitial fibrosis and tubular atrophy

BACKGROUND

Development of interstitial fibrosis and tubular atrophy (IF/TA) is the main histologic feature involved in renal allograft deterioration. The aim of this study was to validate whether de novo tubular expression of CD44 (transmembrane glycoprotein) and vimentin (mesenchymal cell marker), both involved in renal fibrosis, can operate as surrogate markers for late IF/TA and renal function. Furthermore, we wanted to establish the interrater reproducibility for the scoring system, which can be a problem in histologic assessments.

METHODS

Six-month protocol renal allograft biopsies (n=30 for matching 12 months estimated glomerular filtration rate (eGFR) from which 20 matched the 12-month protocol biopsy) were immunostained for CD44 and vimentin, semiquantitatively scored by three observers of two centers, and correlated with IF/TA and eGFR at 12 months.

RESULTS

The interobserver agreement was excellent for CD44 (Kendall's W-coefficient: 0.69; P<0.001) and vimentin (Kendall's W-coefficient: 0.79; P<0.001). CD44 and vimentin expression at 6 months were significantly correlated with IF/TA (rho=0.481 for CD44 and rho=0.619 for vimentin) and eGFR (rho=-0.569 for CD44 and rho=-0.376 for vimentin) at 12 months.

CONCLUSIONS

Summarizing, de novo tubular expression of CD44 and vimentin can function as surrogate marker for IF/TA and eGFR at 12 months. Further area under receiver operator characteristic curve analysis has to establish the predictive value for both biomarkers.

Periodontitis case definition affects the association with renal function in kidney transplant recipients

AIM

The aim of this analysis was to investigate the association between periodontal status and renal allograft function in a cohort of renal transplant patients using different periodontitis case definitions.

MATERIAL AND METHODS

Fifty-eight kidney transplant patients were included. The subjects were classified into two groups, deterioration or stable/improvement of renal allograft function as expressed by the difference in glomerular filtration rate (GFR) between two time points at least 6 months apart. Chronic periodontitis was defined as: (1) two or more interproximal sites with clinical attachment level (CAL) ≥4 mm or two or more interproximal sites with probing depth (PD) ≥5 mm (DEF1); (2) PD ≥ 5 or CAL ≥ 4 in at least six proximal sites (DEF2); and (3) PD ≥ 5 or CAL ≥ 4 in at least two proximal sites in each quadrant (DEF3).

RESULTS

In a multivariate linear regression model, none of the continuous periodontal variables were significantly associated with deterioration of allograft function. Of the three definitions of chronic periodontitis, only DEF2 emerged as significantly more prevalent in subjects with GFR deterioration and was a statistically significant predictor of GFR deterioration over time.

CONCLUSION

These findings underscore the importance of periodontitis ‘case definition’ in the observed statistical associations between periodontitis and systemic disease.

Early urinary CCL2 is associated with the later development of interstitial fibrosis and tubular atrophy in renal allografts

BACKGROUND

Chronic renal allograft injury resulting in progressive interstitial fibrosis and tubular atrophy (IFTA) is a leading cause of graft loss. The goal of this study was to identify early urinary predictors for the subsequent development of IFTA in a prospective cohort of patients (n=111) who underwent serial protocol biopsies at 0, 6, and 24 months.

METHODS

The urinary proteins evaluated were CCL2, CXCL9, CXCL10, and alpha1-microglobulin (alpha1M) using ELISA and immunonephelometry.

RESULTS

We first evaluated urines obtained at 1 to 3 months and found that alpha1M and CXCL10 were associated with IFTA at 6 months but not at 24 months. Next, we evaluated urines at 6 months and found that CCL2 was associated with both IFTA and graft dysfunction at 24 months. On univariate analysis, 6-month urinary CCL2 was a risk factor for developing 24-month IFTA, defined as ci+ct score more than 0 (odds ratio 1.045, 95% confidence interval: 1.005-1.084, P=0.028). Furthermore, CCL2 remained an independent predictor of IFTA on multivariate analysis (odds ratio 1.049, 95% confidence interval: 1.006-1.094, P=0.024) when adjusted for donor age, delayed graft function, deceased donation, and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker exposure. In comparison, alpha1M, CXCL9, and CXCL10 were not associated with late graft outcomes.

CONCLUSION

This study demonstrates that early urinary CCL2 is an independent predictor for the subsequent development of IFTA at 24 months.

Intragraft expression of the IL-10 gene is up-regulated in renal protocol biopsies with early interstitial fibrosis, tubular atrophy, and subclinical rejection

Grafts with subclinical rejection associated with interstitial fibrosis and tubular atrophy (SCR+IF/TA) show poorer survival than grafts with subclinical rejection without IF/TA (SCR). Aiming to detect differences among SCR+IF/TA and SCR, we immunophenotyped the inflammatory infiltrate (CD45, CD3, CD20, CD68) and used a low-density array to determine levels of T(H)1 (interleukin IL-2, IL-3, gamma-interferon, tumor necrosis factor-alpha, lymphotoxin-alpha, lymphotoxin-beta, granulocyte-macrophage colony-stimulating factor) and T(H)2 (IL-4, IL-5, IL-6, IL-10, and IL-13) transcripts as well as of IL-2R (as marker for T-cell activation) in 31 protocol biopsies of renal allografts. Here we show that grafts with early IF/TA and SCR can be distinguished from grafts with SCR on the basis of the activation of IL-10 gene expression and of an increased infiltration by B-lymphocytes in a cellular context in which the degree of T-cell activation is similar in both groups of biopsies, as demonstrated by equivalent levels of IL-2R mRNA. These results suggest that the up-regulation of the IL-10 gene expression, as well as an increased proportion of B-lymphocytes in the inflammatory infiltrates, might be useful as markers of early chronic lesions in grafts with SCR.

Post-transplant monitoring of renal allografts: are we there yet?

Transplantation has emerged as the therapy of choice for many patients with end organ failure. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient to balance the risk for rejection and over-immunosuppression. This will require diagnostic tools that can detect harmful processes in the allograft early, and that can be measured repeatedly. This review will consider recent advances in our understanding of the molecular nature of these processes and how this information is being utilized to design novel diagnostic assays to non-invasively monitor allografts. Highlighted is the need for large-scale prospective multi-centre studies to validate assays that show early promise in single centre studies.

The pathogenesis and treatment of chronic allograft nephropathy

Despite improvements in immunosuppressive therapy, long-term allograft survival after kidney transplantation remains as low as 50%. Chronic allograft nephropathy (CAN) is a major cause of late graft loss in renal transplant recipients. The histopathologic signs of CAN-interstitial fibrosis, tubular atrophy, glomerulopathy and vasculopathy-are nonspecific; therefore, the 2007 Banff classification dispensed with the term CAN in favor of 'interstitial fibrosis and tubular atrophy without evidence of any specific etiology'. In this Review, however, the term CAN is used to describe a clinical syndrome that is characterized by progressive decline in renal function from 3 months after transplantation, accompanied by the development of proteinuria and hypertension. The pathogenesis of CAN is complex and incompletely understood, and involves several immunological and non-immunological factors. We discuss the contributory roles of acute rejection, donor age, anti-human-leukocyte-antigen antibodies, calcineurin inhibitor nephrotoxic effects, viral infection, hypertension and hyperlipidemia. The prevention and treatment of CAN needs multidisciplinary strategies. Early detection by means of protocol biopsy and calculation of glomerular filtration rate is the first step, followed by management of modifiable risk factors.

Minimizing the risk of chronic allograft nephropathy

Chronic allograft nephropathy, now defined as interstital fibrosis and tubular atrophy not otherwise specified, is a near universal finding in transplant kidney biopsies by the end of the first decade posttransplantation. After excluding death with functioning graft, caused by cardiovascular disease or malignancy, chronic allograft nephropathy is the leading cause of graft failure. Original assumptions were that this was not a modifiable process but inexorable, likely due to past kidney injuries. However, newer understandings suggest that acute or subacute processes are involved, and with proper diagnosis, appropriate interventions can be instituted. Our method involved a review of the primary and secondary prevention trials in calcineurin inhibitor withdrawal. Some of the more important causes of progressive graft deterioration include subclinical cellular or humoral rejection, and chronic calcineurin inhibitor toxicity. Early graft biopsy, assessment of histology, and changes in immunosuppression may be some of the most important measures available to protect graft function. The avoidance of clinical inertia in pursuing subtle changes in graft function is critical. Modification in maintenance immunosuppression may benefit many patients with early evidence of graft deterioration.

Association between delayed graft function and allograft and patient survival: a systematic review and meta-analysis

BACKGROUND

Delayed graft function (DGF) is a common complication of renal transplantation. The short-term consequences of DGF are well known, but the long-term relationship between DGF and patient and graft survival is controversial in the published literature. We conducted a systematic review and meta-analysis to precisely estimate these relationships.

METHODS

We performed a literature search for original studies published through March 2007 pertaining to long-term (>6 months) outcomes of DGF. The primary outcome was graft survival. Secondary outcomes were patient survival, acute rejection and kidney function.

RESULTS

When compared to patients without DGF, patients with DGF had a 41% increased risk of graft loss (RR 1.41, 95% CI 1.27-1.56) at 3.2 years of follow-up. There was no significant relationship between DGF and patient survival at 5 years (RR 1.14, 95% CI 0.94-1.39). The mean creatinine in the non-DGF group was 1.6 mg/dl. Patients with DGF had a higher mean serum creatinine (0.66 mg/dl, 95% CI 0.57-0.74) compared to patients without DGF at 3.5 years of follow-up. DGF was associated with a 38% relative increase in the risk of acute rejection (RR 1.38, 95% CI 1.29-1.47).

CONCLUSION

The results of this meta-analysis emphasize and quantify the long-term detrimental association between DGF and important graft outcomes like graft survival, acute rejection and renal function. Efforts to prevent and treat DGF should be aggressively investigated in order to improve graft survival given the deficit in the number of kidney donors.

Chronic allograft nephropathy: what have we learned from protocol biopsies?

Chronic allograft nephropathy, characterized by interstitial fibrosis and tubular atrophy, is still a major cause of graft loss after kidney transplantation. The complex pathophysiology of chronic allograft nephropathy is still poorly understood, and could be clarified by a more systematic performance of implantation and protocol biopsies of the renal allograft. This review highlights the contribution of implantation and protocol biopsies to our current knowledge of the complex interaction of multiple processes, ultimately leading to the development of interstitial fibrosis and tubular atrophy in the transplanted kidney. In addition, the safety and the limitations of protocol biopsies are discussed, as well as potential future directions for clinical practice and clinical research.

Chronic allograft nephropathy

PURPOSE OF REVIEW

Despite dramatic declines in acute rejection and early graft failure, long-term outcomes after kidney transplantation have improved little during the past 25 years. Most late allograft failure is attributed to chronic allograft nephropathy, but this is a clinicopathological description and not a diagnosis, and its pathogenesis and treatment are largely unknown.

RECENT FINDINGS

Recent studies suggest that acute rejection during the first few months, and calcineurin inhibitor toxicity thereafter, may both contribute to chronic allograft nephropathy. There is also accumulating evidence that injury from antibody-mediated rejection may play an important pathogenic role in at least some patients with chronic allograft nephropathy, particularly those with transplant glomerulopathy. Therapeutic measures, including protocols to reduce calcineurin inhibitor exposure, remain largely unproven.

SUMMARY

Understanding why so many kidney allografts fail, despite effective preventive measures for early acute rejection, is one of the most important areas of research in kidney transplantation today.

Marked variation in the definition and diagnosis of delayed graft function: a systematic review

BACKGROUND

The term delayed graft function (DGF) is commonly used to describe the need for dialysis after receiving a kidney transplant. DGF increases morbidity after transplantation, prolongs hospitalization and may lead to premature graft failure. Various definitions of DGF are used in the literature without a uniformly accepted technique to identify DGF.

METHODS

We performed a systematic review of the literature to identify all of the different definitions and diagnostic techniques to identify DGF.

RESULTS

We identified 18 unique definitions for DGF and 10 diagnostic techniques to identify DGF.

CONCLUSIONS

The utilization of heterogeneous clinical criteria to define DGF has certain limitations. It will lead to delayed and sometimes inaccurate diagnosis of DGF. Hence a diagnostic test that identifies DGF reliably and early is necessary. Heterogeneity, in the definitions used for DGF, hinders the evolution of a diagnostic technique to identify DGF, which requires a gold standard definition. We are in need of a new definition that is uniformly accepted across the kidney transplant community. The new definition will be helpful in promoting better communication among transplant professionals and aids in comparing clinical studies of diagnostic techniques to identify DGF and thus may facilitate clinical trials of interventions for the treatment of DGF.

Quantification of interstitial fibrosis by image analysis on routine renal biopsy in patients receiving cyclosporine

BACKGROUND

Renal interstitial fibrosis (IF) is the main histopathological feature of chronic allograft injury. IF is currently assessed by semiquantitative analysis, but automatic color image analysis may be more reliable and reproducible. We performed a retrospective analysis to calculate IF on routine renal biopsies performed at 1 year posttransplant.

METHODS

Data were obtained from MO2ART, a prospective multicenter trial in which cyclosporine A dose was adjusted based on C2 level. One-year routine biopsies were assessed from 26 patients from two centers. For each biopsy, a section was analyzed by a program of color segmentation imaging, which automatically extracts green color areas characteristic of IF. Results were expressed as percentage of IF and grade (grade 1: <25%, grade 2: 25-50%, and grade 3: >50%).

RESULTS

Mean IF score was 0.35+/-0.04. Quantitative IF grade 1 was observed in 9 biopsies (34.6%), grade 2 in 12 (46.1%), and grade 3 in 5 (19.2%). Diabetes and cytomegalovirus infection were significantly associated with a higher percentage of IF. There was no correlation between the group of randomization and IF. We found a statistical significant correlation between Banff 05 chronic lesions classification and the IF index (P<0.02). Repeated analysis of variance demonstrated an association between high grade of automated IF and a worsening of creatinine clearance (Modification of Diet in Renal Disease) between 1 and 3 years.

CONCLUSIONS

Automatic quantification of IF on routine renal biopsies at one year posttransplant is predictive of long-term allograft function and may assist early diagnosis of the interstitial lesions of chronic allograft injury.

Analysis of renal transplant protocol biopsies in ABO-incompatible kidney transplantation

Numerous studies have shown that protocol biopsies have predictive power. We retrospectively examined the histologic findings and C4d staining in 89 protocol biopsies from 48 ABO-incompatible (ABO-I) transplant recipients, and compared the results with those of 250 controls from 133 ABO-compatible (ABO-C) transplant recipients given equivalent maintenance immunosuppression. Others have shown that subclinical rejection (borderline and grade I) in ABO-C grafts decreased gradually after transplantation. In our study, however, subclinical rejection in the ABO-I grafts was detected in 10%, 14% and 28% at 1, 3 and 6-12 months, respectively. At 6-12 months, mild tubular atrophy was more common in the ABO-C grafts whereas the incidence of transplant glomerulopathy did not differ between the two groups (ABO-C: 7%; ABO-I: 15%; p = 0.57). In the ABO-I transplants, risk factors for transplant glomerulopathy in univariate analysis were positive panel reactivity (relative risk, 45.0; p < 0.01) and a prior history of antibody-mediated rejection (relative risk, 17.9; p = 0.01). Furthermore, C4d deposition in the peritubular capillaries was detected in 94%, with diffuse staining in 66%. This deposition, however, was not linked to antibody-mediated rejection. We conclude that, in the ABO-I kidney transplantation setting, detection of C4d alone in protocol biopsies might not have any diagnostic or therapeutic relevance.

Lack of benefit of early protocol biopsies in renal transplant patients receiving TAC and MMF: a randomized study

We conducted a randomized, multicenter study to determine whether treatment of subclinical rejection with increased corticosteroids resulted in beneficial outcomes in renal transplant patients receiving tacrolimus (TAC), mycophenolate mofetil (MMF) and prednisone. One hundred and twenty-one patients were randomized to biopsies at 0,1,2,3 and 6 months (Biopsy arm), and 119 to biopsies at 0 and 6 months only (Control arm). The primary endpoint of the study was the prevalence of the sum of the interstitial and tubular scores (ci + ct)> 2 (Banff) at 6 months. Secondary endpoints included clinical and subclinical rejection and renal function. At 6 months, 34.8% of the Biopsy and 20.5% of the Control arm patients had a ci + ct score >or= 2 (p = 0.07). Between months 0 and 6, clinical rejection episodes were 12 in 10 Biopsy arm patients and 8 in 8 Control arm patients (p = 0.44). Overall prevalence of subclinical rejection in the Biopsy arm was 4.6%. Creatinine clearance at 6 months was 72.9 +/- 21.7 in the Biopsy and 68.90 mL/min +/- 18.35 mL/min in the Control arm patients (p = 0.18). In conclusion, we found no benefit to the procurement of early protocol biopsies in renal transplant patients receiving TAC, MMF and prednisone, at least in the short term. This is likely due to their low prevalence of subclinical rejection.

Evaluating the accuracy of functional biomarkers for detecting histological changes in chronic allograft nephropathy

The most common cause of late kidney transplant failure is chronic allograft nephropathy (CAN). Much research has focused on identifying biomarkers (or correlates) that would predict subsequent CAN and allow timely intervention. Functional biomarkers such as serum creatinine and estimated glomerular filtration rate (eGFR) have been widely adopted, even though they have not been rigorously evaluated as surrogate markers. This study evaluated serum creatinine and eGFR for predicting the early histopathological changes seen in transplant protocol biopsies (TPB). We prospectively followed 289 kidney transplant patients in the Southern Alberta Transplant Program who had TPB at 6-12 months post-transplant. Tissue samples (n = 280) were independently examined by renal pathologists. The ability of serum creatinine or eGFR to predict the threshold level for abnormal histopathology was evaluated by calculating the area under the receiver operator characteristic curve. Serum creatinine and eGFR had poor predictive value (most confidence intervals included 0.5, indicating no predictive ability) for ten individual histological measurements (Banff 97 scores), and the Chronic Allograft Damage Index. We conclude that serum creatinine and eGFR have a limited clinical role in predicting the early histopathological changes that precede CAN and should not be used for this purpose.

Clinical predictors of renal allograft histopathology: a comparative study of single-lesion histology versus a composite, quantitative scoring system

BACKGROUND

Progressive injury that is refractory to conventional immunosuppression remains the major hurdle to indefinite survival of transplanted organs. Several clinical risk factors of chronic renal allograft rejection have been identified; although some (e.g., acute rejection) are direct manifestations of immunological injury, others (e.g., donor age) have been more difficult to conceptually link with graft dysfunction.

METHODS

We conducted formal multivariate statistical analyses to reveal associations between established clinical risk factors and allograft histopathology. In a multicenter protocol biopsy-controlled study, 17 clinical risk factors were studied in relation to either the composite Chronic Allograft Damage Index (CADI) score or, to each of eight individual histological indices, using multiple linear regression with forward selection.

RESULTS

Nine clinical risk factors were not significantly associated with any histopathological index. Four (donor age, acute rejection, recipient age, and cold ischemia time) were associated both with the total CADI score and, to varying extents, with the individual histopathological indices. In our analysis, clinical risk factors accounted for, at best, only about 60% of the interindividual variation in histopathological score.

CONCLUSIONS

Our study reveals a missing link between specific clinical risk factors and early histopathological findings that are known to presage accelerated failure of clinically healthy grafts. Given the complex relationship between clinical risk factors, early histopathological changes, and graft outcome, we conclude that composite, quantitative histological indices are best suited to for evaluation of the histological status of the transplant.

Low incidence of adverse events in outpatient pediatric renal allograft biopsies

In 1999, our center implemented a policy of outpatient protocol biopsies as standard practice for the clinical management of pediatric renal allograft recipients. In order to determine the safety of this procedure, we conducted a retrospective chart audit of all outpatient renal allograft biopsies performed at our center. Biopsies were performed under conscious (midazolam) or procedural (propofol/fentanyl) sedation. Localization of the lower pole of the renal allograft was achieved with renal ultrasound. Using a Biopty gun with a 16-gauge needle, two cores were obtained. Patients were discharged four h post-biopsy. Patient demographics, hospital length of stay (LOS), specimen adequacy (per Banff criteria) and major and minor adverse events were recorded in a central database. Data were expressed as mean +/- SD. From June 1999 to July 2004, we performed 162 biopsies in 43 pediatric renal allograft recipients. Most patients underwent extraperitoneal transplantation (42/43, 97.7%) and were greater than five yr of age at biopsy (129/131 biopsies, 98.5%). The majority of these procedures (131/162, 80.9%) were conducted in the outpatient department, with 113 of 131 (86.3%) being obtained for protocol (n = 89) and one-month follow-up acute rejection therapy (n = 24) indications. Patients underwent 3.7 +/- 2.7 biopsies (range = 1-11). Specimen adequacy was achieved in 119 of 124 (96.0%) of documented cases. The overall incidence of adverse events was 12 of 131 (9.2%) biopsies, all of which were minor in severity. Macroscopic hematuria was the most common minor adverse event, occurring after 11 of 131 (8.4%) biopsies. While macroscopic hematuria prolonged LOS (adverse events vs. no adverse events: 23.0 +/- 26.0 vs. 8.6 +/- 4.1 h, p = 0), none of these episodes required major surgical or radiographic interventions. We conclude that in patients greater than five yr of age with extraperitoneal renal allografts, outpatient protocol biopsies using a 16-gauge needle are sufficiently safe to justify their inclusion in the routine clinical management of pediatric renal allograft recipients and in pediatric clinical trials.

Comparison of Low Versus High Tacrolimus Levels in Kidney Transplantation: Assessment of Efficacy by Protocol Biopsies

BACKGROUND

The use of calcineurin inhibitors is generally guided by drug blood levels. However, those levels are chosen based on clinical experience, lacking adequate titration studies.

METHODS

In these analyses, we compared clinical and histologic endpoints in two groups of kidney transplant recipients: in the first (HiTAC, January 2000 to June 2002, n=245) tacrolimus levels were significantly higher than in the second (LoTAC, July 2002 to September 2004, n=330). This change in drug levels (15% reduction) was made in an attempt to reduce the incidence of polyoma virus nephropathy (PVAN). Other immunosuppressive medications were unchanged during these two time periods.

RESULTS

The recipient and donor demographics were not statistically different between the two groups. Compared to HiTAC, at one year posttransplant LoTAC had: 1) lower incidence of PVAN (10.5% vs. 2.5%, P<0.0001); 2) lower fasting glucose levels; 3) higher iothalamate glomerular filtration rate (52+/-19 vs. 59+/-17 ml/min/m, P<0.0001); and 4) on protocol one-year biopsies, lower incidence and severity of interstitial fibrosis (67% vs. 45%, P=0.003) and tubular atrophy (82% vs., 66%, P=0.01). The incidence and severity of acute rejection episodes was similar between both groups (7.8% versus 7.6%).

CONCLUSIONS

Modest reductions in tacrolimus exposure early posttransplant are associated with significant beneficial effects for the patient and the allograft without an increased immunologic risk.

Untreated rejection in 6-month protocol biopsies is not associated with fibrosis in serial biopsies or with loss of graft function

Donor age, calcineurin inhibitor nephrotoxicity, and acute rejection are the most significant predictors of chronic allograft nephropathy. Protocol biopsies, both in deceased- and living-donor renal grafts, have shown that cortical tubulointerstitial fibrosis correlates with graft survival and function. The impact of not treating subclinical acute rejection (SAR) is less clear. In this study, 126 de novo renal transplant recipients were randomly assigned to receive area-under-the-curve-controlled exposure of either a cyclosporine or a tacrolimus-based immunosuppressive regimen that included steroids, mycophenolate mofetil, and basiliximab induction. Protocol biopsies were taken before and 6 and 12 mo after transplantation. The prevalence of SAR was determined retrospectively. Fibrosis was evaluated by quantitative digital analysis of Sirius red staining in serial biopsies. Donor age correlated significantly with tubulointerstitial fibrosis in pretransplantation biopsies and inferior graft function at month 6 (rtau = -0.26; P = 0.033). Acute rejection incidence was 11.5%, and no clinical late rejection occurred. The prevalence of SAR at 6 mo was 30.8% but was not associated with differences in serial quantitative Sirius red staining at 6 or 12 mo, proteinuria, or progressive loss of GFR up to 2 yr. No differences were found in donor variables, histocompatibility, rejection history, or exposure of immunosuppressants. Controlled individualized calcineurin inhibitor exposure and subsequent tapering resulted in a low early acute rejection rate and prevented late acute rejection. Because, by design, we did not treat SAR, these results provide evidence that asymptomatic infiltrates in 6-mo surveillance biopsies may not be deleterious in the intermediate term. There is need for reliable biomarkers to prove that not all cell infiltrates are equivalent or that infiltrates may change with time.