Natural History, Risk Factors, and Impact of Subclinical Rejection in Kidney Transplantation

Novel non-invasive biomarkers diagnostic of acute rejection in renal transplant recipients: A systematic review

BACKGROUND AND OBJECTIVES

Acute rejection is a significant complication detrimental to kidney transplant function. Current accepted means of diagnosis is percutaneous renal biopsy, a costly and invasive procedure. There is an urgent need to detect and validate non-invasive biomarkers capable of replacing the biopsy.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Comprehensive literature searches of Medline, EMBASE and Cochrane Central Register of Controlled Trials databases were performed. Eligible studies were included as per inclusion criteria and assessed for quality using the GRADE quality of evidence tool. Outcomes evaluated included biomarker diagnostic performance, number of patients/samples, mean age and gender ratio, immunosuppression regime, in addition to clinical applications of the biomarker(s) tested. PRISMA guidelines were followed. Where possible, statistical analysis of comparative performance data was performed.

RESULTS

23 studies were included in this review, including 19 adult, 3 paediatric and 1 mixed studies. A total of 2858 participants and 50 candidate non-invasive tests were identified. Sensitivity, specificity and area under the curve performance values ranged 36%-100%, 30%-100% and 0.55-0.98, respectively.

CONCLUSIONS

Although larger, more robust multi-centre validation studies are needed before non-invasive biomarkers can replace the biopsy, numerous candidate tests have demonstrated significant promise for various facets of postoperative management. Suggested uses include: ruling out patients with a low risk of acute rejection to avoid the need for biopsy, non-invasive testing where the biopsy is contraindicated and a prompt diagnosis is needed, and integration into a serial blood monitoring protocol in conjunction with serum creatinine.

Short-term adverse effects of early subclinical allograft inflammation in kidney transplant recipients with a rapid steroid withdrawal protocol

The impact of subclinical inflammation (SCI) noted on early kidney allograft biopsies remains unclear. This study evaluated the outcome of SCI noted on 3-month biopsy. A total of 273/363 (75%) kidney transplant recipients with a functioning kidney underwent allograft biopsies 3-months posttransplant. Among those with stable allograft function at 3 months, 200 biopsies that did not meet the Banff criteria for acute rejection were identified. These were Group I: No Inflammation (NI, n = 71) and Group II: Subclinical Inflammation (SCI, n = 129). We evaluated differences in kidney function at 24-months and allograft histology score at 12-month biopsy. SCI patients had a higher serum creatinine (1.6 ± 0.7 vs 1.38 ± 0.45; P = .02) at 24-months posttransplant, and at last follow-up at a mean of 42.5 months (1.69 ± 0.9 vs 1.46 ± 0.5 mg/dL; P = .027). The allograft chronicity score (ci + ct + cg + cv) at 12-months posttransplant was higher in the SCI group (2.4 ± 1.35 vs 1.9 ± 1.2; P = .02). The incidence of subsequent rejections within the first year in SCI and NI groups was 24% vs 10%, respectively (P = .015). De novo donor-specific antibody within 12 months was more prevalent in the SCI group (12/129 vs 1/71, P = .03). SCI is likely not a benign finding and may have long-term implications for kidney allograft function.

Polyclonal Regulatory T Cell Therapy for Control of Inflammation in Kidney Transplants

Early subclinical inflammation in kidney transplants is associated with later graft fibrosis and dysfunction. Regulatory T cells (Tregs) can reverse established inflammation in animal models. We conducted a pilot safety and feasibility trial of autologous Treg cell therapy in three kidney transplant recipients with subclinical inflammation noted on 6-month surveillance biopsies. Tregs were purified from peripheral blood and polyclonally expanded ex vivo using medium containing deuterated glucose to label the cells. All patients received a single infusion of ~320 × 10⁶ (319, 321, and 363.8 × 10⁶ ) expanded Tregs. Persistence of the infused Tregs was tracked. Graft inflammation was monitored with follow-up biopsies and urinary biomarkers. Nearly 1 × 10⁹ (0.932, 0.956, 1.565 × 10⁹ ) Tregs were successfully manufactured for each patient. There were no infusion reactions or serious therapy-related adverse events. The infused cells demonstrated patterns of persistence and stability similar to those observed in non-immunosuppressed subjects receiving the same dose of Tregs. Isolation and expansion of Tregs is feasible in kidney transplant patients on immunosuppression. Infusion of these cells was safe and well tolerated. Future trials will test the efficacy of polyclonal and donor alloantigen-reactive Tregs for the treatment of inflammation in kidney transplants.

Orthogonal Comparison of Molecular Signatures of Kidney Transplants With Subclinical and Clinical Acute Rejection: Equivalent Performance Is Agnostic to Both Technology and Platform

We performed orthogonal technology comparisons of concurrent peripheral blood and biopsy tissue samples from 69 kidney transplant recipients who underwent comprehensive algorithm-driven clinical phenotyping. The sample cohort included patients with normal protocol biopsies and stable transplant (sTx) function (n = 25), subclinical acute rejection (subAR, n = 23), and clinical acute rejection (cAR, n = 21). Comparisons between microarray and RNA sequencing (RNA-seq) signatures were performed and demonstrated a strong correlation between the blood and tissue compartments for both technology platforms. A number of shared differentially expressed genes and pathways between subAR and cAR in both platforms strongly suggest that these two clinical phenotypes form a continuum of alloimmune activation. SubAR is associated with fewer or less expressed genes than cAR in blood, whereas in biopsy tissues, this clinical phenotype demonstrates a more robust molecular signature for both platforms. The discovery work done in this study confirms a clear ability to detect gene expression profiles for sTx, subAR, and cAR in both blood and biopsy tissue, yielding equivalent predictive performance that is agnostic to both technology and platform. Our data also provide strong biological insights into the molecular mechanisms underlying these signatures, underscoring their logistical potential as molecular diagnostics to improve clinical outcomes following kidney transplantation.

Renal association clinical practice guideline in post-operative care in the kidney transplant recipient

These guidelines cover the care of patients from the period following kidney transplantation until the transplant is no longer working or the patient dies. During the early phase prevention of acute rejection and infection are the priority. After around 3-6 months, the priorities change to preservation of transplant function and avoiding the long-term complications of immunosuppressive medication (the medication used to suppress the immune system to prevent rejection). The topics discussed include organization of outpatient follow up, immunosuppressive medication, treatment of acute and chronic rejection, and prevention of complications. The potential complications discussed include heart disease, infection, cancer, bone disease and blood disorders. There is also a section on contraception and reproductive issues.Immediately after the introduction there is a statement of all the recommendations. These recommendations are written in a language that we think should be understandable by many patients, relatives, carers and other interested people. Consequently we have not reworded or restated them in this lay summary. They are graded 1 or 2 depending on the strength of the recommendation by the authors, and AD depending on the quality of the evidence that the recommendation is based on.

The Use of Genomics and Pathway Analysis in Our Understanding and Prediction of Clinical Renal Transplant Injury

The development and application of high-throughput molecular profiling have transformed the study of human diseases. The problem of handling large, complex data sets has been facilitated by advances in complex computational analysis. In this review, the recent literature regarding the application of transcriptional genomic information to renal transplantation, with specific reference to acute rejection, acute kidney injury in allografts, chronic allograft injury, and tolerance is discussed, as is the current published data regarding other "omics" strategies-proteomics, metabolomics, and the microRNA transcriptome. These data have shed new light on our understanding of the pathogenesis of specific disease conditions after renal transplantation, but their utility as a biomarker of disease has been hampered by study design and sample size. This review aims to highlight the opportunities and obstacles that exist with genomics and other related technologies to better understand and predict renal allograft outcome.

Subclinical Rejection in Renal Transplantation: Reappraised

Short-term outcomes in renal transplantation have improved significantly in the past few years. However, the improvement in long-term outcomes has been modest. The reasons for graft failure beyond the first year of transplantation have been attributed to several different factors. We believe that subclinical rejection (SCR) may be 1 of the factors that contribute to graft loss in the long run. We also believe that there are data to suggest that SCR leads to progressive fibrosis and loss of graft function. This has been demonstrated even in patients who have mild degrees of subclinical inflammation. This review outlines the major studies that have been published on this important topic. It also outlines potential risk factors for the development of SCR. The current approach and diagnostic methods are discussed as well as their pros and cons. Newer noninvasive methods of diagnosis as well as molecular diagnostics and their merits and shortcomings are also discussed in some depth. Thus, the proposed state of the art review on SCR will create a renewed interest at all levels including transplant clinicians, transplant researchers, pharmaceutical industries as well as regulatory organizations.

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.

Kidney allograft surveillance biopsy practices across US transplant centers: A UNOS survey

BACKGROUND

The approach to the diagnosis and management of subclinical rejection (SCR) in kidney transplant recipients remains controversial.

METHODS

We conducted a survey through UNOS across US transplant centers regarding their approach to surveillance biopsies and reasons for the nonperformance of surveillance biopsies.

RESULTS

Responses were obtained from 106/238 centers (45%), and only 18 (17%) of the centers performed surveillance biopsies on all patients and 22 (21%) performed biopsy for select cases. The most common time points for surveillance biopsies were 3 and 12  months post-transplant. The common reasons for not performing biopsies were low yield (n = 44, 65%) and the belief that it will not change outcome (n = 24, 36%). The incidence of SC-TCMR was ≥ 10% among 39% of centers. The mean serum creatinine was slightly worse by 0.06 mg/dL at 1 year and 0.07 mg/dL at 3 years among centers performing biopsy, P < .0001. The. 1-and 3-year Observed-Expected (O-E) graft survival was similar among centers performing biopsies vs. those not performing biopsy (P = .07, .88).

CONCLUSION

Only 17% of US centers perform surveillance biopsies, with another 21% performing surveillance biopsies in select cases (among centers that responded to the survey). Greater uniformity in the approach and management of this condition is of paramount importance.

Single center experience of subclinical rejections and BK nephropathies by kidney allografts' surveillance biopsies

PURPOSE

Acute rejection of the kidney allograft remains the most important factor affecting the long-term graft outcome and is a major predictor of development of chronic damage and graft loss. Several studies have shown that early detection and treatment of subclinical rejection episodes may be beneficial for the graft outcome. The role of protocol (surveillance) biopsies and the value of donor specific antibodies (DSA) monitoring are still debatable.

METHODS

This is a prospective observational study involving seventeen kidney recipients transplanted in north-eastern part of Poland who underwent "zero", 3-month and 12-month allograft biopsies as well as DSA assessment.

RESULTS

Histologic analysis of the biopsies showed subclinical acute cellular rejection in 17.6% of patients (two tubulointerstitial, one vascular) at 3-months post transplantation, and additional case of borderline rejection at the 12-month point. Moreover, two cases (11.8%) of polyomavirus BK nephropathy were diagnosed (one at 3 and one at 12 month point). None of the patients developed de novo DSA.

CONCLUSIONS

Our protocol biopsies allowed us to detect significant proportion of patients with subclinical, but histologically relevant acute cellular rejection and BK nephropathy. Early therapeutic intervention had beneficial effects in a 4-year follow up.

Acute Rejection Phenotypes in the Current Era of Immunosuppression: A Single-Center Analysis

Background

Besides ‘definitive rejection’, the Banff classification includes categories for ‘suspicious for rejection’ phenotypes. The aim of this study was to determine the frequency and phenotypes of rejection episodes in 316 consecutive renal transplants from 2009 to 2014 grouped into patients without/with pretransplant HLA-DSA (ptDSA_neg, n = 251; ptDSA_pos, n = 65).

Methods

All adequate indication (n = 125) and surveillance biopsies (n = 538) performed within the first year posttransplant were classified according to the current Banff criteria.

Results

‘Suspicious for rejection’ phenotypes were 3 times more common than ‘definitive rejection’ phenotypes in biopsies from ptDSA_neg patients (35% vs 11%) and equally common in biopsies from ptDSA_pos patients (25% vs 27%). In both groups, ‘suspicious for rejection’ phenotypes were more frequent in surveillance than in indication biopsies (28% vs 16% in ptDSA_neg patients, and 37% vs 29% in ptDSA_pos patients). ‘Borderline changes: ‘Suspicious' for acute T-cell mediated rejection’ (91%) were the dominant ‘suspicious for rejection’ phenotype in ptDSA_neg patients, whereas ‘borderline changes’ (58%) and ‘suspicious for acute/active antibody-mediated rejection’ (42%) were equally frequent in biopsies from ptDSA_pos patients. Inclusion of ‘suspicious for rejection’ phenotypes increased the 1-year incidence of clinical (ptDSA_neg patients: 18% vs 8%, P = 0.0005; ptDSA_pos patients: 24% vs 18%, P = 0.31) and (sub)clinical rejection (ptDSA_neg patients: 59% vs 22%, P < 0.0001; ptDSA_pos patients: 68% vs 40%, P = 0.004).

Conclusions

‘Suspicious for rejection’ phenotypes are very common in the current era and outnumber the frequency of ‘definitive rejection’ within the first year posttransplant.

Protocol Biopsies: Utility and Limitations

As both T cell and antibody-mediated rejection can have a subclinical phase, protocol biopsies provide an early opportunity to intervene before the onset of clinical allograft dysfunction. Protocol biopsies are usually done after reperfusion to establish baseline, between 3 and 6 months to identify subclinical rejection, and at 6-12 months to assess chronicity and persistent inflammation that have prognostic implication. Treatment of both subclinical T cell and antibody-mediated rejection prevents progression of rejection and development of interstitial fibrosis/tubular atrophy or transplant glomerulopathy. Although subclinical rejection has become less frequent in low-risk patients on triple immunosuppression containing tacrolimus, protocol biopsies may still be useful in selected population. Protocol biopsies are more likely to benefit patients at higher risk for rejection, including those who are highly sensitized, transplanted across donor-specific antibody barriers, or on calcineurin inhibitor/corticosteroids sparing regimens. Interstitial fibrosis on protocol biopsies, especially in conjunction with persistent inflammation, predicts lower allograft survival.

Total inflammation in early protocol kidney graft biopsies does not predict progression of fibrosis at one year post-transplant

INTRODUCTION

There is an uncertainty whether total inflammation in early protocol kidney graft biopsies is associated with fibrosis progression. We investigated whether total inflammation, both in fibrotic and non-fibrotic areas, at week 6 would predict fibrosis progression at one yr post-transplant.

METHODS

We included 156 single adult ABO compatible kidney recipients with adequate week 6 and one yr transplant protocol biopsies (312 biopsies). Biopsies were scored according to the current Banff criteria. In addition, fibrosis and inflammation in fibrotic and non-fibrotic areas were scored in a 10-grade semi-quantitative eyeballing system from 0% to 100%.

RESULTS

Fibrosis increased significantly from week 6 to one yr both by the 10-grade scoring system from 0.69 ± 1.07 to 1.45 ± 1.86, (mean ± SD), p < 0.001 and by Banff interstitial fibrosis (ci) scoring 0.81 ± 0.65 to 1.13 ± 0.87, p < 0.001. The 10-grade scoring system detected a larger proportion of fibrosis progressors than the Banff scoring 40.4% vs. 35.5%, p < 0.001. No significant positive association was found between inflammation at week 6 and progression of fibrosis in either of the scoring systems.

CONCLUSIONS

Total inflammation in kidney transplant biopsies at week 6 did not predict progression of fibrosis at one yr post-transplant.

Exploring genetic and non-genetic risk factors for delayed graft function, acute and subclinical rejection in renal transplant recipients

AIMS

This study aimed at identifying pharmacological factors such as pharmacogenetics and drug exposure as new predictive biomarkers for delayed graft function (DGF), acute rejection (AR) and/or subclinical rejection (SCR).

METHODS

Adult renal transplant recipients (n = 361) on cyclosporine-based immunosuppression were followed for the first 6 months after transplantation. The incidence of DGF and AR were documented as well as the prevalence of SCR at 6 months in surveillance biopsies. Demographic, transplant-related factors, pharmacological and pharmacogenetic factors (ABCB1, CYP3A5, CYP3A4, CYP2C8, NR1I2, PPP3CA and PPP3CB) were analysed in a combined approach in relation to the occurrence of DGF, AR and prevalence of SCR at month 6 using a proportional odds model and time to event model.

RESULTS

Fourteen per cent of the patients experienced at least one clinical rejection episode and only DGF showed a significant effect on the time to AR. The incidence of DGF correlated with a deceased donor kidney transplant (27% vs. 0.6% of living donors). Pharmacogenetic factors were not associated with risk for DGF, AR or SCR. A deceased donor kidney and acute rejection history were the most important determinants for SCR, resulting in a 52% risk of SCR at 6 months (vs. 11% average). In a sub-analysis of the patients with AR, those treated with rejection treatment including ATG, significantly less frequent SCR was found in the 6-month biopsy (13% vs. 50%).

CONCLUSIONS

Transplant-related factors remain the most important determinants of DGF, AR and SCR. Furthermore, rejection treatment with depleting antibodies effectively prevented SCR in 6-month surveillance biopsies.

Urinary biomarkers of chronic allograft nephropathy

PURPOSE

Chronic allograft nephropathy (CAN) is widely accepted as the leading cause of renal allograft loss after the first year post transplantation. This study aimed to identify urinary biomarkers that could predict CAN in transplant patients.

EXPERIMENTAL DESIGN

The study included 34 renal transplant patients with histologically proven CAN and 36 renal transplant patients with normal renal function. OrbiTrap MS was utilized to analysis a urinary fraction in order to identify other members of a previously identified biomarker tree . This novel biomarker pattern offers the potential to distinguish between transplant recipients with CAN and those with normal renal function.

RESULTS

The primary node of the biomarker pattern was reconfirmed as β2 microglobulin. Three other members of this biomarker pattern were identified: neutrophil gelatinase-associated lipocalin, clusterin, and kidney injury biomarker 1. Significantly higher urinary concentrations of these proteins were found in patients with CAN compared to those with normal kidney function.

CONCLUSIONS AND CLINICAL RELEVANCE

While further validation in a larger more-diverse patient population is required to determine if this biomarker pattern provides a potential means of diagnosing CAN by noninvasive methods in a clinical setting, this study clearly demonstrates the biomarkers' ability to stratify patients based on transplant function.

Can pre-implantation biopsies predict renal allograft function in pediatric renal transplant recipients?

Objectives:

To determine the utility of pre-implantation renal biopsy (PIB) to predict renal allograft outcomes.

Methods:

This is a retrospective review of all patients that underwent PIB from January 2003 to December 2011 at the Great Ormond Street Hospital for Children in London, United Kingdom. Thirty-two male patients (56%) aged 1.5-16 years (median: 10.2) at the time of transplantation were included in the study and followed-up for 33 (6-78) months. The results were compared with 33 controls.

Results:

The PIB showed normal histopathological findings in 13 patients (41%), mild chronic vascular changes in 8 (25%), focal tubular atrophy in one, moderate to severe chronic vascular change in 3, mild to moderate acute tubular damage in 6, and tissue was inadequate in one subject. Delayed graft function (DGF) was observed in 3 patients; 2 with vascular changes in PIB, and one with normal histopathological findings. Two subjects with PIB changes lost their grafts. The estimated glomerular filtration rate at 3-, and 6-months post-transplantation was lower in children with abnormal PIB changes compared with those with normal PIB. There was one case of DGF in the control group, and 4 children lost their grafts including the one with DGF.

Conclusion:

Pre-implantation renal biopsy can provide important baseline information of the graft with implications on subsequent medical treatment for pediatric renal transplant recipients.

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.

Long Noncoding RNAs in Urine Are Detectable and May Enable Early Detection of Acute T Cell-Mediated Rejection of Renal Allografts

BACKGROUND

Long noncoding RNAs (lncRNAs) are novel intracellular noncoding ribonucleotides regulating the genome and proteome. They are detectable in the blood of patients with acute kidney injury. We tested whether lncRNAs are present in urine and may serve as new predictors of outcome in renal transplant patients with acute rejection.

METHODS

A global lncRNA expression analysis was performed with RNA from urine of patients with acute T cell-mediated renal allograft rejection and control transplant patients. Deregulated lncRNAs were confirmed in kidney biopsies and urine in a validation cohort of 62 patients with acute rejection, 10 of them after successful antirejection therapy, and 31 control transplant patients.

RESULTS

A global screen revealed several lncRNAs to be deregulated in urine of patients with acute rejection. Three intergenic lncRNAs, LNC-MYH13-3:1, RP11-395P13.3-001, and RP11-354P17.15-001, were most strongly altered. These were validated in the whole cohort of patients. RP11-395P13.3-001 and RP11-354P17.15-001 were upregulated in patients with acute rejection compared with controls. Only levels of RP11-354P17.15-001 normalized in patients with acute rejection after successful antirejection therapy. RP11-354P17.15-001 was associated with higher decline in glomerular filtration rate 1 year after transplantation. In vitro, in tubular epithelial cells, all lncRNAs were enriched by interleukin-6 treatment, but only RP11-395P13.3-001 and RP11-354P17.15-001 increased in cell culture supernatant, indicating that these lncRNAs might be secreted under inflammatory conditions.

CONCLUSIONS

lncRNAs are strongly altered in urine of patients with acute rejection. Urinary RP11-354P17.15-001 may serve as a novel biomarker of acute kidney rejection, identifying patients with acute rejection and predicting loss of kidney function.

Transcriptional Perturbations in Graft Rejection

BACKGROUND

Understanding the regulatory interplay of relevant microRNAs (miRNAs) and messenger RNAs (mRNAs) in the rejecting allograft will result in a better understanding of the molecular pathophysiology of alloimmune injury.

METHODS

One hundred sixty-seven allograft biopsies, with (n = 47) and without (n = 120) central histology for Banff scored acute rejection (AR), were transcriptionally profiled for mRNA and miRNA by whole genome microarrays and multiplexed microfluidic quantitative polymerase chain reaction, respectively. A customized database was curated (GO-Elite) and used to identify AR-specific dysregulated mRNAs and the role of perturbations of their relevant miRNAs targets during AR.

RESULTS

The AR-specific changes in 1035 specific mRNAs were mirrored by AR-specific perturbations in 9 relevant miRNAs as predicted by Go-Elite and were regulated specifically by p53 and forkhead box P3. Infiltrating lymphocytes and the renal tubules drove the miRNA tissue pertubations in rejection, involving message degradation and transcriptional/translational activation. The expression of many of these miRNAs significantly associated with the intensity of the Banff-scored interstitial inflammation and tubulitis.

CONCLUSIONS

There is a highly regulated interplay between specific mRNA/miRNAs in allograft rejection that drive both immune-mediated injury and tissue repair during AR.

Renal allograft fibrosis: biology and therapeutic targets

Renal tubulointerstitial fibrosis is the final common pathway of progressive renal diseases. In allografts, it is assessed with tubular atrophy as interstitial fibrosis/tubular atrophy (IF/TA). IF/TA occurs in about 40% of kidney allografts at 3-6 months after transplantation, increasing to 65% at 2 years. The origin of renal fibrosis in the allograft is complex and includes donor-related factors, in particular in case of expanded criteria donors, ischemia-reperfusion injury, immune-mediated damage, recurrence of underlying diseases, hypertensive damage, nephrotoxicity of immunosuppressants, recurrent graft infections, postrenal obstruction, etc. Based largely on studies in the non-transplant setting, there is a large body of literature on the role of different cell types, be it intrinsic to the kidney or bone marrow derived, in mediating renal fibrosis, and the number of mediator systems contributing to fibrotic changes is growing steadily. Here we review the most important cellular processes and mediators involved in the progress of renal fibrosis, with a focus on the allograft situation, and discuss some of the challenges in translating experimental insights into clinical trials, in particular fibrosis biomarkers or imaging modalities.

Antibody-mediated rejection in young kidney transplant recipients: the dilemma of noncompliance and insufficient immunosuppression

BACKGROUND

Antibody-mediated rejection (ABMR) is a recognized cause of late kidney allograft loss. Although ABMR may occur despite appropriate chronic immunosuppressive therapy, non-adherence both facilitates and accelerates the activation of the effector phase of the humoral immune response against the donor tissue, leading in turn to progressive kidney allograft rejection. Given the poor efficacy of rescue therapies for both acute and chronic late ABMR, establishing appropriate preventive strategies at different times before and after transplantation is a critical management goal.

CASE-DIAGNOSIS/TREATMENT

In this report, we discuss the differential diagnoses and management of ABMR based on the clinical case report of a young kidney transplant recipient with progressive ABMR due to poor immunosuppressive adherence. In the absence of sensitive and specific non-invasive monitoring tools for alloimmune activation, the clinical dilemma in the management of the adolescent patient lies in differentiating between suboptimal prescribed immunosuppression and deliberate non-adherence to adequate immunosuppression dosing. Despite the advent of therapies to reduce ABMR injury, the graft is destined for untimely functional loss.

CONCLUSIONS

New biomarkers and tools for the accurate characterization of alloimmune risk before and after transplantation, and serial testing for de novo changes in circulating donor-specific alloantibodies, are urgently needed to support the delivery of optimized immunosuppression exposure.

The value of long-term protocol biopsies after kidney transplantation

Protocol biopsies for the detection and treatment of subclinical rejection in the early period after kidney transplantation are useful for preventing allograft dysfunction. However, little has been reported on the relationship between subclinical rejection and long-term protocol biopsies. In this review, we examine the potential benefits associated with long-term allograft biopsies focusing on the issue of immunological and non-immunological factors. Early detection and treatment of subclinical rejection improves outcome. However, the benefit of long-term allograft biopsies is largely unproved, and the strategy is yet to be widely implemented. The procurement of long-term protocol biopsies for the sole purpose of detecting subclinical rejection may be unwarranted. On the other hand, the early detection of IgA nephropathy using long-term protocol biopsy may improve graft survival. In addition, assessment of long-term protocol biopsies is useful not only for detection of calcineurin inhibitor nephrotoxicity, but also for follow-up after withdrawal of calcineurin inhibitor regimens. Also, identifying normal histology on a protocol biopsy may inform us about the safety of reducing overall immunosuppression. Thus, the potential benefit of long-term protocol biopsy may be of clinical significance for the detection of graft dysfunction as a result of non-immune factors, such as recurrence of glomerulonephritis and calcineurin inhibitor nephrotoxicity, rather than subclinical rejection.

Autologous bone marrow derived mesenchymal stromal cell therapy in combination with everolimus to preserve renal structure and function in renal transplant recipients

Background

Kidney transplantation has improved survival and quality of life for patients with end-stage renal disease. Despite excellent short-term results due to better and more potent immunosuppressive drugs, long-term survival of transplanted kidneys has not improved accordingly in the last decades. Consequently there is a strong interest in immunosuppressive regimens that maintain efficacy for the prevention of rejection, whilst preserving renal structure and function. In this respect the infusion of mesenchymal stromal cells (MSCs) may be an interesting immune suppressive strategy. MSCs have immune suppressive properties and actively contribute to tissue repair. In experimental animal studies the combination of mammalian target of rapamycin (mTOR) inhibitor and MSCs was shown to attenuate allo immune responses and to promote allograft tolerance. The current study will test the hypothesis that MSC treatment, in combination with the mTOR inhibitor everolimus, facilitates tacrolimus withdrawal, reduces fibrosis and decreases the incidence of opportunistic infections compared to standard tacrolimus dose.

Methods/design

70 renal allograft recipients, 18–75 years old, will be included in this Phase II, open label, randomized, non-blinded, prospective, single centre clinical study. Patients in the MSC treated group will receive two doses of autologous bone marrow derived MSCs IV (target 1,5x10⁶, Range 1-2x10⁶ million MSCs per/kg body weight), 7 days apart, 6 and 7 weeks transplantation in combination with everolimus and prednisolone. At the time of the second MSC infusion tacrolimus will be reduced to 50% and completely withdrawn 1 week later. Patients in the control group will receive everolimus, prednisolone and standard dose tacrolimus. The primary end point is to compare fibrosis by quantitative Sirius Red scoring of MSC treated and untreated groups at 6 months compared to 4 weeks post-transplant. Secondary end points include: composite end point efficacy failure (Biopsy Proven Acute Rejection, graft loss or death); renal function and proteinuria; opportunistic infections; immune monitoring and “subclinical” cardiovascular disease groups by assessing echocardiography in the different treatment groups.

Discussion

This study will provide information whether MSCs in combination with everolimus can be used for tacrolimus withdrawal, and whether this strategy leads to preservation of renal structure and function in renal recipients.

Trial registration

NCT02057965.

Monitoring T cell alloreactivity

Currently, immunosuppressive therapy in kidney transplant recipients is center-specific, protocol-driven, and adjusted according to functional or histological evaluation of the allograft and/or signs of drug toxicity or infection. As a result, a large fraction of patients receive too much or too little immunosuppression, exposing them to higher rates of infection, malignancy and drug toxicity, or increased risk of acute and chronic graft injury from rejection, respectively. The individualization of immunosuppression requires the development of assays able to reliably quantify and/or predict the magnitude of the recipient's immune response toward the allograft. As alloreactive T cells are central mediators of allograft rejection, monitoring T cell alloreactivity has become a priority for the transplant community. Among available assays, flow cytometry based phenotyping, T cell proliferation, T cell cytokine secretion, and ATP release (ImmuKnow), have been the most thoroughly tested. While numerous cross-sectional studies have found associations between the results of these assays and the presence of clinically relevant post-transplantation outcomes, data from prospective studies are still scanty, thereby preventing widespread implementation in the clinic. Future studies are required to test the hypothesis that tailoring immunosuppression on the basis of results offered by these biomarkers leads to better outcomes than current standard clinical practice.

The role of macrophages in the development of human renal allograft fibrosis in the first year after transplantation

The aim of this study was to investigate the role of infiltrating macrophages in renal allograft fibrosis. Forty-six protocol renal allograft biopsies obtained 1 year after transplantation were stained with Sirius red to quantify fibrosis and double stained with CD68 and CD206 to identify the proportion of alternatively activated (M2) macrophages. Biopsies were analyzed for gene expression by microarray, which was correlated with macrophage infiltration and the severity of fibrosis. The number of infiltrating CD68+ cells strongly correlated with the percentage of interstitial fibrosis (r = 0.73, p < 0.0001). Macrophage infiltration at 1 year correlated with renal dysfunction at 1, 12 and 36 months posttransplant (estimated GFR low vs. high: 1 month 78 ± 26 vs. 54 ± 19 mL/min, p < 0.01; 12 months 87 ± 29 vs. 64 ± 19 mL/min, p < 0.05; 36 months 88 ± 33 vs. 60 ± 24 mL/min, p < 0.05). Ninety-two percent of infiltrating macrophages exhibited an M2 phenotype with CD68+ CD206+ dual staining. Gene microarrays demonstrated an alloimmune response with up-regulation of interferon-γ-response genes despite the lack of rejection or inflammatory infiltrate. Consistent with this was the presence of CXCL10 in proximal tubular cells at 3 months. This suggests that M2 macrophage proliferation, or infiltration, was associated with subclinical alloimmune inflammation, tubular injury and progression of fibrosis.

A single-center cohort study to define the role of pretransplant biopsy score in the long-term outcome of kidney transplantation

BACKGROUND

The role of pretransplant biopsy in defining the quality of kidney grafts is still debated. The aim of this study was to investigate the influence of pretransplant biopsy score on long-term graft outcome.

METHODS

In a retrospective cohort study, we analyzed 372 recipients of single kidney transplantation (SKT) from deceased donors between 1997 and 2007, with an available pretransplant biopsy. We evaluated 5- and 10-year graft survival, incidence of delayed graft function, and estimated glomerular filtration rate at 1 and 5 years.

RESULTS

Graft survival at 5 and 10 years was significantly better for recipients with a score of 0 compared to transplants with a score of 1 to 5, whereas we did not observe any significant difference among transplants with a score of 1 through 4. Survival of kidneys with a score of 5 was significantly worse compared to grafts with a score of 1 to 4. In a multivariate Cox model, only pretransplant histological score was significantly associated with graft survival. Transplants with a score of 0 and 5 had the best and the worst graft function, respectively, both at 1 and 5 years, whereas we did not observe any difference among patients with a score of 1 through 4. In a multivariate logistic regression, pretransplant histological score was independently associated with the prevalence of an estimated glomerular filtration rate less than 30 mL/min at 5 years. Finally, delayed graft function rate was significantly higher in recipients with a score of 5 compared to patients with a score of 1 to 4 and score of 0.

CONCLUSIONS

Our data suggest that 1) pretransplant histological score may predict long-term graft outcome and 2) allocation of kidneys with a score of 4 to SKT provides an acceptable long-term graft function and survival.

The Interplay between inflammation and fibrosis in kidney transplantation

Serial surveillance renal allograft biopsies have shown that early subclinical inflammation constitutes a risk factor for the development of interstitial fibrosis. More recently, it has been observed that persistent inflammation is also associated with fibrosis progression and chronic humoral rejection, two histological conditions associated with poor allograft survival. Treatment of subclinical inflammation with steroid boluses prevents progression of fibrosis and preserves renal function in patients treated with a cyclosporine-based regimen. Subclinical inflammation has been reduced after the introduction of tacrolimus based regimens, and it has been shown that immunosuppressive schedules that are effective in preventing acute rejection and subclinical inflammation may prevent the progression of fibrosis and chronic humoral rejection. On the other hand, minimization protocols are associated with progression of fibrosis, and noncompliance with the immunosuppressive regime constitutes a major risk factor for chronic humoral rejection. Thus, adequate immunosuppressive treatment, avoiding minimization strategies and reinforcing educational actions to prevent noncompliance, is at present an effective approach to combat the progression of fibrosis.

Early protocol biopsies in pediatric renal transplantation: interest for the adaptation of immunosuppression

GPB are often performed in PRT to detect subclinical acute rejection or IF/TA. Reducing immunosuppression side effects without increasing rejection is a major concern in PRT. We report the results of GPB in children transplanted with a steroid-sparing protocol adapted to immunological risk. Children under 18 yr who received a renal transplantation between April 1, 2009 and May 31, 2012 were included. Immunosuppression consisted of an antibody induction therapy, tacrolimus, and MMF for all recipients. CSs were administered to children under five yr old, or receiving a second allograft. Twenty-eight children were included, 50% were CSs free. GPB were performed between three and six months. IF/TA was documented in seven biopsies; four of these seven children were CS free. One child, with CSs, presented a borderline rejection, and another child, steroid free, with significant inflammatory interstitial infiltrate, considered as a subclinical rejection, was treated with CSs pulses. The median eGFR was stable (74, 67.5, and 82 mL/min/1.73 m² at, respectively, seven days, three months, and one yr). Patient and graft survival were 100%. These results have to be confirmed in a larger cohort, with long-term follow-up.

Mesenchymal stromal cells to prevent fibrosis in kidney transplantation

PURPOSE OF REVIEW

Kidney transplantation has improved the life expectancy and quality of life for patients with end-stage renal failure. However, despite the impressive improvements in short-term outcome parameters because of better and more potent immunosuppressive drugs, the long-term survival of renal allografts has changed little over the last decades. Sustained inflammation in the areas of interstitial fibrosis and tubular atrophy (IFTA) is a strong predictor of allograft failure. Mesenchymal stromal cells (MSCs) have potent anti-inflammatory and reparative properties, and could thus play a role in controlling these processes.

RECENT FINDINGS

Local resident MSCs and exogenous MSCs have been implicated in the repair of the injured kidney, mostly by their paracrine functions. In the experimental models and clinical trials, first results with MSCs for the treatment of inflammation and IFTA suggest beneficial effects.

SUMMARY

Endogenously and exogenously administered MSCs might enhance the intrinsic reparative capabilities of the kidney in transplant recipients and maybe developed as a tool to control both inflammation and fibrosis.

Correlation of serum and urinary matrix metalloproteases/tissue inhibitors of metalloproteases with subclinical allograft fibrosis in renal transplantation

Progressive interstitial fibrosis and tubular atrophy (IF/TA) is a leading cause of chronic allograft dysfunction. Increased extracellular matrix remodeling regulated by matrix metalloproteases (MMPs) and their inhibitors (TIMPs) has been implicated in the development of IF/TA. The aim of this study was to investigate whether urinary/serum MMPs/TIMPs correlate with subclinical IF/TA detected in surveillance biopsies within the first 6months post-transplant. We measured eight different MMPs/TIMPs simultaneously in urine and serum samples from patients classified as normal histology (n=15), IF/TA 1 (n=15) and IF/TA 2-3 (n=10). There was no difference in urinary MMPs/TIMPs among the three groups, and only 1/8 serum MMPs/TIMPs (i.e. MMP-1) was significantly elevated in biopsies with IF/TA 2-3 (p=0.01). In addition, urinary/serum MMPs/TIMPs were not different between surveillance biopsies demonstrating an early development of IF/TA (i.e. delta IF/TA≥1 compared to a previous biopsy obtained three months before; n=11) and stable grade of IF/TA (i.e. delta IF/TA=0; n=20). Next, we investigated whether urinary/serum MMP/TIMP levels are elevated during acute subclinical tubulitis in surveillance biopsies obtained within the first 6months post-transplant (n=25). Compared to biopsies with normal histology, serum MMPs/TIMPs were not different; however, all urinary MMP/TIMP levels were numerically higher during subclinical tubulitis (MMP-1, MMP-7, TIMP-1 with p≤0.04). We conclude that urinary/serum MMPs/TIMPs do hardly correlate with existing or early developing IF/TA in surveillance biopsies obtained within the first 6months post-transplant. This could be explained by the dynamic process of extracellular matrix remodeling, which seems to be active during acute tubulo-interstitial injury/inflammation, but not in quiescent IF/TA.

The short-term impact of protocol biopsies in a live-related renal transplant program using tacrolimus based immunosuppression

The aim of the study was to assess the impact of protocol biopsies in a live-related renal transplant program using tacrolimus-based immunosuppression in the short term. Eighty-three live-related transplant recipients were randomly allocated to protocol biopsy group (Group I, n = 40) and a control group (Group II, n = 43). Other immunosuppressants in these groups consisted of either mycophenolate mofetil or azathioprine and steroids. Protocol biopsies were conducted in biopsy group at 1, 6, and 12 months post-transplant. The non-biopsy group was followed by serial serum creatinine and biopsies in them were conducted as and when clinically indicated. Both groups were analyzed at 12 months with respect to graft function and survival. The two groups were similar with respect to age, number of dialysis pre-operatively, tacrolimus levels, induction therapy, donor age, and donor glomerular filtration rate. Forty protocol biopsies were conducted at 1 month, 31 at 6 months, and 26 at 12 months. The prevalence of sub-clinical rejection at 1, 6, and 12 months in these biopsies was 17.5%, 11.2%, and 10.3%, respectively. The prevalence of calcineurin inhibitor toxicity during same period was 15%, 15.5%, and 14.4%, respectively. The cumulative rejection rate in Group I and Group II at 12-month follow-up was 10.3% and 11.3% (P = 0.78), respectively, and cumulative calcineurin inhibitor toxicity at 12 months was 14.4% and 9.3% (P = 0.59), respectively, were not statistically significant. There was no difference in graft survival and function at 1 year. Protocol biopsies have a limited role in a well-matched renal transplant program with tacrolimus-based immunosuppression in the short term. However, the long-term impact of protocol biopsies needs further evaluation.

Do protocol transplant biopsies improve kidney transplant outcomes?

PURPOSE OF REVIEW

The research undertaken on 'protocol' renal transplant biopsies has provided a rich, if not the richest, approach to better understanding of the immune and nonimmune impacts upon the transplant. The purpose of this review is to detail how the direct benefit to the patient also lies in these renamed 'surveillance' biopsies.

RECENT FINDINGS

Undertaken at fixed time points after transplantation, biopsy provides individual diagnoses with which the clinician can vary immunosuppression both in intensity and in the type of agent used to modify pathological processes early in their course. Initial nonfunction from acute tubular necrosis, subclinical cellular and humoral rejection, calcineurin inhibitor nephrotoxicity, BK virus nephropathy and recurrent glomerulonephritis are all important diagnoses for which early intervention provides better therapeutic outcomes than delaying until they are clinically evident.

SUMMARY

This review provides the recent evidence that has convinced many transplant units to embark upon surveillance programmes for their patients in order to individualize their immunosuppression and thus gain better outcomes.

Long-term interleukin-2 assessment after conversion from a twice-daily to once-daily tacrolimus regimen in stable kidney recipients

Conversion to tacrolimus (Tac) to once daily (Tac-O) formulation is commonly followed by a 20% reduction in Tac trough levels in the first month. It is not associated with modifications of renal function but there is the issue of its effects on inflammatory cytokines and on subclinical rejection. The aim of our study was to evaluate long-term interleukins (IL)-2 profiles in stable renal transplant patients after Tac-O conversion. We enrolled 10 stable kidney transplant patients converted to Tac-O. Tac trough levels, serum creatinine concentrations, glomerular filtration rate using the Modification of Diet in Renal Disease formula, C-reactive protein, IL-2 levels, and clinical assessments were performed monthly for 6 months before and 12 months after conversion. Despite the significant reduction in Tac trough levels, we did not observe alterations suggestive of clinical or subclinical acute rejection.

Detection of clinical and subclinical tubulo-interstitial inflammation by the urinary CXCL10 chemokine in a real-life setting

Urinary CXCL10 is a promising noninvasive biomarker for tubulo-interstitial allograft inflammation, but its diagnostic characteristics have not been assessed in a real-life setting. We investigated urinary CXCL10 in 213 consecutive renal allograft recipients having 362 surveillance biopsies at 3/6 months and 80 indication biopsies within the first year posttransplant. Allograft histology results were classified as (i) acute Banff score zero, (ii) interstitial infiltrates only, (iii) tubulitis t1, (iv) tubulitis t2-3 and (v) isolated vascular compartment inflammation. For clinical and subclinical pathologies, urinary CXCL10 correlated well with the extent of tubulo-interstitial inflammation. To determine diagnostic characteristics of urinary CXCL10, histological groups were separated into two categories: no relevant inflammation (i.e. acute Banff score zero and interstitial infiltrates only) versus all other pathologies (i.e. tubulitis t1-3 and isolated vascular compartment inflammation). For subclinical pathologies, AUC was 0.69 (sensitivity 61%, specificity 72%); for clinical pathologies, AUC was 0.74 (sensitivity 63%, specificity 80%). A urinary CXCL10-guided biopsy strategy would have reduced performance of surveillance and indication biopsies by 61% and 64%, respectively. Missed (sub)clinical pathologies were mostly tubulitis t1 and isolated vascular compartment lesions. In real life, urinary CXCL10 had clinically useful diagnostic properties making it a candidate biomarker to guide allograft biopsies.

Circulating lymphocyte subsets in different clinical situations after renal transplantation

Phenotypic characterization of T and B lymphocytes allows the discrimination of functionally different subsets. Here, we questioned whether changes in peripheral lymphocyte subset distribution reflect specific clinical and histopathological entities after renal transplantation. Sixty-five renal transplant recipients with either histologically proven (sub)clinical acute rejection or chronic allograft dysfunction, or without abnormalities were studied for their peripheral lymphocyte subset composition and compared with 15 healthy control individuals. Naive, memory and effector CD8(+) T-cell counts were measured by staining for CD27, CD28 and CD45RO/RA. In addition, we studied the CD25(+) CD4(+) T-cell population for its composition regarding regulatory Foxp3(+) CD45RO(+) CD127(-) cells and activated CD45RO(+) CD127(+) cells. Naive, non-switched and switched memory B cells were defined by staining for IgD and CD27. We found a severe decrease in circulating effector-type CD8(+) T cells in recipients with chronic allograft dysfunction at 5 years after transplantation. Percentages of circulating CD25(+) CD127(low) CD4(+) regulatory T cells after transplantation were reduced, but we could not detect any change in the percentage of CD127(+) CD45RO(+) CD4(+) activated T cells in patients at any time or condition after renal transplantation. Regardless of clinical events, all renal transplant recipients showed decreased total B-cell counts and a more differentiated circulating B-cell pool than healthy individuals. The changes in lymphocyte subset distribution probably reflect the chronic antigenic stimulation that occurs in these transplant recipients. To determine the usefulness of lymphocyte subset-typing in clinical practice, large cohort studies are necessary.

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.

Early subclinical rejection as a risk factor for late chronic humoral rejection

BACKGROUND

Subclinical rejection and interstitial fibrosis and tubular atrophy (IF/TA) in protocol biopsies are associated with outcome. We study the relationship between histologic lesions in early protocol biopsies and histologic diagnoses in late biopsies for cause.

MATERIALS AND METHODS

Renal transplants with a protocol biopsy performed within the first 6 months posttransplant between 1988 and 2006 were reviewed. Biopsies were evaluated according to Banff criteria, and C4d staining was available in biopsies for cause.

RESULTS

Of the 517 renal transplants with a protocol biopsy, 109 had a subsequent biopsy for cause which showed the following histological diagnoses: chronic humoral rejection (CHR) (n=44), IF/TA (n=42), recurrence of the primary disease (n=11), de novo glomerulonephritis (n=7), T-cell-mediated rejection (n=4), and polyoma virus nephropathy (n=1). The proportion of retransplants (15.9% vs. 2.3%, P=0.058) and the prevalence of subclinical rejection were higher in patients with CHR than in patients with IF/TA (52.3% vs. 28.6%, P=0.0253). Demographic donor and recipient characteristics and clinical data at the time of protocol biopsy were not different between groups. Logistic regression analysis showed that subclinical rejection (relative risk, 2.52; 95% confidence interval, 1.1-6.3; P=0.047) but not retransplantation (relative risk, 6.7; 95% confidence interval, 0.8-58.8; P=0.085) was associated with CHR.

CONCLUSION

Subclinical rejection in early protocol biopsies is associated with late appearance of CHR.