Chronic histological damage in early indication biopsies is an independent risk factor for late renal allograft failure

Emerging phenotypes in kidney transplant rejection

PURPOSE OF REVIEW

This review focuses on more recently emerging rejection phenotypes in the context of time post transplantation and the resulting differential diagnostic challenges. It also discusses how novel ancillary diagnostic tools can potentially increase the accuracy of biopsy-based rejection diagnosis.

RECENT FINDINGS

With advances in reducing immunological risk at transplantation and improved immunosuppression treatment renal allograft survival improved. However, allograft rejection remains a major challenge and represent a frequent course for allograft failure. With prolonged allograft survival, novel phenotypes of rejection are emerging, which can show complex overlap and transition between cellular and antibody-mediated rejection mechanisms as well as mixtures of acute/active and chronic diseases. With the emerging complexity in rejection phenotypes, it is crucial to achieve diagnostic accuracy in the individual patient.

SUMMARY

The prospective validation and adoption of novel molecular and computational diagnostic tools into well defined and appropriate clinical context of uses will improve our ability to accurately diagnose, stage, and grade allograft rejection.

Contemporary and Emerging MRI Strategies for Assessing Kidney Allograft Complications: Arterial Stenosis and Parenchymal Injury, From the AJR Special Series on Imaging of Fibrosis

MRI plays an important role in the evaluation of kidney allografts for vascular complications as well as parenchymal insults. Transplant renal artery stenosis, the most common vascular complication of kidney transplant, can be evaluated by MRA using gadolinium and nongadolinium contrast agents as well as by unenhanced MRA techniques. Parenchymal injury occurs through a variety of pathways, including graft rejection, acute tubular injury, BK polyomavirus infection, drug-induced interstitial nephritis, and pyelonephritis. Investigational MRI techniques have sought to differentiate among these causes of dysfunction as well as to assess the degree of interstitial fibrosis or tubular atrophy (IFTA)-the common end pathway for all of these processes-which is currently evaluated by invasively obtained core biopsies. Some of these MRI sequences have shown promise in not only assessing the cause of parenchymal injury but also assessing IFTA noninvasively. This review describes current clinically used MRI techniques and previews promising investigational MRI techniques for assessing complications of kidney grafts.

Multiscale genetic architecture of donor-recipient differences reveals intronic LIMS1 mismatches associated with kidney transplant survival

Donor-recipient (D-R) mismatches outside of human leukocyte antigens (HLAs) contribute to kidney allograft loss, but the mechanisms remain unclear, specifically for intronic mismatches. We quantified non-HLA mismatches at variant-, gene-, and genome-wide scales from single nucleotide polymorphism (SNP) data of D-Rs from 2 well-phenotyped transplant cohorts: Genomics of Chronic Allograft Rejection (GoCAR; n = 385) and Clinical Trials in Organ Transplantation-01/17 (CTOT-01/17; n = 146). Unbiased gene-level screening in GoCAR uncovered the LIMS1 locus as the top-ranked gene where D-R mismatches associated with death-censored graft loss (DCGL). A previously unreported, intronic, LIMS1 haplotype of 30 SNPs independently associated with DCGL in both cohorts. Haplotype mismatches showed a dosage effect, and minor-allele introduction to major-allele-carrying recipients showed greater hazard of DCGL. The LIMS1 haplotype and the previously reported LIMS1 SNP rs893403 are expression quantitative trait loci (eQTL) in immune cells for GCC2 (not LIMS1), which encodes a protein involved in mannose-6-phosphase receptor (M6PR) recycling. Peripheral blood and T cell transcriptome analyses associated the GCC2 gene and LIMS1 SNPs with the TGF-β1/SMAD pathway, suggesting a regulatory effect. In vitro GCC2 modulation impacted M6PR-dependent regulation of active TGF-β1 and downstream signaling in T cells. Together, our data link LIMS1 locus D-R mismatches to DCGL via GCC2 eQTLs that modulate TGF-β1-dependent effects on T cells.

Association of Predicted HLA T-Cell Epitope Targets and T-Cell-Mediated Rejection After Kidney Transplantation

RATIONALE & OBJECTIVE

The relationship between human leukocyte antigen (HLA) molecular mismatches and T-cell-mediated rejection (TCMR) is unknown. We investigated the associations between the different donor HLA-derived T-cell targets and the occurrence of TCMR and borderline histologic changes suggestive of TCMR after kidney transplantation.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

All kidney transplant recipients at a single center between 2004 and 2013 with available biopsy data and a DNA sample for high-resolution HLA donor/recipient typing (N = 893).

EXPOSURE

Scores calculated by the HLA matching algorithm PIRCHE-II and HLA eplet mismatches.

OUTCOME

TCMR, borderline changes suggestive of TCMR, and allograft failure.

ANALYTICAL APPROACH

Multivariable cause-specific hazards models were fit to characterize the association between HLA epitopes targets and study outcomes.

RESULTS

We found 277 patients developed TCMR, and 134 developed only borderline changes suggestive of TCMR on at least 1 biopsy. In multivariable analyses, only the PIRCHE-II scores for HLA-DRB1 and HLA-DQB1 were independently associated with the occurrence of TCMR and with allograft failure; this was not the case for HLA class I molecules. If restricted to rejection episodes within the first 3 months after transplantation, only the T-cell epitope targets originating from the donor's HLA-DRB1 and HLA-DQB1, but not class I molecules, were associated with the early acute TCMR. Also, the median PIRCHE-II score for HLA class II was statistically different between the patients with TCMR compared to the patients without TCMR (129 [IQR, 60-240] vs 201 [IQR, 96-298], respectively; P < 0.0001). These differences were not observed for class I PIRCHE-II scores.

LIMITATIONS

Observational clinical data and residual confounding.

CONCLUSIONS

In the absence of HLA-DSA, HLA class II but not class I mismatches are associated with early episodes of acute TCMR and allograft failure. This suggests that current immunosuppressive therapies are largely able to abort the most deleterious HLA class I-directed alloimmune processes; however, alloresponses against HLA-DRB1 and HLA-DQB1 molecular mismatches remain insufficiently suppressed.

PLAIN-LANGUAGE SUMMARY

Genetic differences in the human leukocyte antigen (HLA) complex between kidney transplant donors and recipients play a central role in T-cell-mediated rejection (TCMR), which can lead to failure of the transplanted kidney. Evaluating this genetic disparity (mismatch) in the HLA complex at the molecular (epitope) level could contribute to better prediction of the immune response to the donor organ posttransplantation. We investigated the associations of the different donor HLA-derived T-cell epitope targets and scores obtained from virtual crossmatch algorithms with the occurrence of TCMR, borderline TCMR, and graft failure after kidney transplantation after taking into account the influence of donor-specific anti-HLA antibodies. This study illustrates the greater importance of the molecular mismatches in class II molecules compared to class I HLA molecules.

Data-Driven Chronic Allograft Phenotypes: A Novel and Validated Complement for Histologic Assessment of Kidney Transplant Biopsies

BACKGROUND

No validated system currently exists to realistically characterize the chronic pathology of kidney transplants that represents the dynamic disease process and spectrum of disease severity. We sought to develop and validate a tool to describe chronicity and severity of renal allograft disease and integrate it with the evaluation of disease activity.

METHODS

The training cohort included 3549 kidney transplant biopsies from an observational cohort of 937 recipients. We reweighted the chronic histologic lesions according to their time-dependent association with graft failure, and performed consensus k-means clustering analysis. Total chronicity was calculated as the sum of the weighted chronic lesion scores, scaled to the unit interval.

RESULTS

We identified four chronic clusters associated with graft outcome, based on the proportion of ambiguous clustering. The two clusters with the worst survival outcome were determined by interstitial fibrosis and tubular atrophy (IFTA) and by transplant glomerulopathy. The chronic clusters partially overlapped with the existing Banff IFTA classification (adjusted Rand index, 0.35) and were distributed independently of the acute lesions. Total chronicity strongly associated with graft failure (hazard ratio [HR], 8.33; 95% confidence interval [CI], 5.94 to 10.88; P<0.001), independent of the total activity scores (HR, 5.01; 95% CI, 2.83 to 7.00; P<0.001). These results were validated on an external cohort of 4031 biopsies from 2054 kidney transplant recipients.

CONCLUSIONS

The evaluation of total chronicity provides information on kidney transplant pathology that complements the estimation of disease activity from acute lesion scores. Use of the data-driven algorithm used in this study, called RejectClass, may provide a holistic and quantitative assessment of kidney transplant injury phenotypes and severity.

Pure T-cell mediated rejection following kidney transplant according to response to treatment

The focus of studies on kidney transplantation (KT) has largely shifted from T-cell mediated rejection (TCMR) to antibody-mediated rejection (ABMR). However, there are still cases of pure acute TCMR in histological reports, even after a long time following transplant. We thus evaluated the impact of pure TCMR on graft survival (GS) according to treatment response. We also performed molecular diagnosis using a molecular microscope diagnostic system on a separate group of 23 patients. A total of 63 patients were divided into non-responders (N = 22) and responders (N = 44). Non-response to rejection treatment was significantly associated with the following factors: glomerular filtration rate (GFR) at biopsy, ΔGFR, TCMR within one year, t score, and IF/TA score. We also found that non-responder vs. responder (OR = 3.31; P = 0.036) and lower GFR at biopsy (OR = 0.56; P = 0.026) were independent risk factors of graft failure. The responders had a significantly superior overall GS rate compared with the non-responders (P = 0.004). Molecular assessment showed a good correlation with histologic diagnosis in ABMR, but not in TCMR. Solitary TCMR was a significant risk factor of graft failure in patients who did not respond to rejection treatment.

Incidence, risk factors, treatment, and consequences of antibody-mediated kidney transplant rejection: A systematic review

BACKGROUND

Antibody-mediated rejection (AMR) is a leading cause of kidney allograft failure, but its incidence, risk factors, and outcomes are not well understood.

METHODS

We searched Ovid MEDLINE, Cochrane, EMBASE, and Scopus from January 2000 to January 2020 to identify published cohorts of ≥500 incident adult or 75 pediatric kidney transplant recipients followed for ≥1 year post-transplant.

RESULTS

At least two reviewers screened 5061 articles and abstracts; 28 met inclusion criteria. Incidence of acute AMR was 1.1%-21.5%; most studies reported 3%-12% incidence, usually within the first year post-transplant. Few studies reported chronic AMR incidence, from 7.5%-20.1% up to 10 years. Almost all patients with acute or chronic AMR received corticosteroids and intravenous immunoglobulin; most received plasmapheresis, and approximately half with rituximab. Most studies examining death-censored graft failure identified AMR as an independent risk factor. Few reported refractory AMR rates or outcomes, and none examined costs. Most studies were single-center and varied greatly in design.

CONCLUSIONS

Cohort studies of kidney transplant recipients demonstrate that AMR is common and associated with increased risk of death-censored graft failure, but studies vary widely regarding populations, definitions, and reported incidence. Gaps remain in our understanding of refractory AMR, its costs, and resulting quality of life.

Transplant outcomes using kidneys from high KDPI acute kidney injury donors

Kidney transplant (KT) outcomes from high kidney donor profile index (KDPI ≥85%) donors with acute kidney injury (AKI) remain underreported. KT from 172 high KDPI Acute Kidney Injury Network (AKIN) stage 0-1 donors and 76 high KDPI AKIN stage 2-3 donors from a single center were retrospectively assessed. The AKIN 2-3 cohort had more delayed graft function (71% vs. 37%, p < .001). At one year, there were no differences in the estimated glomerular filtration rate (44 ± 17 vs. 46 ± 18, p = .42) or fibrosis on protocol biopsy (ci, p = .85). Donor terminal creatinine (p = .59) and length of delayed graft function (p = .39) did not impact one-year eGFR. There were more primary nonfunction (PNF) events in the high KDPI AKIN 2-3 group (5.3% vs. 0.6%, p = .02). With a median follow-up of 3.8 years, one-year death-censored graft failure was 3.5% for AKIN 0-1 and 14.5% for AKIN 2-3 (HR 2.40, 95% CI 1.24-4.63, p = .01). Although AKIN stage 2-3 high KDPI kidneys had comparable one-year eGFR to AKIN stage 0-1 high KDPI kidneys, there were more PNF occurrences and one-year death-censored graft survival was reduced. Given these findings, additional precautions should be undertaken when assessing and utilizing kidneys from severe AKI high KDPI donors.

Risk factors, histopathological features, and graft outcome of transplant glomerulopathy in the absence of donor-specific HLA antibodies

Transplant glomerulopathy is established as a hallmark of chronic antibody-mediated rejection in kidney transplant patients with donor-specific HLA antibodies (HLA-DSA). The clinical importance of transplant glomerulopathy in the absence of HLA-DSA is not well established. To help define this, 954 patients (encompassing 3744 biopsies) who underwent kidney transplantation 2004-2013 were studied with retrospective high-resolution HLA genotyping of both donors and recipients. The risk factors, histopathological appearance and prognosis of cases with transplant glomerulopathy in the absence of HLA-DSA were compared to those cases with HLA-DSA, and the impact of the PIRCHE-II score and eplet mismatches on development of transplant glomerulopathy evaluated. In this cohort, 10.3% developed transplant glomerulopathy, on average 3.2 years post-transplant. At the time of glomerulopathy, 23.5% had persistent pre-transplant or de novo HLA-DSA, while 76.5% were HLA-DSA negative. Only HLA-DSA was identified as a risk factor for glomerulopathy development as eplet mismatches and the PIRCHE-II score did not associate. HLA-DSA negative biopsies with glomerulopathy had less interstitial inflammation, less glomerulitis, and less C4d deposition in the peritubular capillaries compared to the HLA-DSA positive biopsies with glomerulopathy. While graft function was comparable between the two groups, HLA-DSA positive glomerulopathy was associated with a significantly higher risk of graft failure compared to HLA-DSA negative glomerulopathy (Hazard Ratio 3.84; 95% confidence interval 1.94-7.59). Landmark analysis three-years post-transplant showed that HLA-DSA negative patients with glomerulopathy still had a significant increased risk of graft failure compared to patients negative for glomerulopathy (2.62; 1.46-4.72). Thus, transplant glomerulopathy often occurs in the absence of HLA-DSA, independent of HLA molecular mismatches, and represents a different phenotype with less concomitant inflammation and better graft survival compared to that developed in the presence of HLA-DSA.

Renal tubular cell binding of β-catenin to TCF1 versus FoxO1 is associated with chronic interstitial fibrosis in transplanted kidneys

β-Catenin is an important co-factor which binds multiple transcriptional molecules and mediates fibrogenic signaling pathways. Its role in kidney transplantation is unknown. We quantified binding of β-catenin within renal tubular epithelial cells to transcription factors, TCF1 and FoxO1, using a proximity ligation assay in 240 transplanted kidneys, and evaluated their pathological and clinical outcomes. β-Catenin/FoxO1 binding in 1-month protocol biopsies inversely correlated with contemporaneous chronic fibrosis, subsequent inflammation. and inflammatory fibrosis (P < .001). The relative binding of β-catenin/TCF1 versus β-catenin/FoxO1 (TF ratio) was the optimal biomarker, and abnormal in diverse fibrotic transplant diseases. A high 1-month TF ratio was followed by greater tubular atrophy and interstitial fibrosis scores, cortical inflammation, renal impairment, and proteinuria at 1 year (n = 131, all P < .001). The TF ratio was associated with reduced eGFR (AUC 0.817), mild fibrosis (AUC 0.717), and moderate fibrosis (AUC 0.769) using receiver operating characteristic analysis. An independent validation cohort (n = 76) confirmed 1-month TF was associated with 12-month moderate fibrosis (15.8% vs. 2.6%, P = .047), however, not with other outcomes or 10-year graft survival, which limits generalizabilty of these findings. In summary, differential binding of β-catenin to TCF1 rather than FoxO1 in renal tubular cells was associated with the fibrogenic response in transplanted kidneys.

Significance of revised criteria for chronic active T cell-mediated rejection in the 2017 Banff classification: Surveillance by 1-year protocol biopsies for kidney transplantation

Diagnostic criteria for chronic active T cell-mediated rejection (CA-TCMR) were revised in the Banff 2017 consensus, but it is unknown whether the new criteria predict graft prognosis of kidney transplantation. We enrolled 406 kidney allograft recipients who underwent a 1-year protocol biopsy (PB) and investigated the diagnostic significance of Banff 2017. Interobserver reproducibility of the 3 diagnosticians showed a substantial agreement rate of 0.68 in Fleiss's kappa coefficient. Thirty-three patients (8%) were classified as CA-TCMR according to Banff 2017, and 6 were previously diagnosed as normal, 12 as acute TCMR, 10 with borderline changes, and 5 as CA-TCMR according to Banff 2015 criteria. Determinant factors of CA-TCMR were cyclosporine use (vs tacrolimus), previous acute rejection, and BK polyomavirus-associated nephropathy. In survival analysis, the new diagnosis of CA-TCMR predicted a composite graft endpoint defined as doubling serum creatinine or death-censored graft loss (log-rank test, P < .001). In multivariate analysis, CA-TCMR was associated with the second highest risk of the composite endpoint (hazard ratio: 5.42; 95% confidence interval, 2.02-14.61; P < .001 vs normal) behind antibody-mediated rejection. In conclusion, diagnosis of CA-TCMR in Banff 2017 may facilitate detecting an unfavorable prognosis of kidney allograft recipients who undergo a 1-year PB.

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.

Photoacoustic imaging of kidney fibrosis for assessing pretransplant organ quality

Roughly 10% of the world's population has chronic kidney disease (CKD). In its advanced stages, CKD greatly increases the risk of hospitalization and death. Although kidney transplantation has revolutionized the care of advanced CKD, clinicians have limited ways of assessing donor kidney quality. Thus, optimal donor kidney-recipient matching cannot be performed, meaning that some patients receive damaged kidneys that function poorly. Fibrosis is a form of chronic damage often present in donor kidneys, and it is an important predictor of future renal function. Currently, no safe, easy-to-perform technique exists that accurately quantifies renal fibrosis. We describe a potentially novel photoacoustic (PA) imaging technique that directly images collagen, the principal component of fibrotic tissue. PA imaging noninvasively quantifies whole kidney fibrotic burden in mice, and cortical fibrosis in pig and human kidneys, with outstanding accuracy and speed. Remarkably, 3-dimensional PA imaging exhibited sufficiently high resolution to capture intrarenal variations in collagen content. We further show that PA imaging can be performed in a setting that mimics human kidney transplantation, suggesting the potential for rapid clinical translation. Taken together, our data suggest that PA collagen imaging is a major advance in fibrosis quantification that could have widespread preclinical and clinical impact.

Association between transplant glomerulopathy and graft outcomes following kidney transplantation: A meta-analysis

Transplant glomerulopathy (TG), a morphological lesion associated with confluent mechanisms of endothelial injury of renal allografts, may provide a viable predictor of graft failure. This systematic literature review and meta-analysis were performed according to the PRISMA statement to examine evidence describing the association between TG and graft loss or failure and time to these events. The literature review was conducted using the Scopus, EBSCO, and Cochrane Library search engines. Hazard ratios, median survival times, and 95% confidence intervals (CIs) were estimated to evaluate graft survival in the total population and prespecified subgroups. Meta-regression analysis assessed heterogeneity. Twenty-one publications comprising 6,783 patients were eligible for data extraction and inclusion in the meta-analysis. Studies were highly heterogeneous (I² = 67.3%). The combined hazard ratio of graft loss or failure from random-effects meta-analysis was 3.11 (95% CI 2.44–3.96) in patients with TG compared with those without. Median graft survival in patients with TG was 3.25 (95% CI 0.94–11.21) years—15 years shorter than in those without TG (18.82 [95% CI 10.03–35.32] years). The effect of time from transplantation to biopsy on graft outcomes did not reach statistical significance (p = 0.116). TG was associated with a threefold increase in the risk of graft loss or failure and a 15-year loss in graft survival, indicating viability as a surrogate measure for both clinical practice and studies designed to prevent or reverse antibody-mediated rejection.

A Novel, Dose-Adjusted Tacrolimus Trough-Concentration Model for Predicting and Estimating Variance After Kidney Transplantation

Background and Objective

Given that a high intrapatient variability (IPV) of tacrolimus whole blood concentration increases the risk for a poor kidney transplant outcome, some experts advocate routine IPV monitoring for detection of high-risk patients. However, attempts to estimate the variance of tacrolimus trough concentrations (TTC) are limited by the need for patients to receive a fixed dose over time and/or the use of linear statistical models. A goal of this study is to overcome the current limitations through the novel application of statistical methodology generalizing the relationship between TTC and dose through the use of nonparametric functional regression modeling.

Methods

With TTC as a response and dose as a covariate, the model employs an unknown bivariate function, allowing for the potentially complex, nonlinear relationship between the two parameters. A dose-adjusted variance of TTC is then derived based on standard functional principal component analysis (FPCA). To assess the model, it was compared against an FPCA-based model and linear mixed-effects models using prediction error, bias, and coverage probabilities for simulated data as well as phase III data from the Astellas new drug application studies for extended-release tacrolimus.

Results

Our numerical investigation indicates that the new model better predicts dose-adjusted TTCs compared with the prediction of linear mixed effects models. Estimated coverage probabilities also indicate that the new model accurately accounts for the variance of TTC during the periods of large fluctuation in dose, whereas the linear mixed effects model consistently underestimates the coverage probabilities because of the inaccurate characterization of TTC fluctuation.

Conclusion

This is the first known application of a functional regression model to assess complex relationships between TTC and dose in a real clinical setting. This new method has applicability in future clinical trials including real-world data sets due to flexibility of the nonparametric modeling approach.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-0271-2) contains supplementary material, which is available to authorized users.

Preventive effect of early introduction of everolimus and reduced-exposure tacrolimus on renal interstitial fibrosis in de novo living-donor renal transplant recipients

BACKGROUND

To improve the long-term outcomes following renal transplantation, prevention of renal-allograft interstitial fibrosis (IF), mainly due to calcineurin inhibitors, is an important therapeutic target. Everolimus (EVR) was reported to have antifibrotic effects. We aimed to investigate the safety, efficacy, and IF of our modified immunosuppressive regimen, which includes early introduction of EVR and reduced-exposure tacrolimus (Tac) (EVR group), and compare it with the standard-exposure tacrolimus-based regimen (Tac group) in de novo living-donor renal recipients.

METHODS

In this retrospective, single-center cohort study, we compared the 2-year clinical courses between the two groups according to intention to treat. Additionally, in patients in whom biopsies were obtained at 1 h, 3 months, and 12 months post-transplant, we compared IF between the groups using imaging analysis.

RESULTS

Overall, 47 patients were included (EVR group, n = 22; Tac group, n = 25). There were no significant differences in renal function and incidences of rejection and viral infections between the groups at the 2-year post-transplant follow-up. However, pathologic imaging analysis (n = 34) revealed chronological progression of IF in the Tac group during the first year post-transplant and no changes in the EVR group (fibrosis rate at 3 months: 20.8 vs. 13.6%, p < 0.001; at 12 months: 24.7 vs. 14.7%, p < 0.001, respectively).

CONCLUSION

Our modified immunosuppressive regimen may have an antifibrotic effect on transplanted kidneys without loss of safety and efficacy.

Association of Intrapatient Variability of Tacrolimus Concentration With Early Deterioration of Chronic Histologic Lesions in Kidney Transplantation

Supplemental Digital Content is available in the text.

High intrapatient variability (IPV) of tacrolimus (Tac) is increasingly recognized as a risk factor for poor graft outcomes in kidney transplantation. The timing of onset of its impact on kidney histologic lesions has not been investigated.

Cell mediated rejection revisited: Past, current, and future directions

The Banff histopathology classification system is the gold standard for assessing the causes of kidney allograft dysfunction triggered by antibody-mediated and T-cell-mediated immune reactions, thereby providing mechanistic insight and guiding therapeutic decisions. The original Banff classification (1993) consisted of four histological categories representing cell-mediated rejection: interstitial inflammation (i), tubulitis (t), endoarteritis (v), and transplant glomerulitis (g). The revised Banff 2007 classification added total inflammation score (ti) from both scarred and unscarred areas based on evolving interpretations of interstitial infiltrates. Further reappraisal of cell-mediated interstitial inflammation led to the introduction of a new inflammation score specific for areas of interstitial fibrosis and tubular atrophy, termed i-IF/TA, in the Banff 2015 scheme, establishment of a new Banff working group on T-cell-mediated rejection (TCMR), and revised criteria of chronic active TCMR in Banff 2017 classification. These Banff scheme updates reflect the general recognition that chronic interstitial inflammation is a common denominator of poor kidney allograft outcome. However, revised theories on the pathogenic importance of interstitial infiltrates have created difficulties in interpretation of chronic tubulointerstitial inflammation, as there are currently no histological criteria to discriminate immune-mediated tissue injury from 'non-specific' injury. Evolving theories on vascular lesions, both active and chronic, have also complicated histological assessment by obscuring the distinction between antibody-mediated and T-cell-mediated tissue injury. This review provides an overview of recent ideas on interstitial inflammation and vascular lesions based on emerging concepts of T-cell-mediated rejection.

Magnetic Resonance Elastography to Assess Fibrosis in Kidney Allografts

BACKGROUND AND OBJECTIVES

Fibrosis is a major cause of kidney allograft injury. Currently, the only means of assessing allograft fibrosis is by biopsy, an invasive procedure that samples <1% of the kidney. We examined whether magnetic resonance elastography, an imaging-based measure of organ stiffness, could noninvasively estimate allograft fibrosis and predict progression of allograft dysfunction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Kidney allograft recipients >1 year post-transplant undergoing an allograft biopsy first underwent free-breathing, flow-compensated magnetic resonance elastography on a 3.0-T magnetic resonance imaging scanner. Each patient had serial eGFR measurements after the elastography scan for a follow-up period of up to 1 year. The mean stiffness value of the kidney allograft was compared with both the histopathologic Banff fibrosis score and the rate of eGFR change during the follow-up period.

RESULTS

Sixteen patients who underwent magnetic resonance elastography and biopsy were studied (mean age: 54±9 years old). Whole-kidney mean stiffness ranged between 3.5 and 7.3 kPa. Whole-kidney stiffness correlated with biopsy-derived Banff fibrosis score (Spearman rho =0.67; P<0.01). Stiffness was heterogeneously distributed within each kidney, providing a possible explanation for the lack of a stronger stiffness-fibrosis correlation. We also found negative correlations between whole-kidney stiffness and both baseline eGFR (Spearman rho =-0.65; P<0.01) and eGFR change over time (Spearman rho =-0.70; P<0.01). Irrespective of the baseline eGFR, increased kidney stiffness was associated with a greater eGFR decline (regression r2=0.48; P=0.03).

CONCLUSIONS

Given the limitations of allograft biopsy, our pilot study suggests the potential for magnetic resonance elastography as a novel noninvasive measure of whole-allograft fibrosis burden that may predict future changes in kidney function. Future studies exploring the utility and accuracy of magnetic resonance elastography are needed.

Application of Ultrasound Elastography for Chronic Allograft Dysfunction in Kidney Transplantation

Interstitial fibrosis is the main characteristic of chronic allograft dysfunction, which remains the key factor affecting long-term allograft survival after kidney transplantation. Ultrasound elastography (UE), including real-time elastography, transient elastography, and acoustic radiation force impulse, has been applied widely in breast, thyroid, and liver diseases, especially in the assessment of liver fibrosis. Recently, numerous studies have reported the efficacy of UE methods in evaluating renal allograft fibrosis. This review aims to investigate the clinical applications, limitations, and future roles of UE in current clinical practice in light of changing management paradigms. In current clinical practice, UE methods, especially transient elastographic measurement, appear to be useful for ruling out fibrosis but do not have sufficient accuracy to distinguish between various stages of allograft fibrosis. Moreover, there remain considerable issues to be solved for the application of UE in kidney transplantation. Thus, UE methods cannot replace the crucial role of renal allograft biopsy in the diagnosis and evaluation of allograft fibrosis in kidney transplantation. Perhaps UE methods could be of more importance in the long-term observation and evaluation of allograft fibrosis during follow-up.

Early introduction of oral paricalcitol in renal transplant recipients. An open-label randomized study

In stable renal transplant recipients with hyperparathyroidism, previous studies have indicated that vitamin D agonist treatment might have anti-proteinuric effects. Animal studies indicate possible anti-fibrotic and anti-inflammatory effects. Early introduction of paricalcitol in de novo renal transplant recipients might reduce proteinuria and prevent progressive allograft fibrosis. We performed a single-center, prospective, randomized, open-label trial investigating effects of paricalcitol 2 μg/day added to standard care. Participants were included 8 weeks after engraftment and followed for 44 weeks. Primary end point was change in spot urine albumin/creatinine ratio. Exploratory microarray analyses of kidney biopsies at study end investigated potential effects on gene expression. Secondary end points included change in glomerular filtration rate (GFR), pulse wave velocity (PWV), and endothelial function measured by peripheral arterial tonometry as reactive hyperemia index (RHI). Seventy-seven de novo transplanted kidney allograft recipients were included, 37 receiving paricalcitol. Paricalcitol treatment lowered PTH levels (P = 0.01) but did not significantly reduce albuminuria (P = 0.76), change vascular parameters (PWV; P = 0.98, RHI; P = 0.33), or influence GFR (P = 0.57). Allograft gene expression was not influenced. To summarize, in newly transplanted renal allograft recipients, paricalcitol reduced PTH and was well tolerated without negatively affecting kidney function. Paricalcitol did not significantly reduce/prevent albuminuria, improve parameters of vascular health, or influence allograft gene expression.

Rejection of the Renal Allograft in the Absence of Demonstrable Antibody and Complement

BACKGROUND

Recent literature has stressed the prominent role of antibodies in graft loss. This study was designed to assess a growing perception that T cell-mediated rejection (TCMR) is no longer clinically relevant.

METHODS

Five hundred forty-five renal allograft recipients over a 3-year period were screened for biopsies with: (a) TCMR including borderline change (BL), (b) negative complement protein C4 degradation fragment, and (c) absence of donor-specific antibody at time of transplant, within 30 days of the biopsy, and up to 4 measurements at later time points.

RESULTS

These stringent requirements identified 28 "pure" cases of late TCMR/BL. Low-grade glomerulitis, peritubular capillaritis, or chronic transplant glomerulopathy were found in 9/28 (32%) biopsies. Serum creatinine showed complete short-term remission in 7/10 (70%) BL and 9/18 (50%) TCMR patients 1 month postbiopsy. Yet, both treated and untreated patients demonstrated further decline in graft function as assessed by serum creatinine and estimated glomerular filtration rate.

CONCLUSIONS

Late TCMR seen in 7.9% of biopsies can contribute to significant deterioration of graft function in patients in whom the dominant contribution of antibody-mediated injury has been reasonably excluded. Our data also reinforce existing literature showing that microvascular lesions do not have absolute specificity for a diagnosis of antibody-mediated rejection.

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.

Tubulointerstitial expression and urinary excretion of connective tissue growth factor 3 months after renal transplantation predict interstitial fibrosis and tubular atrophy at 5 years in a retrospective cohort analysis

Connective tissue growth factor (CTGF) is an important mediator of renal allograft fibrosis, and urinary CTGF (CTGFu) levels correlate with the development of human allograft interstitial fibrosis. We evaluated the predictive value of CTGF protein expression in 160 kidney transplant recipients with paired protocol biopsies at 3 months and 5 years after transplantation. At month 3 and year 1, CTGFu was measured using ELISA, and biopsies were immunohistochemically stained for CTGF, with semiquantitative scoring of tubulointerstitial CTGF-positive area (CTGFti). Predictors of interstitial fibrosis and tubular atrophy (IF/TA) severity at 5 years were donor age [OR 1.05 (1.02-1.08), P = 0.001], female donor [OR 0.40 (0.18-0.90), P = 0.026], induction therapy [OR 2.76 (1.10-6.89), P = 0.030], and CTGFti >10% at month 3 [OR 2.72 (1.20-6.15), P = 0.016]. In subgroups of patients with little histologic damage at 3 months [either ci score 0 (n = 119), IF/TA score ≤1 (n = 123), or absence of IF/TA, interstitial inflammation, and tubulitis (n = 45)], consistent predictors of progression of chronic histologic damage by 5 years were donor age, induction therapy, CTGFti >10%, and CTGFu. These results suggest that, even in patients with favorable histology at 3 months, significant CTGF expression is often present which may predict accelerated accumulation of histologic damage.

Early Conversion to Prednisolone/Everolimus as an Alternative Weaning Regimen Associates With Beneficial Renal Transplant Histology and Function: The Randomized-Controlled MECANO Trial

In renal transplantation, use of calcineurin inhibitors (CNIs) is associated with nephrotoxicity and immunosuppression with malignancies and infections. This trial aimed to minimize CNI exposure and total immunosuppression while maintaining efficacy. We performed a randomized controlled, open-label multicenter trial with early cyclosporine A (CsA) elimination. Patients started with basiliximab, prednisolone (P), mycophenolate sodium (MPS), and CsA. At 6 months, immunosuppression was tapered to P/CsA, P/MPS, or P/everolimus (EVL). Primary outcomes were renal fibrosis and inflammation. Secondary outcomes were estimated glomerular filtration rate (eGFR) and incidence of rejection at 24 months. The P/MPS arm was prematurely halted. The trial continued with P/CsA (N = 89) and P/EVL (N = 96). Interstitial fibrosis and inflammation were significantly decreased and the eGFR was significantly higher in the P/EVL arm. Cumulative rejection rates were 13% (P/EVL) and 19% (P/CsA), (p = 0.08). A post hoc analysis of HLA and donor-specific antibodies at 1 year after transplantation revealed no differences. An individualized immunosuppressive strategy of early CNI elimination to dual therapy with everolimus was associated with decreased allograft fibrosis, preserved allograft function, and good efficacy, but also with more serious adverse events and discontinuation. This can be a valuable alternative regimen in patients suffering from CNI toxicity.

Novel Therapeutics Identification for Fibrosis in Renal Allograft Using Integrative Informatics Approach

Chronic allograft damage, defined by interstitial fibrosis and tubular atrophy (IF/TA), is a leading cause of allograft failure. Few effective therapeutic options are available to prevent the progression of IF/TA. We applied a meta-analysis approach on IF/TA molecular datasets in Gene Expression Omnibus to identify a robust 85-gene signature, which was used for computational drug repurposing analysis. Among the top ranked compounds predicted to be therapeutic for IF/TA were azathioprine, a drug to prevent acute rejection in renal transplantation, and kaempferol and esculetin, two drugs not previously described to have efficacy for IF/TA. We experimentally validated the anti-fibrosis effects of kaempferol and esculetin using renal tubular cells in vitro and in vivo in a mouse Unilateral Ureteric Obstruction (UUO) model. Kaempferol significantly attenuated TGF-β1-mediated profibrotic pathways in vitro and in vivo, while esculetin significantly inhibited Wnt/β-catenin pathway in vitro and in vivo. Histology confirmed significantly abrogated fibrosis by kaempferol and esculetin in vivo. We developed an integrative computational framework to identify kaempferol and esculetin as putatively novel therapies for IF/TA and provided experimental evidence for their therapeutic activities in vitro and in vivo using preclinical models. The findings suggest that both drugs might serve as therapeutic options for IF/TA.

Renal transplant immunology in the last 20 years: A revolution towards graft and patient survival improvement

To deride the hope of progress is the ultimate fatuity, the last word in poverty of spirit and meanness of mind. There is no need to be dismayed by the fact that we cannot yet envisage a definitive solution of our problems, a resting-place beyond which we need not try to go. -P.B. Medawar, 1969 * Thomas E. Starlz, also known as the Father of Clinical Transplantation, once said that organ transplantation was the supreme exception to the rule that most major advances in medicine spring from discoveries in basic science [Starzl T. The mystique of organ transplantation. J Am Coll Surg 2005 Aug;201(2):160-170]. In fact, the first successful identical-twin kidney transplantation performed by Murray's team in December 1954 (Murray J et al. Renal homotransplantations in identical twins. Surg Forum 1955;6:432-436) was the example of an upside down translation medicine: Human clinical transplantation began and researchers tried to understand the underlying immune response and how to control the powerful rejection pathways through experimental models. In the last 20 years, we have witnessed an amazing progress in the knowledge of immunological mechanisms regarding alloimmune response and an outstanding evolution on the identification and characterization of major and minor histocompatibility antigens. This review presents an historical and clinical perspective of those important advances in kidney transplantation immunology in the last 20 years, which contributed to the improvement in patients' quality of life and the survival of end-stage renal patients. In spite of these significant progresses, some areas still need substantial progress, such as the definition of non-invasive biomarkers for acute rejection; the continuous reduction of immunosuppression; the extension of graft survival, and finally the achievement of real graft tolerance extended to HLA mismatch donor: recipient pairs.

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.

Using Molecular Phenotyping to Guide Improvements in the Histologic Diagnosis of T Cell-Mediated Rejection

Recognition that some lesions typical of T cell-mediated rejection (TCMR) also occur in antibody-mediated rejection requires revision of the histologic TCMR definition. To guide this process, we assessed the relative importance of various lesions and the performance of new histology diagnostic algorithms, using molecular TCMR scores as histology-independent estimates of true TCMR. In 703 indication biopsies, random forest analysis and logistic regression indicated that interstitial infiltrate (i-lesions) and tubulitis (t-lesions) were the key histologic predictors of molecular TCMR, with arteritis (v-lesions) having less importance. Histology predicted molecular TCMR more accurately when diagnoses were assigned by strictly applying the Banff rules to the lesion scores and redefining isolated v-lesion TCMR. This improved prediction from area under the curve (AUC) 0.70 with existing rules to AUC 0.80. Further improvements were achieved by introducing more categories to reflect inflammation (AUC 0.84), by summing the lesion scores (AUC 0.85) and by logistic regression (AUC 0.90). We concluded that histologic assessment of TCMR can be improved by placing more emphasis on i- and t-lesions and incorporating new algorithms for diagnosis. Nevertheless, some discrepancies between histologic and molecular diagnoses persist, partially due to the inherent nonspecificity of i- and t-lesions, and molecular methods will be required to help resolve these cases.

Off-label use of the expensive orphan drug eculizumab in France 2009-2013 and the impact of literature: focus on the transplantation field

PURPOSE

The orphan drug eculizumab (Soliris ®) is one of the most expensive in the world and based on expenditures is classed among the highest in France, a scenario suggestive of off-label use. Given its pharmacological properties, it is likely to be used in organ transplantation. Our purposes were to describe the consumption trends of eculizumab for off-label indications overall and in the organ transplantation field and to assess the impact of publications on the latter use.

METHODS

We carried out a temporal ecological study within the French national hospitalization database (PMSI). First, the trend of eculizumab consumption (2009-2013) was compared to our estimate of the maximum on-label consumption (overall and for transplantation). Second, we evaluated the impact of the publications supporting the effectiveness of eculizumab in the transplantation field on temporal trends of eculizumab consumption.

RESULTS

Eculizumab total consumption exceeded our estimate of the maximum on-label consumption since the end of 2011 and increased until the end of the study. The off-label consumption represented at least 50 % of the total consumption. The off-label consumption in organ transplantation also increased since 2011. The amount of publications grew through the study period, but overall, the evidence level remained low. Statistically, publications were neither associated with the drug consumption for transplantation in the long term nor in the short term.

CONCLUSION

Eculizumab started being notably used for off-label indications in France since the end of 2011, and this use increased until the end of the study. We found only low-level evidence concerning the off-label use of eculizumab in the transplantation field through the studied period.

Acoustic Radiation Force Impulse Measurement in Renal Transplantation: A Prospective, Longitudinal Study With Protocol Biopsies

Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = -0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW < 3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥ 3.5 g/kg.No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values.

T-cell-mediated rejection of the kidney in the era of donor-specific antibodies: diagnostic challenges and clinical significance

PURPOSE OF REVIEW

Burgeoning literature on antibody-mediated rejection (ABMR) has led to a perception that T-cell-mediated rejection (TCMR) is no longer a significant problem. This premise needs to be carefully appraised.

RECENT FINDINGS

A review of the literature indicates that TCMR remains an independent-risk factor for graft loss. Importantly, it can occur as a sensitizing event that triggers ABMR, and adversely affects its outcome. Moreover, T cells are regularly present in lesions used to diagnose ABMR, and these lesions can also develop in the absence of donor-specific antibodies (DSA). Conversely, patients with DSA are at risk for mixed ABMR-TCMR, which is quite common in many studies, and may require a combined anti-T-cell and anti-B-cell strategy for the best outcome.

SUMMARY

T-cell-based clinical monitoring and therapy is still relevant for prophylaxis of both cellular and humoral rejection, treatment of steroid refractory TCMR, which occurs in up to 20% of patients, and optimization of clinical outcome in mixed TCMR-ABMR, which is more frequently encountered than generally appreciated, and still associated with unacceptably high rates of graft loss.

New insights in antibody-mediated rejection

PURPOSE OF REVIEW

In the present review, we aim to describe the state of knowledge concerning antibody-mediated rejection (ABMR) spectrum and diagnosis criteria before analyzing the present and future promising leads regarding ABMR prognosis markers and treatment.

RECENT FINDINGS

Recent studies regarding complement-binding donor-specific antibodies and the molecular approach highlighted the unmet need for stratification tools for prognosis and treatment inside ABMR disease.

SUMMARY

ABMR is the leading cause of kidney allograft failure. The recent expansion of its spectrum is related to the paradigm of a continuous process, leading insidiously to a chronic form of ABMR and to the progressive acknowledgement of new entities (such as vascular ABMR, subclinical ABMR, C4d-negative ABMR). Considering the global picture of ABMR, the Banff classification gradually refined the diagnosis criteria so that it now describes a clinically relevant and coherent entity. Nevertheless, if the diagnosis mainly relies on conventional assessment, such as histological findings and circulating donor-specific antibodies, these criteria face serious limitations in terms of stratification of patients at risk of graft loss inside ABMR disease. Recently, new promising tools have emerged in order to identify long-term outcomes at the time of the diagnosis of rejection. In this regard, donor-specific antibodies' complement-fixing ability and the molecular approach contributed significantly. Currently, however, no clinically relevant surrogate marker of treatment efficiency is currently available.

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.

The histology of kidney transplant failure: a long-term follow-up study

BACKGROUND

The relative impact on renal allograft outcome of specific histological diagnoses versus nonspecific chronic histological damage remains unclear.

METHODS

All 1,197 renal allograft recipients who were transplanted at a single center between 1991 and 2001 were included. All posttransplant renal allograft indication biopsies performed in this cohort during follow-up (mean, 14.5±2.80 years after transplantation) were rescored according to the current histological criteria and associated with death-censored graft outcome.

RESULTS

In this cohort, 1,365 allograft indication biopsies were performed. Specific diagnoses were present in 69.4% of graft biopsies before graft loss, but 30.6% of grafts did not have specific diagnoses in the last biopsy before graft loss. Only 14.6% of the patients did never have any specific disease diagnosed before graft loss. Extensive interstitial fibrosis and tubular atrophy without a clear cause was identified as the single cause of graft loss in only 6.9% of the cases. Acute T-cell-mediated rejection and changes suggestive of acute antibody-mediated rejection, diagnosed after the first year posttransplant, associated independently with graft survival. Transplant glomerulopathy increased over time after transplantation and represented a major risk for graft loss, as well as de novo or recurrent glomerular pathologies and polyomavirus nephropathy. Chronic histological injury associated with graft outcome, independent of specific diagnoses.

CONCLUSION

Renal allograft loss is multifactorial. Chronic histological damage and specific diseases had additive and independent impact on graft outcome. Chronic damage should be taken into account in prognostication of renal allograft outcome and could be implemented in treatment algorithms for specific diseases of kidney allografts.

Through a glass darkly: seeking clarity in preventing late kidney transplant failure

A common lament is that long-term kidney transplant outcomes remain the same despite improvements in early graft survival. To be fair, progress has been made-in both our understanding of chronic injury and modestly, graft survival. However, we are still a long way from actually solving this important and difficult problem. In this review, we outline recent data supporting the existence of several causes of renal allograft loss, the incidences of which peak at different time points after transplantation. On the basis of this broadened concept of chronic renal allograft injury, we examine the challenges of clinical trial design in long-term studies, including the use of surrogate end points and biomarkers. Finally, we suggest a path forward that, ultimately, may improve long-term renal allograft 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.

Biological pathways and potential targets for prevention and therapy of chronic allograft nephropathy

Renal transplantation (RT) is the best option for patients with end-stage renal disease, but the half-life is limited to a decade due to progressive deterioration of renal function and transplant failure from chronic allograft nephropathy (CAN), which is the leading cause of transplant loss. Extensive research has been done to understand the pathogenesis, the biological pathways of fibrogenesis, and potential therapeutic targets for the prevention and treatment of CAN. Despite the advancements in the immunosuppressive agents and patient care, CAN continues to remain an unresolved problem in renal transplantation. The aim of this paper is to undertake a comprehensive review of the literature on the pathogenesis, biological pathways of RT fibrogenesis, and potential therapeutic targets for the prevention and therapy of CAN.

Time course of pathologic changes in kidney allografts of positive crossmatch HLA-incompatible transplant recipients

BACKGROUND

Recipients of incompatible allografts are at increased risk of graft loss. We hypothesized that analysis of sequential biopsies from these grafts could define progression of graft lesions and identify features predictive of progression.

METHODS

We studied the time course of histologic injury in 745 kidney graft biopsies from 129 patients transplanted with a positive crossmatch human leukocyte antigen-incompatible kidney between 2000 and 2010 (follow-up of 1-9 years).

RESULTS

Graft survival was 98% at 1 year and 80% at 5 years after transplantation. Throughout follow-up, 70% of patients experienced rejection, with 52% showing subclinical rejection in the first year. Cell-mediated rejection was more frequent than antibody-mediated rejection throughout follow-up. Transplant glomerulopathy (TxGN; cg≥1) developed in 47% of patients over the period of the study, as early as 3 months in a few patients. TxGN was preceded by glomerulitis in more than 90% of cases, with a median time interval of 12 months. Glomerulitis and detectable posttransplantation donor-specific antibodies were risk factors for TxGN (P<0.0001 and P<0.05). C4d-negative antibody-mediated rejection manifesting as capillaritis (g≥1 and ptc≥1) with detectable donor-specific antibodies was observed in some recipients (<20%). There was progressively higher average tubulointerstitial scarring (ci+ct) from 3 to 6 to 12 months (P<0.001).

CONCLUSIONS

Despite good graft survival, a significant incidence of biopsy-proven rejection occurred in this subset of closely monitored human leukocyte antigen-incompatible recipients throughout follow-up. Microcirculation inflammation, particularly glomerulitis, irrespective of C4d, is associated with a high risk of development of TxGN at 1 year.

Transplant glomerulopathy: the interaction of HLA antibodies and endothelium

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