Protocol renal allograft biopsies and the design of clinical trials aimed to prevent or treat chronic allograft nephropathy

Hydroxyproline in Urine Microvesicles as a Biomarker of Fibrosis in the Renal Transplant Patient

Background/Objectives: Interstitial fibrosis/tubular atrophy in kidney transplantation is an unspecific lesion induced by immune and non-immune factors, which determines the progression of chronic kidney disease. Hydroxyproline is an imino acid that is part of the molecule of collagen. The aim of this study was to assess hydroxyproline in urine microvesicles as a marker of fibrosis in the renal transplant patient. Patients and Methods: An observational cross-sectional study was conducted on 46 renal transplant patients who had undergone renal biopsy with diagnostic intention, as well as 19 healthy controls. Clinical, histological, and laboratory variables were collected at the time of marker determination and renal function was analyzed 2 years later. Hydroxyproline was measured in urine microvesicles. Results: Renal transplant patients showed a higher microvesicular concentration of hydroxyproline compared to the control group, with the following medians (interquartile range (IQR)): 28.024 (5.53) ng/mL vs. 2.51 (1.16) ng/mL, p < 0.001. In the transplanted patients, patients in whom biopsy showed some score of total cortical parenchymal inflammation (ti) displayed a significantly higher concentration of hydroxyproline in urine microvesicles than those patients who did not score for cortical parenchymal inflammation (29.91 ± 2.797 ng/mL vs. 22.72 ± 8.697 ng/mL, p = 0.034). No significant correlation was observed between urinary markers and serum creatinine, calcium, and parathyroid hormone (PTH). Conclusions: The concentration of hydroxyproline in urinary microvesicles increased in renal transplant patients relative to healthy controls. Hydroxyproline in urinary microvesicles is a marker of chronic renal inflammation in transplanted patients, and further studies are required to confirm this finding in other pathologies, as well as the association with fibrosis and the evolution of renal function.

Macrophage-Induced Pro-Fibrotic Gene Expression in Tubular Cells after Ischemia/Reperfusion Is Paralleled but Not Directly Mediated by C5a/C5aR1 Signaling

Ischemia/reperfusion (I/R) is inevitable during kidney transplantation and causes acute kidney injury (AKI), which affects immediate outcome and leads to chronic changes such as fibrotic remodeling of the graft. We investigated pro-fibrotic signaling after I/R, focusing on the complement component and receptor C5a/C5aR1 and macrophage/tubule crosstalk. Male Dark Agouti rats were subjected to I/R and their kidneys were harvested 10 min, 6 h, 24 h, 3 days, 5 days and 8 weeks after reperfusion. The development of renal fibrosis was assessed by the detection of Vimentin (VIM), α-smooth muscle actin (α-SMA) and collagen by immunohistochemistry and Sirius Red staining, respectively. The characterization of C5a/C5aR1 activity and C5aR1+ cells was performed by multiplex mRNA analysis, ELISA, immunofluorescence flow cytometry and in situ hybridization in animal models and cell culture analyses. In the cell culture experiments, we focused on macrophage/tubule cell crosstalk in co-culture experiments and mimicked in vivo conditions by hypoxia/reoxygenation and supplementation with C5a. Already 6-24 h after the induction of I/R in the rat model, C5a concentration in the plasma was significantly increased compared to the control. The matrix components VIM and α-SMA peaked on day 5 and declined after 8 weeks, when an increase in collagen was detected using Sirius Red. In contrast to early I/R-induced C5a activation, renal C5ar1 expression was maximal at day 5 and C5 expression increased until week 8, indicating that the renal upregulation of expression is not required for early complement activation. C5aR1 mRNA was detected in neutrophils and macrophages, but not in proximal tubular cells in the injured kidneys. The macrophage/tubular cell co-culture experiments showed that macrophages were mainly responsible for the increased expression of fibrosis-associated genes in tubule cells (ACTA2, VIM, SNAI1, TGFB1 and FGF-2), and hypoxia/reoxygenation had a partially enhancing effect. A direct pro-fibrotic effect of C5a was not observed. Increased TGF-ß levels were dependent on the differentiation of macrophages to the M2 subtype. In conclusion, the early activation of mesenchymal markers in tubular epithelial cells leads to long-term fibrotic remodeling characterized by VIM expression and driven by TGF-ß-dependent macrophage/tubular crosstalk. The chemoattractive properties of complement C5a may contribute to the recruitment of pro-fibrotic macrophages.

Banff-based histologic chronicity index is associated with graft failure but has poor interobserver reproducibility

BACKGROUND

Antibody-mediated rejection (AMR) often leads to chronic kidney allograft damage and is a critical cause of allograft failure. The Banff classification, used to diagnose AMR, has become complex and challenging for clinicians. A Banff-based histologic chronicity index (CI) was recently proposed as a simplified prognostic indicator. Its reliability and reproducibility have not been externally validated.

METHODS

This study investigated 71 kidney allograft biopsies diagnosed with AMR. Interobserver reproducibility of the recently proposed CI and its components (cg, cv, ct, and ci) were assessed. The association between CI and allograft failure was analyzed, and CI cut-off values were evaluated by Cox proportional hazards regression and Kaplan-Meier estimator with log-rank test.

RESULTS

The study confirmed the association of CI with allograft failure, but also revealed that the assessment of CI varied between pathologists, impacting its reproducibility as a prognostic tool. Only 49 (69.0%) of the biopsies showed complete agreement on the proposed cut-off value of CI < 4 or CI ≥ 4. Furthermore, this cut-off did not reliably stratify allograft failure. Notably, the cg score, which carries significant weight in the CI calculation, had the lowest agreement between observers (kappa = .281).

CONCLUSIONS

While a simplified prognostic indicator for AMR is needed, this study highlights the limitations of CI, particularly its poor interobserver reproducibility. Our findings suggest that clinicians should interpret CI cautiously and consider establishing their own cut-off values. This study underscores the need to address interobserver reproducibility before CI can be widely adopted for AMR management.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

Biopsy-Controlled Non-Invasive Quantification of Collagen Type VI in Kidney Transplant Recipients: A Post-Hoc Analysis of the MECANO Trial

The PRO-C6 assay, a reflection of collagen type VI synthesis, has been proposed as a non-invasive early biomarker of kidney fibrosis. We aimed to investigate cross-sectional and longitudinal associations between plasma and urine PRO-C6 and proven histological changes after kidney transplantation. The current study is a post-hoc analysis of 94 participants of the MECANO trial, a 24-month prospective, multicenter, open-label, randomized, controlled trial aimed at comparing everolimus-based vs. cyclosporine-based immunosuppression. PRO-C6 was measured in plasma and urine samples collected 6 and 24 months post-transplantation. Fibrosis was evaluated in biopsies collected at the same time points by Banff interstitial fibrosis/tubular atrophy (IF/TA) scoring and collagen staining (Picro Sirius Red; PSR); inflammation was evaluated by the tubulo-interstitial inflammation score (ti-score). Linear regression analyses were performed. Six-month plasma PRO-C6 was cross-sectionally associated with IF/TA score (Std. β = 0.34), and prospectively with 24-month IF/TA score and ti-score (Std. β = 0.24 and 0.23, respectively) (p < 0.05 for all). No significant associations were found between urine PRO-C6 and any of the biopsy findings. Fibrotic changes and urine PRO-C6 behaved differentially over time according to immunosuppressive therapy. These results are a first step towards non-invasive fibrosis detection after kidney transplantation by means of collagen VI synthesis measurement, and further research is required.

Usefulness of morphometric image analysis with Sirius Red to assess interstitial fibrosis after renal transplantation from uncontrolled circulatory death donors

Early interstitial fibrosis (IF) correlates with long-term renal graft dysfunction, highlighting the need for accurate quantification of IF. However, the currently used Banff classification exhibits some limitations. The aim of our study was to precisely describe the progression of IF after renal transplantation using a new morphometric image analysis method relying of Sirius Red staining. The morphometric analysis we developed showed high inter-observer and intra-observer reproducibility, with ICC [95% IC] of respectively 0.75 [0.67–0.81] (n = 151) and 0.88 [0.72–0.95] (n = 21). We used this method to assess IF (mIF) during the first year after the kidney transplantation from 66 uncontrolled donors after circulatory death (uDCD). Both mIF and interstitial fibrosis (ci) according to the Banff classification significantly increased the first three months after transplantation. From M3 to M12, mIF significantly increased whereas Banff classification failed to highlight increase of ci. Moreover, mIF at M12 (p = 0.005) correlated with mean time to graft function recovery and was significantly associated with increase of creatininemia at M12 and at last follow-up. To conclude, the new morphometric image analysis method we developed, using a routine and cheap staining, may provide valuable tool to assess IF and thus to evaluate new sources of grafts.

Kidney allograft fibrosis: what we learned from latest translational research studies

To add new molecular and pathogenetic insights into the biological machinery associated to kidney allograft fibrosis is a major research target in nephrology and organ transplant translational medicine. Interstitial fibrosis associated to tubular atrophy (IF/TA) is, in fact, an inevitable and progressive process that occurs in almost every type of chronic allograft injury (particularly in grafts from expanded criteria donors) characterized by profound remodeling and excessive production/deposition of fibrillar extracellular matrix (ECM) with a great clinical impact. IF/TA is detectable in more than 50% of kidney allografts at 2 years. However, although well studied, the complete cellular/biological network associated with IF/TA is only partially evaluated. In the last few years, then, thanks to the introduction of new biomolecular technologies, inflammation in scarred/fibrotic parenchyma areas (recently acknowledged by the BANFF classification) has been recognized as a pivotal element able to accelerate the onset and development of the allograft chronic damage. Therefore, in this review, we focused on some new pathogenetic elements involved in graft fibrosis (including epithelial/endothelial to mesenchymal transition, oxidative stress, activation of Wnt and Hedgehog signaling pathways, fatty acids oxidation and cellular senescence) that, in our opinion, could become in future good candidates as potential biomarkers and therapeutic targets.

Sequential monitoring of TIM-3 mRNA expression in blood and urine samples of renal transplant recipients

BACKGROUND

T cell immunoglobulin and mucin domain 3 (TIM-3), as a co-inhibitory receptor expressed on Th1, Th17, CD8T, FoxP3 + Treg and innate immune cells, plays an important role in suppression of T cell-mediated immune responses, tolerance induction and T cell exhaustion. In this study, we evaluated sequential alterations of TIM-3 mRNA expression level in blood and urine samples of renal transplant recipients to predict approaching clinical episodes.

METHODS

A total of 52 adult renal transplant recipients (31 male and 21 female) were enrolled in this study. All the patients received kidney transplant from living unrelated donors. TIM-3 mRNA expression in peripheral blood mononuclear cells (PBMCs) and urinary cells were quantified using Real Time TaqMan polymerase chain reaction (PCR) at 4 different time points (pre-transplantation, 2, 90 and 180 days post-transplantation).

RESULT

TIM-3 mRNA expression level on days 2, 90 and 180 after transplantation was significantly higher in blood and urine samples of patients with graft dysfunction (GD) compared with patients with well-functioning graft (WFG). Our results also showed a high correlation between blood and urinary level of TIM-3 mRNA expression. The data from Receiver Operating Characteristic (ROC) Curve Analysis showed that blood and urinary TIM-3 mRNA expression level at month 3 and 6 could discriminate graft dysfunction (GD) from well-functioning graft (WFG) with high specificity and sensitivity.

CONCLUSION

Our data suggested that serial monitoring of TIM-3 mRNA level in the blood and urine samples of renal transplant recipients could be a useful non-invasive biomarker for prediction and diagnosis of allograft dysfunction.

Non-invasive quantification of collagen turnover in renal transplant recipients

Kidney allograft failure due to chronic injury/rejection remains the main cause of graft loss in renal transplant recipients (RTR). Here, we investigated whether specific biomarkers of extracellular matrix (ECM) turnover are associated with allograft function and chronic kidney disease (CKD) stage in RTR. Seventy-eight patients who attended the University Medical Center Groningen for a routine check-up after kidney transplantation were enrolled in the study. Plasma and/or 24h-urine samples were collected and specific matrix-metalloproteinase-generated neo-epitope fragments of collagens were measured by enzyme-linked immunosorbent assay. Our results demonstrated that urinary levels of C3M, a marker for collagen type III degradation, correlated with estimated glomerular filtration rate (eGFR; r = 0.58, p<0.0001), with lower levels detected in the urine of patients with advanced CKD. In addition, plasma levels of Pro-C6, a marker for collagen type VI formation, significantly increased with disease progression and correlated with eGFR (r = -0.72, p<0.0001). Conversely, plasma C3M and urinary Pro-C6 levels showed no correlation with renal function. We identified two neo-epitope biomarkers of tissue turnover associated with ECM remodeling and fibrosis that can stratify patients by CKD stage. This is as promising first step towards non-invasive monitoring of ECM turnover in the kidneys.

Clinical and pathological analyses of interstitial fibrosis and tubular atrophy cases after kidney transplantation

AIM

We carried out a clinicopathological analysis of cases presenting with interstitial fibrosis and tubular atrophy (IF/TA) after renal transplantation in an attempt to clarify the mechanisms underlying the development and prognostic significance of IF/TA.

METHODS

IF/TA was diagnosed in 35 renal allograft biopsy specimens (BS) obtained from 35 renal transplant recipients under follow up at the Department of Transplant Surgery, Kidney Center, Toda Chuo General Hospital, between January 2014 and March 2015.

RESULTS

IF/TA was diagnosed at a median of 39.9 months after the transplantation. Among the 35 patients with IF/TA, 19 (54%) had a history of acute rejection. Among the 35 BS showing evidence of IF/TA, the IF/TA was grade I in 25, grade II in 9, and grade III in 1. Arteriosclerosis of the middle-sized arteries was observed in 30 BS (86%). We then classified the 35 BS showing evidence of IF/TA according to their overall histopathological features, as follows; IF/TA alone (6 BS; 17%), IF/TA + medullary ray injury (12 BS; 34%), and IF/TA + rejection (12 BS; 34%). Loss of the renal allograft occurred during the observation period in one of the patients (3%). Of the remaining patients with functioning grafts, deterioration of the renal allograft function after the biopsies occurred in 15 patients (43%).

CONCLUSIONS

The results of our study suggests that rejection contributes to IF/TA in 30-40% of cases, medullary ray injury in 30-40% of cases, and nonspecific injury in 20% of cases. IF/TA contributes significantly to deterioration of renal allograft function.

Mechanism of tacrolimus-induced chronic renal fibrosis following transplantation is regulated by ox-LDL and its receptor, LOX-1

Chronic renal allograft dysfunction (CRAD) is the most common cause of graft failure following renal transplantation. However, the underlying mechanisms remain to be fully elucidated. Immunosuppressants and hyperlipidemia are associated with renal fibrosis following long-term use. The present study aimed to determine the effects of tacrolimus (FK506) and lipid metabolism disorder on CRAD. In vitro and in vivo models were used for this investigation. Cells of the mouse proximal renal tubular epithelial cell strain, NRK-52E, were cultured either with oxidized low-density lipoprotein (ox-LDL), FK506, ox-LDL combined with FK506, or vehicle, respectively. Changes in cell morphology and changes in the levels of lectin-like ox-LDL receptor-1 (LOX-1), reactive oxygen species (ROS), hydrogen peroxide and fibrosis-associated genes were evaluated at 24, 48 and 72 h. In separate experiment, total of 60 Sprague-Dawley rats were divided randomly into four groups, which included a high-fat group, FK506 group, high-fat combined with FK506 group, and control group. After 2, 4 and 8 weeks, the serum lipid levels, the levels of ox-LDL, ROS, and the expression levels of transforming growth factor (TGF)-β1 and connective tissue growth factor were determined. The in vitro and in vivo models revealed that lipid metabolism disorder and FK506 caused oxidative stress and a fibrogenic response. In addition, decreased levels of LOX-1 markedly reduced the levels of TGF-β1 in the in vitro model. Taken together, FK506 and dyslipidemia were found to be associated with CRAD following transplantation.

Senescence in chronic allograft nephropathy

Despite increasing numbers of patients on dialysis, the numbers of renal transplants performed yearly have remained relatively static. During the last 50 years, there have been many advances in the pharmacology of prevention of organ rejection. However, most patients will suffer from a slow but steady decline in renal function leading to graft loss. The most common cause of long-term graft loss is chronic allograft nephropathy (CAN). Therefore, elucidating and understanding the mechanisms involved in CAN is crucial for achieving better posttransplant outcomes. It is thought that the development of epithelial to mesenchymal transition (EMT) in proximal tubules is one of the first steps towards CAN, and has been shown to be a result of cellular senescence. Cells undergoing senescence acquire a senescence associated secretory phenotype (SASP) leading to the production of interleukin-1 alpha (IL-1α), which has been implicated in several degenerative and inflammatory processes including renal disease. A central mediator in SASP activation is the production of reactive oxygen species (ROS), which are produced in response to numerous physiological and pathological stimuli. This review explores the connection between SASP and the development of EMT/CAN in an effort to suggest future directions for research leading to improved long-term graft outcomes.

Tubular atrophy in the pathogenesis of chronic kidney disease progression

The longstanding focus in chronic kidney disease (CKD) research has been on the glomerulus, which is sensible because this is where glomerular filtration occurs, and a large proportion of progressive CKD is associated with significant glomerular pathology. However, it has been known for decades that tubular atrophy is also a hallmark of CKD and that it is superior to glomerular pathology as a predictor of glomerular filtration rate decline in CKD. Nevertheless, there are vastly fewer studies that investigate the causes of tubular atrophy, and fewer still that identify potential therapeutic targets. The purpose of this review is to discuss plausible mechanisms of tubular atrophy, including tubular epithelial cell apoptosis, cell senescence, peritubular capillary rarefaction and downstream tubule ischemia, oxidative stress, atubular glomeruli, epithelial-to-mesenchymal transition, interstitial inflammation, lipotoxicity and Na(+)/H(+) exchanger-1 inactivation. Once a a better understanding of tubular atrophy (and interstitial fibrosis) pathophysiology has been obtained, it might then be possible to consider tandem glomerular and tubular therapeutic strategies, in a manner similar to cancer chemotherapy regimens, which employ multiple drugs to simultaneously target different mechanistic pathways.

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.

New computerized color image analysis for the quantification of interstitial fibrosis in renal transplantation

BACKGROUND

Chronic allograft injury, the primary cause of late allograft failure in renal transplantation, can be diagnosed early at a preclinical stage by histopathological changes such as interstitial fibrosis (IF). Currently, assessed by semiquantitative analysis in the Banff classification, IF quantification is limited by pathologist's subjective interpretation.

METHODS

We have designed algorithms dedicated to quantify IF by computerized color image analysis. This innovative and objective software automatically extracts the green areas characteristic of IF in Masson's trichrome based on color image segmentation followed by removal of nonspecific IF staining (capsula, sclerosis glomeruli and normal glomeruli, normal basement membrane) and computes an index. It also counts automatically the number of glomeruli. Sixty-seven Masson stained renal transplant biopsies at various IF stages were imaged using a digital color camera mounted on a microscope. We tested the robustness of the method against varying acquisition parameters.

RESULTS

We demonstrated that the parameters do not have an impact on this quantification and that the algorithm is able to handle biopsy color variations. The intra- and interobserver reproducibility was good (P<0.003). The kappa coefficient that was performed on another set of 90 biopsies to evaluate the concordance of our method with an expert Banff quantification was 0.68, indicating a substantial agreement. Finally, the computerized IF correlated with renal function.

CONCLUSION

This study demonstrates that computerized color image analysis is a reliable and reproducible method to evaluate renal IF in routine practice and in multi-centric studies.

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

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

Identifying biomarkers as diagnostic tools in kidney transplantation

There is a critical need for biomarkers for early diagnosis, treatment response, and surrogate end point and outcome prediction in organ transplantation, leading to a tailored and individualized treatment. Genomic and proteomic platforms have provided multiple promising new biomarkers during the last few years. However, there is still no routine application of any of these markers in clinical transplantation. This article will discuss the existing gap between biomarker discovery and clinical application in the kidney transplant setting. Approaches to implementing biomarker monitoring into clinical practice will also be discussed.

Biomarkers in renal transplantation

Identifying surrogate markers of renal allograft outcome and biomarkers of acute and chronic graft injury is a critical issue for the transplant community. Measurement of serum creatinine and biopsy remain the current gold standards for the evaluation of renal allografts. These tests have significant limitations in predicting which patients are destined for immune tolerance or immune-mediated graft loss, and aiding in the management of long-term immunosuppression. The goal of biomarkers is to diagnose rejection early, determine prognosis and tailor immunosuppressive therapy in a noninvasive, cost-effective manner. Biomarker research has focused on primary areas of kidney injury, the tubules and the cells that infiltrate them. This article reviews biomarkers currently under investigation in the setting of renal allograft transplantation.

Molecular pathways involved in loss of graft function in kidney transplant recipients

Interstitial fibrosis (IF) and tubular atrophy (TA) are integral parts of chronic allograft dysfunction and represent in the new classification a separate entity with or without the identification of a specific etiology. Loss of kidney graft function with IF/TA is one of the causes of most kidney allograft losses. Despite progress in immunosuppression, chronic allograft dysfunction remains the main clinical challenge for improving long-term graft survival. The sustained damage to the allograft does not represent a single entity but the summated effects of tissue injury from several pathogenic insults, as well as the kidney's healing response, modified by alloimmunity and immunosuppression. A major challenge in the future of kidney transplantation includes the study of chronic allograft dysfunction pathogenesis to identify early markers of disease progression, as well as potential therapeutics pathways.

Interstitial fibrosis quantification in renal transplant recipients randomized to continue cyclosporine or convert to sirolimus

Conversion from cyclosporine (CsA) to sirolimus at week 12 after kidney transplantation is associated with a significant improvement in renal function. The aim of this analysis was to investigate the effect of this conversion on interstitial fibrosis (IF), a hallmark of chronic allograft injury, in patients taking part in the CONCEPT trial. This multicenter, prospective, trial included 193 renal recipients randomized at week 12 to switch from CsA to sirolimus or to continue CsA, with mycophenolate mofetil. Routine biopsy with automated, quantified assessment of IF by a program of color segmentation was performed at 1 year in 121 patients. At 1 year, renal function was significantly improved in the conversion group as assessed by estimated GFR (MDRD) and measured GFR. Biopsy results, however, showed no between-group difference in percentage of IF. Calculated GFR at 1 year was significantly associated with the percentage of IF (p = 0.004, R(2)= 0.07). By multivariate analysis diabetic patients had more fibrosis than non-diabetic patients. In conclusion, although kidney transplant patients converted from CsA to sirolimus showed significant improvement in renal function, we found no difference of IF on 1-year biopsies.

Interstitial fibrosis and tubular atrophy in renal allograft protocol biopsies as a surrogate of graft survival

Interstitial fibrosis and tubular atrophy (IF/TA) evaluated in protocol renal allograft biopsies are associated with decreased graft survival, especially when associated with transplant vasculopathy, subclinical rejection, or transplant glomerulopathy. IF/TA evaluated in protocol biopsies has been used as a secondary efficacy variable in clinical trials, some of which have shown that the prevalence of IF/TA depends on the type of immunosuppressive treatment. These observations suggest that IF/TA may be considered a surrogate of graft survival. However, there is an important difference between a predictive and a surrogate variable. A predictive variable is associated only with the main outcome variable, whereas in case of a surrogate variable, an additional condition must be accomplished; that is, modifications of the predictive variable as a result of treatment imply changes in the main outcome variable. In a trial of cyclosporine withdrawal from a cyclosporine-sirolimus-prednisone regimen, cyclosporine discontinuation was associated with less severe chronic lesions in protocol biopsies at 3 years and also with improved graft survival at 4 years. This observation suggest that IF/TA may be a surrogate of survival. This conclusion must be confirmed in other trials before accepting IF/TA as a real surrogate of graft outcome.

Spironolactone ameliorates transplant vasculopathy in renal chronic transplant dysfunction in rats

Chronic transplant dysfunction (CTD) is the leading cause of long-term renal allograft loss and is characterized by specific histological lesions including transplant vasculopathy, interstitial fibrosis, and focal glomerulosclerosis. Increasing evidence indicates that aldosterone is a direct mediator of renal damage via the mineralocorticoid receptor (MR). The MR antagonist spironolactone is renoprotective in native chronic kidney disease, but its effects on CTD are unknown. We studied the effects of spironolactone treatment on CTD development in the Dark Agouti-to-Wistar-Furth renal allograft transplant model, by treatment with 20 mg/kg spironolactone or vehicle daily by oral gavage from 2 days before transplantation (donors and recipients) throughout the experiment (12 wk, recipients). Dark Agouti-to-Dark Agouti isografts served as negative controls. Spironolactone significantly ameliorated the development of transplant vasculopathy in allografts by reducing the number of affected intrarenal arteries. In addition, spironolactone treatment showed a trend toward reduced proteinuria and focal glomerulosclerosis, and significantly reduced glomerular macrophage influx. However, spironolactone treatment did not affect interstitial fibrosis, interstitial macrophage influx, creatinine clearance, and systolic blood pressure. We conclude that spironolactone selectively ameliorates transplant vasculopathy and glomerular lesions in renal CTD in rats. These results suggest that spironolactone may have renoprotective potential as an adjunct treatment in renal transplantation to ameliorate CTD.

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

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

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

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

Presence of FoxP3+ regulatory T Cells predicts outcome of subclinical rejection of renal allografts

Subclinical rejection (SCR) of renal allografts refers to histologic patterns of acute rejection despite stable renal function. The clinical approach to SCR is controversial; it would be helpful to identify biomarkers that could determine whether the identified cellular infiltrates were detrimental. For investigation of whether the presence of FoxP3+ regulatory T cells (Treg) could help determine the functional importance of tubulointerstitial infiltrates observed in 6-mo protocol biopsies, 37 cases of SCR were evaluated. The presence of FoxP3+ Treg discriminated harmless from injurious infiltrates, evidenced by independently predicting better graft function 2 and 3 yr after transplantation. Furthermore, the FoxP3+ Treg/CD3+ T cell ratio positively correlated with graft function at 2 yr after transplantation, suggesting that an increasing proportion of Treg within the global T cell infiltrate may facilitate renal engraftment; therefore, immunostaining for FoxP3+ Treg in patients with SCR on protocol biopsies may ultimately be useful to identify patients who may require alterations in their immunosuppressive regimens.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The utility of 1- and 3-month protocol biopsies on renal allograft function: a randomized controlled study

Identification of pathological events in the renal allograft using protocol biopsies at predetermined time intervals may yield useful information and improve outcomes. We examined the influence of decisions taken on the basis of 1- and 3-month protocol biopsies findings on 1-year renal allograft function in a prospective randomized study. Out of 102 living-donor allograft recipients, 52 were randomized to undergo protocol biopsies and 50 controls had only indicated biopsies. All acute rejection (AR) episodes (clinical and subclinical) were treated. Calcineurin inhibitor (CNI) dose adjustments were made on clinical judgment. Baseline recipient and donor characteristics, immunosuppressive drug usage, HLA matches and 2-h cyclosporine levels were similar in both groups. At 1 and 3 months, protocol biopsies revealed borderline (BL) changes in 11.5% and 14% patients, AR in 17.3% and 12% and chronic allograft nephropathy (CAN) in 3.8% and 10%. The incidence of clinically evident AR episodes was similar in the two groups, but biopsy group had lower serum creatinine at 6 months (p = 0.0003) and 1 year (p < 0.0001). The renal functions were similar in those with normal histology and BL changes. Protocol biopsies are helpful in detecting subclinical histological changes in the graft and improving short-term renal allograft function.

Protocol biopsies in renal transplantation: prognostic value of structural monitoring

The natural history of renal allograft damage has been characterized in serial protocol biopsies. The prevalence of subclinical rejection (SCR) is maximal during the first months and it is associated with the progression of interstitial fibrosis/tubular atrophy (IF/TA) and a decreased graft survival. IF/TA rapidly progress during the first months and constitutes an independent predictor of graft survival. IF/TA associated with transplant vasculopathy, SCR, or transplant glomerulopathy implies a poorer prognosis than IF/TA without additional lesions. These observations suggest that protocol biopsies could be considered a surrogate of graft survival. Preliminary data suggest that the predictive value of protocol biopsies is not inferior to acute rejection or renal function. Additionally, protocol biopsies have been employed as a secondary efficacy variable in clinical trials. This strategy has been useful to demonstrate a decrease in the progression of IF/TA in some calcineurin-free regimens. Quantification of renal damage is associated with graft survival suggesting that quantitative parameters might improve the predictive value of protocol biopsies. Validation of protocol biopsies as a surrogate of graft survival is actively pursued, as the utility of classical surrogates of graft outcome such as acute rejection has become less useful because of its decreased prevalence with actual immunosuppression.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical significance of protocol biopsy at one month posttransplantation in deceased-donor renal transplantation

BACKGROUND

Protocol biopsy was used to detect pathologic changes in recipients with stable allograft function. With our 5-year practice, we reviewed protocol biopsies performed at 1 month posttransplantation in Chinese renal transplantation to analyze the impact of pathologic changes on allograft survival and to evaluate the clinical significance of protocol biopsy.

METHODS

227 patients who received biopsy at 1 month posttransplantation during Aug 2000 to Feb 2005 with stable graft function were enrolled. Patients were divided into normal group (NM), borderline change group (BL) and subclinical rejection group (SCR) based on pathology in protocol biopsy. Their clinical data were all reviewed.

RESULTS

In the 227 patients with stable graft function, there were 173 patients (76.2%), 37 patients (16.3%) and 17 patients (7.5%) in the NM, BL, SCR group respectively. The incidence of acute rejection in the following period was significantly higher in the BL and SCR groups than that in the NM group (21.6%, 29.4% vs 7.5%, P<0.01). There was a significant difference of graft survival between the BL, SCR group and NM group (P<0.01).

CONCLUSIONS

Borderline changes and subclinical rejection detected in protocol biopsy were associated with poor allograft survival. Protocol biopsy performed at 1 month posttransplantation is of great significance and can predict graft survival.

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

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

Histologic and clinical findings in living donor allografts with long-term stable function

BACKGROUND/AIMS

Protocol biopsy is an important strategy which assesses the histological changes that can occur in the renal allograft and adversely affect its outcome. We aimed to evaluate histological changes in long-term living donor transplants.

METHODS

Elective biopsies were done for 120 live donor renal transplant recipients with well-functioning grafts and no rejection history at least 1 year or more after transplant. All patients had serum creatinine levels <2 mg/dl. The histopathological findings using the chronic allograft damage index score were correlated with different clinical and immunological parameters.

RESULTS

Chronic tubulointerstitial fibrosis was the most prevalent finding (85% of cases), mostly of mild degree. Normal biopsies were reported in only 7.5% of cases, whereas chronic cyclosporine nephrotoxicity was detected in 5.8% of biopsies. Posttransplant hypertension was significantly correlated with glomerulosclerosis, and posttransplant diabetes with glomerulosclerosis, mesangial matrix increase, tubular atrophy and interstitial fibrosis. The main risk factors associated with a high chronic allograft damage index score were DR mismatching, posttransplant diabetes and time of biopsy. All histopathological changes increased with advancing donor age and declining graft function.

CONCLUSION

Elective biopsies showed that histopathological findings do exist even with stable renal function that may pave the way for predicting long-term graft outcome.

An image analysis-based method for quantification of chronic allograft damage index parameters

Chronic allograft damage index (CADI) is a semi-quantitative histopathological score that predicts renal graft outcome. We aimed to develop an objective image analysis-based method for quantification of CADI parameters. Thirty-five kidney transplant biopsies were visually analyzed according to the original CADI criteria, and divided into normal, mildly, moderately and severely altered groups. Digital images of the same samples were then analyzed with IPLab software. Areas of inflammation and fibrosis measured using image analysis increased simultaneously with corresponding visual scores, although the difference between non-inflamed and mildly inflamed groups was not statistically significant. Area of normal tubuli decreased in the images of samples with visually mild/moderate tubular atrophy and tended to be even smaller in the group with severe tubular atrophy. Image analysis-based glomerular sclerosis score increased concurrently with increasing visual score. Mesangial matrix increase score in image analysis was greater in the samples with visually mild/moderate mesangial matrix increase score compared to those with normal glomeruli, and it was highest in the group with severe mesangial matrix increase. An image analysis-based CADI scoring of renal allograft biopsies could provide more precise data for scientific studies, and help pathologists in renal allograft biopsy scoring.

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

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

Subclinical rejection associated with chronic allograft nephropathy in protocol biopsies as a risk factor for late graft loss

Chronic allograft nephropathy (CAN) in protocol biopsies is associated with graft loss while the association between subclinical rejection (SCR) and outcome has yielded contradictory results. We analyze the predictive value of SCR and/or CAN in protocol biopsies on death-censored graft survival. Since 1988, a protocol biopsy was done during the first 6 months in stable grafts with serum creatinine <300 micromol/L and proteinuria <1 g/day. Biopsies were evaluated according to Banff criteria. Borderline changes and acute rejection were grouped as SCR. CAN was defined as presence of interstitial fibrosis and tubular atrophy. Mean follow-up was 91 +/- 46 months. Sufficient tissue was obtained in 435 transplants. Biopsies were classified as normal (n = 186), SCR (n = 74), CAN (n = 110) and SCR with CAN (n = 65). Presence of SCR with CAN was associated with old donors, percentage of panel reactive antibodies and presence of acute rejection before protocol biopsy. Cox regression analysis showed that SCR with CAN (relative risk [RR]: 1.86, 95% confidence interval [CI]: 1.11-3.12; p = 0.02) and hepatitis C virus (RR: 2.27, 95% CI: 1.38-3.75; p = 0.01) were independent predictors of graft survival. In protocol biopsies, the detrimental effect of interstitial fibrosis/tubular atrophy on long-term graft survival is modulated by SCR.

Risk factors associated with the deterioration of renal function after kidney transplantation

Renal function early after transplantation is associated with a large number of risk factors, including donor age and acute rejection. During the 1990s, donor age increased and the incidence of acute rejection decreased. Renal function between the third and sixth month improved slightly, while renal function deterioration between the third or sixth month and the 12th month improved significantly. This modification coincides with the introduction of mycophenolate mofetil and tacrolimus. The tendency for sustained renal improvement early after transplantation became more evident after the introduction of anti-calcineurin-free regimens. Studies of protocol biopsies have shown that there is an increase of glomerular volume after transplantation and that a larger glomerular volume at 4 months is associated with a better glomerular filtration rate. This adaptation mechanism is impaired in patients with chronic allograft nephropathy or in patients with high cyclosporin levels. Taken together, these data suggest that the steady improvement of renal allograft function may be partly explained by a better glomerular adaptation after transplantation because of the avoidance of the vasoconstrictive effect of anti-calcineurinic agents, and a significant decrease in the prevalence of chronic allograft nephropathy early after transplantation.

Protocol Transplant Biopsies: Are They Really Needed?

Studies suggest that surveillance or protocol biopsies that are performed during the first year after kidney transplantation may be clinically useful in identifying early acute rejection or chronic allograft nephropathy at a point when they may be amenable to treatment. Although the benefit of this approach has yet to be evaluated in large, multicenter, prospective trials, numerous studies suggest that implementation of protocol biopsies may improve long-term graft function. In particular, a number of reports suggest that detection of chronic allograft nephropathy in early protocol biopsies is predictive of subsequent graft function and loss and that early treatment may have a dramatic effect on the outcome of the graft. Protocol biopsies also have the potential to be of great value in high-risk patients, such as those with delayed graft function, by allowing for early intervention for acute rejection. Furthermore, the procedure seems to be relatively straightforward and safe. Nevertheless, paucity of data has meant that clear proof of a benefit of early treatment of subclinical rejection and chronic allograft nephropathy detected by protocol biopsy is lacking. Moreover, the optimal timing of protocol biopsies and reliable methods to quantify the histologic changes observed in biopsy specimens have yet to be determined. This review discusses the pros and cons of protocol biopsies and considers the place of this procedure in the routine treatment of kidney transplant patients.

Predicting subsequent decline in kidney allograft function from early surveillance biopsies

Identifying factors that are predictive of allograft loss might be an important step toward prolonging kidney allograft survival. In this study we sought to determine the association between histologic changes on 1-year surveillance biopsies, changes in graft function and survival. This analysis included 292 adults, recipients of kidneys from living donors (69%) or deceased donors (31%), transplanted between 1998 and 2001 and followed up for 46 +/- 14 months. The primary end point was death-censored graft loss or a >50% reduction in GFR beyond 1 year. One-year biopsies were classified as: (i) Normal (N = 87, 30%), (ii) inflammation (N = 6, 2%), (iii) fibrosis (N = 131, 45%), (iv) fibrosis and inflammation (N = 53, 18%) and (v) transplant glomerulopathy (N = 15, 5%). By multivariate Cox analysis, survival related to biopsy classification (HR = 4.2, p = 0.001), graft function (HR = 0.97, p = 0.001) and HLA mismatches (HR = 1.003, p = 0.004). Using normal histology as a reference, fibrosis and inflammation (HR = 8.5, p < 0.0001) and glomerulopathy (HR = 10, p < 0.0001) related to poorer survival but mild fibrosis alone did not. Importantly, the degree of inflammation associated with fibrosis generally did not qualify for the diagnosis of borderline rejection. In conclusion, inflammation and glomerulopathy 1 year post-transplant predict loss of graft function and graft failure independently of function and other variables.