Artificial Urinary Biomarkers for Early Diagnosis of Acute Renal Allograft Rejection

Acute renal allograft rejection (ARAR) after kidney transplantation associated with reduced graft survival and eventual graft failure is poorly diagnosed in hospitals. Here, we report the development of Artificial bioMarker Probes (AMPros) for sensitive urinalysis of ARAR in murine models. AMPros spontaneously go to the kidneys after systemic administration, specifically react with the prodromal immune biomarkers to activate their near-infrared fluorescence signals to report cell-mediated rejection, and efficiently undergo renal excretion into urine. Thus, AMPros enable convenient optical urinalysis that detects ARAR prior to histological manifestation of rejection, which is also earlier than current diagnostic methods measuring proinflammatory cytokines and peripheral blood lymphocyte mRNAs. Due to the high kidney specificity, AMPros-based urinalysis discriminates allograft rejection against other non-alloimmune specific diseases, which is unattainable by measurement of serological biomarkers. Such a noninvasive and sensitive urine test holds great promise in continuous monitoring of renal allograft conditions at low resource settings for timely clinical interventions.

Biomarker-Development Proteomics in Kidney Transplantation: An Updated Review

Kidney transplantation (KT) is the optimal therapeutic strategy for patients with end-stage renal disease. The key to post-transplantation management is careful surveillance of allograft function. Kidney injury may occur from several different causes that require different patient management approaches. However, routine clinical monitoring has several limitations and detects alterations only at a later stage of graft damage. Accurate new noninvasive biomarker molecules are clearly needed for continuous monitoring after KT in the hope that early diagnosis of allograft dysfunction will lead to an improvement in the clinical outcome. The advent of “omics sciences”, and in particular of proteomic technologies, has revolutionized medical research. Proteomic technologies allow us to achieve the identification, quantification, and functional characterization of proteins/peptides in biological samples such as urine or blood through supervised or targeted analysis. Many studies have investigated proteomic techniques as potential molecular markers discriminating among or predicting allograft outcomes. Proteomic studies in KT have explored the whole transplant process: donor, organ procurement, preservation, and posttransplant surgery. The current article reviews the most recent findings on proteomic studies in the setting of renal transplantation in order to better understand the effective potential of this new diagnostic approach.

Urinary cell mRNA profiling of kidney allograft recipients: Development of a portable protocol for noninvasive diagnosis of T cell mediated rejection and BK virus nephropathy

BACKGROUND

We developed urinary cell mRNA profiling for noninvasive diagnosis of acute T cell mediated rejection (TCMR) and BK virus nephropathy (BKVN), two significant post-transplant complications. Our profiling protocol for the multicenter Clinical Trial of Transplantation-04 (CTOT-04) study consisted of centrifugation of urine to prepare cell pellets, washes, addition of an RNA preservative, storage at 800C and shipment in cold containers to our Gene Expression Monitoring (GEM) Core for RNA isolation and quantification of mRNA in RT-qPCR assays. To simplify profiling, we developed a filter-based protocol (ZFBP) that eliminated the need for centrifugation, RNA preservative, storage at 800C, and shipment in cold containers for mRNA profiling. Furthermore, we trained kidney allograft recipients to perform the filtration of urine at home using the filter and post the urinary cell lysate containing the RNA at ambient temperature to our GEM Core for profiling. Here, we report our refinement of ZFBP and investigation of its diagnostic performance characteristics.

METHODS

Total RNA was isolated from kidney allograft biopsy-matched urines using a filter-based protocol complemented by a silica-membrane-based cartridge for mRNA enrichment, the Weill Cornell Hybrid Protocol (WCHP). Absolute copy numbers of CD3ε mRNA, CXCL10 mRNA, and 18S rRNA, components of the CTOT-04 three-gene TCMR diagnostic signature, and urinary cell BKV VP 1 mRNA copy number were measured using RT-qPCR assays. Mann-Whitney test, Fischer exact test, and receiver operating characteristic (ROC) curve analysis were used for data analyses.

RESULTS

Urinary cell three-gene TCMR diagnostic signature scores in urines processed using the WCHP discriminated kidney allograft recipients with TCMR (12 TCMR biopsies from 11 patients) from those without TCMR or BKVN (29 No TCMR/No BKVN biopsies from 29 patients). The median (25th and 75th percentiles) score of the CTOT-04 three-gene TCMR diagnostic signature was -0.448 (-1.664, 0.204) in the TCMR group and - 2.542 (-3.267, -1.365) in the No TCMR/ No BKVN group (P = 0.0005, Mann-Whitney test). ROC curve analysis discriminated the TCMR group from the No TCMR/ No BKVN group; the area under the ROC curve (AUROC) was 0.84 (95% Confidence Intervals [CI], 0.69 to 0.98) (P < 0.001), and TCMR was diagnosed with a sensitivity of 67% (95% CI, 35 to 89) at a specificity of 86% (95% CI, 67 to 95) using the CTOT-04 validated cutpoint of -1.213 (P = 0.0016, Fisher exact test). BKV VP1 mRNA copy number in urines processed using the WCHP discriminated patients with BKVN (n = 7) from patients without TCMR or BKVN (n = 29) and the AUROC was 1.0 (95% CI, 1.00 to 1.00) (P < 0.0001) and BKVN was diagnosed with a sensitivity of 86% (95% CI, 42 to 99) at a specificity of 100% (95% CI, 85 to 100) with the previously validated cutpoint of 6.5 × 108 BKV-VP1 mRNA copies per microgram of RNA (P < 0.0001, Fisher exact test).

CONCLUSION

Urine processed using the WCHP predicted TCMR and BKVN in kidney allograft recipients. WCHP represents not only a significant advance toward the portability of urinary cell mRNA profiling but also improved patient management by minimizing their visits for urine collection.

Point-of-care non-invasive enzyme-cleavable nanosensors for acute transplant rejection detection

Accurate and non-invasive monitoring of allograft posttransplant is essential for early detection of acute cellular rejection and determines the long-term survival of the graft. Clinically, tissue biopsy is the most effective approach for diagnosing transplant rejection. Nonetheless, the procedure is invasive and potentially triggers organ failure. This work aims to design and apply GzmB-responsive nanosensors (GBRNs) that can readily size-change in graft tissues. Subsequently, we investigate the activity of serine protease granzyme B by generating a direct colorimetric urinary readout for non-invasive detection of transplant rejection in under 1 h. In preclinical heart graft mice models of transplant rejection, GBRNs were cleaved by GzmB and excreted by the kidneys via accurate nanometre-size glomerular filtration. By exploiting the catalytic activity of ultrasmall gold nanoclusters, GBRNs urinalysis promotes ultrasensitive surveillance of rejection episodes with a receiver operator characteristic curve area under the curve of 0.896 as well as a 95% confidence interval of about 0.7701-1.000. Besides, the catalytic activity of gold nanoclusters in urine can be detected at point-of-care testing to predict the immunity responses in mice with insufficient immunosuppressive therapy. Therefore, this non-invasive, sensitive, and quantitative method is a robust and informative approach for rapid and routine monitoring of transplant allografts without invasive biopsy.

Urinary cell mRNA profiling of kidney allograft recipients: A systematic investigation of a filtration based protocol for the simplification of urine processing

BACKGROUND

Kidney transplantation is a life-restorative therapy, but immune rejection undermines allograft survival. Urinary cell mRNA profiles offer a noninvasive means of diagnosing kidney allograft rejection, but urine processing protocols have logistical constraints. We aimed to determine whether the centrifugation-based method for urinary cell mRNA profiling could be replaced with a simpler filtration-based method without undermining quality.

METHODS

We isolated RNA from urine collected from kidney allograft recipients using the Cornell centrifugation-based protocol (CCBP) or the Zymo filter-based protocol (ZFBP) and compared RNA purity and yield using a spectrophotometer or a fluorometer and measured absolute copy number of transcripts using customized real-time quantitative PCR assays. We investigated the performance characteristics of RNA isolated using ZFBP and stored either at -80 °C or at ambient temperature for 2 to 4 days and also when shipped to our Gene Expression Monitoring (GEM) Core at ambient temperature. We examined the feasibility of initial processing of urine samples by kidney allograft recipients trained by the GEM Core staff and the diagnostic utility for acute rejection, of urine processed using the ZFBP.

RESULTS

RNA purity (P = 0.0007, Wilcoxon matched paired signed-ranks test) and yield (P < 0.0001) were higher with ZFBP vs. CCBP, and absolute copy number of 18S rRNA was similar (P = 0.79) following normalization of RNA yield by reverse transcribing a constant amount of RNA isolated using either protocol. RNA purity, yield, and absolute copy numbers of 18S rRNA, TGF-β1 mRNA and microRNA-26a were not different (P > 0.05) in the filtrates containing RNA stored either at -80 °C or at ambient temperature for 2 to 4 days or shipped overnight at ambient temperature. RNA purity, yield, and absolute copy numbers of 18S rRNA and TGF-β1 mRNA were also not different (P > 0.05) between home processed and laboratory processed urine filtrates. Urinary cell levels of mRNA for granzyme B (P = 0.01) and perforin (P = 0.0002) in the filtrates were diagnostic of acute rejection in human kidney allografts.

CONCLUSIONS

Urinary cell mRNA profiling was simplified using the ZFBP without undermining RNA quality or diagnostic utility. Home processing by the kidney allograft recipients, the stability of RNA containing filtrates at ambient temperature, and the elimination of the need for centrifuges and freezers represent some of the advantages of ZFBP over the CCBP for urinary cell mRNA profiling.

Meat intake and risk of mortality and graft failure in kidney transplant recipients

BACKGROUND

It is unknown whether meat intake is beneficial for long-term patient and graft survival in kidney transplant recipients (KTR).

OBJECTIVES

We first investigated the association of the previously described meat intake biomarkers 1-methylhistidine and 3-methylhistidine with intake of white and red meat as estimated from a validated food frequency questionnaire (FFQ). Second, we investigated the association of the meat intake biomarkers with long-term outcomes in KTR.

METHODS

We measured 24-h urinary excretion of 1-methylhistidine and 3-methylhistidine by validated assays in a cohort of 678 clinically stable KTR. Cross-sectional associations were assessed by linear regression. We used Cox regression analyses to prospectively study associations of log2-transformed biomarkers with mortality and graft failure.

RESULTS

Urinary 1-methylhistidine and 3-methylhistidine excretion values were median: 282; interquartile range (IQR): 132-598 µmol/24 h and median: 231; IQR: 175-306 µmol/24 h, respectively. Urinary 1-methylhistidine was associated with white meat intake [standardized β (st β): 0.20; 95% CI: 0.12, 0.28; P < 0.001], whereas urinary 3-methylhistidine was associated with red meat intake (st β: 0.30; 95% CI: 0.23, 0.38; P < 0.001). During median follow-up for 5.4 (IQR: 4.9-6.1) y, 145 (21%) died and 83 (12%) developed graft failure. Urinary 3-methylhistidine was inversely associated with mortality independently of potential confounders (HR per doubling: 0.55; 95% CI: 0.42, 0.72; P < 0.001). Both urinary 1-methylhistidine and urinary 3-methylhistidine were inversely associated with graft failure independent of potential confounders (HR per doubling: 0.84; 95% CI: 0.73, 0.96; P = 0.01; and 0.59; 95% CI: 0.41, 0.85; P = 0.004, respectively).

CONCLUSIONS

High urinary 3-methylhistidine, reflecting higher red meat intake, is independently associated with lower risk of mortality. High urinary concentrations of both 1- and 3-methylhistidine, of which the former reflects higher white meat intake, are independently associated with lower risk of graft failure in KTR. Future intervention studies are warranted to study the effect of high meat intake on mortality and graft failure in KTR, using these biomarkers.

Urinary Extracellular Vesicles Are a Novel Tool to Monitor Allograft Function in Kidney Transplantation: A Systematic Review

Extracellular vesicles (EVs) are nanoparticles that transmit molecules from releasing cells to target cells. Recent studies link urinary EVs (uEV) to diverse processes such as infection and rejection after kidney transplantation. This, and the unmet need for biomarkers diagnosing kidney transplant dysfunction, has led to the current high level of interest in uEV. uEV provide non-intrusive access to local protein, DNA, and RNA analytics without invasive biopsy. To determine the added value of uEV measurements for detecting allograft dysfunction after kidney transplantation, we systematically included all related literature containing directly relevant information, with the addition of indirect evidence regarding urine or kidney injury without transplantation. According to their varying characteristics, uEV markers after transplantation could be categorized into kidney-specific, donor-specific, and immune response-related (IR-) markers. A few convincing studies have shown that kidney-specific markers (PODXL, ion cotransporters, SYT17, NGAL, and CD133) and IR-markers (CD3, multi-mRNA signatures, and viral miRNA) could diagnose rejection, BK virus-associated nephropathy, and calcineurin inhibitor nephrotoxicity after kidney transplantation. In addition, some indirect proof regarding donor-specific markers (donor-derived cell-free DNA) in urine has been demonstrated. Together, this literature review provides directions for exploring novel uEV markers' profiling complications after kidney transplantation.

Urinary Human Epididymis Secretory Protein 4 as a Useful Biomarker for Subclinical Acute Rejection Three Months after Kidney Transplantation

Kidney transplantation is the treatment of choice for patients with advanced chronic kidney disease (CKD) and end stage renal disease (ESRD). However, acute rejection (AR) is a common complication in kidney transplantation and is associated with reduced graft survival. Current diagnosis of AR relies mainly on clinical monitoring including serum creatinine, proteinuria, and confirmation by histopathologic assessment in the biopsy specimen of graft kidney. Although an early protocol biopsy is indispensable for depicting the severity of pathologic lesions in subclinical acute rejection (subAR), it is not acceptable in some cases and cannot be performed because of its invasive nature. Therefore, we examined the detection of noninvasive biomarkers that are closely related to the pathology of subAR in protocol biopsies three months after kidney transplantation. In this study, the urinary level of microtubule-associated protein 1 light chain 3 (LC3), monocyte chemotactic protein-1 (MCP-1), liver-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL), and human epididymis secretory protein 4 (HE4) were measured three months after kidney transplantation. Urine samples of 80 patients undergoing kidney transplantation between August 2014 to September 2016, were prospectively collected after three months. SubAR was observed in 11 patients (13.8%) in protocol biopsy. The urinary levels of LC3, MCP-1, NGAL, and HE4 were significantly higher in patients with subAR than in those without, while those of L-FABP did not differ between the two groups. Multivariate regression models, receiver-operating characteristics (ROC), and areas under ROC curves (AUC) were used to identify predicted values of subAR. Urinary HE4 levels were able to better identify subAR (AUC = 0.808) than the other four urinary biomarkers. In conclusion, urinary HE4 is increased in kidney transplant recipients of subAR three months after kidney transplantation, suggesting that HE4 has the potential to be used as a novel clinical biomarker for predicting subAR.

Histopathologic Features that Predict Transplant Glomerulopathy Progression in a Chinese Cohort

BACKGROUND

Transplant glomerulopathy (TG) represents a major cause of long-term allograft failure and is the leading cause of overall post-transplant proteinuria. The extent to which histopathologic features predicts prognostication is uncertain.

METHODS

A single-center retrospective cohort with biopsy-proven TG was investigated. Renal biopsies were scored according to Banff 2017. The primary outcome was death-censored graft failure defined as return to dialysis or estimated glomerular filtration rate (eGFR) decreased to <15 mL/min/1.73 m2. The prognostic significance of clinical and histopathologic parameters was determined using Cox proportional hazards models.

RESULTS

Data from 180 cases were available for analysis with a median follow-up of 5.0 (2.6-8.2) years. In multivariable models, ci + ct score (HR 3.1; 95% CI 2.0-4.9), cg score (HR 1.7; 95% CI 1.1-2.8), eGFR (HR 2.1; 95% CI 1.4-3.2) and proteinuria (HR 2.4; 95% CI 1.6-3.7) were independent predictors of the primary outcome. Mesangial Immunoglobulin A deposition did not significantly affect allograft survival. The only significant pathologic factors for the severity of proteinuria were cg and g + ptc (adjusted R2 = 0.46) as determined by multivariable stepwise linear regression analysis.

CONCLUSIONS

Severe ci + ct and cg at biopsy were predictors of unfavorable allograft prognosis in TG patients even after taking into consideration clinical characteristics. Histologic severity of cg and g + ptc was significantly associated with clinical proteinuria.

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

INTRODUCTION

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

METHODS AND ANALYSIS

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

NCT03206801; Pre-results.

Urinary microbiome associated with chronic allograft dysfunction in kidney transplant recipients

BACKGROUND

We performed a study to identify differences in the urinary microbiome associated with chronic allograft dysfunction (CAD) and compared the urinary microbiome of male and female transplant recipients with CAD.

METHODS

This case-control study enrolled 67 patients within the Deterioration of Kidney Allograft Function (DeKAF) Genomics cohort at two transplant centers. CAD was defined as a greater than 25% rise in serum creatinine relative to a 3 month post-transplant baseline. Urine samples from patients with and without CAD were analyzed using 16S V4 bacterial ribosomal DNA sequences.

RESULTS

Corynebacterium was more prevalent in female and male patients with CAD compared to non-CAD female patients (P = 0.0005). A total 21 distinct Operational Taxonomic Unit (OTUs) were identified as significantly different when comparing CAD and non-CAD patients using Kruskal-Wallis (P < 0.01). A subset analysis of female patients with CAD compared to non-CAD females identified similar differentially abundant OTUs, including the genera Corynebacterium and Staphylococcus (Kruskal-Wallis; P = 0.01; P = 0.004, respectively). Male CAD vs female CAD analysis showed greater abundance of phylum Proteobacteria in males.

CONCLUSION

There were differences in the urinary microbiome when comparing female and male CAD patients with their female non-CAD counterparts and these differences persisted in the subset analysis limited to female patients only.

Novel urinary exosomal biomarkers of acute T cell-mediated rejection in kidney transplant recipients: A cross-sectional study

BACKGROUND

Acute rejection is hazardous to graft survival in kidney transplant recipients (KTRs). We aimed to identify novel biomarkers for early diagnosis of acute T cell-mediated rejection (TCMR) in urinary exosomes of KTRs.

METHODS

Among 458 graft biopsies enrolled in a cross-sectional multicenter study, 22 patients with stable graft function (STA) who had not shown pathologic abnormality and 25 patients who diagnosed biopsy-proven TCMR were analyzed. We performed proteomic analysis using nano-ultra performance liquid chromatography-tandem mass spectrometry (nano-UPLC-MS/MS) to identify candidate biomarkers for early TCMR diagnosis on urinary exosomes. We confirmed the protein levels of each candidate biomarker by western blot analysis.

RESULTS

A total of 169 urinary exosome proteins were identified by nano-UPLC-MS/MS. Forty-six proteins showed increased expression in STA patients, while 17 proteins were increased in TCMR patients. Among them, we selected five proteins as candidate biomarkers for early diagnosis of TCMR according to significance, degree of quantity variance, and information from the ExoCarta database. We confirmed the proteomic expression levels of five candidate biomarkers by western blot analysis in each patient. Of all candidate biomarkers, tetraspanin-1 and hemopexin were significantly higher in TCMR patients (STA:TCMR ratio = 1:1.8, P = 0.009, and 1:3.5, P = 0.046, respectively).

CONCLUSIONS

Tetraspanin-1 and hemopexin were detected in KTR urine and could act as potential diagnostic proteins for TCMR.

Identification of a urine metabolite constellation characteristic for kidney allograft rejection

INTRODUCTION

Allograft rejection is still an important complication after kidney transplantation. Currently, monitoring of these patients mostly relies on the measurement of serum creatinine and clinical evaluation. The gold standard for diagnosing allograft rejection, i.e. performing a renal biopsy is invasive and expensive. So far no adequate biomarkers are available for routine use.

OBJECTIVES

We aimed to develop a urine metabolite constellation that is characteristic for acute renal allograft rejection.

METHODS

NMR-Spectroscopy was applied to a training cohort of transplant recipients with and without acute rejection.

RESULTS

We obtained a metabolite constellation of four metabolites that shows promising performance to detect renal allograft rejection in the cohorts used (AUC of 0.72 and 0.74, respectively).

CONCLUSION

A metabolite constellation was defined with the potential for further development of an in-vitro diagnostic test that can support physicians in their clinical assessment of a kidney transplant patient.

Urinary Neutrophil Gelatinase-Associated Lipocalin Does Not Distinguish Acute Rejection from Other Causes of Acute Kidney Injury in Pediatric Renal Transplant Recipients

BACKGROUND

The aim of this prospective single center study was to investigate the ability of urinary neutrophil gelatinase-associated lipocalin (NGAL) to distinguish acute rejection from other causes of acute kidney injury (AKI) in children after renal transplantation.

METHODS

Fifteen children fulfilled the inclusion criteria (acute kidney injury (AKI) with allograft biopsy, at least 21 days after renal transplantation, no sepsis) during 2013 - 2014 in our pediatric transplantation center. The mean age was 14.8  2.8, median time after renal transplantation was 0.4 years (range 0.1 - 3.8). Urinary NGAL was measured in spot urine by Chemiluminescent Microparticle Immunoassay technology.

RESULTS

Four patients had biopsy proven acute rejection (rejection group), eleven children had AKI of other cause (non-rejection group). The median urinary NGAL concentration in the rejection group was not significantly different from NGAL in the non-rejection group (7.3 ng/mL, range 3.0 - 42.3 vs. 8.6 ng/mL, range 3.4 - 54.7, p = 0.48). There was a significant negative correlation between eGFR and urinary NGAL concentrations (r = -0.77, p < 0.001).

CONCLUSIONS

Our small study suggests that in children after renal transplantation, urinary NGAL cannot be used as a specific marker for distinguishing acute rejection from other non-rejection causes of AKI. Urinary NGAL was mainly associated with graft function but not with the etiology of AKI.

Integrated Kidney Exosome Analysis for the Detection of Kidney Transplant Rejection

Kidney transplant patients require life-long surveillance to detect allograft rejection. Repeated biopsy, albeit the clinical gold standard, is an invasive procedure with the risk of complications and comparatively high cost. Conversely, serum creatinine or urinary proteins are noninvasive alternatives but are late markers with low specificity. We report a urine-based platform to detect kidney transplant rejection. Termed iKEA (integrated kidney exosome analysis), the approach detects extracellular vesicles (EVs) released by immune cells into urine; we reasoned that T cells, attacking kidney allografts, would shed EVs, which in turn can be used as a surrogate marker for inflammation. We optimized iKEA to detect T-cell-derived EVs and implemented a portable sensing system. When applied to clinical urine samples, iKEA revealed high level of CD3-positive EVs in kidney rejection patients and achieved high detection accuracy (91.1%). Fast, noninvasive, and cost-effective, iKEA could offer new opportunities in managing transplant recipients, perhaps even in a home setting.

Both absolute and relative quantification of urinary mRNA are useful for non-invasive diagnosis of acute kidney allograft rejection

Urinary mRNA analysis with three-gene set (18S rRNA, CD3ε, and IP-10) has been suggested as a non-invasive biomarker of acute rejection (AR) in kidney transplant recipients using quantitative real-time PCR (qPCR). Application of droplet digital PCR (ddPCR), which has been suggested to provide higher sensitivity, accuracy, and absolute quantification without standard curves, could be a useful method for the quantifying low concentration of urinary mRNA. We investigated the urinary expression of these three genes in Korean patients with kidney transplantation and also evaluated the usefulness of ddPCR. 90 urine samples were collected at time of allograft biopsy in kidney recipients (n = 67) and from patients with stable renal function more than 10 years (n = 23). Absolute quantification with both PCR system showed significant higher mRNA levels of CD3ε and IP-10 in AR patients compared with stable transplants (STA), but there was no difference in 18S rRNA expression across the patient groups. To evaluate discrimination between AR and STA, ROC curve analyses of CTOT-4 formula yielded area under the curve values of 0.72 (95% CI 0.60–0.83) and 0.77 (95% CI 0.66–0.88) for qPCR and ddPCR, respectively. However, 18S normalization of absolute quantification and relative quantification with 18S showed better discrimination of AR from STA than those of the absolute method. Our data indicate that ddPCR system without standard curve would be useful to determine the absolute quantification of urinary mRNA from kidney transplant recipients. However, comparative method also could be useful and convenient in both qPCR and ddPCR analysis.

Non-invasive Detection of Acute Renal Allograft Rejection by Measurement of Vascular Endothelial Growth Factor in Urine

Urinary vascular endothelial growth factor (VEGF) was determined by enzyme-linked immunosorbent assay in 199 renal allograft recipients and 80 healthy controls. Urinary VEGF level did not change significantly during the first 8 weeks after transplantation in 119 patients with stable renal function and there were no abnormal histological findings (No-AR). In 67 patients with acute rejection, urinary VEGF was significantly higher (28.57 ± 6.21 pg/μmol creatinine) than in the No-AR patients (3.05 ± 0.45 pg/μmol creatinine) and healthy controls (2.87 ± 0.35 pg/μmol creatinine). At a cut-off point of 3.26 pg/μmol creatinine, sensitivity and specificity for diagnosis of acute rejection were 86.6 and 71.4%, respectively. The 13 patients with subclinical rejection excreted urinary VEGF (16.14 ± 4.09 pg/μmol creatinine) at a significantly higher level than No-AR patients (3.05 ± 0.45 pg/μmol creatinine). At a cut-off point of 4.69 pg/μmol creatinine, sensitivity and specificity for diagnosis of subclinical rejection were 84.6 and 79.8%, respectively. In conclusion, monitoring VEGF in urine might offer a new non-invasive way to detect acute and subclinical rejection in renal transplant recipients.

N-acetyl-beta-glucosaminidase urine activity as a marker of early proximal tubule damage and a predictor of the long-term function of the transplanted kidneys

INTRODUCTION

Ischaemia-reperfusion injury (IRI) is a factor leading to the damages of the transplanted kidney, what affects mainly the proximal tubules. Early monitoring of tubule damage can be an efficient tool to predict the allograft dysfunction. Present in proximal tubules, N-acetyl-beta-glucosaminidase (NAG) is a lysosomal enzyme whose excretion rises as a result of IRI or acute rejection. The aim of this study was to monitor the NAG urine activity to evaluate the early proximal tubule damage, and to try to predict the long-term function of the transplanted kidney.

MATERIAL AND METHODS

The study enrolled 87 Caucasian renal transplant recipients (61.7% males, 38.3% females, mean age 45.56±14.34 years). Urine samples were collected for NAG and creatinine analysis on the 1st day after transplantation, and then in the 3rd and 12th month. Protocol biopsies were performed in the 3rd and 12th month.

RESULTS

A significant positive correlation between NAG urine activity in the 3rd month after transplantation and creatinine concentration on the 14th (p=0.004) and 30th day (p=0.05), in the 3rd month (p=0.009) and after the 1st (p=0.005) and 2nd year (p=0.003) was observed. A statistically significantly higher urinary NAG activity in samples collected in the first 3 days and in the 3rd month after transplantation among patients with DGF (p=0.006 and p=0.03 respectively) was found. There was a significant positive correlation between NAG urine activity in the 3rd month and the grade of tubular atrophy in specimens collected in the 3rd (p=0.03) and 12th (p=0.04) month.

CONCLUSIONS

Monitoring of NAG urine activity is useful in the evaluation of early proximal tubule damage and predicting the long-term function of the transplanted kidneys.

Noninvasive analyses of kidney injury molecule-1 messenger RNA in kidney transplant recipients with graft dysfunction

BACKGROUND

Kidney graft fibrosis is a major factor related to chronic loss of kidney function. At present, the finding of fibrosis depends on the analysis of tissue in the renal biopsy, which has important limitations. In this study, we evaluated the messenger mRNA transcription and gene expression of kidney injury molecule-1 (KIM-1) in kidney tissue and in urinary sediment cells of kidney transplant patients with graft dysfunction aiming at the development of techniques that may allow the noninvasive diagnosis of interstitral fibrosis/tubular atrophy (IF/TA).

PATIENTS AND METHODS

RNA extracted from cells in tissue and urine of 77 renal transplant patients whose biopsies were classified according to the Banff scheme-2007. Four diagnostic groups were established: (1) acute tubular necrosis (n = 9); (2) acute rejection (n = 49); (3) acute calcineurin inhibitors nephrotoxicity (n = 10); and (4) interstitial fibrosis and tubular atrophy (IFTA, n = 29). Tissue and urine cell RNA was amplified and quantification were made by real-time polymerase chain reactron. Data from the quantification of gene expression are presented as median and 25th to 75th percentiles.

RESULTS

Messenger RNA levels of the KIM-1 gene were higher in the biopsies (26.17; 3.38-294.53) and urinary sediment cells (0.09; 0-5.81) of the patients classified as having IF/TA as compared with all others groups. A significant correlation between gene expression in samples of urine and tissue cells was found (P < .01).

CONCLUSION

These initial data suggests that KIM-1 gene mRNA quantification can be used as a noninvasive biomarker of IF/TA.

Urinary chemokines CXCL9 and CXCL10 are noninvasive markers of renal allograft rejection and BK viral infection

Renal transplant recipients require periodic surveillance for immune-based complications such as rejection and infection. Noninvasive monitoring methods are preferred, particularly for children, for whom invasive testing is problematic. We performed a cross-sectional analysis of adult and pediatric transplant recipients to determine whether a urine-based chemokine assay could noninvasively identify patients with rejection among other common clinical diagnoses. Urine was collected from 110 adults and 46 children with defined clinical conditions: healthy volunteers, stable renal transplant recipients, and recipients with clinical or subclinical acute rejection (AR) or BK infection (BKI), calcineurin inhibitor (CNI) toxicity or interstitial fibrosis (IFTA). Urine was analyzed using a solid-phase bead-array assay for the interferon gamma-induced chemokines CXCL9 and CXCL10. We found that urine CXCL9 and CXCL10 were markedly elevated in adults and children experiencing either AR or BKI (p = 0.0002), but not in stable allograft recipients or recipients with CNI toxicity or IFTA. The sensitivity and specificity of these chemokine assays exceeded that of serum creatinine. Neither chemokine distinguished between AR and BKI. These data show that urine chemokine monitoring identifies patients with renal allograft inflammation. This assay may be useful for noninvasively distinguishing those allograft recipients requiring more intensive surveillance from those with benign clinical courses.

Diagnosis of subclinical and clinical acute T-cell-mediated rejection in renal transplant patients by urinary proteome analysis

PURPOSE

Noninvasive diagnosis of acute renal allograft rejection may be advantageous compared with the allograft biopsy.

EXPERIMENTAL DESIGN

In this study, a multi-marker classification model for rejection was defined on a training set of 39 allograft patients by statistical comparison of capillary electrophoresis mass spectrometry (CE-MS) peptide spectra in urine samples from 16 cases with subclinical acute T-cell-mediated tubulointerstitial rejection and 23 nonrejection controls.

RESULTS

Application of the rejection model to a blinded validation set (n=64) resulted in an AUC value of 0.91 (95% CI: 0.82-0.97, p=0.0001). In total, 16 out of 18 subclinical and 10 out of 10 clinical rejections (BANFF grades Ia/Ib), and 28 out of 36 controls without rejection were correctly classified. Acute tubular injury in the biopsies or concomitant urinary tract infection did not interfere with CE-MS-based diagnosis. Sequence information of identified altered collagen α(I) and α (III) chain fragments in rejection samples suggested an involvement of matrix metalloproteinase-8 (MMP-8). Biopsy stainings revealed matrix metalloproteinase-8 exclusively in neutrophils located within peritubular capillaries and sparsely, in the tubulointerstitium during rejection.

CONCLUSIONS AND CLINICAL RELEVANCE

The established marker set contains peptides related to tubulointerstitial infiltration seen in acute rejection. The set of urinary peptide markers will be used for early diagnosis of acute kidney allograft rejection marker in a multicenter phase III prospective study.

Polyomavirus-infected decoy cells in cytocentrifuged urine cytology specimens from renal transplant recipients

OBJECTIVE

To evaluate the prevalence of BK virus (BKV) infection in renal transplant recipients based on the detection of urinary decoy cells.

METHODS

Fifty transplantation patients (56% males) aged 39.9 ± 11 years were screened for urinary decoy cells. The majority (86%) had received grafts from living donors. The inclusion criteria were graft dysfunction, hematuria, and/or leukocyturia. Creatinine and urea serum levels were monitored for 6 months.

RESULTS

Decoy cells were found in the urine of 12 (24%) patients 1-2 years after transplantation. The immunosuppression regimens most frequently adopted by BKV-positive patients were cyclosporine + azathiprine (50%) and FK + mycophenolate mofetyl + prednisone (25%). A renal biopsy revealed normal structures in 7 patients (58.4%), BKV nephropathy with lymphomononuclear infiltrate and fibrosis in 4 patients (33.3%), and acute cellular rejection with lymphomononuclear infiltrate without fibrosis in 1 patient (8.3%). In the latter patient, BKV-associated nephropathy was confirmed by immunohistochemistry. During the first month, creatinine and urea serum levels were higher among patients with urinary decoy cells. Creatinine levels decreased between the first and the sixth months.

CONCLUSION

The finding of BKV-associated nephropathy in 33.3% of the patients with urinary decoy cells stresses the importance of screening for BKV with urinary cytology.

The early diagnosis of acute renal graft dysfunction: a challenge we face. The role of novel biomarkers

Acute graft dysfunction can be caused by ischaemic damage or immunological injury leading to serious consequences both in the short and long term. We are in a desperate need for biomarkers of immune and nonimmune injury at different time points of the transplantation time course, beginning from a potential kidney donors where acute kidney damage can pass unnoticed, during the early post-transplant periods to predict acute transplant dysfunction due to various causes and during long term follow up to predict chronic histological changes. The implementation of these novel biomarkers could increase the sensitivity of diagnosis and monitoring of kidney injury in kidney transplant recipients. Traditionally acute graft dysfunction is diagnosed by measuring serum creatinine concentrations. Unfortunately rise in serum creatinine is a late sign of kidney damage. It indicates rather predicts the damage. The treatment, in order to be effective, must be instituted very early after the initiating insult, well before the serum creatinine even begins to rise. Fortunately, emerging technologies such as functional genomics and proteomics have uncovered novel candidates that are emerging as potentially useful biomarkers of acute kidney injury (AKI). The most promising of biomarkers in AKI for clinical use include a plasma panel consisting of Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Cystatin C and a urine panel including NGAL, Il-18 and Kidney Injury Molecule 1 (KIM-1). Most of these biomarkers were developed in non-transplant AKI, yet their role in clinical transplantation has to be identified.

Urine immunocytology as a noninvasive diagnostic tool for acute kidney rejection: a single center experience

Renal biopsy is a gold standard for establishing diagnosis of acute rejection of the renal allograft. However, being invasive, renal biopsy has potential significant complications and contraindications. Therefore, possibility to noninvasively diagnose acute rejection would improve follow-up of kidney transplant patients. The purpose of this study was to evaluate urine immunocytology for T cells as a method for noninvasive identification of patients with acute renal allograft rejection in comparison to renal biopsy. In this prospective study a cohort of 56 kidney, or kidney-pancreas transplant recipients was included. Patients either received their transplant at the University Hospital "Merkur", or have been followed at the "Merkur" Hospital. Patients were subject to either protocol or indication kidney biopsy (a total of 70 biopsies), with simultaneous urine immunocytology (determination of CD3-positive cells in the urine sediment). Acute rejection was diagnosed in 24 biopsies. 23 episodes were T-cell mediated (6 grade IA, 5 grade IB, 1 grade IIA, 1 grade III and 10 borderline), while in 1 case acute humoral rejection was diagnosed. 46 biopsies did not demonstrate acute rejection. CD3-positive cells were found in 21% of cases with acute rejection and in 13% of cases without rejection (n.s.). A finding of CD3-positive cells in urine had a sensitivity of 21% and specificity of 87% for acute rejection (including borderline), with positive predictive value of 45% and negative predictive value of 68%. Although tubulitis is a hallmark of acute T cell-mediated rejection, detection of T cells in urine sediment was insufficiently sensitive and insufficiently specific for diagnosing acute rejection in our cohort of kidney transplant recipients.

First documented case of BK nephropathy in kidney transplant recipient in Croatia: usage of urine cytology in evaluation process

BK virus associated nephropathy (BKVAN) in transplanted kidney, although recognized as a distinct entity in the 1970-es, continues to represent a challenge in kidney transplantation, mainly because the optimal treatment approach has not been determined yet. The fact that about 10-20% of patients have simultaneously some stage of acute rejection, complicate the treatment even more. Herein we present a case of BK nephropathy in the patient, one year after combined liver and kidney transplantation, complicated by episode of acute T-cell mediated rejection. Identification of decoy cells by cytology urine exam in patient with acute kidney graft function deterioration, raised suspicion of BKVAN. Diagnosis has been made by histological examination and confirmed with immunohistochemical staining for BK virus in kidney graft biopsy. One month after he had been treated for BKVAN with intravenous immunoglobulin, leflunomide and overall immunosuppression therapy reduction, there was further deterioration of graft function due to an episode of acute T-cell mediated rejection (Banff classification IA). He received 500 mg of metilprednisolon intravenously and mycophenolate mofetil had been reintroduced, which resulted in slow partial recovery of the graft function, but never to the baseline values. For the past two years his renal graft function has been stable, maintaining lower levels of immunosuppressive therapy. According to our knowledge this is the first documented case of BK virus associated nephropathy, diagnosed and confirmed with immunohistochemical staining of tissue from kidney biopsy in Croatia.

Cytometric analysis of TH1/TH2 cytokines in the urine of patients undergoing kidney transplantation

BACKGROUND

Crucial inflammatory mediators involved in development of alloimmune response leading to AR are cytokines. Our project was aimed to investigate the relation between the urine cytokine profile and the development of acute rejection (AR) episodes in patients after kidney transplantation.

MATERIAL/METHODS

The project included 44 patients undergoing kidney transplantation. During the six-month period following the transplantation AR was diagnosed in 11 patients. Urine samples were collected 2, 4, 14 and 30 days posttransplantation and cytometrically tested for concentrations of IL-2, IL-4, IL-5, IL-10, IFN-gamma and TNF-alpha.

RESULTS

We found the elevated posttransplant concentrations of IFN-gamma, IL-10 and TNF-alpha in the urine of patients with diagnosed AR vs. NONAR (P<.05). No significant differences in the urine concentrations of IL-2, IL-4, IL-5 between the two groups were observed (P>.05). Elevated concentrations of urine IFN-gamma and TNF-alpha in AR patients, not accompanied by higher concentrations of IL-2, may suggest an ongoing undetected nonspecific Th1 immune response, capable of amplifying the alloimmune response in the early phase postsurgery, leading to AR. Higher concentrations of IL-10 found in the urine of AR patients, in turn, can partially result from peripheral regulatory mechanisms controlling the ongoing immune reaction, and partially from activation of monocytes/macrophages.

CONCLUSIONS

The results of our study suggest that higher concentrations of IFN-gamma, TNF-alpha and IL-10 in the urine of patients shortly after the kidney transplantation can be considered as risk factors increasing the probability of AR episodes.

Treatment of renal transplant failure

INTRODUCTION

Among graft failures beyond months, we performed progressive reduction and complete withdrawal of immunosuppressive drugs and steroids over a period of 6 months.

PATIENTS AND METHODS

We analyzed the treatment and complications associated with all late allograft failures in 34 patients (8.19%) out of 415 patients transplanted from November 1996 to November 2006.

RESULTS

In 21 patients (61.8%), the progressive reduction of immunosuppressive treatment was effective and well tolerated; however, in 13 patients (38.2%) there was rejection of the allograft at 10.74 +/- 8.95 months (0.77-34.80) after the failure. With the reintroduction of these drugs, the rejection was controlled in seven patients, but in the other six we had to embolize the allograft, which had to be repeated in one case. Embolization was well tolerated, but in one case there was migration of one coil to the femoral artery. One patient treated with drug withdrawal experienced emphysematous pyelonephritis after repeated urinary infections, requiring a nephrectomy. Thirteen (38.2%) of the patients with late failures have been admitted for a second transplant; five of them showed HLA sensitization.

CONCLUSIONS

Conservative treatment with progressive withdrawal of immunosuppression was effective and well tolerated in two-thirds of the patients with late renal allograft failure, but one-third of the patients rejected the graft and needed allograft embolization. Infection of the graft and HLA sensitization can complicate the course of these patients.

A preliminary study on the significant value of beta-2-microglobulin over serum creatinine in renal transplant rejection and renal failure

INTRODUCTION

Beta-2-microglobulin (beta2M) is a light chain of HLA class I molecule, which is filtered by glomerulus, reabsorbed and catabolised by proximal tubule. It is one of the markers of transplant rejection. The aim of the present study was to find out the level of beta2M in acute renal failure (ARF), chronic renal failure (CRF), renal transplant rejection (TR) and renal transplantation stable (TS) cases, and correlation of beta2M with serum creatinine (SCr) in assessing renal failure.

METHODS

23 patients with ARF, 22 patients with CRF, six cases of TR, seven patients with TS, and 28 normal healthy controls were studied within a one-year period.

RESULTS

Highest mean value of beta2M was noted (12.97 +/- 3.83 microg/ml) in CRF, and all cases had elevated beta2M of which 81.8 percent of cases had beta2M above 10 microg/ml. In ARF, all cases had elevated beta2M and 78.3 percent patients had a value more than 10 microg/ml with a mean value of 11.75 +/- 2.09 microg/ml. TR cases also had elevated beta2M but 50 percent had mild elevation (less than 10 microg/ml) and 50 percent had marked elevation (more than 10 microg/ml). 42.8 percent of TS patients also had mild elevation of beta2M in the range 2.10-3.70 microg/ml. Interestingly, in normal healthy controls, 21.4 percent of patients had mild elevation of beta2M of 2.1-2.75 microg/ml, while 78.6 percent of cases had a normal range of beta2M (less than 2 microg/ml). All normal healthy controls and 71.4 percent of TS cases had normal SCr (less than 1.4 mg/dL). All cases of CRF and TR cases, and 28.6 percent of TS cases had elevated SCr. 81.8 percent of cases with CRF and 60.9 percent of cases with ARF had a marked rise of serum creatinine above 5 mg/dL.

CONCLUSION

Our study showed that beta2M is not superior over SCr for renal failure and TR cases, because it is also elevated in 21.4 percent of normal controls and 42.8 percent of TS cases. SCr is a cheaper, simpler and comparatively good test to assess renal failure and TR.

Cytometric bead array (CBA) for the measurement of cytokines in urine and plasma of patients undergoing renal rejection

Renal rejection is associated with an active immune response regulated by cytokines and in which immunocompetent cells are involved. Previous studies have measured high levels of cytokines in the urine and plasma in various renal dysfunction states. However, some methods used to measured cytokines hinder their use as a diagnostic tool in renal rejection. In this report, cytokine levels were determined in the plasma and urine of kidney transplant patients, with renal rejection and without it, using a cytometric bead array (CBA) technique. Concentrations of six human cytokines (IL-2, IL-4, IL-5, IL-10, TNF-alpha and INF-gamma) were established. Results show that patients who develop renal rejection presented high levels of IL-10 and IFN-gamma cytokines in plasma and urine compared to patients without renal rejection. The CBA technique displayed greater sensitivity in the determination of cytokines in urine than the conventional ELISA technique. Finally, when standard cytokines in plasma and in urine were compared, it was observed that, in plasma, levels of IL-4, IL-5, IL-10, TNF-alpha and IFN-gamma were detected, whereas in urine the levels detected were of IL-4, IL-5, IL-10 and IFN-gamma. These results indicate that the CBA assay is a sensitive method to measure cytokines in urine. In kidney transplant patients undergoing acute renal rejection, the presence of cytokines in urine reflects renal damage and could be a useful method in the diagnosis of renal rejection.

Postoperative hyperbilirubinemia and graft outcome in living donor liver transplantation

Little information is available on the characteristics and clinical significance of serum bilirubin level early after liver transplantation. The aim of this study was to clarify the risk factors for early graft loss and to assess the significance of postoperative hyperbilirubinemia as a predictor of graft outcome in living donor liver transplantation (LDLT). We retrospectively analyzed perioperative parameters in 68 patients who underwent LDLT. Graft loss within 1 year post-LDLT was confirmed in 9 patients (13.4%). Univariate analysis of risk factors showed that preoperative Model for End-Stage Liver Disease score, donor age, postoperative peak serum bilirubin level (p-BIL) within 28 days after LDLT, and surgical complications were significant determinants of early graft loss (<1 year post-transplant). Multivariate analysis identified p-BIL (odds ratio = 1.170, 95% confidence interval = 1.030-1.329, P = 0.016) as the only independent predictor of early graft loss. The incidence of such loss was high in patients with p-BIL over 27.0 mg/dL (area under the receiver operating characteristic curve = 0.988). In conclusion, serum bilirubin level is a useful predictor of short-term (<1 year) graft outcome and for considering retransplantation in a timely fashion.

High expression of Tim-3 mRNA in urinary cells from kidney transplant recipients with acute rejection

TIM-3 is a recently described molecule specifically expressed on Th1 differentiated T cells. We explored the usefulness of urinary mRNA profiles in the diagnosis of renal acute rejection (AR). Sixty urinary samples from renal transplant recipients simultaneously collected to allograft biopsy, (AR = 30 and No-AR =30), and 12 urinary samples from stable renal transplants were analyzed. Urinary mRNA encoding for TIM-3 and IFN-gamma were quantified using real time RT-PCR. TIM-3 mRNA was highly expressed in AR (559.19 +/- 644.41) compared to No-AR (3.78 +/- 7.20), and stable transplants (0.54 +/- 0.76), p < 0.001. To a lesser degree, IFN-gamma mRNA transcripts were also increased in AR (50.40 +/- 38.71), compared with No-AR (4.69 +/- 12.62), and stable transplants (0.38 +/- 0.44) p < 0.001. The highest expression of TIM-3 in AR makes it a promising noninvasive test for its diagnosis.

Characterization of urinary peptide biomarkers of acute rejection in renal allografts

We previously demonstrated that 4.7 kDa and 4.4 kDa peptides are useful in diagnosing acute rejection in renal transplant recipients. The aim of this study was to characterize these polypeptides and assess their potential as biomarkers. The polypeptides were identified as human beta-Defensin-1 (4.7 kDa) and alpha-1-antichymotrypsin (4.4 kDa), by tandem mass spectrometry and ProteinChip immunoassay. The urinary abundance of both polypeptides, assessed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), revealed a reduction in beta-Defensin-1 while alpha-1-antichymotrypsin increased in patients with rejection (p < 0.05) compared with clinically stable transplants. The area under the curve (AUC) for the receiver operator characteristic (ROC) curve for the diagnosis of rejection for the ratio of both peptides combined was 0.912. Longitudinal analysis confirmed a reduction in beta-Defensin-1 with a reciprocal increase in alpha-1-antichymotrypsin as rejection developed. The difference in urinary beta-Defensin-1 levels quantified by radioimmunoassay was 176.8 +/- 122.3 pg/mL in stable patients compared with 83.2 +/- 52.2 pg/mL in patients with acute rejection, with an ROC AUC of 0.749 (p < 0.01). Immunohistochemistry (IHC) confirmed reduced beta-Defensin-1 expression in the renal parenchyma of patients experiencing acute rejection. In conclusion, the ratio of beta-Defensin-1 and alpha-1-antichymotrypsin excretion in the urine is a novel, potentially useful candidate biomarkers of acute rejection.

Establishing the molecular pathways involved in chronic allograft nephropathy for testing new noninvasive diagnostic markers

BACKGROUND

Chronic allograft nephropathy (CAN) is a cause of graft loss. The multistage processes that result in CAN are poorly understood. Noninvasive assays for detecting allograft dysfunction and predicting long-term outcomes are a priority in transplantation (Tx).

METHODS

Renal tissue from kidney transplant patients (KTP) with CAN (n=11) and normal kidneys (NK; n=7) were studied using microarrays. Markers resulting from the microarray analysis (transforming growth factor [TGF]-beta, epidermal growth factor receptor [EGFR], angiotensinogen [AGT]) were tested in urine (Ur) and peripheral blood (PB) samples from the CAN patients (collected at the biopsy time) using reverse-transcriptase real-time polymerase chain reaction. Ur and PB samples from long-term KTP with stable renal function (SRF; n=20) were used as control.

RESULTS

Assuming unequal variances between CAN and NK, using a false discovery rate of 0.005, and running 1,000 of all possible permutations, 728 probe sets were differentially expressed. Genes related to fibrosis and extracellular matrix deposition (i.e., TGF-beta, laminin, gamma 2, metalloproteinases-9, and collagen type IX alpha 3) were up-regulated. Genes related to immunoglobulins, B cells, T-cell receptor, nuclear factor of activated T cells, and cytokine and chemokines receptors were also upregulated. EGFR and growth factor receptor activity (FGFR)2 were downregulated in CAN samples. AGT, EGFR, and TGF-beta levels were statistical different in urine but not in blood samples of CAN patients when compared to KTP with SRF (P<0.001, P=0.04, and P<0.001, respectively).

CONCLUSIONS

Genes related to fibrosis, extracellular matrix deposition, and immune response were found up-regulated in CAN. Markers resulting from the microarray analysis were differentially expressed in Ur samples of the CAN patients and in concordance with the microarray profiles.

Urinary cytotoxic molecular markers for a noninvasive diagnosis in acute renal transplant rejection

Perforin (P), Granzyme B (GB) and Fas-Ligand (FAS-L) are cytotoxic molecules involved in acute rejection (AR) after renal transplantation. A noninvasive diagnostic test to monitor AR and other complications could improve clinical management. We investigated the predictive and diagnostic interest of target mRNA measurements, with a quantitative PCR assay, in AR, as well as in other clinical complications recurrent in kidney transplantation. One hundred and sixty-two urine specimens from 37 allograft recipients were investigated. Clinical settings were AR, urinary tract infection (UTI), cytomegalovirus infection (CMVi) or disease (CMVd), chronic allograft nephropathy (CAN), delayed graft function (DGF) and stable graft course (controls). In the case of AR, mRNA levels of all three molecules were significantly higher than in recipients not showing any clinically evident signs of complication. Indeed, it was observed that expression levels of P, GB and Fas-L mRNA also increase in other clinical situations such as UTI, CMV and DGF. Finally, kinetic studies in three patients with AR revealed that increased P, GB and Fas-L mRNA levels could precede or were concomitant with increased serum creatinin levels. P, GB and Fas-L gene expression in urine specimens were upregulated in AR episodes but also in UTI, CMV infection and DGF. Therefore, this technique would appear to be of limited clinical value as a noninvasive method of diagnosing AR.

[Urinary cytology after renal transplantation]

BK polyomavirusnephropathy (BKN) is a serious complication of the potent immunosuppressive therapies in renal allograft recipients. BKN occurs in 5% of the patients and leads to allograft loss in approximately 50% of those affected. Early detection of BKN improves the chances to retain the allograft by allowing immediate intervention. Urine cytology is a simple, cheap and reliable method for early identification of patients at risk for BKN, together with BK DNA analysis in the serum. BK virus causes a spectrum of morphologic changes of tubular and urothelial cells that can be viewed online at http://vmic.unibas.ch/patho/seminar/index.html. These BK infected cells are called "decoy cells" as they can mimic the features of bladder carcinoma cells. In addition, certain morphologic features of the urinary sediment including tubular cells and lymphocytes can anticipate renal rejection. Historically, urinary cytology was important to screen patients with allograft for analgetic nephropathy for malignant cells, since they were at greatly increased risk of urothelial carcinoma.

Increase of proteinuria after conversion from calcineurin inhibitor to sirolimus-based treatment in kidney transplant patients with chronic allograft dysfunction

BACKGROUND

Conversion from calcineurin inhibitor to sirolimus, rapamycin has become an option in patients with chronic allograft dysfunction (CAD). However, in many cases an increase of proteinuria has been observed. The aim was to characterize the course of this so far unexplained proteinuria after conversion.

METHODS

In 149 renal transplant patients from various Spanish centres, proteinuria and renal function were analysed 6 months before until 6 months after conversion. Patients were divided into three groups according to mean proteinuria before conversion (1:<or=300 mg/day; 2:>300-3500 mg/day; 3:>3.5 g/day).

RESULTS

Generally patients showed an increase of proteinuria from 864+/-1441 (0-12125) to 1541+/-1878 (0-10976) mg/day after conversion; P<0.001. Group 1: 145+/-92 vs 669+/-868 mg/day, P<0.001; group 2: 1041+/-799 vs 1995+/-2021 mg/day, P<0.001; group 3: 6205+/-3184 vs 4859+/-2122 mg/day, P=NS. Patients with an increase of proteinuria of >500 mg/day (n=60; 40%) had a higher serum creatinine before conversion compared with patients with no or moderate increase (2.5+/-0.8 vs 2.15+/-0.72 mg/dl; P=0.002). The group that experienced an increase>500 mg/day had a higher serum creatinine after conversion compared with the patients with no or moderate increase (2.8+/-1.0 vs 2.1+/-1.2; P<0.001). Of 64 patients, 19 in group 1 showed an increase>500 mg/day.

CONCLUSION

Conversion for CAD can be associated with an increase of proteinuria in patients with pre-existing renal damage; however, it preserves renal function in patients with better creatinine and proteinuria before conversion, and might not be of benefit if advanced loss of renal function and high proteinuria are already present before conversion.

Noninvasive immune monitoring assessed by flow cytometry and real time RT-PCR in urine of renal transplantation recipients

BACKGROUND

Monitoring recipient's alloreactivity has shown to be critical for limiting overimmunosuppression besides allowing preemptive treatment of acute rejection (AR).

METHODS

Flow cytometry and real time RT-PCR were performed in urine of kidney transplant recipients with AR (n = 13) and compared with pyelonephritis (n = 10), chronic allograft nephropathy (n = 13), acute tubular necrosis (n = 13) and stable graft function (n = 11). Expression of CD3, CD4, CD8, HLA-DR, Fas-L, ICAM-1 and CD25 were assessed using flow cytometry. mRNA of perforin, granzyme B and Fas-L were quantified by real time RT-PCR.

RESULTS

Frequencies of CD3+, HLA-DR+, Fas-L+, ICAM-1+ and CD25+ cells were significantly higher in AR group (p < 0.05). ROC curves showed sensitivity from 70% to 91% and specificity from 30% to 100%, whereas the highest sensitivity and specificity was 91% and 100% respectively, for Fas-L+ cells. Levels of mRNA of perforin, granzyme B and Fas-L were significantly augmented in AR, while the sensitivity and specificity ranged from 85% to 88% and from 55% to 100%, respectively.

CONCLUSIONS

Analyses of immune activation markers by flow cytometry and real time RT-PCR are equally useful for noninvasive monitoring kidney allografts.

Urinary HLA-DR and CD54 expression--indicators for inflammatory activity in decoy cell shedding patients

BACKGROUND

Polyomavirus (PV) nephropathy may coexist with or follow acute renal transplant rejection. The aim of this study was to evaluate whether HLA-DR and CD54 are useful cellular markers for surveillance of acute rejection in PV-infected patients.

METHODS

A prospective study was conducted using 205 renal transplant patients. Urine samples were collected at a regular interval post-transplantation for routine cytology and immunocytochemistry. Urinary levels of tumour necrosis factor alpha, soluble interleukin-2 receptor and interleukin-6 were used as adjunctive markers for acute rejection.

RESULTS

Of the 699 total samples, decoy cells were identified in 100 samples of 50 patients. Patients with decoy cell-positive (DCP) samples had higher serum creatinine levels than decoy cell-negative (DCN) samples (1.55 vs 1.41 mg/dl, respectively; P = 0.006). DCP samples were also more likely to be HLA-DR positive (50.0 vs 32.4%; P = 0.029), as well as CD54 positive (17.4 vs 6.9%; P = 0.038). However, serum creatinine levels did not correlate with HLA-DR or CD54 positivity among DCP samples. Instead, CD54 positivity correlated with decoy cell grades. Immunosuppression decreased in 11 DCP patients, and HLA-DR was negatively converted in three of them. None of the patients developed acute clinical rejection. Urinary cytokine levels did not correlate with serum creatinine levels, nor did they correlate with HLA-DR or CD54 status among DCP patients.

CONCLUSIONS

Urinary tubular HLA-DR and CD54 expression increased in decoy cell shedding patients but did not indicate a concomitant acute rejection. These markers may instead indicate renal inflammatory activity associated with viral reactivation, which has the potential to progress to PV interstitial nephritis.

Proteomic research in renal transplantation

Expression proteomics is a valuable tool for biomarker discovery. Currently there is a great deal of interest in the development of urine biomarkers for detection of renal allograft rejection as an alternative to percutaneous needle biopsy, which is the "gold standard." Needle biopsy is costly and associated with significant patient morbidity and mortality. This review will discuss the author's current work in proteomics-based urine biomarker discovery, as well as alternative approaches used by other groups that use SELDI mass spectrometry. The current state of urine transplant biomarkers will be discussed, and in conclusion there will be a brief discussion of how urine biomarkers will be used for transplant patient management once they are validated and analyte-specific assays are developed.

Urinary β2-Microglobulin Is Associated With Acute Renal Allograft Rejection

BACKGROUND

Identifying urinary biomarkers associated with acute rejection (AR) of kidney allografts could improve recipient care by allowing AR to be diagnosed noninvasively and treated earlier. We attempted to identify novel biomarkers associated with AR by analyzing urinary proteins by using matrix-associated laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS).

METHODS

Using MALDI-TOF MS, we analyzed urine samples from 30 renal allograft recipients with biopsy-proven AR, 15 allograft recipients without AR, preoperative samples from 29 kidney donors, and 10 subjects with proteinuric native kidney disease.

RESULTS

In samples obtained at the time of AR, we identified a protein peak at 11.7 kd that correlated strongly with AR. In regard to its predictive power for AR, this protein peak showed sensitivity of 83.3%, specificity of 80%, positive predictive value of 89%, and negative predictive value of 70.6%, suggesting that this protein is highly associated with AR. We identified this peak as being beta2-microglobulin. This was validated by using enzyme-linked immunosorbent assay, which documented the presence of high urinary beta2-microglobulin levels in subjects with AR.

CONCLUSION

Beta2-microglobulin could be a strong biomarker for AR if used in conjunction with other biomarkers, producing an AR-specific urinary protein signature. This possibility must be confirmed in a larger cohort of kidney transplant recipients.

Prediction of renal allograft rejection by urinary protein analysis using ProteinChip Arrays (surface-enhanced laser desorption/ionization time-of-flight mass spectrometry)

OBJECTIVES

To develop a noninvasive method for the detection of renal transplant rejection using ProteinChip Arrays (surface-enhanced laser desorption/ionization time-of-flight mass spectrometry).

METHODS

A total of 23 urine samples were collected from 13 patients showing biopsy-proven renal allograft rejection and from 10 patients without histologic signs of rejection. All 23 patients had clinical symptoms and signs of acute allograft rejection and underwent renal biopsy. Samples were centrifuged, and supernatants were directly spotted onto the ProteinChip arrays with different chromatographic surfaces. The obtained spectra in a range from 2 to 200 kDa were subjected to bioinformatic analysis using the method of Fuzzy c-means, followed by the establishment of rule bases and evaluation using the relevance index according to Kiendl.

RESULTS

Several protein peaks were identified allowing differentiation between rejection and no rejection. Using two different ProteinChip surfaces, we found two biomarkers at 25.71 kDa and 28.13 kDa that gave a diagnostic sensitivity of 90% and 93% and a specificity of 80% (SAX2) and 85% (CM10), respectively.

CONCLUSIONS

Surface-enhanced laser desorption/ionization time-of-flight mass spectrometry appears to be a promising new diagnostic tool for distinguishing renal transplant patients with no rejection from those with acute rejection.

A novel biological assay to detect the active form of TGF-beta in urine to monitor renal allograft rejection

BACKGROUND

Transforming growth factor-beta (TGF-beta) plays an important role in renal fibrosis. Measurement of the concentration of the active form of TGF-beta particularly in urine may help our understanding of the mechanism of chronic allograft nephropathy and could be used as a diagnostic tool. However, TGF-beta release and activation are complex and, consequently, there is currently no accurate way to measure TGF-beta activity.

METHODS

TGF-beta-sensitive BL41 cells were stably transfected with a reporter plasmid harboring a synthetic TGF-beta-inducible DNA sequence upstream from the luciferase gene. Cells were incubated with urine samples from normal donors or transplanted recipients with or without patent nephropathy, and the active form of TGF-beta was determined as luciferase activity.

RESULTS

We have established a cell line which expresses luciferase activity in response to active TGF-beta in a dose-dependent manner. Moreover, the use of a histone deacetylase inhibitor greatly increased sensitivity to TGF-beta and also stabilized luciferase inductibility. This test is highly specific to active TGF-beta. Detectable levels of TGF-beta were found in urine from patients with renal dysfunction due to acute or chronic renal allograft rejection (P < 0.001), but not in that from patients with stable, correctly functional kidneys.

CONCLUSION

We describe a highly sensitive and specific assay for active TGF-beta. We also show that, in cases of renal allograft, TGF-beta expression is highly and significantly correlated with acute or chronic rejections.

Messenger RNA for FOXP3 in the urine of renal-allograft recipients

BACKGROUND

The outcome of renal transplantation after an episode of acute rejection is difficult to predict, even with an allograft biopsy.

METHODS

We studied urine specimens from 36 subjects with acute rejection, 18 subjects with chronic allograft nephropathy, and 29 subjects with normal biopsy results. Levels of messenger RNA (mRNA) for FOXP3, a specification and functional factor for regulatory T lymphocytes, and mRNA for CD25, CD3epsilon, perforin, and 18S ribosomal RNA (rRNA) were measured with a kinetic, quantitative polymerase-chain-reaction assay. We examined associations of mRNA levels with acute rejection, rejection reversal, and graft failure.

RESULTS

The log-transformed mean (+/-SE) ratio of FOXP3 mRNA copies to 18S ribosomal RNA copies was higher in urine from the group with acute rejection (3.8+/-0.5) than in the group with chronic allograft nephropathy (1.3+/-0.7) or the group with normal biopsy results (1.6+/-0.4) (P<0.001 by the Kruskal-Wallis test). FOXP3 mRNA levels were inversely correlated with serum creatinine levels measured at the time of biopsy in the acute-rejection group (Spearman's correlation coefficient = -0.38, P=0.02) but not in the group with chronic allograft nephropathy or the group with normal biopsy results. Analyses of receiver-operating-characteristic curves demonstrated that reversal of acute rejection can be predicted with 90 percent sensitivity and 73 percent specificity with use of the optimal identified cutoff for FOXP3 mRNA of 3.46 (P=0.001). FOXP3 mRNA levels identified subjects at risk for graft failure within six months after the incident episode of acute rejection (relative risk for the lowest third of FOXP3 mRNA levels, 6; P=0.02). None of the other mRNA levels were predictive of reversal of acute rejection or graft failure.

CONCLUSIONS

Measurement of FOXP3 mRNA in urine may offer a noninvasive means of improving the prediction of outcome of acute rejection of renal transplants.

Prediction of Acute Renal Allograft Rejection by Urinary Monokine Induced by IFN-γ (MIG)

Early diagnosis of acute allograft rejection (AR) is still decisive for long-term renal allograft survival. The aim of this study was to define the role of the chemokine monokine induced by IFN-gamma (MIG) (CXCL9) and IFN-gamma-inducible protein 10 (IP-10) (CXCL10) as early markers of AR in renal transplantation (NTX). In a prospective study, 69 de novo renal transplant recipients were monitored and urine samples were collected after NTX for a median of 29 d. In pH-adjusted urine, MIG and IP-10 were determined by modified ELISA. AR was clinically diagnosed in 15 of 69 recipients and confirmed by biopsy in 14 of 15 AR patients (Banff classification). Corresponding to CXCR3-positive infiltrates in renal tissue, urinary MIG was elevated in 14 of 15 AR patients with a median of 2809 pg/ml (quartile 25% and 75% = 870 and 13,000; n = 15), being significantly (P < 0.0001) different from both nonrejecting allograft patients (NO-AR) (median, 25%, and 75%: 96, 1.0, and 161, n = 54) and healthy controls (median, 25%, and 75%: 144, 19, and 208, n = 13). Urinary MIG predicted AR with a sensitivity of 93% and a specificity of 89%. In AR and NO-AR groups, MIG values correlated well with IP-10 (P < 0.001). MIG values indicated both imminent rejection and response to successful antirejection therapy. MIG was not related to intercurrent infections or other causes for impairment of renal function. In a multivariate analysis, MIG correlated best (P < 0.001) with AR from all AR-associated parameters. In conclusion, urinary MIG serves as a very sensitive and specific predictor for AR, mirrors response to antirejection therapy, and thus may contribute to improved long-term renal allograft survival.

Vasodilatation vs. immunotherapy to prevent delayed graft function: delayed graft function as an indication of immune activation

Delayed renal allograft function (DGF) is a factor for acute rejection and chronic allograft nephropathy. Cold ischemia time (CIT) is associated with an increased in DGF. Twenty patients receiving allografts with CIT>12 were enrolled in a double-blinded, randomized (1:1), placebo-controlled study to assess vasodilatation with fenoldopam (Abbott; dopamine-1 receptor agonist) on DGF. Fenoldopam infusion began at arterial anastomosis at 0.025 microg/kg/min and titrated to 0.1 microg/kg/min continued for 48 h postop (PO). Immunosuppression included steriods, MMF, and calcinurin inhibitors begun 36 h PO. Antibody induction (AI) using antithymocyte globulin (rabbit) (AT-G(r); Sangstat) was added halfway through the study to African-Americans and for PRA>40%. The need for dialysis, cumulative urine output (UOP), and creatinine (Cr) at PO day 7, 14, and 30 were compared. Eighteen patients completed the study drug infusion. Demographics of groups were not different. There was no difference between fenoldopam and controls for dialysis, UOP at 48 and 72 h, or Cr at 7, 14, or 30 days. There was a difference in UOP when AI (n=7) was compared to non-AI (n=11). At 48 h non-AI UOP 4796+/-3284 ml compared to AI UOP 8960+/-5130 ml (p=0.050). At 72 h, non-AI patients had UOP of 6824+/-4547 ml compared to AI patients with UOP of 12196+/-5868 ml (p=0.044). There was a trend to a lower Cr at day 7 for AI 2.7+/-2.1mg/dl compared to 4.9+/-3.0 mg/dl in non-AI (p=0.11). There was no difference in dialysis or Cr at day 14 and 30 between the AI and non-AI patients. AI with AT-G(r) significantly increases UOP in allografts with CIT>12 h, whereas vasodilatation did not. Therapy for DGF may include AT-G(r) AI.