• 120027 The Kidney Foundation of Canada
• 170009 The Kidney Foundation of Canada
• 190014 The Kidney Foundation of Canada

• biomarkers
• pediatric kidney transplantation
• subclinical rejection

• Child
• Humans
• Biomarkers/blood
• Biomarkers/urine
• Biopsy
• Creatinine/blood
• Graft Rejection/diagnosis
• Graft Rejection/blood
• Graft Survival
• Kidney Transplantation
• Observational Studies as Topic

• NIAID1K23AI139335-01A1 Eurofins Transplant Genomics Inc

• Adult
• Humans
• Kidney Transplantation/adverse effects
• Chemokine CXCL10
• Biomarkers
• Interferon-gamma
• Immunoassay
• Graft Rejection/diagnosis

• Biomarkers
• Clinical outcome
• Immunosuppression
• Infection
• Pharmacodynamics
• Rejection
• Solid organ transplantation

We investigated the clinical relevance of urinary cytokines/chemokines reflecting intrarenal immunologic micromilieu as prognostic markers and the optimal measurement timing after living donor kidney transplantation (LDKT). This prospective cohort study included 77 LDKT patients who were followed for ≥ 5 years. Patients were divided into control (n = 42) or acute rejection (AR, n = 35) group. Early AR was defined as AR occurring within 3 months. Serum and urine cytokines/chemokines were measured serially as follows: intraoperative, 8/24/72 h, 1 week, 3 months, and 1 year after LDKT. Intrarenal total leukocytes, T cells, and B cells were analyzed with immunohistochemistry followed by tissueFAXS. Urinary MCP-1 and fractalkine were also analyzed in a validation cohort. Urinary MCP-1 after one week was higher in the AR group. Urinary MCP-1, fractalkine, TNF-α, RANTES, and IL-6 after one week were significantly higher in the early AR group. Intrarenal total leukocytes and T cells were elevated in the AR group compared with the control group. Urinary fractalkine, MCP-1, and IL-10 showed positive correlation with intrarenal leukocyte infiltration. Post-KT 1 week urinary MCP-1 showed predictive value in the validation cohort. One-week post-KT urinary MCP-1 may be used as a noninvasive diagnostic marker for predicting AR after LDKT.

• ABMR
• BKV
• Biological matrix
• CMV
• CXCL-10
• Kidney transplantation
• Rejection (TCMR
• SCR)

• Acute rejection
• Biomarqueurs urinaires
• Chemokines
• Chimiokines
• Diagnostic non invasif
• Kidney transplantation
• Noninvasive diagnostic
• Rejet aigu
• Transplantation rénale
• Urinary biomarker

Non-invasive biomarkers of graft rejection are needed to optimize the management and outcomes of kidney transplant recipients. Urinary excretion of IFN-γ-related chemokine CXCL10 is clearly associated with clinical and subclinical T cell-mediated graft inflammation, but its relationship with antibody-mediated damage has not been fully addressed. Further, the variables influencing levels of urinary CXCL10 excretion are unknown.

A total of 151 kidney graft biopsies (92 surveillance and 59 indication biopsies) and 151 matched urine samples obtained before biopsy were prospectively analyzed. T cell-mediated rejection (TCMR) and antibody-mediated rejection (AbMR) were defined according to the 2017 Banff classification criteria. Urinary CXCL10 levels were measured by ELISA and corrected by urinary creatinine.

Banff scores ‘t’, ‘i’, ‘g’, and ‘ptc’ were significantly related to urinary CXCL10 levels. Multivariate analysis showed that ‘t’ (β=0.107, P=0.001) and ‘ptc’ (β=0.093, P=0.002) were significantly associated with urinary CXCL10. Donor-specific antibodies (DSAs) were related to the high excretion of urinary CXCL10 at 1 year after transplantation (odds ratio [OR] 17.817, P=0.003). Urinary CXCL10 showed good discrimination ability for AbMR (AUC-ROC 0.760, P=0.001). The third tertile of urinary CXCL10 remained significantly associated with AbMR (OR 4.577, 95% confidence interval 1.799–11.646, P=0.001) after multivariate regression analysis.

DSA was the only variable clearly related to high urinary CXCL10 levels. Urinary CXCL10 is a good non-invasive candidate biomarker of AbMR and TCMR, supplying information independent of renal function and other variables normally used to monitor kidney transplants.

Chronic antibody-mediated rejection (CAMR) is the major cause of kidney transplant failure. The molecular mechanisms underlying this event are still poorly defined and this lack of knowledge deeply influences the potential therapeutic strategies. The aim of our study was to analyze the phosphoproteome of peripheral blood mononuclear cells (PBMCs), to identify cellular signaling networks differentially activated in CAMR. Phosphoproteins isolated from PBMCs of biopsy proven CAMR, kidney transplant recipients with normal graft function and histology and healthy immunocompetent individuals, have been investigated by proteomic analysis. Phosphoproteomic results were confirmed by Western blot and PBMCs’ confocal microscopy analyses. Overall, 38 PBMCs samples were analyzed. A differential analysis of PBMCs’ phosphoproteomes revealed an increase of lactotransferrin, actin-related protein 2 (ARPC2) and calgranulin-B in antibody-mediated rejection patients, compared to controls. Increased expression of phosphorylated ARPC2 and its correlation to F-actin filaments were confirmed in CAMR patients. Our results are the first evidence of altered cytoskeleton organization in circulating immune cells of CAMR patients. The increased expression of phosphorylated ARPC2 found in the PBMCs of our patients, and its association with derangement of F-actin filaments, might suggest that proteins regulating actin dynamics in immune cells could be involved in the mechanism of CAMR of kidney grafts.

• F-actin
• actin-related protein 2
• chronic antibody-mediated rejection
• kidney transplantation
• phosphoproteome

• Adult
• Antibodies/metabolism
• Antibody-Dependent Cell Cytotoxicity
• Cytoskeletal Proteins/metabolism
• Cytoskeletal Proteins/physiology
• Cytoskeleton/metabolism
• Cytoskeleton/physiology
• Female
• Graft Rejection/immunology
• Graft Rejection/metabolism
• Graft Rejection/physiopathology
• Humans
• Kidney/pathology
• Kidney Transplantation/methods
• Leukocytes, Mononuclear/metabolism
• Male
• Middle Aged
• Phosphorylation
• Proteomics

New biomarkers of early and late graft dysfunction are needed in renal transplant to improve management of complications and prolong graft survival. A wide range of potential diagnostic and prognostic biomarkers, measured in different biological fluids (serum, plasma, urine) and in renal tissues, have been proposed for post-transplant delayed graft function (DGF), acute rejection (AR), and chronic allograft dysfunction (CAD). This review investigates old and new potential biomarkers for each of these clinical domains, seeking to underline their limits and strengths. OMICs technology has allowed identifying many candidate biomarkers, providing diagnostic and prognostic information at very early stages of pathological processes, such as AR. Donor-derived cell-free DNA (ddcfDNA) and extracellular vesicles (EVs) are further promising tools. Although most of these biomarkers still need to be validated in multiple independent cohorts and standardized, they are paving the way for substantial advances, such as the possibility of accurately predicting risk of DGF before graft is implanted, of making a “molecular” diagnosis of subclinical rejection even before histological lesions develop, or of dissecting etiology of CAD. Identification of “immunoquiescent” or even tolerant patients to guide minimization of immunosuppressive therapy is another area of active research. The parallel progress in imaging techniques, bioinformatics, and artificial intelligence (AI) is helping to fully exploit the wealth of information provided by biomarkers, leading to improved disease nosology of old entities such as transplant glomerulopathy. Prospective studies are needed to assess whether introduction of these new sets of biomarkers into clinical practice could actually reduce the need for renal biopsy, integrate traditional tools, and ultimately improve graft survival compared to current management.

• Polyomavirus associated nephropathy
• acute rejection
• biomarkers
• calcineurin-inhibitor nephrotoxicity
• chronic allograft dysfunction
• chronic rejection
• extracellular vesicles
• immunosuppression
• renal transplant

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

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

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

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

• ABHD14B/CCG1-interacting factor B
• ABPP/activity-based protein profiling
• LTF/LactotransferrinPR3
• Neurotrypsin/PRSS12
• PR3/PRTN3/myeloblastin
• Renal transplant
• Serine hydrolase
• Urine

• biomarkers
• cfDNA
• ddcfDNA
• donor derived cell free DNA
• donor-derived cell-free DNA
• kidney
• kidney transplantation
• nephrology
• renal transplantation
• transplantation

• clinical research/practice
• diagnostic techniques and imaging: positron emission tomography
• kidney transplantation/nephrology
• rejection: subclinical

In kidney transplant recipients (KTRs), BK polyomavirus (BKPyV) replication may progress to polyomavirus‐associated nephropathy (PVAN). In this retrospective study, we assessed the chemokine CXCL10 in urine and blood samples consecutively acquired from 85 KTRs who displayed different stages of BKPyV replication and eventually developed PVAN. In parallel to progression toward PVAN, CXCL10 gradually increased in blood and urine, from baseline (prior to virus replication) to BKPyV DNAuria (median increase in blood: 42.15 pg/ml, P = 0.0156), from mere DNAuria to low‐ and high‐level BKPyV DNAemia (median increase: 52.60 and 87.26 pg/ml, P = 0.0010 and P = 0.0002, respectively) and peaked with histologically confirmed PVAN (median increase: 145.00 pg/ml, P < 0.0001). CXCL10 blood and urine levels significantly differed among KTRs with respect to simultaneous presence of human cytomegalovirus (P < 0.001) as well as in relation to the clinical severity of respective BKPyV DNAemia episodes (P = 0.0195). CXCL‐10 concentrations were particularly lower in KTRs in whom BKPyV DNAemia remained without clinical evidence for PVAN, as compared to individuals who displayed high decoy cell levels, decreased renal function and/or biopsy‐proven PVAN (median blood concentration: 266.97 vs. 426.42 pg/ml, P = 0.0282). In conclusion, in KTRs CXCL10 rises in parallel to BKPyV replication and correlates with the gradual development of PVAN.

• BK virus
• CXCL10
• kidney transplantation
• nephropathy
• polyomavirus

• biomarker
• clinical trial
• kidney transplant
• subclinical rejection
• urine CXCL10

• Adult
• Biomarkers/urine
• Chemokine CXCL10/urine
• Delayed Graft Function/urine
• Female
• Graft Rejection/urine
• Health Surveys
• Humans
• Kidney Transplantation/adverse effects
• Male
• Middle Aged
• Multicenter Studies as Topic
• Predictive Value of Tests
• Randomized Controlled Trials as Topic

• 364003 CIHR
• Fonds de Recherche Québec Santé
• Institute of Nutrition, Metabolism and Diabetes
• University of Manitoba

• Antibody-mediated rejection (ABMR)
• Microarray
• Molecular diagnostics
• Molecular microscope
• Renal transplant
• T-cell-mediated rejection (TCMR)

• allograft function
• allograft rejection
• allograft survival
• biomarkers
• chemokines
• pediatric kidney transplantation

Acute kidney injury (AKI) following cardiac surgery leads to increased morbidity and mortality. Characterization and validation of early biomarkers of AKI may ultimately facilitate early therapeutic intervention. We have previously identified that elevated urinary hepcidin-25 is inversely and independently associated with the development of AKI in adult cardiac surgery patients. Hepcidin-25 is an antimicrobial peptide that sequesters iron intracellularly, and its elevation following human ischemia reperfusion injury may represent a renoprotective response to minimize renal injury.

Our goal was to validate urinary hepcidin-25 as a non-invasive biomarker in an independent cardiac surgery cohort, within the context of clinical AKI predictors.

Prospective observational cohort study.

Adult cardiac surgery program at St. Boniface Hospital, Winnipeg, Manitoba, Canada.

Adult cardiac surgery patients undergoing cardiopulmonary bypass (CPB), n = 306.

Urine hepcidin-25, measured on post-operative day (POD) 1.

A prospective, observational cohort of adult CPB patients (n = 306) was collected with serial perioperative urine samples. Urine hepcidin-25 at POD 1 was measured by competitive ELISA. Its diagnostic performance was evaluated in conjunction with clinical parameters and the Thakar clinical prediction score, using multivariate logistic regression.

Urinary hepcidin-25 is elevated following cardiac surgery in AKI and non-AKI patients. Elevated urinary hepcidin-25 concentration was inversely associated with AKI on both univariate (odds ratio [OR]: 0.61, 95% confidence interval [CI]: 0.45-0.83, P = .002) and multivariate analysis (OR: 0.67, 95% CI: 0.50-0.95, P = .02). A combined model with clinical risk factors demonstrated that baseline estimated glomerular filtration rate (eGFR), diabetes mellitus, and urinary hepcidin-25 concentration had an overall area under the curve (AUC) of 0.82 (0.75-0.88) for predicting subsequent AKI development, which was superior to clinical prediction alone as determined by the Thakar score.

(1) A single-center observational study. (2) Polyclonal antibody–based competitive ELISA.

Hepcidin-25 is inversely associated with AKI in a multivariate model when combined with eGFR and diabetes mellitus, with an overall AUC of 0.82. Notably, urinary hepcidin-25 improves on clinical AKI prediction compared to the Thakar score alone.

• AKI, biomarkers
• cardiac surgery
• iron
• ischemia reperfusion injury
• renoprotection

A literature review on immune monitoring in kidney transplantation produced dozens of research articles and a multitude of promising biomarkers, all in the quest for the much sought after - but perennially elusive - “holy grail” of kidney biomarkers able to unequivocally predict acute transplant rejection vs non-rejection. Detection methodologies and study designs were many and varied. Hence the motivation for this editorial, which espouses the notion that in today’s kidney transplantation milieu, the judicious use of disease classifiers tailored to specific patient immune risks may be more achievable and productive in the long run and confer a greater advantage for patient treatment than the pursuit of a single “omniscient” biomarker. In addition, we desire to direct attention toward greater scrutiny of biomarker publications and decisions to implement biomarkers in practice, standardization of methods in the development of biomarkers and consideration for adoption of “biomarker-driven” biopsies. We propose “biomarker-driven” biopsies as an adjunctive to and/or alternative to random surveillance (protocol) biopsies or belated indication biopsies. The discovery of a single kidney transplantation biomarker would represent a major breakthrough in kidney transplantation practice, but until that occurs - if ever it does occur, other approaches offer substantial potential for unlocking prognostic, diagnostic and therapeutic options. We conclude our editorial with suggestions and recommendations for productively incorporating current biomarkers into diagnostic algorithms and for testing future biomarkers of acute rejection in kidney transplantation.

• Acute rejection
• Banff classification
• Biomarker
• Human leukocyte antigen matching
• Immune monitoring
• Immunological risk
• Kidney transplantation
• Protocol biopsy

• Biomarkers
• Genomic
• Molecular signatures
• Proteomics
• Renal transplantation
• Transplant outcome

• Allograft rejection
• CCL2
• biomarkers
• chemokines
• kidney transplantation

• Adolescent
• Adult
• Biomarkers/urine
• Chemokine CCL2/urine
• Female
• Graft Rejection/diagnosis
• Graft Rejection/mortality
• Graft Survival
• Humans
• Kidney Transplantation
• Male
• Middle Aged
• Prognosis
• Sensitivity and Specificity
• Survival Analysis
• Young Adult

• adherence
• biomarkers
• immune competency
• pharmacogenomics
• surveillance

• Molecular diagnostics
• acute rejection
• genomics
• graft monitoring
• indicators of immune response
• organ transplantation
• personalized transplant management
• proteomics
• transcriptomics

• Biomarkers
• Disease Management
• Gene Expression Profiling/methods
• Genomics/methods
• Graft Rejection/diagnosis
• Graft Rejection/genetics
• Graft Rejection/immunology
• Graft Rejection/metabolism
• Humans
• Immunosuppression Therapy/methods
• Molecular Diagnostic Techniques
• Precision Medicine/methods
• Proteomics/methods
• Transplantation Immunology

• R01 DK083447 NIDDK NIH HHS
• R56 DK083447 NIDDK NIH HHS

Kidney transplantation (KTx) represents the best available treatment for patients with end-stage renal disease. Still, the full benefits of KTx are undermined by acute rejection (AR). The diagnosis of AR ultimately relies on transplant needle biopsy. However, such an invasive procedure is associated with a significant risk of complications and is limited by sampling error and interobserver variability. In the present review, we summarize the current literature about non-invasive approaches for the diagnosis of AR in kidney transplant recipients (KTRs), including in vivo imaging, gene-expression profiling and omics analyses of blood and urine samples. Most imaging techniques, such as contrast-enhanced ultrasound and magnetic resonance, exploit the fact that blood flow is significantly lowered in case of AR-induced inflammation. In addition, AR-associated recruitment of activated leucocytes may be detectable by 18F-fluorodeoxyglucose positron emission tomography. In parallel, urine biomarkers, including CXCL9/CXCL10 or a three-gene signature of CD3ε, CXCL10 and 18S RNA levels, have been identified. None of these approaches has yet been adopted in the clinical follow-up of KTRs, but standardization of analysis procedures may help assess reproducibility and comparative diagnostic yield in large, prospective, multicentre trials.

• acute rejection
• biomarkers
• gene expression
• kidney biopsy
• proteomics

Kidney transplantation (KTx) represents the best available treatment for patients with end-stage renal disease. Still, full benefits of KTx are undermined by acute rejection (AR). The diagnosis of AR ultimately relies on transplant needle biopsy. However, such an invasive procedure is associated with a significant risk of complications and is limited by sampling error and interobserver variability. In the present review, we summarize the current literature about non-invasive approaches for the diagnosis of AR in kidney transplant recipients (KTRs), including in vivo imaging, gene expression profiling and omics analyses of blood and urine samples. Most imaging techniques, like contrast-enhanced ultrasound and magnetic resonance, exploit the fact that blood flow is significantly lowered in case of AR-induced inflammation. In addition, AR-associated recruitment of activated leukocytes may be detectable by ¹⁸F-fluoro-deoxy-glucose positron emission tomography. In parallel, urine biomarkers, including CXCL9/CXCL10 or a three-gene signature of CD3ε, IP-10 and 18S RNA levels, have been identified. None of these approaches has been adopted yet in the clinical follow-up of KTRs, but standardization of procedures may help assess reproducibility and compare diagnostic yields in large prospective multicentric trials.

• 18FDG-PET/CT
• acute rejection
• kidney biopsy
• kidney transplantation
• magnetic resonance imaging
• ultrasonography