Urinary Biomarkers for Cell Cycle Arrest TIMP-2 and IGFBP7 for Prediction of Graft Function Recovery after Kidney Transplantation

TIMP-2 and IGFBP7 have been identified and validated for the early detection of renal injury in critically ill patients, but data on recovery of allograft function after kidney transplantation (KTx) are scarce. In a prospective observational multicenter cohort study of renal transplant recipients, urinary [TIMP-2] × [IGFBP7] was evaluated daily from day 1 to 7 after KTx. Different stages of early graft function were defined: immediate graft function (IGF) (decrease ≥ 10% in serum creatinine (s-crea) within 24 h post KTx); slow graft function (SGF) (decrease in s-crea < 10% within 24 h post KTx); and delayed graft function (DGF) (any dialysis needed within the first week after KTx). A total of 186 patients were analyzed. [TIMP-2] × [IGFBP7] was significantly elevated as early as day 1 in patients with DGF compared to SGF and IGF. ROC analysis of [TIMP-2] × [IGFBP7] at day 1 post-transplant for event "Non-DGF" revealed a cut-off value of 0.9 (ng/mL)2/1000 with a sensitivity of 87% and a specificity of 71%. The positive predictive value for non-DGF was 93%. [TIMP-2] × [IGFBP7] measured at day 1 after KTx can predict early recovery of transplant function and is therefore a valuable biomarker for clinical decision making.

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.

Use of a Targeted Urine Proteome Assay (TUPA) to identify protein biomarkers of delayed recovery after kidney transplant

PURPOSE

Development of delayed graft function (DGF) following kidney transplant is associated with poor outcomes. An ability to rapidly identify patients with DGF versus those with immediate graft function (IGF) may facilitate the treatment of DGF and the research needed to improve prognosis. The purpose of this study was to use a Targeted Urine Proteome Assay to identify protein biomarkers of delayed recovery from kidney transplant.

EXPERIMENTAL DESIGN

Potential biomarkers were identified using the Targeted Urine Proteome (MRM) Assay to interrogate the relative DGF/IGF levels of expression of 167 proteins in urine taken 12-18 h after kidney implantation from 21 DGF, 15 SGF (slow graft function), and 16 IGF patients. An iterative Random Forest analysis approach evaluated the relative importance of each biomarker, which was then used to identify an optimum biomarker panel that provided the maximum sensitivity and specificity with the least number of biomarkers.

CONCLUSIONS AND CLINICAL RELEVANCE

Four proteins were identified that together distinguished DGF with a sensitivity of 77.4%, specificity of 82.6%, and AUC of 0.891. This panel represents an important step toward identifying DGF at an early stage so that more effective treatments can be developed to improve long-term graft outcomes.

Pre-transplant Evaluation of Donor Urinary Biomarkers can Predict Reduced Graft Function After Deceased Donor Kidney Transplantation

Several recipient biomarkers are reported to predict graft dysfunction, but these are not useful in decision making for the acceptance or allocation of deceased donor kidneys; thus, it is necessary to develop donor biomarkers predictive of graft dysfunction. To address this issue, we prospectively enrolled 94 deceased donors and their 109 recipients who underwent transplantation between 2010 and 2013 at 4 Korean transplantation centers. We investigated the predictive values of donor urinary neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and L-type fatty acid binding protein (L-FABP) for reduced graft function (RGF). We also developed a prediction model of RGF using these donor biomarkers. RGF was defined as delayed or slow graft function. Multiple logistic regression analysis was used to generate a prediction model, which was internally validated using a bootstrapping method. Multiple linear regression analysis was used to assess the association of biomarkers with 1-year graft function. Notably, donor urinary NGAL levels were associated with donor AKI (P = 0.014), and donor urinary NGAL and L-FABP were predictive for RGF, with area under the receiver-operating characteristic curves (AUROC) of 0.758 and 0.704 for NGAL and L-FABP, respectively. The best-fit model including donor urinary NGAL, L-FABP, and serum creatinine conveyed a better predictive value for RGF than donor serum creatinine alone (P = 0.02). In addition, we generated a scoring method to predict RGF based on donor urinary NGAL, L-FABP, and serum creatinine levels. Diagnostic performance of the RGF prediction score (AUROC 0.808) was significantly better than that of the DGF calculator (AUROC 0.627) and the kidney donor profile index (AUROC 0.606). Donor urinary L-FABP levels were also predictive of 1-year graft function (P = 0.005). Collectively, these findings suggest donor urinary NGAL and L-FABP to be useful biomarkers for RGF, and support the use of a new scoring system based on donor biomarkers to facilitate decision-making in acceptance and allocation of deceased donor kidneys and contribute to maximal organ utilization.

Association of Brain-dead Donor's Urine Neutrophil Gelatinase-associated Lipocalin Levels With Kidney Allograft Function

INTRODUCTION

Development of delayed graft function is more prevalent in patients receiving a kidney allograft from brain-dead than living donors. This study aimed to evaluate the association between urine neutrophil gelatinase-associated lipocalin (NGAL) levels in brain-dead donors and subsequent allograft function.

MATERIALS AND METHODS

Urine NGAL concentration was measured in urine samples obtained from 24 brain-dead kidney allograft donors before organ retrieval. The 24 kidney recipients were followed for 6 months. The immunosuppressive therapy was similar for all of the recipients. Following transplantation, plasma creatinine was recorded daily during the recipient's stay in the hospital and then at 1, 3, and 6 months after transplantation. Delayed graft function was defined as the need for dialysis in the first 7 days after transplantation.

RESULTS

The mean age of the donors was 28.7 ± 11.2 years and 70.8% were men. Their median urine NGAL level was 7.4 ng/ml (range, 2 ng/mL to 45 ng/mL). Urine NGAL levels were only associated with the need for cardiopulmonary resuscitation (P = .007). On the 1st day after transplantation, 16.7% of the recipients developed delayed graft function, which was declined to 12.5% on the 2nd day and to 8.3% during the 3rd day and the following days. No significant association was observed between the donor's urine NGAL levels and graft function (P = .86).

CONCLUSIONS

Our results did not show any association between urine NGAL levels and outcome of allograft function obtained from brain-dead donors. Larger studies are required to confirm this finding.

Effect of N-acetyl cysteine and vitamin C on kidney allograft function biomarkers interleukin-18 and neutrophil gelatinase-associated lipocalin

INTRODUCTION

Delayed graft function (DGF) is a consequence of ischemia-reperfusion injuries in kidney allografts, for which no definite treatment is available. The neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) are introduced as the most promising urine biomarkers to detect DGF. N-acetylcysteine (NAC) and vitamin C, well-known potent antioxidants that scavenge free radicals, may alleviate kidney injury. This study investigated the protective effects of NAC alone and in combination with vitamin C on DGF, by measuring IL-18 and NGAL in living donor kidney transplantations.

MATERIALS AND METHODS

Patients transplanted between January 2011 and February 2013 were randomly divided into 3 groups to receive routine anti-rejection medication only (n = 32), NAC plus routine immunosuppressive regimen (NAC group; n = 33), and NAC and vitamin C plus routine regimen (NAC and vitamin C group; n = 19). Urine samples were taken 4 hours and 24 hours after transplantation. Enzyme-linked immunosorbent assay kits were utilized for measuring urine NGAL and IL-18.

RESULTS

There were no significant differences in the DGF prevalence and its duration between the study arms. Although the levels of NGAL and IL-18 decreased in the NAC and NAC and vitamin C groups, these reductions were not significant. Glomerular filtration rate at 30 and 60 days after transplantation were not significantly different between study groups, either.

CONCLUSIONS

Our results showed that NAC is a safe drug without significant adverse effects in kidney transplant recipients; however, its potential useful effects on urinary biomarkers of DGF were not illustrated in the present study.

[Lipocalin and kidney transplant]

INTRODUCTION

Kidney transplantation is frequently complicated by delayed graft function (DGF). DGF is associated with more frequent rejection episodes, increased need of post-transplantation biopsies, dialysis sessions and prolonged hospitalization. These complications may have negative impact on long-term survival of transplanted kidney.Urinary neutrophil gelatinase-associated lipocalin (uNGAL) is regarded as acute kidney injury marker.This preliminary study aimed at evaluating whether uNGAL may be early predictor of DGF in kidney transplanted patients.

SUBJECTS AND METHODS

Urine samples were collected from renal transplant recipients on day 1 post-transplantation to determine 24/h urinary NGAL and creatinine excretion. On same day, routine blood chemistry was assessed.

RESULTS

N. 20 renal transplant recipients were evaluated. DGF was observed in n. 6 patients (DGF-patients). In DGF-patients compared to NO-DGF-patients, mean age was higher (586 Vs 5111, p=0.001), while 24/h urine output (5735 Vs 4150 2230 ml/24h; p=0.001) and urinary creatinine excretion (191184 Vs 683660 mg/24h; p=0.001) were lower. No difference was found between DGF- and NO-DGF-patients in 24/h urinary NGAL excretion (1,202,20 Vs 2,444,0 mg/24h; p<0.20). In univariate analysis, DGF was inversely associated to 24/h urine output (r2=-0.795, p=0.001) and urinary creatinine excretion (r2=-0.480, p=0.037) and positively to age (r2=0.446, p=0.049). In multivariate analysis 24/h urine output (p=0.014) and 24/h urinary creatinine excretion (p=0.039) were associated to DGF.

CONCLUSION

This preliminary study suggests that 24/h urinary NGAL excretion, measured 1 day after kidney transplantation, is not a reliable predictor of DGF. Larger study with longer observation period is mandatory.

[Neutrophil gelatinase-associated lipocalin (u-NGAL) in the assessment of renal function in patients after kidney allotransplantation]

BACKGROUND

Early dysfunction of transplanted kidney is a serious complication that can lead to the premature loss of transplant. Ischemic and reperfusion injury of donor kidney leads to the disturbance of the function of the graft, which is a form of post-transplantation acute kidney injury that causes the relevance of search of early markers for diagnosis.

OBJECTIVE

Evaluation of the diagnostic value of determination in the urine neutrophilgelatinase-associated lipocalin (u-NGAL) in patients in the early period after kidney transplantation.

METHODS

An open, randomized, retrospective comparative study of 80 patients, who underwent kidney transplantation from a living human-related donor (group 1, 50 patients) and from donor with brain death documentation (group 2, 30 patients) was carried out. In 20 patients of the second group (group 2a) rapid recovery of graft function was observed, and in 10 patients (group 2b)--delayed graft recovery as a result of postischemic acute kidney injury. During the first five post-transplantation days investigated biochemical analysis of blood and urine, as well as the marker u-NGAL.

RESULTS

Because of kidney transplantation was performed to the patients with end-stage chronic renal failure, high values of urea and creatinine in the blood samples during the first postoperative days were noted, that reflected the severity of the preoperative state of the patients. In the patients, who underwent human-related kidney transplantation, a more favorable picture of the investigated laboratory parameters was seen. Values of u-NGAL in this group in the early post-transplant period were normal, which attested to the absence of significant ischemic injury of transplanted kidney. In 30 patients with cadaver kidney transplantation average u-NGAL value during the first post-transplant day was 14-times fold exceeded normal range (160 ng/ml), while in 50 patients of the group with human-related transplantation--only 2 times. In the first day in group 2a average u-NGAL value decreased to normal, while in group 2b, where renal replacement therapy was carried out from the first day, remained extremely high (more than 2000 ng/ml, p<0.001 to compare with other two groups) during all 5 days of investigation. Conducting of hemodialysis sessions during the first week was required in 10 patients of group 2b, on the 2nd week--9 patients, on the 3 and 4 week in 5 patients 5, and on the fifth week--in 3 patients.

CONCLUSIONS

Due to prolonged period of ischemia in kidney transplantation from a donor with established brain death the level of u-NGAL in these patients was significantly higher than in the kidneys transplantation from living human-related donor. In patients after transplantation dynamics of u-NGAL allows to identify patients with delayed graft function recovery and the need for renal replacement therapy already in the early postoperative period.

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 NGAL and IL-18 are predictive biomarkers for delayed graft function following kidney transplantation

Delayed graft function (DGF) due to tubule cell injury frequently complicates deceased donor kidney transplants. We tested whether urinary neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) represent early biomarkers for DGF (defined as dialysis requirement within the first week after transplantation). Urine samples collected on day 0 from recipients of living donor kidneys (n = 23), deceased donor kidneys with prompt graft function (n = 20) and deceased donor kidneys with DGF (n = 10) were analyzed in a double blind fashion by ELISA for NGAL and IL-18. In patients with DGF, peak postoperative serum creatinine requiring dialysis typically occurred 2-4 days after transplant. Urine NGAL and IL-18 values were significantly different in the three groups on day 0, with maximally elevated levels noted in the DGF group (p < 0.0001). The receiver-operating characteristic curve for prediction of DGF based on urine NGAL or IL-18 at day 0 showed an area under the curve of 0.9 for both biomarkers. By multivariate analysis, both urine NGAL and IL-18 on day 0 predicted the trend in serum creatinine in the posttransplant period after adjusting for effects of age, gender, race, urine output and cold ischemia time (p < 0.01). Our results indicate that urine NGAL and IL-18 represent early, predictive biomarkers of DGF.