Deceased-donor kidney perfusate and urine biomarkers for kidney allograft outcomes: a systematic review

Protein biomarkers in assessing kidney quality before transplantation‑current status and future perspectives (Review)

To meet the demand for kidney transplants (KTx), organs are frequently retrieved not only from standard criteria donors (SCD; a donor who is aged <50 years and suffered brain death from any number of causes, such as traumatic injuries or a stroke) but also from expanded criteria donors (any donor aged >60 years or donors aged >50 years with two of the following: A history of high blood pressure, a creatinine serum level ≥1.5 mg/dl or death resulting from a stroke). This comes at the cost of a higher risk of primary non‑function (the permanent hyperkalemia, hyperuremia and fluid overload that result in the need for continuous dialysis after KTx), delayed graft function (the need for dialysis session at least once during the first week after KTx), earlier graft loss and urinary complications (vesico‑ureteral reflux, obstruction of the vesico‑ureteral anastomosis, urine leakage). At present, there are no commercially available diagnostic tools for assessing kidney quality prior to KTx. Currently available predictive models based on clinical data, such as the Kidney Donor Profile Index, are insufficient. One promising option is the application of perfusion solutions for protein biomarkers of kidney quality and predictors of short‑ and long‑term outcomes. However, to date, protein markers that can be detected with ELISA, western blotting and cytotoxic assays have not been identified to be a beneficial predictors of kidney quality. These include lactate dehydrogenases, glutathione S‑transferases, fatty acid binding proteins, extracellular histones, IL‑18, neutrophil gelatinase‑associated lipocalin, MMPs and kidney injury molecule‑1. However, novel methods, including liquid chromatography‑mass spectrometry (LC‑MS) and microarrays, allow the analysis of all renal proteins suspended/dissolved in the acellular preservation solution used for kidney storage before KTx (including hypothermic machine perfusion as one of kidney storage methods) e.g. Belzer University of Wisconsin. Recent proteomic studies utilizing LC‑MS have identified complement pathway elements (C3, C1QB, C4BPA, C1S, C1R and C1RL), desmoplakin, blood coagulation pathway elements and immunoglobulin heavy variable 2‑26 to be novel predictors of kidney quality before transplantation. This was because they were found to correlate with estimated glomerular filtration rate at 3 and 12 months after kidney transplantation. However, further proteomic studies focusing on distinct markers obtained from hypothermic and normothermic machine perfusion are needed to confirm their predictive value and to improve kidney storage methods. Therefore, the present literature review from PubMed, Scopus, Embase and Web of Science was performed with the aims of summarizing the current knowledge on the most frequently studied single protein biomarkers. In addition, novel analytical methods and insights into organ injury during preservation were documented, where future directions in assessing organ quality before kidney transplantation were also discussed.

Diagnostic and Prognostic Value of Machine Perfusion Biomarkers in Kidney Graft Evaluation

BACKGROUND

With the rising prevalence of end-stage kidney disease, the use of expanded criteria donor allografts, seen as essential for meeting organ demand, still proves challenging due to their higher risk of graft loss, delayed function, and rejection. Machine perfusion, a technique in preserving allografts, offers improved allograft outcomes compared to static cold storage while allowing for the noninvasive measurement of kidney injury biomarkers in the perfusate solution. This offers an objective method to assess graft function at various preservation stages.

MATERIALS AND METHODS

We conducted a narrative review of the databases PubMed and Scopus, including studies written in the English language and published after 2010.

RESULTS

In this narrative review, we identified biomarkers, like 4-hydroxyproline, taurine, and glutathione transferase, as predictive markers of delayed graft function. Additionally, biomarkers, like extracellular histone h3, vascular cell adhesion protein, and matrix metalloprotease protein, have shown correlation with decreased graft function, although their predictive ability remains inconclusive.

DISCUSSION

The review outlines various suggestions for potential areas of research focus to enhance future expanded criteria donor allograft utilization. However, limitations exist, including the absence of a singular reliable biomarker and the challenges of validating biomarker effectiveness across diverse outcomes.

Prognostic Biomarkers in Kidney Transplantation: A Systematic Review and Critical Appraisal

SIGNIFICANCE STATEMENT

Why are there so few biomarkers accepted by health authorities and implemented in clinical practice, despite the high and growing number of biomaker studies in medical research ? In this meta-epidemiological study, including 804 studies that were critically appraised by expert reviewers, the authors have identified all prognostic kidney transplant biomarkers and showed overall suboptimal study designs, methods, results, interpretation, reproducible research standards, and transparency. The authors also demonstrated for the first time that the limited number of studies challenged the added value of their candidate biomarkers against standard-of-care routine patient monitoring parameters. Most biomarker studies tended to be single-center, retrospective studies with a small number of patients and clinical events. Less than 5% of the studies performed an external validation. The authors also showed the poor transparency reporting and identified a data beautification phenomenon. These findings suggest that there is much wasted research effort in transplant biomarker medical research and highlight the need to produce more rigorous studies so that more biomarkers may be validated and successfully implemented in clinical practice.

BACKGROUND

Despite the increasing number of biomarker studies published in the transplant literature over the past 20 years, demonstrations of their clinical benefit and their implementation in routine clinical practice are lacking. We hypothesized that suboptimal design, data, methodology, and reporting might contribute to this phenomenon.

METHODS

We formed a consortium of experts in systematic reviews, nephrologists, methodologists, and epidemiologists. A systematic literature search was performed in PubMed, Embase, Scopus, Web of Science, and Cochrane Library between January 1, 2005, and November 12, 2022 (PROSPERO ID: CRD42020154747). All English language, original studies investigating the association between a biomarker and kidney allograft outcome were included. The final set of publications was assessed by expert reviewers. After data collection, two independent reviewers randomly evaluated the inconsistencies for 30% of the references for each reviewer. If more than 5% of inconsistencies were observed for one given reviewer, a re-evaluation was conducted for all the references of the reviewer. The biomarkers were categorized according to their type and the biological milieu from which they were measured. The study characteristics related to the design, methods, results, and their interpretation were assessed, as well as reproducible research practices and transparency indicators.

RESULTS

A total of 7372 publications were screened and 804 studies met the inclusion criteria. A total of 1143 biomarkers were assessed among the included studies from blood ( n =821, 71.8%), intragraft ( n =169, 14.8%), or urine ( n =81, 7.1%) compartments. The number of studies significantly increased, with a median, yearly number of 31.5 studies (interquartile range [IQR], 23.8-35.5) between 2005 and 2012 and 57.5 (IQR, 53.3-59.8) between 2013 and 2022 ( P < 0.001). A total of 655 studies (81.5%) were retrospective, while 595 (74.0%) used data from a single center. The median number of patients included was 232 (IQR, 96-629) with a median follow-up post-transplant of 4.8 years (IQR, 3.0-6.2). Only 4.7% of studies were externally validated. A total of 346 studies (43.0%) did not adjust their biomarker for key prognostic factors, while only 3.1% of studies adjusted the biomarker for standard-of-care patient monitoring factors. Data sharing, code sharing, and registration occurred in 8.8%, 1.1%, and 4.6% of studies, respectively. A total of 158 studies (20.0%) emphasized the clinical relevance of the biomarker, despite the reported nonsignificant association of the biomarker with the outcome measure. A total of 288 studies assessed rejection as an outcome. We showed that these rejection studies shared the same characteristics as other studies.

CONCLUSIONS

Biomarker studies in kidney transplantation lack validation, rigorous design and methodology, accurate interpretation, and transparency. Higher standards are needed in biomarker research to prove the clinical utility and support clinical use.

An analysis of the relationship between donor and recipient biomarkers and kidney graft function, dysfunction, and rejection

BACKGROUND

The study aimed to find predictive biomarkers to evaluate donor kidney function to predict graft dysfunction as well as to assess an early signs of acute graft rejection.

METHOD

Twenty-seven deceased donors and 54 recipients who underwent a successful kidney transplantation were enrolled in the study. An assessment was made in serum and urine from donors and recipients to measure the following biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), tissue inhibitor of metalloproteinase 2 (TIMP-2) and urinary N-acetyl-b-D-glucosaminidase (uNAG). These biomarkers were used to establish a model for predicting a reduced graft function (RGF) classified as either a delayed or slow graft function.

RESULT

Our analysis suggest that out of four tested biomarkers, the serum TIMP-2 and uNAG levels of the donors had a predictive value for RGF; the area under the receiver operating characteristic curves (AUROC) of serum TIMP-2 and uNAG were 0.714 and 0.779, respectively. The combined best fitting prediction model of serum TIMP-2, uNAG, and creatinine levels was better in predicting RGF than the serum creatinine level alone. In addition, the recipient serum TIMP-2 level on the third day post-transplantation (D3) was associated with the estimated glomerular filtration rate (eGFR) on the seventh day post-transplantation (D7; OR 1.119, 95% CI 1.016-1.233, p = 0.022). Furthermore, the ROC curve value revealed that the AUROC of TIMP-2 on D3 was 0.99 (95% CI 0.97-1, p < 0.001), and this was the best predictive value of the renal function on D7.

CONCLUSIONS

Donor serum TIMP-2 and uNAG levels are useful predictive biomarkers because they can provide the donor-based prediction for RGF.

Perfusate Neutrophil Gelatinase-Associated Lipocalin, Kidney Injury Molecular-1, Liver-Type Fatty Acid Binding Protein, and Interleukin-18 as Potential Biomarkers to Predict Delayed Graft Function and Long-Term Prognosis in Kidney Transplant Recipients: A Single-Center Retrospective Study

BACKGROUND Delayed graft function (DGF) caused by ischemia-reperfusion injury is a common pathophysiological process that should be monitored by specific biomarkers in addition to serum creatinine. Thus, this single-center retrospective study aimed to investigate the association between levels of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecular-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), and interleukin-18 (IL-18) in DGF associated with acute kidney injury in kidney transplant recipients (KTRs) and estimated glomerular filtration rate (eGFR) at 3 years post-transplant. MATERIAL AND METHODS A total of 102 KTRs [14(13.7%) of DGF and 88(86.3%) of NON-DGF] were enrolled. DGF was defined as "dialysis is needed within 1 week after kidney transplantation". NGAL, KIM-1, L-FABP, and IL-18 were obtained from perfusate samples of donation-after-cardiac-death (DCD) kidneys, and measured by ELISA. RESULTS Compared to the NON-DGF group, KTRs in the DGF group had a statistically significant increase in levels of NGAL (P<0.001) and KIM-1 (P<0.001). Multiple logistic regression analyses showed that NGAL (OR=1.204, 95% CI 1.057-1.372, P=0.005) and KIM-1 (OR=1.248, CI=1.065-1.463, P=0.006) could be regarded as independent risk factors. The accuracy of NGAL and KIM-1 was 83.3% and 82.1%, respectively, calculated using the area under the receiver operating characteristic curve. Furthermore, the eGFR at 3 years post-transplant had a moderate negative correlation with NGAL (r=-0.208, P=0.036) and KIM-1 (r=-0.260, P=0.008). CONCLUSIONS Our results support those from previous studies showing that perfusate levels of NGAL and KIM-1 are associated with DGF in KTRs and also with reduced eGFR at 3 years post-transplant.

Extracellular histone release by renal cells after warm and cold ischemic kidney injury: Studies in an ex-vivo porcine kidney perfusion model

Extracellular histones are cytotoxic molecules involved in experimental acute kidney injury. In patients receiving a renal transplant from donors after circulatory death, who suffer from additional warm ischemia, worse graft outcome is associated with higher machine perfusate extracellular histone H3 concentrations. We now investigated temperature-dependent extracellular histone release in an ex vivo porcine renal perfusion model, and subsequently studied histone release in the absence and presence of non-anticoagulant heparin. Seven pairs of ischemically damaged porcine kidneys were machine perfused at 4°C (cold ischemia) or 28°C (warm ischemia). Perfusate histone H3 concentration was higher after warm as compared to cold ischemia (median (IQR) = 0.48 (0.20-0.83) μg/mL vs. 0.02 (0.00-0.06) μg/mL; p = .045, respectively). Employing immune-electron microscopy (EM), histone containing cytoplasmic protrusions of tubular and endothelial cells were found after warm ischemic injury. Furthermore, abundant histone localization was detected in debris surrounding severely damaged glomerular cells, in a "buck shot" pattern. In vitro, histones were cytotoxic to endothelial and kidney epithelial cells in a temperature-dependent manner. In a separate ex vivo experiment, addition of heparin did not change the total histone H3 levels observed in the perfusate but revealed a continuous increase in the level of a lower molecular weight histone H3 variant. Our findings show that ischemically damaged kidneys release more extracellular histones in warm ischemia, which by EM was due to histone release by renal cells. Blocking of histone-mediated damage during transplantation may be beneficial in prevention of renal injury.

Preoperative Function Assessment of Ex Vivo Kidneys with Supervised Machine Learning Based on Blood and Urine Markers Measured during Normothermic Machine Perfusion

Establishing an objective quality assessment of an organ prior to transplantation can help prevent unnecessary discard of the organ and reduce the probability of functional failure. In this regard, normothermic machine perfusion (NMP) offers new possibilities for organ evaluation. However, to date, few studies have addressed the identification of markers and analytical tools to determine graft quality. In this study, function and injury markers were measured in blood and urine during NMP of 26 porcine kidneys and correlated with ex vivo inulin clearance behavior. Significant differentiation of kidneys according to their function could be achieved by oxygen consumption, oxygen delivery, renal blood flow, arterial pressure, intrarenal resistance, kidney temperature, relative urea concentration, and urine production. In addition, classifications were accomplished with supervised learning methods and histological analysis to predict renal function ex vivo. Classificators (support vector machines, k-nearest-neighbor, logistic regression and naive bayes) based on relevant markers in urine and blood achieved 75% and 83% accuracy in the validation and test set, respectively. A correlation between histological damage and function could not be detected. The measurement of blood and urine markers provides information of preoperative renal quality, which can used in future to establish an objective quality assessment.

Organ-specific metabolic profiles of the liver and kidney during brain death and afterwards during normothermic machine perfusion of the kidney

We investigated metabolic changes during brain death (BD) using hyperpolarized magnetic resonance (MR) spectroscopy and ex vivo graft glucose metabolism during normothermic isolated perfused kidney (IPK) machine perfusion. BD was induced in mechanically ventilated rats by inflation of an epidurally placed catheter; sham-operated rats served as controls. Hyperpolarized [1-¹³ C]pyruvate MR spectroscopy was performed to quantify pyruvate metabolism in the liver and kidneys at 3 time points during BD, preceded by injecting hyperpolarized[1-¹³ C]pyruvate. Following BD, glucose oxidation was measured using tritium-labeled glucose (d-6-3H-glucose) during IPK reperfusion. Quantitative polymerase chain reaction and biochemistry were performed on tissue/plasma. Immediately following BD induction, lactate increased in both organs (liver: eµ_d 0.21, 95% confidence interval [CI] [-0.27, -0.15]; kidney: eµ_d 0.26, 95% CI [-0.40, -0.12]. After 4 hours of BD, alanine production decreased in the kidney (eµ_d 0.14, 95% CI [0.03, 0.25], P < .05). Hepatic lactate and alanine profiles were significantly different throughout the experiment between groups (P < .01). During IPK perfusion, renal glucose oxidation was reduced following BD vs sham animals (eµ_d 0.012, 95% CI [0.004, 0.03], P < .001). No differences in enzyme activities were found. Renal gene expression of lactate-transporter MCT4 increased following BD (P < .01). In conclusion, metabolic processes during BD can be visualized in vivo using hyperpolarized magnetic resonance imaging and with glucose oxidation during ex vivo renal machine perfusion. These techniques can detect differences in the metabolic profiles of the liver and kidney following BD.

A systematic review to identify whether perfusate biomarkers produced during hypothermic machine perfusion can predict graft outcomes in kidney transplantation

There is good evidence to support the use of hypothermic machine perfusion (HMP) over static cold storage as the favoured preservation method for deceased donor kidneys. However, the utility of HMP as a tool to assess the viability of kidneys for transplant is unclear. There is a need to determine whether perfusate biomarkers produced during HMP can predict post-transplant outcomes and assess the suitability of organs for transplantation. Three different databases (MEDLINE, Embase, Transplant Library) were screened to 31 May 2019. Articles were included if a relationship was reported between one or more perfusate biomarkers and post-transplant outcomes. Studies were assessed and graded for methodological quality and strength of evidence. Glutathione S-transferase was the most promising biomarker for predicting delayed graft function, but its predictive ability was at best moderate. Analysis of primary nonfunction rates was challenging due to low occurrence rates and small sample sizes. Existing studies are limited in quality and have not yielded biomarkers for kidneys undergoing HMP that are able to predict post-transplant outcomes with sufficient accuracy to support routine clinical use. Further studies with larger samples and more robust methodology are needed. (PROSPERO registration: CRD42019121161).

PROspective Evaluation of Chronic Pancreatitis for EpidEmiologic and Translational StuDies: Rationale and Study Design for PROCEED From the Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer

Prospective Evaluation of Chronic Pancreatitis for Epidemiologic and Translational Studies (PROCEED) is the first prospective, observational cohort study of chronic pancreatitis (CP) in the United States. The primary goals of PROCEED are to define disease progression, test the predictive capability of candidate biomarkers, and develop a platform to conduct translational and mechanistic studies in CP. Using objective and consensus-driven criteria, PROCEED will enroll adults at different stages of CP-controls, suspected CP, and definite CP. In addition to collecting detailed information using structured case report forms and protocol-mandated evaluations at baseline and during follow-up, PROCEED will establish a linked biorepository of blood, urine, saliva, stool, pancreatic fluid, and pancreatic tissue. Enrollment for PROCEED began in June 2017. As of July 1, 2018, nine clinical centers of the Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer are enrolling, and 350 subjects have completed baseline evaluation. In conclusion, PROCEED will provide the most accurate and reliable estimates to date on progression of CP. The established cohort and biorepository will facilitate numerous analyses, leading to new strategies for diagnosis, methods to monitor disease progression, and treatment of CP.

A Retrospective Cohort Study on Rehospitalization following Expanded Criteria Donor Kidney Transplantation

Background

Expanded criteria donor (ECD) kidneys are commonly used but are associated with increased graft failure. Graft failure is in turn related to rehospitalization within thirty days post transplant. Our goal was to determine whether ECD kidneys independently lead to rehospitalization within 30 days, 1 year, and 2 years after transplant.

Methods

All adult first-time recipients of deceased donor kidneys transplanted from 2003-2012 at our center were reviewed. Models included demographics, medical comorbidities, center for disease control high-risk kidney, ECD kidney, ischemia times, cause of renal failure, immunosuppressive regimen, positive psychiatric screening, alcoholism, surgeon, year the transplant was performed, years on dialysis before transplant, and the number of inpatient hospitalizations within 6 months prior to transplant. We conducted Andersen-Gill modeling and propensity score matching followed by logistic regression. We also used multivariable linear regression to predict average length of stay during rehospitalization.

Results

More ECD patients had a rehospitalization at 1 year (70.3% versus 59%, log-rank test p=0.014). Thirty-day and 2-year time marks were not significant. Andersen-Gill models predicting successive hospitalizations yielded HR of 1.42 (p=0.002) and 1.32 (p=0.015) for ECD patients at 1 and 2 years of after transplantation, respectively. Propensity score matching and logistic regression showed a significant relative risk of 1.630 at one year (p=0.033) and 1.313 at two years (p=0.268). There was no significant association between ECD and subsequent lengths of hospital stay.

Conclusion

Receiving an ECD kidney is independently associated with multiple readmissions within 2 years of transplant but unrelated to length of stay.

Biomarkers and Pharmacogenomics in Kidney Transplantation

This review is focused on present and future biomarkers, along with pharmacogenomics used in clinical practice for kidney transplantation. It aims to highlight biomarkers that could potentially be used to improve kidney transplant early and long-term graft survival, but also potentially patient co-morbidity. Future directions for improving outcomes are discussed, which include immune tolerance and personalising immunosuppression regimens.

Hypothermic Machine Perfusion Results in a Marginal Kidney Transplant Programme

BACKGROUND

Hypothermic machine perfusion (HMP) of deceased donor kidneys is associated with a better outcome than static cold storage, predominantly in marginal donors. Nevertheless, there is little evidence supporting whether graft centre of origin and donor category impact HMP results.

OBJECTIVE

To identify factors impacting HMP in transplantation from marginal donors.

DESIGN, SETTING, AND PARTICIPANTS

Analysis of prospectively collected cohort data of expanded criteria donor (ECD) and donor after circulatory death (DCD) categories II and III was performed. A total of 214 adult recipients of first kidney transplantation with complete data and a minimum of 6-mo follow-up were included.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Delayed graft function (DGF) was defined as the lack of decrease in creatinine level in the first 48h. Graft loss was defined as return to dialysis or creatinine clearance <15ml/min/1.73m². Univariate and multivariate logistic regression analyses for DGF were constructed to identify independent risk factors. Recipient and graft survival (GS) analyses were conducted by Kaplan-Meier, and univariate and multivariate Cox regression analyses.

RESULTS AND LIMITATION

DGF occurred in 32.8% of imported and 20.5% of local grafts (p=0.059). Only donor category (DCD; odds ratio [OR]: 6.6, p=0.008) and haemodialysis (OR: 3.5, p=0.002) were significantly associated with DGF development. The 1-yr GS rate was 92.5% in the local donor group and 84.3% in the imported donor group (p=0.050). Multivariate analysis by Cox proportional hazards model identified only donor category (hazard ratio [HR] 10.99, p=0.001) and donor age (HR 1.07, p=0.005) as predictive variables for GS. The small sample size of the DCD group diminished the statistical power and did not permit a subgroup analysis to determine the impact of specific DCD category on HMP results.

CONCLUSIONS

DCD donor category, but not donor centre of origin, impacted DGF development and GS in the HMP of deceased donor kidneys.

PATIENT SUMMARY

Currently, the number of donors is insufficient to meet the demand for renal grafts. Expanded criteria for donation after brain death and donation after circulatory death (DCD) programmes have been developed as strategies to minimise this problem. Hypothermic machine perfusion has previously demonstrated its usefulness in expanded criteria donation and DCD preservation. DCD type and donor age increase the risk of graft loss.

Systematic review of kidney transplantation functional predictors

CONTEXT

Kidney transplantation from donors with expanded criteria has increased the pool of kidneys at the cost of a higher risk of short and long-term graft dysfunction. The main issue lies in determining which kidneys will offer acceptable function and survival compared with the risk represented by surgery and subsequent immunosuppression.

OBJECTIVE

The objective of our article is to review the current evidence on the tools for predicting the functionality of kidney transplantation from cadaveric donors with expanded criteria and determining the validity for their use in standard practice.

ACQUISITION OF EVIDENCE

We conducted a systematic literature review according to the PRISM criteria, through Medline (http://www.ncbi.nlm.nih.gov) and using the keywords (in isolation or in conjunction) "cadaveric renal transplantation; kidney graft function appraisal, graft function predictors". We selected prospective and retrospective series and review articles. A total of 375 articles were analysed, 39 of which were ultimately selected for review.

SUMMARY OF THE EVIDENCE

The predictors of functionality include the following: The donor risk indices; the calculation of the renal functional weight or the assessment of the nephronic mass; the measurement of vascular resistances during perfusion in hypothermia; the measurement of the donor's biomarkers in urine and in the perfusion liquid; the measurement of functional and reperfusion parameters in normothermia; and the measurement of morphological parameters (microscopic and macroscopic) of the target organ. In this article, we present an explanatory summary of each of these parameters, as well as their most recent evidence on this issue.

DISCUSSION

None of the reviewed parameters in isolation could reliably predict renal function and graft survival. There is a significant void in terms of the macroscopic assessment of kidney transplantation.

CONCLUSIONS

We need to continue developing predictors of renal functionality to accurately define the distribution of each currently available donor kidney.

Kidney perfusion: some like it hot others prefer to keep it cool

PURPOSE OF REVIEW

Machine perfusion technologies provide an opportunity for improved preservation, organ assessment, and resuscitation of damaged kidneys. This review summarizes the recent advances in hypothermic and normothermic kidney machine perfusion technologies.

RECENT FINDINGS

Modifications to the perfusion conditions with the addition of oxygen during hypothermic machine perfusion can support a low level of metabolism, which in experimental settings improves graft function. Normothermic machine perfusion technologies are evolving in different directions including short-duration resuscitation, more prolonged periods of perfusion, and the transition between hypothermic and normothermic conditions. Clinical trials are ongoing in both hypothermic and normothermic settings. Functional parameters can be used to assess kidney quality and although normothermic machine perfusion may hold an advantage over hypothermic machine perfusion, new metabolomic, proteomic, and genomic technologies may be applied in the future to both technologies to provide more rigorous information on kidney quality. Promoting recovery by introducing an intervention during perfusion is an attractive area of research and therapies targeting the endothelium are a particular area of interest.

SUMMARY

A great deal of research is still needed to optimize and logistically place hypothermic and normothermic perfusion technologies. In the future, we may progress toward organ-tailored preservation whereby high-risk kidneys can undergo assessment and repair before transplantation.

Presence of Cytotoxic Extracellular Histones in Machine Perfusate of Donation After Circulatory Death Kidneys

BACKGROUND

Extracellular histones are cytotoxic molecules that are related to cell stress and death. They have been shown to play a crucial role in multiple pathophysiologic processes like sepsis, inflammation, vascular dysfunction, and thrombosis. Their role in organ donation and graft function and survival is still unknown. The aim of this study was to assess whether an association exists between the presence of extracellular histones in machine perfusates and deceased donor kidney viability.

METHODS

Machine perfusates of 390 donations after circulatory death kidneys were analyzed for histone concentration, and corresponding graft function and survival were assessed.

RESULTS

Extracellular histone concentrations were significantly higher in perfusates of kidneys with posttransplant graft dysfunction (primary nonfunction and delayed graft function) and were an independent risk factor for delayed graft function (odds ratio, 2.152; 95% confidence interval [95% CI], 1.199-3.863) and 1 year graft failure (hazard ratio, 1.386; 95% CI, 1.037-1.853), but not for primary nonfunction (odds ratio, 1.342; 95% CI, 0.900-2.002). One year graft survival was 12% higher in the group with low histone concentrations (P = 0.008) as compared with the group that contained higher histone concentrations.

CONCLUSIONS

This study warrants future studies to probe for a possible role of cytotoxic extracellular histones in organ viability and suggests that quantitation of extracellular histones might contribute to assessment of posttransplant graft function and survival.

Early experience with hypothermic machine perfusion of living donor kidneys - a retrospective study

Although hypothermic machine perfusion (HMP) has been shown to be beneficial to deceased donor kidneys, the effect of HMP on living donor kidneys (LDK) is unknown. LDK are subjected to minutes of normothermic ischemia at the time of recovery. Comparison of 16 LDK preserved by HMP with 16 LDK preserved by static cold storage (SCS). Outcomes of interest are resistive indices (RI), both while on HMP and postoperatively, and creatinine clearance (CrCl). Injury markers NGAL and LDH were seen in the perfusate of LDK in amounts similar to what is found for donation after neurological determination of death kidneys. Compared to SCS kidneys, CrCl was significantly higher in the HMP group from days 2 through 7 post-transplant [ie: day 7 (78.8 ± 5.4 vs. 54.0 ± 4.6 ml/min, P = 0.005)]. CrCl at 1 year was higher in the HMP group (81.2 ± 5.8 vs. 70.0 ± 5.3 ml/min, P = 0.03). Early post-transplant RI was significantly lower in the HMP group (0.61 ± 0.02 vs. 0.71 ± 0.02, P < 0.0001). Our data support the assertion that injury does occur during LDK procurement and suggest that some of this injury may be reversed with HMP, resulting in more favorable early RI and graft function compared to SCS kidneys.

High Urinary Aspartate Aminotransferase in the Late Posttransplant Period Predicts Rapid, Progressive Decline in Kidney Allograft Function

OBJECTIVES

Scant information is available on factors for predicting the rate of decline in kidney allograft function beyond 1 year posttransplant.We investigated whether urinary enzymes (alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, N-acetyl-β-D-hexosaminidase, and ε-glutamyl transpeptidase) in the late postoperative period can predict the decline in estimated glomerular filtration rate.

MATERIALS AND METHODS

In 79 kidney allograft recipients 1 to 17 years after kidney transplant, we assessed a value of urinary enzymes single measurement for predicting the slope of estimated glomerular filtration rate, rapid decline in estimated glomerular filtration rate (> 5 mL/min/1.73 m² /y), and significant decline in estimated glomerular filtration rate (≥ 25% from baseline) during a 2-year period.

RESULTS

At baseline, patients with estimated glomerular filtration rate < 60 mL/min/1.73 m² (n = 54) differed from those with estimated glomerular filtration rate ≥ 60 mL/min/1.73 m² (n = 25) only in their lower median urinary alanine aminotransferase:creatinine ratio (expressed as U/L:mmol/L): 0.055 versus 0.222 (P = .011). Higher urinary activity of aspartate aminotransferase at baseline predicted the negative-slope value for estimated glomerular filtration rate (beta, -0.279; standard error, 0.131; P = .037) and decline in estimated glomerular filtration rate of > 5 mL/min/1.73 m ²/year (odds ratio, 2.06; 95% confidence interval, 1.10-3.83; P = .023) over 2 years. It also predicted the drop in estimated glomerular filtration rate ≥ 25% after 1 year (odds ratio, 2.62; 95% confidence interval, 1.07-6.37; P = .034) and 2 years (odds ratio, 2.75; 95% confidence interval, 1.12-6.73; P =.027). Combined with time after transplant, urinary aspartate aminotransferase had good power for predicting an estimated glomerular filtration rate decrease ≥ 25% after 2 years of follow-up.

CONCLUSIONS

Higher urinary activity of aspartate aminotransferase in the late posttransplant period is useful for identifying transplant patients who are at risk for progressive loss of graft function.

Biomarkers for the detection of renal fibrosis and prediction of renal outcomes: a systematic review

Background

Fibrosis is the unifying pathway leading to chronic kidney disease. Identifying biomarkers of fibrosis may help predict disease progression.

Methods

We performed a systematic review to evaluate the reliability of blood and urine biomarkers in identifying fibrosis on biopsy as well as predicting renal outcomes. Using MEDLINE and EMBASE, a two-stage search strategy was implemented. Stage I identified a library of biomarkers correlating with fibrosis on biopsy. Stage II evaluated the association between biomarkers identified in stage I, and renal outcomes. Only biomarkers with moderate positive correlation with fibrosis (r > 0.40) or acceptable area under the curve (AUC >0.65) advanced to stage II.

Results

Stage I identified 17 studies and 14 biomarkers. Five biomarkers met criteria to advance to stage II, but only three were independently associated with renal outcomes. Transforming growth factor β (TGF-β) correlated with fibrosis (r = 0.60), and was associated with 1.7–3.9 times the risk of worsening renal function in 426 patients. Monocyte chemoattractant protein-1 (MCP-1) diagnosed fibrosis with AUC of 0.66 and was associated with 2.3–11.0 times the risk of worsening renal function in 596 patients. Matrix metalloproteinase-2 (MMP-2) correlated with fibrosis (r = 0.41), and was associated with 2.5 times the risk of worsening renal function.

Conclusions

Given the heterogeneity of the data due to diverse patient populations along with differing renal outcomes, a meta-analysis could not be conducted. Nonetheless we can conclude from the published data that TGF-β, MCP-1 and MMP-2 may identify patients at risk for renal fibrosis and hence worse renal outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0490-0) contains supplementary material, which is available to authorized users.

Long-Term Outcomes and Discard Rate of Kidneys by Decade of Extended Criteria Donor Age

BACKGROUND AND OBJECTIVES

Extended criteria donors represent nowadays a main resource for kidney transplantation, and recovery criteria are becoming increasingly inclusive. However, the limits of this approach are not clear as well as the effects of extreme donor ages on long-term kidney transplantation outcomes. To address these issues, we performed a retrospective study on extended criteria donor kidney transplantation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In total, 647 consecutive extended criteria donor kidney transplantations performed over 11 years (2003-2013) were included. Donor, recipient, and procedural variables were classified according to donor age decades (group A, 50-59 years old [n=91]; group B, 60-69 years old [n=264]; group C, 70-79 years old [n=265]; and group D, ≥80 years old [n=27]). Organs were allocated in single- or dual-kidney transplantation after a multistep evaluation including clinical and histologic criteria. Long-term outcomes and main adverse events were analyzed among age groups and in either single- or dual-kidney transplantation. Kidney discard rate incidence and causes were evaluated.

RESULTS

Median follow-up was 4.9 years (25th; 75th percentiles: 2.7; 7.6 years); patient and graft survival were comparable among age groups (5-year patient survival: group A, 87.8%; group B, 88.1%; group C, 88.0%; and group D, 90.1%; P=0.77; graft survival: group A, 74.0%; group B, 74.2%; group C, 75.2%; and group D, 65.9%; P=0.62) and between dual-kidney transplantation and single-kidney transplantation except for group D, with a better survival for dual-kidney transplantation (P=0.04). No difference was found analyzing complications incidence or graft function over time. Kidney discard rate was similar in groups A, B, and C (15.4%, 17.7%, and 20.1%, respectively) and increased in group D (48.2%; odds ratio, 5.1 with A as the reference group; 95% confidence interval, 2.96 to 8.79).

CONCLUSIONS

Discard rate and long-term outcomes are similar among extended criteria donor kidney transplantation from donors ages 50-79 years old. Conversely, discard rate was strikingly higher among kidneys from octogenarian donors, but appropriate selection provides comparable long-term outcomes, with better graft survival for dual-kidney transplantation.

Prediction, prevention, and management of delayed graft function: where are we now?

Delayed graft function (DGF) remains a major barrier to improved outcomes after kidney transplantation. High-risk transplant recipients can be identified, but no definitive prediction model exists. Novel biomarkers to predict DGF in the first hours post-transplant, such as neutrophil gelatinase-associated lipocalin (NGAL), are under investigation. Donor management to minimize the profound physiological consequences of brain death is highly complex. A hormonal resuscitation package to manage the catecholamine "storm" that follows brain death is recommended. Donor pretreatment with dopamine prior to procurement lowers the rate of DGF. Hypothermic machine perfusion may offer a significant reduction in the rate of DGF vs simple cold storage, but costs need to be evaluated. Surgically, reducing warm ischemia time may be advantageous. Research into recipient preconditioning options has so far not generated clinically helpful interventions. Diagnostic criteria for DGF vary, but requirement for dialysis and/or persistent high serum creatinine is likely to remain key to diagnosis until current work on early biomarkers has progressed further. Management centers on close monitoring of graft (non)function and physiological parameters. With so many unanswered questions, substantial reductions in the toll of DGF in the near future seem unlikely but concentrated research on many levels offers long-term promise.

Advances in organ preservation for transplantation

Organ transplantation provides the best available therapy for a myriad of medical conditions, including end-stage renal disease, hepatic failure and type I diabetes mellitus. The current clinical reality is, however, that there is a significant shortage of organs available for transplantation with respect to the number of patients on organ waiting lists. As such, methods to increase organ supply have been instituted, including improved donor management, organ procurement and preservation strategies, living organ donation, transplantation education and the increased utilization of donation after circulatory death and expanded criteria donors. In particular, especially over the last decade, we have witnessed a significant change in the way donor organs are preserved, away from static cold storage methods to more dynamic techniques centred on machine perfusion (MP). This review highlights the current state and future of organ preservation for transplantation, focusing on both abdominal and thoracic organs. In particular, we focus on MP preservation of renal, hepatic, pancreatic, cardiac and lung allografts, also noting relevant advances in Australasia. MP of organs after procurement holds considerable promise, and has the potential to significantly improve graft viability and function post-transplantation, especially in donors in whom acceptance criteria have been expanded.

Protection of the Transplant Kidney from Preservation Injury by Inhibition of Matrix Metalloproteinases

Background

Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, play an important role in ischemic injury to the heart, yet it is not known if these MMPs are involved in the injury that occurs to the transplant kidney. We therefore studied the pharmacologic protection of transplant kidneys during machine cold perfusion.

Methods

Human kidney perfusates were analyzed for the presence of injury markers such as cytochrome c oxidase, lactate dehydrogenase, and neutrophil-gelatinase associated lipocalin (NGAL), and MMP-2 and MMP-9 were measured. The effects of MMP inhibitors MMP-2 siRNA and doxycycline were studied in an animal model of donation after circulatory determination of death (DCDD).

Results

Markers of injury were present in all analyzed perfusates, with higher levels seen in perfusates from human kidneys donated after controlled DCDD compared to brain death and in perfusate from kidneys with delayed graft function. When rat kidneys were perfused at 4°C for 22 hours with the addition of MMP inhibitors, this resulted in markedly reduced levels of MMP-2, MMP-9 and analyzed injury markers.

Conclusions

Based on our study, MMPs are involved in preservation injury and the supplementation of preservation solution with MMP inhibitors is a potential novel strategy in protecting the transplant kidney from preservation injury.

Associations of Perfusate Biomarkers and Pump Parameters With Delayed Graft Function and Deceased Donor Kidney Allograft Function

Hypothermic machine perfusion (HMP) is increasingly used in deceased donor kidney transplantation, but controversy exists regarding the value of perfusion biomarkers and pump parameters for assessing organ quality. We prospectively determined associations between perfusate biomarkers (neutrophil gelatinase-associated lipocalin [NGAL], kidney injury molecule 1, IL-18 and liver-type fatty acid-binding protein [L-FABP]) and pump parameters (resistance and flow) with outcomes of delayed graft function (DGF) and 6-mo estimated GFR (eGFR). DGF occurred in 230 of 671 (34%) recipients. Only 1-h flow was inversely associated with DGF. Higher NGAL or L-FABP concentrations and increased resistance were inversely associated with 6-mo eGFR, whereas higher flow was associated with higher adjusted 6-mo eGFR. Discarded kidneys had consistently higher median resistance and lower median flow than transplanted kidneys, but median perfusate biomarker concentrations were either lower or not significantly different in discarded compared with transplanted kidneys. Notably, most recipients of transplanted kidneys with isolated "undesirable" biomarker levels or HMP parameters experienced acceptable 6-mo allograft function, suggesting these characteristics should not be used in isolation for discard decisions. Additional studies must confirm the utility of combining HMP measurements with other characteristics to assess kidney quality.

Salivary and Urinary Total Antioxidant Capacity as Biomarkers of Oxidative Stress in Humans

Total Antioxidant Capacity (TAC) is a biomarker often used in order to investigate oxidative stress in many pathological conditions. Saliva and urine can be collected noninvasively and represent attractive diagnostic fluids for detecting biomarkers of various pathological conditions. The reviewed case-control and intervention studies that measured salivary or urinary TAC revealed that diseases, antioxidant foods, or supplements and age, gender, and lifestyle factors influenced salivary or urinary TAC. Salivary and urinary TAC were particularly affected by oral or renal status, respectively, as well as by infection; therefore these factors must be taken into account in both case-control and intervention studies. Furthermore, some considerations on sample collection and normalization strategies could be made. In particular, unstimulated saliva could be the better approach to measure salivary TAC, whereas 24 h or spontaneous urine collection should be chosen on the basis of the study outcome and of the creatinine clearance. Finally, the uric acid-independent TAC could be the better approach to evaluate red-ox status of body, in particular after nutritional interventions and in diseases associated with hyperuricaemia.

Donor Hemodynamics as a Predictor of Outcomes After Kidney Transplantation From Donors After Cardiac Death

Donation after cardiac death is an important source of transplantable organs, but evidence suggests donor warm ischemia contributes to inferior outcomes. Attempts to predict recipient outcome using donor hemodynamic measurements have not yielded statistically significant results. We evaluated novel measures of donor hemodynamics as predictors of delayed graft function and graft failure in a cohort of 1050 kidneys from 566 donors. Hemodynamics were described using regression line slopes, areas under the curve, and time beyond thresholds for systolic blood pressure, oxygen saturation, and shock index (heart rate divided by systolic blood pressure). A logistic generalized estimation equation model showed that area under the curve for systolic blood pressure was predictive of delayed graft function (above median: odds ratio 1.42, 95% confidence interval [CI] 1.06-1.90). Multivariable Cox regression demonstrated that slope of oxygen saturation during the first 10 minutes after extubation was associated with graft failure (below median: hazard ratio 1.30, 95% CI 1.03-1.64), with 5-year graft survival of 70.0% (95%CI 64.5%-74.8%) for donors above the median versus 61.4% (95%CI 55.5%-66.7%) for those below the median. Among older donors, increased shock index slope was associated with increased hazard of graft failure. Validation of these findings is necessary to determine the utility of characterizing donor warm ischemia to predict recipient outcome.

Resistance index determination in the pre and post kidney transplantation time points in graft dysfunction diagnosis

BACKGROUND

Donor shortage necessitates the development of tools capable of objectively assessing kidney graft quality from expanded criteria donors and kidneys donated after cardiac death. The deteriorating donor profile is leading to a shift from cold storage toward machine perfusion preservation. Several authors found that renal resistance (RR) at the end of machine perfusion was an independent risk factor for the development of delayed graft function (DGF). In contrast, Doppler ultrasonography in the posttransplant period reveals renal hemodynamics and is useful in diagnosing renal allograft dysfunction. We sought to determine concordance between RR and the resistance index (RI) and their diagnostic value in the assessment of graft viability.

METHODS

RR was determined at the end of perfusion during hypothermic machine preservation and RI was measured by Doppler ultrasonography in the early posttransplant period. Agreement between these 2 measures was established by means of the intraclass correlation coefficient (ICC). Diagnostic validity for RR and RI was determined by sensitivity, specificity and positive and negative predictive values.

RESULTS

The ICC was 0.135, which indicates a slight agreement. RR and RI had limited value in the prediction of DGF for a specific kidney as reflected by a c-statistic of 0.58 and 0.66, respectively.

CONCLUSIONS

There is no agreement between the RR and RI, which may be owing to the different conditions under which measurements are made. The poor predictive power of RR for DGF indicates that kidneys should not be discarded based on RR criteria alone.

Translational research in kidney transplantation and the role of patient engagement

Background

Translational research is an evolving discipline that is intended to bridge the gaps between basic science research, clinical research, and implementation in clinical practice. It is a fluid, multidirectional process that requires strong interdisciplinary collaboration to produce research that is relevant to end-users.

Purpose of this review

This review summarizes current perspectives on translational research and outlines its relevance and importance to kidney transplantation research.

Sources of information

Sources of information used for this review include published reports, articles, and research funding websites.

Findings

Tissue typing is used as an in-depth example of how translational research has been applied in the field of kidney transplant medicine, and how it has resulted in successful implementation of diagnostic and management options for sensitized individuals undergoing kidney transplantation. The value of actively involving kidney transplant stakeholders (patients, caregivers, and clinicians) in setting research priorities and determining relevant outcomes for future investigation is also discussed.

Limitations

This is a narrative review of the literature which has been partly influenced by the perspectives and experiences of its authors.

Implications

Translational and patient-oriented research practices should be incorporated into future research endeavours in the field of kidney transplantation in order to create beneficial change in clinical practice and improve patient outcomes.

What was known before

Translational research which engages patients in the investigative process can enhance the likelihood that medical discoveries will have a meaningful impact at the bedside.

What this adds

This article applies current perspectives on translational research and patient engagement to the field of kidney transplantation, illustrating how these approaches have led to significant advancements in the field. It provides further justification for deliberate, targeted efforts to cross-collaborate and incorporate the patient voice into kidney transplant research.

Recommendations for donation after circulatory death kidney transplantation in Europe

Donation after circulatory death (DCD) donors provides an invaluable source for kidneys for transplantation. Over the last decade, we have observed a substantial increase in the number of DCD kidneys, particularly within Europe. We provide an overview of risk factors associated with DCD kidney function and survival and formulate recommendations from the sixth international conference on organ donation in Paris, for best-practice guidelines. A systematic review of the literature was performed using Ovid Medline, Embase and Cochrane databases. Topics are discussed, including donor selection, organ procurement, organ preservation, recipient selection and transplant management.

New Solutions to Reduce Discard of Kidneys Donated for Transplantation

Kidney transplantation is a cost-saving treatment that extends the lives of patients with ESRD. Unfortunately, the kidney transplant waiting list has ballooned to over 100,000 Americans. Across large areas of the United States, many kidney transplant candidates spend over 5 years waiting and often die before undergoing transplantation. However, more than 2500 kidneys (>17% of the total recovered from deceased donors) were discarded in 2013, despite evidence that many of these kidneys would provide a survival benefit to wait-listed patients. Transplant leaders have focused attention on transplant center report cards as a likely cause for this discard problem, although that focus is too narrow. In this review, we examine the risks associated with accepting various categories of donated kidneys, including discarded kidneys, compared with the risk of remaining on dialysis. With the goal of improving access to kidney transplant, we describe feasible proposals to increase acceptance of currently discarded organs.

Metabolomic analysis of perfusate during hypothermic machine perfusion of human cadaveric kidneys

BACKGROUND

The metabolic processes occurring within the preserved kidney during hypothermic machine perfusion (HMP) are not well characterized. The aim of this study was to use nuclear magnetic resonance (NMR) spectroscopy to examine the metabolomic profile of HMP perfusate from human cadaveric kidneys awaiting transplantation and to identify possible discriminators between the profiles of kidneys with delayed graft function (DGF) and immediate graft function (IGF).

METHODS

Perfusates from HMP kidneys were sampled at 45 min and 4 hr of preservation with the LifePort Kidney Transporter 1.0 (Organ Recovery Systems, Chicago, IL) using KPS-1. Prepared samples underwent 1-D Proton-NMR spectroscopy, and resultant spectra were analyzed. Clinical parameters were collected prospectively.

RESULTS

Perfusate of 26 transplanted cadaveric kidneys was analyzed; 19(73%) with IGF and 7(27%) with DGF. Glucose concentrations were significantly lower in DGF kidneys compared to those with IGF at both 45 min (7.772 vs. 9.459 mM, P = 0.006) and 4 hr (8.202 vs. 10.235 mM, P = 0.003). Concentrations of inosine and leucine were significantly different between DGF and IGF kidneys at 45 min (0.002 vs. 0.013 mM, P = 0.009 and 0.011 vs. 0.006 mM, P = 0.036), and gluconate levels were also significantly different between DGF and IGF kidneys at 4 hr (49.099 vs. 59.513 mM, P = 0.009).

CONCLUSION

Significant metabolic activity may be occurring in kidneys during HMP. The NMR spectroscopy of the perfusate can identify differences in the metabolomic profiles of DGF and IGF kidneys that might have a predictive role in viability assessment. Modification of harmful metabolic processes may improve outcomes for HMP kidneys.

Hypothermic machine perfusion of kidneys retrieved from standard and high-risk donors

Hypothermic machine perfusion (HMP) of kidneys is a long-established alternative to static cold storage and has been suggested to be a better preservation method. Today, as our deceased donor profile continues to change towards higher-risk kidneys of lower quality, we are confronted with the limits of cold storage. Interest in HMP as a preservation technique is on the rise. Furthermore, HMP also creates a window of opportunity during which to assess the viability and quality of the graft before transplantation. The technology might also provide a platform during which the graft could be actively repaired, making it particularly attractive for higher-risk kidneys. We review the current evidence on HMP in kidney transplantation and provide an outlook for the use of the technology in the years to come.

The marginal kidney donor

PURPOSE OF REVIEW

The current era of organ shortage has necessitated a widening of criteria for donation, considering donors who would have been considered unsuitable before. This review summarizes the recent advances in strategies to maximize the use of marginal kidneys without compromising the outcomes.

RECENT FINDINGS

Various strategies have been studied and implemented to optimize procurement and allocation of marginal kidneys, and to preserve their function. In particular, a growing number of transplant centers are using donors after circulatory death. Whereas normothermic ex-vivo and postmortem perfusion are promising procedures to improve the outcomes of marginal grafts in the future, dual-kidney transplantation is a viable approach which is at present potentially underutilized. Despite active research on new strategies to evaluate organ quality, pretransplant biopsy assessment currently remains the most reliable method. The practice of using living donors with advanced age is supported by available evidence, whereas the use of young living donors with minor medical abnormalities needs further investigation.

SUMMARY

Progress has been made in the recent years, clarifying the best criteria for evaluating, recovering, and allocating marginal kidney donors. However, further research is needed, with special regards to the criteria for using marginal living-kidney donors.

Preoperative assessment of the deceased-donor kidney: from macroscopic appearance to molecular biomarkers

Variation in deceased-donor kidney quality can significantly affect outcomes after kidney transplantation. Suboptimal organ selection for a given recipient can result in primary nonfunction, premature graft failure, or inappropriate discard of a suitable organ. Appraisal and appropriate selection of deceased-donor kidneys for use in transplantation is therefore critical. A number of predictive tools have been developed to assist the transplant team in evaluating the suitability of a deceased-donor kidney for transplantation to a given recipient. These include stratification of donors into "standard-" or "expanded-criteria" categories based on clinical parameters, pre-implantation biopsy scores, donor risk scores, machine perfusion characteristics, functional kidney weight, donor biomarkers and molecular diagnostic tools, ex vivo viability assessment using postmortem normothermic perfusion, and overall macroscopic appraisal by the surgical team. Consensus as to the role and predictive value of each of these tools is lacking and clinical practice regarding evaluation and selection of kidneys varies considerably.In this review, we seek to critically appraise the literature and evaluate the levels of evidence for tools used to assess deceased-donor kidneys. Although a plethora of appraisal tools exist, very few demonstrate desirable predictive power to be useful in clinical decision-making. Further research using large, well-designed prospective studies is urgently needed to advance this important field of transplantation science.

Glutathione S-transferase iso-enzymes in perfusate from pumped kidneys are associated with delayed graft function

Accurate and reliable assessment tools are needed in transplantation. The objective of this prospective, multi-center study was to determine the associations of the alpha and pi iso-enzymes of glutathione S-transferase (GST), measured from perfusate solution at the start and end (base and post) of kidney allograft machine perfusion, with subsequent delayed graft function (DGF). We also compared GST iso-enzyme perfusate levels from discarded versus transplanted kidneys. A total of 428 kidneys were linked to outcomes as recorded by the United Network of Organ Sharing. DGF, defined as any dialysis in the first week of transplant, occurred in 141 recipients (32%). Alpha- and pi-GST levels significantly increased during machine perfusion. The adjusted relative risks (95% confidence interval) of DGF with each log-unit increase in base and post pi-GST were 1.14 (1.0-1.3) and 1.36 (1.1-1.8), respectively. Alpha-GST was not independently associated with DGF. There were no significant differences in GST values between discarded and transplanted kidneys, though renal resistance was significantly higher in discarded kidneys. We found pi-GST at the end of machine perfusion to be independently associated with DGF. Further studies should elucidate the utility of GST for identifying injured kidneys with regard to organ allocation, discard and recipient management decisions.

Urine proteomics in kidney transplantation

The transplanted kidney, through its urinary output, provides a medium through which the molecular constitution can provide insight into either the healthy function or developing dysfunction of a newly transplanted organ. An assay that would detect the aberration of early biomarkers of allograft injury using only urine samples from patients would provide many advantages over the current use of creatinine and tissue biopsies, as these means are either relatively non-specific or very invasive. Several urine biomarkers have been correlated with allograft injury, including CXCL9, CXCL10, CCL2, NGAL, IL-18, cystatin C, KIM-1 and Tim-3. The recent results of the CTOT-01 trial serve to validate the predictive value of the CXCL9 biomarker as a non-invasive biomarker for rejection and a prognostic indicator of graft function. There is now a preponderance of evidence showing a value of urinary monitoring of CXCL9 and CXCL10 with respect to detection of acute kidney allograft rejection. The value of the assay has been validated as a means of reducing the need for kidney transplant biopsy and applying biopsy in a more targeted manner. Additional goals for non-invasive monitoring would include predictive value prior to creatinine elevation that in turn would permit earlier, preemptive treatment of rejection.

Oxygen consumption during oxygenated hypothermic perfusion as a measure of donor organ viability

Hypothermic machine perfusion (HMP) for the preservation of kidneys, recovered from extended criteria organ donors (ECDs), presents the opportunity for assessing ex vivo parameters that may have value in predicting postimplantation organ viability. Organ perfusion and vascular resistance are the parameters most frequently cited as the basis for the decision to use or discard a donor kidney. The limitation of these measures is emphasized by the observation that a significant percentage of ECD kidneys with poor perfusion parameters can provide life-sustaining function after transplantation. It has been suggested that whole organ oxygen consumption (OC) during oxygenated HMP may better reflect the proportion of viable tissue in the organ and more reliably predict posttransplant organ function. Our study correlates renal OC and renal vascular resistance (RVR) during oxygenated HMP with postpreservation glomerular filtration rates (GFRs) in rodent kidneys after 24 hours of oxygenated HMP. Kidneys from adult rodents were preserved for 24 hours using oxygenated HMP and static cold storage (SCS). During oxygenated HMP preservation, organ OC, renal organ flow rates, and RVR were serially measured. After the preservation period, organs were mounted onto a Langendorff device for warming to normal body temperature and measurement of GFR. Oxygen consumption and RVR during HMP were correlated with postpreservation GFR. Oxygen consumption during oxygenated HMP was significantly correlated (r2 = 0.871; p < 0.05) with postpreservation GFR, suggesting that higher OC predicts better postpreservation GFR. In contrast, RVR was poorly correlated with postpreservation GFR (r2 = 0.258; p = 0.199). Glomerular filtration rate in SCS kidneys was 0.002 ± 0.003 ml/min/g. We demonstrate that measurement of organ OC during oxygenated HMP may have significant value in predicting postpreservation organ function.

Machine perfusion viability testing

PURPOSE OF REVIEW

Pretransplant assessment of kidney graft viability may help clinicians to decide whether to accept or discard a kidney for transplantation. With the increasing demand for donor kidneys and the increased use of marginal kidneys, the need of viability markers has increased to pursue superior transplant outcomes. Hypothermic machine perfusion (HMP) provides the theoretical opportunity to assess the viability of donor kidneys. We discuss the novel developments in viability testing during HMP and address the future prospects.

RECENT FINDINGS

HMP viability testing has focused on the analysis of machine perfusion parameters and perfusate biomarkers. Renal resistance and the biomarkers lactate dehydrogenase, aspartate transaminase, glutathione-S-transferase, N-acetyl-β-D-glucosaminidase, heart-type fatty acid binding protein, lipid peroxidation products, redox-active iron and IL-18 are correlated with transplant outcome in terms of development of delayed graft function or graft survival. However, they all lack adequate predictive value for transplant outcome. New techniques including contrast-enhanced ultrasound, three-dimensional ultrasound and magnetic resonance spectrometry are promising methods to test kidney viability during HMP, but their value has to be established. The introduction of normothermic machine perfusion offers other promising opportunities for viability testing.

SUMMARY

Machine perfusion characteristics and perfusate biomarkers have been extensively studied. They often correlate with the transplant outcome, but the present viability tests are not reliable predictors of transplant outcome. New developments in kidney graft viability assessment are necessary to have a chance of being clinically useful in the future.

Comparison of Serum and Urine Neutrophil Gelatinase-Associated Lipocalin (NGAL) With Serum Creatinine in Prediction of Kidney Suitability for Transplantation

Background

When using brain dead donors for organ donation, assessment of kidney function before the procedure is essential.

Objectives

It would be ideal to find an early marker of viability of donor kidneys that is more accurate than creatinine.

Patients and Methods

The present study was conducted from March of 2011 to March of 2012, included 52 deceased donors. Serum and urinary Neutrophil Gelatinase Associated Lipocalin (NGAL) and creatinine were measured at 0, 2, 4, 8, 12 and 18 hours after their admission to the ICU of our organ procurement unit (OPU). Other routine laboratory tests of hemglobin, blood glucose and lipid profile were performed as well.

Results

There were 31 males and 21 females with the mean age of 29.7 ± 14.3 (6-58) years. Thirty one patients became brain dead due to car accidents. The mean time of admission time before harvest was 12.6 ± 5.8 (3-30) hours. We did not discover any correlation of serum creatinine with serum or urinary NGAL at any time before the organ harvesting. However, serum NGAL level measurement 2 hours after admission correlated significantly with other hours' measurements (4, 6, 8 hours, r > 0.9; P < 0.001).

Conclusions

The serum NGAL level, especially at 2 hours after admission to the ICU, should be evaluated with kidney function after transplantation to get the accurate predictive value.