Graft quality assessment in kidney transplantation: not an exact science yet!

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.

Experimental long-term sub-normothermic machine perfusion for non-allocable human liver grafts: first data towards feasibility

Background

Patients with end-stage liver disease can only be cured by liver transplantation. Due to the gap between demand and supply, surgeons are forced to use expanded criteria donor (ECD) organs, which are more susceptible to ischemia–reperfusion injury (IRI). Therefore, enhanced storing techniques are required. Machine perfusion (MP) has moved into the spotlight of research because of its feasibility for investigating liver function prior to implantation. However, as the perfect MP protocol has not yet been found, we aimed to investigate the potential of sub-normothermic (SN)MP in this field.

Methods

Non-allocable human livers were subjected to 24 h of SNMP at 21 °C after delivery to the study team. Perfusion was performed with Custodiol® (Dr. Franz Köhler Chemie, Bensheim, Germany) or Belzer MPS® (Bridge to Life Europe, London, UK) and perfusate liver parameters were determined. For determination of biliary conditions, pH, glucose, and HCO3- levels were measured.

Results

Liver parameters were slightly increased irrespective of perfusate or reason for liver rejection during 24 h of perfusion. Six livers failed to produce bile completely, whereas the remaining 10 livers produced between 2.4 ml and 179 ml of bile. Biliary carbonate was increased in all but one liver. The bile-glucose-to-perfusate-glucose ratio was near 1 for most of the organs and bile pH was above 7 in all but one case.

Conclusion

This study provides promising data on the feasibility of long-term SNMP as a tool to gain time during MP to optimize ECD organs to decrease the gap between organ demand and supply.

Long-term (24 h) sub-normothermic liver machine perfusion seems to be possible, although some adjustments to the protocol might be necessary to improve the general outcome. This has so far been shown for normothermic machine perfusion, bearing some drawbacks compared to the sub-normothermic variant.

Deceased-Donor Kidney Biopsy Scoring Systems for Predicting Future Graft Function: A Comparative Study

BACKGROUND

Deceased-donor kidney quality pretransplantation is considered critical for future graft function. Assessment of donor kidney quality considers clinical and histologic variables. Several models that incorporate a variety of these factors have been proposed to predict long-term graft survival.

METHODS

We compared the performance metrics of 4 scoring systems models---the Maryland Aggregate Pathology Index, Banff, Remuzzi, and Leuven---for predicting renal allograft survival. In this retrospective cohort study, we analyzed 173 renal allografts that underwent preoperative baseline biopsy. Donor demographics and donor baseline histopathology data were collected and correlated with graft survival posttransplant.

RESULTS

Among the 4 scoring systems, none were significantly associated with posttransplant graft survival or early graft function. The Maryland Aggregate Pathology Index scoring system had better predictive capacity in receiver operating characteristic curve analysis; however, the utility as a predictor of graft survival was only slightly better than chance. Baseline histologic features were individually analyzed, and it was found that none were associated with graft survival in this cohort. Among donor demographics, none were significantly associated with graft survival.

CONCLUSIONS

In our study none of the 4 previously proposed predictive models were associated with graft survival after transplantation. Further studies are needed to define new models with stronger predictive value for graft outcome that could help minimize organ discards.

Perfusate Analysis During Dual Hypothermic Oxygenated Machine Perfusion of Liver Grafts: Correlations With Donor Factors and Early Outcomes

BACKGROUND

Liver graft viability assessment has long been considered a limit of hypothermic oxygenated machine perfusion (HOPE). Aim of this study was assessing correlations of easily available perfusate parameters (PP) (aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, glucose, lactate, and pH) with graft features and outcome.

METHODS

In the period October 2018-February 2020, perfusate samples were obtained every 30 minutes during 50 dual-HOPE (D-HOPE) procedures. Correlations of PP with graft factors, 90-day graft loss, early allograft dysfunction (EAD), L-GrAFT score, acute kidney injury, and comprehensive complication index were analyzed using Pearson coefficient, receiver-operating characteristics analysis and by univariable and multivariable regression.

RESULTS

Median D-HOPE time was 122 minutes. All parameters were normalized to liver weight. Only macrovesicular steatosis (MaS) significantly impacted PP levels and slope. Grafts with ≥30% MaS exhibited significantly different PP values and slope. Graft loss and EAD rate were 2% (n = 1) and 26% (n = 13). All PP except lactate correlated with EAD, 90-minute alanine aminotransferase showing the highest area under the receiver-operating characteristics curve (0.84). However, at multivariable analysis, the only factor independently associated with EAD was MaS (odds ratio, 5.44; confidence interval, 1.05-28.21; P = 0.04). Ninety minutes lactate dehydrogenase had the strongest correlation with L-GrAFT (R = 0.70; P < 0.001). PP correlated poorly with comprehensive complication index and grades 2-3 acute kidney injury rate.

CONCLUSIONS

PP were predictive of graft function after transplant, but their association with graft survival and clinical outcomes requires further evaluation. MaS influenced levels of PP and was the only independent predictor of EAD.

Urinary Biomarkers for Diagnosis and Prediction of Acute Kidney Allograft Rejection: A Systematic Review

Noninvasive tools for diagnosis or prediction of acute kidney allograft rejection have been extensively investigated in recent years. Biochemical and molecular analyses of blood and urine provide a liquid biopsy that could offer new possibilities for rejection prevention, monitoring, and therefore, treatment. Nevertheless, these tools are not yet available for routine use in clinical practice. In this systematic review, MEDLINE was searched for articles assessing urinary biomarkers for diagnosis or prediction of kidney allograft acute rejection published in the last five years (from 1 January 2015 to 31 May 2020). This review follows the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Articles providing targeted or unbiased urine sample analysis for the diagnosis or prediction of both acute cellular and antibody-mediated kidney allograft rejection were included, analyzed, and graded for methodological quality with a particular focus on study design and diagnostic test accuracy measures. Urinary C-X-C motif chemokine ligands were the most promising and frequently studied biomarkers. The combination of precise diagnostic reference in training sets with accurate validation in real-life cohorts provided the most relevant results and exciting groundwork for future studies.

Assessment of Organ Quality in Kidney Transplantation by Molecular Analysis and Why It May Not Have Been Achieved, Yet

Donor organ shortage, growing waiting lists and substantial organ discard rates are key problems in transplantation. The critical importance of organ quality in determining long-term function is becoming increasingly clear. However, organ quality is difficult to predict. The lack of good measures of organ quality is a serious challenge in terms of acceptance and allocation of an organ. The underlying review summarizes currently available methods used to assess donor organ quality such as histopathology, clinical scores and machine perfusion characteristics with special focus on molecular analyses of kidney quality. The majority of studies testing molecular markers of organ quality focused on identifying organs at risk for delayed graft function, yet without prediction of long-term graft outcome. Recently, interest has emerged in looking for molecular markers associated with biological age to predict organ quality. However, molecular gene sets have not entered the clinical routine or impacted discard rates so far. The current review critically discusses the potential reasons why clinically applicable molecular quality assessment using early kidney biopsies might not have been achieved yet. Besides a critical analysis of the inherent limitations of surrogate markers used for organ quality, i.e., delayed graft function, the intrinsic methodological limitations of studies assessing organ quality will be discussed. These comprise the multitude of unpredictable hits as well as lack of markers of nephron mass, functional reserve and regenerative capacity.

Transplanting Marginal Organs in the Era of Modern Machine Perfusion and Advanced Organ Monitoring

Organ transplantation is undergoing profound changes. Contraindications for donation have been revised in order to better meet the organ demand. The use of lower-quality organs and organs with greater preoperative damage, including those from donation after cardiac death (DCD), has become an established routine but increases the risk of graft malfunction. This risk is further aggravated by ischemia and reperfusion injury (IRI) in the process of transplantation. These circumstances demand a preservation technology that ameliorates IRI and allows for assessment of viability and function prior to transplantation. Oxygenated hypothermic and normothermic machine perfusion (MP) have emerged as valid novel modalities for advanced organ preservation and conditioning. Ex vivo prolonged lung preservation has resulted in successful transplantation of high-risk donor lungs. Normothermic MP of hearts and livers has displayed safe (heart) and superior (liver) preservation in randomized controlled trials (RCT). Normothermic kidney preservation for 24 h was recently established. Early clinical outcomes beyond the market entry trials indicate bioenergetics reconditioning, improved preservation of structures subject to IRI, and significant prolongation of the preservation time. The monitoring of perfusion parameters, the biochemical investigation of preservation fluids, and the assessment of tissue viability and bioenergetics function now offer a comprehensive assessment of organ quality and function ex situ. Gene and protein expression profiling, investigation of passenger leukocytes, and advanced imaging may further enhance the understanding of the condition of an organ during MP. In addition, MP offers a platform for organ reconditioning and regeneration and hence catalyzes the clinical realization of tissue engineering. Organ modification may include immunological modification and the generation of chimeric organs. While these ideas are not conceptually new, MP now offers a platform for clinical realization. Defatting of steatotic livers, modulation of inflammation during preservation in lungs, vasodilatation of livers, and hepatitis C elimination have been successfully demonstrated in experimental and clinical trials. Targeted treatment of lesions and surgical treatment or graft modification have been attempted. In this review, we address the current state of MP and advanced organ monitoring and speculate about logical future steps and how this evolution of a novel technology can result in a medial revolution.

Kidney Perfusion as an Organ Quality Assessment Tool-Are We Counting Our Chickens Before They Have Hatched?

The final decision to accept an organ for transplantation remains a subjective one. With “poor organ quality” commonly cited as a major reason for kidney discard, accurate, objective, and reliable quality assessment is essential. In an era of increasingly higher-risk deceased donor kidneys, the catch is to accept those where the risk–benefit scale will tip in the right direction. Currently available assessment tools, such as risk-scores predicting outcome and zero-time biopsy, perform unsatisfactory, and assessment options during static cold storage are limited. Kidney perfusion technologies are finding their way into clinical practice, and they bring a new opportunity to assess kidney graft viability and quality, both in hypothermic and normothermic conditions. We give an overview of the current understanding of kidney viability assessment during ex situ kidney perfusion. A pragmatic framework to approach viability assessment is proposed as an interplay of three different compartments: the nephron, the vascular compartment, and the immune compartment. Although many interesting ways to assess kidney injury and function during perfusion have been proposed, none have reached the stage where they can reliably predict posttransplant outcome. Larger well-designed studies and validation cohorts are needed to provide better guidance.

Deep Learning Global Glomerulosclerosis in Transplant Kidney Frozen Sections

Transplantable kidneys are in very limited supply. Accurate viability assessment prior to transplantation could minimize organ discard. Rapid and accurate evaluation of intra-operative donor kidney biopsies is essential for determining which kidneys are eligible for transplantation. The criterion for accepting or rejecting donor kidneys relies heavily on pathologist determination of the percent of glomeruli (determined from a frozen section) that are normal and sclerotic. This percentage is a critical measurement that correlates with transplant outcome. Inter- and intra-observer variability in donor biopsy evaluation is, however, significant. An automated method for determination of percent global glomerulosclerosis could prove useful in decreasing evaluation variability, increasing throughput, and easing the burden on pathologists. Here, we describe the development of a deep learning model that identifies and classifies non-sclerosed and sclerosed glomeruli in whole-slide images of donor kidney frozen section biopsies. This model extends a convolutional neural network (CNN) pre-trained on a large database of digital images. The extended model, when trained on just 48 whole slide images, exhibits slide-level evaluation performance on par with expert renal pathologists. Encouragingly, the model's performance is robust to slide preparation artifacts associated with frozen section preparation. The model substantially outperforms a model trained on image patches of isolated glomeruli, in terms of both accuracy and speed. The methodology overcomes the technical challenge of applying a pretrained CNN bottleneck model to whole-slide image classification. The traditional patch-based approach, while exhibiting deceptively good performance classifying isolated patches, does not translate successfully to whole-slide image segmentation in this setting. As the first model reported that identifies and classifies normal and sclerotic glomeruli in frozen kidney sections, and thus the first model reported in the literature relevant to kidney transplantation, it may become an essential part of donor kidney biopsy evaluation in the clinical setting.

MicroRNAs in Kidney Machine Perfusion Fluid as Novel Biomarkers for Graft Function. Normalization Methods for miRNAs Profile Analysis

MicroRNAs (miRNAs) are post-transcriptional regulators that have emerged as promising biomarkers in kidney transplantation. Quantification of miRNAs can be analyzed by means of biological normalization. The purpose of normalization is to remove technical variation in data, which is not related to the biological changes under investigation. Proper normalization is critical for the correct analysis and interpretation of results.

MATERIAL AND METHODS

A prospective cohort study was conducted on graft dysfunction in kidney transplantation from expanded criteria donors. After RNA extraction quantitative real-time polymerase chain reaction was performed. The exogenous spike-in normalization was used as technical normalization. Relative expression was calculated using the 2-ΔΔCt method and UniSp2 spike-in was used as reference for normalization. Results obtained were further analyzed by the application of the mean expression value that uses the calculated mean of all miRNAs in a given sample.

RESULTS

The mean expression value approach confirmed the significance of a subset of the miRNAs previously identified for delayed graft function development and composed by miRNAs miR-486-5p, miR-144-3p, miR-142-5p, and miR-144-5p.

CONCLUSIONS

MicroRNAs are becoming increasingly important as biomarkers in multiple disease processes including kidney transplantation. Perfusion fluid, particularly during hypothermic machine perfusion, provides a valuable pretransplantation source for identification of organ viability biomarkers. Although there is no clear consensus concerning the normalization technique, the mean expression value method shows the better normalization strategy.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Past, Present, and Future of Dynamic Kidney and Liver Preservation and Resuscitation

The increased demand for organs has led to the increased usage of "higher risk" kidney and liver grafts. These grafts from donation after circulatory death or expanded criteria donors are more susceptible to preservation injury and have a higher risk of unfavorable outcomes. Dynamic, instead of static, preservation could allow for organ optimization, offering a platform for viability assessment, active organ repair and resuscitation. Ex situ machine perfusion and in situ regional perfusion in the donor are emerging as potential tools to preserve and resuscitate vulnerable grafts. Preclinical findings have ignited clinical organ preservation research that investigates dynamic preservation, its various modes (continuous, preimplantation) and temperatures (hypo-, sub, or normothermic). This review outlines the current status of dynamic preservation of kidney and liver grafts and describes ongoing research and emerging clinical trials.

YKL-40 Associates with Renal Recovery in Deceased Donor Kidney Transplantation

Deceased donor kidneys with AKI are often discarded for fear of poor transplant outcomes. Donor biomarkers that predict post-transplant renal recovery could improve organ selection and reduce discard. We tested whether higher levels of donor urinary YKL-40, a repair phase protein, associate with improved recipient outcomes in a prospective cohort study involving deceased kidney donors from five organ procurement organizations. We measured urinary YKL-40 concentration in 1301 donors (111 had AKI, defined as doubling of serum creatinine) and ascertained outcomes in the corresponding 2435 recipients, 756 of whom experienced delayed graft function (DGF). Donors with AKI had higher urinary YKL-40 concentration (P<0.001) and acute tubular necrosis on procurement biopsies (P=0.05). In fully adjusted analyses, elevated donor urinary YKL-40 concentration associated with reduced risk of DGF in both recipients of AKI donor kidneys (adjusted relative risk, 0.51 [95% confidence interval (95% CI), 0.32 to 0.80] for highest versus lowest YKL-40 tertile) and recipients of non-AKI donor kidneys (adjusted relative risk, 0.79 [95% CI, 0.65 to 0.97]). Furthermore, in the event of DGF, elevated donor urinary YKL-40 concentration associated with higher 6-month eGFR (6.75 [95% CI, 1.49 to 12.02] ml/min per 1.73 m²) and lower risk of graft failure (adjusted hazard ratio, 0.50 [95% CI, 0.27 to 0.94]). These findings suggest that YKL-40 is produced in response to tubular injury and is independently associated with recovery from AKI and DGF. If ultimately validated as a prognostic biomarker, urinary YKL-40 should be considered in determining the suitability of donor kidneys for transplant.

Decision Making by Young Transplant Surgeons Regarding Expanded-Criteria Donors With Acute Kidney Injury or Allocation Failure

BACKGROUND

The utilization of expanded-criteria donors (ECDs) has increased to overcome donor shortages. Unfortunately, the discard rate has also increased, especially in ECDs with acute kidney injury (AKI). We evaluated the outcomes of kidney transplantation in ECDs and standard-criteria donors (SCDs) with and without AKI.

METHODS

We reviewed the medical records of patients who underwent kidney transplantation. We used the AKI definition published by the Kidney Disease: Improving Global Outcomes group and reviewed the demographic characteristics of donors and recipients. We analyzed transplantation outcomes.

RESULTS

Twenty-seven patients underwent kidney transplantation from ECDs with AKI (n = 6) or without AKI (n = 5) and SCDs with AKI (n = 6) or without AKI (n = 10). Initial creatinine and estimated glomerular filtration rate (eGFR) were not significantly different between the groups. The incidence of delayed graft function was highest in ECDs with AKI (n = 3; 36.4%), but this was not a significantly difference. There was no difference in the last creatinine and eGFR in ECDs with AKI (1.32 mg/dL, 58.7 mL/min/1.73 m(2)), ECDs without AKI (1.67 mg/dL, 44.2 mL/min/1.73 m(2)), SCDs with AKI (0.94 mg/dL, 81.5 mL/min/1.73 m(2)) and SCDs without AKI (0.97 mg/dL, 81.8 mL/min/1.73 m(2)).

CONCLUSIONS

As the donor pool is extended to ECDs, young transplant surgeons may increasingly face decisions regarding ECDs with AKI or allocation failure. There is no consensus regarding discard criteria. However, if the donor showed initially normal creatinine levels or if dual-kidney transplantation can be performed, young transplant surgeons should not hesitate to use ECDs with AKI or allocation failure.

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.

Chinese Pediatric Organ Donation With Scheduled Cardiac Arrest After Brain Death: A Novel China Classification Beyond Maastricht

OBJECTIVE

Organ donation with scheduled cardiac arrest after brain death (s-DBCD) is a special category in China. This study was to evaluate the procedure of pediatric s-DBCD, graft quality, and clinical outcomes of single kidney transplantation.

METHODS

We retrospectively analyzed the data of 8 Chinese pediatric donors.

RESULTS

The death causes of the donors (age 4-12 years) were cerebral hypoxia after cardiopulmonary resuscitation (n = 1), intracranial vascular malformation (n = 1), severe traumatic brain injury (n = 3), and brain malignancy (n = 3). The functional warm ischemia time of the grafts was 18 (13-26) minutes. Sixteen kidneys were recovered using liver-kidney en bloc procurement after in situ perfusion. All kidneys had a length >7 cm and were transplanted to 3 adolescent and 13 adult recipients. Two cases of delayed graft function occurred. The patients had a median serum creatinine level of 97 (55-123) μmol/L by the last visit. The median estimated glomerular filtration rate level was 85.4 (58-136) mL/min. Five episodes of biopsy-proven acute rejection occurred in 4 patients, which were reversed by methylprednisolone pulse therapy. Renal arterial stenosis was observed in 1 patient, which was cured by interventional balloon dilatation and stent implantation.

CONCLUSION

Pediatric s-DBCD is feasible with acceptable graft quality. Single kidney transplantation with pediatric graft size >7 cm has good clinical outcomes.

High-Resolution Imaging Using the VisualSonics Vevo 2100 on Isolated, Perfused Porcine Kidneys on Mechanical Circulatory Support

Despite many improvements in the field of renal transplantation, the key problem that persists is the lack of organs for all the patients who need kidneys. This problem continues despite the addition of extended criteria donors and donation after cardiac death. Compounding this issue is the high discard rate and there are no good means to truly predict renal function using current pretransplantation testing parameters. In an isolated renal perfusion model using porcine kidneys, we tested the proof of principle that a Vevo 2100 high-frequency high-resolution ultrasound system (Fujifilm VisualSonics, Inc., Toronto, Canada) could assess renal parenchymal perfusion and flow in the central renal vessels which could not assess by conventional ultrasound. Images and velocities were easily obtained during these studies. High-frequency ultrasound imaging may be a feasible and reproducible method for assessing renal parenchymal integrity and function pretransplantation. Further studies are required to determine the sensitivity and specificity of this approach in comparison with traditional renal biopsy pretransplantation with the goal of increasing the identification and use of donated kidneys for transplantation.

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.

A single-center experience with 200 dual kidney transplantations

This study reports on a large series of 200 dual kidney transplantations (DKTs) from expanded criteria donors (ECDs) and proposes specific ways to optimize outcomes. Data concerning 200 DKTs performed in the last 14 yr were retrospectively analyzed. Kidneys from high-risk ECD were allocated for use in DKTs on an old-for-old basis after histological assessment. Different surgical techniques and immunosuppressant regimens were used over time, and the outcomes are discussed. Donors and recipients were a median 73 (70-77) and a 62 (58-67) yr old, respectively. Delayed graft function occurred in 31.5% of cases, and acute rejection in 13.5%. Patient and graft survival at five yr were 90.4% and 85.8%, respectively. Unilateral kidney placement was preferred for 75% of patients, and was associated with a low rate of surgical complications. Our current standard therapy comprising low-dose calcineurin inhibitors (CNIs) associated with mammalian target of rapamycin inhibitors (mTOR) and steroids appears to offer the best risk/benefit profile for elderly patients undergoing DKT. In our experience, outcomes after DKT can be improved by: (i) kidney clinical-histological assessment; (ii) unilateral kidney placement; (iii) minimal use of CNI associated with mTOR.

Neutrophil gelatinase-associated lipocalin, a new biomarker candidate in perfusate of machine-perfused kidneys: a porcine pilot experiment

The enduring kidney graft shortage has led to the increasing use of expanded-criteria donors as well as kidneys donated after cardiac death, triggering the revival of machine perfusion preservation. Indeed, machine perfusion not only preserves these kidneys better than static cold storage, but also has the potential to evaluate them. The presence of certain biomarkers, among them aspartate aminotransferase (AST) and heart-type fatty acid binding protein (H-FABP), has been demonstrated in the perfusate of human kidneys, making them potentially useful as biomarkers of graft quality. Neutrophil gelatinase-associated lipocalin (NGAL) which is believed to be released upon renal tubular cell injury is another biomarker candidate. However, because it is also released from neutrophils, it is currently unclear whether NGAL is a direct or indirect, inflammatory-mediated marker of kidney injury. To resolve this issue we established a pilot experiment to study the concentrations of AST, H-FABP, and NGAL in the perfusates of 6 porcine kidneys that were exposed to incremental periods of warm ischemia before machine perfusion for 22 hours. An ex vivo porcine model was chosen because preclinical large animal work remains necessary to refine machine perfusion technology and because the presence of these markers in perfusates of porcine kidneys had not been shown previously. All 3 biomarkers were detectable in the cold acellular perfusate; their release seemed to be proportionate to the degree of warm injury, albeit that this must be confirmed in a larger sample. In conclusion, NGAL is directly released by ischemically damaged kidneys, independent of neutrophil activation. In addition to NGAL, the determination of AST and H-FABP in perfusates of machine-perfused porcine kidneys is also feasible. Determination of these markers may be added to the arsenal of research tools for preclinical preservation research.

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.

Kidney donor risk index is a good prognostic tool for graft outcomes in deceased donor kidney transplantation with short, cold ischemic time

BACKGROUND

We performed a retrospective cohort study to determine the prognostic value of standard criteria donor/expanded criteria donor (SCD/ECD) designation, with regard to one-yr GFR and graft survival rate, in a region with short, cold ischemic time (CIT), and how this designation compares with the kidney donor risk index (KDRI) and zero-time kidney biopsies.

METHODS

We reviewed 362 cases of deceased donor kidney transplantation (DDKT). Donor kidneys were classified as SCD or ECD. They were also assessed by the KDRI. Zero-time kidney biopsy was performed in 196 patients, and histologic score was assessed.

RESULTS

Median follow-up duration was 46 months. Forty-two cases (11.6%) used ECD kidneys. The mean CIT was only 4.9 ± 2.7 h. Graft survival rates were not significantly different between ECD and SCD groups. The KDRI showed the best correlation with one-yr estimations of glomerular filtration rate (eGFR) (R(2) = 0.230, p < 0.001), and higher KDRI was associated with a higher risk of graft failure (hazard ratio 2.63, 95% confidence interval 1.01-6.87). However, higher histologic score was not associated with a higher risk of graft failure.

CONCLUSION

KDRI has greater predictive value for short-term outcomes in DDKT with short CIT than the SCD/ECD designation or pathology.

Machine perfusion in solid organ transplantation: where is the benefit?

BACKGROUND

Machine perfusion (MP) in solid organ transplantation has been a topic of variable importance for decades. At the dawn of organ transplantation, MP was one of the standard techniques for preservation; today's gold standard for organ preservation for transplantation is cold storage (CS). The outcome after transplantation of solid organs has tremendously improved over the last five decades. MP has been continuously under investigation and may be an option for organ preservation in selected cases; however, there is only little evidence from clinical trials that can be used to advocate for MP as a routine organ preservation method.

METHODS

This article reviews the current knowledge on MP in the field of solid organ transplantation with special focus on findings from clinical trials.

CONCLUSION

Especially in heart and lung transplantation, MP seems to be a promising tool to improve postoperative outcome, but a general evidence-based recommendation for or against an application of MP cannot be given due to the lack of the highest level of clinical evidence. Gold standards such as CS should not be left behind without good reason. Randomized clinical trials are desperately needed to further improve outcome and for better understanding of the underlying pathophysiological mechanisms.

The predictive value of kidney allograft baseline biopsies for long-term graft survival

The effect of baseline histology and individual histologic lesions at the time of transplantation on long-term graft survival has been evaluated using different scoring systems, but the predictive capacity of these systems has not been adequately validated. All kidney recipients transplanted in a single institution between 1991 and 2009 who underwent a baseline kidney allograft biopsy at transplantation were included in this prospective study (N=548). All baseline biopsies were rescored according to the updated Banff classification, and the relationship between the individual histologic lesions and donor demographics was assessed using hierarchical clustering and principal component analysis. Survival analysis was performed using Cox proportional hazards analysis and log-rank testing. Mean follow-up time was 6.7 years after transplantation. Interstitial fibrosis, tubular atrophy, and glomerulosclerosis associated significantly with death-censored graft survival, whereas arteriolar hyalinosis and vascular intimal thickening did not. Notably, donor age correlated significantly with interstitial fibrosis, tubular atrophy, and glomerulosclerosis and associated independently with graft survival. On the basis of these findings, a novel scoring system for prediction of 5-year graft survival was constructed by logistic regression analysis. Although the predictive performance of previously published histologic scoring systems was insufficient to guide kidney allocation in our cohort (receiver operating characteristic area under the curve ≤0.62 for each system), the new system based on histologic data and donor age was satisfactory for prediction of allograft loss (receiver operating characteristic area under the curve = 0.81) and may be valuable in the assessment of kidney quality before transplantation.

Assessment of donor biopsies

PURPOSE OF REVIEW

To provide an up-to-date overview about the assessment of donor biopsies and to discuss the current problems and chances of preimplantation biopsies for transplant allocation with a focus on the technical work up and the histological variables scored.

RECENT FINDINGS

Preimplantation biopsy results are the major reason for discarding procured extended donor criteria kidneys in the USA. There is neither a consensus on the work up, nor the reporting of preimplantation donor biopsies, nor the importance of the biopsy findings in the process of allocation. The best available data have been collected in the context of single vs. double kidney transplantation. A clinical risk factor score may help to define kidneys when a preimplantation biopsy is warranted. Punch biopsies using a skin punch device appear to be a reasonable alternative for surgeons fearing needle biopsies.

SUMMARY

Donor biopsies are very useful as zero-hour biopsies establishing baseline information for comparison with subsequent transplant biopsies. As none of the histological variables and scores provides perfect prediction, preimplantation biopsy results have to be interpreted in the context of all available donor and recipient information.

Optimizing utilization of kidneys from deceased donors over 60 years: five-year outcomes after implementation of a combined clinical and histological allocation algorithm

This 5 year observational multicentre study conducted in the Nord Italian Transplant programme area evaluated outcomes in patients receiving kidneys from donors over 60 years allocated according to a combined clinical and histological algorithm. Low-risk donors 60-69 years without risk factors were allocated to single kidney transplant (LR-SKT) based on clinical criteria. Biopsy was performed in donors over 70 years or 60-69 years with risk factors, allocated to Single (HR-SKT) or Dual kidney transplant (HR-DKT) according to the severity of histological damage. Forty HR-DKTs, 41 HR-SKTs and 234 LR-SKTs were evaluated. Baseline differences generally reflected stratification and allocation criteria. Patient and graft (death censored) survival were 90% and 92% for HR-DKT, 85% and 89% for HR-SKT, 88% and 87% for LR-SKT. The algorithm appeared user-friendly in daily practice and was safe and efficient, as demonstrated by satisfactory outcomes in all groups at 5 years. Clinical criteria performed well in low-risk donors. The excellent outcomes observed in DKTs call for fine-tuning of cut-off scores for allocation to DKT or SKT in high-risk patients.

Machine perfusion in organ transplantation: a tool for ex-vivo graft conditioning with mesenchymal stem cells?

PURPOSE OF REVIEW

Machine perfusion has emerged as a tool to evaluate pretransplant graft function more objectively during preservation. Machine perfusion also offers the possibility to recondition questionable organs and to 'immunomodulate' allografts ex vivo. This article aims to review the current knowledge on machine perfusion of the various solid thoracic and abdominal organs, and to discuss the new possibility of conditioning and treating grafts with mesenchymal stem cells (MSCs) during machine perfusion.

RECENT FINDINGS

Different methods of machine perfusion have been described varying among organs in temperature and composition of perfusate. Commercial devices have recently become available for machine perfusion of all organs, with the largest clinical experience acquired in kidney and lung transplantation. Clinical studies are ongoing for liver, heart, and pancreas. MSC therapy in organ transplantation is now emerging with clinical studies set up to investigate its potential to attenuate ischemia/reperfusion injury (innate immunity) and to downregulate the alloimmune response (adaptive immunity) and promote engraftment after transplantation. We hypothesize that delivery of MSCs directly into the machine perfusion circuit may provide a unique opportunity to treat and immunomodulate organs prior to transplantation. To our knowledge, no study on ex-vivo delivery of MSCs during machine perfusion has been reported.

SUMMARY

Machine perfusion of solid organs has regained much attention during the last decade. It provides a new promising tool that may allow pretransplant ex-vivo assessment, preservation, repair, and conditioning of grafts. Experimental research and clinical trials testing the administration of MSCs during machine perfusion are warranted to explore the potential benefit and mechanisms of this approach.

Optimization of expanded donors using dual kidney transplantation: case-control study

BACKGROUND

Cadaveric donation is now experiencing a trend toward the use of expanded criteria donors (ECD) who may not yield a suitable kidney for single organ transplantation which has occasionally led to their use as dual renal transplantations.

MATERIAL AND METHODS

We undertook a case-control study to analyze our experiences between May 2007 and March 2011 with 80 kidneys from ECD who were older than 65 years. Of these, 40 were used as single transplants (STX) and the other 40 as dual cases (DTX). Criteria to determine STX versus DTX were established by biopsy results and other donor factors.

RESULTS

The mean age of the ECD for STX was 68.7 ± 3.0 years and for DTX, 74.2 ± 4.3 years (P < .001), with more women among DTX (75%) versus STX (40%; P < .001). The DTX kidneys showed higher biopsy scores than the STX organs. DTX were older than STX recipients, but there were no differences in cold ischemia time, delayed graft function, hemorrhagic complications or reinterventions. DTX recipients achieved better CrCl at 1, 3, 6, and 12 months, although only significantly so at 6 months (53.4 ± 19.5 Ml/min versus 44.5 ± 15.6 mL/min; P < .05). Death-censored graft survival was 90% at 3 years for both groups.

CONCLUSIONS

DTX offered good results for graft survival and renal function, despite the more complicated surgery and worse quality of the allografts. DTX allowed the use of ECD kidneys that showed less satisfactory histologic and donor characteristics.

Prognostic utility of hypothermic machine perfusion in deceased donor renal transplantation

Pulsatile pump perfusion of kidney transplants is known to decrease delayed graft function (DGF) and improve 1 year graft survival when compared to static cold preservation. Kidneys with better flow and resistance parameters on perfusion are likely to have a better post transplant function. These parameters are commonly used to evaluate kidneys being considered for transplantation. This study assesses the time frame for a kidney within which it reaches optimal perfusion parameters. All kidneys pumped between 5/2006 and 9/2009 on a Lifeport© kidney transporter at our local organ procurement agency were studied. 190 kidneys were evaluated and then divided into two groups based on whether terminal flows increased or declined after prolonged perfusion. All kidneys were assessed for changes in flow (F), resistance (R) and temperature at 15 minute intervals. Discards, DGF and one year graft survival were noted. The Student paired t test and Chi-square analysis were used to compare data. A multiple logistic regression analysis was performed to study independent predictors of DGF on pump perfusion.

RESULTS

For all kidneys, the mean initial flow was 59 ± 35 mL/min which improved to an average flow of 128 ± 38 mL/min with continued perfusion. The maximal flow and terminal flows were 148 ± 51 and 135 ± 38 mL/min respectively. The flows at 2, 4, and 6 hours was 125 ± 41, 128 ± 42 and 130 ± 39 mL/min respectively. Kidneys that improved on continued perfusion had a significantly lower discard rate (20 vs 34% p < 0.05), but a higher incidence of DGF (64 vs 39%, P < .05). One year graft loss (death censored) was comparable in the two groups. (4/42 vs. 3/33, P = .94). Resistance at 2, 4, and 6 hours was predictive of DGF, as was donor anoxia and cerebrovascular accident (CVA) as the cause of death.

CONCLUSIONS

Kidneys on pulsatile pump perfusion tend to show improved flows and decreased resistance over time. The average flow for a kidney is reached by 2 hours. Those kidneys that start with lower flow rates that improve after 2 hours with continued perfusion are less likely to be discarded but are still associated with a greater incidence of delayed graft function. Resistance at 2 hours predicts DGF while initial resistance predicts one year graft survival.

A CD3+ count-based thymoglobulin induction regimen permits delayed introduction of calcineurin inhibitors in kidney transplantation

BACKGROUND

Withholding calcineurin inhibitors (CNIs) can be considered when graft function is inadequate following kidney transplantation (KT). Thymoglobulin (rATG) can be used to prevent acute rejection while CNIs are being withheld. Here, we report our results of a novel CNI-sparing induction protocol, which utilizes a CD3+ cell count-based rATG treatment regimen when delayed graft function (DGF) develops in the immediate postoperative period.

METHODS

In a cohort of 153 consecutive deceased-donor KT recipients, all received a single intraoperative dose of basiliximab; 84 subsequently developed DGF and therefore received rATG (rATG+ group), while 69 demonstrated immediate graft function and received CNIs (rATG- group).

RESULTS

In the rATG+ group, mean duration of therapy was 8.5±6.0 d, permitting CNI initiation to be delayed until postoperative day 10.3±6.2. Cumulative dose of rATG was only 5.1±4.5 mg/kg while targeting CD3+ counts of ≤30 cells/mm3. CD3+ counts were reduced to a mean of 16.7±17.0 cells/mm3 during therapy. At one yr, patient and graft survival rates were 97.6% and 92.9%, respectively, while the frequency of infections and malignancies were not significantly increased compared to the rATG- group.

CONCLUSION

A unique induction regimen successfully delayed CNI initiation by using modest doses of rATG to deplete CD3+ cells, while yielding excellent long-term graft outcome without increased risk of infection or malignancy.

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

BACKGROUND

Accurate and reliable assessment of kidney quality before transplantation is needed to predict recipient outcomes and to optimize management and allocation of the allograft. The aim of this study was to systematically review the published literature on biomarkers in two mediums (the perfusate from deceased-donor kidneys receiving machine perfusion and deceased-donor urine) that were evaluated for their possible association with outcomes after kidney transplantation.

METHODS

We searched the Ovid Medline and Scopus databases using broad keywords related to deceased-donor biomarkers in kidney transplantation (limited to humans and the English language). Studies were included if they involved deceased-donor kidneys, measured perfusate or urine biomarkers and studied a possible relationship between biomarker concentrations and kidney allograft outcomes. Each included article was assessed for methodological quality.

RESULTS

Of 1430 abstracts screened, 29 studies met the inclusion criteria. Of these, 23 were studies of perfusate (16 biomarkers examined) and 6 were studies of urine (18 biomarkers examined). Only 3 studies (two perfusate) met the criteria of 'good' quality and only 12 were published since 2000. Perfusate lactate dehydrogenase, glutathione-S-transferase (GST) and aspartate transaminase were all found to be significantly associated with delayed graft function in a majority of their respective studies (6/9, 4/6 and 2/2 studies, respectively). Urine neutrophil gelatinase-associated lipocalin, GST, Trolox-equivalent antioxidant capacity and kidney injury molecule-1 were found to be significantly associated with allograft outcomes in single studies that examined diverse end points.

CONCLUSION

Higher quality studies are needed to investigate modern kidney injury biomarkers, to validate novel biomarkers in larger donor populations and to determine the incremental predictive value of biomarkers over traditional clinical variables.

The cutting (w)edge--comparative evaluation of renal baseline biopsies obtained by two different methods

BACKGROUND

The assessment of donor-derived damage of transplanted kidneys might be instrumental for estimating donor organ quality and for predicting short- and long-term organ outcome. In the present study, we report a new standardized method for obtaining pre-transplant kidney biopsy specimens. Instead of taking wedge biopsies (WBs), a skin punch biopsy (PB) tool was utilized to obtain standardized biopsy samples that also represented deeper cortical zones.

METHODS

We compared 147 PB specimens and 114 WBs with respect to the number of glomeruli and arterial vessels they contained. The performance of the two biopsy methods in detecting glomerular damage, interstitial fibrosis/tubular atrophy (IF/TA) and arteriosclerosis was determined by evaluation of subsequent transplant core biopsies of the patients. Statistical comparison employed Kruskal-Wallis and kappa (κ) tests.

RESULTS

Significantly more PB samples (89%) than WBs (66%) were diagnostically adequate according to the Banff criteria. Despite a higher number of glomeruli in WBs (34.6 versus 21.7 in punch biopsies), arteries were present in only 68% of WBs but could be found in 93% of punch biopsies. The comparison of findings in pre-transplant biopsies with lesions in corresponding post-transplant core biopsies revealed a superior diagnostic concordance for IF/TA and arteriosclerosis for punch biopsies than for WBs, reaching kappa values of 0.823 versus 0.729 and 0.661 versus 0.516, respectively.

CONCLUSION

The use of skin PB tools for obtaining baseline biopsies from transplanted kidneys is a safe and effective method for assessment of donor-derived damage of the organ.

Prediction of delayed graft function by means of a novel web-based calculator: a single-center experience

Renal failure persisting after renal transplant is known as delayed graft function (DGF). DGF predisposes the graft to acute rejection and increases the risk of graft loss. In 2010, Irish et al. developed a new model designed to predict DGF risk. This model was used to program a web-based DGF risk calculator, which can be accessed via http://www.transplantcalculator.com . The predictive performance of this score has not been tested in a different population. We analyzed 342 deceased-donor adult renal transplants performed in our hospital. Individual and population DGF risk was assessed using the web-based calculator. The area under the ROC curve to predict DGF was 0.710 (95% CI 0.653-0.767, p < 0.001). The "goodness-of-fit" test demonstrates that the DGF risk was well calibrated (p = 0.309). Graft survival was significantly better for patients with a lower DGF risk (5-year survival 71.1% vs. 60.1%, log rank p = 0.036). The model performed well with good discrimination ability and good calibration to predict DGF in a single transplant center. Using the web-based DGF calculator, we can predict the risk of developing DGF with a moderate to high degree of certainty only by using information available at the time of transplantation.