Redox-active iron released during machine perfusion predicts viability of ischemically injured deceased donor kidneys

Effects of prolonged cold ischemia on the DCD kidney function and Inflammasome expression in rat kidney transplants

BACKGROUND

Acute kidney injury (AKI) is the main reason for the bad outcome of the donation of circulatory death (DCD) kidney after transplantation. Prolonged cold storage (CS) is a risk factor for the occurrence of the delayed graft function in DCD kidney. The protein NLR-domain containing receptor 3 (NLRP3) plays a crucial role in renal ischemia reperfusion injury by triggering inflammasome formation. Herein, we investigated whether the NLRP3 signal participate in the CS-induced damage of DCD kidney in rat kidney transplantation models.

MATERIALS AND METHODS

DCD kidney and living donor (LD) kidney of SD rats were preserved in UW solution at 4 °C for 2 h or 18 h, and then transplanted into syngeneic recipient. Thus, the animals were randomly divided into 4 groups: 2-h LD group, 2-h DCD group, 18-h LD group and 18-h DCD group. The renal function and pathological changes were determined. The expressions of NLRP3 and inflammatory factor IL-1β were assessed. The concentration of ferrous iron (Fe²⁺) was analyzed both in kidneys and in the preservation solution. The renal morphological changes were examined by hematoxylin eosin staining.

RESULTS

Our results showed that the levels of Cr and BUN were higher in 18-h LD group as compared to the 2-h LD group, which were remarkably increased in 18-h DCD group. The expression levels of NLRP3 and IL-1β were increased by 18-h CS compared to 2-h CS in both LD kidney and DCD kidney. In addition, the Fe²⁺ concentration has significantly increased in 18-h LD group than that in 2-h LD group, and the elevation of Fe²⁺ was more remarkable in DCD kidneys.

CONCLUSION

In conclusion, our study demonstrated that prolonged hypothermic storage of DCD kidney deteriorated the graft function via the increased Fe²⁺ concentration, which was associated with the upregulation of NLRP3 expression.

Assessing Kidney Graft Viability and Its Cells Metabolism during Machine Perfusion

Kidney transplantation is the golden treatment for end-stage renal disease. Static cold storage is currently considered the standard method of preservation, but dynamic techniques, such as machine perfusion (MP), have been shown to improve graft function, especially in kidneys donated by extended criteria donors and donation after circulatory death. With poor organ quality being a major reason for kidneys not being transplanted, an accurate, objective and reliable quality assessment during preservation could add value and support to clinicians’ decisions. MPs are emerging technologies with the potential to assess kidney graft viability and quality, both in the hypothermic and normothermic scenarios. The aim of this review is to summarize current tools for graft viability assessment using MP prior to implantation in relation to the ischemic damage.

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.

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.

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).

Beyond transfusion therapy: new therapies in thalassemia including drugs, alternate donor transplant, and gene therapy

Transfusion combined with chelation therapy for severe β thalassemia syndromes (transfusion-dependent thalassemia [TDT]) has been successful in extending life expectancy, decreasing comorbidities and improving quality of life. However, this puts lifelong demands not only on the patients but also on the health care systems that are tasked with delivering long-term treatment and comprehensive support. Prevention programs and curative approaches are therefore an important part of overall strategy. Curative treatments alter the dynamic of a patient's health care costs, from financial commitment over 50 years, into a potential "one-off" investment. Since the 1980s, this has usually been available only to the 30% or so of young children with matched sibling donors. By improving the safety of matched related donors and haploidentical hematopoietic stem cell transplants, the potential size of the donor pool for curative therapies may be increased. Recent advances in gene therapy demonstrate that even patients lacking a matched donor can be rendered transfusion independent with an autograft of genetically modified autologous stem cells, with a low short-term risk. Noncurative treatments are also of potential value by decreasing use of blood and chelators and decreasing hospital visits. An example is luspatercept, an activin-receptor trap that modifies transforming growth factor-β signaling, thereby increasing the efficiency of erythropoiesis. This has entered phase 3 clinical trials for TDT and non-TDT and, usefully increases in both Hb and quality of life in non-TDT as well as decreasing transfusion requirements in TDT. Other novel noncurative treatments are entering clinical trials such improvement of erythropoiesis through pharmacological manipulation of hepcidin and iron metabolism.

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.

Renal iron overload in rats with diabetic nephropathy

Diabetic nephropathy (DN) remains incurable and is the main cause of end-stage renal disease. We approached the pathophysiology of DN with systems biology, and a comprehensive profile of renal transcripts was obtained with RNA-Seq in ZS (F1 hybrids of Zucker and spontaneously hypertensive heart failure) rats, a model of diabetic nephropathy. We included sham-operated lean control rats (LS), sham-operated diabetic (DS), and diabetic rats with induced renal ischemia (DI). Diabetic nephropathy in DI was accelerated by the single episode of renal ischemia. This progressive renal decline was associated with renal iron accumulation, although serum and urinary iron levels were far lower in DI than in LS. Furthermore, obese/diabetic ZS rats have severe dyslipidemia, a condition that has been linked to hepatic iron overload. Hence, we tested and found that the fatty acids oleic acid and palmitate stimulated iron accumulation in renal tubular cells in vitro. Renal mRNAs encoding several key proteins that promote iron accumulation were increased in DI. Moreover, renal mRNAs encoding the antioxidant proteins superoxide dismutase, catalase, and most of the glutathione synthetic system were suppressed, which would magnify the prooxidant effects of renal iron loads. Substantial renal iron loads occur in obese/diabetic rats. We propose that in diabetes, specific renal gene activation is partly responsible for iron accumulation. This state might be further aggravated by lipid-stimulated iron uptake. We suggest that progressive renal iron overload may further advance renal injury in obese/diabetic ZS rats.

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.

Assessing warm ischemic injury of pig livers at hypothermic machine perfusion

BACKGROUND

Livers originating from donation after circulatory death (DCD) donors are exposed to warm ischemia (WI) before liver transplantation (LTx). Currently, there are no objective tests to evaluate the damage sustained before LTx. This study aims to identify surrogate markers for liver injury that can be assessed during hypothermic machine perfusion (HMP) preservation. In addition, we want to use mathematical equation modeling combining these markers to improve our assessment of DCD livers for transplantation.

MATERIALS AND METHODS

Porcine livers were exposed to incremental periods of WI (0-120 min) and subsequently HMP preserved for 4 h. Biochemical and hemodynamic parameters were repeatedly measured in the perfusate during HMP. Subsequently, to mimic LTx, normothermic isolated-liver perfusion was applied for 2 h and the injury assessed using a morphological score.

RESULTS

With increasing WI periods, the perfusate became more acidotic, and levels of aspartate aminotransferase (AST), liver fatty acid binding protein, redox-active iron, and arterial vascular resistance increased. A damage index, combining AST and pH (damage index = 2 - 37 × β(AST) - 257 × β(pH)) based on multifactorial analysis of the changing pattern of these markers, had increased sensitivity and specificity to reflect WI and reperfusion injury.

CONCLUSIONS

This proof of concept study demonstrated the potential role for objective evaluation of DCD porcine livers during HMP and the advantage to use multifactorial analysis on the markers' changing pattern.

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.

The value of machine perfusion biomarker concentration in DCD kidney transplantations

BACKGROUND

Donation after cardiac death (DCD) increases the number of donor kidneys but is associated with more primary nonfunction (PNF) and delayed graft function (DGF). It has been suggested that biomarkers in the preservation solution of machine perfused kidneys may predict PNF, although evidence is lacking.

METHODS

We analyzed the diagnostic accuracy of the perfusate biomarkers glutathione S-transferase, lactate dehydrogenase (LDH), heart-type fatty acid binding protein, redox-active iron, interleukin (IL)-18, and neutrophil gelatinase-associated lipocalin to predict PNF and DGF in 335 DCD kidneys preserved by hypothermic machine perfusion at our center between 1 January 1997 and 1 January 2008. The diagnostic accuracy of these biomarkers to predict PNF was evaluated with the area under the receiver operating characteristics curves. Additionally, the risk of DGF and graft failure was assessed.

RESULTS

LDH and IL-18 concentrations were associated with PNF (odds ratio [95% confidence interval], 1.001 [1.000-1.002]; P=0.005 and 1.001 [1.000-1.002]; P=0.003, respectively) in a multivariate analysis; the diagnostic accuracy for PNF was "poor" for all biomarkers but increased to "fair" for redox-active iron and IL-18 in a multivariate analysis (area under the receiver operating characteristics curves, 0.701 and 0.700, respectively). LDH and IL-18 concentrations were associated with DGF; biomarker concentration was not associated with 1-year graft survival.

CONCLUSIONS

The diagnostic accuracy of the perfusate biomarkers glutathione S-transferase, LDH, heart-type fatty acid binding protein, redox-active iron, IL-18, and neutrophil gelatinase-associated lipocalin to predict viability of DCD kidneys varies from "poor" to "fair". Therefore, DCD kidneys should not be discarded because of high biomarker perfusate concentration.

Characterization of the perfusate proteome of human donor kidneys

BACKGROUND

Preservation of deceased donor kidneys by hypothermic machine perfusion results in superior transplant outcomes as compared with static cold storage and provides the opportunity to measure biomarkers of cellular injury in perfusate samples. Identification of biomarkers predicting early graft dysfunction so far has met with limited success.

METHODS

Two-dimensional difference gel electrophoresis and mass spectrometry were used to explore the proteome of perfusate samples from machine-perfused human donor kidneys (N = 18) and to discover novel biomarkers of ischaemic acute kidney injury.

RESULTS

Thirty-two protein spots were successfully identified, representing 19 unique proteins that were derived from renal tissue and from residual plasma in the renal microcirculation. Two unidentified protein spots were significantly up-regulated, whereas one protein spot--identified as haptoglobin--was significantly down-regulated in the perfusate of ischaemically injured kidneys from donors after cardiac death as compared with kidneys from brain-dead donors who had not suffered warm ischaemic injury. Furthermore, two protein spots were up-regulated in kidneys that never functioned after transplantation, whereas one spot was up-regulated--identified as α1-antitrypsin--in kidneys with delayed graft function.

CONCLUSIONS

We provide the first description of the renal perfusate proteome and present preliminary evidence of differentially expressed biomarkers in human donor kidneys with different levels of acute ischaemic injury. Their diagnostic value for the selection of marginal kidneys in clinical transplantation should be determined in future studies.

Desferrioxamine in warm reperfusion media decreases liver injury aggravated by cold storage

AIM: To evaluate whether desferrioxamine decreases ischemia and perfusion injury aggravated by cold storage (CS) in a rat liver perfusion model.

METHODS: Isolated rat livers were kept in CS in University of Wisconsin Solution for 20 h at 4 °C, then exposed to 25 min of warm ischemia (WI) at 37 °C followed by 2 h of warm perfusion (WP) at 37 °C with oxygenated (95% oxygen and 5% carbon dioxide) Krebs-Henseleit buffer. Desferrioxamine (DFO), an iron chelator, was added at different stages of storage, ischemia and perfusion: in CS only, in WI only, in WP only, in WI and perfusion, or in all stages. Effluent samples were collected after CS and after WI. Perfusate samples and bile were collected every 30 min (0, 0.5, 1, 1.5 and 2 h) during liver perfusion. Cellular injury was assessed by the determination of lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) in the effluent and perfusate samples. Total iron was analysed in the perfusate samples. After WP, the liver was collected for the determination of liver swelling (wet to dry ratio) and liver morphological examination (hematoxylin and eosin staining).

RESULTS: Increased CS time caused increased liver dysfunction during WP. After 2 h of WP, liver injury was indicated by increased release of AST (0.5 h CS: 9.4 ± 2.2 U/g liver vs 20 h CS: 45.9 ± 10.8 U/g liver, P < 0.05) and LDH (0.5 h CS: 59 ± 14 U/g liver vs 20 h CS: 297 ± 71 U/g liver, P < 0.05). There was an associated increase in iron release into the perfusate (0.5 h CS: 0.11 ± 0.03 μmoL/g liver vs 20 h CS: 0.58 ± 0.10 μmoL/g liver, P < 0.05) and reduction in bile flow (0.5 h CS: 194 ± 12 μL/g vs 20 h CS: 71 ± 8 μL/g liver, P < 0.05). When DFO was added during WI and WP following 20 h of CS, release of iron into the perfusate was decreased (DFO absent 0.58 ± 0.10 μmoL/g liver vs DFO present 0.31 ± 0.06 μmoL/g liver, P < 0.05), and liver function substantially improved with decreased release of AST (DFO absent 45.9 ± 10.8 U/g liver vs DFO present 8.1 ± 0.9 U/g liver, P < 0.05) and LDH (DFO absent 297 ± 71 U/g liver vs DFO present 56 ± 7 U/g liver, P < 0.05), and increased bile flow (DFO absent 71 ± 8 μL/g liver vs DFO present 237 ± 36 μL/g liver, P < 0.05). DFO was also shown to improve liver morphology after WP. Cellular injury (the release of LDH and AST) was significantly reduced with the addition of DFO in CS medium but to a lesser extent compared to the addition of DFO in WP or WI and perfusion. There was no effect on liver swelling or bile flow when DFO was only added to the CS medium.

CONCLUSION: DFO added during WI and perfusion decreased liver perfusion injury aggravated by extended CS.

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.

Kidney transplantation from donors after cardiac death: uncontrolled versus controlled donation

Kidney donation after cardiac death has been popularized over the last decade. The majority of these kidneys are from controlled donors. The number of organs for transplantation can be further increased by uncontrolled donors after cardiac death. The outcome of uncontrolled compared to controlled donor kidney transplantation is relatively unknown. We compared the long-term outcome of kidney transplantation from uncontrolled (n = 128) and controlled (n = 208) donor kidneys procured in the Maastricht region from January 1, 1981 until January 1, 2008, and transplanted in the Eurotransplant region. The incidence of primary nonfunction and delayed graft function in both uncontrolled and controlled donor kidneys is relatively high (22% vs. 21%, and 61% vs. 56%, p = 0.43, respectively). Ten-year graft and recipient survival are similar in both groups (50% vs. 46%, p = 0.74 and 61% vs. 60%, p = 0.76, respectively). Estimated glomerular filtration rates 1 year after transplantation are 40 ± 16 versus 42 ± 19 mL/min/1.73 m(2) , p = 0.55, with a yearly decline thereafter of 0.67 ± 3 versus 0.70 ± 7 mL/min/1.73 m(2) /year, p = 0.97. The outcome of kidney transplantation from uncontrolled and controlled donors after cardiac death is equivalent. This justifies the expansion of the donor pool with uncontrolled donors to reduce the still growing waiting list for renal transplantation, and may stimulate the implementation of uncontrolled kidney donation programs.

Normothermic kidney preservation

PURPOSE OF REVIEW

Kidneys from marginal or donation after cardiac death (DCD) donors are particularly susceptible to injury during hypothermic preservation and may benefit from alternative methods of preservation. Normothermic preservation can be adapted to improve the quality of kidneys for transplantation by a variety of techniques.

RECENT FINDINGS

Extracorporeal membrane support to maintain circulation before cooling and organ retrieval has been used to improve the condition of DCD donor kidneys, with lower rates of delayed graft function (DGF) compared with standard retrieval conditions. Experimentally, normothermic perfusion has been used in conjunction with hypothermic techniques as a resuscitation technique to improve graft outcome. An ex-vivo porcine kidney model showed that energy levels could be replenished to improve tissue perfusion during reperfusion. This technique was translated into a porcine transplant model demonstrating that it was a feasible and safe method of preservation.

SUMMARY

Normothermic preservation techniques have the potential to be adapted into an improved method of retaining tissue viability compared with hypothermic techniques. Furthermore, they may be used as a device to enhance and assess the condition of the kidney which would be particularly beneficial for kidneys from DCD donors.

A comparison of hypothermic machine perfusion versus static cold storage in an experimental model of renal ischemia reperfusion injury

INTRODUCTION

There is increasing support for the use of hypothermic machine perfusion (HMP) in an attempt to reduce preservation injury. However, experimental evidence is needed to further examine the effects of HMP on renal ischemia reperfusion injury.

METHODS

Porcine kidneys were subjected to 10 min of warm ischemia followed by 18 hr of static cold storage with hyperosomolar citrate (HOC), histidine-tryptophan-ketoglutarate (HTK), or University of Wisconsin (UW) solutions or 18 hr HMP with Kidney Perfusion Solution using the Lifeport perfusion system. Renal function, oxidative damage, and morphology were assessed during 3 hr of reperfusion with autologous blood using an isolated organ perfusion system.

RESULTS

During reperfusion, intrarenal resistance was significantly lower in the HMP group compared with HOC and UW (area under the curve; HMP 3.8+/-1.7, HOC 9.1+/-4.3, UW 7.7+/-2.2, HTK 5.6+/-1.9 mm Hg/min; P=0.006), and creatinine clearance was significantly higher compared with the UW group (area under the curve creatinine clearance; HMP 9.8+/-7.3, HOC 2.2+/-1.7, UW 1.8+/-1.0, HTK 2.1+/-1.8 mL/min/100 g; P=0.004). Tubular function was significantly improved in the HMP group (P<0.05); however, levels of lipid peroxidation were significantly higher (P=0.005).

CONCLUSION

HMP demonstrated a reduced level of preservation injury compared with the static techniques resulting in improved renal and tubular function and less tubular cell inflammation during reperfusion.

Pulsatile perfusion of kidney allografts

PURPOSE OF REVIEW

The purpose of this article is to describe the current use of pulsatile kidney perfusion during organ preservation and the effects on kidney allograft outcomes and utilization.

RECENT FINDINGS

As of spring 2008, there were 75 629 candidates on the kidney waiting list in the USA according to United Network for Organ Sharing data. In 2006, a total of 1815 deceased donor expanded criteria donors kidneys were transplanted, and approximately 80% of those kidneys had cold ischemic time of over 12 h. The utilization of kidney pulsatile perfusion varies extensively throughout the USA with rates of 7-12% in our institution.

SUMMARY

Data on the use of pulsatile hypothermic perfusion for kidneys during organ preservation are limited and mostly retrospective. Most authors agree that pulsatile perfusion is safe and leads to a decrease in delayed graft function, especially for marginal kidneys from extended criteria or deceased donors. The long-term effects of delayed graft function on graft survival remain to be seen. With the recent large-sampled international prospective randomized trial recently completed, we may see more kidneys pulsatile perfused. This may lead to an increase in the utilization of otherwise discarded kidneys, though these data are difficult to extrapolate.

Artificial circulation of the liver: machine perfusion as a preservation method in liver transplantation

Due to the sharp increase in liver transplant candidates and the subsequent shortage of suitable donor livers, an extension of the current donor criteria is necessary. Simple cold storage, the current standard in organ preservation has proven to be insufficient to preserve extended criteria donor livers. Therefore a renewed interest grew toward alternative methods for liver preservation, such as hypothermic machine perfusion and normothermic machine perfusion. These "new" preservation methods were primarily assessed in rat models, and only a few clinically relevant large animal models have been described so far. This review will elaborate on these alternative preservation methods.

Recipient hemodynamics during non-heart-beating donor kidney transplantation are major predictors of primary nonfunction

Non-heart-beating donor (NHBD) kidneys may substantially expand the donor pool, but many transplant centers are reluctant to use these kidneys because of the relatively high incidence of primary nonfunction (PNF). In heart-beating donor kidneys, intravascular fluid depletion during transplant surgery is associated with delayed graft function (DGF). Therefore, we studied the effect of the recipients' hemodynamic status on the outcome of 177 NHBD kidney transplantations. Independent statistically significant predictors of PNF were average central venous pressure (CVP) below 6 cmH(2)O (adjusted odds ratio (AOR) 3.1 (95% CI: 1.4-7.1), p=0.007), average systolic blood pressure below 110 mmHg (AOR 2.6 (95% CI: 1.1-5.9), p=0.03) and pre-operative diastolic blood pressure below 80 mmHg (AOR 2.4 (95% CI: 1.0-5.9), p=0.05). Donor characteristics were not independently associated with PNF (p>0.10). In a subgroup analysis of 56 paired kidneys, 29% of the recipients with the lower CVP of the pair experienced PNF compared with 11% of their counterparts with higher CVP (p=0.09). Our study indicates that recipient hemodynamics during transplant surgery are major predictors of PNF. Therefore, improving recipient hemodynamics by expansion of the intravascular volume is expected to enhance the results of NHBD kidney transplantations and may enlarge the donor pool by increasing the acceptance of NHBD kidneys.

Non-heartbeating donation of kidneys for transplantation

There is a persistent shortage of kidneys available for transplantation. In the early 1980s, therefore, we published the concept of non-heartbeating (NHB) donation; that is, procurement of kidneys from donors whose death has been accompanied by irreversible circulatory arrest. NHB donors are generally categorized using four definitions; category III (awaiting cardiac arrest) and category IV (cardiac arrest while braindead)--or 'controlled'--donors are the most suitable for initiating NHB donation programs. Delayed graft function is associated with use of kidneys from such donors, but has no effect on graft survival in the short or long term. Use of kidneys from category I (dead upon arrival at hospital) and category II (unsuccessfully resuscitated), or 'uncontrolled', donors is likewise associated with delayed graft function, but also with an increased risk of primary nonfunction. Viability testing of donated organs from these sources is a prerequisite for transplantation. Machine preservation parameters and enzyme release measurements help to distinguish viable from nonviable kidneys. The proportion of NHB donor kidneys in the total pool of postmortem kidneys differs considerably between countries. In The Netherlands, the proportion is nearly 50%. This figure is markedly higher than that in the US and Canada, where national programs have now been initiated to increase rates of NHB donation. In the future, warm preservation techniques might facilitate better viability testing, thereby increasing NHB donation from category I and II donors and further reducing the shortage of kidneys available for transplantation.