Lysis of cold-storage-induced microvascular obstructions for ex vivo revitalization of marginal human kidneys

Salvaging donated kidneys from prolonged warm ischemia during ex vivo hypothermic oxygenated perfusion

Prolonged warm ischemic is the main cause discarding donated organs after cardiac death. Here, we identified that prolonged warm ischemic time induced disseminated intravascular coagulation and severe capillary vasospasm after cardiac death of rat kidneys. Additionally, we found a significant accumulation of fibrinogen in a hypoxic cell culture of human umbilical vein epithelial cells and in isolated kidneys exposed to prolonged warm ischemic following flushing out of blood. However, pre-flushing the kidney with snake venom plasmin in a 90-minute warm ischemic model maximized removal of micro thrombi and facilitated the delivery of oxygen and therapeutic agents. Application of carbon monoxide-releasing CORM-401 during ex vivo hypothermic oxygenated perfusion achieved multipath protective effects in prolonged warm ischemic kidneys. This led to significant improvements in perfusion parameters, restoration of the microcirculation, amelioration of mitochondrial injury, oxidative stress, and apoptosis. This benefit resulted in significantly prolonged warm ischemic kidney recipient survival rates of 70%, compared with none in those receiving ex vivo hypothermic oxygenated perfusion alone. Significantly, ex vivo hypothermic oxygenated perfusion combined with cytoprotective carbon monoxide releasing CORM-401 treatment meaningfully protected the donated kidney after cardiac death from ischemia-reperfusion injury by reducing inflammation, oxidative stress, apoptosis, and pathological damage. Thus, our study suggests a new combination treatment strategy to potentially expand the donor pool by increasing use of organs after cardiac death and salvaging prolonged warm ischemic kidneys.

Utilizing pathophysiological concepts of ischemia-reperfusion injury to design renoprotective strategies and therapeutic interventions for normothermic ex vivo kidney perfusion

Normothermic machine perfusion (NMP) has emerged as a promising tool for the preservation, viability assessment, and repair of deceased-donor kidneys prior to transplantation. These kidneys inevitably experience a period of ischemia during donation, which leads to ischemia-reperfusion injury when NMP is subsequently commenced. Ischemia-reperfusion injury has a major impact on the renal vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis. With an increased understanding of the underlying pathophysiological mechanisms, renoprotective strategies and therapeutic interventions can be devised to minimize additional injury during normothermic reperfusion, ensure the safe implementation of NMP, and improve kidney quality. This review discusses the pathophysiological alterations in the vasculature, metabolism, oxygenation, electrolyte balance, and acid-base homeostasis of deceased-donor kidneys and delineates renoprotective strategies and therapeutic interventions to mitigate renal injury and improve kidney quality during NMP.

Red blood cells as oxygen carrier during normothermic machine perfusion of kidney grafts: Friend or foe?

Renal ex vivo normothermic machine perfusion (NMP) is under development as an assessment tool for high-risk kidney grafts and as a means of achieving more physiologically accurate organ preservation. On-going hemolysis has been reported during NMP, as this technique relies on red blood cells for oxygen delivery. In this study, we confirm the occurrence of progressive hemolysis during 6-hour kidney NMP. NMP-associated erythrostasis in the glomeruli and in peri-glomerular vascular networks points to an interaction between the red blood cells and the graft. Continuous hemolysis resulted in prooxidative changes in the perfusate, which could be quenched by addition of fresh frozen plasma. In a cell-based system, this hemolysis induced redox stress and exhibited toxic effects at high concentrations. These findings highlight the need for a more refined oxygen carrier in the context of renal NMP.

Indocyanine green fluorescence quantification during normothermic ex situ perfusion for the assessment of porcine liver grafts after circulatory death

Current graft evaluation during normothermic ex situ liver perfusion lacks real-time parameters for predicting posttransplant hepatocyte and biliary function. Indocyanine green (ICG) imaging has been widely used in liver surgery, enabling the visualization of hepatic uptake and excretion through bile using near-infrared light. In this research, porcine livers under various ischemic conditions were examined during a 5-hour normothermic ex situ liver perfusion procedure, introducing ICG at 1 hour through the hepatic artery. These conditions included livers from heart-beating donors, donation after circulatory death (DCD) with warm ischemic durations of 60 minutes (DCD60) and 120 minutes (DCD120), as well as interventions utilizing tissue plasminogen activator in DCD120 cases (each n = 5). Distinct hepatic fluorescence patterns correlated with different degrees of ischemic injury ( p = 0.01). Low ICG uptake in the parenchyma (less than 40% of maximum intensity) was more prevalent in DCD120 (21.4%) compared to heart-beating donors (6.2%, p = 0.06) and DCD60 (3.0%, p = 0.02). Moreover, ICG clearance from 60 minutes to 240 minutes was significantly higher in heart-beating donors (69.3%) than in DCD60 (17.5%, p < 0.001) and DCD120 (32.1%, p = 0.01). Furthermore, thrombolytic intervention using tissue plasminogen activator in DCD120 resulted in noteworthy outcomes, including significantly reduced ALP levels ( p = 0.04) and improved ICG clearance ( p = 0.02) with a trend toward mitigating fibrin deposition similar to DCD60, as well as enhancements in bile production ( p = 0.09). In conclusion, ICG fluorescence imaging during normothermic ex situ liver perfusion provides real-time classification of hepatic vascular and biliary injuries, offering valuable insights for the more accurate selection and postintervention evaluation of marginal livers in transplantation.

Current Techniques and Indications for Machine Perfusion and Regional Perfusion in Deceased Donor Liver Transplantation

Since the advent of University of Wisconsin preservation solution in the 1980s, clinicians have learned to work within its confines. While affording improved outcomes, considerable limitations still exist and contribute to the large number of livers that go unused each year, often for fear they may never work. The last 10 years have seen the widespread availability of new perfusion modalities which provide an opportunity for assessing organ viability and prolonged organ storage. This review will discuss the role of in situ normothermic regional perfusion for livers donated after circulatory death. It will also describe the different modalities of ex situ perfusion, both normothermic and hypothermic, and discuss how they are thought to work and the opportunities afforded by them.

Normothermic ex vivo perfusion of deceased donor kidneys and its clinical potential in kidney transplantation outcomes

In recent years, normothermic machine perfusion (NMP) has emerged in conversation surrounding organ preservation and transplantation techniques with the goal of improving patient and clinical outcomes. This is in great attempt to address the rate of non-utilization and the shortage of available organs in kidney transplantation. This focus in mind, normothermic perfusion presents itself as a potential tool to mimic physiological conditions and improve current preservation methods, such as static cold storage. This review serves to improve understanding of the observed connection between the consequences of ischemia and reperfusion injury and traditional preservation techniques as well as how renal NMP may mitigate these issues. Previous studies suggest that reducing time in static cold storage methods by promoting the normothermic perfusion model results in decreased delayed graft function and post-transplant complications. This review also aims to present the immense clinical potential NMP has on future kidney transplantation success and what this means for the fields of nephrology and transplantation. While great strides have been made to evaluate normothermic perfusion's impact on kidney graft viability and transplant success, future research into unified protocol, clinically relevant biomarkers, cost-utility analysis, and use with associated therapeutic and imaging modalities is paramount.

Perfusate Proteomes Provide Biological Insight Into Oxygenated Versus Standard Hypothermic Machine Perfusion in Kidney Transplantation

OBJECTIVE

To provide mechanistic insight into key biological alterations in donation after circulatory death kidneys during continuous pefusion we performed mass spectrometry profiling of perfusate samples collected during a phase 3 randomized double-blind paired clinical trial of hypothermic machine perfusion with and without oxygen (COMPARE).

BACKGROUND

Despite the clinical benefits of novel perfusion technologies aiming to better preserve donor organs, biological processes that may be altered during perfusion have remained largely unexplored. The collection of serial perfusate samples during the COMPARE clinical trial provided a unique resource to study perfusate proteomic profiles, with the hypothesis that in-depth profiling may reveal biologically meaningful information on how donor kidneys benefit from this intervention.

METHODS

Multiplexed liquid chromatography-tandem mass spectrometry was used to obtain a proteome profile of 210 perfusate samples. Partial least squares discriminant analysis and multivariate analysis involving clinical and perfusion parameters were used to identify associations between profiles and clinical outcomes.

RESULTS

Identification and quantitation of 1716 proteins indicated that proteins released during perfusion originate from the kidney tissue and blood, with blood-based proteins being the majority. Data show that the overall hypothermic machine perfusion duration is associated with increasing levels of a subgroup of proteins. Notably, high-density lipoprotein and complement cascade proteins are associated with 12-month outcomes, and blood-derived proteins are enriched in the perfusate of kidneys that developed acute rejection.

CONCLUSIONS

Perfusate profiling by mass spectrometry was informative and revealed proteomic changes that are biologically meaningful and, in part, explain the clinical observations of the COMPARE trial.

48 h Normothermic Machine Perfusion With Urine Recirculation for Discarded Human Kidney Grafts

Normothermic machine perfusion (NMP) has reshaped organ preservation in recent years. In this preclinical study, prolonged normothermic perfusions of discarded human kidney grafts were performed in order to investigate perfusion dynamics and identify potential quality and assessment indicators. Five human discarded kidney grafts were perfused normothermically (37°C) for 48 h using the Kidney Assist device with a red-blood-cell based perfusate with urine recirculation. Perfusion dynamics, perfusate and urine composition as well as injury markers were measured and analyzed. Donor age ranged from 41 to 68 years. All but one kidney were from brain dead donors. Perfusions were performed successfully for 48 h with all discarded kidneys. Median arterial flow ranged from 405 to 841 mL/min. All kidneys excreted urine until the end of perfusion (median 0.43 mL/min at the end of perfusion). While sodium levels were consistently lower in urine compared to perfusate samples, this was only seen for chloride and potassium in kidney KTX 2. Lactate, AST, LDH as well as pro-inflammatory cytokines increased over time, especially in kidneys KTX 3 and 4. Ex vivo normothermic perfusion is able to identify patterns of perfusion, biological function, and changes in inflammatory markers in heterogenous discarded kidney grafts.

Rational nanoparticle design: Optimization using insights from experiments and mathematical models

Polymeric nanoparticles are highly tunable drug delivery systems that show promise in targeting therapeutics to specific sites within the body. Rational nanoparticle design can make use of mathematical models to organize and extend experimental data, allowing for optimization of nanoparticles for particular drug delivery applications. While rational nanoparticle design is attractive from the standpoint of improving therapy and reducing unnecessary experiments, it has yet to be fully realized. The difficulty lies in the complexity of nanoparticle structure and behavior, which is added to the complexity of the physiological mechanisms involved in nanoparticle distribution throughout the body. In this review, we discuss the most important aspects of rational design of polymeric nanoparticles. Ultimately, we conclude that many experimental datasets are required to fully model polymeric nanoparticle behavior at multiple scales. Further, we suggest ways to consider the limitations and uncertainty of experimental data in creating nanoparticle design optimization schema, which we call quantitative nanoparticle design frameworks.

Expanding the Horizons of Pre-Transplant Renal Vascular Assessment Using Ex Vivo Perfusion

Recently, immense efforts have focused on improving the preservation of (sub)optimal donor organs by means of ex vivo perfusion, which enables the opportunity for organ reconditioning and viability assessment. However, there is still no biomarker that correlates with renal viability. Therefore, it is essential to explore new techniques for pre-transplant assessment of organ quality to guarantee successful long-term transplantation outcomes. The renal vascular compartment has received little attention in machine perfusion studies. In vivo, proper renal vascular and endothelial function is essential for maintaining homeostasis and long-term graft survival. In an ex vivo setting, little is known about vascular viability and its implications for an organ's suitability for transplant. Seeing that endothelial damage is the first step in a cascade of disruptions and maintaining homeostasis is crucial for positive post-transplant outcomes, further research is key to clarifying the (patho)physiology of the renal vasculature during machine perfusion. In this review, we aim to summarize key aspects of renal vascular physiology, describe the role of the renal vasculature in pathophysiological settings, and explain how ex vivo perfusion plays a role in either unveiling or targeting such processes. Additionally, we discuss potentially new vascular assessment tools during ex vivo renal perfusion.

D-dimer Release From Livers During Ex Situ Normothermic Perfusion and After In Situ Normothermic Regional Perfusion: Evidence for Occult Fibrin Burden Associated With Adverse Transplant Outcomes and Cholangiopathy

BACKGROUND

Deceased donor livers are prone to biliary complications, which may necessitate retransplantation, and we, and others, have suggested that these complications are because of peribiliary vascular fibrin microthrombi. We sought to determine the prevalence and consequence of occult fibrin within deceased donor livers undergoing normothermic ex situ perfusion (NESLiP) and evaluate a role for fibrinolysis.

METHODS

D-dimer concentrations, products of fibrin degradation, were assayed in the perfusate of 163 livers taken after 2 h of NESLiP, including 91 that were transplanted. These were related to posttransplant outcomes. Five different fibrinolytic protocols during NESLiP using alteplase were evaluated, and the transplant outcomes of these alteplase-treated livers were reviewed.

RESULTS

Perfusate D-dimer concentrations were lowest in livers recovered using in situ normothermic regional perfusion and highest in alteplase-treated livers. D-dimer release from donation after brain death livers was significantly correlated with the duration of cold ischemia. In non-alteplase-treated livers, Cox proportional hazards regression analysis showed that D-dimer levels were associated with transplant survival ( P  = 0.005). Treatment with alteplase and fresh frozen plasma during NESLiP was associated with significantly more D-dimer release into the perfusate and was not associated with excess bleeding postimplantation; 8 of the 9 treated livers were free of cholangiopathy, whereas the ninth had a proximal duct stricture.

CONCLUSIONS

Fibrin is present in many livers during cold storage and is associated with poor posttransplant outcomes. The amount of D-dimer released after fibrinolytic treatment indicates a significant occult fibrin burden and suggests that fibrinolytic therapy during NESLiP may be a promising therapeutic intervention.

The Current Role and Future Applications of Machine Perfusion in Liver Transplantation

The relative paucity of donor livers suitable for transplantation has sparked innovations to preserve and recondition organs to expand the pool of transplantable organs. Currently, machine perfusion techniques have led to the improvement of the quality of marginal livers and to prolonged cold ischemia time and have allowed for the prediction of graft function through the analysis of the organ during perfusion, improving the rate of organ use. In the future, the implementation of organ modulation might expand the scope of machine perfusion beyond its current usage. The aim of this review was to provide an overview of the current clinical use of machine perfusion devices in liver transplantation and to provide a perspective for future clinical use, including therapeutic interventions in perfused donor liver grafts.

Current Evidence and Future Perspectives to Implement Continuous and End-Ischemic Use of Normothermic and Oxygenated Hypothermic Machine Perfusion in Clinical Practice

The use of high-risk renal grafts for transplantation requires the optimization of pretransplant assessment and preservation reconditioning strategies to decrease the organ discard rate and to improve short- and long-term clinical outcomes. Active oxygenation is increasingly recognized to play a central role in dynamic preservation strategies, independent of preservation temperature, to recondition mitochondria and to restore the cellular energy profile. The oxygen-related decrease in mitochondrial succinate accumulation ameliorates the harmful effects of ischemia-reperfusion injury. The differences between normothermic and hypothermic machine perfusion with regard to organ assessment, preservation, and reconditioning, as well as the logistic and economic implications, are factors to take into consideration for implementation at a local level. Therefore, these different techniques should be considered complementary to the perfusion strategy selected depending on functional intention and resource availability. This review provides an overview of the current clinical evidence of normothermic and oxygenated hypothermic machine perfusion, either as a continuous or end-ischemic preservation strategy, and future perspectives.

How to Best Protect Kidneys for Transplantation-Mechanistic Target

The increasing number of patients on the kidney transplant waiting list underlines the need to expand the donor pool and improve kidney graft utilization. By protecting kidney grafts adequately from the initial ischemic and subsequent reperfusion injury occurring during transplantation, both the number and quality of kidney grafts could be improved. The last few years have seen the emergence of many new technologies to abrogate ischemia-reperfusion (I/R) injury, including dynamic organ preservation through machine perfusion and organ reconditioning therapies. Although machine perfusion is gradually making the transition to clinical practice, reconditioning therapies have not yet progressed from the experimental setting, pointing towards a translational gap. In this review, we discuss the current knowledge on the biological processes implicated in I/R injury and explore the strategies and interventions that are being proposed to either prevent I/R injury, treat its deleterious consequences, or support the reparative response of the kidney. Prospects to improve the clinical translation of these therapies are discussed with a particular focus on the need to address multiple aspects of I/R injury to achieve robust and long-lasting protective effects on the kidney graft.

Honoring the gift: The transformative potential of transplant-declined human organs

For decades, transplantation has been a life-saving treatment for those fortunate enough to gain access. Nevertheless, many patients die waiting for an organ and countless more never make it onto the waitlist because of a shortage of donor organs. Concurrently, thousands of donated organs are declined for transplant each year because of concerns about poor outcomes post-transplant. The decline of any donated organ-even if medically justified-is tragic for both the donor family and potential recipients. In this Personal Viewpoint, we discuss the need for a new mindset in how we honor the gift of organ donation. We believe that the use of transplant-declined human organs in translational research has the potential to hasten breakthrough discoveries in a multitude of scientific and medical areas. More importantly, such breakthroughs will allow us to properly value every donated organ. We further discuss the many practical challenges that such research presents and offer some possible solutions based on experiences in our own research laboratories. Finally, we share our perspective on what we believe are the necessary next steps to ensure a future where every donated organ realizes its full potential to impact the lives of current and future patients.

Long-term Transplant Function After Thrombolytic Treatment Ex Vivo of Donated Kidneys Retrieved 4 to 5 H After Circulatory Death

BACKGROUND

Using a novel thrombolytic technique, we present long-term transplant function, measured by creatinine and iohexol clearance, after utilizing kidneys from porcine donors with uncontrolled donation after circulatory deaths, with 4.5-5 h of warm ischemia.

METHODS

Pigs in the study group were subjected to simulated circulatory death. After 2 h, ice slush was inserted into the abdomen and 4.5 h after death, the kidneys were retrieved. Lys-plasminogen, antithrombin-III, and alteplase were injected through the renal arteries on the back table. Subsequent ex vivo perfusion was continued for 3 h at 15°C, followed by 3 h with red blood cells at 32°C, and then transplanted into pigs as an autologous graft as only renal support. Living-donor recipient pigs that did not receive ex vivo perfusion, and unilateral nephrectomized pigs served as the controls.

RESULTS

Pigs in the study group (n = 13), surviving 10 d or more were included, of which 7 survived for 3 mo. Four animals in the living-donor group (n = 6) and all 5 nephrectomized animals survived for 3 mo. Creatinine levels in the plasma and urine, neutrophil gelatinase-associated lipocalin levels, Kidney Injury Marker-1 expression, and iohexol clearance at 3 mo did not differ significantly between the study and living-donor groups. Histology and transmission electron microscopy after 3 mo showed negligible fibrosis and no other damage.

CONCLUSIONS

The present method salvages kidneys from extended unontrolled donation after circulatory death using thrombolytic treatment while preserving histology and enabling transplantation after ex vivo reconditioning, with clinically acceptable late function after 3 mo, as measured by creatinine and iohexol clearance.

Application of Ex Vivo Normothermic Machine Perfusion in Deceased Donors With Acute Kidney Injury With Successful Renal Transplantation: A Preliminary Experience

Ex vivo normothermic machine perfusion (NMP) has improved organ preservation and viability assessment among heart, liver, and lung transplantation. However, literature regarding the application of NMP in human clinical kidney transplantation remains limited. Numerous kidneys, especially from donors with stage 3 acute kidney injury (AKI), are not utilized concerning the high rate of delayed graft function (DGF) and primary nonfunction. The present study investigated the impact of NMP (135-150 min) on short-term outcomes after kidney transplantation from deceased donors with AKI.

Methods

Graft outcomes of NMP kidneys were compared with contralateral kidneys stored in static cold storage (SCS) from the same donor with AKI during December 2019-June 2021. The study's primary aim is to assess the safety and feasibility of NMP in deceased donors with AKI. The primary outcome was DGF. Secondary outcomes were duration of DGF, biopsy-proven rejection, postoperative intrarenal resistive index, postoperative infections, hospital stay duration, primary nonfunction, and kidney function estimated glomerular filtrate rate at discharge, 3 mo, and 1 y.

Results

Five pairs of AKI kidneys (NMP versus SCS) were included in the final analysis. The results show no statistically significant differences in clinical outcomes between NMP versus SCS kidneys; however, NMP kidneys demonstrated slightly improved estimated glomerular filtrate rate at 3 mo (59.8 ± 5.93 [59] versus 75.20 ± 14.94 [74]) mL/min/1.73 m² (P < 0.065) and at the last follow-up (12-29 mo) (72.80 ± 10.71 [75]) versus (94 ± 22.67 [82]) mL/min/1.73 m² (P < 0.059) as compared with SCS kidneys. A higher proportion of NMP kidneys had normal intrarenal resistive index (0.5-0.7) and mild acute tubular injury on protocol biopsy, suggesting NMP is safe and feasible in deceased donors with acute kidney injury.

Conclusions

NMPs of AKI donor kidneys are safe and feasible. A larger cohort is required to explore the reconditioning effect of NMP on AKI kidneys.

Monobody adapter for functional antibody display on nanoparticles for adaptable targeted delivery applications

Vascular endothelial cells (ECs) play a central role in the pathophysiology of many diseases. The use of targeted nanoparticles (NPs) to deliver therapeutics to ECs could dramatically improve efficacy by providing elevated and sustained intracellular drug levels. However, achieving sufficient levels of NP targeting in human settings remains elusive. Here, we overcome this barrier by engineering a monobody adapter that presents antibodies on the NP surface in a manner that fully preserves their antigen-binding function. This system improves targeting efficacy in cultured ECs under flow by >1000-fold over conventional antibody immobilization using amine coupling and enables robust delivery of NPs to the ECs of human kidneys undergoing ex vivo perfusion, a clinical setting used for organ transplant. Our monobody adapter also enables a simple plug-and-play capacity that facilitates the evaluation of a diverse array of targeted NPs. This technology has the potential to simplify and possibly accelerate both the development and clinical translation of EC-targeted nanomedicines.

Normothermic machine perfusion of kidneys: current strategies and future perspectives

PURPOSE OF REVIEW

This review aims to summarize the latest original preclinical and clinical articles in the setting of normothermic machine perfusion (NMP) of kidney grafts.

RECENT FINDINGS

Kidney NMP can be safely translated into the clinical routine and there is increasing evidence that NMP may be beneficial in graft preservation especially in marginal kidney grafts. Due to the near-physiological state during NMP, this technology may be used as an ex-vivo organ assessment and treatment platform. There are reports on the application of mesenchymal stromal/stem cells, multipotent adult progenitor cells and microRNA during kidney NMP, with first data indicating that these therapies indeed lead to a decrease in inflammatory response and kidney injury. Together with the demonstrated possibility of prolonged ex-vivo perfusion without significant graft damage, NMP could not only be used as a tool to perform preimplant graft assessment. Some evidence exists that it truly has the potential to be a platform to treat and repair injured kidney grafts, thereby significantly reducing the number of declined organs.

SUMMARY

Kidney NMP is feasible and can potentially increase the donor pool not only by preimplant graft assessment, but also by ex-vivo graft treatment.

Normothermic Machine Perfusion in Renal Transplantation

Purpose of Review

Normothermic machine perfusion (NMP) is a promising new tool in kidney transplantation to improve the outcome of marginal donor kidney transplantation. This review examines the current evidence for NMP in clinical practice and considers how the technology may be used in the future.

Recent Findings and Summary

There is emerging evidence to suggest that NMP has the potential to expand the donor pool of transplantable organs. The safety and feasibility of NMP have been established in a number of clinical studies but more research is needed to optimise the perfusion conditions. NMP shows promise as a viability assessment tool with particular focus on biomarkers and imaging techniques which provide real-time information to facilitate transplantation decision-making. Moreover, the exciting development of new potential therapeutics such as cell and gene-based therapies which are deliverable during NMP may also improve and recondition grafts prior to implantation.

Novel Ex-Vivo Thrombolytic Reconditioning of Kidneys Retrieved 4 to 5 Hours After Circulatory Death

BACKGROUND

Due to organ shortage, many patients do not receive donor organs. The present novel thrombolytic technique utilizes organs from donors with uncontrolled donation after circulatory deaths (uDCD), with up to 4-5 h warm ischemia, without advanced cardiopulmonary resuscitation (aCPR) or extracorporeal circulation (EC) after death.

METHODS

The study group of pigs (n = 21) underwent simulated circulatory death. After 2 h, an ice slush was inserted into the abdomen. Kidneys were retrieved 4.5 h after death. Lys-plasminogen, antithrombin-III (ATIII), and alteplase (tPA) were injected through the renal arteries on the back table. Subsequent ex vivo perfusion at 15 °C was continued for 3 h, followed by 3 h with red blood cells (RBCs) at 32 °C. Perfusion outcome and histology were compared between uDCD kidneys, receiving no thrombolytic treatment (n = 8), and live donor kidneys (n = 7). The study kidneys were then transplanted into pigs as autologous grafts with a single functioning autologous kidney as the only renal support. uDCD control pigs (n = 8), receiving no ex vivo perfusion, served as controls.

RESULTS

Vascular resistance decreased to <200 mmHg/mL/min ( P < 0.0023) and arterial flow increased to >100 mL/100 g/min ( P < 0.00019) compared to controls. In total 13/21 study pigs survived for >10 days, while all uDCD control pigs died. Histology was preserved after reconditioning, and the creatinine level after 10 days was next to normal.

CONCLUSIONS

Kidneys from extended uDCD, not receiving aCPR/EC, can be salvaged using thrombolytic treatment to remove fibrin thrombi while preserving histology and enabling transplantation with a clinically acceptable early function.

Nanotherapeutics in transplantation: How do we get to clinical implementation?

Patients undergoing organ transplantation transition from one life-altering issue (organ dysfunction) to a lifelong commitment-immunosuppression. Regimens of immunosuppressive agents (ISAs) come with significant side effects and comorbidities. Recently, the use of nanoparticles (NPs) as a solution to the problems associated with the long-term and systemic use of ISAs in transplantation has emerged. This minireview describes the role of NPs in organ transplantation and discusses obstacles to clinical implementation and pathways to clinical translation.

Nanotechnology in Kidney and Islet Transplantation: An Ongoing, Promising Field

Organ transplantation has evolved rapidly in recent years as a reliable option for patients with end-stage organ failure. However, organ shortage, surgical risks, acute and chronic rejection reactions and long-term immunosuppressive drug applications and their inevitable side effects remain extremely challenging problems. The application of nanotechnology in medicine has proven highly successful and has unique advantages for diagnosing and treating diseases compared to conventional methods. The combination of nanotechnology and transplantation brings a new direction of thinking to transplantation medicine. In this article, we provide an overview of the application and progress of nanotechnology in kidney and islet transplantation, including nanotechnology for renal pre-transplantation preservation, artificial biological islets, organ imaging and drug delivery.

Renal Normothermic Machine Perfusion: The Road Toward Clinical Implementation of a Promising Pretransplant Organ Assessment Tool

The increased utilization of high-risk renal grafts for transplantation requires optimization of pretransplant organ assessment strategies. Current decision-making methods to accept an organ for transplantation lack overall predictive power and always contain an element of subjectivity. Normothermic machine perfusion (NMP) creates near-physiological conditions, which might facilitate a more objective assessment of organ quality before transplantation. NMP is rapidly gaining popularity, with various transplant centers developing their own NMP protocols and renal viability criteria. However, to date, no validated sets of on-pump viability markers exist nor are there unified NMP protocols. This review provides a critical overview of the fundamentals of current renal NMP protocols and proposes a framework to approach further development of ex vivo organ evaluation. We also comment on the potential logistical implications of routine clinical use of NMP, which is a more complex procedure compared with static cold storage or even hypothermic machine perfusion.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

A digital pathology tool for quantification of color features in histologic specimens

In preclinical research, histological analysis of tissue samples is often limited to qualitative or semiquantitative scoring assessments. The reliability of this analysis can be impaired by the subjectivity of these approaches, even when read by experienced pathologists. Furthermore, the laborious nature of manual image assessments often leads to the analysis being restricted to a relatively small number of images that may not accurately represent the whole sample. Thus, there is a clear need for automated image analysis tools that can provide robust and rapid quantification of histologic samples from paraffin-embedded or cryopreserved tissues. To address this need, we have developed a color image analysis algorithm (DigiPath) to quantify distinct color features in histologic sections. We demonstrate the utility of this tool across multiple types of tissue samples and pathologic features, and compare results from our program to other quantitative approaches such as color thresholding and hand tracing. We believe this tool will enable more thorough and reliable characterization of histological samples to facilitate better rigor and reproducibility in tissue-based analyses.

Endothelial Dysfunction Criteria in Critically Ill Children: The PODIUM Consensus Conference

OBJECTIVES

To review, analyze, and synthesize the literature on endothelial dysfunction in critically ill children with multiple organ dysfunction syndrome and to develop a consensus biomarker-based definition and diagnostic criteria.

DATA SOURCES

Electronic searches of PubMed and Embase were conducted from January 1992 to January 2020, using a combination of medical subject heading terms and key words to define concepts of endothelial dysfunction, pediatric critical illness, and outcomes.

STUDY SELECTION

Studies were included if they evaluated critically ill children with endothelial dysfunction, evaluated performance characteristics of assessment/scoring tools to screen for endothelial dysfunction, and assessed outcomes related to mortality, functional status, organ-specific outcomes, or other patient-centered outcomes. Studies of adults or premature infants (≤36 weeks gestational age), animal studies, reviews or commentaries, case series with sample size ≤10, and non-English language studies with the inability to determine eligibility criteria were excluded.

DATA EXTRACTION

Data were abstracted from each eligible study into a standard data extraction form along with risk of bias assessment.

DATA SYNTHESIS

We identified 62 studies involving 84 assessments of endothelial derived biomarkers indirectly linked to endothelial functions including leukocyte recruitment, inflammation, coagulation, and permeability. Nearly all biomarkers studied lacked specificity for vascular segment and organ systems. Quality assessment scores for the collected literature were low.

CONCLUSIONS

The Endothelial Subgroup concludes that there exists no single or combination of biomarkers to diagnose endothelial dysfunction in pediatric multiple organ dysfunction syndrome. Future research should focus on biomarkers more directly linked to endothelial functions and with specificity for vascular segment and organ systems.

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

Advances in Hypothermic and Normothermic Perfusion in Kidney Transplantation

Hypothermic and normothermic machine perfusion in kidney transplantation are purported to exert a beneficial effect on post-transplant outcomes compared to the traditionally used method of static cold storage. Kidney perfusion techniques provide a window for organ reconditioning and quality assessment. However, how best to deliver these preservation methods or improve organ quality has not yet been conclusively defined. This review summarises the promising advances in machine perfusion science in recent years, which have the potential to further improve early graft function and prolong graft survival.

Aggravation of fibrin deposition and microthrombus formation within the graft during kidney transplantation

In kidney transplantation, microthrombi and fibrin deposition may lead to local perfusion disorders and subsequently poor initial graft function. Microthrombi are often regarded as donor-derived. However, the incidence, time of development, and potential difference between living donor kidneys (LDK) and deceased donor kidneys(DDK), remains unclear. Two open-needle biopsies, taken at preimplantation and after reperfusion, were obtained from 17 LDK and 28 DDK transplanted between 2005 and 2008. Paraffin-embedded sections were immunohistochemically stained with anti-fibrinogen antibody. Fibrin deposition intensity in peritubular capillaries(PTC) and glomeruli was categorized as negative, weak, moderate or strong and the number of microthrombi/mm² was quantified. Reperfusion biopsies showed more fibrin deposition (20% to 100% moderate/strong, p < 0.001) and more microthrombi/mm² (0.97 ± 1.12 vs. 0.28 ± 0.53, p < 0.01) than preimplantation biopsies. In addition, more microthrombi/mm² (0.38 ± 0.61 vs. 0.09 ± 0.22, p = 0.02) and stronger fibrin intensity in glomeruli (28% vs. 0%, p < 0.01) and PTC (14% vs. 0%, p = 0.02) were observed in preimplantation DDK than LDK biopsies. After reperfusion, microthrombi/mm² were comparable (p = 0.23) for LDK (0.09 ± 0.22 to 0.76 ± 0.49, p = 0.03) and DDK (0.38 ± 0.61 to 0.90 ± 1.11, p = 0.07). Upon reperfusion, there is an aggravation of microthrombus formation and fibrin deposition within the graft. The prominent increase of microthrombi in LDK indicates that they are not merely donor-derived.

Normothermic Machine Perfusion (NMP) of the Liver - Current Status and Future Perspectives

A shortage of available organs for liver transplantation has led transplant surgeons and researchers to seek for innovative approaches in hepatoprotection and improvement of marginal allografts. The most exciting development in the past decade has been continuous mechanical perfusion of livers with blood or preservation solution to mitigate ischemia-reperfusion injury in contrast to the current standard of static cold storage. Two variations of machine perfusion have emerged in clinical practice. During hypothermic oxygenated perfusion the liver is perfused using a red blood cell-free perfusate at 2-10°C. In contrast, normothermic machine perfusion mimics physiologic liver perfusion using a red blood cell-based solution at 35.5-037.5°C, offering a multitude of potential advantages. Putative effects of normothermic perfusion include abrogation of hyperfibrinolysis after reperfusion and inflammation, glycogen repletion, and regeneration of adenosine triphosphate. Research in normothermic machine perfusion focuses on development of biomarkers predicting allograft quality and susceptibility to ischemia-reperfusion injury. Moreover, normothermic perfusion of marginal allografts allows for application of a variety of therapeutic interventions potentially enhancing organ quality. Both methods need to be subjected to translational investigation and evaluation in clinical trials. A clear advantage is transformation of an emergency procedure at night into a planned daytime surgery. Current clinical trials suggest that normothermic perfusion not only increases the use of hepatic allografts but is also associated with milder ischemia-reperfusion injury, resulting in a reduced risk of early allograft dysfunction and less biliary complications, including ischemic cholangiopathy, compared to static cold storage. The aim of this review is to give a concise overview of normothermic machine perfusion and its current applications, benefits, and possible advances in the future.