Enzymatic conversion of human blood group A kidneys to universal blood group O.

ABO blood group compatibility restrictions present the first barrier to donor-recipient matching in kidney transplantation. Here, we present the use of two enzymes, FpGalNAc deacetylase and FpGalactosaminidase, from the bacterium Flavonifractor plautii to enzymatically convert blood group A antigens from the renal vasculature of human kidneys to 'universal' O-type. Using normothermic machine perfusion (NMP) and hypothermic machine perfusion (HMP) strategies, we demonstrate blood group A antigen loss of approximately 80% in as little as 2 h NMP and HMP. Furthermore, we show that treated kidneys do not bind circulating anti-A antibodies in an ex vivo model of ABO-incompatible transplantation and do not activate the classical complement pathway. This strategy presents a solution to the donor organ shortage crisis with the potential for direct clinical translation to reduce waiting times for patients with end stage renal disease.

Normothermic machine perfusion versus static cold storage in donation after circulatory death kidney transplantation: a randomized controlled trial.

Kidney transplantation is the optimal treatment for end-stage renal disease, but it is still severely limited by a lack of suitable organ donors. Kidneys from donation after circulatory death (DCD) donors have been used to increase transplant rates, but these organs are susceptible to cold ischemic injury in the storage period before transplantation, the clinical consequence of which is high rates of delayed graft function (DGF). Normothermic machine perfusion (NMP) is an emerging technique that circulates a warmed, oxygenated red-cell-based perfusate through the kidney to maintain near-physiological conditions. We conducted a randomized controlled trial to compare the outcome of DCD kidney transplants after conventional static cold storage (SCS) alone or SCS plus 1-h NMP. A total of 338 kidneys were randomly allocated to SCS (n = 168) or NMP (n = 170), and 277 kidneys were included in the final intention-to-treat analysis. The primary endpoint was DGF, defined as the requirement for dialysis in the first 7 d after transplant. The rate of DGF was 82 of 135 (60.7%) in NMP kidneys versus 83 of 142 (58.5%) in SCS kidneys (adjusted odds ratio (95% confidence interval) 1.13 (0.69-1.84); P = 0.624). NMP was not associated with any increase in transplant thrombosis, infectious complications or any other adverse events. A 1-h period of NMP at the end of SCS did not reduce the rate of DGF in DCD kidneys. NMP was demonstrated to be feasible, safe and suitable for clinical application. Trial registration number: ISRCTN15821205 .

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.

The Effects of Free Heme on Functional and Molecular Changes During Ex Vivo Normothermic Machine Perfusion of Human Kidneys.

Normothermic machine perfusion (NMP) is a technique of kidney preservation designed to restore cellular metabolism after cold ischemia. Kidneys are perfused with an oxygenated banked red blood cell (RBC) based solution for 1h at 36°C. During NMP, RBCs can become damaged, releasing free heme into the perfusate. This can act as a damage-associated molecular pattern (DAMP) activating inflammatory signalling pathways. The aim of this study was to measure the levels of free heme during NMP, assess the effect on kidney function and determine any association with inflammatory and stress related gene expression. Levels of free heme were measured in perfusate samples from a series of donation after circulatory death (DCD) kidneys undergoing NMP as part of a randomised controlled trial (RCT). The age of RBCs and levels of free heme were correlated with perfusion parameters. Changes in gene expression were analysed in a series of kidneys declined for transplantation using the NanoString nCounter Organ Transplant Panel and qRT-PCR. Older units of RBCs were associated with higher levels of free heme and levels increased significantly during NMP (Pre 8.56 ± 7.19µM vs 26.29 ± 15.18µM, P<0.0001). There was no association with levels of free heme and perfusion parameters during NMP (P > 0.05). Transcriptional and qPCR analysis demonstrated the upregulation of differentially expressed genes associated with apoptosis (FOS and JUN), inflammatory cytokines (IL-6, SOCS3, ATF3), chemokines (CXCL8, CXCL2, CC3/L1) and oxidative stress (KLF4) after NMP. However, these did not correlate with levels of free heme (P >0.05). A significant amount of free heme can be detected in the perfusate before and after NMP particularly when older units of red cells are used. Although transcriptional analysis demonstrated significant upregulation of genes involved with apoptotic, inflammatory and oxidative pathways these were not associated with high levels of free heme.

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.

MicroRNA antagonist therapy during normothermic machine perfusion of donor kidneys.

Normothermic machine perfusion (NMP) is a novel clinical approach to overcome the limitations of traditional hypothermic organ preservation. NMP can be used to assess and recondition organs prior to transplant and is the subject of clinical trials in solid organ transplantation. In addition, NMP provides an opportunity to deliver therapeutic agents directly to the organ, thus avoiding many limitations associated with systemic treatment of the recipient. We report the delivery of oligonucleotide-based therapy to human kidneys during NMP, in this case to target microRNA function (antagomir). An antagomir targeting mir-24-3p localized to the endothelium and proximal tubular epithelium. Endosomal uptake during NMP conditions facilitated antagomir co-localization with proteins involved in the RNA-induced silencing complex (RISC) and demonstrated engagement of the miRNA target. This pattern of uptake was not seen during cold perfusion. Targeting mir-24-3p action increased expression of genes controlled by this microRNA, including heme oxygenase-1 and sphingosine-1-phosphate receptor 1. The expression of genes not under the control of mir-24-3p was unchanged, indicating specificity of the antagomir effect. In summary, this is the first report of ex vivo gymnotic delivery of oligonucleotide to the human kidney and demonstrates that NMP provides the platform to bind and block detrimental microRNAs in donor kidneys prior to transplantation.

Extracellular vesicles in kidney transplantation: a state-of-the-art review.

Kidney transplantation is the optimal treatment for patients with kidney failure; however, early detection and timely treatment of graft injury remain a challenge. Precise and noninvasive techniques of graft assessment and innovative therapeutics are required to improve kidney transplantation outcomes. Extracellular vesicles (EVs) are lipid bilayer-delimited particles with unique biosignatures and immunomodulatory potential, functioning as intermediaries of cell signalling. Promising evidence exists for the potential of EVs to develop precision diagnostics of graft dysfunction, and prognostic biomarkers for clinician decision making. The inherent targeting characteristics of EVs and their low immunogenic and toxicity profiles combined with their potential as vehicles for drug delivery make them ideal targets for development of therapeutics to improve kidney transplant outcomes. In this review, we summarize the current evidence for EVs in kidney transplantation, discuss common methodological principles of EV isolation and characterization, explore upcoming innovative approaches in EV research, and discuss challenges and opportunities to enable translation of research findings into clinical practice.

A systematic review of living kidney donor enhanced recovery after surgery.

Enhanced recovery after surgery (ERAS) reduces complications and shortens hospital stay without increasing readmission or mortality. However, its role in living donor nephrectomy (LDN) has not yet been defined. Medline, Embase, CINAHL, PsycINFO, and Cochrane Central were searched prior to 08/01/21 for all randomized controlled and cohort studies comparing ERAS to standard of care in LDN. The study was registered on PROSPERO (CRD: CRD42019141706). One thousand, three hundred seventy-seven patients were identified from 14 studies (698 patients with ERAS and 679 patients without). There were considerable differences in the protocols used, and compliance with general ERAS recommendations was poor. Meta-analysis of laparoscopic procedures (including hand- and robot-assisted) revealed that duration of stay was significantly reduced by 0.98 days with ERAS (95% CI = 0.36-1.60, P = .002) and opiate requirement by 32.4 mg (95% CI = 1.1-63.7, P = .04). There was no significant difference n readmission rates or complications. Quality of evidence was low to moderate assessed using the GRADE tool. This review suggests there is a positive benefit of ERAS in laparoscopic LDN. However, there was considerable variation in ERAS protocols used, and the quality of evidence was low; as such, a guideline for ERAS in LDN should be developed and validated.

Advances in Kidney Preservation Techniques and Their Application in Clinical Practice.

The use of cold preservation solutions to rapidly flush and cool the kidney followed by static cold storage in ice has been the standard kidney preservation technique for the last 50 y. Nonetheless, changing donor demographics that include organs from extended criteria donors and donation after circulatory death donors have led to the adoption of more diverse techniques of preservation. Comparison of hypothermic machine perfusion and static cold storage techniques for deceased donor kidneys has long been debated and is still contested by some. The recent modification of hypothermic machine perfusion techniques with the addition of oxygen or perfusion at subnormothermic or near-normothermic temperatures are promising strategies that are emerging in clinical practice. In addition, the use of normothermic regional perfusion to resuscitate abdominal organs of donation after circulatory death donors in situ before cold flushing is also increasingly being utilized. This review provides a synopsis of the different types of preservation techniques including their mechanistic effects and the outcome of their application in clinical practice for different types of donor kidney.

Treatment of transplant kidneys during machine perfusion.

The increasing use of donation after circulatory death (DCD) and extended criteria donor (ECD) organs has raised awareness of the need to improve the quality of kidneys for transplantation. Treating kidneys during the preservation interval could improve early and long-term graft function and survival. Dynamic modes of preservation including hypothermic machine perfusion (HMP) and normothermic machine perfusion (NMP) may provide the functional platforms to treat these kidneys. Therapies in the field of regenerative medicine including cellular therapies and genetic modification and the application of biological agents targeting ischaemia reperfusion injury (IRI) and acute rejection are a growing area of research. This review reports on the application of cellular and gene manipulating therapies, nanoparticles, anti-inflammatory agents, anti-thrombolytic agents and monoclonal antibodies administered during HMP and NMP in experimental models. The review also reports on the clinical effectiveness of several biological agents administered during HMP. All of the experimental studies provide proof of principle that therapies can be successfully delivered during HMP and NMP. However, few have examined the effects after transplantation. Evidence for clinical application during HMP is sparse and only one study has demonstrated a beneficial effect on graft function. More investigation is needed to develop perfusion strategies and investigate the different experimental approaches.

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

Thousands of kidneys from higher-risk donors are discarded annually because of the increased likelihood of complications posttransplant. Given the severe organ shortage, there is a critical need to improve utilization of these organs. To this end, normothermic machine perfusion (NMP) has emerged as a platform for ex vivo assessment and potential repair of marginal organs. In a recent study of 8 transplant-declined human kidneys on NMP, we discovered microvascular obstructions that impaired microvascular blood flow. However, the nature and physiologic impact of these lesions were unknown. Here, in a study of 39 human kidneys, we have identified that prolonged cold storage of human kidneys induces accumulation of fibrinogen within tubular epithelium. Restoration of normoxic conditions-either ex vivo during NMP or in vivo following transplant-triggered intravascular release of fibrinogen correlating with red blood cell aggregation and microvascular plugging. Combined delivery of plasminogen and tissue plasminogen activator during NMP lysed the plugs leading to a significant reduction in markers of renal injury, improvement in indicators of renal function, and improved delivery of vascular-targeted nanoparticles. Our study suggests a new mechanism of cold storage injury in marginal organs and provides a simple treatment with immediate translational potential.

Normothermic kidney perfusion: An overview of protocols and strategies.

Normothermic machine perfusion (NMP) technologies are emerging as an important adjunct in organ preservation and transplantation. NMP can enable the reduction or avoidance of cold ischemia and allows for pretransplant measurement of function and metabolic status to assess the suitability of the organ for transplantation. The key requirement of NMP is to provide an environment that is protective to the organ, ensures optimal oxygen delivery and supports metabolic function. Red blood cell-based solutions, artificial hemoglobin solutions, and acellular solutions have all been utilized in NMP. However, there is no clear consensus on perfusion protocols. A period of NMP after hypothermic preservation is the most commonly used strategy. As an alternative, several groups have developed and tested the feasibility of more prolonged periods of NMP. There are only a few reports of the application of NMP in clinical kidney transplantation and each uses different approach and conditions. This review details the rationale for NMP protocols considering duration of NMP and different perfusate compositions in experimental and clinical models. We also include a discussion on the mechanistic action of NMP, comparison of subnormothermic and hypothermic conditions, the different logistical approaches and future requirements.

Cytokine absorption during human kidney perfusion reduces delayed graft function-associated inflammatory gene signature.

Transplantation is the optimal treatment for most patients with end-stage kidney disease but organ shortage is a major challenge. Normothermic machine perfusion (NMP) has been used to recondition marginal organs; however, mechanisms by which NMP might benefit organs are not well understood. Using pairs of human kidneys obtained from the same donor, we compared the effect of NMP with that of cold storage on the global kidney transcriptome. We found that cold storage led to a global reduction in gene expression, including inflammatory pathway genes and those required for energy generation processes, such as oxidative phosphorylation (OXPHOS). In contrast, during NMP, there was marked upregulation OXPHOS genes, but also of a number of immune and inflammatory pathway genes. Using biopsies from kidneys undergoing NMP that were subsequently transplanted, we found that higher inflammatory gene expression occurred in organs with prolonged delayed graft function (DGF). Therefore, we used a hemoadsorber (HA) to remove pro-inflammatory cytokines. This attenuated inflammatory gene expression increased OXPHOS pathway genes and had potentially clinically important effects in reducing the expression of a DGF-associated gene signature. Together, our data suggest that adsorption of pro-inflammatory mediators from the perfusate represents a potential intervention which may improve organ viability.

Novel delivery of cellular therapy to reduce ischemia reperfusion injury in kidney transplantation.

Ex vivo normothermic machine perfusion (NMP) of donor kidneys prior to transplantation provides a platform for direct delivery of cellular therapeutics to optimize organ quality prior to transplantation. Multipotent Adult Progenitor Cells (MAPC® ) possess potent immunomodulatory properties that could minimize ischemia reperfusion injury. We investigated the potential capability of MAPC cells in kidney NMP. Pairs (5) of human kidneys, from the same donor, were simultaneously perfused for 7 hours. Kidneys were randomly allocated to receive MAPC treatment or control. Serial samples of perfusate, urine, and tissue biopsies were taken for comparison. MAPC-treated kidneys demonstrated improved urine output (P = .009), decreased expression of injury biomarker NGAL (P = .012), improved microvascular perfusion on contrast-enhanced ultrasound (cortex P = .019, medulla P = .001), downregulation of interleukin (IL)-1ß (P = .050), and upregulation of IL-10 (P < .047) and Indolamine-2, 3-dioxygenase (P = .050). A chemotaxis model demonstrated decreased neutrophil recruitment when stimulated with perfusate from MAPC-treated kidneys (P < .001). Immunofluorescence revealed prelabeled MAPC cells in the perivascular space of kidneys during NMP. We report the first successful delivery of cellular therapy to a human kidney during NMP. Kidneys treated with MAPC cells demonstrate improvement in clinically relevant parameters and injury biomarkers. This novel method of cell therapy delivery provides an exciting opportunity to recondition organs prior to transplantation.