Will cell therapies provide the solution for the shortage of transplantable organs?

A proof-of-concept study in small and large animal models for coupling liver normothermic machine perfusion with mesenchymal stromal cell bioreactors

To fully harness mesenchymal-stromal-cells (MSCs)' benefits during Normothermic Machine Perfusion (NMP), we developed an advanced NMP platform coupled with a MSC-bioreactor and investigated its bio-molecular effects and clinical feasibility using rat and porcine models. The study involved three work packages: 1) Development (n = 5): MSC-bioreactors were subjected to 4 h-liverless perfusion; 2) Rat model (n = 10): livers were perfused for 4 h on the MSC-bioreactor-circuit or with the standard platform; 3) Porcine model (n = 6): livers were perfused using a clinical device integrated with a MSC-bioreactor or in its standard setup. MSCs showed intact stem-core properties after liverless-NMP. Liver NMP induced specific, liver-tailored, changes in MSCs' secretome. Rat livers exposed to bioreactor-based perfusion produced more bile, released less damage and pro-inflammatory biomarkers, and showed improved mithocondrial function than those subjected to standard NMP. MSC-bioreactor integration into a clinical device resulted in no machine failure and perfusion-related injury. This proof-of-concept study presents a novel MSC-based liver NMP platform that could reduce the deleterious effects of ischemia/reperfusion before transplantation.

Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion

BACKGROUND

Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation.

METHODS

Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54 h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600 μg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1 + 2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition.

FINDINGS

Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition.

INTERPRETATION

We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR.

FUNDING

The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Application of Mesenchymal Stem Cells During Machine Perfusion: An Emerging Novel Strategy for Organ Preservation

Although solid organ transplantation remains the definitive management for patients with end-stage organ failure, this ultimate treatment has been limited by the number of acceptable donor organs. Therefore, efforts have been made to expand the donor pool by utilizing marginal organs from donation after circulatory death or extended criteria donors. However, marginal organs are susceptible to ischemia-reperfusion injury (IRI) and entail higher requirements for organ preservation. Recently, machine perfusion has emerged as a novel preservation strategy for marginal grafts. This technique continually perfuses the organs to mimic the physiologic condition, allows the evaluation of pretransplant graft function, and more excitingly facilitates organ reconditioning during perfusion with pharmacological, gene, and stem cell therapy. As mesenchymal stem cells (MSCs) have anti-oxidative, immunomodulatory, and regenerative properties, mounting studies have demonstrated the therapeutic effects of MSCs on organ IRI and solid organ transplantation. Therefore, MSCs are promising candidates for organ reconditioning during machine perfusion. This review provides an overview of the application of MSCs combined with machine perfusion for lung, kidney, liver, and heart preservation and reconditioning. Promising preclinical results highlight the potential clinical translation of this innovative strategy to improve the quality of marginal grafts.

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.

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

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