Delivery of genetic load during ex situ liver machine perfusion with potential for CRISPR-Cas9 gene editing: An innovative strategy for graft treatment

Designer Organs: Ethical Genetic Modifications in the Era of Machine Perfusion

Gene therapy is a rapidly developing field, finally yielding clinical benefits. Genetic engineering of organs for transplantation may soon be an option, thanks to convergence with another breakthrough technology, ex vivo machine perfusion (EVMP). EVMP allows access to the functioning organ for genetic manipulation prior to transplant. EVMP has the potential to enhance genetic engineering efficiency, improve graft survival, and reduce posttransplant complications. This will enable genetic modifications with a vast variety of applications, while raising questions on the ethics and regulation of this emerging technology. This review provides an in-depth discussion of current methodologies for delivering genetic vectors to transplantable organs, particularly focusing on the enabling role of EVMP. Organ-by-organ analysis and key characteristics of various vector and treatment options are assessed. We offer a road map for research and clinical translation, arguing that achieving scientific benchmarks while creating anticipatory governance is necessary to secure societal benefit from this technology.

Expanding the Use of Ex Situ Organ Machine Perfusion Beyond Transplantation

Machine perfusion preservation of grafts has become the gold standard organ preservation method. It has been developed to improve the quality of grafts due to the increasing gap between demand and supply of organs for transplantation. Following successful long-term machine perfusion preservation with automated commercial devices developed for preservation of organs for transplantation, there is increasing interest in utilizing perfused discarded human organs and xenografts for a variety of purposes beyond transplantation including gene therapy and modulation, drug testing, chemotherapy, ex vivo surgery, organ supporting systems, bioengineering, and surgical training and education. Here, we review all current and potential applications of machine perfusion preservation.

Ex vivo machine perfusion as a platform for lentiviral gene delivery in rat livers

Developing new strategies for local monitoring and delivery of immunosuppression is critical to making allografts safer and more accessible. Ex vivo genetic modification of grafts using machine perfusion presents a promising approach to improve graft function and modulate immune responses while minimizing risks of off-target effects and systemic immunogenicity in vivo. This proof-of-concept study demonstrates the feasibility of using normothermic machine perfusion (NMP) to mimic in vitro conditions for effective gene delivery. In this study, lentiviral vectors encoding the secreted biomarker Gaussia Luciferase (GLuc) and red fluorescent protein (RFP) were introduced ex vivo to rodent livers during a 72-h machine perfusion protocol. After an initial 24-h exposure to viral vectors, the organs were maintained in perfusion for an additional 48 h to monitor gene expression, aligning with in vitro benchmarks. Control livers were perfused in similar fashion, but without viral injections. Virally perfused livers exhibited nearly a 10-fold increase in luminescence compared to controls (p < 0.0001), indicating successful genetic modification of the organs. These findings validate the use of machine perfusion systems and viral vectors to genetically engineer whole organs ex vivo, laying the groundwork for a broad range of applications in transplantation through genetic manipulation of organ systems. Future studies will focus on refining this technology to enhance precision in gene expression and explore its implications for clinical translation.

Ex Vivo Machine Perfusion as a Platform for Lentiviral Gene Delivery in Rat Livers

Developing new strategies for local monitoring and delivery of immunosuppression is critical to making allografts safer and more accessible. Ex vivo genetic modification of grafts using machine perfusion presents a promising approach to improve graft function and modulate immune responses while minimizing risks of off-target effects and systemic immunogenicity in vivo. This proof-of-concept study demonstrates the feasibility of using normothermic machine perfusion (NMP) to mimic in vitro conditions for effective gene delivery. In this study, lentiviral vectors carrying biosensor constructs with Gaussia Luciferase (GLuc) were introduced to rodent livers during a 72-hour perfusion period, with a targeted delivery of 3 × 107 infection units (IU). Following the initial 24-hour exposure required for viral transduction, an additional 48 hours was necessary to observe gene expression, analogous to in vitro benchmarks. The perfused livers displayed significantly increased luminescence compared to controls, illustrating successful genetic modification. These findings validate the ex vivo use of lentiviral particles in a rodent liver model and lay the groundwork for a broad range of applications through genetic manipulation of organ systems. Future studies will focus on refining this technology to enhance precision in gene expression and explore its implications for clinical transplantation.

What Is Hot and New in Basic and Translational Science in Liver Transplantation in 2023? Report of the Basic and Translational Research Committee of the International Liver Transplantation Society

The 2023 Joint Annual Congress of the International Liver Transplantation Society, European Liver and Intestine Transplant Association, and Liver Intensive Care Group of Europe were held in Rotterdam, the Netherlands, from May 3 to 6, 2023. This year, all speakers were invited to attend the Congress in person for the first time since the COVID-19 pandemic. The congress was attended by 1159 registered delegates from 54 countries representing 5 continents, with the 10 countries comprising the bulk of the delegates. Of the 647 abstracts initially submitted, 542 were eventually presented at the meeting, coming from 38 countries (mainly North America, Europe, and Asia) and 85% of them (462 abstracts) came from only 10 countries. Fifty-three (9.8%) abstracts, originated from 17 countries, were submitted under the Basic/Translational Scientific Research category, a similar percentage as in 2022. Abstracts presented at the meeting were classified as (1) ischemia and reperfusion injury, (2) machine perfusion, (3) bioengineering and liver regeneration, (4) transplant oncology, (5) novel biomarkers in liver transplantation, (6) liver immunology (rejection and tolerance), and (7) artificial intelligence and machine learning. Finally, we evaluated the number of abstracts commented in the Basic and Translational Research Committee-International Liver Transplantation Society annual reports over the past 5 y that resulted in publications in peer-reviewed journals to measure their scientific impact in the field of liver transplantation.

AAV9-mediated gene delivery to liver grafts during static cold storage in a rat liver transplant model

Introduction

Recombinant adeno-associated virus (rAAV) is a novel strategy used clinically for gene delivery, but has not been characterized in the context of organ transplantation. We sought to determine the efficacy of rAAV-mediated gene delivery during static cold storage (SCS) prior to liver transplantation.

Methods

A triple-plasmid transfection protocol was used to produce rAAV subtype-9 vectors containing firefly luciferase genomes in HEK293 cells. Lewis rat liver grafts were flushed and stored in cold HTK solution. Three experimental groups received rAAV at different doses, administered via the portal vein as a bolus during SCS. A control group did not receive rAAV (N = 2). Recipients then underwent syngeneic liver transplantation. Bioluminescence imaging to quantify in vivo luciferase expression was performed on post-operative days 7, 14, 28, and 56.

Results

Control animals demonstrated no bioluminescent activity, while animals receiving rAAV-treated livers had increasing bioluminescence, peaking at four weeks but sustained to the eight-week endpoint. This result was confirmed by experimental endpoint tissue luciferase activity assay.

Discussion

rAAV mediates gene transduction in liver grafts when administered during SCS and has potential for gene therapy applications in solid organ transplantation.

Observations and findings during the development of a subnormothermic/normothermic long-term ex vivo liver perfusion machine

BACKGROUND

Ex situliver machine perfusion at subnormothermic/normothermic temperature isincreasingly applied in the field of transplantation to store and evaluateorgans on the machine prior transplantation. Currently, various perfusionconcepts are in clinical and preclinical applications. Over the last 6 years ina multidisciplinary team, a novel blood based perfusion technology wasdeveloped to keep a liver alive and metabolically active outside of the bodyfor at least one week.

METHODS

Within thismanuscript, we present and compare three scenarios (Group 1, 2 and 3) we werefacing during our research and development (R&D) process, mainly linked tothe measurement of free hemoglobin and lactate in the blood based perfusate. Apartfrom their proven value in liver viability assessment (ex situ), these twoparameters are also helpful in R&D of a long-term liver perfusion machine and moreover supportive in the biomedical engineering process.

RESULTS

Group 1 ("good" liver on the perfusion machine) represents the best liver clearance capacity for lactate and free hemoglobin wehave observed. In contrast to Group 2 ("poor" liver on the perfusion machine), that has shown the worst clearance capacity for free hemoglobin. Astonishingly,also for Group 2, lactate is cleared till the first day of perfusion andafterwards, rising lactate values are detected due to the poor quality of theliver. These two perfusate parametersclearly highlight the impact of the organ quality/viability on the perfusion process. Whereas Group 3 is a perfusion utilizing a blood loop only (without a liver).

CONCLUSION

Knowing the feasible ranges (upper- and lower bound) and the courseover time of free hemoglobin and lactate is helpful to evaluate the quality ofthe organ perfusion itself and the maturity of the developed perfusion device. Freehemoglobin in the perfusate is linked to the rate of hemolysis that indicates how optimizing (gentle blood handling, minimizing hemolysis) the perfusion machine actually is. Generally, a reduced lactate clearancecapacity can be an indication for technical problems linked to the blood supplyof the liver and therefore helps to monitor the perfusion experiments.Moreover, the possibility is given to compare, evaluate and optimize developed liverperfusion systems based on the given ranges for these two parameters. Otherresearch groups can compare/quantify their perfusate (blood) parameters withthe ones in this manuscript. The presented data, findings and recommendations willfinally support other researchers in developing their own perfusion machine ormodifying commercially availableperfusion devices according to their needs.

Modifying organs with gene therapy and gene modulation in the age of machine perfusion

PURPOSE OF REVIEW

This review aims to highlight current advances in gene therapy methods, describing advances in CRISPR-Cas9 gene editing and RNA interference in relevance to liver transplantation, and machine perfusion.

RECENT FINDINGS

In order to minimize rejection, increase the donor pool of available organs, and minimize the effects of ischemia-reperfusion injury, gene therapy and gene modification strategies are, thus, required in the context of liver transplantation.

SUMMARY

Gene therapy has been used successfully in a diverse array of diseases, and, more recently, this technique has gained interest in the field of organ transplantation. Biological and logistical challenges reduce the rate of successful procedures, increasing the waiting list even more. We explore the exciting future implications of customized gene therapy in livers using machine perfusion, including its potential to create a future in which organs destined for transplant are individualized to maximize both graft and recipient longevity.

Gene Therapy: Will the Promise of Optimizing Lung Allografts Become Reality?

Lung transplantation is the definitive therapy for patients living with end-stage lung disease. Despite significant progress made in the field, graft survival remains the lowest of all solid organ transplants. Additionally, the lung has among the lowest of organ utilization rates-among eligible donors, only 22% of lungs from multi-organ donors were transplanted in 2019. Novel strategies are needed to rehabilitate marginal organs and improve graft survival. Gene therapy is one promising strategy in optimizing donor allografts. Over-expression or inhibition of specific genes can be achieved to target various pathways of graft injury, including ischemic-reperfusion injuries, humoral or cellular rejection, and chronic lung allograft dysfunction. Experiments in animal models have historically utilized adenovirus-based vectors and the majority of literature in lung transplantation has focused on overexpression of IL-10. Although several strategies were shown to prevent rejection and prolong graft survival in preclinical models, none have led to clinical translation. The past decade has seen a renaissance in the field of gene therapy and two AAV-based in vivo gene therapies are now FDA-approved for clinical use. Concurrently, normothermic ex vivo machine perfusion technology has emerged as an alternative to traditional static cold storage. This preservation method keeps organs physiologically active during storage and thus potentially offers a platform for gene therapy. This review will explore the advantages and disadvantages of various gene therapy modalities, review various candidate genes implicated in various stages of allograft injury and summarize the recent efforts in optimizing donor lungs using gene therapy.

Delivering siRNA Compounds During HOPE to Modulate Organ Function: A Proof-of-Concept Study in a Rat Liver Transplant Model

BACKGROUND

Apoptosis contributes to the severity of ischemia-reperfusion injury (IRI), limiting the use of extended criteria donors in liver transplantation (LT). Machine perfusion has been proposed as a platform to administer specific therapies to improve graft function. Alternatively, the inhibition of genes associated with apoptosis during machine perfusion could alleviate IRI post-LT. The aim of the study was to investigate whether inhibition of an apoptosis-associated gene (FAS) using a small interfering RNA (siRNA) approach could alleviate IRI in a rat LT model.

METHODS

In 2 different experimental protocols, FASsiRNA (500 µg) was administered to rat donors 2 h before organ procurement, followed by 22 h of static cold storage, (SCS) or was added to the perfusate during 1 h of ex situ hypothermic oxygenated perfusion (HOPE) to livers previously preserved for 4 h in SCS.

RESULTS

Transaminase levels were significantly lower in the SCS-FASsiRNA group at 24 h post-LT. Proinflammatory cytokines (interleukin-2, C-X-C motif chemokine 10, tumor necrosis factor alpha, and interferon gamma) were significantly decreased in the SCS-FASsiRNA group, whereas the interleukin-10 anti-inflammatory cytokine was significantly increased in the HOPE-FASsiRNA group. Liver absorption of FASsiRNA after HOPE session was demonstrated by confocal microscopy; however, no statistically significant differences on the apoptotic index, necrosis levels, and FAS protein transcription between treated and untreated groups were observed.

CONCLUSIONS

FAS inhibition through siRNA therapy decreases the severity of IRI after LT in a SCS protocol; however the association of siRNA therapy with a HOPE perfusion model is very challenging. Future studies using better designed siRNA compounds and appropriate doses are required to prove the siRNA therapy effectiveness during liver HOPE liver perfusion.