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

Graft repair during machine perfusion: a current overview of strategies

PURPOSE OF REVIEW

With changing donor characteristics (advanced age, obesity), an increase in the use of extended criteria donor (ECD) livers in liver transplantation is seen. Machine perfusion allows graft viability assessment, but still many donor livers are considered nontransplantable. Besides being used as graft viability assessment tool, ex situ machine perfusion offers a platform for therapeutic strategies to ameliorate grafts prior to transplantation. This review describes the current landscape of graft repair during machine perfusion.

RECENT FINDINGS

Explored anti-inflammatory therapies, including inflammasome inhibitors, hemoabsorption, and cellular therapies mitigate the inflammatory response and improve hepatic function. Cholangiocyte organoids show promise in repairing the damaged biliary tree. Defatting during normothermic machine perfusion shows a reduction of steatosis and improved hepatobiliary function compared to nontreated livers. Uptake of RNA interference therapies during machine perfusion paves the way for an additional treatment modality.

SUMMARY

The possibility to repair injured donor livers during ex situ machine perfusion might increase the utilization of ECD-livers. Application of defatting agents is currently explored in clinical trials, whereas other therapeutics require further research or optimization before entering clinical research.

The Coming Age of Antisense Oligos for the Treatment of Hepatic Ischemia/Reperfusion (IRI) and Other Liver Disorders: Role of Oxidative Stress and Potential Antioxidant Effect

Imbalances in the redox state of the liver arise during metabolic processes, inflammatory injuries, and proliferative liver disorders. Acute exposure to intracellular reactive oxygen species (ROS) results from high levels of oxidative stress (OxS) that occur in response to hepatic ischemia/reperfusion injury (IRI) and metabolic diseases of the liver. Antisense oligonucleotides (ASOs) are an emerging class of gene expression modulators that target RNA molecules by Watson-Crick binding specificity, leading to RNA degradation, splicing modulation, and/or translation interference. Here, we review ASO inhibitor/activator strategies to modulate transcription and translation that control the expression of enzymes, transcription factors, and intracellular sensors of DNA damage. Several small-interfering RNA (siRNA) drugs with N-acetyl galactosamine moieties for the liver have recently been approved. Preclinical studies using short-activating RNAs (saRNAs), phosphorodiamidate morpholino oligomers (PMOs), and locked nucleic acids (LNAs) are at the forefront of proof-in-concept therapeutics. Future research targeting intracellular OxS-related pathways in the liver may help realize the promise of precision medicine, revolutionizing the customary approach to caring for and treating individuals afflicted with liver-specific conditions.

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.

Ex Vivo Gene Therapy in Organ Transplantation: Considerations and Clinical Translation

Ex vivo machine perfusion (EVMP) is rapidly growing in utility during solid organ transplantation. This form of organ preservation is transforming how organs are allocated and expanding the definition of what is considered a suitable organ for transplantation in comparison with traditional static cold storage. All major organs (heart, lung, liver, kidney) have been influenced by this advanced method of organ preservation. This technology also serves as an unprecedented platform for effective administration of advanced therapeutics, including gene therapies, during organ transplantation to optimize and recondition organs ex vivo in an isolated manner. Applying gene therapy interventions through EVMP introduces different considerations and challenges that are unique from gene therapies designed for systemic administration. Considerations involving vector (choice, dose, toxicity), perfusate composition, and perfusion circuit components should be evaluated when developing a gene therapy to administer in this setting. This review explores these aspects and discusses clinical applications in transplantation where gene therapy interventions can be developed relevant to heart, lung, liver, and kidney donor grafts.

Focusing on Ischemic Reperfusion Injury in the New Era of Dynamic Machine Perfusion in Liver Transplantation

Liver transplantation is the most effective treatment for end-stage liver disease. Transplant indications have been progressively increasing, with a huge discrepancy between the supply and demand of optimal organs. In this context, the use of extended criteria donor grafts has gained importance, even though these grafts are more susceptible to ischemic reperfusion injury (IRI). Hepatic IRI is an inherent and inevitable consequence of all liver transplants; it involves ischemia-mediated cellular damage exacerbated upon reperfusion and its severity directly affects graft function and post-transplant complications. Strategies for organ preservation have been constantly improving since they first emerged. The current gold standard for preservation is perfusion solutions and static cold storage. However, novel approaches that allow extended preservation times, organ evaluation, and their treatment, which could increase the number of viable organs for transplantation, are currently under investigation. This review discusses the mechanisms associated with IRI, describes existing strategies for liver preservation, and emphasizes novel developments and challenges for effective organ preservation and optimization.

End-ischemic hypothermic oxygenated machine perfusion does not improve renal outcome following liver transplantation from aged donors: A single-center retrospective report

BACKGROUND

Organ transplantation using grafts from elderly donors entails a higher risk for severe ischemia-reperfusion injury (IRI). Advanced IRI after liver transplantation (LT) seems to be associated with the development of acute kidney injury (AKI). We studied if end-ischemic hypothermic oxygenated machine perfusion (HOPE) of liver grafts, aimed at mitigating liver IRI, impacts on the frequency and severity of AKI after LT.

METHODS

LTs performed at our center between January 2017 and December 2022 using organs from deceased brain-dead donors aged 70 or older were reviewed. From November 2020 on, HOPE was performed routinely in this donor category. The frequency and severity of AKI (KDIGO criteria) within 48 hours of graft reperfusion and the model of early allograft function (MEAF) were compared between HOPE-LTs (n = 30) and control LTs (n = 71).

RESULTS

AKI developed in 23/30 (77%) HOPE-LTs and in 40/71 (56%) control LTs (p = n.s.), with no difference in severity and timing between groups. Renal replacement therapy was required in 3/30 (10%) HOPE-LTs and 6/71 (8%) control LTs. In addition, transaminase leak during the first week (marker of IRI) and MEAF were similar between groups. These findings persisted after propensity matching. Histology showed more hepatocyte vacuolization and higher Suzuki score in HOPE-LTs. Although this analysis could have been underpowered, no trends supporting the benefit of HOPE on liver and renal injury after LT were ever identified.

CONCLUSIONS

In conclusion, HOPE in this group of older donors does not seem to improve either graft IRI, or the incidence of early AKI after LT.

Machine perfusion of the liver and bioengineering

With the increasing number of accepted candidates on waiting lists worldwide, there is an urgent need to expand the number and the quality of donor livers. Dynamic preservation approaches have demonstrated various benefits, including improving liver function and graft survival, and reducing liver injury and post-transplant complications. Consequently, organ perfusion techniques are being used in clinical practice in many countries. Despite this success, a proportion of livers do not meet current viability tests required for transplantation, even with the use of modern perfusion techniques. Therefore, devices are needed to further optimise machine liver perfusion - one promising option is to prolong machine liver perfusion for several days, with ex situ treatment of perfused livers. For example, stem cells, senolytics, or molecules targeting mitochondria or downstream signalling can be administered during long-term liver perfusion to modulate repair mechanisms and regeneration. Besides, today's perfusion equipment is also designed to enable the use of various liver bioengineering techniques, to develop scaffolds or for their re-cellularisation. Cells or entire livers can also undergo gene modulation to modify animal livers for xenotransplantation, to directly treat injured organs or to repopulate such scaffolds with "repaired" autologous cells. This review first discusses current strategies to improve the quality of donor livers, and secondly reports on bioengineering techniques to design optimised organs during machine perfusion. Current practice, as well as the benefits and challenges associated with these different perfusion strategies are discussed.

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.