The Effect of Antioxidant Added to Preservation Solution on the Protection of Kidneys before Transplantation

Modification of Preservative Fluids with Antioxidants in Terms of Their Efficacy in Liver Protection before Transplantation

Transplantation is currently the only effective treatment for patients with end-stage liver failure. In recent years, many advanced studies have been conducted to improve the efficiency of organ preservation techniques. Modifying the composition of the preservation fluids currently used may improve graft function and increase the likelihood of transplantation success. The modified fluid is expected to extend the period of safe liver storage in the peri-transplantation period and to increase the pool of organs for transplantation with livers from marginal donors. This paper provides a literature review of the effects of antioxidants on the efficacy of liver preservation fluids. Medline (PubMed), Scopus, and Cochrane Library databases were searched using a combination of MeSH terms: "liver preservation", "transplantation", "preservation solution", "antioxidant", "cold storage", "mechanical perfusion", "oxidative stress", "ischemia-reperfusion injury". Studies published up to December 2023 were included in the analysis, with a focus on publications from the last 30 years. A total of 45 studies met the inclusion criteria. The chemical compounds analyzed showed mostly bioprotective effects on hepatocytes, including but not limited to multifactorial antioxidant and free radical protective effects. It should be noted that most of the information cited is from reports of studies conducted in animal models, most of them in rodents.

Pushing the boundaries of innovation: the potential of ex vivo organ perfusion from an interdisciplinary point of view

Ex vivo machine perfusion (EVMP) is an emerging technique for preserving explanted solid organs with primary application in allogeneic organ transplantation. EVMP has been established as an alternative to the standard of care static-cold preservation, allowing for prolonged preservation and real-time monitoring of organ quality while reducing/preventing ischemia-reperfusion injury. Moreover, it has paved the way to involve expanded criteria donors, e.g., after circulatory death, thus expanding the donor organ pool. Ongoing improvements in EVMP protocols, especially expanding the duration of preservation, paved the way for its broader application, in particular for reconditioning and modification of diseased organs and tumor and infection therapies and regenerative approaches. Moreover, implementing EVMP for in vivo-like preclinical studies improving disease modeling raises significant interest, while providing an ideal interface for bioengineering and genetic manipulation. These approaches can be applied not only in an allogeneic and xenogeneic transplant setting but also in an autologous setting, where patients can be on temporary organ support while the diseased organs are treated ex vivo, followed by reimplantation of the cured organ. This review provides a comprehensive overview of the differences and similarities in abdominal (kidney and liver) and thoracic (lung and heart) EVMP, focusing on the organ-specific components and preservation techniques, specifically on the composition of perfusion solutions and their supplements and perfusion temperatures and flow conditions. Novel treatment opportunities beyond organ transplantation and limitations of abdominal and thoracic EVMP are delineated to identify complementary interdisciplinary approaches for the application and development of this technique.

Evaluation of Oxidative Stress and Metabolic Profile in a Preclinical Kidney Transplantation Model According to Different Preservation Modalities

This study addresses a joint nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy approach to provide a platform for dynamic assessment of kidney viability and metabolism. On porcine kidney models, ROS production, oxidative damage kinetics, and metabolic changes occurring both during the period between organ retrieval and implantation and after kidney graft were examined. The 1H-NMR metabolic profile—valine, alanine, acetate, trimetylamine-N-oxide, glutathione, lactate, and the EPR oxidative stress—resulting from ischemia/reperfusion injury after preservation (8 h) by static cold storage (SCS) and ex vivo machine perfusion (HMP) methods were monitored. The functional recovery after transplantation (14 days) was evaluated by serum creatinine (SCr), oxidative stress (ROS), and damage (thiobarbituric-acid-reactive substances and protein carbonyl enzymatic) assessments. At 8 h of preservation storage, a significantly (p < 0.0001) higher ROS production was measured in the SCS vs. HMP group. Significantly higher concentration data (p < 0.05−0.0001) in HMP vs. SCS for all the monitored metabolites were found as well. The HMP group showed a better function recovery. The comparison of the areas under the SCr curves (AUC) returned a significantly smaller (−12.5 %) AUC in the HMP vs. SCS. EPR-ROS concentration (μmol·g−1) from bioptic kidney tissue samples were significantly lower in HMP vs. SCS. The same result was found for the NMR monitored metabolites: lactate: −59.76%, alanine: −43.17%; valine: −58.56%; and TMAO: −77.96%. No changes were observed in either group under light microscopy. In conclusion, a better and more rapid normalization of oxidative stress and functional recovery after transplantation were observed by HMP utilization.

Novel, Innovative Models to Study Ischemia/Reperfusion-Related Redox Damage in Organ Transplantation

The implementation of ex vivo organ machine perfusion (MP) into clinical routine undoubtedly helped to increase the donor pool. It enables not just organ assessment, but potentially regeneration and treatment of marginal organs in the future. During organ procurement, redox-stress triggered ischemia-reperfusion injury (IRI) is inevitable, which in addition to pre-existing damage negatively affects such organs. Ex vivo MP enables to study IRI-associated tissue damage and its underlying mechanisms in a near to physiological setting. However, research using whole organs is limited and associated with high costs. Here, in vitro models well suited for early stage research or for studying particular disease mechanisms come into play. While cell lines convince with simplicity, they do not exert all organ-specific functions. Tissue slice cultures retain the three-dimensional anatomical architecture and cells remain within their naïve tissue-matrix configuration. Organoids may provide an even closer modelling of physiologic organ function and spatial orientation. In this review, we discuss the role of oxidative stress during ex vivo MP and the suitability of currently available in vitro models to further study the underlying mechanisms and to pretest potential treatment strategies.

Luminal administration of biliverdin ameliorates ischemia-reperfusion injury following intestinal transplant in rats

BACKGROUND

Intestinal grafts are susceptible to ischemia-reperfusion injury, resulting in the loss of mucosal barrier function and graft failure. Biliverdin is known to exert a variety of cytoprotective functions against oxidative tissue injury. Because the mucosal layer is the primary site of ischemia-reperfusion injury, mucosa-targeting strategies by luminal delivery of reagents might be beneficial. We tested whether intraluminal administration of biliverdin as an adjuvant to standard preservation solutions protected against ischemia-reperfusion injury.

METHODS

Orthotopic syngeneic intestinal transplants were performed on Lewis rats after 6 hours of cold preservation. Saline containing biliverdin (10 μM) or without biliverdin was introduced into the lumen of the intestinal grafts immediately before cold preservation.

RESULTS

Damage to the intestinal mucosa caused by ischemia-reperfusion injury resulted in severe morphological changes, including blunting of the villi and erosion, and led to significant loss of gut barrier function 3 hours after reperfusion. These changes to the mucosa were notably ameliorated by intraluminal administration of biliverdin. Biliverdin also effectively inhibited upregulation of messenger RNAs for interleukin-6, inducible nitric oxide synthase, and C-C motif chemokine 2. Additionally, biliverdin treatment prevented the loss of expression of claudin-1, a transmembrane, tight-junction barrier protein. The 14-day survival of recipients of biliverdin-treated grafts was significantly improved as compared with the recipients of saline-treated control grafts (83.3% vs 38.9%, P = .030).

CONCLUSION

This study demonstrated that luminally delivered biliverdin provides beneficial effects during the transplant of rat small intestinal grafts and could be an attractive therapeutic option in organ transplantation.

Liver Graft Hypothermic Static and Oxygenated Perfusion (HOPE) Strategies: A Mitochondrial Crossroads

Marginal liver grafts, such as steatotic livers and those from cardiac death donors, are highly vulnerable to ischemia–reperfusion injury that occurs in the complex route of the graft from “harvest to revascularization”. Recently, several preservation methods have been developed to preserve liver grafts based on hypothermic static preservation and hypothermic oxygenated perfusion (HOPE) strategies, either combined or alone. However, their effects on mitochondrial functions and their relevance have not yet been fully investigated, especially if different preservation solutions/effluents are used. Ischemic liver graft damage is caused by oxygen deprivation conditions during cold storage that provoke alterations in mitochondrial integrity and function and energy metabolism breakdown. This review deals with the relevance of mitochondrial machinery in cold static preservation and how the mitochondrial respiration function through the accumulation of succinate at the end of cold ischemia is modulated by different preservation solutions such as IGL-2, HTK, and UW (gold-standard reference). IGL-2 increases mitochondrial integrity and function (ALDH2) when compared to UW and HTK. This mitochondrial protection by IGL-2 also extends to protective HOPE strategies when used as an effluent instead of Belzer MP. The transient oxygenation in HOPE sustains the mitochondrial machinery at basal levels and prevents, in part, the accumulation of energy metabolites such as succinate in contrast to those that occur in cold static preservation conditions. Additionally, several additives for combating oxygen deprivation and graft energy metabolism breakdown during hypothermic static preservation such as oxygen carriers, ozone, AMPK inducers, and mitochondrial UCP2 inhibitors, and whether they are or not to be combined with HOPE, are presented and discussed. Finally, we affirm that IGL-2 solution is suitable for protecting graft mitochondrial machinery and simplifying the complex logistics in clinical transplantation where traditional (static preservation) and innovative (HOPE) strategies may be combined. New mitochondrial markers are presented and discussed. The final goal is to take advantage of marginal livers to increase the pool of suitable organs and thereby shorten patient waiting lists at transplantation clinics.