Barry J. Fuller

Liver ischemia/reperfusion injury: Processes in inflammatory networks—A review

Liver ischemia/reperfusion (IR) injury is typified by an inflammatory response. Understanding the cellular and molecular events underpinning this inflammation is fundamental to developing therapeutic strategies. Great strides have been made in this respect recently. Liver IR involves a complex web of interactions between the various cellular and humoral contributors to the inflammatory response. Kupffer cells, CD4+ lymphocytes, neutrophils, and hepatocytes are central cellular players. Various cytokines, chemokines, and complement proteins form the communication system between the cellular components. The contribution of the danger‐associated molecular patterns and pattern recognition receptors to the pathophysiology of liver IR injury are slowly being elucidated. Our knowledge on the role of mitochondria in generating reactive oxygen and nitrogen species, in contributing to ionic disturbances, and in initiating the mitochondrial permeability transition with subsequent cellular death in liver IR injury is continuously being expanded. Here, we discuss recent findings pertaining to the aforementioned factors of liver IR, and we highlight areas with gaps in our knowledge, necessitating further research. Liver Transpl 16:1016–1032, 2010.

Decellularized human liver as a natural 3D-scaffold for liver bioengineering and transplantation.

Liver synthetic and metabolic function can only be optimised by the growth of cells within a supportive liver matrix. This can be achieved by the utilisation of decellularised human liver tissue. Here we demonstrate complete decellularization of whole human liver and lobes to form an extracellular matrix scaffold with a preserved architecture. Decellularized human liver cubic scaffolds were repopulated for up to 21 days using human cell lines hepatic stellate cells (LX2), hepatocellular carcinoma (Sk-Hep-1) and hepatoblastoma (HepG2), with excellent viability, motility and proliferation and remodelling of the extracellular matrix. Biocompatibility was demonstrated by either omental or subcutaneous xenotransplantation of liver scaffold cubes (5 × 5 × 5 mm) into immune competent mice resulting in absent foreign body responses. We demonstrate decellularization of human liver and repopulation with derived human liver cells. This is a key advance in bioartificial liver development.

Organ Preservation: Current Concepts and New Strategies for the Next Decade.

Organ transplantation has developed over the past 50 years to reach the sophisticated and integrated clinical service of today through several advances in science. One of the most important of these has been the ability to apply organ preservation protocols to deliver donor organs of high quality, via a network of organ exchange to match the most suitable recipient patient to the best available organ, capable of rapid resumption of life-sustaining function in the recipient patient. This has only been possible by amassing a good understanding of the potential effects of hypoxic injury on donated organs, and how to prevent these by applying organ preservation. This review sets out the history of organ preservation, how applications of hypothermia have become central to the process, and what the current status is for the range of solid organs commonly transplanted. The science of organ preservation is constantly being updated with new knowledge and ideas, and the review also discusses what innovations are coming close to clinical reality to meet the growing demands for high quality organs in transplantation over the next few years.

Shear‐stress preconditioning and tissue‐engineering‐based paradigms for generating arterial substitutes

In situ tissue engineering using shear‐stress preconditioning and adhesive biomolecules is a new approach to autologous tissue engineering. In the present study, novel tissue‐engineering grafts (TEGs) were preconditioned within an in vitro pulsatile flow circuit, with and without the addition of fibronectin (FN), to establish whether low‐shear‐stress conditions promoted endothelial cell (EC) retention and differentiation. TEGs (n=24) were generated by the contraction and compaction of collagen(I) by porcine aortic smooth‐muscle cells (SMCs) on to a compliant polyester graft scaffold. ECs were radiolabelled with [111In]indium tropolonate and seeded on to the luminal surface of the TEGs. Following organ culture in a bioreactor (7 days), TEGs were split into four groups (n=six TEGs per group): Group A acted as controls with TEGs unmodified and seeded with radiolabelled ECs; Group B underwent luminal pre‐coating with FN (75 μg/ml) prior to EC seeding; Group C underwent preconditioning within a pulsatile flow circuit at 10–20 μN (1–2 dyn)/cm2 for 7 days prior to EC seeding, and Group D TEGs were preconditioned for 7 days at 1–2 dyn/cm2, followed by luminal pre‐coating with FN prior to EC seeding. The resistance to physiological shear stress of the seeded ECs was assessed using a γ‐radiation counter within a physiological flow circuit producing an arterial waveform with a mean shear stress of 93.2 μN (9.32 dyn)/cm2. Environmental scanning electron microscopy (ESEM) was used to determine the distribution and degree of differentiation of the attached Ecs, and tissue‐type‐plasminogen‐activator (tPA) assays provided a measure of function and viability. EC resistance to shear stress at 93.2 μN/cm2 was significantly enhanced by a period of preconditioning (Group C) at 10–20 μN/cm2, surface modification with FN (Group B), or both (Group D) when compared with control grafts (Group A). However, TEGs coated with FN whether preconditioned (Group D) or not (Group B) demonstrated the best results for EC retention. ESEM demonstrated near‐confluent differentiated flattened ECs in both these cases. EC function was demonstrated by a steady increase in tPA production. Low‐shear‐stress preconditioning of TEGs enhances EC retention in vitro with an additional advantage demonstrated by pre‐treatment with FN prior to endothelialization. These findings may be exploited in the development of tissue‐engineered constructs to maintain a confluent endothelial lining.

EVIDENCE OF FREE-RADICAL-INDUCED DAMAGE IN RABBIT KIDNEYS AFTER SIMPLE HYPOTHERMIC PRESERVATION AND AUTOTRANSPLANTATION

Rabbit kidneys were stored for 24 or 48 hr at 0

REDUCED SUSCEPTIBILITY TO LIPID-PEROXIDATION IN COLD ISCHEMIC RABBIT KIDNEYS AFTER ADDITION OF DESFERRIOXAMINE, MANNITOL, OR URIC-ACID TO THE FLUSH SOLUTION

C after single-passage vascular flush with 30 ml of cold hypertonic citrate solution or 0.9% isotonic sodium chloride solution. They were then subjected to in vitro biochemical assay for evidence of free-radical damage immediately after storage or after they had been orthotopically autotransplanted and reperfused with blood in vivo for 60 min. Kidney homogenates were incubated at 37

Intracellular iron redistribution: An important determinant of reperfusion damage to rabbit kidneys

C and assayed for fluorescent conjugated Schiff bases as indicators of lipid peroxidation, as well as for superoxide dismutase activity and reduced and oxidized glutathione. In kidneys flushed with hypertonic citrate, no evidence of peroxidation could be detected immediately after storage for 24 or 48 hr. However, after in vivo reperfusion significantly more peroxidation (P<0.01) was evident. Storage in isotonic saline solution produced still higher levels of peroxidation damage whether reperfused or not (P<0.001). Schiff base formation was inversely proportional to the reduced and oxidized glutathione levels measured. No changes in superoxide dismutase levels could be detected. It is concluded that lipid peroxidation is important during cold ischemia but most damage occurs during the 60-min of reperfusion in vivo immediately after transplantation.

An assessment of covalent grafting of RGD peptides to the surface of a compliant poly(carbonate-urea)urethane vascular conduit versus conventional biological coatings: its role in enhancing cellular retention.

Ischemia reperfusion injury is a major obstacle in liver resection and liver transplantation surgery. Understanding the mechanisms of liver ischemia reperfusion injury (IRI) and developing strategies to counteract this injury will therefore reduce acute complications in hepatic resection and transplantation, as well as expanding the potential pool of usable donor grafts. The initial liver injury is initiated by reactive oxygen species which cause direct cellular injury and also activate a cascade of molecular mediators leading to microvascular changes, increased apoptosis and acute inflammatory changes with increased hepatocyte necrosis. Some adaptive pathways are activated during reperfusion that reduce the reperfusion injury. IRI involves a complex interplay between neutrophils, natural killer T-cells cells, CD4+ T cell subtypes, cytokines, nitric oxide synthases, haem oxygenase-1, survival kinases such as the signal transducer and activator of transcription, Phosphatidylinositol 3-kinases/Akt and nuclear factor κβ pathways. Transgenic animals, particularly genetic knockout models, have become a powerful tool at elucidating mechanisms of liver ischaemia reperfusion injury and are complementary to pharmacological studies. Targeted disruption of the protein at the genetic level is more specific and maintained than pharmacological inhibitors or stimulants of the same protein. This article reviews the evidence from knockout models of liver IRI about the cellular and molecular mechanisms underlying liver IRI.