Ischemic Preconditioning Directly or Remotely Applied on the Liver to Reduce Ischemia-Reperfusion Injury in Resections and Transplantation

Ischemia-reperfusion (I/R) injury is an important cause of liver damage occurring during surgical procedures. In liver resection, I/R causes post-operative transaminasemia and liver function failure. In liver transplantation, I/R causes graft dysfunction, ranging from biochemical abnormalities to primary non-function of the transplanted organ. Ischemic preconditioning is a surgical strategy to reduce the severity of I/R and improve post-operative outcomes by prior exposure to a brief period of vascular occlusion directly to the target organ or remotely to a distant vascular bed. This chapter aims to discuss the different ischemic preconditioning strategies in both liver resection surgery and liver transplantation. In addition, we will describe the differences of such surgical strategies in both steatotic and non-steatotic livers in both preclinical experiments and clinical practice. Such information may be useful to guide the design of the effective ischemic preconditioning methods in the surgery of hepatic resections and liver transplantation

Hepatic Regeneration Under Warm or Cold Ischemia Conditions: Controversies and New Approaches

Ischemia-reperfusion (I/R) associated with hepatic resection and living related liver transplantation is an unsolved problem in clinical practice. Indeed, I/R induces damage and regenerative failure in clinical liver surgery. Signaling pathways regarding the pathophysiology of liver I/R and regeneration making clear distinction between situations of cold and warm ischemia, as well as liver regeneration with or without vascular occlusion, will be addressed. The different experimental models used to date to improve the postoperative outcomes in clinical liver surgery will be also described. Furthermore, the most updated therapeutic strategies, as well as the clinical and scientific controversies in the field, will be discussed. Such information may be useful to guide the design of better experimental models as well as the effective therapeutic strategies in liver surgery that can succeed in achieving its clinical application

Endoplasmic Reticulum and Mitochondria Contacts Correlate with the Presence and Severity of NASH in Humans.

The interaction between the mitochondria and the endoplasmic reticulum (ER) is essential for hepatocyte function. An increase in ER-mitochondria contacts (ERMCs) is associated with various metabolic diseases. Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and type 2 diabetes, and its progressive form non-alcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma. However, the role of ERMCs in the progression of NAFL to NASH is still unclear. We assessed whether ERMCs could correlate with NAFLD severity. We used a proximity ligation assay to measure the abundance of ERMCs in liver biopsies from patients with biopsy-proven NAFLD (n = 48) and correlated the results with histological and metabolic syndrome (MetS) features. NAFLD patients were included according to inclusion and exclusion criteria, and then assigned to NAFL (n = 9) and NASH (n = 39) groups. ERMCs density could discriminate NASH from NAFL (sensitivity 61.5%, specificity 100%). ERMCs abundance correlated with hepatocellular ballooning. Moreover, the density of ERMCs increased with an increase in the number of MetS features. In conclusion, ERMCs increased from NAFL to NASH, in parallel with the number of MetS features, supporting a role for this interaction in the pathophysiology of NASH

Mechanobiology of portal hypertension.

The interplay between mechanical stimuli and cellular mechanobiology orchestrates the physiology of tissues and organs in a dynamic balance characterized by constant remodelling and adaptative processes. Environmental mechanical properties can be interpreted as a complex set of information and instructions that cells read continuously, and to which they respond. In cirrhosis, chronic inflammation and injury drive liver cells dysfunction, leading to excessive extracellular matrix deposition, sinusoidal pseudocapillarization, vascular occlusion and parenchymal extinction. These pathological events result in marked remodelling of the liver microarchitecture, which is cause and result of abnormal environmental mechanical forces, triggering and sustaining the long-standing and progressive process of liver fibrosis. Multiple mechanical forces such as strain, shear stress, and hydrostatic pressure can converge at different stages of the disease until reaching a point of no return where the fibrosis is considered non-reversible. Thereafter, reciprocal communication between cells and their niches becomes the driving force for disease progression. Accumulating evidence supports the idea that, rather than being a passive consequence of fibrosis and portal hypertension (PH), mechanical force-mediated pathways could themselves represent strategic targets for novel therapeutic approaches. In this manuscript, we aim to provide a comprehensive review of the mechanobiology of PH, by furnishing an introduction on the most important mechanisms, integrating these concepts into a discussion on the pathogenesis of PH, and exploring potential therapeutic strategies

Online oxygen monitoring using integrated inkjet-printed sensors in a liver-on-a-chip system

The demand for real-time monitoring of cell functions and cell conditions has dramatically increased with the emergence of organ-on-a-chip (OOC) systems. However, the incorporation of co-cultures and microfluidic channels in OOC systems increases their biological complexity and therefore makes the analysis and monitoring of analytical parameters inside the device more difficult. In this work, we present an approach to integrate multiple sensors in an extremely thin, porous and delicate membrane inside a liver-on-a-chip device. Specifically, three electrochemical dissolved oxygen (DO) sensors were inkjet-printed along the microfluidic channel allowing local online monitoring of oxygen concentrations. This approach demonstrates the existence of an oxygen gradient up to 17.5% for rat hepatocytes and 32.5% for human hepatocytes along the bottom channel. Such gradients are considered crucial for the appearance of zonation of the liver. Inkjet printing (IJP) was the selected technology as it allows drop on demand material deposition compatible with delicate substrates, as used in this study, which cannot withstand temperatures higher than 130 °C. For the deposition of uniform gold and silver conductive inks on the porous membrane, a primer layer using SU-8 dielectric material was used to seal the porosity of the membrane at defined areas, with the aim of building a uniform sensor device. As a proof-of-concept, experiments with cell cultures of primary human and rat hepatocytes were performed, and oxygen consumption rate was stimulated with carbonyl-cyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP), accelerating the basal respiration of 0.23 ± 0.07 nmol s-1/106 cells up to 5.95 ± 0.67 nmol s-1/106 cells s for rat cells and the basal respiration of 0.17 ± 0.10 nmol s-1/106 cells by up to 10.62 ± 1.15 nmol s-1/106 cells for human cells, with higher oxygen consumption of the cells seeded at the outflow zone. These results demonstrate that the approach of printing sensors inside an OOC has tremendous potential because IJP is a feasible technique for the integration of different sensors for evaluating metabolic activity of cells, and overcomes one of the major challenges still remaining on how to tap the full potential of OOC systems.Peer ReviewedPostprint (author's final draft

New Perspectives on the Use of Sub-Optimal Donor Livers

Liver transplantation is the therapy of choice for patients with end-stage liver disease. However, a shortage of donor organs remains a major obstacle to the widespread application of liver transplantation. To overcome this problem, transplant centers have developed strategies to expand the organ donor pool, including the routine use of sub-optimal donor livers. However, these have an increased risk of initial poor function or primary non-function that may cause greater risk of morbidity in the recipient. This chapter aims to describe the pathophysiological changes that may occur in sub-optimal donor livers, focusing on viral infections, since, after transplantation, infection of the graft is almost universal and can lead to chronic hepatitis, cirrhosis, and graft failure. The different experimental models as well as the clinical outcomes of the transplantation of sub-optimal donor livers with viral infections will be discussed. Such information may be useful to guide the design of better experimental models than those described to date as well as the effective use of sub-optimal livers with successful clinical application

Animal models for liver disease – A practical approach for translational research

Animal models are crucial for improving our understanding of human pathogenesis, enabling researchers to identify therapeutic targets and test novel drugs. In the current review, we provide a comprehensive summary of the most widely used experimental models of chronic liver disease, starting from early stages of fatty liver disease (non-alcoholic and alcoholic) to steatohepatitis, advanced cirrhosis and end-stage primary liver cancer. We focus on aspects such as reproducibility and practicality, discussing the advantages and weaknesses of available models for researchers who are planning to perform animal studies in the near future. Additionally, we summarise current and prospective models based on human tissue bioengineering

Review: Vascular effects of PPARs in the context of NASH.

BACKGROUND Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to regulate glucose and fatty acid metabolism, inflammation, endothelial function and fibrosis. PPAR isoforms have been extensively studied in metabolic diseases, including type 2 diabetes and cardiovascular diseases. Recent data extend the key role of PPARs to liver diseases coursing with vascular dysfunction, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). AIM This review summarises and discusses the pathobiological role of PPARs in cardiovascular diseases with a special focus on their impact and therapeutic potential in NAFLD and NASH. RESULTS AND CONCLUSIONS PPARs may be attractive for the treatment of NASH due to their liver-specific effects but also because of their efficacy in improving cardiovascular outcomes, which may later impact liver disease. Assessment of cardiovascular disease in the context of NASH trials is, therefore, of the utmost importance, both from a safety and efficacy perspective