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Acute liver failure (ALF) is defined by the American Association for the Study of Liver Diseases as rapid development of acute liver injury without any prior signs of damage and is characterized by severe impairment of the synthetic, metabolic, and detoxifying functions of the liver1. ALF differs from chronic liver failure where the failure occurs as a result of liver injury caused over a long period of time and from acute chronic liver failure (ACLF), where abrupt liver damage takes place as a result of chronic liver diseases2,3,4. The only available cure for ALF is orthotopic liver transplant (OLT), or death may occur. Due to the shortage of liver donors, the rate of mortality in patients suffering from ALF is very high.
To study the potential of alternative therapeutic approaches and to better understand the pathophysiology of ALF, animal models that can reflect the ALF occurring in human beings are needed. Many of the already available ALF animal models have several shortcomings. Acetaminophen (APAP) effects are difficult to reproduce but have the closest similarities in terms of temporal, clinical, biochemical, and pathological parameters. APAP- induced animal models frequently encounter problems due to the presence of methemoglobinemia caused by the oxidation of hemoglobin by APAP and its intermediates5,6,7. Another problem is the lack of reproducibility reflected by unpredictable dose responses and the time of death. The ALF animal models produced using carbon tetra chloride (CCl4) have poor reproducibility8,9,10,11. Concavalin A (Con A) and lipoplysaccharide (LPS)-induced ALF animal models do not reflect the clinical pattern of the human disease, though they have advantages in the study of cellular mechanisms involved in autoimmune liver diseases and in the study of sepsis respectively12,13,14,15. Similarly, thioacetamide (TAA) also requires biotransformation to an active metabolite thioacetamide sulfoxide and shows species variation16,17,18,19. D-galactosamine (D-Gal) produces some biochemical, metabolic, and physiological changes similar to ALF but is not able to reflect the whole ALF pathological condition20,21,22,23. There have been very few attempts to combine two or more of these methods to develop an ALF model that is able to reflect the ALF syndrome in a better manner13. Therefore, further studies are required to develop a model that can reflect the disease parameters, has better reproducibility, and provides enough time to study the effects of a therapeutic intervention.
In the current study, an alternative ALF model in rats has been created by combining the effects of partial hepatectomy (PHx) and lower doses of a hepatotoxic reagent. APAP has a well-established role in causing liver injury5,24,25. It is a widely used analgesic and is toxic to the liver at supratherapeutic doses by forming toxic metabolites. APAP is the cause of many deaths in developed countries. Physical injury caused by partial hepatectomy initiates activation of various processes involved in inflammation as well as liver regeneration. Injection of the hepatotoxic agent APAP causes a hostile environment in the liver, preventing the proliferation of hepatocytes. This reduces the stress period on the animal, which when combined with smaller doses of hepatotoxin, leads to better reproducibility of the procedure. Therefore, using this model, a combinatory effect of two types of liver injuries has been studied. To characterize the developed ALF animal model, physiological and biochemical parameters have been studied. Successful reversibility of ALF was confirmed by transplantation of syngeneic healthy rat hepatocytes.