EASL position paper on preclinical models of steatotic liver disease.

Steatotic liver disease (SLD) comprises a heterogeneous group of liver diseases defined by pathological hepatic lipid accumulation with varying degrees of steatohepatitis and progressive fibrosis, which may culminate in cirrhosis and/or hepatocellular carcinoma. SLD encompasses metabolic dysfunction-associated steatotic liver disease (MASLD), formerly called non-alcoholic fatty liver disease (NAFLD); MetALD, describing patients with MASLD consuming moderately high amounts of alcohol; and alcohol-associated/related liver disease (ALD). In addition, SLD encompasses less common aetiologies, including drug-induced and monogenic causes, as well as cryptogenic disease, which lacks metabolic risk factors or an identifiable cause. As the leading cause of chronic liver disease worldwide, MASLD, including metabolic dysfunction-associated steatohepatitis (MASH), is a complex multisystem disorder associated with extrahepatic organ dysfunction. Consequently, MASLD has become a major focus of multidisciplinary research, driving innovation across hepatology, immunology, cardiometabolism, addiction medicine, nutrition, prevention, and beyond. Over the past two decades, a broad array of in vivo, in vitro, and ex vivo experimental models have been developed to recapitulate diverse aspects of SLD pathophysiology, genetics, inflammation, treatment response, and multi-organ crosstalk, substantially advancing mechanistic understanding and therapeutic development. However, the rapid expansion and heterogeneity of available models have also highlighted the need for improved categorisation, standardisation, and harmonisation in line with evolving disease definitions and clinical concepts. In this EASL position paper, we critically review and classify currently available experimental SLD models and propose key criteria required for their appropriate use across distinct SLD subtypes. These criteria encompass systemic and hepatic metabolism, cardiometabolic comorbidities, histopathology, immunopathology, and molecular features relevant to disease stage and aetiology. This position paper aims to guide informed model selection, promote consistent nomenclature, and enhance rigour and translational relevance in preclinical and experimental SLD research.