Generation and characterization of a chronic in vitro model to study the early stage of metabolic dysfunction-associated steatotic liver disease (MASLD).

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic and progressive liver disease with an increasing global burden that starts with an early stage of simple steatosis (MASL) which frequently progresses to liver cirrhosis and hepatocellular carcinoma (HCC). Despite its widespread occurrence, the MASL or steatotic stage, characterized by excessive fat accumulation in the liver and considered reversible and benign, has not been extensively studied. To study MASL effectively, it is imperative to have a clinically relevant model system that focuses solely on steatosis, in a progressive and time-dependent manner, recapitulating molecular changes associated with human disease. We established a chronic cellular model of MASL using a primary immortalized human hepatocyte cell line treated with a low dose mixture of fatty acids. This model mimics the pattern of chronic disease progression, shows minimal lipotoxicity, exhibits progressive lipid accumulation (from early to moderate steatosis), and demonstrates macrosteatosis, a hallmark of MASL. To determine whether this model recapitulates both morphological and molecular aspects of steatosis, we measured the expression of key genes and pathways found to be dysregulated in a recently available early MASL patient dataset as well as a non-human primate model of MASL. In support of the relevance of our model, we observed increased fatty acid uptake, lipogenesis, mitochondrial activity, metabolic rewiring, and autophagic alterations that significantly overlap with the pathological features of human and non-human primate MASL. In conclusion, we generate a relevant cellular model of steatosis that can serve as a robust platform for screening of existing chemical libraries to identify potent inhibitors of MASL as well as discovering novel therapeutic targets by mechanistically studying altered molecular signatures associating early stages of MASLD.