Single-Cell Data Analysis Reveals Critical Hepatic Cells Subpopulations in the Progression of Non-alcoholic Fatty Liver Disease to Non-Alcoholic Steatohepatitis.

Aims: The aim of this study was to reveal the hepatic cell landscape and function in the progression of NAFLD to NASH.

Background: Non-alcoholic steatohepatitis (NASH) is the progressive form and turning point of nonalcoholic fatty liver disease (NAFLD), which severely causes irreversible cirrhosis as well as hepatocellular carcinoma. The mechanism underlying the progression of NAFLD to NASH has not been revealed. Unraveling the mechanism of action of NAFLD-NASH is an important goal in improving the survival of patients with liver disease.

Objective: The aim of this study is to discover heterogeneous hepatic cells during the progression of NAFLD to NASH.

Methods: Single-nucleus RNA-seq (snRNA-seq) data containing NASH in NAFLD samples were obtained from the Gene Expression Omnibus (GEO) database. Cell types in liver tissues from NASH and NAFLD were identified after dimensionality reduction analysis, cluster analysis, and cell annotation. The cell pathways in which differences existed were identified by analyzing metabolic pathways in Hepatic cells. We also identified cell subpopulations in Hepatic cells. The developmental trajectories of Hepatic cells were characterized by pseudotime trajectory analysis. Single-cell regulatory network inference and clustering analysis identified key transcription factors and gene regulatory networks in Hepatic cells. Moreover, cell communication analysis determined the potential interactions between Hepatic cells and immune cells, and heapatic stellate cells.

Results: Seven cell types were identified in NAFLD and NASH. The proportion of Hepatic cells was lower in NASH and showed greater energy metabolism and glucose metabolism activity. Hepatic cells exhibited heterogeneity, showing two cell subpopulations, Hepatic cells 1 and Hepatic cells 2. Dysregulation of lipid metabolism in Hepatic Cell 2 resulted in lipid accumulation in the liver, which might be involved in the progression of NAFLD. Four key transcription factors, BHLHE40, NFEL2L, RUNX1, and INF4A, were primarily found in Hepatic cells 2. The transcription factors within the hepatic cells 2 subpopulation mainly regulated genes related to lipid metabolism, energy metabolism, and inflammatory response. The cell communication analysis showed that hepatocyte interactions with immune cells were associated with inflammatory responses, while interactions with hepatic astrocytes were associated with liver injury and hepatocyte fibrosis.

Conclusion: The hepatic cells 2 might promote the progression of NAFLD to NASH by regulating metabolic activity, which might contribute to liver injury through inflammation.