Transcriptomic trajectory of hepatocyte ballooning reveals a lipotoxic point of no return and initiates oncogenic regulatory rewiring in MASLD.

Background: Hepatocyte ballooning is a defining histological marker of progressive steatohepatitis, but its molecular basis remains poorly defined. Objective: To identify a molecular signature and mechanistic trajectory underlying hepatocyte ballooning across the MASLD-to-hepatocellular carcinoma spectrum. Methods: Liver microarray data from 43 patients stratified by histological ballooning score were combined with machine-learning feature selection and publicly available single-nucleus RNA sequencing data (87,244 hepatocyte nuclei) to derive a gene signature, tested in an independent bulk transcriptomic cohort (GSE130970, n = 75); pseudotime, transcription-factor regulon and cell-cell communication analyses characterised the underlying biology, with in vitro validation in palmitic acid-treated Huh7 cells and prognostic testing in 510 TCGA-LIHC patients. Results: An eight-gene signature ( Conclusions: Hepatocyte ballooning is a transcriptionally active, stepwise process with a lipotoxic point of no return and prognostic relevance extending to hepatocellular carcinoma.