Clear Cell Foci as Precursors of Hepatocyte Nuclear Factor 1-alpha–inactivated Hepatocellular Adenoma in a Metabolic Syndrome Mouse Model

Abstract

Clear cell foci (CCF) are frequently observed in metabolic dysfunction–associated steatohepatitis (MASH) and are considered potential precursor lesions of hepatocyte nuclear factor 1α–inactivated hepatocellular adenoma (H-HCA). To clarify their chronological development, we examined 55 male TSOD mice at 24, 32, 40, and 48 weeks of age using histology and immunohistochemistry for glutamine synthetase (GS), liver fatty acid–binding protein (L-FABP), β-Klotho, and fibroblast growth factor 21 (FGF21). CCF first appeared at 24 weeks and increased markedly with age (from 11% to 81%). All CCF were positive for β-Klotho, and a subset showed FGF21 expression, indicating that CCF represent a hepatocellular state associated with metabolic dysregulation. H-HCA, characterized by GS negativity and reduced L-FABP expression, emerged at 40 weeks and reached an incidence of 29% at 48 weeks. Notably, multiple H-HCA were partially or completely surrounded by β-Klotho–positive CCF, suggesting a morphologic continuum from CCF to H-HCA. Raman spectroscopic analysis demonstrated that CCF exhibit prominent autofluorescence and possess spectral characteristics distinct from both background hepatocytes and tumor tissue, supporting the concept that CCF represent a unique hepatocellular state. These findings indicate that metabolic abnormalities in TSOD mice promote the sequential formation of CCF and H-HCA, establishing this model as a useful platform for studying adenoma development in metabolic liver disease.