Hepatocyte Mettl3 Deficiency Drives Primary Sclerosing Cholangitis and Liver Fibrosis via Cholangiocyte-Macrophage Crosstalk.

Effective therapies for primary sclerosing cholangitis (PSC), a progressive cholestatic liver disease characterized by biliary inflammation and fibrotic damage, remain limited due to an incomplete elucidation of its underlying molecular mechanisms. Although N6-methyladenosine (m6A) RNA methylation has been implicated in hepatic pathophysiology, its role in PSC remains undefined. Here, we demonstrate that hepatocyte-specific deletion of Mettl3, a critical m6A methyltransferase, induces spontaneous PSC-like pathology characterized by ductular reaction and peribiliary fibrosis. Therapeutic restoration of Mettl3 through genetic knock-in or AAV8-mediated hepatocyte-specific overexpression significantly attenuated 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced PSC progression. Integrated single-cell and bulk transcriptomic profiles revealed an expansion of Trem2+ macrophages that interact with Spp1high cholangiocytes via the Cd44-Spp1 axis. Genetic ablation of Trem2 or cholangiocyte-specific deletion of Spp1 significantly suppressed DDC-induced biliary injury. Mechanistically, Mettl3-deficient hepatocytes secreted higher levels of macrophage-recruiting cytokines (such as Mif and Csf1), facilitating the recruitment of Trem2+ macrophage, which subsequently activated cholangiocytes through Cd44-Spp1 signaling, exacerbated biliary inflammation and fibrosis. Notably, pharmacological activation of Mettl3 in adult hepatocytes substantially mitigated PSC progression and liver fibrosis. Collectively, our findings establish hepatocyte Mettl3 deficiency as a pivotal driver of PSC pathogenesis and highlight the therapeutic potential of targeting the m6A epitranscriptome in cholestatic liver diseases.