Hepatocyte hnRNPK preserves mitochondrial integrity to restrain liver injury and fibrosis

BACKGROUND AIMS: Liver fibrosis is a global health issue with unclear unified drivers. The RNA-binding protein hnRNPK is critical for hepatic homeostasis, but its role in chronic fibrosis remains undefined. This study investigated hnRNPK-mediated splicing dysregulation in liver fibrosis and its therapeutic potential. APPROACH RESULTS: We mapped hepatocellular hnRNPK expression across a broad spectrum of human and murine fibrotic etiologies. Mechanistic insights were obtained by integrating snRNA-seq, hepatocyte-specific alternative splicing profiling, untargeted and spatial metabolomics, and 3D mitochondrial reconstruction using AT-SEM. We identified reduced hepatocellular hnRNPK abundance as a conserved hallmark of liver fibrosis across distinct pathogenic insults, including MASH, ALD, HBV, and DILI. Hepatocyte-specific Hnrnpk ablation in mice induced aberrant Opa1 splicing, specifically promoting exon 4b inclusion. This disrupted the balance of OPA1 isoforms, depleting L-OPA1 and driving severe mitochondrial fragmentation characterized by distinct "spheroid" ultrastructures. This loss of mitochondrial integrity triggered HSC activation through the cytosolic mtDNA-cGAS-STING pro-inflammatory signaling cascade and the mitochondria-containing pellet. Notably, restoring the hnRNPK-Opa1 axis via AAV-mediated overexpression of Hnrnpk or the Opa1-Δ4b isoform (lacking exon 4b), together with pharmacological promotion of mitochondrial fusion, effectively arrested and regressed established liver fibrosis in multiple murine models. CONCLUSIONS: Our findings establish the loss of hnRNPK as a central, unifying mechanism in liver fibrogenesis. By governing the Opa1 splicing axis, hnRNPK maintains mitochondrial integrity and prevents the pro-inflammatory signaling and secretome that fuel HSC activation. Targeting this RNA-mitochondria axis represents a potent, etiology-independent therapeutic strategy for chronic liver disease.