Hepatocyte hnRNPK preserves mitochondrial integrity to restrain liver injury and fibrosis.

BACKGROUND AND 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 AND

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.