Hepatocyte-specific partial cellular reprogramming via selective OSK mRNA lipid nanoparticle attenuates liver fibrosis

Liver fibrosis is a major global health burden with no approved therapies. Transient expression of reprogramming factors Oct4 , Sox2, and Klf4 ( OSK ) promotes tissue regeneration without inducing full pluripotency, which represents an attractive regenerative therapy. Here, we introduce a hepatocyte-specific mRNA delivery strategy for in vivo partial cellular reprogramming using a chemically defined lipid nanoparticle (LNP) platform. We synthesized a series of natural unsaturated fatty alcohol-based ionizable lipids and identified a lead compound, H4T3, with mRNA delivery efficacy comparable to SM102. Further formulation optimization led to a simplified, phospholipid-free, three-component LNP formulation, H4T3_F6 that exhibits high potency and enhanced hepatocyte selectivity, alongside minimal immunogenicity and an overall favorable safety profile. Hepatocyte-specific delivery of OSK mRNA via H4T3_F6 LNPs transiently reprogrammed fibrotic hepatocytes into progenitor-like cells, rejuvenated hepatic gene expression, and promoted functional regeneration. This rejuvenation process downregulates fibrogenic mediators ( Tgfb1 , Pdgfb ), disrupting hepatocyte-stellate cell signaling and halting extracellular matrix (ECM) deposition. The integrated reprogramming and paracrine modulation collectively shift the liver microenvironment from a fibrotic to a regenerative state in a CCl 4 -induced liver fibrosis mouse model. This study provides proof-of-concept for rejuvenating fibrotic livers via selective mRNA-based in vivo cellular reprogramming, offering a promising strategy for liver fibrosis or age-related tissue repair. • The Simplified, phospholipid-free, three component H4T3_F6 LNP shows superior mRNA delivery potency, strong selectivity, and minimal immunogenicity. • H4T3_F6-mediated OSK mRNA delivery transiently reprograms fibrotic hepatocytes, promoting functional hepatic regeneration. • Reprogramming rejuvenates hepatic gene expression and reduces fibrogenic signaling, effectively reversing liver fibrosis.