Vorinostat Can Reduce an Ongoing Fibrosis and Preserve Key Liver Metabolic Functions by Selectively Altering Mesenchymal Cell Differentiation

Liver fibrosis is a major global cause of mortality that is driven by the activation of hepatic stellate cells (HSCs) into extracellular matrix (ECM)-producing myofibroblasts (MyoFs). The lack of predictive human in vitro models has severely hampered the discovery of targeted anti-fibrotic therapies. Here, we describe a human iPSC-derived hepatic micro-organoid (microHO) model, which labels collagen producing cells, to study liver fibrosis pathophysiology and screen drug candidates. We discovered that while multiple drugs prevented fibrosis when co-administered prophylactically with TGFβ1, only the FDA-approved pan-HDAC inhibitor Vorinostat (SAHA) successfully reduced an established, ongoing fibrosis and preserved life-sustaining liver metabolic functions in a fibrotic microenvironment, including ammonia detoxification and CYP3A4-mediated drug metabolism. To uncover its mechanism of action, we utilized single-cell RNA sequencing and CRISPR-Cas12a lineage tracing. We found that Vorinostat actively redirects HSC differentiation away from pro-fibrotic MyoFs and toward a distinct, fibrosis-suppressing mesenchymal inhibitory (Mes ^Inh ) cell. By reversing TGFβ1-induced epigenetic silencing, Vorinostat opens condensed chromatin to rescue metabolic gene expression and generates anti-fibrotic effectors that neutralize ongoing TGFβ1 signaling. Given its distinct capacity to remodel mesenchymal cell fate and reverse epigenetic repression of metabolic genes at clinically achievable concentrations, Vorinostat represents a highly promising drug for repurposing as a therapeutic for advanced human liver fibrosis.