CREPT aggravates liver fibrosis through TGF-β activated-Smad2/3 but not Smad4 in hepatocytes

Background & Aims: Liver fibrosis, a serious medical condition with limited therapies, frequently progresses to cirrhosis and other severe complications. Here, we report that cell cycle-related and expression elevated protein in tumor (CREPT) is up-regulated in liver fibrosis. CREPT preferentially enhances transforming growth factor-β (TGF-β)-activated Smad2/3, rather than the canonical Smad2/3-Smad4 complex, thereby facilitating liver fibrosis progression. Methods: We analyzed public transcriptomic and proteomic datasets from patients with liver fibrosis. Human tissue arrays and mouse models of fibrosis were used to investigate CREPT expression patterns. Hepatocyte-specific overexpression (TG-CREPT) and deletion (CREPThep-/-) mice were subjected to acute liver injury (24 h, high-dose CCl4), chronic fibrosis (28 d, low-dose CCl4), and bile duct ligation (BDL) to induce liver fibrosis. Histological, biochemical, and RNA-sequencing (RNA-seq) analyses and CUT&Tag experiments were conducted. Results: CREPT is predominantly enriched in hepatocytes and upregulated in fibrotic liver tissues from patients and mice induced by CCl4 or BDL. Overexpression of CREPT in hepatocytes exacerbates liver injury and fibrosis in mice under acute or chronic CCl4 exposure and BDL challenge. In contrast, hepatocyte-specific deletion of CREPT significantly alleviates liver fibrosis. Mechanistically, CREPT aggravates TGF-β/Smad signaling pathway, preferentially interacting with Smad2/3, but not Smad4, to promote inflammatory responses, and up-regulates fibrogenic genes, including Cebpd, Fosl2 and Fn1. Intriguingly, targeting CREPT with LNP-delivered siRNA (LNP-siCREPT) and GalNAc-delivered siRNA (GalNAc-siCREPT) significantly reduces pre-existing liver fibrosis in mice. Conclusions: Our findings identify a promoting effect of CREPT on liver fibrosis through TGF-β-activated Smad2/3 but not Smad4. Targeting CREPT represents a potential therapeutic strategy for liver fibrosis.