LAUSR

BACKGROUND AND AIMS Messenger RNA (mRNA)-based therapeutics are rapidly progressing to the clinic and hold tremendous potential for benefiting millions of people worldwide. Therapeutic targeting of injuries that require transient restoration of proteins by mRNA delivery is an attractive aspect, however until recently, it has remained poorly explored. In this study, we examined for the first time, the therapeutic utility of mRNA delivery in liver fibrosis and cirrhosis, which contributes to millions of deaths, annually. Here, we aimed to demonstrate therapeutic efficacy of the human transcription factor hepatocyte nuclear factor alpha (HNF4A) encoding mRNA in chronically injured murine liver leading to fibrosis and cirrhosis. METHODS We investigated restoration of hepatocyte functions by HNF4A mRNA transfection in vitro, and analyzed the attenuation of liver fibrosis and cirrhosis in multiple mouse models, by delivering hepatocyte-targeted biodegradable lipid nanoparticles (LNP) encapsulating HNF4A mRNA. To identify potential mechanisms, we performed microarray-based gene expression profiling, single cell RNA sequencing, and chromatin immunoprecipitation. We used primary liver cells and human liver buds for additional functional validation. RESULTS Expression of HNF4A encoding mRNA led to restoration of metabolic activity of fibrotic primary murine and human hepatocytes in vitro. Repeated in vivo delivery of HNF4A mRNA encapsulated-LNP induced a robust inhibition of fibrogenesis in four independent mouse models of hepatotoxin- and cholestasis-induced liver fibrosis. Mechanistically, we discovered that paraoxonase 1 is a direct target of HNF4A and it contributes to HNF4A-mediated attenuation of liver fibrosis via modulation of liver macrophages and hepatic stellate cells. CONCLUSION Collectively, our findings provide the first direct preclinical evidence of the applicability of HNF4A mRNA therapeutics for the treatment of fibrosis in the liver. LAY SUMMARY Liver fibrosis and cirrhosis remain unmet medical needs and contribute to high mortality, worldwide. Herein, we take advantage of a promising, emerging mRNA therapy approach to treat liver fibrosis and cirrhosis. We demonstrate that restoration of a key gene, HNF4A, via mRNA encapsulated in lipid nanoparticles decreased injury in multiple mouse models of fibrosis and cirrhosis. Our study provides the proof-of-concept that mRNA therapy would be a promising strategy for reversing liver fibrosis and cirrhosis.