Project Summary Liver fibrosis is a wound healing process characterized by the accumulation of excess extracellular matrix (ECM) in the liver. Alcohol abuse is one of the most common causes of liver fibrosis/cirrhosis in western developed countries, accounting for more than 50% of cirrhosis cases. If left untreated, liver fibrosis will develop into liver cirrhosis, which is irreversible and affects nearly 633,233 adults in the United States. Unfortunately, there is no standard treatment for liver fibrosis till now. Therefore, effective antifibrotic medicines are needed urgently The accumulation of type I collagen in fibrotic liver is primarily due to an increase in the half-life of its mRNA in activated hepatic stellate cells (HSCs). We recently demonstrated that blocking PCBP2 expression using siRNA can efficiently decrease the stability of the collagen α1(I) mRNA and subsequently reverse alcohol- and cytokine-induced fibrogenesis in HSCs. We also discovered an IGF2R-specific peptide that can be used to specifically deliver cargos to activated HSCs. We will improve our current nanocomplex system to enhance the delivery of the PCBP2 siRNA to activated HSCs. It has been well established that the activation and proliferation of HSCs is the central event in liver fibrogenesis. Recently, experimental and clinical studies have shown that inducing apoptosis of activated HSCs in fibrotic liver is a rational and potential anti-fibrotic approach. It was found that HSCs inhibit T cells and B cells through PD-L1 on the surface of HSCs. PD-L1 is overexpressed in activated HSCs, leading to the strong immune modulatory activity of the activated HSCs against T-cell response. Activated HSCs exert inhibitory effects on infiltrating CD8+ T cells and induction effects on CD4+CD25+ regulatory T (Treg) cells. The immune modulatory activity of activated HSCs can be reversed by anti- PD-L1 antibodies to block the PD-1/PD-L1 interaction. We therefore hypothesize that anti-PD-L1 inhibitor can be utilized to restore the activity of infiltrating T cells in the fibrotic liver to clear activated HSCs which overexpress PD-L1. Our strategy is to develop a combination therapy to reverse the accumulated type I collagen using PCBP2 siRNAs and induce apoptosis of activated HSCs using PD-L1 inhibitors. Our central hypothesis is that alcoholic liver fibrosis can be reversed by targeting two different key steps in liver fibrogenesis.