Hepatocytes-derived MPs, MP-free supernatants, MP+Vanin-1 neutralizing antibody (VNN1 nAb) and controls were used to treat HSC (LX2 and primary human HSC) for 6 and Everolimus in vivo 24hrs. Migration was assessed by Boyden’s

chamber and wound healing response while HSC activation was determined by quantitation of the expression of pro-fibrogenic markers. Internalization of MPs into the HSCs was studied by immunofluorescence. Results. Exposure of HSC with hepatocytes-derived MPs resulted in significant increase expression of key pro-fibrogenic genes, including α-SMA, TIMP1 and Collagen-I (p<0.01) and proliferation (MPs vs. MP-free supernatant, p<0.04). Exposure of primary HSC and LX2 cells to MPs released by hepatocyte during lipotoxicity resulted in a significant phenotypic change characteristic of their activation, with increased migration (MPs vs. MP-free supernatant, p<0.001) and wound healing response (MPs vs. MP-free supernatant, p<0.002) mainly after 24hrs of incubation. MPs internalization by HSC was crucial for the MP effects and was mediated at least in part through a Vanin-1 -dependent

mechanism. Indeed activation and migration of HSC were significantly abrogated by neutralizing Vanin-1 on the MPs by a specific Epigenetics inhibitor neutralizing antibody (MP vs. MP+VNN1 nAb, p<0.04). Conclusion. Our study demonstrates that MPs released from dying hepatocytes during lipotoxicity are critical signals that contribute to HSC activation in a process dependent on Vanin-1 expression. These results provide a mechanistic link between MPs and liver fibrosis and has important

implications for development of novel diagnostic and therapeutic see more strategies for patients with this condition. Disclosures: Maurizio Parola – Independent Contractor: Shire Pharmaceutical Ltd, Basingstoke, UK The following people have nothing to disclose: Davide Povero, Akiko Eguchi, Chiara Busletta, Erica Novo, Ariel E. Feldstein Introduction: PDGF and TGF-β contribute to hepatic stellate cell (HSC) activation process under pathological conditions such as metastatic tumor growth in the liver. PDGFs regulate the proliferation and migration of HSCs and TGF-β induces transdiffer-entiation of quiescent HSCs into myofibroblasts. It is believed that different intracellular adaptor proteins downstream of PDGF and TGF-β receptors making these two signaling pathways functionally divergent. For example, AKT, MAPK and PLCγ are major signal intermediates of PDGF receptor tyrosine kinases and SMADs serve this role for TGF-β receptor serine/threonine kinases. Although TGF-β can also activate AKT and MAPK to some extent, evidence to support a convergence of these two independent signaling pathways for HSC activation remains scarce. Hypothesis: We tested a hypothesis that PDGF receptors may participate in the TGF-β signaling by binding to TGF-β receptors in HSCs. Methods: Lentiviral vectors encoding PDGF receptor alpha (PDGFRα) or beta (PDGFRβ) were used to knockdown PDGFRα or PDGFRβ in HSCs.