Because the use of ABS also results in growth arrest, absence of fetal growth factors, and/or presence of differentiation-inducing factors in adult serum could partly explain the observed changes. We hypothesize that the absence of growth-stimulating factors allows for growth arrest and provides the opportunity to form cell–cell contacts and tight junctions. Cell–cell contacts, in turn, are important factors in facilitating intercellular communication

and have been linked to increased hepatic functionality, including bile secretion, glycogenolysis, and ALB secretion.[9] Our current data suggest that an important difference between cells cultured in ABS-supplemented (or DMSO-supplemented) media PD332991 and cells cultured in HS-supplemented media is the intracellular lipid

stores. Our study indicates that only in HS is the lipid droplet content increased. The increased lipid content can, in turn, facilitate activation of lipid-dependent nuclear receptors, such as LXR-α, PPAR-α, and PPAR-γ, enabling de novo synthesis of lipids and lipoprotein secretion. The method we have presented in this study for culturing hepatoma cells provides a convenient, cost-effective model for the study of liver disease, lipoprotein secretion, and other liver-related processes. AZD2281 mouse We have used this model to produce HCV strain JFH-1 at high titers. When cells are differentiated, JFH-1 production in HS media exceeded that in FBS media by 1,000 times or more. We have achieved production of viral titers of over 108 RNA copies/mL for extended periods of time. Besides functioning as a production platform for HCV, this model can also provide further insight into the cellular factors and processes P-type ATPase essential for efficient production of HCV, resulting in virus that closely resembles HCV derived from patient sera. Additional Supporting Information may be found in the online version of this article. Supplemental figure 1. Comparison to DMSO and Adult bovine serum mediated growth arrest Historically, fetal serum has been used in

cell cultures because of the presence of high levels of growth stimulating factors. We wanted to determine if some of the same effects seen in HS (adult human serum) could be achieved by switching FBS to ABS (adult bovine serum). Also, HuH-7 or HuH-7-derived cells become contact inhibited by DMSO, as reported previously (4). We therefore characterized Huh7.5 cells grown in either FBS media further supplemented with DMSO (1%) or in media supplemented with adult bovine serum (ABS, 2%). Both ABS and DMSO supplementation resulted in growth arrest and changes in cellular morphology, however these changes were less pronounced than in HS; for example the increase in cells size that was observed under HS conditions was not observed in DMSO or ABS containing medium.