Proteins were detected by enhanced chemiluminescence HRP substrate (Millipore). Statistics Data are shown as means and standard deviations. disruption of GJIC activities. Dynamic gap junction organization and internalization are phosphorylation-dependent and the p38 mitogen-activated protein kinases pathway (MAPK) can negatively regulate Cxs through phosphorylation-dependent degradation of Cxs. We found that p38 MAPK inhibitor SB203580 improved maturation of hESC-Heps correlating with up-regulation of Cx32; by contrast, the p38 MAPK activator, anisomycin, blocked hESC-Heps maturation correlating with down-regulation of Cx32. These results suggested that Cx32 is essential for cell-cell interactions that facilitate driving hESCs through hepatic-lineage maturation. Regulators of both Cx32 and other members of its pathways maybe Carotegrast used as a promising approach on regulating hepatic lineage restriction of pluripotent stem cells and optimizing their functional maturation. The liver is the major organ responsible for protein synthesis, metabolic transformation, and detoxification of xenobiotics as well as for metabolically handling endogenous substrates. The hepatocyte is the most important cell type for both cell therapy and liver regeneration for end-stage liver diseases and for toxicity evaluation during drug development in pharmaceutical industries1,2. However, primary human hepatocytes (PHH) are a severely limited resource given the shortage of donor livers. They cannot easily be expanded, and they lose their metabolic functions rapidly was a popular problem and one of the major challenges in research. Therefore, new experimental strategies are expected to achieve a successful differentiation of fully mature hepatocytes from pluripotent stem cells. Gap junctions are the pores coupling adjacent cells to mediate intercellular activities of gap junctional intercellular communication (GJIC), by which there is exchange of metabolites and electrical activity13. They are formed by connexons, iris-diaphragm-like structures composed of 6 connexins (Cxs) that can assume a closed position forming a small channel, or swivel open to form a larger channel. The Cxs comprise a large family of proteins and most cell types express more than one type of Cx. Both Carotegrast Cx expression and GJIC activity may vary with physiological and pathological states of Rabbit polyclonal to ZC3H12D the cell and tissue. The gap junctional exchange of small molecules between adjacent cells is crucial for maintaining Carotegrast tissue homeostasis14. Importantly, genetic mutations in Cx interfered with GJ function resulting in several diseases15,16,17. It was also suggested that Carotegrast GJIC and Cxs played critical roles in stem cell proliferation and differentiation. Schiller showed that inhibition of GJIC blocked the progression of pre-osteoblastic cells towards a mature, osteoblastic phenotype deduced that modulation of Cx43 altered expression of osteoblastic differentiation markers19. On the other hand, increasing Cx43 expression by the treatment of all-trans retinoic acid resulted in more differentiation and maturation of lens epithelial cells20. Furthermore, Cx43 overexpression potentiated and induced dentin sialophosphoprotein expression and enhanced odontoblastic differentiation of dental pulp stem cells21. Multiple forms of Cxs, including Cx26 and Cx32, were found in hepatic parenchymal cells in adult livers. There are ~90% Cx32 and ~5% Cx26 in well-organized tissue of adult liver, which establish an elaborate GJIC network between hepatocytes and become indispensable for functional differentiation22. In adult liver, Cx32 expression and GJIC activities positively correlate with CYP-mediated xenobiotic biotransformation23,24,25, glycogenolysis26,27, albumin secretion28, ammonia detoxification28 and bile secretion29. More importantly, Cx expression patterns in embryonic liver undergo lineage stage-dependent changes during hepatic differentiation and maturation process. Hepatic progenitor cells were indeed repeatedly found to switch from Cx43 to Cx26 expression and, in particular, to Cx32 expression upon differentiation into hepatocytes, both and and respectively and effectively improve33 or block37 hepatic gap junction communication and expression. was induced about 3-fold by VK2 at 50?M (Supplementary Fig. S2a). In contrast, addition of 2-APB to the last stage of differentiation caused reduction of these genes, and down-regulated by 3-fold at 50?M (Supplementary Fig. S2b). Therefore, subsequent differentiation was carried out at 50?M of VK2 and 2-APB. By day 20 of differentiation, cells induced with the treatment of VK2 were large and homogeneously polygonal shaped with bright junctions. A small fraction became binucleated (arrows), and these displayed more typical hepatocyte morphology than cells in DMSO-treated control group (Fig. 2a). To compare the gene expression of the hepatocytes induced Carotegrast under these conditions, a repertoire of hepatic markers were analyzed by qRT-PCR. These included plasma proteins (and and and and and and and were induced about 3-fold by SB at 10?M (Supplementary Fig. S2c). The expression of hepatic markers, including Cx32, ALB, AAT, OTC1, UGT1A4, MDR1, etc. were increased in hESC-Heps treated with SB than untreated cells (Fig. 3b). Additionally, immunostaining and flow cytometry data showed that cells treated with SB demonstrated more homogeneous and enhanced expression of ALB, Cx32, CK18, CPS1 and ECAD than untreated cells (Fig. 3c,d and Supplementary Fig. S4). On the contrary, anisomycin, an activator of p38 MAPK, disrupted hepatocyte differentiation and decreased expression of hepatic markers dramatically (Fig. 3bCd and Supplementary Fig. S4). This consistent outcome of treatment by VK2 which up-regulated Cx32 and.