Potentiating stem cell-derived hepatocyte function

Abstract

The rat pancreatic AR42J-B13 (B-13) cell line differentiates into non-replicative hepatocyte-like (B-13/H) cells in response to glucocorticoid. As this response is dependent on the induction of serine/threonine protein kinase 1 (SGK1), this suggests a general essential role for SGK1 in hepatocyte maturation. To test this hypothesis, B-13 cells infected with AdV-SGK1F in the absence of glucocorticoid resulted in the expression of Flag-tagged SGK1F protein; increases in β-catenin phosphorylation; decreases in Tcf/Lef transcriptional activity; expression of hepatocyte marker genes and the conversion of B-13 cells to a cell phenotype near-similar to B-13/H cells. Given this demonstration of functionality, the effects of expressing adenoviral-encoded flag-tagged human SGK1F (AdV-SGK1F) in induced pluripotent human stem cells (iPSCs) was investigated. iPSCs directed to differentiate to hepatocyte-like cells using the standard protocol for chemical inhibitors and mixtures of growth factors, were infected with AdV-SGK1F at different stages of their differentiation to hepatocytes, either at an early point during differentiation to endoderm; during endoderm differentiation to anterior definitive endoderm and hepatoblasts and once converted to hepatocyte-like cells. SGK1F expression did not affect differentiation to endoderm, most possibly due to low levels of expression. However, expression of SGK1F in both iPSCs-derived endoderm and hepatocyte-like cells both resulted in the promotion of cells to an hepatoblast phenotype. These data demonstrate that the effect of expressing SGK1F in human iPSC-derived cells contrasts with its effects when expressed in B-13 cells. Given that SGK1 expression promotes an hepatoblast phenotype rather than maturation of human iPSC towards a mature hepatocyte phenotype, these data suggest a temporary role for Sgk1 in promoting a hepatoblast state in B-13 trans-differentiation to B-13/H cells.