7A). Timepoints that showed peak expression in culture and after PHx from previous experiments were chosen for comparison. To make the results more comparable, primers were designed in a common region with same sequence for rats and mice. Considering the specific

gene expression for hepatocytes plated for 2 hours as 1-fold, we found that the expression of cMyc and Klf4 at mRNA level was more in culture (49- and 1,573-fold, respectively) than in MESC (1.63- and 891-fold, respectively). Oct4 and Nanog expression was more in MESC, and REST expression in culture (13-fold) was close to that in MESC (16-fold). Oct4 and Nanog induction was more after PHx than in culture, whereas that of cMyc, Klf4, and REST was less than that in culture. Oct4 induction in culture was 4-fold, which was close to the levels in normal rat liver. Protein expression of reprogramming PLX-4720 nmr factors 1 day after PHx was compared to the protein expression of MESC (Fig.7 B-E). Although expression of REST, Oct4, Myc, and Nanog were less than that expressed in MESC, KLF4 expression was in fact more in cultured hepatocytes with growth factors as compared to MESC (Fig. 7B,C). On the other hand, KLF4 expression

did not seem to change much after PHx (Fig. 7D,E). At the same time, GS-1101 in vivo Myc protein expression after PHx was more than in MESC (Fig. 7D,E). Our study suggests that the expression of transcription factor

REST and the downstream reprogramming factors Oct4, cMyc, Nanog is crucial for the survival of normal hepatocytes in culture and that their expression might have an antiapoptotic effect on hepatocytes. The fact that inhibition of REST leads to cell death suggests that REST, Oct4, cMyc, and Nanog act as survival factors for hepatocytes in culture. The fact that Klf4 is up-regulated during hepatocyte proliferation (Figs. MCE公司 1, 2) but its unchanged protein levels after REST-inhibition are not sufficient to save the hepatocytes from apoptotic death (Fig. 4) suggests that Klf4 may have a role in proliferation but not in survival of hepatocytes. We saw high levels of Oct4, Nanog, and Klf4 protein at 0d (2 hours after plating, Fig. 2). Although the mRNA for these reprogramming factors seems to increase with time in culture (Fig. 1), their protein levels seem to decrease in culture without growth factors and the levels are simply maintained in culture with growth factors. This can be explained based on our data from Fig. 7A where we compare the mRNA for reprogramming factors under varied experimental conditions. Considering the specific mRNA levels for hepatocytes plated for 2 hours as 1-fold, Oct4 mRNA expression in normal rat liver was 4-fold.