Prediction of hepatotoxicity for drugs using human pluripotent stem cell-derived hepatocytes.

Drug-induced liver toxicity is a main reason for withdrawals of new drugs in late clinical phases and post-launch of the drugs. Thus, hepatotoxicity screening of drug candidates in pre-clinical stage is important for reducing drug attrition rates during the clinical development process. Here, we show commercially available hepatocytes that could be used for early toxicity evaluation of drug candidates. From our hepatic differentiation technology, we obtained highly pure (≥98%) hepatocytes from human embryonic stem cells (hESCs) having mature phenotypes and similar gene expression profiles with those of primary human tissues. Furthermore, we optimized 96-well culture condition of hESC-derived hepatocytes suitable for toxicity tests in vitro. To this end, we demonstrated the efficacy of our optimized hepatocyte model for predicting hepatotoxicity against the Chinese herbal medicines and showed that toxicity patterns from our hepatocyte model was similar to those of human primary cultured hepatocytes. We conclude that toxicity test using our hepatocyte model could be a good alternative cell source for pre-clinical study to predict potential hepatotoxicity in drug discovery industries.

ER stress reliever enhances functionalities of in vitro cultured hepatocytes.

Endoplasmic reticulum stress (ER stress) leads an unfolded protein response (UPR) which results in internal cellular responses such as proteostasis and protein clearance. Recently, several reports demonstrated that the ER stress in stem cells could affect their stemness and fates to differentiate into certain lineages. However, the potential for controlling differentiation and function of cells by regulating ER stress needs to be further addressed. Here, we demonstrated that relieving the ER stress in cell cultures enhances the functionalities of hPSC-derived hepatocytes and other hepatic cells to be used in various research fields. Firstly, we found that UPR genes were up-regulated during hepatic differentiation of hPSCs and treatment of ER stress reliever at the hepatic induction stage of the differentiation resulted the enhanced mature marker expressions and glycogen storage of the differentiated hepatocytes. The treatment of ER stress reliever also improved the maintenance of hepatic characteristics in long-term culture of hPSC-derived hepatocytes. Furthermore, relieving ER stress increased the hepatic marker expression and CYP3A4 activity in hepatoma cell lines and human primary hepatocytes. Taken together, our findings indicate that regulating ER stress of in vitro cultured hepatocytes might be a crucial factor for enhancing differentiation, function and maintaining hepatic identity.