Human Induced Hepatocytes(hiHep) Used In Cholestatic Liver Injury

Drug induced liver injury(DILI)is one of the main reasons leading to the failure of new drug research and development.Among it,nearly half of drug-induced liver toxicity belongs to cholestatic liver injury.At present,human primary hepatocytes(PHH)are still the gold standard for predicting DILI including cholestatic liver injury in vitro.However,the high cost,the lack of passage,and batch-to-batch variability limit their use.Recent studies have shown that human induced hepatocytes(hiHep)derived from human fibroblast by transdifferentiation have mature hepatocyte characteristics.Therefore,our aim is to confirm the metabolic detoxication and transport function in hiHep cells,and then explore their potential in drug hepatotoxicity,especially cholestatic liver injury and the relevant mechanism.The results showed that hiHep cells were able to express cytochrome P450(CYP450)enzymes and transporters,and had enzymic activity and transport function,which made them have the ability to evaluate drug-induced toxicity.Moreover,hi Hep cells highly expressed bile acid(BA)synthases and BA transporters,and intracellular and extracellular BA components were detected in hiHep cells for the first time,implying that hiHep cells had the ability of BA synthesis and secretion.Moreover,similar to PHH,hiHep cells also could study the toxicity of BAs and the potential mechanism.It was found that many kinds of representative cholestatic agents inhibited efflux transporter bile salt export pump(BSEP),similar to that in primary hepatocytes.Those drugs-induced toxicity responses in hiHep cells had a positive correlation to those in PHH(r2=0.8032).Based on this,we evaluated the protective effect of therapeutic drugs in hiHep cells and found those drugs could efficiently inhibit BA-induced toxicity in hiHep cells.In this follow-up study,hiHep cells were used as the in vitro model to investigate whether lipid-lowering statins had the protective effect against cholestatic liver injury.The preliminary results showed that fluvastatin could increase deoxycholic acid(DCA)-induced low cell viability and glutathione level in hiHeps.The potential mechanism of fluvastatin protection may be dependent on the down-regulation of p38 phosphorylation,but do not rely on the NRF2 signal pathway and activate ERK and JNK in mitogen activated protein kinase(MAPK)signal pathway.For the first time,these studies demonstrated that hihep cells expressed BA synthases and transporters,which made hiHep be a novel suitable cell model for the evaluation of hepatotoxicity,especially for the evaluation of cholestatic hepatotoxicity.In addition,hiHep cells could also screen potential liver protective drugs and undergo the relevant mechanism study.