Human Embryonic and Induced Pluripotent Stem Cell-Derived Cells as Preclinical Tools in Drug Discovery and Development

Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) have two unique properties: the self-renewal capacity and the broad developmental potential. They both have their advantages and disadvantages, but the current perception is that hESCs and hiPSCs complement rather than replace each other. New scientific problems and ethical challenges will arise because stem cell research is developing rapidly. The potential of hiPSC and hESC technologies in drug discovery is tremendous. The human pluripotent stem cell (hPSC)-derived cells have a potential to replace a part of the current preclinical toxicity and efficacy screening tests and to prevent misrouted drug development and use for lead optimization at phases before clinical trials. The hPSC-based disease models can also narrow the gap between traditional animal models and clinical trials. One major challenge is the differentiation process of hPSCs into cells of the relevant tissue. The recent study of our laboratory shows that the liver cell-deried acellular matrix (ACM) promotes the hepatic commitment of hESCs. To create chemically defined, xeno-free and feeder-free culture matrices for the differentiation of the hESCs into hepatocyte-like cells (HLCs), the ECM components of the ACM were characterized. The results suggest that the ACM contains fibronectin, laminins. After the characterization, the object was to identify which of the ECM proteins are essential and effective in the differentiation. A three-step differentiation protocol with differenent ECM protein solutions was used to produce HLCs. The hESCs were first induced into definitive endoderm (DE) cells. The DE cells were committed to the bipotential hepatic progenitors positive for HNF4α and AFP. Finally the progenitors were differentiated into HLCs. The mRNA expression of albumin, CK8, CK18, AAT, and BCRP was increased in HLCs. All the derived HLCs were albumin positive. The hESCderived HLCs showed hepatic morphology, cytoplasmic vacuole characteristics, and functional albumin secretion. The chemically defined matrices showed a supportive role in the differentiation of the hESCs into HLCs. This study establishes an efficient, chemically defined, xeno-free system to produce HLCs as a cell source for pharmaceutical and developmental studies.