Browsing by Author "Porola, Pauliina"

Hepatotoxicity is an undesired feature of many drugs and is one of the main reasons for attrition during the drug development process. Although an in vitro model can never totally correspond to or replace a whole organism, a reliable in vitro model for liver toxicity screening would help to detect liver toxicity earlier in the development process. Effective and early in vitro screening would reduce the need of animal subjects and clinical trials and thus would be both ethically more acceptable and more cost-effective. Currently mostly used models for liver metabolism and toxicity studies are primary hepatocytes, hepatic cell lines and animal models. However, these models have many drawbacks and are not considered reliable. Human embryonic stem cells (hESCs) are pluripotent cells that can be differentiated into many specialized cell types including hepatocytes. They are also self-renewable and thus represent an unlimited and promising source of hepatocytes to be used as a tool in in vitro liver toxicity testing of drug candidates. The aim of this study was to produce hepatocytes from hESCs via multiple steps following the in vivo pathway of developing hepatocytes: first hESCs were differentiated into definitive endoderm cells, after which they were differentiated into hepatic progenitor cells. Finally, hepatocyte-like cells (HLCs) were induced from the progenitor cells. Our specific interest was the use of hepatic cell derived acellular matrix as a differentiation basis for hepatic progenitors and hepatocytes. We also studied the effect of Matrigel overlay on the hepatic differentiation. Differentiation method without the Matrigel overlay was promising. HLCs showed correct hepatocyte-like morphology and expressed hepatocyte markers such as albumin, α-antitrypsin, CYP3A4 and HNF4α both on mRNA and protein level shown by qPCR and flow cytometry and immunofluorescence staining, respectively. Accordingly, the expression of stem cells marker SSEA-3 showed a tendency to decrease as the differentiation proceeded. HLCs also functionally resembled hepatocytes shown by albumin production. However, we could not detect other hepatocyte functions such as urea production or CYP activity. With Matrigel overlay, the hepatocyte-like morphology of the cells was lost, no albumin production was shown and the expression of several hepatocyte markers was lower than in the experiment done without the Matrigel overlay. Thus, Matrigel overlay was shown to be unbeneficial for hepatocyte differentiation. In conclusion, we showed that differentiation of hESCs on the acellular matrix with specific growth factors and without the Matrigel overlay seems promising as a method to produce HLCs. This preliminary study serves as a basis for future studies, in which the differentiation method should still be further studied and developed to yield functional HLCs of uniform quality.