Liver Cells Derived from Stem Cells Will be Used to Test New Drugs

Human embryonic stem cells (hESCs) are obtained from very early stage embryos obtained by in vitro fertilization, which are not going to be used for reproduction. However, the source of these cells remains ethically controversial for some people. Fortunately, during recent years, many laboratories have demonstrated that it is also possible to produce some stem cells from patient skin cells (fibroblasts). These new cells are called human induced pluripotent stem cells (hiPSCs). Both types of stem cells (hESCs and hiPSCs) are able to replicate indefinitely. They could provide an unlimited source of cells for various applications. Both of these stem cells are also in principle able to differentiate into most of the body’s cell types. However, the development of methods to induce specific differentiations into brain cells, heart cells or liver cells remains a challenge.

In the January 2012 issue of Molecular Therapy,Takayama et al. reported a new method to induce the differentiation of hESCs and hiPSCs into liver cells. They have introduced 3 genes, called SOX17+HEX+HNF4α,in the stem cells with an adenovirus vector. This is a virus in which the endogenous viral genes have been replaced by the desired gene. These genes induced the differentiation of the stem cells through various stages during the embryologic development. The SOX17 gene first induced the differentiation of the stem cells in endoderm, while the HEX gene induced further differentiation in hepatoblasts. Lastly, the HNF4α induced the differentiation in hepatocytes (the liver cells).

The liver cells derived from the stem cells will be used to test in culture the toxicity of new drugs during early phase of pharmaceutical development. The liver cells derived from the hiPSCs of patients with a hereditary liver disease could also be used to specifically test the efficacy of new drugs to treat this disease before patient trials.