• liver
• stem cells

Ever since Ernest McCulloch and James E Till defined essential stem cell properties, the field of stem cell biology has attracted increasing interest.1 Manipulating embryonic stem cells has resulted in advanced genetic technologies such as knock-out and transgenic animals, providing valuable models to study genetic influence on a wide variety of diseases.2 The success in manipulating stem cells and the ability to differentiate them into diverse tissues brought with them countless concepts of utilising stem cells in medicine. The idea of perpetually dividing pluripotent cells, capable of differentiating into nearly every possible cell or tissue type, seems like an inexhaustible resource for regenerative medicine. At the same time it became increasingly clear that stem cells are not just beneficial since tumours of various origins also contain stem cells that help them to proliferate but also to escape conventional chemotherapy. Furthermore, even embryonic pluripotent stem cells have a tumourigenic potency, which is one of the major hurdles to their utilisation in therapeutic concepts. Thus, the existence of stem cells must be considered a double-edged sword.3

In general, adult stems cells may be found in multiple human tissues, among them the liver. These cells multiply by cell division and were described as replenishing dying cells and regenerating damaged tissues. Besides, these adult stem cells may also transdifferentiate into a whole spectrum of cell types of other tissues, the physiological relevance of which is still open to debate.4

The existence of stem cells in normal liver is widely accepted. They may be augmented by immunoselection for epithelial cell adhesion molecule-positive (EpCAM+) cells and are estimated to constitute ∼0.5–2.5% of the liver parenchymal cells. Furthermore these EpCAM+ liver cells were demonstrated to possess stem cell characteristics, as transplantation of …