Human embryonic stem cell lines are contaminated: what should we do?

Human embryonic stem (hES) cells have the potential to differentiate into any desired cells and to be used in cell replacement therapies for some diseases. However, existing hES cell lines would not be suitable for the therapies as they are contaminated with other biological products. In order to produce the safest hES cell lines for therapeutic purposes, all steps for the establishment of hES cell lines must avoid the use of animal serum and/or animal feeder cell lines. Safe and fast approaches to producing hES cell lines based on recent research advances in both humans and animals have been suggested.