These latest results show that the ES cells need to be genetically modified and extensive manipulation in vitro before they can be transplanted safely. Direct transplant of ES cells are known to give rise to teratomas and uncontrollable cell proliferation. There is already evidence that ES cells are genetically unstable in long term culture, and are especially prone to chromosomal abnormalities. The risks involved in using the cytomegalovirus promoter to drive over-expression of the transcription factor are undetermined. To avoid immune rejection, the ES cells have to be tissue-matched from a bank of stem cells created from ‘spare’ human embryos. Otherwise, a special human embryo has to be created for the purpose, by transferring the patient’s genetic material into an empty egg, a procedure prone to failure and morally objectionable to many, including scientists.

By contrast, adult stem cells could be transplanted directly without genetic modification or pre-treatments. They simply differentiate according to cues from the surrounding tissues and do not give uncontrollable growth or tumours. The adult stem cells also show high degrees of genomic stability during culture. There is no problem with immune rejection because the cells can readily be isolated from the patients requiring transplant. And there is no moral objection involved. Better yet, research can be directed towards encouraging adult stem cells to regenerate and repair damaged tissues in situ, without the need for cell isolation and in vitro expansion. By minimising intervention, risks are reduced, as well as cost, making the treatment available to everyone and not just the rich.