LONDON, August 18. A mixture of horror and excitement greeted the British government's decision this week to allow stem cell research and therapeutic cloning. For most scientists, the risk–benefit balance is clearly weighted in favour of such research, and the decision heralds a new era of therapeutic possibilities. But for many people in Britain it smacks of eugenics and meddling with the sanctity of life. So what is all the fuss about?
On Wednesday Tony Blair's government endorsed the conclusions of an expert committee led by Liam Donaldson, the chief medical officer, that embryonic stem cells — primordial cells that can differentiate into any mature cell type given the right conditions — have "enormous potential" to create new forms of treatment for currently incurable diseases. At present, research on human embryos up to 14 days old is permitted for a handful of specific purposes related to infertility. Animal studies, mainly in mice, have generated substantial evidence that stem cells could provide an entirely new, and much needed, source of tissue for transplantation as well as offering the possibility of new treatments for many common diseases. For years scientists have been urging the government to review the legislation. Now, the scene is set for major research programmes to refine stem cell and tissue transplantation techniques.
The Donaldson committee considered various sources of stem cells and concluded that those derived from early embryos have the greatest potential to develop into most types of tissue — a property known as pluripotency. The therapeutic applications of tissue derived from stem cells are considerable: specific tissue types could be harvested for repair of failing organs (for example, insulin-secreting cells in diabetes) or for replacement of diseased or damaged tissues (eg, nerve cells in stroke or Parkinson's disease).
The committee also gave the go-ahead to limited research in therapeutic cloning — the creation of embryos by cell nuclear replacement — which might be applied to treat some rare but serious inherited disorders. For example, it could be possible to prevent a child from inheriting damaged mitochondria from the mother by inserting the nucleus of the mother's egg into a healthy donor egg that has had its nucleus removed. The committee concluded that, provided the necessity of the technique is proved on a "case-by-case basis" and with full consent of the donors, the benefits of discovering the mechanism for reprogramming adult cells justifies this transitional research.
Many technical issues are still to be resolved, and fundamental work is needed to identify the chemicals necessary to promote growth and specialisation of stem cells. There are also questions over safety: for example, will cells and tissues produced by nuclear replacement develop normally, will they be more prone to malignancy, and will they really circumvent the problem of rejection by the immune system? Most scientists consulted by the committee felt that the research was still several years away from being able to deliver actual healthcare benefits.
Nonetheless, the government's support for the controversial research represents a momentous decision that could catalyse similar moves in other industrialised countries. There is pressure for change in the US, where government researchers are banned from working on stem cells. The ban does not apply in the private sector, however, and calls are intensifying for government labs to be allowed to do such research to avoid monopolisation for private gain. Within weeks, the National Institutes of Health is expected to issue guidelines allowing federal researchers to work on, but not harvest, stem cells from embryos. In Britain, the final decision on the issue will be left to a free vote of MPs later this year.