We are at the juncture between the old medicine and the new - still mired in the limitations of the old but able to see on the horizon something utterly different in conception. That way is so new, so revolutionary, so transforming, that it deserves the name it has received. We are entering the world of regenerative medicine. We will remake ourselves - rebuilding and replacing the parts of our bodies that let us down; the parts that have sickened, degenerated or ceased to function.
Medicine of the 21 st century will have a new paradigm as the focus turns inward, to understand and harness the ways our bodies function on the molecular and cellular levels. Unlike today's other profound biomedical revolution - a high tech affair involving decoding our genome - stem cell research is a much more low-tech enterprise. It's not lack of scientific tools that is the main impediment; it is restrictive laws and public policies.
The first fruits of these revolutions will not come next week or next year, so it is important not to raise public expectations unrealistically. How to precisely direct the transformation of embryonic stem cells down predictable and desirable pathways remains unknown. But we could see some applications entering clinics in five years or so. These could address such hitherto intractable diseases as Parkinson's disease and diabetes, or even such scourges such as end stage heart failure.
A stem cell can come from an embryo, fetus or adult. It has two properties. Under the right conditions it can reproduce itself and it can also give rise to the specialized cells that make up the tissues and organs of the body. Human embryonic stem cells are "pluripotent," which means that they have the potential to develop into all basic tissue types and hence to provide a virtually limitless source of cells for transplantation.
Another kind of stem cell is also in the news - the adult stem cell. These are found in major organs and they both self-renew and give rise to specialized cells. There have been stunning advances in getting these cells to change their destiny - transforming blood cells into nerve cells, for example. Such evidence fuels the moral debates about embryo research.
Those opposed to embryonic stem cell research believe in the absolute sanctity of the human embryo. As this is a minority view, they often couch their arguments in scientific rather than moral terms. In testimony before the UK's House of Lords Select Committee on Stem Cell Research, one "expert" actually stated that not only were adult stem cells just as promising as embryonic stem cells (untrue, according to the prevailing scientific consensus) but they were even better - more versatile, more malleable.
Of course, embryo research involves legitimate moral concerns, and it is the British who subjected these concerns to the earliest and the most sustained examination. That is only fitting because it was in the UK that a new and problematical moral construct - the embryo in a dish - came into being in 1978, with the birth of the first "test tube" baby, Louise Brown, the product of in vitro fertilization. There were no moral paradigms to deal with the extra corporeal embryo. Abortion ethics is of little help, although the opponents are often but not always the same.
No, a new way of thinking was required and Britain provided that with the Warnock Report of 1984. Its conclusions were enshrined in the Human Fertilisation and Embryology Act of 1990.
Under British analysis, the embryo outside the body did have moral status, but only after the appearance of the so-called primitive streak on or about the 14 th day of development. Before that, it could not be said to be a unique, identifiable future person; it might still split and become twins. Embryo research was allowed for purposes such as improving the efficiency of IVF. It was only a small step for the British to allow stem cell research as a permissible purpose.
Most people approve of in vitro fertilization, but it is the technology that gives the infertile the chance to be parents that also poses moral questions. IVF is inefficient so extra embryos are produced in case they are needed. These are frozen and many if not most are discarded.
Improving IVF also requires embryo research. Does it make any moral sense to say that embryos destined to be destroyed should not be used for life saving stem cell research? Embryonic stem cells are derived from an early embryo called blastocysts at about the 5 th day. At this point, the embryo is a hollow ball of about 100 cells, none of which can be identified as destined to become any particular part of any particular human being.
Stem cell research requires a sensible, predictable policy environment in order to flourish. Paradoxically, given its enormous impact on basic research in biological sciences, the United States is not leading this effort and, perhaps, is not even a major player.
For more than twenty years, anti-abortionists have so frightened America's Congress that it left the field of assisted reproduction unregulated at the national level. So there is no policy framework within which to situate stem cell research or reproductive or therapeutic cloning. Into this vacuum has stepped President Bush. But his belief in the absolute sanctity of the early embryo is not shared by a majority of Americans.
The President's stem cell policy - developed without consulting Congress - impedes US science and cruelly prolongs the agony of millions of sick and suffering people. Scientists elsewhere must forge ahead without America. Their work - their dreams - will change all of our lives for the better.