It is now a decade since human embryonic stem cells were discovered, and since the UK legislated to facilitate cloning human embryos for research. Since then, barely a week has passed without new stem cell stories appearing. Last November, it was widely reported that the world's "first tailor-made replacement organ", a successfully transplanted trachea produced from stem cells, finally proved the enormous potential of embryonic stem cells. The Guardian trumpeted this as "a tribute in particular to the UK regulatory framework that enabled stem cell research to make such rapid strides", concluding that "the election of Barack Obama, committed to removing the block on federal funding for most stem cell research in the US, can only speed the process." So is this, as many end-of-year commentaries implied, game, set and match to the embryo research lobby, and defeat for those advocating stem cell science that does not involve destroying human embryos?
A moment's examination shows precisely the opposite. The truth is that the airway transplant was achieved with exclusively adult stem cells, while the Obama and UK regulation references relate exclusively to embryonic stem cells. Such conflation of unrelated stem cell developments - citing adult stem cell advances to promote embryonic stem cell research - is not rare. Gordon Brown, trying to persuade MPs to support animal-human hybrid embryo research, wrote: "With adult stem cells already being used as treatments for conditions including leukaemia, severe combined immunodeficiency, and heart disease, scientists are already close to the breakthroughs that will allow embryonic stem cells to be used to treat a much wider range of conditions."
In fact, as the advantages of other forms of stem-cell research become increasingly obvious, there is every reason to predict that the use of human embryos as a source of stem cells will decline substantially this year.
It is little realised but invariably true that every media stem cell story involving patients concerns adult cells; and every story about embryonic stem cells is about their potential, or animal experiments - not patients. Embryonic stem cells remain far too dangerous for clinical testing. Cross-infection and rejection are potential problems, but the biggest hazard is that embryonic stem cells form tumours. Biologically, they have much in common with cancer stem cells.
While this serious barrier to clinical use has not been solved, one dramatic advance in embryonic stem cell science was seen in 2008. Science's "Breakthrough of the Year," was a fundamentally new way of producing cells identical to embryonic stem cells - but which, crucially, involves neither creating nor destroying embryos. Inducible pluripotent stem cells (iPSCs) are made very simply (compared to cloning human embryos) by taking adult cells and artificially activating certain genes. This effectively turns back the cell "clock": it de-differentiates, gaining the properties and characteristics of embryonic stem cells, but without ethical compromise.
Sir Martin Evans, 2008 Nobel Laureate and discoverer 30 years ago of mouse embryonic stem cells, viewed this remarkable technique as "the writing...on the wall" for research using embryos. Over the past year, embryonic stem cell scientists everywhere have adopted it, abandoning work with human embryos. Professor James Thomson of Madison, Wisconsin, who first discovered human embryonic stem cells, predicted that "a decade from now, [research using human embryos] will be just a funny historical footnote."
But not so funny in ethical terms. As Thomson himself said, "If human embryonic stem cell research doesn't make you at least a little bit uncomfortable, you have not thought about it enough." The ethics are not complex. Human embryonic stem cells cannot be obtained without destroying embryos. Since no biologist or physician could ever deny that a human individual's life commences at conception (not birth, nor implantation, nor the time the primitive nervous system appears: these are stages of human life, not stages before life), embryonic stem cell research cannot occur without destroying living human beings.
Recognising if not the sanctity of the human embryo, then at least some form of moral status, the Lancet in 2001 declared that "...creating embryos with no purpose other than to use them as a source of stem cells is ethically unacceptable."
But the scientific excitement and alleged medical potential of embryonic stem cells (arguably amplified by the politics of abortion, which also implicitly devalues the human embryo), resulted in the widespread abandonment of such principles, with a huge expansion of human embryo research, new and ever more liberating legislation in the UK, including last year's law allowing the cloning of human-animal hybrids, and outcry in the US at the "Bush ban" on federal funding for many forms of embryonic stem cell research.
The paradox is that while 2009 might have seen new UK legislation combining with a new US president to open the floodgates for human embryo research, the likelihood is that such research may instead slow to a trickle.
While still carrying the therapeutic hazards of embryonic stem cells, including tumour formation, iPSCs offer a far easier and cheaper methodology than either cloning human embryos or obtaining stem cells from more traditionally produced embryos (i.e. on a Petri dish in an IVF clinic). So even those still convinced that embryonic stem cells, rather than adult ones, hold the key to the future, are more likely to pursue their aims with human iPSCs, not embryo-derived cells. Equally importantly, adult stem cell advances, often dramatic, now appear almost weekly - from tracheal transplants to the generation of a prostate from a single adult stem cell. These cells are safe, relatively accessible and avoid immune rejection (being derived from the patient himself, not other individuals). Adult stem cells also start with a medical and biological advantage: tissue repair is their evolved purpose. Repairing diseased adult tissue is hardly the evolutionary function of the embryonic stem cell.
So major increases in the volume of both adult stem cell research (and its translation to clinical trials in patients) and iPSC research are inevitable in 2009, but no headlong rush into new embryo-based experiments seems likely. Indeed, it is now authoritatively suggested that Barack Obama's "stem cell revolution" will not include "funding the derivation of new ES cell lines or the practice of research cloning".
The "stem cell wars" will recede gently into history. Most people neither know nor care who won. Research that destroys human embryos may slow to a trickle, though its advocates insist that both the iPSC technique and adult stem cell successes depended on earlier human embryo research - though in truth everything necessary could have been learned from studying adult cells themselves or rodent embryonic stem cells, the conventional paths to scientific progress. But the real victor in 2009, and in coming years, is the patient, for whom stem-cell research is finally beginning to deliver.