Self-renewal and the capacity to differentiate into a multitude of mature cell types have made stem cells the hottest ticket in biomedicine. But there are questions aplenty, scientific and otherwise.
- Do we need more stem cell lines? President Bush may believe that the available lines are sufficient, but these are derived fro1m blastocysts produced in fertility clinics. Maximizing the impact of stem cells in medicine calls for new lines derived from specific diseases, like cancers.
- Must therapeutic cloning be used to generate new lines? Yes, transplanting nuclei from cells of adults with genetic disorders into enucleated eggs--therapeutic cloning--provides the obvious route to study disease development. In the longer term this approach could also provide genetically matched tissues for transplantation.
- Is transdifferentiation real? After five frantic years, current thinking hovers between "maybe" and "probably." While promising, most scientists do not (yet) consider transdifferentiation to be a replacement for therapeutic cloning.
- Have stem cells been used successfully in animal models of disease? Yes, most notably embryonic stem cells have been induced in vitro to become midbrain neural stem cells; transplanted into a rat model of Parkinson disease, these cells became functionally integrated and reversed behavioral defects.
- Have human clinical trials similarly achieved symptom relief? Too soon to tell; controlled studies are very rare. Re-searchers using cells derived from human fetuses have had some promising results, but cell-based therapies are likely to be many years away. And while biotech is beginning to engage, thus far none of the major pharma companies has shown much enthusiasm.
- Can a lid be kept on expectations? Hard to see how. The clamor from patients is growing, understandably so. Media coverage is incessant and has to strike a difficult balance between tomorrow's promise and today's reality.
- Have science journals led by example? Not completely. To quote a recent, creditably self-censuring article in Science magazine, "Plasticity was such a hot phenomenon in the late 1990s that journals, including Science, were snapping up and publishing partial--or what are now seen as questionable--results."
- Have the social, political, economic, legal, religious, and ethical issues been engaged? Most vigorously, and at the highest levels. The importance of the debate is without question but there is currently a lack of consensus, to a dangerous extent. Unfortunately, participants often seem insufficiently informed on scientific aspects and the full medical potential of stem cells.
- How has the research community responded? In many countries, scientific academies and associations have provided reports; scientists have participated unstintingly in expert panels and committees; and the science journals have provided outstanding coverage.
- Research will flourish, but where? It depends in part on legislation that emerges from the debate. Right now certain countries, such as the United Kingdom, Sweden, France and Australia, are more accommodating than others, such as the United States and Germany. Will a "reverse brain drain" result?
If your important question was missed, please let me know.
Richard Gallagher (firstname.lastname@example.org) is editor of The Scientist.