LIFE saving or life taking? That is the stark question that has dominated public discussion of embryonic stem cells. The debate, especially in the US, now centres on the intractable question of whether it is justifiable to create and then destroy an embryo in pursuit of medical progress. Well, here鈥檚 some news: important as this debate is, it does not even begin to exhaust the moral issues facing biologists and the wider public when it comes stem cells.
That embryonic stem cells can turn into virtually any body tissue has been known for some time, and further advances are as inevitable as they are desirable. With these advances will come new challenges for public policy, so earlier this year we set up a programme designed to address the next generation of ethical and policy issues. Here is a sample of the questions we have already identified.
As with any promising medical technology, there is tremendous pressure to move quickly from the laboratory to human trials. Patients suffering from conditions for which stem cell science seems particularly promising, such as Parkinson鈥檚 or spinal cord injury, are understandably impatient, and understandably willing to volunteer for research trials. Yet important questions about the safety of stem cell therapies have yet to be widely examined, let alone resolved.
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For instance, there is a theoretical risk that stem cells implanted into people will move around and end up in the wrong place, or, as they specialise, develop into the wrong sorts of cells. Or implanted cells might turn cancerous or be rejected by the body鈥檚 immune system. Before it is acceptable to conduct human trials, we need to establish what counts as sufficient animal data or other evidence of safety.
We also need to decide what types of diseases and patients it would be most ethical to test stem cells on. For example, should the first human trials involve patients unlikely to live long enough to develop tumours?
These difficult judgements will be made even harder by the fact that there is no one way to isolate or prepare 鈥渓ines鈥� of stem cells. Some lines may be safer and more effective than others; stem cells that are genetically identical to the patient, for example, should behave quite differently after implantation from stem cells derived from non-identical embryos or donors. Access to experimental data will be crucial to having an open debate about such issues. Researchers and regulators may have to work together to ensure that critical information is not withheld as a result of patent policies or other profit-related considerations.
A second major area of concern is over who will benefit. The goal of stem cell science ought to be to produce therapies that are not only safe and effective, but applicable and available to all. New medical technologies, however, are usually expensive, and thus their earliest 鈥� and sometimes only 鈥� beneficiaries are the economically privileged.
And if we are not careful, biological barriers to access that emerge from the science of stem cells may become entwined with economic ones. One of the major biological barriers to the widespread use of cell-based therapies is likely to be the problem of immune rejection, and here too there are currently more questions than answers. In one model, patients receive therapies that are derived from stem cells genetically identical to their own and thus pose no problems for rejection. At present, however, both the potential methods for obtaining such cells 鈥� from adult tissue or embryos cloned from adult cells 鈥� are incredibly expensive and time consuming. The worry is that for the foreseeable future only the wealthy may be able to afford this kind of bespoke cell therapy.
The ideal way to expand access might be to create 鈥渦niversal鈥� stem cell lines. These cells, genetically modified to evade immune attack, would enable doctors to offer patients a simpler and cheaper 鈥渙ff-the-shelf鈥� therapy. But we don鈥檛 yet know whether this strategy is technically feasible. If it is, should research in this area be accelerated?
Alternatively, we could use ordinary stem cells and rely on specialised drugs to keep the patient鈥檚 immune system in check. As with conventional organ transplantation, this approach is likely to work best if the donor cells share similar immune, or HLA, genes to those of the patient receiving the therapy. That suggests we should be building up banks of stem cells with a wide range of genetic make-ups. But what factors should influence our gathering of such cells? HLA gene frequencies, for instance, differ among ethnic groups. How important should ethnicity be in establishing the bank?
These are only a few of the next generation of ethical and policy issues that stem cell research will encounter. Public discussion of these issues needs to start now, while the science is still young and the debate can be carried on thoughtfully. Recent mishaps with gene therapy should teach us a lesson about the importance of transparency on safety. And our eventual goal must be to make the technology universally available. Justice demands no less.