Stem Cell, cell at an early stage of development that has the potential to turn into many different types of tissue. The stem cells of an embryo have the capacity to produce cells of all types, but stem cells of more limited capacity for differentiation are also found in various tissues in adults. Stem cells can in principle provide replacements for tissues damaged by age, trauma, or disease, and they have thus become a subject of intensive research and great public interest.
When a stem cell divides, each daughter cell has the potential to either remain a stem cell or differentiate to a more specialized cell type. In the future, many scientists believe that stem cells could be used to repair tissues damaged by trauma or disease and treat conditions such as Type 1 diabetes, Parkinson’s disease, Alzheimer’s disease, arthritis, heart disease, and spinal cord damage.
The use of stem cells is very controversial, especially when the cells are taken from laboratory-created embryos. Opponents argue that any embryo has the potential to become a human being, so it is morally wrong to experiment on them. Against this, supporters of stem cell research point out that the embryos used are typically only four or five days old—little more than a small ball of cells—and incapable of feeling. They also point to the immense potential for the relief of suffering presented by stem cell therapy. Legislation in the United Kingdom now permits the use of foetal tissue up to 14 days old for production of stem cells. Future technical developments should make it possible to produce stem cells from even fully differentiated adult cells, and to grow these in large numbers in tissue culture, thereby avoiding the need to use human foetal material.
Events have moved very rapidly since 1997, when Dolly’s birth was announced. Several other species have been cloned by nuclear transfer, including mice (which had proved so difficult in the early 1980s); cattle; rats; and pigs, which are of immense potential importance primarily in medicine, not least as possible sources of donor organs, or xenotransplants (see Medical Transplantation).
However, interest has not focused on the mere replication of elite animals, as in 1980s America. Instead, different aspects of cloning science have been developed in different ways. Among the most promising is tissue repair, which combines both of the main conceptual threads: the retention of totipotency (or at least some measure of versatility); and the reprogramming of differentiated cells. Thus, research that was initially quite separate from the cloning work has shown that if cells derived from embryos are injected into damaged brains in rats, then they can develop into nerve cells and effect some repair and mental improvement. There is now some evidence that this can also work in humans suffering from Alzheimer’s disease, for example. But the embryonic tissue does not of course come from the patient himself or herself, which means that it risks immune rejection. At least, the brain itself tends to tolerate foreign material, but rejection is certainly a risk in other tissues such as the pancreas, which might benefit from tissue replacement in diabetes. The immediate aim is, then, to transfer nuclei from the cells of the patient himself or herself into embryo cells so that they assume the character of the patient’s own cells, and then use these reconstructed cells for tissue replacement. Clearly the use of embryonic tissue raises ethical problems, but the principle is emerging, at least in Britain, that it is permissible to take cells from embryos up to 14 days old, when the cells are still not differentiated, or fully integrated to form a new individual. Modern fertility clinics produce many more embryos by in vitro fertilization (IVF) than will ever be implanted. To make use of them is of course a compromise. Given their potentiality to become human beings, there is a special sensitivity attached to their use; yet the argument that their use will bring relief to those suffering from various profoundly debilitating conditions is a strong one.
All such dilemmas will surely be solved, however, when biologists know exactly how the cytoplasm of recipient eggs manages to reprogramme donor nuclei in G0. What the egg can do could one day be replicated in the laboratory. Then, for example, it should be possible to take skin cells from a patient with diabetes, culture them, reprogramme them so that they become totipotent again, and re-implant them in the damaged organ. Ultimately it might even be possible, by such reprogramming, to culture the patient’s own cells so that they recreate entire organs: the ultimate organ transplant. Whether or not such a procedure proves viable, research in this direction appears certain to be instructive and fruitful.
It has also now been shown that cells can be transformed genetically in culture, and then be used to make whole new transformed animals by nuclear transfer. Polly was merely the first. But the wider significance of cloning combined with genetic engineering can hardly be overestimated. In the days when DNA could only be added to embryos, genetic engineering of animals was very hit-and-miss, and it was possible only to add genes. Now that cells can be transformed in culture the “engineers” can manipulate them as freely as if they were bacteria, either adding genes or removing them (the “knockout gene”), or changing their nature. Then the transformed cells can be cloned into entire animals by nuclear transfer. In short, through cloning technology, genetic engineering of animals has come of age. Genomics—discovering which genes do what—completes the picture.
The realities of modern research are very far from the various nightmare scenarios of cloned dictators, or entire substitute people grown simply to supply “spare parts”, that were mooted after Dolly. Nevertheless, as both publicly funded research projects and the large commercial biotechnology and pharmaceutical companies rapidly advance knowledge and applications, often following different priorities, giving different weights to ethical precepts, and working in competition with each other, there are areas of concern.
Although many scientists are now developing aspects of cloning technology, relatively few want simply to make clones that are replicas of existing creatures. But some do, including some who are already seeking, or offering, cloning of human beings. By 2001, doctors both in the United States and in Europe were actively preparing to offer cloning to couples unable to reproduce by other means, though many critics worldwide felt that these ventures were at least premature. By the same token, some medical scientists are now using the new techniques of genetic engineering to correct serious genetic diseases such as cystic fibrosis. Others dream of going further: introducing genes into unborn children that would (with luck) make them more athletic, or beautiful, or intelligent, the so-called “designer baby”. Many apparently see nothing wrong with this, seeing it in the same light as spending considerable sums of money on private schooling and college fees.
Others, however, perceive huge ethical problems. In addition to the possibility of such choices being limited to the wealthy few, the very nature of such genetic alteration beyond the realms of preventing serious disease raises questions of responsibility. Although everyone chooses his or her mate carefully, hoping (albeit unconsciously) to produce healthy, bright children, the mixing of genes during sexual reproduction ensures that each child is genetically unique: a true individual. Thus the parents’ control over their children’s genes is very limited. But a parent who clones a child, or transforms him or her genetically, is prescribing the child’s genes. That at the very least could be regarded as being extraordinarily presumptuous. Cloned or transformed children might well feel that their individuality had been forever compromised. It is a widely accepted ethical principle, too, that no one can be held responsible for things they have no control over, so although we may (irrationally) feel guilty if things go awry with our children’s genes, we cannot reasonably be held responsible. But parents who prescribe their children’s genes must take responsibility for all setbacks.
In considering the “designer baby” scenario, it is also important to remember that no technology is ever precisely predictable, and our current understanding of genetic engineering is very limited. Even to correct a simple genetic defect is innately risky, but the risk can be worth taking if the disease is severe. To tinker with a child who is already healthy in the hope of adding a few points of IQ, or a few inches in height, seems unjustifiable. Yet no mistake at all would be acceptable. The genetic designers of babies would have to be able to offer certainty in the outcomes or disaster could result—anything from late abortion to serious abnormalities. But no technology has ever, or can ever, promise 100 per cent success.
The perennial challenge is to frame laws that will release the new technologies for the good of humanity and our fellow creatures, while forestalling the many possible abuses. The greater challenge is to promote the sensibility that would make such laws unnecessary.