THE birth of Louise Brown, the first child to spring from an egg fertilised outside the body, caused a sensation in 1978. Fertility experts hailed it as a breakthrough while critics attacked IVF as immoral and dangerous. Now, a quarter of a century later, we may be witnessing the start of another revolution in assisted reproduction that will be no less controversial. Last week, researchers in the US reported that they had transformed mouse embryonic stem cells into mature eggs in the lab, and a Japanese team has produced sperm in a similar way (see 鈥淭he next IVF revolution?鈥�).
The full significance of these advances is not yet clear. The teams have not shown that their artificial gametes can develop into healthy mice after fertilisation. Even if they do, the technique may not work for humans: researchers who grow slices of human ovaries in a dish struggle to gather eggs from them, and starting from scratch with unspecialised cells may be even tougher. But then, before Dolly the sheep, most biologists would have said cloning a mammal was impossible. It may just be a matter of time before viable human eggs and sperm can be created in the lab. Governments would do well to consider the implications before this happens.
For starters, a plentiful supply of human eggs would accelerate research in several areas, especially therapeutic cloning. Here the nucleus from a person鈥檚 cell is transferred into a denucleated egg to create a cloned embryo. The idea is that stem cells from that embryo could then be used to treat illnesses in the person who supplied the nucleus. Worryingly, more eggs will also be a boon to those who want to create living clones.
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Making eggs and sperm also has huge potential for helping infertile couples. It would depend on therapeutic cloning to generate embryonic stem cells, something that has yet to be achieved with human cells. But if that does happen, it could enable couples who cannot make their own eggs or sperm to have children who are a mixture of their genes, just like those conceived in the old-fashioned way.
Yet these couples need not be old- fashioned couples. Some eggs in the latest experiments came from male stem cells. If the same can be done in humans, a gay couple could supply both egg and sperm to create their own child. That prospect will no doubt outrage some. It would certainly require a rethink of the laws covering parentage.
But before this ever happens, we need to have a clear picture of the risks to any offspring born from artificially created eggs and sperm. There is good reason to be concerned, as even IVF has yet to be given a clean bill of health. Most studies show that IVF poses no extra risk, but there are exceptions. One Australian study concluded that IVF babies had a 9 per cent risk of major defects such as a hole in the heart, compared with just 4 per cent for babies conceived naturally. Recently, a number of small studies found that IVF children have a higher risk of defects caused by errors in imprinting, the process by which genes in the embryo are switched on or off.
The inability to generate the right pattern of imprinting has thwarted all past attempts to create artificial eggs and sperm. It is also the reason why cloning is so difficult and the rate of abnormalities in clones is so high. Eggs or sperm created with the latest technique may have fewer imprinting problems than cloned cells and artificial gametes made in other ways, but even if this proves to be the case, it is still likely that the rate of birth defects will be higher than in existing IVF.
That raises the question of what constitutes an acceptable level of birth defects for assisted reproduction. Would we tolerate defects in 20 per cent of babies? Or 50 per cent? There are no easy answers, especially as many birth defects are not life-threatening and can be treated.
The biggest danger, as we have seen with reproductive cloning, is that doctors greedy for fame or fortune will race to create the first baby using the new methods. Unregulated use of experimental reproductive techniques is clearly undesirable. But then so is a blanket ban. Many countries have, or plan to introduce, laws against all forms of cloning, which would outlaw the latest techniques, too. Those advocating such laws might ask themselves if they really want to ban a method that might one day let infertile couples have their own biological children, just as if they had been conceived naturally.