Many couples are faced with the unpleasant choice between not having a child of their own and the risk of passing on a debilitating illness. Yet research into reproductive technologies to reduce the chances of having unhealthy children has been hindered by public view of interfering with the course of life.

Mutations in the DNA of mitochondria – the energy-producing organelles in a cell – are associated with a growing list of diseases, and treatment options are limited to alleviation of symptoms. In theory, the mutation could be picked up by early embryonic screening, but efforts to do so have been of limited value, as little is known about how much mitochondrial damage is required to cause disease.

Now, a paper published online this week by Nature (M. Tachibana et al. Nature doi:10.1038/nature08368; 2009) provides a way to eliminate the problem. This technique involves taking nuclear DNA from one egg cell and transferring it to another egg that has had its nucleus removed. The newly ‘rebuilt’ egg will only contain mitochondria from the new egg cell, leaving behind any defective mitochondria from the parent cell. It can then be used for in vitro fertilization.

But the work presented this week is done in monkeys. Demonstrating that this can be done safely in humans would require research that is controversial – and, in many countries, legal or practically impossible.

A major obstacle is that human embryos would need to be created solely for research, which many feel violates the sanctity of human life. That logic was used by the administration of former US President George Bush to prohibit such studies, and even now the National Institutes of Health and other US agencies cannot fund them.

Nevertheless, this constraint has not prevented research from being funded by non-federal sources, such as the state of California. Nor has it prevented the formation and destruction of embryos during commercial fertility treatments.

The nuclear-transfer process has a more serious obstacle in obtaining the human eggs needed for both donor and recipient cells. The egg-donation process is uncomfortable and somewhat risky, and some bioethicists argue that compensating women who undergo it is a form of coercion.

Egg donation paid for research is prohibited by most state and federal funding agencies in the United States and elsewhere (with the notable exception of New York State, which allows it).

As a result, egg cells are typically only available from women who are willing to give them philanthropically – a comparatively small number, reduced by the fact that women have thousands to donate to fertility clinics. dollars can be found. Thus, research in some areas, such as somatic-cell nuclear transfer, or cloning, has almost slowed.

More states should lead New York, and allow researchers to pay for egg donation. The potential for coercion, although real, is manageable. And the move of technology to the clinic would certainly be faster, and arguably more ethical, if donors were paid (c. Thompson Regen. Med. 2, 203–209; 2007).

Yet another argument raised when such research has been attempted in the past – for example when researchers tried to replenish damaged mitochondrial DNA in one egg with healthy mitochondrial DNA from another – is this. That such a three-parent union is ‘unnatural’.

Yet similar concerns were welcomed by in vitro fertilization when it was pioneered in the 1970s, and the technique is now widely accepted. Blanket sanctions can hinder progress and encourage unethical practices. With proper oversight, research into other fertility techniques has the potential to give more couples the chance to have a healthy baby.

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