Science seemed to blur into science fiction this week with the news that my colleagues in Newcastle and I were hoping to get approval for a half-cow, half-human embryo. This prompted images of hybrid animals and shock-horror headlines.

It is understandable that the prospect of blurring the species line may make some people uneasy. However, we are not mad scientists trying to play God, just scientists seeking a solution to the problem of creating cloned embryonic stem cells by “therapeutic cloning”. This, we hope, will lead to new treatments for neurological disorders such as Alzheimer’s and Parkinson’s diseases. To achieve this, we would need a lot of human eggs to produce the embryos needed to achieve stem cells. At the moment, we have an egg shortage.

Embryonic stem cells — cells that have the potential to develop into any cell of the body — can be generated only from human embryos. We normally need sperm to fertilise an egg, thus ultimately creating an embryo, from which we can extract the stem cells. What we at King’s College London and the University of Newcastle applied for doesn’t lie in the realm of Frankenstein, but is a standard procedure (this was the technique used to make Dolly the sheep).

Take an egg (a cow’s in this case), remove all the DNA, so you effectively have an empty shell. Put the DNA you want to clone (a human’s) into the egg. This then grows into an embryo. However, as the DNA of this embryo is almost entirely human now, the embryo would be a human embryo, not a mixed cow-human creation.

This research may also have important implications for organ repair. Cloned stem cells could replace the damaged cells. In a study announced this week on heart attack patients, the stem cells will be extracted from the patients’ bone marrow and injected straight into the heart, where it is hoped that they will then help to repair the organ.

My group at King’s College London is interested in creating cloned human embryonic stem cell lines from individuals with genetic forms of diseases, such as Alzheimer’s and spinal muscular atrophy.

Although to some the thought of using an animal egg may seem gruesome and unnecessary, it is the best solution that we can come up with for the egg shortage in cloning research. The Human Fertility and Embryology Authority (HFEA) does not permit egg donation for research purposes. At the moment, our only source are eggs that fail to fertilise in fertility treatment, and such eggs are hard to use.

Although the HFEA has recently allowed one centre to offer women a reduction in the cost of fertility treatment if they donate half of their eggs for cloning, I am opposed to young women donating eggs for money. I do not feel it is appropriate to encourage women to undergo a risky and invasive procedure for which they receive no direct medical benefit and where most of the donated eggs are wasted.

What we really need for this procedure is a surrogate egg — hence the cows. These animals and other domesticated livestock that are already killed by the food industry for their meat can provide a large pool of eggs. We can use these to improve the efficiency of the cloning procedure, which at the moment is low, and to generate human cell lines, which we believe will accelerate greater understanding of devastating neuro-degenerative disorders, and as an important new cellular tool to develop new and important therapies.

Whether or not our collective applications to the HFEA will be approved remains to be seen, but what is certain is that if we want future treatments for today’s diseases, a better source of eggs needs to be found.

Dr Stephen Minger is the director of the stem cell biology laboratory at King's College London. Mark Henderson is away