File photo: By combining two types of stem cells – special cells which have the ability to develop into different kinds of tissue – from mice, researchers were able to grow a very early stage embryo. Picture: Wikimedia Commons

London - Scientists have taken a major step towards creating life in the laboratory without using sperm or eggs.

By combining two types of stem cells – special cells which have the ability to develop into different kinds of tissue – from mice, researchers were able to grow a very early stage embryo.

When the collection of fewer than 100 cells, just days old, was then implanted into a womb, it triggered chemical changes that a normal pregnancy would, although it was not able to develop any further.

Lead researcher Professor Nicolas Rivron, of Maastricht University in the Netherlands, said their breakthrough could eventually create an unlimited supply of identical early-stage embryos – hollow balls of cells known as blastocysts – that could be used for infertility research and testing the effects of new medical treatments.

He added: "This is the first time we have created structures in the lab from stem cells which have the potential to form the whole organism – the baby, placenta and yolk sac. Embryos are very precious, and it is impossible to test drugs on them as you don’t have the numbers. With artificial embryos you can open up the numbers. This will allow screening of medicines in the future."

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Researchers say that within three years the technique could result in a viable mouse embryo – one that could fully develop into a baby mouse.

But experts warn that if the technique could be replicated in people – which Professor Rivron told the Daily Mail may well be possible within two decades – it could lead to the creation of an army of human clones.

Professor Rivron added: "I do not believe in using blastocysts for human reproduction. This is ethically very questionable. Human cloning is totally forbidden."

It is hoped the research, published in the journal Nature, will shed light on one of the biggest causes of infertility – embryos failing to implant in the womb.

However, at the moment the scientists do not know why their own newly created blastocysts are not developing further. The ones they have managed to create are equivalent to just 3.5 days old.

Professor Rivron said: "We actually don’t know. They look extremely similar to normal blastocysts, and generate many cell types. However, the cells are not properly organised – they look like a disorganised embryo."