Artificial Sperm Created

Scientists have raised hopes of an end to male infertility after producing mice using artificial sperm. ARTIFICIAL sperm have been used to create living animals for the first time, in an experiment that promises an end to male infertility.

Scientists have fertilised mouse eggs with sperm grown from embryonic stem (ES) cells to produce seven pups, proving that working reproductive cells can be made in the laboratory. The births provide the strongest evidence yet that it will be possible eventually to use stem cells to treat infertile men who can make no sperm of their own.

Other experiments have suggested that artificial eggs can be made from female embryos, raising similar hopes for infertile women, though no offspring have been born. In the longer term, it may be possible to produce sperm from female stem cells, and eggs from male ones, allowing homosexual couples to have children that bear the genes of both parents. In theory, a single person might even provide both the eggs and sperm needed to create an embryo.

The creation of “male eggs” and “female sperm”, however, faces difficult technical barriers, as embryos require genetic material from both a mother and a father in order to develop normally.

The immediate benefit of the research will be to deepen understanding of how mature sperm are formed, improving treatments for male infertility. One promising idea is to remove tissue from the testes, culture immature sperm in the laboratory and then transfer them back to the patient.

Further in the future, it could become possible to clone embryos that carry fertility patients’ genes, which could be grown into artifical sperm or eggs that allow them to have their own genetic children.

Even if cloning proves impractical, the technology should solve the shortage of donated sperm and eggs.

The study, which was published yesterday in the journal Developmental Cell, was led by Karim Nayernia, who has recently joined the Newcastle-Durham Institute for Stem Cell Biology and Regenerative Medicine from Georg-August University in Göttingen, Germany.

His team first created male mouse embryos, which were allowed to develop for a few days until they became small balls of cells known as blastocysts. They then identified spermatogonial stem cells (SSCs), which will go on to form sperm, and removed them for culture. Those that formed sperm were picked out and injected into mouse eggs, with the resulting embryos placed in the wombs of surrogate mothers.

Fertilisation was very inefficient: hundreds of eggs were injected, but only about 50 developed as far as two-cell embryos, while only seven were carried to term. One of the pups died in infancy and all were dead within five months, compared with a normal lifespan of about two years.

However, the limited success still proves the principle that they can lead to live births.

“This is a problem we will have to solve before human trials, but it is a very important result from a biological viewpoint,” Professor Nayernia said. “We have a model for studying how life begins.”

A team at the University of Sheffield has already established that it is possible to grow human sperm from ES cells, though no attempt has been made to use them to fertilise eggs. Others in America and Japan have also shown that mouse eggs can be made from stem cells and fertilised, though no pups have been born.

The Times