Although scientists have succeeded in creating artificial sperm from embryonic stem cells in mice, practical applications in human fertility treatments are likely a long way off.

After these cells, called "spermatogonial stem cells," grew into adult sperm cells, scientists injected them into the eggs of female mice.

The eggs became fertile and were then transplanted into another group of female mice, which gave birth to seven baby mice. All but one of the offspring survived to adulthood.

Ethical Questions

Nevertheless, those six mice had abnormal growth rates, the researchers noted. They were all smaller or larger than control mice. Also, even though they reached adulthood, all died within 5 months. The normal lifespan of mice is several years.

The problems may be due to genetic changes during the imprinting stage, the researchers suggested.

This is the first experiment to create life from artificial sperm, according to Professor Nayernia, who believes the knowledge gained may eventually have applications in the treatment of infertility in men -- though such treatment is years away, at best.

Critics, though, fear this could be the first step toward eliminating the role of men entirely in the process of human reproduction.