Spanish scientists have created human sperm from skin cells.

A team at the Valencian Infertility Institute - Spain's first medical institution dedicated solely to assisted reproduction – say the development could lead to a treatment for infertility.

“What to do when someone who wants to have a child lacks gametes?.. this is the problem we want to address,” says Dr Carlos Simon, the institute’s scientific director.

The project builds on the work of Japan's Shinya Yamanaka and Britain's John Gordon, who shared a Nobel prize in 2012 after they discovered a way to transform adult cells back into stem cells.

Dr Simon’s used similar techniques to reprogram mature skin cells by injecting them with a cocktail of genetic material needed to create gametes.

This regressed the skin cell into a germ cell, which can develop into sperm or an egg.

However, sperm created this was does not have the ability to fertilise.

“This is a sperm but it needs a further maturation phase to become a gamete. This is just the beginning,” Dr Simon said.

Chinese researchers earlier this year announced they had fertilised eggs and grown mice from artificial sperm.

“With the human species we must do much more testing because we are talking about the birth of a child,” Dr Simon said.

There are also some legal constraints to take into account, since the creation of artificial embryos is illegal in many countries.

“We are talking about a long process,” Dr Simon said.

The full study is accessible here. [http://www.nature.com/articles/srep24956]