Scientists have shown for the first time that sperm created from embryonic stem cells can be used to produce live offspring.

The experiment, carried out by researchers in Britain and Germany using mice, culminated in the births of seven babies. Six of these, whose origins were owed to sperm derived from these "multipurpose" cells, lived to adulthood, according to a press release from the University of Newcastle on Tuesday.

In the research, a team led by professor Karim Nayernia, who was formerly based at Georg-August University in Germany, succeeded in converting stem cells taken from early mouse embryos into "spermatogonial stem cells" (SSCs), and then into functioning sperm.

Nayernia, who is now professor of Stem Cell Biology at Newcastle University, and his team were the first in the world to isolate spermatagonial stem cells. The scientists were also able to show that some of these stem cells, called multi-potent adult germline stem cells (maGSCs), turned into heart, muscle, brain and other cells.

The breakthrough was reported in the academic journal Developmental Cell. The team described how they developed a new strategy for generating mature sperm cells in the laboratory using embryonic stem cells from mice. The researchers then went on to test whether this sperm would function in real life, the press release said.

The researchers implanted the sperm artificially into eggs collected from mice, and showed that the sperm were capable of fertilizing the eggs, which produced living offspring when implanted into surrogate mothers.

Of 210 eggs injected with the lab-reared sperm, 65 began to undergo cell division, resulting in seven live births, with only one of the offspring failing to reach adulthood, the researchers said.

Stem cells have the potential to develop into any tissue type in the body and could therefore be used to develop a wide range of medical therapies.

The breakthrough will help scientists to understand more about how animals produce sperm and the knowledge has potential implications for the treatment of male infertility.

Nayernia was quoted as saying "spermatagonial stem cells are extremely promising and more research is needed to establish their full potential."

From a scientific point of view, the breakthrough has been described as a milestone in understanding how cells produce functioning sperm.