A group of Chinese researchers from the Institute of Zoology at the Chinese Academy of Sciences have created healthy mice offspring using sperm cells created from stem cells. The offspring were able to reproduce again and create successive generations with no adverse health effects.

The researchers took stem cells from a mouse embryo and bathed them in various chemicals to produce an immature sperm-like cell, which they then exposed to testicular cells and testosterone, along with other sex hormones. The end result was a fully functional sperm cell which they then used to artificially inseminate an egg cell. The process resulted in completely healthy offspring.

The researchers developed the process as a means to treat male infertility, which affects to 15% of couples. The technique has been described as a major piece of work, and due to the authors claims that the germ cells showed correct development along the way, it may be transferable to humans. The team has said they are attempting to pursue the first stage of development in humans already.

Others have warned to remain cautious, saying that independent verification must be made, and that the timeline of cell development is off from previous projections. Additionally there may be complications replicating it in humans as there is known differences in the development of germ cells in mice and humans. The ethical implications of using embryonic stem cells must also be explored.