Mouse births from stem cell sperm
In the UK around 1 in 10 men are infertile, often because of low sperm counts. A new experimental technique may one day help infertile men produce sperm.
For the first time healthy and fertile offspring have been created using sperm made from mouse embryonic stem cells. The technique involved implanting 'programmed' cells into infertile mice where they developed into sperm.
Scientists extracted stem cells from mouse embryos. These cells have the ability to turn into any type of adult cell, including the germ cells that produce sperm and eggs. By analysing the genes of cells developing in a normal embryo the researchers discovered the conditions needed to turn stem cells into primordial germ cells (cells capable of turning into germ cells). When these cells were implanted into the testes of mice lacking germ cells, sperm production began in three out of six cases.
To demonstrate that the sperm were healthy and functional the researchers extracted sperm from the mice and used it to fertilise eggs in the laboratory. The resulting embryos were then implanted into female mice where they grew into healthy and fertile mouse pups.
The researchers then repeated the technique using induced pluripotent stem cells. These are adult mouse cells that have been turned back into stem cells. These could also be turned into primordial germ cells and implanted into mouse testes. However, this method only resulted in sperm production in one of six mice and some of the offspring died prematurely.
Watch our video about how mice are used to investigate reproductive disorders here.