Sperm From Stem Cells?

Infertility is a problem that affects many couples and that may lead to psychological impacts. Men afflicted by certain inherited genetic anomalies produce only very few sperm cell or no sperm cells at all.

Scientists in the US have just made a huge step towards helping these men: they have created sperm precursor cells from human skin cells.
Induced pluripotent stem cells were produced from the skin cells of three men who cannot produce any sperm due to a genetic mutation, and from two healthy men. These stem cells were injected into the testes of mice, where they transformed into sperm-precursor cells. However, they did not develop into mature sperm cells, probably because the genetic difference between humans and mice is too big.
While the stem cells from the healthy men performed better, the fact that the infertile men's stem cells could produce any sperm cells at all was a huge breakthrough.

Now scientists hope to replicate this study with animals that are more closely related to humans, in order to achieve better results. There is just one big problem: the stem cells caused tumors in the mice. This issue will probably have to be solved before more trials can be conducted.

Nevertheless, this new study provides a model that can help scientists to understand the earliest steps of human reproduction and the biological problems infertile men have to deal with. It also gives hope to men who became infertile due to cancer treatments.

Sources:
http://www.cell.com/cell-reports/abstract/S2211-1247(14)00264-2
http://www.iflscience.com/health-and-medicine/scientists-generate-sperm-precursors-skin-cells-infertile-men
http://med.stanford.edu/ism/2014/may/germ-cell.html
http://www.montana.edu/news/12625/reijo-pera-and-team-stem-cell-research-holds-promise-for-male-infertility
http://www.livescience.com/45278-stem-cells-sperm-production.html