Sperm Made from Human Bone Marrow

Scientists from the Universities of Göttingen and Münster and the Medical School of Hannover claim to have successfully made spermatogonia from adult stem cells. The stem cells, which were isolated from the bone marrow, would have normally differentiated into one of the three types of muscle cells. Instead, the scientists induced transdifferentiation into immature sperm cells. These spermatogonia were then implanted in mice testes.
The next step for the scientists is to get the spermatogonia to progress to mature sperm cells, a process which could take three to five years of experiments. The researchers hope to one day be able to treat male infertility, especially that caused by chemotherapy.
Other scientists warn not to over-interpret this data; transdifferentiation achieved with other types of cells has been difficult to reproduce once subjected to rigorous testing. The discovery, however, is still a step in the right direction.
http://news.bbc.co.uk/2/hi/health/6547675.stm