Mouse testes show stem cell promise

German researchers have isolated cells from adult mouse testicles that share some of the characteristics of embryonic stem cells (ES cells). The team isolated stem cells that normally grow into sperm, and coaxed them into producing many different types of body cell. The researchers, based at the Georg-August-University of Gottingen, published their findings early online in the journal Nature. The discovery may eventually lead to tailor-made stem cells that could be used to treat diseases such as diabetes and Parkinson's disease - in men at least. However, other scientists caution that stem cells from human testes might not behave in the same way as their mouse counterparts.  

The ongoing controversy surrounding research into human ES cells in Germany, where such work is banned, and many other countries, has lead several groups to seek alternative sources of cells that can potentially develop into a wide range of different tissues. Although previous research has shown that germline stem cells from embryos and newborn mice are almost as versatile as ES cells, this is the first time that scientists have investigated the potential of adult spermatogonial stem cells (SSCs) - the cells that grow into sperm.

The researchers used transgenic mice in which the SSCs were permanently 'tagged' with a fluorescent protein, to enable them to isolate the elusive cells from mouse testes. They then grew the cells in the laboratory, and found that some of them resembled ES cells. These cells, which they dubbed multipotent adult germline stem cells (maGSCs), were able to grow into several different types of body cell - including heart, brain, liver and skin. The scientists also found that the maGSCs were able to form different tissues and organs when injected into mouse embryos. Team leader Gerd Hasenfuss told New Scientist magazine that his team is now taking testicle tissue samples from patients already undergoing operations, to try and obtain human versions of the stem cells.

Professor Chris Higgins, director of the UK's Medical Research Council Clinical Sciences Centre, welcomed the discovery, but stressed that much more research is needed to understand the similarities and differences between maGSC and ES cells. Stem cell researcher Dr Stephen Minger called the findings 'pretty amazing', but added that 'we would need to replicate this in humans, just because it works in mice doesn't mean it will also work in people'. Professor Harry Moore, of the University of Sheffield, echoed these concerns, pointing out that there are a number of key differences between mice and human testes cells.

If these hurdles can be overcome, then men affected by diseases such as Parkinson's disease could one day be treated with stem cells isolated from their own testes. Co-author Wolfgang Engel says that recent research suggesting the existence of ovary stem cells could lead to similar cell-based therapies for women. 'I think it will be possible to find stem cells there', he told Nature.