Testicles could be new source of stem cells

Scientists from Germany and the UK have found a new source of stem cells that could be as good as embryonic stem cells for researching and developing treatments for a range of serious diseases, but without the ethical problems of embryonic stem cells; the source is routine biopsies of men’s testicles.

The discovery was the work of researchers from the Universities of Tübingen and Cologne in Germany, and King’s College, London, and was published 8 October in the online issue of Nature. The lead author was Professor Thomas Skutella, who leads an experimental embryology group at Tübingen University.

Stem cells from embryos have the potential to become any cell in the body, after all, a whole person grows from a single fertilised egg. But getting stem cells from embryos is fraught with ethical problems since it involves the destruction of embryos.

For some time now scientists have been working to find alternative ways to make stem cells with the same ability to become any cell in the body as the embryonic stem cell. One such method that has been showing great promise recently is the induced pluripotent stem cell, or iPS cell. By taking a normal cell, such as a skin cell and inserting certain genes into its DNA, scientists have been able to reprogram the cell to regress to an earlier form when it still had the potential to become virtually any other cell of the body.

However, Skutella and colleagues had a hunch that there was another source of stem cells, ones that did not need to have genes inserted into their DNA to make them into cells that produce other cells, because they do that already: the sperm producing cells inside adult male testicles.

They succeeded in harvesting stable stem cells from spermatogonial (sperm producing) cells taken from routine tissue biopsies of the testes of 22 adult male humans. They showed that the cells could be coaxed into regressing to become cells from all three germ layers that form in the very early stages of a new human embryo. This was done by culturing them in the same way used to make embryonic stem cells differentiate.

The researchers concluded that:

"The generation of human adult germline stem cells from testicular biopsies may provide simple and non-controversial access to individual cell-based therapy without the ethical and immunological problems associated with human embryonic stem cells."

Stem cells are the new hope for treatment development because they carry the potential of personalized therapy – using a person’s own cells to create stem cells that can then repair and replace damaged tissue, such as in Parkinson’s, Alzheimer’s and cancers. This way the big problem of immune system rejection is overcome because the implants have the same DNA as the host.

In this case however, using stem cells from male testes, the treatment would only work on men.

Many scientists are of the view that regardless of the alternatives that are found, embryonic stem cells are still the best, they are the "gold standard" of pluripotency, and we will need them for research and treatment development for some time to come.

(Source: Nature: University of Tübingen: October 2008)