Much of the controversy surrounding research on stem cells hinges on the source of the cells--particularly whether they come from embryonic sources or adult ones. Now research published online by the Proceedings of the National Academy of Sciences provides new insight into the abilities of stem cells taken from hair follicles. The results indicate that these adult stem cells can develop into neurons.

Inside a hair follicle is a small bulge that houses stem cells. As hair follicles cycle through growth and rest periods, these stem cells periodically differentiate into new follicle cells. Yasuyuki Amoh of AntiCancer, Inc. and his colleagues isolated stem cells from the whiskers of mice and tested their ability to become more sophisticated cell types. The researchers cultured the cells and after one week discovered that they had changed into neurons and two other cell types--known as astrocytes and oligodendrocytes--that are associated with neurons. According to the report, when left for longer periods lasting weeks or months, the stem cells could differentiate into a variety of cell types, including skin and muscle cells.

The scientists next transplanted the stem cells under the skin of living mice and found that they could also differentiate under those conditions. The finding that the stem cells could form neurons and other cell types after transplantation in vivo as well as in a petri dish, the authors conclude, "raises possibilities of their therapeutic applications."