HAIR follicles make more than just hair. The tiny cavities from which they grow are also the source of skin cells, say Henry Sun of New York University and Robert Lavker of the University of Pennsylvania in Philadelphia.
The researchers tracked stem cells in follicles by injecting mice with dyes. They found that a large proportion of the cells crawl upwards into the epidermis, where they form the epithelial cells that make up the outer layer of the skin. The fact that the source of these stem cells is near the skin's surface may explain how some skin cancers and diseases arise, says Sun. "The cells are within easy reach of chemical carcinogens."
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