The hair follicle isn't just a hair factory. Researchers have now discovered that the hair follicle is the source of new cells for the skin's outermost layer, the epidermis, which is replenished throughout life. And these cells, according to a new study by researchers at New York University School of Medicine and the University of Pennsylvania School of Medicine, reside in a well-protected area of the follicle, called the "bulge," that lies just underneath the skin.
The new study, led by Tung-Tien Sun, Ph.D., of NYU School of Medicine, and Robert Lavker, Ph.D., of the University of Pennsylvania School of Medicine, is published in the August 18 issue of the journal Cell. Using a novel double-labeling system, the researchers were able to track the path of the progeny of stem cells as they traveled from the bulge into the epidermis of mice, where they settled in as epithelial cells. Epithelial stem cells are primitive progenitor cells that supply the cells needed for replenishing the skin, one of the body's self-renewing tissues. (These cells aren't related to the stem cells found in the bone marrow.)
"We used to think that the hair follicle had its own stem cells, and that the epidermis had its own stem cells," says Dr. Sun, who is the Rudolf L. Baer Professor of Dermatology and Professor of Pharmacology and Urology at NYU School of Medicine. "Now we believe that there aren't two separate entities. Instead, there is only one entity, an ultimate epidermal stem cell that is capable of forming skin or hair." (Despite the great difference in their appearance, hair and skin are closely allied. Hair is composed of a protein called keratin, a specialized product of epithelial cells.)
"This is an important new concept," says Dr. Lavker, Professor of Dermatology, at the University of Pennsylvania School of Medicine. "Our findings suggest that certain types of skin cancer probably arise from epidermal stem cells found in the bulge,
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Contact: Marjorie Shaffer
Marjorie.Shaffer@med.nyu.edu
212-404-3555
New York University Medical Center and School of Medicine
16-Aug-2000