Philadelphia, PA -- Researchers at the University of Pennsylvania School of Medicine have isolated stem cells responsible for hair follicle growth. The findings, published in the April issue of Nature Biotechnology, may serve as the foundation for new hair loss and skin grafting treatments.

Hair grows from cells located at the base of the hair follicle. Hair follicles continuously cycle through growth, rest, and re-growth phases. In many people with hair loss, however, the follicles do not cycle correctly, with a growing number of abnormal follicles entering longer resting phases and producing only tiny invisible hairs.

Penn researchers suspected that stem cells located within the follicle bulge were responsible for hair growth. To test their theory, they used sophisticated cell labeling techniques to track the decedents of the stem cells during normal hair growth and isolate them in adult mice. They transplanted a slurry of these cells into the skin of a different set of adult mice with no immune systems. (The absence of an immune system prevented the mice from rejecting the stem cell transplant.)

Within four weeks, the transplanted cells made new hair follicles that produced new hair. "Now that we can isolate stem cells involved in hair growth, we can develop targets for manipulating hair growth," says study principal investigator George Cotsarelis, MD, Director of the Penn Hair and Scalp Clinic and Assistant Professor of Dermatology. Penn researchers hope to one day isolate stem cells in an adult scalp and transplant those cells to other areas of the scalp, generating new follicles and hair growth. Using the stem cell transplant as a treatment for hair loss, however, is at least 10 years away, says Cotsarelis.

The findings have implications not only for hair growth, but also for burn treatments. "The cells that we have isolated not only make hair follicles, but also can make other skin cells," says Cotsarelis. "These stem cells are there for your lifetime and have a huge capacity to proliferate and regenerate." Current skin grafting treatments fail to generate hair growth and often lead to unsightly scars. One day, doctors may be able to isolate and use stem cells in skin grafts for burn patients, generating better grafts with hairs.

This story has been adapted from a news release issued by University Of Pennsylvania Medical Center.

Everyone has bad hair days. For 30 million men in the United States, roughly 40 percent of those over 35, every day is a no hair day. The good news is that thanks to new research, baldness may be fading away.

Researchers from the Howard Hughes Institute at the University of Chicago have induced hair follicle formation in the mature skin cells of mice. Follicle formation is a once-in-a-lifetime event that ordinarily happens only during early embryogenesis.

Their findings, reported in the November 25 issue of Cell, indicate that a molecule called beta-catenin may be the long sought message that instructs embryonic cells to become hair follicles, suggesting possible treatments for premature baldness.

"Beta-catenin can cause adult epithelial cells to revert to an embryonic-like state where they have the ability to choose to become a hair follicle," says Elaine Fuchs, Amgen Professor in the Departments of Molecular Genetics and Cell Biology, Howard Hughes Investigator, and lead author of the paper. “This is exciting because current treatments for baldness only work if there are living follicles left, or if the patient undergoes hair transplant surgery. Our research shows that new follicles can be created from adult skin cells if certain molecular players are induced to act.

Beta-catenin performs two very different functions. In adult epithelial cells, it participates in binding neighboring cells together to facilitate cell-cell communication. But during embryogenesis, beta-catenin appears to have another role: it reacts with a molecule called LEF-1, which is expressed only in cells that will eventually become hair follicles. Together, beta-catenin and LEF-1 form a transcription factor that binds to the cell’s DNA and activates the genes that instruct the cell to become a hair follicle.

Uri Gat, a postdoctoral fellow in Fuchs’s lab, created mice that constantly produced a stabilized form of beta-catenin in their skin. (Normally any excess beta-catenin that is not needed for cell-cell adhesion is quickly degraded.) "The process caused some epidermal cells to make the partner molecule, LEF-1," explains Fuchs. “Wherever both stabilized beta-catenin and LEF-1 were present in an epithelial cell, a new hair follicle formed. If we can induce those two partners at the right time, new hair could be formed in places where it has been lost.

The genetically engineered mice were exceptionally hairy. In some mice, most skin cells became hair follicles.

Unlike in embryogenesis, however, the genetically engineered skin of the transgenic mice made an endless supply of beta-catenin and benign follicle tumors formed.

"This is a case of too much of a good thing leading to a bad thing," says Fuchs. She cautions that the use of these exciting findings will still need more work before hair growth can be induced without danger of unwanted side-effects. "If we can find a way to transiently express beta-catenin in these skin cells, just until new follicles are established, and then turn it off, we may be able to prevent tumor formation and still allow hair follicles to form," says Fuchs. The flip side of this, she says, is that it is also a potential tool to stop unwanted hair growth by inhibiting the pathway.

It could also have applications in the agricultural industry, for example to engineer sheep with denser wool or thicker skin, Fuchs explains.