To date, few fundamentals have been known about the most common gland in the body, the sweat glands that are essential to controlling body temperature, allowing humans to live in the world’s diverse climates. Now, in a tour de force, researchers at The Rockefeller University and the Howard Hughes Medical Institute have identified, in mice, the stem cell from which sweat glands initially develop as well as stem cells that regenerate adult sweat glands.
In their study, published in Cell, the scientists devised a strategy to purify and molecularly characterize the different kinds of stem cell populations that make up the complex sweat duct and glands of the skin. With this information in hand, they studied how these different populations of stem cells respond to normal tissue homeostasis and to different types of skin injuries, and how the sweat glands differ from their close cousins, the mammary glands.
“Mammary gland stem cells respond to hormonal induction by greatly expanding glandular tissue to increase milk production,” explains Elaine Fuchs, Rebecca C. Lancefield Professor at Rockefeller and an investigator at the Howard Hughes Medical Institute. “In contrast, during a marathon race, sweat gland stem cells remain largely dormant, and glandular output rather than tissue expansion accounts for the 3 liters of sweat our body needs. These fascinating differences in stem cell activity and tissue production are likely at the root why breast cancers are so frequent, while sweat gland cancers are rare.” Their findings might also help in the future to improve treatments for burn patients and to develop topical treatments for people who sweat too much, or too little.
“For now, the study represents a baby step towards these clinical goals, but a giant leap forward in our understanding of sweat glands,” says the study’s lead author, Catherine P. Lu, a postdoctoral researcher in Fuchs’s Laboratory of Mammalian Cell Biology and Development.
Each human has millions of sweat glands but they have rarely been extensively studied, possibly due to the difficulty of gathering enough of the tiny organs to research in a lab, says Lu. The mouse is traditionally used as a model for human sweat gland studies, so in this project, Lu and colleagues laboriously extracted sweat glands from the tiny paw pads of mice, the only place they are found in these and most other mammals.
The research team sought to discover whether the different cells that make up the sweat gland and duct contained stem (progenitor) cells, which can help repair damaged adult glands. “We didn’t know if sweat stem cells exist at all, and if they do, where they are and how they behave,” she says. The last major studies on proliferative potential within sweat glands and sweat ducts were conducted in the early 1950s before modern biomedical techniques were used to understand fundamental bioscience.