Healing function of sweat glands declines with age

Credit: University of Michigan Health System

Each injury means a little more as individuals age—more impact and more healing time.

A group of scientists and dermatologists are now looking at the role sweat glands play in how aging skin recovers from wounds. It's a step to better learn about aging skin, in order to better treat—and slow—the process.

Their research, recently published in Aging Cell, compared 18 elderly subjects' skin to 18 young adults' skin, to see how each group healed from skin lesions. The lesions were smaller than the diameter of a pencil eraser, performed under local anesthesia.

"We've identified, for the first time, the cellular mechanisms of altered skin wound repair in elderly patients," says first author Laure Rittié, Ph.D., research assistant professor in the University of Michigan Department of Dermatology.

Beyond the underarm

The researchers had already determined eccrine sweat glands, which are located throughout the body, are important for wound closure. They are major contributors of new cells that replace the cells that were lost due to injury.

In young people, they discovered sweat glands contributed more cells to wound closure than in aged adults. The cells in aged skin weren't as cohesive, either. Fewer cells participating, spaced further apart, means a delay in wound closure and a thinner repaired epidermis in aged versus young skin.

It wasn't that the sweat glands were less active in older people, rather, that the environment in the aging skin had been slowly degraded, making the skin structures less able to support the new cells that were generated.

"This tells us that, beyond the frustrating appearance, skin aging also negatively impacts the ability of the skin to repair itself," Rittié explains.

The differences in young and aged skin healing were clear from the beginning of the healing process. The skin was considered healed when the new growths merged together and the scab fell off the surface.

"These important findings could not have been revealed in animal studies because laboratory animals don't have sweat glands, they don't sweat like we do," notes senior author Gary Fisher, Ph.D., Harry Helfman Professor of Molecular Dermatology in the U-M Department of Dermatology.

Clinical implications

The elderly especially would benefit from better skin healing, and Rittié and her team plan to continue the research with that target.

"Limiting skin damage during the aging process is likely to limit the negative impact of aging on wound repair," she says. "This study teaches us that poor wound healing and wrinkling and sagging that occur in aging skin share similar mechanisms. Chronic sun exposure is an important factor that damages skin structures that normally support sweat glands. This is thus yet another good reason to wear sunscreen!"

Sweat glands play major role in healing human wounds, research shows

Credit: University of Michigan Health System

Turns out the same glands that make you sweat are responsible for another job vital to your health: they help heal wounds.

Human skin is rich with millions of eccrine sweat glands that help your body cool down after a trip to the gym or on a warm day. These same glands, new University of Michigan Health System research shows, also happen to play a key role in providing cells for recovering skin wounds – such as scrapes, burns and ulcers.

The findings were released online ahead of print in the American Journal of Pathology.

"Skin ulcers – including those caused by diabetes or bed sores – and other non-healing wounds remain a tremendous burden on health services and communities around the world," says lead author Laure Rittié, Ph.D., research assistant professor of dermatology at the University of Michigan Medical School.

"Treating chronic wounds costs tens of billions of dollars annually in the United States alone, and this price tag just keeps rising. Something isn't working."

Now, U-M researchers believe they have discovered one of the body's most powerful secret weapons in healing.

"By identifying a key process of wound closure, we can examine drug therapies with a new target in mind: sweat glands, which are very under-studied," Rittié says. "We're hoping this will stimulate research in a promising, new direction."

Previous understanding of wound closure was that new skin cells originate from hair follicles and from intact skin at the edge of the wound. The U-M findings demonstrate that cells arise from beneath the wound, and suggest that human eccrine sweat glands also store an important reservoir of adult stem cells that can quickly be recruited to aid wound healing.

"It may be surprising that it's taken until now to discover the sweat glands' vital role in wound repair," Rittié says. "But there's a good reason why these specific glands are under-studied – eccrine sweat glands are unique to humans and absent in the body skin of laboratory animals that are commonly used for wound healing research.

"We have discovered that humans heal their skin in a very unique way, different from other mammals," Rittié adds. "The regenerative potential of sweat glands has been one of our body's best-kept secrets. Our findings certainly advance our understanding of the normal healing process and will hopefully pave the way for designing better, targeted therapies."