Two kinds of sweat glands are present in the human body. Apocrine sweat glands are located in arm-pits or rectogenital areas and are responsible for “smelly” sweat. Eccrine sweat glands, on the other hand, are distributed all over the human body and produce a non-odorous sweat. The eccrine sweat glands are primarily found in humans and certain primates. They also exist in some other mammals, but are usually restricted to the footpads of non-primate mammals. There is some controversy about the actual purpose of eccrine sweat glands in humans. The functions traditionally ascribed to eccrine sweat glands include promoting grip, generating a protective acid mantle for the skin as well as regulation of temperature or the electrolyte balance.
The recent article “Eccrine Sweat Glands are Major Contributors to Reepithelialization of Human Wounds” published in the American Journal of Pathology by Laure Rittié and colleagues proposes a novel and very interesting function for eccrine sweat glands. In this study, CO2 laser treatment was used to create superficial wounds in human subjects, either on their palm or on their forearms. The researchers performed biopsies during the subsequent days to assess the wound healing process. They observed significant proliferation of cells at the bases of hair follicles (pilosebaceous units) as well as proliferation of cells within the eccrine sweat glands. The outgrowths of cells from these areas merged together to regenerate the skin layer. Wound healing (re-epithelialization) in the palms of hands was primarily driven by cell proliferation of sweat gland cells, because the palms do not contain hair follicles.
The findings suggest that wound healing and regeneration of damaged skin may be an important function of cells that reside within human eccrine sweat glands. The study did not quantify the exact contribution of the sweat glands to the wound healing process or compare it with the contributions of other cell types. It also did not address whether the sweat production itself regulates or facilitates the repair process. This would be an intriguing possibility, because we all know how our palms become sweaty when we are under stress. Is it possible that the eccrine sweat production is a way of preparing the body for potential wounds and the need for repair or regeneration? Is there a way to enhance the wound healing emanating from the eccrine sweat glands? These and other questions will need to be addressed in future studies.
In summary, the work by Rittié and colleagues presents an important new perspective on how sweat glands can participate in wound healing. It is also an important reminder of how some animal models of wound healing may have their limitations when their results are translated to the human setting. Most laboratory animals that are used for wound healing studies do not have eccrine sweat glands. Results derived from such animal wound healing studies may thus not be readily applicable to the human setting and should be interpreted with a grain of sweat (salt).
Image credit: Wikimedia / National Institutes of Health – Anatomy of Skin