Aging-related shift of eccrine sweat glands toward the skin surface due to tangling and rotation of the secretory ducts revealed by digital 3D skin reconstruction.

Background: Sweat gland function deteriorates with aging, leading to loss of heat tolerance. However, it is unclear whether and how the structure of sweat glands changes during aging, because the 3D structure is complex and inaccessible.

Methods: To clarify age-dependent changes in sweat glands, we developed a method for 3D structure analysis of sweat glands by means of X-ray micro-CT observation of human skin specimens followed by 3D digital reconstruction on computer (digital 3D skin).

Results: Comparison of eccrine sweat glands of abdominal skin from young and old subjects showed that the density and volume of sweat glands do not change with aging. In contrast, the depth of the secretory coil from the skin surface is decreased in the aged group. Surprisingly, the secretory ducts appear tortuous or meandering though their length is unchanged. The secretory coils are located at the dermal-adipose layer boundary in both groups, but the thickness of the dermal layer decreases with aging, and the depth of the coils is correlated with the dermal thickness.

Conclusion: Our results suggest that sweat glands twist and rotate with aging to maintain the position of the coil at the dermal-adipose boundary, causing an overall shift toward the skin surface.