Shiseido reports its researchers have uncovered how age-related inflammatory factors (IL-8) damage epidermal stem cells and accelerate cell aging.
As the company explains, IL-8 is a type of waste product collected by lymphatic vessels in the skin. While it has been known that the age-related decrease of lymphatic vessels causes deterioration in the collection of waste product, which results in the accumulation of inflammatory factors in skin, it was unclear how such accumulated inflammatory factors affect epidermal stem cells.
The Study: Skin Rejuvenation and Cell Senescence
Recent work has revealed that IL-8 accumulation causes damage to epidermal stem cells and affects the barrier function of the skin. First, the team examined epidermal stem cell colony-forming ability, which is an index of its self-replication abilities. They cultured IL-8 (or not) in the culture medium and compared the number of colonies formed. This revealed that colony-forming, i.e., cell rejuvenation ability, deteriorates significantly in the group with IL-8.
Then, they examined the expression level of the Lrig1 gene, which is a marker for epidermal stem cells, and found that the gene expression level was significantly reduced when IL-8 was added. This suggested a loss in the stem characteristics of epidermal stem cells.
Furthermore, they selectively stained senescent cells using β-galactosidase staining, in order to verify the effect of IL-8 on cellular senescence. This revealed that the addition of inflammatory factors to epidermal cells increased the number of senescent cells.
Finally, adding an inflammatory factor (IL-8) to the skin model and culturing it for five days showed a decrease in the expression of bleomycin hydrolase, a natural moisturizing factor-producing enzyme, which maintains the skin barrier function. This suggests that IL-8 deteriorates the barrier function of the skin.
The Outcome: Lymphatic Approach to Skin Care
These findings will lead to the development of a new skin care approach that focuses on the functions of lymphatic vessels to care for epidermal stem cells, which play an important role in the rejuvenation of skin cells. The company notes some of the research results will be presented at the 45th Annual Meeting of The Japanese Society for Investigative Dermatology, to be held Dec. 11-13, 2020.