What is rough skin?

Rough skin, a frequently encountered skin problem in women, is defined as "a condition in which the dried stratum corneum on the skin surface causes a rough skin texture and eventually scaling". Rough skin is generally treated by supplementing it with what it lacks: moisturizing components or intercellular lipid. However, a solution to tackle the fundamental factor that causes rough skin is yet to be discovered. Shiseido has been conducting studies to elucidate the mostly unknown mechanism of development of rough skin and to develop new ingredients with superior efficacies.

Rough skin

Discovery of new rough skin mechanism

Shiseido discovered that the first reaction that triggers the development of rough skin occurs in the stratum corneum, the outermost layer of the skin. Shiseido has also identified the key player in this first reaction, namely, UPA protein present in the stratum corneum. UPA protein is activated by dryness or other stresses, such as physical damage, and the damage produced by it is subsequently transferred from the stratum corneum into the deeper epidermis to damage the entire epidermis and triggers the development of rough skin.

When UPA protein is activated by stress, the green fluorescence in the stratum corneum (between the dotted lines) disappears, and the stratum corneum appears as a black belt.

UPA protein: a protein that controls keratinocyte proliferation and differentiation. Its overexpression triggers the development of rough skin.

Development of the novel active ingredient "SEBLAEN(R)"

Based on the newly gained knowledge, Shiseido started a new study on rough skin in which an active ingredient that suppresses activation of UPA protein in the stratum corneum of the skin and shows excellent efficacy against rough skin was successfully developed. The ingredient was named "SEBLAEN(R)" (t-cycloamino acid methylamide derivative). SEBLAEN(R) was patented in Japan, the U.S, EU, Taiwan and Korea, and was approved by the Ministry of Health, Labour and Welfare of Japan as an active ingredient of a quasi-drug for the treatment of rough/chapped skin in 2004.

Molecular structure of SEBLAEN(R)

Improvement of rough skin by CE care

A process called "epidermal turnover" occurs continually in the epidermis; newly generated cells in the basal layer move upward to the spinous cell layer, granular layer, stratum corneum, and then slough off as dead skin cells. The stratum corneum has important functions, including the "water holding function" to maintain adequate skin moisture and the "barrier function" to prevent water evaporation from the skin and also prevent the entry into the skin of foreign substances from the environment. In cases with rough skin, the epidermal turnover becomes irregular, resulting in impaired function of the stratum corneum.

Process of CE maturation (diagram)

The cornified envelope (CE) is a membrane-like structure of proteins that covers corneocytes. It plays an important role in the barrier function of the skin. Using a proprietary CE maturity evaluation method, Shiseido identified a large amount of immature CE on facial skin with impaired barrier function, revealing the association between maturation of the CE and the barrier function of the stratum corneum, which are impaired in rough skin.

Shiseido developed an ingredient that acts on the stratum corneum and promotes CE maturation. Continuous use of a skin cream containing this ingredient promotes CE maturation, improves the skin barrier function and prevents the development of rough skin.

A large amount of immature CE is seen in skin with impaired barrier function.