Pouillot Anne, Dayan Nava, Polla Ada S, Polla Luigi L, Polla Barbara S
Alchimie Forever Sàrl, Geneva, Switzerland.
J Cosmet Dermatol. 2008 Jun;7(2):143-8. doi: 10.1111/j.1473-2165.2008.00379.x.
The stratum corneum (SC) (i.e., the outermost layer of human skin) is a complex and paradoxical tissue composed of corneocytes and a matrix of intercellular lipids playing an essential role as the skin's protective barrier. The first paradox of SC is its dual nature. It is composed of nondividing (dead) cells embedded in a metabolically active (live) environment whose function is to protect the epidermis and to maintain its integrity. In order to do so, the SC uses various strategies, including enzymatic reactions, colonization by bacterial flora, immune signaling, antimicrobial lipids and peptides, low pH, antioxidants, and natural moisturizing factor(s). The second paradox is that although its biological function is essentially that of a physicochemical barrier, cosmetologists and pharmacists are actively exploring paths for penetration through the SC to allow passage of active molecules and their penetration into the skin. Various pathways of penetration and physicochemical factors facilitating this penetration into the dermis and/or the epidermis have been defined, but the exact mechanisms of penetration of cosmetic ingredients remain elusive. For cosmetologists and pharmacists, the SC represents a major focus of interest whether for basic research or the development of novel topical approaches taking into account the fascinating properties of this complex tissue.
角质层（SC）（即人类皮肤的最外层）是一种复杂且自相矛盾的组织，由角质形成细胞和细胞间脂质基质组成，作为皮肤的保护屏障发挥着至关重要的作用。角质层的第一个矛盾之处在于其双重性质。它由嵌入代谢活跃（有生命）环境中的非分裂（死亡）细胞组成，其功能是保护表皮并维持其完整性。为了实现这一目标，角质层采用了多种策略，包括酶促反应、细菌菌群定植、免疫信号传导、抗菌脂质和肽、低pH值、抗氧化剂以及天然保湿因子。第二个矛盾之处在于，尽管其生物学功能本质上是作为物理化学屏障，但美容师和药剂师正在积极探索通过角质层的渗透途径，以使活性分子能够通过并渗透到皮肤中。已经确定了各种渗透途径以及促进这种渗透进入真皮和/或表皮的物理化学因素，但化妆品成分的确切渗透机制仍然难以捉摸。对于美容师和药剂师来说，角质层无论是对于基础研究还是考虑到这种复杂组织的迷人特性开发新型局部应用方法，都是一个主要的关注焦点。
