Skin appearance and functionality are affected by a complex combination of factors including both genetic, i.e. intrinsic, and actinic, i.e. extrinsic or environmental. Indeed, genetic and actinic factors act together to modulate the expression of key genes involved in skin homeostasis. Intrinsic aging is genetically regulated and follows a chronological clock inside of cells, while environmental factors such as UV exposure, humidity and air pollutants are responsible for actinic aging. Together, genetic and actinic aging target important metabolic pathways in skin cells that trigger the signs of aging such as skin roughness and wrinkling.
At a molecular level, it has been demonstrated that collagen synthesis is reduced in aged skin cells and in cells damaged by UV radiation.1 Similarly, the expression of various matrix metalloproteases (MMPs), which cause the degradation of collagen fibers and other skin fibrillar components, is upregulated in aged cells as well as in cells exposed to UV, infrared radiation or excessive heat.2, 3 Furthermore, reactive oxygen species are molecular agents implicated in the deleterious effects of both intrinsic and extrinsic aging.1, 4
The skin barrier also plays important roles in skin’s functioning. For instance, it prevents excessive water loss and protects against physical trauma, foreign particles such as allergens, bacteria, toxic chemicals, and also radiation. The barrier function of the skin mainly resides in the stratum corneum (SC) layer of the epidermis, where differentiated keratinocytes are embedded within a lipid matrix. With age, the ability of the barrier to repair damage from physical insults decreases.5
In an effort to develop an active to improve skin barrier repair and hydration, increase elasticity, and reduce the appearance of wrinkles, the algae extract Saccharina longicruris (S. longicruris) was investigated since algae is known for its survival abilities. Specifically, it develops thickened segments to adapt to water movements and stores compounds to survive harsh environments. Thus, to gain insight into the functionality of S. longicruris extract, the author examined its efficacy to promote keratinocyte differentiation and reverse the gene expression level of senescent human fibroblasts, described here.