Skin anti-aging treatments in cosmetics
Skin aging is a natural process where skin gets thinner and loses fat, becoming less plump and smooth, losing its youthful fullness. Most of these changes occur in the dermis, which is composed of an extracellular matrix rich in collagen that provides structure for skin cells and firmness to the skin. During aging, there is a decrease in the production of collagen; collagen fibers get thicker and fragmented and growth factor signaling is impaired, decreasing collagen content.
This natural process can be worsened by external factors, creating deeper wrinkles and age spots on the skin. These external factors are thought to worsen skin aging by decreasing the amount of natural antioxidants in the skin and increasing the production of reactive oxygen species, damaging skin structural proteins and inducing inflammation. In addition, ultraviolet light can directly harm nucleic acids and proteins in the skin, increasing damage. External factors include sunlight, smoking, alcohol and some skin care products which may cause irritation, accelerating skin aging.
Growth Factors and Cytokines
Since growth factors and cytokines are known to directly affect collagen synthesis, they have been used in several cosmetic products to reduce skin aging. Some of these growth factors are, vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF). Cytokines used in cosmetic products include TGF-beta and interleukins. For instance, the PSP products from Neocutis, including Bio-restorative Skin Cream and Lumiere Bio-restorative Eye Cream, use a mixture of growth factors and cytokines obtained from cultured human fibroblasts. Other brands, such as the TNS product line from SkinMedica, use conditioned medium obtained from neonatal foreskin fibroblast culture, rich in growth factors. Although some studies suggest a positive effect of these products on skin aging, the large molecular size of growth factors (generally over 15000 Da) limits their ability to penetrate the skin, decreasing the efficiency of these treatments.
Other cosmetic products use matrikines instead. Matrikines are short peptides generated by proteolysis of macromolecules from the extracellular matrix (ECM) of the dermis, rich in collagen, elastin and fibrillin. Matrikines can modulate cell proliferation and migration, and have been shown to play a role in wound healing. In addition, their small size allows better skin penetration than growth factors and cytokines, making them better alternatives for addressing skin aging. Several matrikines are used in cosmetic products, including the tripeptide Glycine-histidine-lysine (GHK), which enhances ECM synthesis and increases collagen content; the tetrapeptide Glycine-glutamate-lysine-glycine, also known as GEKG or tetrapeptide-21, which was shown to improve skin quality and increase procollagen production; and the micro-protein complex (MPC), a mixture of antioxidants and matrikines, which seems to increase skin elasticity and firmness, although independent studies remain scarce.
Recently, researchers have started studying the use of umbilical cord stem cells for skin repair and regeneration because of their capability of self-renewal and of differentiation into several types of cells. This technology has been studied in vivo in several animal models showing that umbilical cord stem cells could accelerate wound healing. These encouraging results suggest that umbilical cord stem cells have a great potential for skin repair, although this remains to be tested in clinical studies in humans.
Aldag, C; Nogueira Teixeira, D; Leventhal, PS. 2016. Skin rejuvenation using cosmetic products containing growth factors, cytokines, and matrikines: a review of the literature. Clin Cosmet Investig Dermatol. 9:411-419.
Rittié, L; Fisher, GJ. 2015. Natural and sun-induced aging of human skin. Cold Spring Harb Perspect Med. 5(1):a015370.
Zeinali, R; Biazar, E; Keshel, SH; Tavirani, MR; Asadipour, K. 2014. Regeneration of full-thickness skin defects using umbilical cord blood stem cells loaded into modified porous scaffolds. ASAIO J. 60(1):106-14.