Discovered in 1993, microRNAs (miRNA) are the most abundant regulators of gene expression in the genome (up to 90% of the genes). These small, non-coding RNA molecules (20 to 25 nucleotides long) are real natural on/off switches for numerous physiological processes. Indeed, once produced, miRNA molecules specifically bind to the beginning of their own messenger RNA (mRNA) molecule, thereby rendering the mRNA information impossible for the ribosome to read, or turning it into the target of proteins that will destroy them.
Mostly studied for their implication in human diseases such as cancer or heart disease, the roles of miRNAs have expanded over the years. Studies are beginning to examine how certain specific miRNAs can act on the most intricate causes of cosmetic concerns such as skin senescence or oily skin and associated blemishes.
Senestem™, a high-tech natural active ingredient developed by IRB by Sederma, has been demonstrated to inhibit the microRNAs involved in:
- Cellular senescence: miR-30e and miR-181a have been shown to clearly participate in increasing senescent phenotypes in fibroblasts. By decreasing the numbers of these microRNA molecules (-54% and -36%, respectively), Senestem™ helps prolong cell survival and reduce the appearance of senescent phenotypes.
- Extracellular matrix breakdown: Senestem™ limits expression of miR-29 (-35%) and miR-196a (-34%), which have been revealed to control collagen-I, collagen-IV and elastin synthesis. Thereby, it helps boost extracellular matrix macromolecule synthesis and improve the quality of the dermis. To complete this action, Senestem™ also modulates the activity of the matrix metalloproteinases (MMPs) responsible for breaking down the large proteins that give structure to the matrix, such as collagens and elastin. MMPs are controlled by miR-21, so by decreasing the latter by 34%, Senestem™ decreases MMP activity and improves the quality, density and thickness of the dermis.
Sebuless™ is another natural active ingredient developed by IRB by Sederma and designed to mattify and equalize skin tone of oily and acne-prone skin. Thanks to an exclusive cosmetogenomic approach, it has been demonstrated to control P. acnes (Propionibacterium acnes) bacteria proliferation and inflammation-induced by miR-105 up-regulation.
The proliferation of P. acnes is a main feature of acne-prone skin. When this bacterium binds to skin cells through surface receptors called Toll-Like Receptors 2 (TLR-2), this triggers a cascade of reactions that result in the production of pro-inflammatory molecules. TLR-2 synthesis is modulated in the keratinocyte by a micro-RNA called miR-105. By increasing the expression of miR-105 by 65%, Sebuless™ reduces the expression of TLR-2, thereby reducing the number of bacterial binding sites, and thus, the bacterial effects.
These two ingredient examples demonstrate the importance of this microRNA regulated pathway and its interest for the cosmetic industry. The studies are only at a starting point and discoveries on microRNAs and more particularly on molecules that can act on them will lead to a new generation of skin care products.