miRNA is a kind of 20-25-nucleotide endogenous small RNA present in cells. It is derived from a DNA that produces no protein, and is generated from hairpin-shaped transcripts. miRNA functions as a repressor that binds to the complementary sequence of 3′-UTR of its target mRNA to induce the inhibition of translation or unstabilization of the target mRNA, and ultimately repress the protein synthesis of the target mRNA. It is known that one miRNA targets several mRNAs and mRNA may also be controlled by several miRNAs.
miRNA is currently known to play a very important role in a number of biological processes including regulation of developmental timing, apoptosis, fat metabolism, and hematopoietic cell differentiation among others, and thus has received a great deal of attention in the field of life science. However, while studies on the function of miRNA in the processes of development of diseases such as cancer have considerably progressed, studies on the role of miRNA in the skin science are relatively insufficient. Recently, it was reported that miR-203 targets p63 mRNA in keratinocytes to inhibit the differentiation of the keratinocytes and that miR-125b inhibits the differentiation of skin stem cells and inhibits the division of keratinocytes, but there are little or no reports of skin-related specific miRNA and the function thereof. In addition to miR-203 and miR-125b, several specific miRNAs are sufficiently expected to play a biologically important role in the skin. In addition, miRNA can be used in various applications, including biological markers and materials, and thus it is concluded that studies on the function of miRNA in the skin can be applied in various fields, including the cosmetic and medical fields.
The skin is roughly divided into epidermis and dermis, and melanocytes present in epidermis synthesize a pigment (melanin) that shows the inherent color of the skin. Biological factors that control skin pigments can be roughly divided into factors that make melanosome in melanocytes, and factors that transport melanosome. Of the factors that make melanosome, the most well-known factors include tyrosinase (TYR) and the like, and factors known to be involved in melanosome transport include Rab27a and the like. Recently, it was known that transcription factors such as PAX3, MITF and the like also participate in the pigment regulation process. Thus, these factors that regulate the pigment become important targets for skin whitening, black hair production or gray hair prevention.