Control by a hair's breadth: the role of microRNAs in the skin

MicroRNAs have continued to attract enormous interest in the scientific community ever since their discovery. Their allure stems from their unique role in posttranscriptional gene expression control as well as their potential application as therapeutic targets in various disease pathologies. While much is known concerning their general biological function, such as their interaction with RNA-induced silencing complexes, many important questions still remain unanswered, especially regarding their functions in the skin. In this review, we summarize our current knowledge of the role of microRNAs in the skin in order to shine new light on our understanding of cutaneous biology and emphasize the significance of these small, single-stranded RNA molecules in the largest organ of the human body. Key events in epidermal and hair follicle biology, including differentiation, proliferation, and pigmentation, all involve microRNAs. We explore the role of microRNAs in several cutaneous processes, such as appendage formation, wound-healing, epithelial-mesenchymal transition, carcinogenesis, immune response, and aging. In addition, we discuss current trends in research and offer suggestions for future studies.