small RNA molecule regulating gene expression and hair follicle development
miR-21 is a type of microRNA, which are small molecules that help regulate gene expression in cells. It is known to play a role in various biological processes, including cell growth, apoptosis (programmed cell death), and differentiation. In the context of hair and alopecia, miR-21 has been implicated in the regulation of hair follicle development and cycling, and its dysregulation may contribute to hair loss conditions.