862 Defining the molecular signature of the hair follicle dermal sheath and its functional requirement for hair cycle progression during catagen

The document presents a study that aimed to define the molecular signature of the hair follicle dermal sheath (DS) and its role in hair cycle progression during catagen. The researchers co-isolated DS, dermal papilla (DP), and dermal fibroblasts to identify gene expression profiles through RNA sequencing. They discovered a unique DS gene expression signature, suggesting potential structural and signaling roles for the DS in hair follicle support and regulation. Using the DS signature gene aggrecan (Acan) for inducible targeting, they created a specific system to manipulate the DS. Conditional cell ablation with the cytotoxic DTA system revealed that the DS is essential for outer root sheath regression at the onset of catagen, indicating a need for DS/epithelial cross-talk during normal hair follicle cycling. This study assigns the DS as a crucial hair follicle niche component, prompting further investigation into its functions for hair follicle activities.