Nestin as a Marker of Unipotent Epithelial Progenitor Cells Differentiating into Outer Root Sheath Keratinocytes in Embryonic and Adult Hair Follicles

This study investigated the role of nestin, an intermediate filament protein, in hair follicle (HF) development and found that nestin-expressing cells contribute to the formation of outer root sheath (ORS) keratinocytes in both embryonic and adult HFs. Using genetically modified mice that express enhanced green fluorescent protein (EGFP) under the control of the nestin promoter, the researchers observed EGFP-positive cells in the epithelial layer of embryonic HFs at the peg stage, which were positive for keratin 5 but not for other stem cell markers. In adult HFs, EGFP-positive cells were not labeled for keratin 15, a marker for multipotent HF stem cells, but when hair was depilated to induce the anagen stage, the majority of ORS keratinocytes were EGFP-positive. This suggests that nestin-expressing cells are unipotent progenitor cells that differentiate into ORS keratinocytes during both HF development and in adult HFs.