Keratins of the Human Hair Follicle: Hyperproliferative Keratins Consistently Expressed in Outer Root Sheath Cells In Vivo and In Vitro

The study analyzed keratins produced by different compartments of the human hair follicle and compared them to those produced by cultured hair follicle and interfollicular keratinocytes. It identified five major keratins consistently expressed in the outer root sheath (ORS) cells both in vivo and in vitro, which were similar to those expressed by interfollicular epidermis keratinocyte cultures. The research demonstrated that the microenvironment influences the differentiation of ORS cells, leading to the consistent expression of "basal" and "hyperproliferative" keratins. This suggests that while the environment directs keratin expression, other environmental responses may occur, such as during skin wound healing by ORS cells.