“…In anagen hair follicles proliferation occurs in follicular epithelial cells surrounding the dermal papilla. After proliferation ceases above Auber's critical line (broadest aspect of the follicular bulb), ultrastructural, immuno-histochemical, in-situ hybridization and proteomic studies identify seven shells of distally migrating cell lineages that differentiate into the hair shaft and the supporting inner-root sheath (Langbein and Schweizer, 2005, Langbein et al, 2010, Legué and Nicolas, 2005, Niemann and Watt, 2002, Orwin, 1979, Plowman et al, 2015). Extension of the hair shaft is powered by a poorly understood process of cell proliferation, reshaping, and migration with narrowing of the surrounding inner root sheath, as well as deposition and hardening of keratin (Bornschlögl et al, 2016, Chapman and Gemmell, 1971, Langbein and Schweizer, 2005, Orwin and Woods, 1982, Parry et al, 2007, Plowman et al, 2015, Rafik et al, 2006, Rogers, 1964).…”