Keratin-Mediated Hair Growth and Its Underlying Biological Mechanism

This study demonstrates that keratin, when injected intradermally, can stimulate hair growth in mice. This effect is due to keratin's interaction with hair-forming cells, leading to the condensation of dermal papilla cells and the creation of a P-cadherin-expressing cell population, known as the hair germ, from the outer root sheath cells. This process is influenced by the microenvironmental changes induced by keratin. The study also finds that keratin released from apoptotic outer root sheath cells, which are induced by transforming growth factor beta 2 (TGFβ2), is crucial for the formation of the dermal papilla cell condensation and the hair germ. The removal or reduction of keratin from these apoptotic cells impairs the formation of these structures. This pilot study suggests that keratin released from dying epithelial cells may play a role in hair regeneration and provides insights into keratin's biological functions in tissue regeneration and development.