Message of Nexin 1, a Serine Protease Inhibitor, Accumulates in the Follicular Papilla During Anagen of the Hair Cycle

The study identified a 1.3 kb mRNA encoding nexin 1, a serine protease inhibitor, which was found in high quantities in rat follicular papillary cells but not in skin fibroblasts. Nexin 1 can inactivate several growth-modulating serine proteases. In situ hybridization revealed that nexin 1 mRNA accumulated in the follicular papilla cells during the anagen phase of the hair cycle, but was undetectable in keratinocytes or other skin mesenchymal cells. The level of nexin 1 mRNA varied among different rat vibrissa papillary cell lines and correlated with their ability to support follicular reconstitution in vivo. These findings suggested that nexin 1 might play a role in regulating hair follicle growth.