Dynamic expression of ornithine decarboxylase in hair growth

Ornithine decarboxylase (ODC) is the key enzyme in the synthesis of polyami nes. small cationic molecules believed to have a role in many cellular proc esses such as cell migration, proliferation and differentiation. We show th at ODC expression is associated with cell proliferation and commitment in h air follicle development and hair growth. In embryonic epidermis, ODC is ex pressed in ectodermal cells at sites where follicles develop, and persists in cells at the leading edge of the follicle placode. ODC is abundantly exp ressed in proliferating bulb cells of anagen follicles, except for a pocket of cells at the base of the bulb. Entry of the follicle into catagen is ac companied by a down-regulation of ODC expression, which is not resumed unti l a new follicle is initiated. In vibrissae, ODC expression is more complex . ODC is expressed nor only in the bulb but also in the hair shaft, present ing a striking biphasic pattern. Additionally, ODC is expressed in a group of outer root sheath cells in the vicinity of the follicle bulge, the putat ive site of hair follicle stem cells. (C) 1999 Elsevier Science Ireland Ltd . All rights reserved.