Cyclin-dependent kinase inhibitors, p21(waf1/cip1) and p27(kip1), are expressed site- and hair cycle-dependently in rat hair follicles

In order to investigate the role of cyclin-dependent kinase (CDK) inhibitor s in hair growth, we analyzed the expressions of p21(wafl/cip1) and p27(kip 1) during the synchronized hair cycle of rat coat. The mRNAs of both p21(wa f1/cip1) and p27(kip1) were detected in anagen hair follicles by reverse tr anscription and polymerase chain reaction and their localization was clearl y demonstrated in the upper half portion of the hair bulb and the cortex by in situ hybridization. The dermal tissue containing hair follicles was the n excised from the anterior dorsal skin of the 5-12-week-old rats at 0.5 we ek intervals and the expressions of p21(wafl/cip1) and p27(kip1) were analy zed by northern blot hybridization. The mRNA of both CDK inhibitors was exp ressed at relatively high levels during anagen than during telogen, a fact which correlated with the mRNA expression levels of hair differentiation ma rkers, type I hair keratin (Ha3) and high sulfur protein B2. These results imply that CDK inhibitors, p21(wafl/cip1) and p27(kip1), are involved in th e differentiation of follicular epithelial cells. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.