Procyanidin B-2, extracted from apples, promotes hair growth: a laboratory study

Summary Background We have previously reported that several selective protein kinase C (PKC) inhibitors, including procyanidin B‐2, promote hair epithelial cell growth and stimulate anagen induction. Objectives We discuss the hypothesis that the hair‐growing activity of procyanidin B‐2 is related to its downregulation or inhibition of translocation of PKC isozymes in hair epithelial cells. Methods We examined the effect of procyanidin B‐2 on the expression of PKC isozymes in cultured murine hair epithelial cells as well as PKC isozyme localization in murine dorsal skin at different stages in the hair cycle. Results We observed that procyanidin B‐2 reduces the expression of PKC‐α, ‐βΙ, ‐βΙΙ and ‐η in cultured murine hair epithelial cells and also inhibits the translocation of these isozymes to the particulate fraction of hair epithelial cells. Our immunohistochemical analyses demonstrated that PKC‐α, ‐βΙ, ‐βΙΙ and ‐η are specifically expressed in the outer root sheaths of both anagen and telogen hair follicles. The hair matrix at the anagen stage showed no positive staining for these PKC isozymes. Moderate to intense staining for PKC‐βΙ and ‐βΙΙ in the epidermis and hair follicles was observed in a telogen‐specific manner; however, expression of PKC‐α and ‐η during the telogen stage was not conspicuous. Gö 6976, an inhibitor of calcium‐dependent (conventional) PKC, proved to promote hair epithelial cell growth. Conclusions These results suggest that PKC isozymes, especially PKC‐βΙ and ‐βΙΙ, play an important role in hair cycle progression and that the hair‐growing mechanisms of procyanidin B‐2 are at least partially related to its downregulation of PKC isozymes or its inhibition of translocation of PKC isozymes to the particulate fraction of hair epithelial cells.