P10.142 Molecular mechanism of the hair growth promoting effect by the combination of 6-benzylaminopurine and pentadecanoic acid

T. Midorikawa, T. Chikazawa, N. Sato, T. Yoshino, K. Takada

Life Science Research Center, Research & Development Headquarters, Lion Corporation, Odawawara, Japan

Objectives: To clarify the hair growth promoting effect by combination of 6-benzylaminopurine, one of plant cytokinins, and pentadecanoic acid and to define the molecular mechanism of 6-Benzylaminopurine action.

Methods: 6-Benzylaminopurine (6BA) and pentadecanoic acid (PDA) were topically applied on anagen-induced back skin of seven-week-old C3H/cj male mice until 14th days of anagen induction. The degree of hair re-growth in control and treated mice was scored and calculated hair growth promoting effect. The effects of 6BA on the cultured hair follicle cells were investigated by means of DNA macroarray analysis. These effects were confirmed by investigating of RT-PCR or immunohistochemical analysis of 6BA and PDA treated mice. The effects of BMP5 or ephrinA3 on hair acidic keratin expression were investigated by RT-PCR.

Results: Hair growth promoting effects were observed in 6BA and PDA treated mice. Although the mechanism of PDA action had already known, but molecular mechanisms of 6BA were not known. Therefore, we next performed the DNA macroarray analysis on 6BA treated hair follicle keratinocyte (primary cultured outer root sheath cells) and dermal papilla cells (DPCs). We found that 6BA up-regulated the BMP5 and ephrinA3 genes. When we investigated the expression of BMP5 and ephrinA3 by immunohistochemical analysis and RT-PCR, early induction of BMP5 and strong expression of ephrinA3 was observed in 6BA-treated mice. Recently, we had found the difference of gene expression in DPCs from androgenic alopecia skin and we noticed that neurotrophin 4/5 was up-regulated and BMP2 or ephrinA3 were down-regulated. So, it was suggested that 6BA complement the activities of DPCs. Both BMP5 and ephrinA3 upregulated the hair acidic keratin 3-Ⅱ which expressed in upper hair matrix region. Characteristically, BMP5 exhibited down-regulation of the hair acidic keratin 2 or 5 which were expressed in precuticle keratinocyte or lower matrix region respectively. Thus, it was considered that BMP5 and ephrinA3 had the special role of hair keratin formation, especially hair shaft formation.

Conclusions: These results lead us to the hypothesis that 6BA exhibited the hair growth promoting effect through the expression of BMP5 and ephrin A3 as hair keratin formation factors in the hair cycle.