The Effect of Coapplication of Capsaicin and Minoxidil on the Murine Hair Growth

Lee, Won Soo; Ahn, Hyung Jin; Kim, Young Hee

Abstract

BACKGROUND
Capsaicin induces the release of substance P(SP), and depletes and prevents reaccumulation of SP in C type nerve fibers. Trophic role of SP and the neural mechanisms of hair growth control remain obscure. Minoxidil is widely used as a topical agent for hair loss. OBJECTIVE: The effects of coapplication of capsaicin and minoxidil on hair growth and cycle, compared with application of capsaicin or minoxidil alone, was evaluated. METHODS: After depilation of the back skin of mice, we divided mice into four groups, i.e., control, capsaicin, minoxidil and coapplied group. We examined hair regrowth after depilation in terms of macroscopic examination, image analysis using phototrichograms, measurement of hair regrowth length, microscopic examination and measurement of mast cell count, and [methyl-3H] thymidine uptake. RESULTS: The results are summarized as follows; 1. Hair growth of capsaicin group and minoxidil group began faster than that of coapplied group and control. Thereafter, hair growth of capsaicin group was observed as the fastest, followed by minoxidil group, coapplied group, and control. 2. The percentage of the area of hair regrowth in coapplied group was lower than capsaicin group, similar to minoxidil group, and higher than control at the 15th day after depilation. At the 30th day after depilation, there was no significant difference between coapplied group and capsaicin group. 3. Hair of coapplied group grew steadily up to the 30th day after depilation, growing taller than any other group. 4. On microscopic examination, capsaicin was able to make the hair cycle faster and shorter than control, but minoxidil group and coapplied group prolonged the anagen phase of hair cycle. 5. Though mast cell count decreased in all four groups after depilation, capsaicin group decreased significantly more than the other group. 6. [Methyl-3H] thymidine uptake increased in all four groups until the 5th day after depilation, and then decreased. The uptake of coapplied group was similar to that of minoxidil group. CONCLUSION: These results suggest that capsaicin can not only induce the anagen phase quickly, but also sustain constant effect on hair growth. Minoxidil can also induce the anagen phase fast, and prolong the duration of anagen phase. Therefore, it is concluded that coapplication of capsaicin and minoxidil can grow hair quickly and steadily.