P6.69 Minoxidil promotes hair growth in female androgenetic alopecia by increasing hair diameter, the ratio of terminal/vellus hairs, and the number of Ki67-positive proliferating hair follicle cells in horizontal scalp sections.

Rudolf E. Schopf, Michael Bress

Dept. Dermatology, Johannes Gutenberg University, Mainz, Germany

Objectives: Minoxidil has been shown to promote hair growth. The short-term effects of a 5% solution of minoxidil on hair diameter, the ratio of terminal/vellus hairs and the proliferation marker Ki67 have not been examined before.

Methods: We tested the effects of a 5% solution of minoxidil applied twice daily for 12 weeks on the scalp of 10 women with androgenetic alopecia. Hair regrowth was evaluated by histologic analysis of paired 5 mm punch biopsy specimens for horizontal sectioning taken from the parietal region of the scalp from the right side on week 0 and the contralateral side on week 12. In histologic sections, the mean diameter of the hair shafts was determined in blinded fashion employing a micrometer grid; a hair shaft with a diameter of <30 micrometer was defined as vellus hair, a diameter of > 30 micrometers as a terminal hair. The ratios of terminal/vellus hair are also presented. Cellular proliferation in hair follicles was ascertained by Ki67 staining using the alkaline phosphatase method by counting the stained nuclei of 5 hair follicles in blinded fashion (Dako, Denmark). In addition, visual analysis was performed by scalp photography.

Results: We found the following hair diameters: 0.0399 +/- 0.0011 (week 0, mean +/- SE) vs. 0.0455 +/- 0.0014 mm (week 12, p<0.05, Wilcoxon test); the ratios of terminal/vellus hair were: 2.99 +/- 0.49 (week 0) vs. 4.74 +/- 0.54 (week 12, p<0.05). Ki67 staining in hair follicles was: 8.04 ± 1.45 (week 0) vs. 9.59 ± 1.62 nuclei (week 12, p<0.05). Scalp photography corresponded to increased hair growth after 12 weeks.

Conclusions: These findings show that a twice daily, 12-week treatment with 5% topical solution of minoxidil enhances hair growth in women by increasing the hair shaft diameter, the ratio of terminal/vellus hairs, and the number of Ki67-positive proliferating cells in hair follicles.