Effect of High-Dose Topical Minoxidil on Erythrocyte Quality in SKH1 Hairless Mice

SKH1 hairless mice are widely used in carcinogenesis and dermatology research due to their bare skin, as exposure to different agents is facilitated. Minoxidil is a cosmetic drug that is recognized as a mitogenic agent, and mitogens are suggested to have carcinogenic and mutagenic potential by inducing cell division and increasing the possibility of perpetuating DNA damage. Therefore, we hypothesized that the application of high doses of minoxidil to the skin of hairless mice would increase the number of micronucleated erythrocytes (MNEs) in peripheral blood. The objective of this study was to evaluate the topical administration of high doses of minoxidil on peripheral blood erythrocytes of SKH1 mice by means of micronucleus assay. Minoxidil was administered on the entire body surface of mice every 12 or 24 h. Minoxidil dosing every 24 h increased the number of micronucleated polychromatic erythrocytes (MNPCEs), and dosing every 12 h increased the number of MNEs and MNPCEs, as compared to baseline and the negative control group. No decrease in polychromatic erythrocyte frequencies was observed in the minoxidil groups. Therefore, topical application of high minoxidil doses to mice can produce DNA damage, as observed through an increase in the number of MNEs, without producing cytotoxicity, possibly due to its mitogenic effect.