A Comparison of Methods of Anagen Synchronization in the Adult Rat Model of Chemotherapy-Induced Alopecia

Background: Chemotherapy-induced alopecia is a common, psychosocially distressing side effect of cancer treatment for which preventative therapies are lacking. Several animal models have been developed to study CIA, including adult murine models. In order to induce CIA in adult models, hair follicles must be synchronized into anagen. The present study seeks to investigate which method of anagen synchronization yields the most representative model of CIA; no study thus far has compared these methods. Methods: Biopsies were analyzed of adult rat skin treated with one of four methods of anagen synchronization: clipping, shaving, waxing, or plucking and an untreated control group. Twenty follicles were assessed at random from each animal in each group and the percentage of hair follicles in anagen V-VI was determined. Results: There were significant differences in the histological and gross profiles of clipping, shaving, waxing, and plucking. Clipping produced the most robust anagen, with 85% of hair follicles in anagen V-VI, while shaving was found to have 30% of follicles in anagen V-VI. Waxing, plucking, and control had no hair follicles in anagen V-VI. Furthermore, shaving, waxing, and plucking demonstrated noticeable gross skin trauma, with waxing resulting in the most severe. Conclusions: Clipping is the preferred method of anagen synchronization in the adult rat model for CIA, as it produces the most robust anagen and has no evidence of gross skin trauma, decreasing the likelihood of confounding results from traumatic hair removal. The next best method is shaving, followed by plucking, and ending with waxing.