Normalisation of hair follicle morphology in C3H/HeJ alopecia areata mice after treatment with squaric acid dibutylester

Alopecia areata is a non-scarring, reversible disorder, presumably caused by an autoimmune attack on anagen hair follicles. Treatments are numerous, and most of these are ineffective. However, the elicitation of contact dermatitis on the affected skin is commonly associated with hair regrowth. A major advance in the study of alopecia areata has been the introduction and characterisation of the C3H/HeJ mouse model that exhibits many features of the human disease. In this study we examined the effects of squaric acid dibutylester treatment on hair follicles and the associated leukocyte infiltrate in alopecia areata mice by light and transmission electron microscopic analysis. This was compared with unaffected normal mice and alopecic untreated mice. Experimental mice were treated unilaterally with the contact allergen squaric acid dibutylester and the skin was assessed after hair regrowth. The characteristic pathological picture of alopecia areata was observed in alopecic but not normal mice. Nine of eleven experimental mice regrew hair on the treated side only and this was associated with a reduction in peri/intrafollicular inflammatory cell infiltrates, hair follicle dystrophy, melanin incontinence/clumping, and an increase in the numbers of hair follicles in full anagen. This normalisation of hair follicle status after treatment reflects the successful reversal of disease in these mice. The mechanism of action of topical immunotherapy with a potent contact allergen such as squaric acid dibutylaster still needs to be elucidated, but an altered immune milieu is suspected. This study further validates the C3H/HeJ mouse model of alopecia areata in the search for therapeutic interventions in this common hair follicle disorder.