Skin structures associated with percutaneous drug penetration differ by body site in Beagles

Objective: To characterize differences among body sites in skin morphological features of Beagles that may influence percutaneous drug penetration. Methods: This exploratory study was conducted from November 2024 through March 2025 with 6 Beagles. Skin samples were collected from 3 body sites-the dorsum, lateral trunk, and ventral abdomen. Skin samples were collected under sedation with local anesthesia. Epidermal thickness, the number of stratum corneum (SC) layers, and dermal vessel density were evaluated histologically. Follicular ostia density was evaluated using dermoscopic images. Data are presented as mean values with 95% CIs. Results: Epidermal thickness showed only small differences among body sites. The number of SC layers also showed small differences (maximum mean difference, approx 0.3 layers). In contrast, follicular ostia density showed large differences among body sites and was highest in the dorsum, intermediate in the lateral trunk, and lowest in the ventral abdomen. Dermal vessel density showed moderate differences, with higher values in the ventral abdomen than in the dorsum and lateral trunk. Conclusions: In Beagles, epidermal thickness and the number of SC layers are relatively uniform across body sites, whereas follicular ostia density and dermal vessel density show clear differences among body sites. Clinical Relevance: These findings suggest that skin structural factors other than epidermal thickness and the number of SC layers may influence percutaneous drug penetration; however, this remains a hypothesis and requires further study.