Elucidation of collagen content in different anatomical regions of the dermis of donkeys (Equus asinus): histomorphometric and ultrastructural study

Abstract Research on collagen content in donkey skin is limited, necessitating experimental approaches to aid in the economic production of the leather and cosmetics industries. This study aimed to analyze the histomorphometry and ultrastructure of donkey skin and compare collagen fiber zones in various anatomical regions, both objectively and quantitatively. The study was the first to describe the melanosome number in different skin regions of a donkey. Skin biopsies from fourteen mature male donkeys were used in this study. The epidermis and dermis were examined histologically and ultrastructurally, focusing on the dermo-epidermal thickness ratio and collagen bundle arrangement in the dermis. The study revealed that melanin deposits are higher in the limbs and abdomen of donkeys compared to the back, neck, and thorax, and the dermal-epidermal junction of the back skin is longer. The back skin is the thickest, while the limb skin is the thinnest, despite the high collagen content in the thoracic region. The study indicates that the variation in melanin deposits and dermal-epidermal junction lengths in different body regions of donkeys may be due to variations in mechanical stress and environmental factors. The abdomen had the highest melanocyte count, with significant differences compared to the neck, back, and thorax. The neck region had the lowest count, while the limb, back, and thorax had similar counts. The study’s findings could aid in identifying the difference between normal skin features and collagen-diseased skin in donkeys, aiding in diagnosis and providing valuable insights for veterinarians and researchers studying similar conditions.