Pre and Postnatal Development of the Rabbit Thin Skin

Rabbits are a popular model in laboratory animal medicine especially in the fields of human dermatology, experimental pharmacology and experimental toxicology. The present study aimed to investigate and re-evaluate, by light and scanning electron microscopy, the pre and postnatal development of rabbit skin. Early at embryonicage 15days(E15), the developing skin formed only of a single or double-layered epidermis and a loosely arranged mesodermal cells; the future dermis. At E17, epidermal stratification became clear and formed of basal layer, intermediate layer and the superficial (peridermal) layer. Additionally, the outer mesodermal cells of the dermis became condensed below the basal cells of the epidermis and followed by the formation of hair placodes at embryonic period E19. At E 25 the stratification of developing epidermis became more distinct with an increase in the extension and differentiation of hair follicle. At late pregnancy at E28, the epidermis became fully differentiated and nearly showed mature structure where the intermediate layer of epidermis differentiated into spinous and granular layers and the appearance of the keratinized layer. Just before birth atE30, the hair shaft started to protrude through skin surface associated with the development of the sebaceous glands as an outgrowth from the hair follicle. Postnatally and at one week old rabbit, the skin appeared nearly mature, the dermis became thicker with well-developed dermal papillae and the majority of the free ends of hair shafts elongated and protruded upon the surface of epidermis. At two months old,the rabbit skin became fully matured with marked increase collagenous fibers within dermis. During pre- and postnatal development of rabbit skin we could not observe any sweat glands of the examined skin samples. We can conclude that the development of the rabbit thin skin and its appendages was mainly established during the prenatal period with few developmental events during postnatal period. The extensive fur covering and absence of the sweat gland of rabbits might be considered during intensive rabbit production to avoid stress upon rabbit thermoregulation mechanisms.