Meibomian Gland Changes in the Rhino (hrrhhrrh) Mouse

The rhino mouse, a single gene recessive mutation, is characterized by abnormal epidermal differentiation and maturation leading to the loss of hair at 1 month of age as well as follicular and epidermal hyperkeratoses. We evaluated the lids and corneas of nine rhino mice and their normal litter mates at various ages from 3 months to 1 year. Tissue specimens were studied by light microscopy, scanning and transmission electron microscopy as well as immunoperoxidase using a polyclonal rabbit anti-keratin antibody. At 3 months of age there was a thickening and hyperkeratinization of the palpebral epidermis which extended into and included the meibomian gland central duct. Whereas in the skin, hyperkeratinization is followed by follicular hyperkeratosis and dermal cyst formation, in the meibomian gland, ductal hyperkeratinization appeared to lead to loss of well developed acini followed by atrophy of the gland at 1 year as confirmed by immunostaining for keratin proteins. Scanning electron microscopy revealed marked plugging of the meibomian gland orifice with keratinized cells or debris in contrast to the patent orifice of the normal lid. Ocular surface changes included the presence of a whitish exudate covering the surface of the eye and increased numbers of preexfoliative corneal epithelial cells. These findings suggest that the rhino mouse may represents the first naturally occurring disorder of the meibomian gland.