Abstract
The hamster cheek pouch has been used to evaluate the effects of drugs and chemicals in the mistaken belief that it is an appropriate surrogate for determining the effect such agents would have on the gastrointestinal tract and oral a cavity epithelium. 1– 8, 10– 12, 12– 27
aAn “oral” cavity does not communicate directly with the nasal cavity or eustachian tubes. A “buccal” cavity, seen in frogs and lower species, has a direct connection to the nasal cavity and eustachian tubes.
For several reasons the above assumption is not valid. 9, 13 Hamster cheek pouches are specialized structures lined with a relatively thick layer of surface keratin lying above cornified, stratified squamous epithelium: essentially like the epidermis, but lacking dendritic cells and adnexal structures such a mucous b glands. Hamster cheek pouch epithelium is similar to that of the tongue, gingiva and hard palate but lacks equal numbers of resident dendritic cells and secretary glands. Unkeratinized stratified squamous epithelium lines the remainder of the oral cavity. The keratinized, multiple-layered, pouch epithelium is resistant to abrasion and hinders absorption, allowing hamsters to store undigested food in the form of fruits, nuts, berries and insects in their pouches. Pouch adventitia is rather dense, lacking lymphatics and serving mainly to adhere the epithelium.
Mucosa lines some parts of the gastrointestinal tract. The single-layer of epithelium is columnar or low columnar and is interspersed with mucus-secreting and other glands. Surface mucus, for which the name is derived, provides protection against chemicals and acts as a lubricant. Mucosal surfaces of the gut are absorptive. In the small intestine, there are specialized delicate microvilli dedicated to this purpose. Mucosa contains Peyer's patches and other immune surveillance such as intraepithelial lymphocytes. A rich system of nerves, blood, and lymph vessels underlies the epithelium supporting the secretary, absorptive and immune surveillance activity.
Given all of the above and perhaps most importantly the fact that the hamster cheek pouch is an immunologically protected site, 9, 17 use as a surrogate for the gastrointestinal and oral mucosa does not seem very compelling. Thinner areas of the epidermis with intact immunological surveillance and greater ease of access for evaluation may be a better choice as surrogates. Both sites unfortunately suffer the disadvantage of not being mucous membranes. Painful lesions in the skin do not interfere with food intake to the same extent as those in the cheek pouch– certainly an advantage of the skin site.
Julia H. Riley, MS
Diplomate American College Veterinary Pathologists
Diplomate American Board Toxicology