Histological localization of myxoid tissue in normal human palatal mucosa and its glycosaminoglycans

Eighteen specimens of palatal mucosa were taken from 17 human subjects. Paraffin-wax sections were stained by routine methods and with various techniques to demonstrate glycosaminoglycans (GAG). In some sections, GAG were removed by selective degradative procedures before staining. Beneath all rugae, there were myxoid areas varying in size and marginal definition. Collagen fibres were few; elastic and reticulin fibres were numerous in a minority of sections. Alcianophilia at pH 2.5, preventable by streptomyces hyaluronidase digestion, suggested the presence of hyaluronic acid beneath the rugae. Alcian-blue staining at pH 1.0 and with the critical electrolyte concentration method using 0.5 M MgCl2 did not distinguish the myxoid tissue from the surrounding connective tissue and could be prevented by digestion with testicular hyaluronidase or chondroitinase ABC. Chondroitin sulphate and, or dermatan sulphate thus may be present but were not localized to the myxoid tissue. This unusual zone of loose connective tissue may act as a physical buffer resisting the local effects of high loads by allowing reversible extrusion of the water.