Alteration of mucins in the submandibular gland during aging in mice

Mucins are large glycosylated glycoproteins that are produced in the salivary glands, and their changes may contribute to the development of xerostomia due to aging and the accompanying deterioration of oral hygiene. This study aimed to characterize the changes in the mucins produced in submandibular gland (SMG) during the aging process.

SMG mucins derived from mice of each age were separated using supported molecular matrix electrophoresis (SMME). Subsequently, the membranes were stained with Alcian blue (AB) or blotted with MAL-II lectin. The SMME membranes stained with AB were subjected to densitometric analysis and glycan analysis. The detailed structures of O-glycan were investigated by tandem mass spectrometry (MS/MS).

The SMG of mice secreted three mucins with different glycan profiles: age-specific mucin, youth-specific mucin, and a mucin expressed throughout life, and the expression patterns of these mucins change during aging. Additionally, age-specific mucin began to be detected at about 12 months of age. A mucin expressed throughout life and age-specific mucin had the same mass of major glycans but different structures. Furthermore, the proportion of mucin glycan species expressed throughout life changed during the aging process, and aging tended to decrease the proportion of fucosylated glycans and increase the proportion of sialoglycans.

There are three secretory mucins with different glycan profiles in the SMG of mice, and their expression patterns change according to the period of the aging process. The proportion of glycan species of mucin expressed throughout life also changes during the aging process.