Analysis of age-related changes in the functional morphologies of salivary glands in mice

Salivary glands in the elderly commonly exhibit salivary dysfunction resulting dry mouth, poor oral hygiene, and dental caries. However, in vivo changes of salivary glands during aging have not been well documented in the literature. This study was undertaken to determine age-related morphometric and functional changes of salivary glands using an aging mouse model.

Male C57BL/6 mice were divided into three groups, group A (10 weeks old; n=10), group B (30 weeks old; n=10), and group C (90 weeks old; n=10). Body weights, salivary gland weights, salivary flow rates, and salivary lag times were measured and compared. Histomorphometric examinations and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were performed. In addition, changes in salivary uptake and excretion were observed by single-photon emission computed tomography (SPECT).

Body and gland weights increased with age. Gland weight was significantly higher in group B than in groups A and C. Salivary lag time was significantly greater in group C than in groups A and B, and salivary flow rate was significantly greater in group B than in groups A and C. Histologic evaluations exhibited acinar cell atrophy, cytoplasmic vacuolization, lymphocyte infiltration, small mucin component and more periductal fibrosis in salivary glands of group C. TUNEL assays revealed that apoptotic salivary epithelial cells were significantly more numerous in group C than in groups A and B. (99m)Tc-pertechnetate excretion rate was significantly lower in group C than in groups A and B in SPECT.

Various morphometric and histopathological changes were observed in the salivary glands of aging mouse as well as relevant functional alterations, such as, decreased saliva production and excretion. Increased number of apoptotic salivary epithelial cells may contribute to the observed functional deterioration.