Mucins in Minor Salivary Glands of Children and Adults

Mucins are vital components in the biofilm providing a multivalent first line of defence in the oral cavity. In human saliva, two essentially different mucins, MUC5B and MUC7, have been identified. It has been suggested that MUC5B forms a matrix retainer for other protective proteins. Early studies indicate that MUC7 takes part in the human salivary non-immune defence system, interacting with oral micro-organisms. Studies of whole saliva have shown that the amount of mucins vary with age. Concerning minor glands, no information about age-related differences in secretion of mucins seems to be available. Objectives: To study the amount of MUC5B and MUC7 in minor gland saliva in children and adults in defined mucosal areas. Methods: 90 individuals were recruited in three categories: 3-year-old children, 14-year-old children, and young adults. Saliva was collected in the labial and buccal mucosal areas with filter papers. Measurements of the amount of saliva were made using a Periotron 8000. The assessment of MUC5B and MUC7 was carried out in an ELISA using LUM5B-2 antiserum and LUM7-1 antiserum, respectively. Mann-Whitney U test were used testing the differences between the age-groups (at the 0.05 level of significance). Results: MUC5B and MUC7 were present in the labial minor gland saliva in all three categories. In the labial area, MUC7 was lower in the 3-year-olds compared to the adults (P<0.05). In the buccal area no detectable amounts of MUC5B and MUC7 were found in most individuals. Conclusions: MUC5B and MUC7 were excreted by the labial minor glands in children as well as in teenagers and adults. The lower concentration of MUC7 in younger children, may indicate a different protecting capacity in the labial area. In addition, the results suggest a site-dependant variation in minor gland expression of mucins. Approved by the ethical committee Lund University.