Expression of Mucins MUC1, MUC2, MUC5AC, MUC5B, MUC6, and MUC7 in Normal Salivary Glands

Aim: To characterize expression of mucins MUC1, MUC2, MUC5AC, MUC5B, MUC6 and MUC7 in normal salivary glands.

Material and Methods: Twenty-five biopsies from normal salivary glands, collected at Hospital S. João, Portugal, were used: 9 minor salivary glands, 3 submandibular and 13 parotid. Five MoAbs (HMFG1, PMH1, CLH2, mMUC5B-2EU1, CLH5) and one policlonal (LUM7.2) were used to identify mucins MUC1, MUC2, MUC5AC, MUC5B, MUC6 and MUC7. Immunohistochemistry was performed using avidin-biotin-peroxidase.

Results: Salivary glands expressed MUC1, MUC2, MUC5B and MUC7. No expression of MUC5AC or MUC6 was detected. MUC1 was expressed in the apical membrane of ducts in all glands. Subpopulations of serous acini from minor salivary glands and submandibular glands also expressed MUC1 at the cell membrane. MUC2 was detected in the cytoplasm of a subpopulation of mucous cells from five minor salivary glands. MUC5B was widely expressed in mucous acini from submandibular and minor salivary glands. MUC7 was widely expressed in serous acini from minor salivary glands and in a subpopulation of serous acini from submandibular glands. Few cells expressing MUC7 were identified in the serous acini and ducts of five parotid glands.

Conclusions: Our work confirmed previous observations and showed that MUC5B is distributed in mucous acini from minor and submandibular glands and MUC7 is observed in serous acini of minor salivary glands and subpopulations of cells from submandibular and parotid glands. We further showed that salivary ducts expressed MUC1. Subpopulations of serous cells in minor salivary glands and submandibular glands also expressed MUC1. MUC2 was expressed in mucous acini from minor salivary glands. No expression of MUC5AC or MUC6 was detected in normal glands.