Expression of cytoskeletal proteins in developing human minor salivary glands

The presence of an epithelium at different stages of proliferation and differentiation raises interesting questions concerning the histogenesis, cell turnover and differentiation of normal salivary glands. In order to expand knowledge of these aspects, we investigated the expression of cytokeratins (CKs) 7,8,10,13,14,16,18 and 19, vimentin (VIM), and smooth muscle actin (SMA) in developing human minor salivary glands using monoclonal antibodies. Labial, buccal, palatine, and lingual salivary glands and those from the floor of the mouth were obtained from human fetuses (forensic postmortem) ranging in age from gestational weeks 10 to 29. Serial sections, 3 microm thick, were immunostained using a strepto-avidin-biotin technique. Reactivity for all antibodies was negative in the salivary gland epithelium during the developmental stages of bud formation, cord growth, and branching of cord. During canalization and cytodifferentiation, the glandular epithelial cells showed a positive reaction to some CKs and SMA. Cytokeratins 7, 8, 18, and 19 showed strong labeling in luminal duct cells that exhibited some degree of morphological differentiation. Myoepithelial cellc were recognized by antibodies to SMA. Cytoskeletal protein expression changes according to the cell type, degree of differentiation, and stage of morphological development of the glandular structure. These changes occur independently of the localization of the gland.