Characterization of cytoskeletal proteins in basal cells of human parotid salivary gland ducts

Abstract

From previous immunofluorescent, immunohistochemical and ultrastructural studies, myoepithelial cells have been reported to be absent from the striated and excretory ducts of human salivary gland. Yet recently, certain anti-cytokeratin monoclonal antibodies which specifically label the myoepithelium of salivary gland acini and intercalated ducts have also been found to stain basally situated cells in both striated and excretory ducts. In this study, we have used eight samples of normal human parotid gland (methacarn-fixed and frozen sections) to establish if basal cells of striated and excretory ducts have the cytoskeletal protein complement (actin and cytokeratins) of myoepithelial cells. Using a muscle-specific actin, HHF35, not only is the myoepithelium of acini and intercalated ducts stained in all cases, but stellate and spindle shaped cells are also detected all along the inter- and intralobular striated ducts in four of the eight examples. With double-labeled frozen sections and fluorescent microscopy, the actin-specific probe, phalloidin, and the myoepithelial-selective anti-cytokeratin 14 antibody, 312C8-1, confirm that the striated duct does have a population of basal cells with the cytoskeletal protein make-up of myoepithelium. The monoclonal antibody 8.12 (specific for cytokeratin 13 and 16) also stains some basal cells of striated and excretory ducts, as well as luminal cells of ducts at all levels, but does not label the myoepithelium of acini and intercalated ducts. Both the anti-cytokeratin antibodies and the actin-detecting mechanisms reveal that the basal cell population of striated and excretory ducts is more heterogeneous, and likely functionally more complex, than has been realized previously. Such findings are not in agreement with certain aspects of current theories of the histogenesis of salivary gland tumours.

Immunoreactive Metallothionein in Salivary Gland Neoplasms.

“…As duct-like and /or myoepitheliallike cells are the predominant histopathological features of salivary neoplasms, a subpopulation of ductal cells located on the non-luminal aspect of the striated and excretory ducts of human salivary glands with a more heterogeneous and functionally more complex features have been identified by ultrastructural and immunohistochemical studies [7], which in the present study showed consistent immunoreactivity for MT. These cells termed as the ductal basal cells, their nature and function not fully clear at present, have been suggested to share numerous common immunohistochemical markers with the myoepithelial cells and at least some of the ductal basal cells may serve as the progenitor-reserve cells of salivary gland neoplasms, if not all [7,8]. However, in salivary tumors, there is no direct evidence for genesis of neoplastic myoepithelial cells either from the myoepithelial cell itself nor from ductal basal cells.…”

“…A consistent reactivity of MT in salivary tumors in non-luminal cells, the neoplastic myoepithelial cells or their counterparts, in particular, in the majority of the salivary tumors evaluated in the present study may have a potential implication in defining the role of neoplastic myoepithelial cells, believed by many investigators to have a major role in the histomorphology and histogenesis of salivary tumors [9]. As duct-like and /or myoepitheliallike cells are the predominant histopathological features of salivary neoplasms, a subpopulation of ductal cells located on the non-luminal aspect of the striated and excretory ducts of human salivary glands with a more heterogeneous and functionally more complex features have been identified by ultrastructural and immunohistochemical studies [7], which in the present study showed consistent immunoreactivity for MT. These cells termed as the ductal basal cells, their nature and function not fully clear at present, have been suggested to share numerous common immunohistochemical markers with the myoepithelial cells and at least some of the ductal basal cells may serve as the progenitor-reserve cells of salivary gland neoplasms, if not all [7,8].…”

Warthin's Tumour of the Parotid Glands, Adenomatous Hyperplasia and Oncocytic Adenomatous Hyperplasia of the Intranodal Heterotopic Salivary Glands: A Comparative Immunohistochemical Assessment.

“…In the ductal epithelium of normal salivary glands, the antibodies K8.12, PKK1 and KL1 were reactive with the luminal and basal cells in the intercalated, striated and excretory ducts with different reaction intensities. The immunoreactivity of antibody K8.12 was predominantly present in the basal cells, while that of antibodies PKK1 and KL1 was equally present in the luminal and basal cells [3,8,29,39,41]. In prenatally developing salivary glands, ductal basal cells have been found to be similar to those found in the adult glands with respect to the expression of cytokeratins detected by antibodies K8.12 and PKK1 which appears relatively early during the differentiation of larger ducts [21].…”

“…The cytokeratins detected by antibodies K8.12, PKK1 and KL1 have been consistently demonstrated in normal and neoplastic lesions of the salivary glands [3,8,12,23,39,41]. In the ductal epithelium of normal salivary glands, the antibodies K8.12, PKK1 and KL1 were reactive with the luminal and basal cells in the intercalated, striated and excretory ducts with different reaction intensities.…”

Primary Epithelial Tumors of Salivary Glands.Histomorphological and Immunohistochemical Implications.

“…The subpopulation of ductal cells located on the abluminal aspect of excretory and striated ducts of human major and minor salivary glands with a more heterogeneous and functionally more complex features have been identified by ultrastructural and immunohistochemical studies [42] . These cells have been termed as ductal basal cells but studies on their nature and function, not fully clear at present, have suggested that they share numerous common immunohistochemical markers with the myoepithelial cells and at least some of the ductal basal cells, if not all, may serve as the progenitor-reserve cells of salivary gland neoplasms [116].…”