Cytokeratin polypeptide expression during the histogenesis of guinea pig submandibular salivary gland

Interlobular excretory ducts of mammalian salivary glands: structural and histochemical review

In the major salivary glands of mammals, excretory ducts (EDs) succeed striated ducts. They are for the most part interlobular in position, although their proximal portions sometimes are on the periphery of a lobule, where they occasionally retain some of the structural features of striated ducts. Based on a survey of a broad range of mammalian species and glands, the predominant tissue type that composes EDs is pseudostratified epithelium. In some species, there is a progression of epithelial types: the proximal EDs are composed of simple cuboidal or columnar epithelium that, in the excurrent direction, usually gives way to the pseudostratified variety. Secretory granules are visible in the apical cytoplasm of the principal cells of the EDs of only a few species, but histochemistry has shown the presence of a variety of glycoproteins in these cells in a spectrum of species. Moreover, the latter methodology has revealed the presence of a variety of oxidative, acid hydrolytic, and transport enzymes in the EDs, showing that, rather than simply acting as a conduit for saliva, these ducts play a metabolically active role in gland function. It is difficult to describe a "typical" mammalian ED because it can vary along its length and interspecific variation does not follow a phylogenetic pattern. Moreover, in contrast to intercalated and striated ducts, ED cellular features do not exhibit a relationship to diet.

Immunocytochemistry of myoepithelial cells in the salivary glands

MECs are distributed on the basal aspect of the intercalated duct and acinus of human and rat salivary glands. However, they do not occur in the acinus of rat parotid glands, and sometimes occur in the striated duct of human salivary glands. MECs, as the name implies, have structural features of both epithelial and smooth muscle cells. They contract by autonomic nervous stimulation, and are thought to assist the secretion by compressing and/or reinforcing the underlying parenchyma. MECs can be best observed by immunocytochemistry. There are three types of immunocytochemical markers of MECs in salivary glands. The first type includes smooth muscle protein markers such as alpha-SMA, SMMHC, h-caldesmon and basic calponin, and these are expressed by MECs and the mesenchymal vasculature. The second type is expressed by MECs and the duct cells and includes keratins 14, 5 and 17, alpha 1 beta 1 integrin, and metallothionein. Vimentin is the third type and, in addition to MECs, is expressed by the mesenchymal cells and some duct cells. The same three types of markers are used for studying the developing gland. Development of MECs starts after the establishment of an extensively branched system of cellular cords each of which terminates as a spherical cell mass, a terminal bud. The pluripotent stem cell generates the acinar progenitor in the terminal bud and the ductal progenitor in the cellular cord. The acinar progenitor differentiates into MECs, acinar cells and intercalated duct cells, whereas the ductal progenitor differentiates into the striated and excretory duct cells. Both in the terminal bud and in the cellular cord, the immediate precursors of all types of the epithelial cells appear to express vimentin. The first identifiable MECs are seen at the periphery of the terminal bud or the immature acinus (the direct progeny of the terminal bud) as somewhat flattened cells with a single cilium projecting toward them. They express vimentin and later alpha-SMA and basic calponin. At the next developmental stage, MECs acquire cytoplasmic microfilaments and plasmalemmal caveolae but not as much as in the mature cell. They express SMMHC and, inconsistently, K14. This protein is consistently expressed in the mature cell. K14 is expressed by duct cells, and vimentin is expressed by both mesenchymal and epithelial cells. After development, the acinar progenitor and the ductal progenitor appear to reside in the acinus/intercalated duct and the larger ducts, respectively, and to contribute to the tissue homeostasis. Under unusual conditions such as massive parenchymal destruction, the acinar progenitor contributes to the maintenance of the larger ducts that result in the occurrence of striated ducts with MECs. The acinar progenitor is the origin of salivary gland tumors containing MECs. MECs in salivary gland tumors are best identified by immunocytochemistry for alpha-SMA. There are significant numbers of cells related to luminal tumor cells in the non-luminal tumor cells that have been believed to be neoplastic MECs.

Myoepithelium of salivary glands

In salivary glands and other exocrine organs, there are starfish-shaped cells that lie between the basal lamina and the acinar and ductal cells. These have structural features of both epithelium and smooth muscle cells, and so are called myoepithelial cells. Their functions include contraction when the gland is stimulated to secrete, compressing or reinforcing the underlying parenchymal cells, thus aiding in the expulsion of saliva and preventing damage to the other cells. They also may aid in the propagation of secretory and other stimuli. Their common developmental origin with the basal cells of the larger ducts is displayed in the mature glands by shared structural and immunohistochemical features, but most such basal cells do not have the distinguishing features of myoepithelial cells, such as myofibrils. Although myoepithelial cells can be identified by light microscopy through enzyme histochemistry and special stains and immunohistochemistry for their myofibrils, these techniques can be misleading in salivary gland neoplasms. Thus, the most reliable means of identifying neoplastic myoepithelial cells is with a combination of histochemistry and electron microscopy. The extent to which these cells are derived from undifferentiated stem cells in both normal and neoplastic growth is controversial. The presentation here of transmission electron microscopy (TEM) of well-differentiated myoepithelial cells in mitotic division indicates that stem cells are not necessarily the only source of myoepithelial cells in the later stages of salivary gland development or in neoplasia.

Immunocytochemical characterization of lung tumors in fine-needle aspiration. The use of cytokeratin monoclonal antibodies for the differential diagnosis of squamous cell carcinoma and adenocarcinoma

In the current study, immunocytochemical typing of intermediate filaments was used for a differential diagnosis of human lung tumors from transthoracic fine-needle aspiration biopsies (TFNAB). The authors have compared the cytologic diagnosis of 53 lung cancer cases with the immunofluorescence patterns obtained using a panel of monoclonal antibodies, five of which (KG 8.13, KM 4.62, Ks B.17, KS 8.12, KK 8.60) react with specific cytokeratin polypeptides and one with vimentin (VIM 13.2). Only in six of 23 samples cytologically diagnosed as squamous cell carcinoma did the immunocytochemical typing of cytokeratins (ICTC) confirm the cytologic diagnosis. In seven cases some of the tumor cells stained positively with antibody Ks B.17 specific for simple epithelial keratin (No: 18), suggesting the presence of some cells of glandular origin. In ten additional cases the ICTC was in conflict with the cytologic diagnosis of squamous cell carcinoma (i.e., antibodies Ks 8.12 and KK 8.60 were negative, and antibody Ks B.17, positive) supporting a diagnosis of adenocarcinoma. In 14 of 18 cases cytologically diagnosed as adenocarcinoma, the ICTC confirmed the diagnosis whereas in four cases additional presence of some squamous cells was noticed. The ICTC labeling of cases cytologically diagnosed as undifferentiated and large cell carcinomas was similar to that of the group of adenocarcinomas. Thus, the application of cytokeratin typing for TFNAB samples seems to provide a vital complementation to routine cytologic study, especially for cases cytologically diagnosed as squamous carcinoma.

Prenatal development of human major salivary glands and immunohistochemical detection of keratins using monoclonal antibodies

The major salivary glands were examined from 69 human fetuses ranging from 10 to 40 weeks of gestation. Prenatal growth curves of developing salivary glands could be established by histological scoring, and development was divided into the early developmental stage (EDS) from 10 to 18 weeks, early intermediate developmental stage (EIDS) from 19 to 24 weeks, late intermediate developmental stage (LIDS) from 15 to 32 weeks, late developmental stage (LDS) from 33 to 40 weeks. Characteristic morphogenesis and cytodifferentiation occurred in glandular duct cells during the period of EIDS and LIDS. In the LDS, acini and ducts of the salivary glands histologically developed into a mature state similar to adult glands. Immunohistochemical staining with monoclonal antibodies (MoAbs) PKK1, KL1, K8.12, K8.13, K4.62, RPN 1160, 1162, 1163, 1164, and 1165 was performed. During the fetal period, keratin expression as revealed by MoAbs PKK1, KL1, K8.12 was well established, and the staining pattern for each of these antibodies was comparable. Other antibodies showed rare or negative staining except K8.13 which had a diffuse, non-specific staining pattern. Accordingly, the proliferation and cytodifferentiation of fetal stage keratin staining in ductal cells as revealed by MoAbs PKK1, KL1, and K8.12 showed a heterogenic distribution in both luminal and basal cells. It is a characteristic finding that the cytodifferentiation of ductal luminal cells precedes ductal basal cells. Ductal basal cells stained with MoAb K8.12 and show heterogeneity of keratin distribution continuously until the full term of gestation. The keratin staining of oral epithelium was also examined to compare with distribution of salivary gland ductal cells and oral epithelial cells. In the present study, the developmental sequence of salivary gland cells and the immunohistochemical properties of keratin proteins in these cells were described in relation to the histogenesis of salivary gland tumours.

Modulation of intermediate-filament expression in developing cochlear epithelium

The present study was designed to characterize the expression and distribution of intermediate filaments (IFs) in the diverse cellular elements of inner-ear epithelium in guinea pig and man. Using immunofluorescence microscopy with a battery of IF-specific monoclonal antibodies, we show that the epithelium of the otocyst expresses cytokeratin (CK) polypeptides typical of simple epithelia. Cells in the early otic ganglion were also positively labelled for cytokeratins, suggesting that they are of otocystic epithelial origin. Cytokeratin distribution was largely homogeneous in the early cochlear duct as the epithelium differentiated, differences in the distribution of cytokeratin between the various cell types became detectable. Characteristically, cochlear hair cells became devoid of cytokeratin labelling, and remained unlabelled with antibodies specific for all other IF classes. The neural tissue of the inner ear was also devoid of cytokeratins and was typically positive for neurofilaments. Vimentin IFs were abundant in the mesenchymal tissues around the membranous labyrinth. Desmin and glial fibrillary acidic protein were not detectable in the cochlea. The apparent absence of all IFs from the cochlear hair cells in both guinea pig and man, as revealed by immunofluorescence and electron microscopy, and the possible significance of their absence for cochlear physiology, are discussed.