Cytokeratin Expression Patterns in the Rat Respiratory Tract as Markers of Epithelial Differentiation in Inhalation Toxicology. I. Determination of Normal Cytokeratin Expression Patterns in Nose, Larynx, Trachea, and Lung

Abstract

Cytokeratin (CK) polypeptides constitute the intermediate filament cytoskeleton of epithelial cells. The patterns of CK expression can be regarded as specific markers for the epithelial differentiation status. Our objective was to map the cell type-specific CK expression patterns at all representative sites of the respiratory tract of untreated rats to use as a base for the detection of inhalation exposure-related differentiation changes. Using routine paraffin-embedded sections and a panel of well-characterized monoclonal antibodies for immunohistochemistry, we obtained CK staining patterns as follows. Nasal cavity: respiratory epithelium CK18, CK19 (basal, ciliated, nonciliated cells), CK14, and/or CK15 (basal and nonciliated cells); olfactory epithelium CK18 (basal, mid, apical zones and Bowman's glands), CK14, and CK15 (basal zone); squamous epithelium of ventral meatus CK14, CK15 (basal and suprabasal cells), CK1, 10/11, and CK13 (suprabasal cells); glands and columnar epithelia of vomeronasal organ and nasolacrimal duct CK7 and CK13 in addition to respiratory epithelial CK pattern. Trachea: similar to nasal respiratory epithelium with pronounced CK15 and additional CK7. Larynx: CK14, CK15 (basal, ciliated, nonciliated cells), CK8, CK18, CK19 (not in basal cells), CK4, and CK13 (cuboidal and squamoid cells of ventral half). Lung: bronchial epithelium CK14 and CK15 (basal cells only); bronchial and alveolar epithelium CK7, CK8, CK18, and CK19; bronchiolar epithelium similar but less CK8 and no CK7; pleural mesothelium CK7, CK8, and CK19. This inventory of complex CK expression patterns provides the basis for investigating test substance-related effects in inhalation toxicology, e.g., cigarette smoke-induced changes.

Cytokeratin Expression Patterns in the Rat Respiratory Tract as Markers of Epithelial Differentiation in Inhalation Toxicology. II. Changes in Cytokeratin Expression Patterns Following 8-Day Exposure to Room-Aged Cigarette Sidestream Smoke

“…Details of the procedures and the defined section levels are given elsewhere (26). Tissues were removed and fixed in formaldehyde-containing fixatives: nasal cavity in neutral buffered formalin solution followed by decalcification in nitric acid, and lungs with larynx and trachea in ethanolhcetic acid/formaldehyde/saline (15).…”

“…Details of the immunostaining procedure and the individual scoring are given elsewhere (26). Paraffin-embedded sections were dewaxed and immunostained following antigen retrieval by protease or microwave treatment using an antibody panel with defined specificity for rat CK (27) (Table 11).…”

“…Paraffin-embedded sections were dewaxed and immunostained following antigen retrieval by protease or microwave treatment using an antibody panel with defined specificity for rat CK (27) (Table 11). For the evaluation, the epithelia present on the various sections were divided intodefined evaluation compartments (26). Within each compartment, individual scores were given for each distinguishable cell type using 4-stage scores (Table 111) for the staining intensity and the relative distribution of the stained vs the unstained cells of this type.…”

Inhibition of Transforming Growth Factor-β Signaling in Normal Lung Epithelial Cells Confers Resistance to Ionizing Radiation

“…No altered cell morphology and cytoskeletal organization was observed. It is well documented that cytokeratin polypeptides constitute the intermediate filament cytoskeleton of epithelial cells (38). Further, the patterns of cytokeratin expression represent markers of epithelial differentiation status.…”

“…We found that SILECC had an abundant level of cytokeratin suggesting that this normal lung cell culture is of epithelial origin. Abundant staining of cytokeratin found in SILECC using pan-Cytokeratin antibody can also be attributed to the fact that normal lung tissue has been known to harbor expression of various forms of cytokeratin polypeptides (38).…”