The tracheobronchial epithelium of the bonnet monkey (Macaca radiata): A quantitative ultrastructural study

Abstract

Since there are major differences between the airway epithelium of man and that of common laboratory species, the tracheobronchial epithelium of the bonnet macaque was characterized to evaluate its usefulness as a model for study of human conducting airways. This study compared the light microscopic, scanning electron microscopic, and ultrastructural appearance of epithelium from the posterior membranous and anterior cartilaginous trachea and mainstem bronchus. Population densities, epithelial volumetric densities, and frequency distributions of cross-sectional areas of nuclei were determined for cell types present on electron micrographs. Four epithelial cell types were distinguished by ultrastructural criteria. Basal cells were 31% of the population and were similar to those described in other species. Ciliated cells were also similar to those of other species and composed 41% of the population; their nuclei were larger than those of other cell types. Mucous goblet cells had large numbers of secretory granules with electron-dense cores and a lucent periphery. They were only 8% of the population by nuclear count but composed 20% of the epithelial volume. The fourth cell type had multiple small vesicles containing small amounts of granular material and was termed a "small mucous granule cell." Small mucous granule cells (16% of the population) were present in greater numbers than mucous goblet cells but were a smaller proportion of the epithelial volume (8%). While population densities of cell types determined from transmission electron micrographs did not vary between sample sites, scanning electron microscopy demonstrated longitudinal streaks of secretory cells in the posterior trachea suggesting that regional differences in epithelial organization exist. We conclude that the macaque extrapulmonary airway epithelium differs from published descriptions of laboratory rodents in both cell types present and relative abundance of those cell types. Although detailed quantitative studies of human extrapulmonary airways are not available, the primate airways resemble those of man in both the types of cells present and the complexity of pseudostratification.

Epithelial Cells of Trachea and Bronchi

“…Bonnet monkey (M. radiata) (Wilson et al, 1984) Sheep (Mariassy and Plopper, 1983;Evans et al, 1989) 5 41e57 (Evans et al, 1989); 59 AE 7 a 6 4 0AE 3 8 3 2 AE 4 a 6 30AE 5 a Pig (Pavelka et al, 1976) 5 4 6 AE 5 3 3 5 e50 (Pavelka et al, 1976) e e e e…”

“…Up to 60% of the mucous cell profile is occupied by membrane-bound secretory granules (Mariassy and Plopper, 1984;Wilson et al, 1984;Rhodin, 1966;Plopper et al, 1983c). These granules vary in their morphologic and histochemical properties.…”

“…In general, a positive correlation exists between the animal size and epithelial height and a negative correlation is found between animal size and airway generation number. Additional variations of the epithelial thickness are known to occur in the trachea when cartilaginous and membranous regions are compared (Wilson et al, 1984). The histochemistry and cytochemistry of the tracheobronchial tree is reviewed in greater detail in Chapter 5.…”

“…Mouse (Pack et al, 1980;Evans et al, 1989) 6 11e14 (Evans et al, 1989) (Wilson et al, 1984). Basal cell: The basal cell is a relatively small (5e15 m), dense, pleomorphic, low polygonal cell.…”

Tracheobronchial epithelium in the adult rhesus monkey: A quantitative histochemical and ultrastructural study

“…Also, the epithelium of respiratory bronchioles is clearly demarcated into two zones of distinctly different epithelial populations. One of these is a pseudostratified columnar epithelium with mucous, basal, and ciliated cells resembling the trachael epithelium of macaques (Castleman et al, 1975;Wilson et al, 1984) and the other a simple cuboidal epithelium composed of Clara cells. The present study was designed to characterize the tracheobronchial epithelium throughout the conducting airway tree in one species on nonhuman primate, the rhesus monkey.…”