Morphology and distribution of Clara cells in the airway epithelium of common marmosets (Callithrix jacchus)

Numeros experimental studies indicate that clara cells play an important roll in the airway epithelium. Investigantions on the morphology and tracheobronchial distribution aof Clara cells help to gain further insights into the function of Clara cells and their role in the regulation of inflammatory processes and regeneration of bronchial epithelium. The common marmoset (Callithrix jacchus) is a nonhuman primate of increasing interest for use as an model respiratory tract of human diseases. Thus, it was the objective of our investigation to access the morphology and distribution of Clara cells and to distinguish them from other nonciliated cells (goblet cells, neuroendocrine cells) in the respiratory tract of this nonhuman primate species by means of light microscopy, immunohistochemistry, and transmission and scanning electron microscopy. Immunohistochemical markers included human Clara cell protein CC-10 and surfactant precursor protein B. For the identification and differentiation of other nonciliated cells, immunohistochemical staining with neuron-specific enolase (NSE) and a mucin-antibody (MUC 1) was performed. Clara cells presented typical electron dense granules of varying diameter.

Secretion seemed to be associated with constrictions of the apical cytoplasm. Clara cells could be detected from trachea to terminal bronchiole, whereas goblet cells are sparse. Our results indicate that Clara cells are the most important nonciliated cells of the conducting airways and guarantee, together with ciliated cells, the mucociliary clearance mechanism of the respiratory tract.