Immunohistochemical characterization of brush cells in the rat larynx.

The immunohistochemical characteristics of brush cells in the laryngeal mucosa were examined using immunohistochemistry for various immunohistochemical cell markers including villin at the light and electron microscopic levels. Cells that were immunoreactive to villin were barrel-shaped with thick cytoplasmic processes extending toward the lumen of the laryngeal cavity. Immunoelectron microscopic observations revealed thick and short microvilli with long rootlets of microfilaments. Numerous small clear vesicles and small finger-like cytoplasmic processes were observed in the apical process and lateral membrane, respectively. Double immunofluorescence showed villin-immunoreactive cells were not immunoreactive for the markers of solitary chemosensory cells, GNAT3 and phospholipase C, β2-subunit (PLCβ2), or for that of neuroendocrine cells, synaptosome-associated protein 25kD. Furthermore, immunoreactivities for cytokeratin 18 (CK18) and doublecortin like-kinase 1 in the perinuclear cytoplasm of villin-immunoreactive cells. However, some CK18-immunoreactive cells were immunoreactive to GNAT3 but not to villin. Regarding sensory innervation, only a few intraepithelial nerve endings with P2X3, SP, or CGRP immunoreactivity attached to villin-immunoreactive cells. In the present study, brush cells in the rat laryngeal mucosa were classified by immunoreactivity for villin, and were independent of other non-ciliated epithelial cells such as solitary chemosensory cells and neuroendocrine cells.