Differential Expression of Taste Receptors in Tongue Papillae of DBA Mouse

The tongue has 4 kinds of papillae, which are filiform, fungiform (FU), foliate (FO) and circumvallate papilla (CV). Tongue papillae except filiform papilla include taste buds. The papillae differ in taste sensitivities, likely due to differential expression of taste receptors. In this study, we evaluated differences in the expression levels of taste receptors in FU, FO and CV. Male DBA2 mice, 42-60 days old, were used in the study. Messenger RNAs were extracted from the murine epithelial tissues including FU, FO and CV. Cloned DNAs were synthesized by reverse transcription. Quantitative PCRs (qPCRs) were performed to determine mRNA expression levels of taste receptors. Results of qPCR revealed that the relative expression levels and patterns were different among FU, FO and CV. All three type 1 taste receptors were expressed FU, FO and CV at varying relative expression levels. All 35 kinds of type 2 taste receptors showed higher expression in FO and CV than in FU. Tas2r108 and Tas2r137 showed the two highest expression levels in all tested papillae. The differential expression levels and patterns of taste receptors among the three papillae could contribute to the different physiological sensitivities by tongue areas. Additional studies such as in situ hybridization or taste receptor cell activity recording is necessary to elucidate the functional relationship between expression levels of taste receptors and taste sensitivity.

Immunohistochemical Study of the Expression of NCAM in the Fungiform Papilla of the Young Rat Tongue Following Single Dose Radiation / 대한해부학회지

Radiotherapy in the treatment of head and neck cancers is often used either alone or in addition to surgery. Radiation disrupts the proliferative capacity of the cancer while doing as little damage as possible to the normal tissue. Nevertheless, conventional radiotherapy of advanced head and neck tumors is frequently associated with severe oropharyngeal mucositis. The fungiform papillae are found on the dorsal surface of the anterior 2/3 of the tongue and have one taste bud which always located on the superior side. In recent years, many study have demonstrated the location of neuropeptides in the intragemmal cells of the taste buds. We used neural cell adhesion molecule (NCAM) in this study. NCAM is a membrane surface glycoprotein found in neural tissue that functions in cell -cell interactions such as adhesion and recognition and may contribute to neuronal and receptoneural synaptogenesis. However, to the best of our knowledge, there is no study about NCAM in relation to dysgeusia, especially after radiotherapy. Therefore, we studied the change of the expression of NCAM in the fungiform papilla of the young rat tongue following single dose radiation. Twenty days old 18 Sprague -Dawley rats were used. Twelve rats were irradiated with a single dose of 17 Gy gamma radiation. We sacrificed rats 1, 7, 20 days after radiation. The anterior part of tongues were removed and cut into at 30 micro gram on a cryocut. Using the free floating method, we immunostained sections. In control group, NCAM is expressed on some intragemmal cells which were located in the center of the bud and intragemmal nerve fibers. NCAM -immunoreactive (ir) perigemmal nerve fibers were rare, however basal plexus fibers and subpapillary nerve bundle showed strong immunoreactivity. One day after radiation, taste buds had no detectable changes of the expression of NCAM. However, seven days after radiation, the number of NCAM -ir intragemmal cells was reduced and the shape of ir cells was deformed. Immunoreactivity of basal plexus fibers and subpapillary nerve bundle was also decreased. The surface of the papilla was transformed into dome shape. Twenty days after radiation, overall forms of buds were recovered except a few deformed NCAM -ir intragemmal cells. NCAM was expressed in the intragemmal cells which are thought to be related with taste sensation, and we speculate that NCAM participate synaptogenesis. However, more studies using immunoelectron microscopic method are required.