Histological and immunohistochemical study of gilthead seabream tongue from the early stage of development: TRPV4 potential roles

Background: Taste buds, the morphofunctional units for taste perception, transduce gustatory stimuli using G protein-coupled receptors and a complex arrangement of ion channels, among which TRPV4, a member of the TRP superfamily. Studies on taste buds development on gilthead seabream are unknown, and the TRPV4 expression on fish taste cells studies were conducted only on zebrafish. Methods: In our study, we have investigated the histological features of the gilthead seabream tongue dorsal surface from the earliest stage of development using Masson trichrome with aniline blue staining. Additionally, the TRPV4 expression pattern was studied by means of immunohistochemical labeling and quantitative RT-PCR. Results: We have recorded for the first time on gilthead seabream lingual dorsal surface the presence of, stage-specific, three types of taste buds: type I, type II and type III in larvae, juveniles and adults respectively. At 40 days post-hatching, taste buds were mature-looking. TRPV4 expression was detected in a subpopulation of taste cells of larvae, juveniles, and adults. Furthermore, TRPV4 was expressed in the basal epithelial cells of the tongue at the larvae and juvenile stage, while this expression pattern was more diffused within all the epithelial cell layers in the adult. Conclusion: Our findings presume a taste sensory role of TRPV4 in the three stage-specific taste buds and oral epithelia of gilthead seabream. In addition to its sensory role on the epithelial cell layers, we hypothesize that TRPV4 is implicated in epithelial cells differentiation and membrane protection.