TGF-beta 3 is expressed in taste buds and inhibits proliferation of primary cultured taste epithelial cells

Transforming growth factor-beta s (TGF-beta s), expressed in various tissues, play important roles in embryonic development and adult tissue homeostasis through their effects on cell proliferation, cell differentiation, cell death, and cell motility. However, expression of TGF-beta signaling components and their biological effect on taste epithelia has not been elucidated. We performed expression analysis of TGF-beta signaling components in taste epithelia and found that the TGF-beta 3 mRNA was specifically expressed in taste buds. Type II TGF-beta s receptor (T beta R-II) mRNA was specifically expressed in the tongue epithelia including the taste epithelia. To elucidate the biological function of TGF-beta 3 in taste epithelia, we performed proliferation assay with primary cultured taste epithelial cells. In the presence of TGF-beta 3, percentage of BrdU-labeled cells decreased significantly, suggesting that the TGF-beta 3 inhibited the proliferation of cultured taste epithelial cells through inhibiting cell-cycle entry into S phase. By quantitative reverse transcription-polymerase chain reaction assay, we found that the TGF-beta 3 resulted in an increased level of expression of p15Ink4b and p21Cip1, suggesting that the TGF-beta 3 inhibited the taste epithelial cell proliferation through inhibiting G1cyclin-Cdk complexes. Taken together, these results suggested that the TGF-beta 3 may regulate taste epithelial cell homeostasis through controlling cell proliferation.