Detection of neurotrophic factors in taste buds by laser capture microdissection, immunohistochemistry, and in situ hybridization

Neurotrophic factors are thought to function in the survival and maintenance of the taste buds and nerve fibers innervating them. Laser capture microdissection (LCM) coupled with the reverse transcription polymerase chain reaction (RT-PCR) was performed to detect the mRNA of neurotrophic factors and their receptors in the taste buds of adult mouse circumvallate papillae. Results showed mRNAs of the ciliary neurotrophic factor (CNTF), its receptor (CNTFR), glial cell line-derived neurotrophic factor (GDNF), GDNF family receptors α-1 (GFR α-1), GFRα-2, and RET tyrosine kinase receptor (RET), neurotrophin (NT)3, NT4/5, tyrosine kinase (Trk) C, nerve growth factor (NGF), and TrkA were expressed in the isolated taste buds. Among these neurotrophic factors, GDNF, GFR α-1, GFR α-2, NT3, NT4/5, NGF, and TrkA were previously found in the taste buds immunohistochemically and were detected at the mRNA level in the present study. The present immunohistochemical study revealed that CNTF, CNTFR, and the RET tyrosine kinase receptor, which binds GDNF family/ receptor complexes, were also expressed in the taste buds. However, by in situ hybridization, mRNAs of CNTF and RET were not detected in the taste buds from adult mice although they were found in those from early postnatal mice. CNTFR mRNA did not show any specific pattern in the taste buds. Moreover, mRNA expressions of NT4/5 and TrkC was re-examined by in situ hybridization; however no specific pattern was found for them in the taste buds. In summary, LCM is a useful tool for the detection of a relatively small amount of mRNA, such as that of neurotrophic factors and receptors in the taste buds.