Shh Signaling is Related to BMP Signaling in Ameloblast Differentiation

Objectives: Ameloblast differentiation is initiated and maintained in the epithelial-mesenchymal interaction, where various growth factors are synthesized and they are believed to be related to differentiation of ameloblasts. Sonic hedgehog (Shh) is reported to be involved in development and differentiation of many cells, including ameloblasts. We found that Gli1, which is one of the most important Shh signaling molecules, was essential for amelogenin and ameloblastin synthesis in ameloblast differentiation. The objective of this study was to evaluate the effects of Shh signaling on bone morphogenic protein (BMP) synthesis in ameloblast differentiation.

Methods: Ameloblast-like cells (ALC) were cultured in spinner modified MEM supplemented with 10% FBS and antibiotics. Shh was applied to ALC, and BMP mRNA expression was analyzed by real-time RT-PCR using specific primers for BMPs. Also, Gli1 mammalian expression vector was transfected into ALC, and BMP mRNA expression was evaluated. Ameloblastic differentiation was evaluated by amelogenin and ameloblastin differentiation.

Results: Ameloblastic differentiation was induced by Shh application and enforced Gli1 expression in ALC. Up-regulation of Gli1 expression was observed in Shh treated ALC. BMP expression, especially BMP4, was induced in not only Shh treated ALC but also ALC that was transfected with the Gli1 mammalian expression vector.

Conclusion: Shh signaling was revealed to be involved in BMP synthesis in ameloblast differentiation.