Aim: To investigate the effect of HP on NGF production in the presence or absence of TGF-β1 in HDP cells.
Methods: HDP cells were obtained from periodontally healthy and non-carious third molars extracted for orthodontic reasons. HDP cells were exposed to varying magnitudes of HP (0.75-1.4g/cm2) and recombinant human TGF-β1 (2ng/ml) for 6 and 24h. The level of NGF was determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Independent t-test (p<0.05) was used for statistical analysis.
Results: No statistical differences were observed, by means of MTT assay, in HDP cells treated with HP for 24h as compared to normal condition. HP slightly induced NGF, but not TGF-β1, mRNA expression after application of pressure. In contrast to mRNA results, both NGF and TGF-β1 proteins were markedly decreased within 6h after treatment. Application with TGF-β1 could up-regulate NGF in human dental pulp (HDP). Interestingly, up-regulate the NGF production was not observed when cells were treated with TGF-β1 and pressure, simultaneously.
Conclusion: This is the first study to demonstrate an inhibitory effect of HP on both NGF protein and TGF-β1-induced NGF protein, but not mRNA level. This result implicates that pressure may suppress NGF production in the post-transcriptional level. Our study provides the new scope for understanding the effects of hydrostatic pressure on NGF production, which may provide a better understanding in dental pulp response to stimulation.