It is generally known that low-intensity pulsed ultrasound (LIPUS) accelerates peripheral nerve tissue regeneration. However, the precise cellular mechanism involved is still unclear. The purpose of this study was to determine how the Schwann cells respond directly to LIPUS stimuli. Thus, we investigated the effect of LIPUS on cell proliferation, neurotrophin-3 (NT-3), and brain-derived neurotrophic factor (BDNF) mRNA expression in rat Schwann cells. Schwann cells were enzymatically isolated from postnatal 1-3 day rat sciatic nerve tissue and cultured in the six-well plate. The ultrasound was applied at a frequency of 1 MHz and an intensity of 100 mW/cm(2) spatial average temporal average for 5 minutes/day. The control group was cultured in the same way but without the administration of ultrasound. Immunohistochemistry demonstrated that more than 98% of the experimental and control cells were positive for S-100, NT-3, and BDNF. With 5-bromo-2'-deoxyuridine (BrdU) assay, the stimulated cells also exhibited an increase in the rate of cell proliferation on days 4, 7, 10, and 14. Further investigation found that mRNA expression of NT-3 was significantly upregulated in experimental groups compared with the control 14 days after the LIPUS stimulation (the ratio of NT-3/beta-actin was 0.56 +/- 0.13 vs. 0.41 +/- 0.09, P < 0.01), whereas the mRNA expression of BDNF was significantly downregulated in experimental groups compared with the control (the ratio of BDNF/beta-actin was 0.51 +/- 0.05 vs. 0.60 +/- 0.08, P < 0.05). These results demonstrated that the application of LIPUS promotes cell proliferation and NT-3 gene expression in Schwann cells, and involved in the alteration of BDNF gene expression.

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Ossification of the posterior longitudinal ligament of the cervical spine (OPLL) is characterized by the replacement of ligament tissues with ectopic bone formation, and this result is strongly affected by genetic and local factors. Two single nucleotide polymorphisms (SNPs) of rs2273073 (T/G) and rs235768 (A/T) of bone morphogenetic protein 2 (BMP2) gene which are associated with OPLL have been reported in our previous report. In this study, we confirmed the connection in 18 case samples analysis of BMP2 gene in OPLL patients; additionally, it was also shown from the OPLL patients with ligament tissues that enchondral ossification and expression of BMP2 were significantly higher compared with the non-OPLL patients by histological examination, immunohistochemistry and Western blotting analysis. To investigate the underlying mechanism, we studied the effect of SNPs in cell model. The C3H10T1/2 cells with different BMP2 gene variants were constructed and then subjected to uniaxial cyclic stretch (0.5 Hz, 10% stretch). In the presence of mechanical stress, the expression of BMP2 protein in C3H10T1/2 cells transfected by BMP2 (rs2273073 (T/G)) and BMP2 (rs2273073 (T/G), rs235768 (A/T)) were significantly higher than the corresponding static groups (P<0.05). In conclusion, these results suggested that BMP2 gene variant of rs2273073 (T/G) could not only increase cell susceptibility to bone transformation similar to pre-OPLL change, but also increase the sensibility to mechanical stress which might play an important role during the progression of OPLL.