Abstract: Objective It is generally known that low-intensity pulsed ultrasound(LIPUS) accelerates peripheral nerve tissue regeneration. However, the precise cellular mechanism is still unclear. The purpose of this study was to determine how the Schwann cells respond directly to LIPUS stimuli. Methods Schwann cells were enzymatically isolated from postnatal 1-3 day rat sciatic nerve tissue and cultured in a 6-well plate. The ultrasound was applied at a frequency of 1 MHz and an intensity of 100mW/cm² spatial average temporal average(ISATA) for 5 min/day. The control group was cultured in the same way but without an administration of ultrasound. We investigated the effect of LIPUS on cell proliferation, neurotrophin-3(NT-3) and brain-derived neurotrophic factor(BDNF) mRNA expression by the methods of BrdU uptake, immunohistochemistry and RT-PCR. Results Immunohistochemistry demonstrated that more than 98% of the cultured cells were positive in S-100, NT-3 and BDNF. Stimulated cells also revealed an increased rate of cell proliferation by using 5-bromo-2'-deoxyuridine(BrdU) assay. The mRNA expression of NT-3 by RT-PCR assays was significantly up-regulated at day 14 after the LIPUS stimulation, whereas, the mRNA expression of BDNF was significantly down-regulated. Conclusion These results suggested that the application of LIPUS can promote cell proliferation and NT-3 gene expression, and down-regulates BDNF gene expression in Schwann cells. The signal-regulated mechanisms involved in this process remains unclear and requires further research.

Key words: low-intensity pulsed ultrasound, Schwann cell, proliferation, neurotrophin-3, brain-derived neurotrophic factor