Low-intensity pulsed ultrasound induces proliferation of human neural stem cells

Abstract

Background

Low-intensity pulsed ultrasound (LIPUS) has been highlighted as a potential therapy for tissue repair and regeneration. However, little is known about LIPUS effects on neuromodulation. This research was conducted to study LIPUS effect on the proliferation of human neural stem cells.

Materials and methods

The human SH-SY5Y neuroblastoma cell line was used as a neural stem cell model. The well-documented SH-SY5Y neurogenic protocol, which involves treatment with all trans-retinoic acid (ATRA) for 5 days and then brain-derived neurotrophic factor (BDNF) for 7 days, was used to synchronise the growth cell cycle to G1 phase of the cell cycle before proliferation testing. Subsequently, the neural stem cells were then treated with single or triple 20-min LIPUS exposures (Intensity I_SATA: 60 mW/cm², frequency: 1.5 MHz, pulse repetition: 100 Hz, and duty cycle: 20%). Cell proliferation was analysed using cell counting of β-tubulin and neurofilament medium-positive neural stem cells, Ki67-cell proliferation marker and metabolic-based assays (cell counting kit-8 and alamarBlue). The involvement of ERK signalling was investigated by quantification of phospho-ERK1/2 levels and cell proliferation with and without MEK/ERK inhibitor (U0126).

Results

The results show that LIPUS exposure(s) induced cell proliferation, as evidenced by an increase in the numbers of neural stem cells. ERK signalling is involved in LIPUS-induced neural stem cell proliferation, as evidenced by concurrent inhibition of LIPUS-induced phospho-ERK levels and cell proliferation in the presence of the MEK/ERK inhibitor.

Conclusion

This study provides original evidence that LIPUS can stimulate neural stem/progenitor cell proliferation. LIPUS may be suggested as a sole or an adjunct therapeutic application to promote the neural stem cell pool in stem cell therapies and tissue engineering approaches for nerve repair and regeneration for the management of traumatic nerve injuries and regenerative endodontic treatment.