High-frequency noncontact low-intensity pulsed ultrasound modulates Ca2+-dependent transcription factors contributing to cell migration.

Chronic wounds have negative physical and psychological effects on patients and increase the health care burden. Consequently, chronic wound in the elderly population is an important issue. Ultrasound can be a great modality for treating chronic wounds because of its noninvasive and safety characteristics; it can accelerate in vitro and in vivo wound healing. In this study, we developed a novel noncontact ultrasound for wound treatment. We stimulated human epidermal keratinocyte migration using low-intensity pulsed ultrasound (LIPUS) with a noncontact transducer to avoid direct contact with the wound. We also compared the effects of 15-min contact and noncontact transducer stimulation, where a 1-MHz contact transducer (intensity = 40 or 200 mW/cm2) and a 0.45-MHz noncontact transducer (intensity = 30 mW/cm2) were used. Both contact and noncontact LIPUS considerably increased cell migration and activated the calcium (Ca2+)-dependent transcription factors cAMP-responsive element-binding protein (CREB) and nuclear factor of activated T cells (NFAT). Furthermore, noncontact transducer stimulation did not cause cell death or affect cell proliferation but significantly increased the Ca2+ influx-mediated intracellular Ca2+ levels. Ca2+-free medium and Ca2+ channel blockers effectively inhibited LIPUS-induced Ca2+-dependent transcription factor activation and cell migration.

Ca2+ signaling-mediated low-intensity pulsed ultrasound-induced proliferation and activation of motor neuron cells.

Motor neuron diseases (MND) including amyotrophic lateral sclerosis and Parkinson disease are commonly neurodegenerative, causing a gradual loss of nerve cells and affecting the mechanisms underlying changes in calcium (Ca2+)-regulated dendritic growth. In this study, the NSC-34 cell line, a population of hybridomas generated using mouse spinal cord cells with neuroblastoma, was used to investigate the effect of low-intensity pulsed ultrasound (LIPUS) as part of an MND treatment model. After NSC-34 cells were seeded for 24 h, LIPUS stimulation was performed on the cells at days 1 and 3 using a non-focused transducer at 1.15 MHz for 8 min. NSC-34 cell proliferation and morphological changes were observed at various LIPUS intensities and different combinations of Ca2+ channel blockers. The nuclear translocation of Ca2+-dependent transcription factors was also examined. We observed that the neurite outgrowth and cell number of NSC-34 significantly increased with LIPUS stimulation at days 2 and 4, which may be associated with the treatment's positive effect on the activation of Ca2+-dependent transcription factors, such as nuclear factor of activated T cells and nuclear factor-kappa B. Our findings suggest that the LIPUS-induced Ca2+ signaling and transcription factor activation facilitate the morphological maturation and proliferation of NSC-34 cells, presenting a promising noninvasive method to improve stimulation therapy for MNDs in the future.