Over a quarter million Americans are currently living with spinal cord injuries (SCIs), costing $3 billion a year to manage. Unlike most cells, neurons are terminally differentiated, making them unable to regenerate or repair themselves. Therefore, when a lesion occurs and disrupts the primary communication pathway in the spinal cord, it can result in myelin loss, axonal degradation, and cell death. Current treatments are unable to stimulate nerve regeneration, but low intensity ultrasound has been shown to improve rate of peripheral nervous system regeneration. The objective of this study is to investigate the growth-stimulating effects of low to mid-intensity ultrasound on cortical axons. Cancer cells, cortical neurons, and neuroendocrine cells were cultured and treated with ultrasound at varying intensities. Cancer cells and cortical neurons were cultured in deprived states to model a post-spinal cord injury environment, while neuroendocrine cells were cultured in complete media. Images of cells were analyzed for number of cells and neurite outgrowth. Cancer cell experiments found that the optimal ultrasound intensity ranged between 0.42 and 0.59 W/cm2 to produce the greatest cellular proliferation when compared to greater intensities and the negative control. Experiments with cortical neurons produced similar results, as the optimal intensity was found to be 0.59 W/cm2. Experiments with neuroendocrine cells found that an ultrasound intensity of 1.02 W/cm2 led to optimal neurite outgrowth when analyzing the rate of neurite outgrowth and total neurite outgrowth at the final day of experimentation. Our goal is to provide the foundation to ultimately develop an effective, noninvasive spinal cord injury treatment.
