Growth and regeneration of sympathetic neuron axons induced by pulsed low intensity ultrasound

Abstract

Over a quarter million Americans are currently living with spinal cord injuries (SCIs), costing $3 billion a year to manage [1]. SCI results in myelin loss, axonal degradation, and death of sympathetic neurons, leading to lesion formation and disruption of the primary communication pathway in the spinal cord. Low intensity ultrasound has been shown to improve axonal regeneration in the peripheral nervous system, but its effect on cells in the central nervous systems is not yet studied. The objective of this work is to investigate the growth-stimulating effects of low to mid-intensity ultrasound on axons of sympathetic neurons. To find optimal ultrasound intensities, neuroendocrine-type PC-12 cells were cultured and treated with pulsed ultrasound at varying intensities. Cells were cultured in deprived states to model a post-SCI environment, while being treated with neurotrophic factor (NGF) to induce their neuron differentiation. Images of cells were analyzed for number of cells and neurite outgrowth. Experiments with PC-12 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 ultimate goal is to develop an effective, noninvasive SCI treatment based on the ultrasound technology.