Cell specific ultrasound effects are dose and frequency dependent

Ultrasound is widely used in clinical practice, mostly in diagnostic studies, but increasingly in therapeutic applications as well. This may be the case in acceleration of wound healing or treatment of cancer. Still, little is known about the direct effect of frequency or energy density of the ultrasound upon the cells themselves. We therefore investigated the impact of three different protocols using high, medium and low energy densities at three different frequencies on normal endothelial and epithelial as well as carcinoma cell lines (neuroblastoma and adenocarcinoma cell lines). Proliferation of endothelial and epithelial cell lines was significantly increased depending on the frequency and energy density applied. No influence on actin cytoskeleton formation was seen in these cells after treatment, while a significant decrease in the density of microvilli and the length of filopodia in the epithelial cell line could be noted. The proliferation rate of the carcinoma cell lines was reduced and cells destroyed. Apoptosis was induced in the adenocarcinoma cells after ultrasound exposure. Additionally, the expression of neurofilament was increased in neuroblastoma cells as evidence of beginning differentiation. So, different settings of frequency and energy density in an ultrasonic treatment protocol lead to different impacts on proliferation, morphology and differentiation and might be used to stimulate or inhibit the growth of individual cell types.