Effect of low-intensity pulsed ultrasound on l929 fibroblasts

Introduction

Ultrasound has proven to be an important therapeutic resource regarding musculoskeletal disease and is routinely used in physical therapy and medicine both therapeutically and diagnostically. The aim of the present study was to analyse the effects with different ultrasound intensities in order to establish the ideal radiation level in cell cultures.

Material and methods

Fibroblast cell cultures were divided into five groups: group I – control (did not receive irradiation); group II – 0.2 W/cm² in pulsed mode at 10% (1 : 9 duty cycle); group III – 0.6 W/cm² in pulsed mode at 10% (1 : 9 duty cycle); group IV – 0.2 W/cm² in pulsed mode at 20% (2 : 8 duty cycle); and group V – 0.6 W/cm² in pulsed mode at 20% (2 : 8 duty cycle). Each group was irradiated with 24-h intervals, observing the following post-irradiation incubation times: 24, 48, 72 and 96 h; after 24 h of each irradiation, cultures were analysed using the MTT method.

Results

Analysis of the results following ultrasound irradiation demonstrated that the effect of ultrasound with 0.6 W/cm² in pulsed mode at 10% (1 : 9 duty cycle) was statistically significant in relation to ultrasonic irradiation in pulsed mode at 20% (2 : 8 duty cycle) (p < 0.05).

Conclusions

According to parameters used in the irradiation of cultivated fibroblasts, the pulse mode regime and the control of intensity are of fundamental importance for the optimal use of therapeutic ultrasound. Furthermore, low and medium intensities decreased cell damage, which establishes that acoustic pulsed energy induces the proliferation of fibroblast cells.