Document Type : Original Research


1 Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

2 Skin and Stem Cells Research Center, Tehran University of Medical Sciences, Tehran, Iran

3 Department of Radiology Technology, Allied Medical Faculty, Shahid Beheshti University of Medical Sciences, Tehran, Iran



Background: Ultrasound waves are considered non-invasive, safe, and mechanical stimuli with unknown mechanisms.
Objective: The aim of this study is to determine the effect of acoustic cavitation interaction according to the mechanical index (MI) on fibroblast cells’ reproducibility and gene expression of collagen Ι as a skin repair agent.
Material and Methods: In this interventional study, the ultrasonic pressure equations were solved to extracted the maximum mechanical indices with frequencies of 150 kHz, 40 kHz, 28 kHz and low intensity (<0.5 W/cm2). Groups were extracted with a mechanical index of 0.10, 0.20, and 0.40. Then, fibroblast cells were exposed to selected acoustic parameters from simulation. After 5 days, the proliferation was measured with an MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay, and collagen Ι expression was quantified.
Results: Increasing reproducibility in the groups of 0.23 W/cm2 with 0.20 mechanical index threshold was calculated at 1.70±0.05 and 1.07±0.04 times higher in continuous and pulse modes compared to the control group. Reducing the proliferation in group 0.40 mechanical index was shown as compared with control and sham groups in pulse mode (P-value<0.05). The collagen Ι expression level of fibroblast cells in groups of control and 0.20 MI were 0.03±0.00 and 0.17±0.05, respectively. The acoustic vibration effects at 0.20 mechanical index have promoted fibroblast cell functions. 
Conclusion: Low-frequency and -intensity ultrasound waves on the mechanical index threshold (cavitation threshold) increases the proliferation of fibroblast cell and the expression of collagen type Ι.