Therapeutic Ultrasound Stimulates MC3T3-E1 Cell Proliferation Through the Activation of NF-κB1, p38α, and mTOR

Background and Objectives: As the population ages, osteometabolic diseases and osteoporotic fractures emerge, resulting in substantial healthcare resource utilization and impaired quality of life. Many types of mechanical stimulation have the potential of being recognized by bone cells after a mechanical sign is transformed into a biological one (a process called mechanotransduction). The therapeutic ultrasound (TU) is one of several resources capable of promoting bone cell mechanical stimulation. Therefore, the main purpose of present study was to evaluate the effect of TU on the proliferation of pre-osteoblasts using in vitro bioassays. Study Design/Materials and Methods: We used MC3T3-E1 pre-osteoblast lineage cells kept in Alpha medium. Cells were treated using pulsed mode therapeutic ultrasound, with frequency of 1MHz, intensity of 0.2 W/cm(2) (SATA), duty cycle of 20%, for 30 minutes. Nifedipine and rapamycin were used to further investigate the role of L-type Ca2+ channels and mTOR pathway. Intracellular calcium, TGF-beta 1, magnesium, and the mRNA levels of osteopontin, osteonectin, NF-kappa B1, p38 alpha were evaluated. Results: The results show that TU stimulates the growth of MC3T3-E1 cells and decreases the supernatant calcium and magnesium content. Also, it increases intracellular calcium, activates NF-kappa B1 and mTOR complex via p38 alpha. Moreover, TU promoted a decrease in the TGF-beta 1 synthesis, which is a cell growth inhibitor. Conclusions: Therapeutic ultrasound, with frequency of 1MHz, intensity of 0.2 W/cm(2) (SATA) and pulsed mode, for 30 minutes, was able to increase the proliferation of preosteoblast-like bone cells. This effect was mediated by a calcium influx, with a consequent activation of the mTOR pathway, through increased NF-kappa B1 and p38 alpha. (C) 2015 Wiley Periodicals, Inc.