Osteogenic Differentiation of Rat Bone Marrow Stromal Cells by Various Intensities of Pulsed Ultrasound

Introduction Bone growth and repair are under the control of biochemical and mechanical signals. Changes in the tissue strains caused by mechanical stimuli induce production and actions of biochemical signals in the local environment to promote new bone formation [1-3]. One such mechanical stimulus of low-intensity pulsed ultrasound (LIPUS) is a clinically used intervention for accelerating healing of fractures and non-unions. While the FDA approved intensity of 30mW/cm is used clinically, the actual intensity experienced by the cells at the target site is unknown. It is reasonable to assume that the soft tissues around the repair site attenuate the delivered LIPUS signal and the target cells are exposed to intensities below the applied dose. The aim of this study was to investigate intensities below 30mW/cm of LIPUS able to provoke phenotypic responses in bone cells. In order to address this question, we studied the effect of 2, 15 and 30mW/cm LIPUS in rat bone marrow-derived stromal cells (rBMSC) at early (intracellular signaling), middle (alkaline phosphates activity) and late (mineralization) stages of osteogenic differentiation.