Influence of Low-Intensity Pulsed Ultrasound Stimulation on Expression of Bone-Related Genes in Rat Bone Marrow Cells

Low-intensity pulsed ultrasound (LIPUS) is used in physiotherapy and bone fracture healing. Previously we demonstrated that LIPUS enhances bone formation around dental implants inserted into rabbit femur. Here, we present the effect of LIPUS treatment on cell proliferation, alkaline phosphatase (ALPase) activity, and the expression of bone-related genes in bone marrow cells. Cell proliferation was not affected by LIPUS treatment. ALPase activity was increased on day 6 after LIPUS treatment in cells treated with 40 mW/cm(2) ultrasound. Evaluation of gene expression in rat bone marrow cells treated with 40 mW/cm(2) ultrasound demonstrated a shift in the expression of genes associated with bone formation; Cox-2 gene expression was increased 30 min after 5- or 20-mM LIPUS treatment. BMP-2 gene expression increased 30 min after 5-mM LIPUS treatment or 6 h after 10-mM LIPUS treatment. Cbfal/Runx2 gene expression increased 30 mm after 20-mM LIPUS treatment. These results suggest that the clinical application of LIPUS for dental implants may promote osseointegration through the activation of bone-related genes.