Application of ultrasound stimulation in bone tissue engineering.

Many studies have been investigated on the effects of the low-intensity pulsed ultrasound (LIPUS) on bone healing, acceleration of bone mineralization and regeneration. Many researchers have focused on a more comprehensive understanding of the biological mechanism of the osteoblast by LIPUS because the osteoblast is an important cell in bone formation. The effects of LIPUS on the proliferation, gene expression of Runx2, Msx2, Dlx5, and AJ18, and the second messenger signaling of osteoblast were reported. Various parameters of LIPUS, such as intensity, frequency, duration and topology, were investigated to find appropriate conditions in osteoblast. Less than 120 mW/cm(2) of intensity and 1-3 MHz of frequency were considered good condition for regeneration of bone tissue. Increased osteoblast cells and higher mineralized nodule formation explain the enhancement of proliferation by LIPUS. In addition, LIPUS affects on differentiation of osteoblast cells, which is shown by increased ALPase, and transcriptional factors, Runx2. Ultrasound stimulates PEG2 and COX-2 in osteoblast, and the signals accelerates the bone regeneration in tissue engineering.