Low-Intensity Pulsed Ultrasound Promotes Osteogenic Differentiation of Reamer-Irrigator-Aspirator Graft-Derived Cells in Vitro.

Recently, reamer-irrigator-aspirator (RIA) systems have been increasingly used to harvest autologous bone grafts. RIA graft materials contain bone marrow, which provides a viable source to derive large numbers of mesenchymal stem cells. Low-intensity pulsed ultrasound (LIPUS) significantly accelerates the differentiation of stem cells derived from bone marrow. This in vitro study investigated the effect of LIPUS on the osteogenic activity and differentiation of RIA graft-derived cells. A small amount of RIA graft was obtained from seven patients. After the cells derived from RIA grafts were cultured, they were divided into two groups: the LIPUS and control groups. LIPUS was applied once daily for 20 min (1.5 MHz, pulse duration: 200 µs, pulse repetition rate: 1 kHz, spatial average-temporal average intensity: 30 mW/cm2). Alkaline phosphatase activity (113.4% and 130.1% on days 7 and 14), expression of osteoblast-related genes (ALP, Runx2) and mineralization (135.2% on day 21) of the RIA graft-derived cells were significantly higher in the LIPUS group than in the control group. However, LIPUS did not affect the cell proliferation of RIA graft-derived cells. This study indicates that LIPUS may enhance the healing of non-union and critical bone defects treated by autologous bone grafting using the RIA system.