Low Intensity Ultrasound Enhances Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

초록

There are clinical advantages of using bone marrow-derived MSCs as donor cells in articular cartilage repair, but several limitations have been demonstrated in inducing chondrogenesis of MSC. Methods to stimulate proliferation and subsequent chondrogenic differentiation of MSCs are needed to further develop the use of cultured MSCs for articular defect repair. Eventhough, several growth factors including TGF-b, IGF, BMPs are known to promote chondrogenesis of MSCs, these factors are not sufficient for the induction of chondrogenesis. Recently, low intensity ultrasound (LIUS) has been shown to augment fracture healing and increase the mechanical strength of fracture callus in clinical studies and animal models. These observations suggest that the mechanical stimulation by LIUS could be one of the factors in chondrogenic pathway in MSCs, even though the underlying mechanisms of LIUS action still remain unclear. However, to date, there have been no reports yet which demonstrate the chondrogenic effects of US on MSCs. In this study, we have examined the possible role of LIUS in chondrogenic differentiation of rabbit bone marrow MSCs in alginate culture with TGF-b3 treatment. Ultrasound stimulation was performed for 10 minute every 12h for 7 consecutive days at a frequency of 1 MHz and intensity of either 0 (control), 200 mW/cm2 in a continuous wave fashion. RT-PCR and western blot analysis were done for examination of collagen type II and aggrecan as the specific marker of chondrogenic differentiation of MSCs. The collagen type II expression was increased at mRNA and protein level by LIUS stimulation. These findings demonstrate that LIUS stimulated the chondrogenic differentiation of rabbit bone marrow MSCs. LIUS might be one of the important mechanical factors in inducing chondrogenesis in cartilage repair