Effects of therapeutic ultrasound on osteoblast gene expression

Ultrasound (US) is commonly used as a physiotherapy aid for a number of typ es of injury to soft connective tissues and for fracture healing. However, the precise effects of therapeutic US on tissue healing processes are not c learly understood, although they are likely to involve changes in key cellu lar functions. The present study has therefore examined the effects of seve ral US intensity levels on the activity of two bone-associated proteins, al kaline phosphatase (ALP) and osteopontin (OP) in a human cell line, MG63, u sing RT-PCR. ALP showed progressively higher expression with increasing US intensities, whereas OP responded differently, showing down-regulation at 1 20 mW/cm(2), the lowest US exposure. OP expression was considerably less af fected overall compared with the relative response of ALP to the same US do ses. The results show that there is a differential response to therapeutic levels of US, since ALP and OP clearly exhibited gene-specific response pro files. These findings suggest that modifying the parameters of US exposure could be used to improve repair and regeneration processes and enhance the clinical efficacy of implanted biomaterials for tissue engineering. (C) 200 1 Kluwer Academic Publishers.