Jamie Harle

Effects of ultrasound on the growth and function of bone and periodontal ligament cells in vitro

The effects of therapeutic ultrasound (US) on tissue healing processes in vivo are likely to involve US-induced changes in key cellular functions. However, these have not yet been clearly delineated and the present study has, therefore, examined the effects of a single 5-min CW exposure of 3.00-MHz US on the growth and functional activity of a human osteoblast-like cell line (MG63 cells) and human periodontal ligament (PDL) cells in vitro. Although cell proliferation was found to be largely unaffected by spatial average intensity (I(SA)) values of between 140-990 mW/cm(2), flow cytometry (FCM) analysis showed that there were pronounced and differential effects on cell function. Thus, bone-associated proteins were down-regulated, whereas collagen type I (COL I) was unaffected and fibronectin (FN) was up-regulated at low intensities in MG63 cells. In contrast, bone protein expression was found to be dose-dependent, and FN and COL I were down-regulated in PDL cells. These results show that US has potentially important effects on the functional activities of connective tissue cells in vitro, which could markedly influence tissue repair and regeneration processes in vivo.

Effects of therapeutic ultrasound on osteoblast gene expression

Ultrasound (US) is commonly used as a physiotherapy aid for a number of types of injury to soft connective tissues and for fracture healing. However, the precise effects of therapeutic US on tissue healing processes are not clearly understood, although they are likely to involve changes in key cellular functions. The present study has therefore examined the effects of several US intensity levels on the activity of two bone-associated proteins, alkaline phosphatase (ALP) and osteopontin (OP) in a human cell line, MG63, using RT-PCR. ALP showed progressively higher expression with increasing US intensities, whereas OP responded differently, showing down-regulation at 120 mW/cm2, the lowest US exposure. OP expression was considerably less affected overall compared with the relative response of ALP to the same US doses. The results show that there is a differential response to therapeutic levels of US, since ALP and OP clearly exhibited gene-specific response profiles. 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.© 2001 Kluwer Academic Publishers