Long-term occupational exposure to whole-body vibration increases the risk of disc degeneration and the consequent back pain [1]. The pathogenesis of vibration induced disorders is still not completely clear and there is no effective treatment. Although the potential effects of vibrational stress on extracellular matrix (ECM) assembly and degradation are particularly relevant to the clinical findings of the vibration induced disorders, the effects of vibrational loads on disc cells are largely unknown. It has been shown that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells [2–5]. However, these studies investigated only the extent of the effect of quasi-static hydrostatic loads. During daily occupational activities intervertebral disc is exposed to dynamic oscillatory hydrostatic loads, characterized by wide frequency spectrum and variable amplitude. In this case, a physiologic level of amplitude and frequency of hydrostatic pressure may be essential for maintaining the matrix of the disc, while an abnormal amplitude and frequency of hydrostatic pressure may accelerate disc degeneration. The ranges of good and bad loading frequencies and amplitudes still need to be discovered. The objective of this study was to find which of loading frequency and loading amplitude has more influence in affecting disc cell response to vibration. To address this issue we developed a mechanically-active culture system capable of delivering a wide range of loading frequency and amplitude of hydrostatic pressure to cultures of nucleus pulposus cells. We used nucleus cells, which are exposed mainly to hydrostatic loading in vivo.

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