Induction of intervertebral disc cell apoptosis and degeneration by chronic unpredictable stress

Object. The purpose of this study was to evaluate the effects of chronic unpredictable stress on the intervertebral discs of rats. Methods. The cellular events involved in injury- and stress-induced disc degeneration were investigated in male Wistar rats. Disc degeneration and apoptosis were evaluated using microscopic (light and electron) and molecular (immunoblotting and immunohistochemistry) methods. Corticosterone levels were used as markers of stress and measured by radioimmunoassay. Results. The data gathered in this study showed that chronic unpredictable stress can significantly increase corticosterone levels. Furthermore, biochemical markers of apoptosis (that is, increases in the Bax/Bcl2 ratio and TUNEL reactivity [p < 0.05]) were observed in the stressed animals. Electron and light microscopy also showed disc degeneration and apoptotic cells in the experimental groups. Conclusions. Taken together, these data demonstrated that chronic stress is most likely to be a risk factor for creating intervertebral disc degeneration and that programmed cell death may be one of the mechanisms of stress-induced disc degeneration.