Rabbit annulus fibrosus cell apoptosis induced by mechanical overload via a mitochondrial apoptotic pathway

In order to investigate the apoptotic pathway of rabbit annulus fibrosus (AF) cells induced by mechanical overload, an experimental air-pressure model was established in this study to pressurize the rabbit AF cells in vitro. Cells were randomly divided into five groups in which the cells were exposed to a continuous pressure of 1.1 MPa for different lengths of time (0, 5, 12, 24 and 36 h). The cell proliferation and apoptosis were detected by cell counting kit-8 (CCK-8) assay and flow cytometry; the alterations in mitochondrial membrane potential were measured by fluorescence microscopy and fluorescence spectrophotometer; the activities of caspase-8 and 9 were determined by spectrophotometry. The results showed that after the cells were subjected to the pressure for 24 or 36 h, the cell proliferation was inhibited; the ratio of cell apoptosis was increased; the mitochondrial membrane potential was decreased; the activity of caspase-9 was enhanced; no activity changes were observed in caspase-8. The results suggested that treatment with a pressure of 1.1 MPa for more than 24 h can lead to the proliferation inhibition and the apoptosis of rabbit AF cells in vitro, and the mitochondrial-dependent pathway is implicated in the pressure-induced AF cell apoptosis.