ABSTRACT
Objective To observe in vitro the effect of mechanical stress at different intensities on the pro-liferation, apoptosis and extracellular matrix of degenerative human nucleus pulposus cells. Methods The cells were isolated and cultured in vitro, and divided into a control group, a low-intensity group, a medium-intensity group and a high-intensity group. The low-, medium- and high-intensity groups were stretched mechanically by 1000 μ, 2000μor 4000μrespectively for 6 hours using a four-point bending system, while the control group was not stressed. Flow cytometry was used to explore any changes in the cell cycle and the proliferation index ( PI) . The expression of proliferating cell nuclear antigen ( PCNA) , B-cell lymphoma-2 ( BCL-2)/Bax, collagen II and aggrecan were meas-ured using real-time quantitative polymerase chain reactions. Results The mechanical stretching significantly influ-enced proliferation, apoptosis and the extracellular matrices compared with the control group. The PI and PCNA ex-pression increased at first and then decreased gradually with the exercise intensity. Compared with the control group, the mRNA expression level of Bcl-2/Bax increased significantly to 1.53 times that of the control group after 1000 μstretching, but to only 0.71 times that of the control group at 2000μand 0.43 times at 4000μ. The gene expression of collagen II increased significantly by 1. 1 times and that of aggrecan by 1. 3 times after 1000 μ stress stimulation compared with the control group ( P≤0.05) . However, the expression of collagen II and aggrecan was inhibited sig-nificantly at 2000 and 4000 μ , with the lowest levels at 4000 μ (P≤0.05). Conclusion Stretching at different intensities has different effects on the proliferation, apoptosis and extracellular matrix of human pulposus cells with degenerate nuclei.