Osteogenic protein-1 attenuates the inflammatory cytokine-induced NP cell senescence through regulating the ROS/NF-κB pathway

Abstract

Background: Nucleus pulposus (NP) cell senescence correlates with disc degeneration. Previous studies imply that inflammation induces NP cell senescence. Osteogenic protein-1 (OP-1) is helpful for regenerating degenerative disc.

Objective: To investigate whether OP-1 treatment can protect against the inflammatory cytokine TNF-α-induced NP cell senescence, and its potential mechanism.

Methods: Rat NP cells were cultured in either basic culture medium or basic culture medium with the inflammatory cytokine TNF-α for 3 days. OP-1 was added into the culture medium of TNF-α-treated NP cells to investigate the protective effects of OP-1 against cellular senescence. NP cell senescence was evaluated by some direct and indirect parameters, such as senescence associated β-galactosidase (SA-β-Gal) activity, cell cycle, telomerase activity, expression of senescence markers (p16 and p53), and the matrix homeostatic phenotype. Additionally, intracellular reactive oxygen species (ROS) and the activity of the NF-κB pathway were also analyzed.

Results: Compared with the control group, the inflammatory cytokine TNF-α significantly promoted NP cell senescence, reflected by the increase in SA-β-Gal activity, G0/G1 phase fraction and senescence markers (p16 and p53) expression, and the decrease in telomerase activity and matrix macromolecules (aggrecan and collagen II) expression. However, OP-1 suppressed the effects of TNF-α on NP cell senescence. Further analysis showed that OP-1 reduced ROS generation in TNF-α-treated NP cells, as well as the resulting activity of the NF-κB pathway.

Conclusion: OP-1 can attenuate inflammatory cytokine TNF-α-induced NP cell senescence, and the ROS/ NF-κB pathway may participate in this regulatory process. This study provides that OP-1 may be efficacy in retarding inflammation-exacerbated disc degeneration.

Keywords: Nucleus pulposus; Osteogenic protein-1; Senescence; TNF-α.