Involvement of autophagy in the progression of compression-induced nucleus pulposus cell degeneration and death

Abstract

Objective To investigate the involvement of autophagy in the progression of compression-induced intervertebral disc (IVD) degeneration.Methods Rabbit nucleus pulposus (NP) cells were isolated from the thoracolumbar IVD of 3-month-old Japanese white rabbits.The rabbit NP cells at the second generation were cultured under the compression condition of 1 Mpa for 12,24 or 48 h.Cell viability was determined by using cell counting Kit-8 (CCK8).The ultrastructural features of rabbit NP cells exposed to compression were examined under the transmission electron microscopy (TEM).The presence of autophagic vacuoles,as a marker of autophagy,was detected by using fluorescent dye monodansylcadaverine (MDC).The variation of autophagy-related gene expression was analyzed by using real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) to evaluate the effect of compression on autophagy of rabbit NP cells.Results Compression induced rabbit NP cell degeneration and death.The autophagosomes were detected in rabbit NP cells under the TEM.The autophagic rate was (1.580 ± 0.171) ％,(7.930 ±0.252) ％,(13.530 ± 1.206) ％ at 12,24,and 48 h respectively.The mRNA expression of beclin-1 and LC3B was significantly higher in the compression treatment group than in the control group (P ＜ 0.05),and the mRNA expression of beclin-1 and LC3B was increased over time under compression culture condition.Conclusion Autophagy and autophagic cell death were present in compression-induced rat NP cell injury,which offers a novel sight about compression-induced degeneration of IVD cells. Key words: Intervertebral disc; Autophagy; Compression; Nucleus pulposus cells