Apoptosis, senescence, and autophagy in rat nucleus pulposus cells: Implications for diabetic intervertebral disc degeneration

Authors

  • Libo Jiang,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Xiaolei Zhang,

    Corresponding author
    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
    2. Center for Stem Cells and Tissue Engineering, School of Medicine, Zhejiang University, HangZhou, China
    • Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China. T/F: 0577-88002823.
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  • Xuhao Zheng,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Ao Ru,

    1. Department of Ultrasound, The Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, China
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  • Xiao Ni,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Yaosen Wu,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
    2. Department of Orthopaedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, 88 Jiefang Road, Hangzhou, China
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  • Naifeng Tian,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Yixing Huang,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Enxing Xue,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Xiangyang Wang,

    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
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  • Huazi Xu

    Corresponding author
    1. Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China
    • Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical College, 109 Western Xueyuan Road, Wenzhou, China. T/F: 0577-88002823.
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  • The authors declare that they have no conflicts of interest.

  • Libo Jiang and Xiaolei Zhang contributed equally to this work.

Abstract

This research was aimed to study the mechanisms by which diabetes aggravates intervertebral disc degeneration (IDD) and to discuss the relationship between autophagy and IDD in nucleus pulposus (NP) cells. Sixteen weeks after injecting streptozotocin (STZ), the intervertebral discs (IVDs) were studied by histology, Alcian blue, 1,9-dimethylmethylene blue (DMMB), immunohistochemistry, and RT-PCR to explore the IDD. The apoptosis and senescence of NP cells was investigated by terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay, immunohistochemistry, and Western blot for caspase3, caspase8, caspase9, and p16lnk4A (increased in cellular senescence). The level of autophagy in NP cells was detected by Western blot, immunohistochemistry, and transmission electron microscopy (TEM). The proteoglycan and collagen II in the extracellular matrix and the aggrecan and collagen II mRNA expression in NP cells of diabetic rats were decreased compared with the control group. Diabetes increased apoptosis of NP cells and led to activations of initiators of intrinsic (caspases-9) and extrinsic (caspase-8) pathways as well as their common executioner (caspase-3). Cellular senescence was increased about twofold in NP of diabetic rats. In addition, the Western blot, immunohistochemistry, and TEM demonstrated higher level of autophagy in NP cells of diabetic rats than control rats to a statistically significant extent. These findings support that diabetes induced by STZ can cause IDD by accelerating the apoptosis and senescence of NP cells excluding the overweight influence. And the results suggest that the autophagy may be a response mechanism to the change of NP cells in diabetic rats. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 692–702, 2013

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