title: Beta1 integrin inhibits apoptosis induced by cyclic stretch in annulus fibrosus cells via ERK1/2 MAPK pathway.
abstract: Low back pain is associated with intervertebral disc degeneration (IVDD) due to cellular loss through apoptosis. Mechanical factors play an important role in maintaining the survival of the annulus fibrosus (AF) cells and the deposition of extracellular matrix. However, the mechanisms that excessive mechanical forces lead to AF cell apoptosis are not clear. The present study was to look for how AF cells sense mechanical changes. In vivo experiments, the involvement of mechanoreceptors in apoptosis was examined by RT-PCR and/or immunoblotting in the lumbar spine of rats subjected to unbalanced dynamic and static forces. In vitro experiments, we investigated apoptotic signaling pathways in untransfected and transfected AF cells with the lentivirus vector for rat β1 integrin overexpression after cyclic stretch. Apoptosis in AF cells was assessed using flow cytometry, Hoechst 33258 nuclear staining. Western blotting was used to analyze expression of β1 integrin and caspase-3 and ERK1/2 MAPK signaling molecules. In the rat IVDD model, unbalanced dynamic and static forces induced apoptosis of disc cells, which corresponded to decreased expression of β1 integrin. Cyclic stretch-induced apoptosis in rat AF cells correlated with the activation of caspase-3 and with decreased levels of β1 integrin and the phosphorylation levels of ERK1/2 activation level. However, the overexpression of β1 integrin in AF cells ameliorated cyclic stretch-induced apoptosis and decreased caspase-3 activation. Furthermore, ERK1/2-specific inhibitor promotes apoptosis in vector β1-infected AF cells. These results suggest that the disruption of β1 integrin signaling may underlie disc cell apoptosis induced by mechanical stress. Further work is necessary to fully elucidate the pathophysiological mechanisms that underlie IVDD caused by unbalanced dynamic and static forces.
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China.|Jiangsu Jiangyin People' Hospital, Jiangyin, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Ding
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China.|Affiliated Hospital of Xuzhou Medical College, Xuzhou, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China.
authors.forename: Xiao-jiang
authors.initials: XJ
authors.lastname: Sun
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China.
authors.forename: You-zhuan
authors.initials: YZ
authors.lastname: Xie
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China. cqzhao@yeah.net.
authors.forename: Chang-qing
authors.initials: CQ
authors.lastname: Zhao
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, People's Republic of China. profzhaojie@163.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism; D007403:Intervertebral Disc / Q000378:metabolism / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016086:Lentivirus / Q000235:genetics; D008159:Lumbar Vertebrae / Q000378:metabolism / Q000473:pathology; D008297:Male; D040542:Mechanotransduction, Cellular / Q000235:genetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics* / Q000378:metabolism; D010006:Osteoblasts / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D014162:Transfection
chemical_list: D019012:Integrin beta1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C505410:Casp3 protein, rat; D053148:Caspase 3
keywords: Apoptosis; Cyclic stretch; ERK; Intervertebral disc degeneration; β1 integrin