Chinese Journal of Tissue Engineering Research ›› 2016, Vol. 20 ›› Issue (7): 972-980.doi: 10.3969/j.issn.2095-4344.2016.07.008

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Effects of cyclic tensile strain on actin cytoskeleton rearrangement in annulus fibrosus cells

Zhang De-hong1, Fang Peng-fei2, Wang Xing-sheng1, Zhao Ji-rong1, Li Xiao-na3     

  1. 1Department of Orthopedics, Gansu Provincial Hospital of TCM, Lanzhou 730050, Gansu Province, China; 2Department of Orthopedics, Baiyin Branch, Gansu Provincial Hospital of TCM, Baiyin 730900, Gansu Province, China; 3Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi Province, China
  • Received:2016-01-08 Online:2016-02-12 Published:2016-02-12
  • Contact: Fang Peng-fei, Master, Attending physician, Department of Orthopedics, Baiyin Branch, Gansu Provincial Hospital of TCM, Baiyin 730900, Gansu Province, China
  • About author:Zhang De-hong, Chief physician, Department of Orthopedics, Gansu Provincial Hospital of TCM, Lanzhou 730050, Gansu Province, China
  • Supported by:

    the Natural Science Foundation of Gansu Province, No. 1208RJZA174

Abstract:

BACKGROUND: When the intervertebral disc is under stress, the hydraulic pressure generated inside the nucleus pulposus makes the annulus fibrosus extend outward and expand, and the annulus collagen fibers are stretched so that the extracellular matrix of annulus fibrosus cells is also under the pressure. In the intervertebral disc, aggrecan is the main component of proteoglycans, matrix metalloproteinase-2 is a major enzyme for extracellular matrix degradation, and tissue inhibitor of metalloproteinase is a multifunctional specific inhibition factor for matrix metalloproteinase activity. There is a mutual regulation between the latter two to keep the homeostasis between them.
OBJECTIVE: To investigate the mechanism of cyclic tensile strain in the metabolism of intervertebral disc annulus matrix.
METHODS: Rat anulus fibrosus cells were subjected to 2% or 10% cyclic tensile strain at 1.0 Hz for 2 and 12 hours using Flexcell4000 tension system. Then cells were collected and cultured in conditioned medium for gene and protein detection. Real-time quantitative PCR was used to detect mRNA expression of aggrecan, matrix metalloproteinases-2 and tissue inhibitor of metalloproteinase-2. Gelatin zymography was used to detect matrix metalloproteinases-2 activity.
RESULTS AND CONCLUSION: The use of 2% cyclic tensile strain had no obvious effect on the stress fiber of actin cytoskeleton, whereas actin cytoskeleton was depolymerized in response to 10% cyclic tensile strain. The 2% cyclic tensile strain raised the expression of Aggrecan at 12 hours; whereas raised the matrix metalloproteinases-2 and tissue inhibitor of metalloproteinase-2 at 2 hours, both of which were in homeostasis; matrix metalloproteinases-2 activity had no significant changes. 10% cyclic tensile strain had no effect on the mRNA expression of Aggrecan. No matter stretching 2 or 12 hours, the matrix metalloproteinases-2 was up-regulated, and the tissue inhibitor of metalloproteinase-2 was down-regulated, both of which were not in balance. Moreover, the matrix metalloproteinases-2 activity was not significantly changed. These findings indicate that the mRNA expressions of Aggrecan, matrix metalloproteinases-2 and tissue inhibitor of metalloproteinase-2 alter in response to cyclic tensile strain in rat anulus fibrosus cells, and the tensile strain induces different mechano-responses in the actin cytoskeleton.