• Hong-Guang Xu, Ming-Ming Ma, Quan Zheng, Xiang Shen, Hong Wang, Shu-Feng Zhang, Jia-Jia Xu, Chuan-Dong Wang, and Xiao-Ling Zhang.
• Department of Spine Surgery, Yijishan Hospital, Wannan Medical College, Wuhu, Anhui, China.
• Spine. 2016 Aug 15; 41 (16): 1261-1271.

Study DesignThe changes of endplate chondrocytes induced by intermittent cyclic mechanical tension (ICMT) were observed by realtime reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis.ObjectiveTo investigate the role of RhoA/ROCK-1 signaling pathway and E-cadherin/P120-catenin complex in endplate chondrocytes degeneration induced by ICMT.Summary Of Background DataICMT can induce the endplate chondrocyte degeneration. However, the relationship between P120-catenin or RhoA/ROCK-1 signaling pathway and endplate chondrocytes degeneration induced by ICMT is not clear.MethodsICMT (strain at 0.5 Hz sinusoidal curve at 8% elongation) was applied to rat endplate chondrocytes for 6 days, 16 hours a day. The cell viability and apoptosis were examined by the LIVE/DEAD assay and flow cytometry. Histological staining was used to examine the lumbar disc tissue morphology and extracellular matrix. To regulate RhoA/ROCK-1 signaling pathway and the expression of E-cadherin and P120-catenin, RhoA/ROCK-1 pathway-specific inhibitors, E-cadherin, and p120-catenin plasmid were applied. Coimmunoprecipitation was employed to examine the interaction between E-cadherin and P120-catenin, P120-catenin, and RhoA. The related gene expression and protein location was examined by realtime reverse transcription-polymerase chain reaction, Western blot, and immunofluorescence.ResultsThere was no change of viability verified by LIVE/DEAD assay and flow cytometry after ICMT loading. ICMT loading led to RhoA/ROCK-1 signaling activation and the loss of the chondrogenic phenotype of endplate chondrocytes. Inhibition of RhoA/ROCK-1 signaling pathway significantly ameliorated the degeneration induced by ICMT. The expression of P120-catenin and E-cadherin were inhibited by ICMT. ICMT reduced the interaction between P120-catenin and E-cadherin. Furthermore, over-expression of P120-catenin and E-cadherin can suppress the expression of chondrogenic gene, over-expression of P120-catenin can suppress the RhoA/ROCK-1 signaling pathway, but over-expression of E-cadherin cannot do it.ConclusionP120-catenin protects endplate chondrocytes from ICMT Induced degeneration by inhibiting the expression of RhoA/ROCK-1 signaling pathway.Level Of EvidenceN/A.

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