Influences and mechanism of XIST on proliferation and extracellular matrix synthesis of nucleus pulposus cells in rats with intervertebral disc degeneration
Objective To investigate the influences and mechanism of X chromosome inactivation specific transcript(XIST)on the proliferation and extracellular matrix synthesis of nucleus pulposus cells in rats with intervertebral disc degeneration(IDD).Methods SD rat intervertebral disc nucleus pulposus cells were isolated and cultured in vitro,and then randomly divided cells into control group,model group,XIST knockdown group,empty plasmid group,and XIST knockdown+miR-132-3p knockdown group.Except for control group,the cells in other groups were induced by interleukin(IL)-1β to establish IDD models.After nucleus pulposus cells were grouped and treated,the expressions of XIST and miR-132-3p in the nucleus pulposus cells of rats were detected by qRT-PCR;the proliferation of intervertebral disc nucleus pulposus cells was detected by MTS method and EdU staining;ELISA was used to measure the levels of inflammatory factors IL-6 and IL-18 in the intervertebral disc nucleus pulposus cells;Immunoblotting was used to detect the expression of extracellular matrix labeled proteins Collagen Ⅱ and Aggrecan in rat nucleus pulposus cells.The targeted regulation of miR-132-3p by XIST in rat nucleus pulposus cells was detected by dual-luciferase reporter gene assay.IDD rat models were established by intramuscular injection of IL-1β and divided into sham operation group,model group,XIST knockdown group,no-load plasmid group,XIST knockdown+miR-132-3p knockdown group,with 12 rats in each group.After treatment in each group,the expressions of XIST and miR-132-3p in intervertebral disc tissues were detected by qRT-PCR;TUNEL staining was used to detect apoptosis of nucleus pulposus cells in intervertebral disc tissue of rats;the morphology of intervertebral disc cartilage was observed by saffron O staining;serum levels of inflammatory factors IL-6 and IL-18 were determined by ELISA;the expressions of Collagen Ⅱ and Aggrecan in intervertebral disc tissues were detected by Western blotting.Results Compared with control group(cells)/sham operation group(rats),XIST expression in intervertebral disc tissue and nucleus pulposus cells,apoptosis rate of intervertebral disc nucleus pulposus cells,levels of inflammatory factors IL-6 and IL-18 in intervertebral disc nucleus pulposus cells culture medium and serum were increased in model group(P＜0.05),the activity and proliferation rate of nucleus pulposus cells and the expressions of miR-132-3p,Collagen Ⅱ and Aggrecan protein in nucleus pulposus cells and intervertebral disc tissues decreased(P＜0.05);compared with model group,the apoptosis rate of nucleus pulposus cells,the levels of inflammatory factors IL-6 and IL-18 in intervertebral disc nucleus pulposus cells culture medium and serum,and the expression of XIST in nucleus pulposus cells and intervertebral disc tissues of rats in XIST knockdown group decreased(P＜0.05),the activity and proliferation rate of nucleus pulposus cells and the expressions of miR-132-3p,Collagen Ⅱ and Aggrecan protein in nucleus pulposus cells and intervertebral disc tissues increased(P＜0.05).Down-regulation of miR-132-3p attenuates the ameliorative effect of knockdown XIST on IL-1β-induced intervertebral disc injury and cartilage matrix loss.XIST was able to target and down-regulate the expression of miR-132-3p in rat nucleus pulposus cells.Conclusion Knockdown of XIST can inhibit inflammation by up-regulating miR-132-3p,thereby inhibiting the apoptosis of IDD nucleus pulposus cells and promoting their proliferation and extracellular matrix synthesis.
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