Specific Inhibitory Protein Dkk-1 Blocking Wnt/β-catenin Signaling Pathway Improve Protectives Effect on the Extracellular Matrix / 华中科技大学学报（医学）（英德文版）

The present study examined the role of Wnt/β-catenin signaling pathway in the degeneration of nucleus pulposus cells and the protective effect of DKK1 on nucleus pulposus cells.The model of nucleus pulposus cell degeneration was induced by intra-disc injection of TNF-α,and the expression of β-catenin protein was detected by Western blotting.The cultured rabbit nucleus pulposus cells were divided into 4 groups.In group A,the cells were cultured with normal medium and served as control group.In group B,the cells were cultured with TNF-α and acted as degeneration group.In group C,the cells were cultured with TNF-α and transfected with Adv-eGFP and was used as fluorescence control group.In group D,the cells were cultured with TNF-α and transfected with Adv-hDKK1-eGFP,serving as intervention group.The expression of type Ⅱ collagen,proteoglycan,β-catenin,and MMP-13 in each group was detected by immunocytochemistry and RT-PCR.The result showed that TNF-α increased the expression of β-catenin and MMP-13,and significantly inhibited the synthesis of type Ⅱ collagen and proteoglycan,which resulted in the degeneration of nucleus pulposus cells.This effect could be obviously reversed by DKK1.We are led to concluded that TNF-α could activate the Wnt/β-catenin signaling pathway,and increase the expression of MMP-13,thereby resulting in disc degeneration.Specifically blocking Wnt/β-catenin signaling pathway by DKK-1 could protect the normal metabolism of intervertebral disc tissue.The Wnt pathway plays an important role in the progression of the intervertebral disc degeneration.

Rabbit Annulus Fibrosus Cell Apoptosis Induced by Mechanical Overload via a Mitochondrial Apoptotic Pathway / 华中科技大学学报（医学）（英德文版）

In order to investigate the apoptotic pathway of rabbit annulus fibrosus(AF)cells induced by mechanical overload,an experimental air-pressure model was established in this study to pressurize the rabbit AF cells in vitro.Cells were randomly divided into five groups in which the cells were exposed to a continuous pressure of 1.1 MPa for different lengths of time(0,5,12,24 and 36 h).The cell proliferation and apoptosis were detected by cell counting kit-8(CCK-8)assay and flow cytometry; thealterations in mitochondrial membrane potential were measured by fluorescence microscopy and fluorescence spectrophotometer; the activities of caspase-8 and 9 were determined by spectrophotometry.The results showed that after the cells were subjected to the pressure for 24 or 36 h,the cell proliferation was inhibited; the ratio of cell apoptosis was increased; the mitochondrial membrane potential was decreased;the activity of caspase-9 was enhanced; no activity changes were observed in caspase-8.The results suggested that treatment with a pressure of 1.1 MPa for more than 24 h can lead to the proliferation inhibition and the apoptosis of rabbit AF cells in vitro,and the mitochondrial-dependent pathway is implicated in the pressure-induced AF cell apoptosis.