Specific Inhibitory Protein Dkk-1 Blocking Wnt/β-catenin Signaling Pathway Improve Protectives Effect on the Extracellular Matrix

The present study examined the role of Wnt/beta-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-alpha, and the expression of beta-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-alpha and acted as degeneration group. In group C, the cells were cultured with TNF-alpha and transfected with Adv-eGFP and was used as fluorescence control group. In group D, the cells were cultured with TNF-alpha and transfected with Adv-hDKK1-eGFP, serving as intervention group. The expression of type. collagen, proteoglycan, beta-catenin, and MMP-13 in each group was detected by immunocytochemistry and RT-PCR. The result showed that TNF-alpha increased the expression of beta-catenin and MMP-13, and significantly inhibited the synthesis of type. 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-alpha could activate the Wnt/beta-catenin signaling pathway, and increase the expression of MMP-13, thereby resulting in disc degeneration. Specifically blocking Wnt/beta-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.