FBW7 inhibits nucleus pulposus cells proliferation by downregulation of cyclin E in the intervertebral disc degeneration

J.-W. Xu, J. Wang, K. Yang, S. Guo, C.-S. Feng, H.-Y. Chen, H.-P. Li

Department of Orthopedics, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, China. lhp-3993@163.com

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• Orthopedics

OBJECTIVE: TF-box and WD repeat domain-containing 7 (FBW7), a component of SCF ubiquitin ligase complex, usually acts as a tumor suppressor because it has an ability in the inhibition of cell proliferation. Nevertheless, the role of FBW7 in intervertebral disc degeneration (IDD) is not quite understood.

MATERIALS AND METHODS: The total protein and RNA were isolated from patients’ disc tissues. WB was carried out to analyze the collagen II and FBW7 protein levels of different Pfirrmann grades disc degeneration. Reverse transcription-polymerase chain reaction (RT-PCR) was used to test the collagen II and FBW7 mRNA expression in these disc samples. NP cells were transfected with siRNA-FWB7 to downregulate the FBW7 expression. SiRNA-NC was used as the sham group. Cyclin E, E2F1, and E2F2 were analyzed with WB and RT-PCR.

RESULTS: In this study, different kinds of degenerated disc tissues were analyzed, and it was found that FBW7 was overexpressed in much severe degeneration condition, which was also proved by the IL-1β stimuli nucleus pulposus (NP) cells degeneration model in vitro. Interestingly, the results showed that FBW7 suppression could reverse the degeneration of NP cells. Furthermore, we found that FBW7 induced NP cell cycle arrest in the G1 phase of and inhibited cell proliferation by upregulating p27 expression in vitro. The overexpression of p27 resulted in the inhibition of cyclin E, which promotes cell proliferation.

CONCLUSIONS: Taken together, our study uncovered that FBW7 played an essential inhibitory role in NP cells proliferation, providing new insights that FBW7 may be a potential strategy for IDD treatments.

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