CircGLCE alleviates intervertebral disc degeneration by regulating apoptosis and matrix degradation through the targeting of miR-587/STAP1

Background: Intervertebral disc degeneration (IDD) can induce profound global socioeconomic burdens. Recent studies have suggested that circular RNAs might have crucial functions in the progression of IDD. The purpose of this study was to identify a specific circular RNA and to investigate its regulatory mechanism in IDD. Methods: CircGLCE was selected after microarray analyses and was further analysed by RT-qPCR and FISH. After silencing CircGLCE, its function was assessed with RT-qPCR, immunofluorescence analysis and flow cytometry. Based on Sanger sequencing, miR-587 was identified as a direct target of CircGLCE, and it was further examined with RNA pulldown assays, RT-qPCR, dual luciferase assays and FISH. After silencing CircGLCE or miR-587, western blotting, immunofluorescence analysis, and flow cytometry were conducted. STAP1 was assessed by RT-qPCR and luciferase assay, and experiments with silenced and overexpressed miR-587 were performed. A rescue experiment was also included. In an IDD rat model, the in vivo effects of overexpressing CircGLCE on IDD were analysed with imaging techniques, TUNEL staining, FISH, western blotting, H&E staining and immunohistochemistry. Results: CircGLCE was found to stably exist in the cytoplasm of nucleus pulposus (NP) cells. It was downregulated in IDD. Knockdown of CircGLCE promoted apoptosis and induced the expression of matrix-degrading enzymes in NP cells. CircGLCE served as a miR-587 sponge in NP cells. Inhibiting miR-587 counteracted the IDD-enhancing effect caused by silencing CircGLCE. STAP1 served as the miRNA target that mediated the functions of miR-587. Overexpressing CircGLCE alleviated IDD in vivo. Conclusions: CircGLCE attenuates IDD by regulating the apoptosis of NP cells and by regulating ECM degradation through the targeting of miR-587/STAP1. CircGLCE may be a potential therapeutic target for IDD treatments.