Overexpression of long non-coding RNA XIST promotes IL-1β-induced degeneration of nucleus pulposus cells through targeting miR-499a-5p

Background: Long non-coding RNA X-interactive specific transcript (XIST) is implicated in many diseases. However, its role and interaction with microRNA (miR)-499a-5p in intervertebral disc degeneration (IDD) remained unclear. Methods: Nucleus pulposus (NP) tissue samples were collected and nucleus pulposus cells (NPCs) were isolated for Interleukin-1? (IL-1?) treatment and identification. XIST and miR-499a-5p expressions in the tissue were measured with quantitative real-time polymerase chain reaction (qRT-PCR). After IL-1? treatment, NPC apoptosis was detected by flow cytometry. The potential binding sites of XIST and miR-499a-5p were predicted by starBase and confirmed by dual-luciferase reporter assay. Relative expressions of tissue inhibitor of metalloproteinases-3 (TIMP-3), Matrix metalloproteinases-3 (MMP-3), MMP-13, Collagen II, Aggrecan and apoptosis-related proteins (Bcl-2 associated X protein, Bax; B-cell lymphoma 2, Bcl-2; cleaved caspase-3) were measured by qRT-PCR and Western blot as needed. Results: XIST expression was upregulated in the NP tissues of patients with IDD, and IL-1? treatment resulted in a degradation of NPCs. Overexpressed XIST promoted the effects of IL-1? on increasing NPC apoptosis and expressions of XIST, MMP-3, MMP-13, Bax and Cleaved caspase-3, but down-regulated TIMP-3, Collagen II, Aggrecan and Bcl-2 expressions. Silencing XIST, however, showed the opposite effects to its overexpression. MiR499a-5p expression was downregulated in NP tissues of IDD patients and could bind with XIST, while its upregulation reversed the effects of overexpressed XIST in the IL-1?-treated NPCs. Conclusion: Overexpressed XIST caused NPC degeneration through promoting apoptosis and extracellular matrix degradation of IL-1?-treated NPCs through targeting miR-499a-5p, and therefore can serve as a potential treatment for IDD.