Long Non-coding RNA HOTAIR Modulates Intervertebral Disc Degenerative Changes Via Wnt/β-catenin Pathway

Background: Intervertebral disc degeneration(IDD)has a complicated and enigmatic pathogenic process.IDD is characterized by the increased senescence of nucleus pulposus(NP)cell,abnormal NP cell apoptosis,disordered extracellular matrix(ECM)remodeling and the increased expression of various inflammatory factors in NP cells.Accumulating evidence shows that long non-coding RNAs(Lnc RNAs)play a regulatory role in the pathogenesis of IDD.HOX transcript antisense RNA(HOTAIR),a lnc RNA is reportedly associated with Wnt/β-catenin pathway in the course of cancer,whereas Wnt/β-catenin pathway is shown to promote IDD.However,how it affects NP cells,the primary component of intervertebral discs is still unclear.This study aimed to investigate the expression and role of the HOTAIR in IDD pathogenesis.Methods: NP tissue samples from 10 patients with idiopathic scoliosis and 30 patients with lumbar disc herniation were collected.q RT-PCR was used to assess the expression of HOTAIR in NP tissues from idiopathic scoliosis patients or IDD patients.Immunohistochemistry was used to assess the expression of senescence markers(p16 and p53)and apoptosis-related molecules(Bax and Bcl-2)on human NP tissue samples.Gainand loss-of-function experiments were used to assess the function of HOTAIR in degenerative NP cells in vitro.Wnt/β-catenin pathway was also examined.q RT-PCR was used to assess the expression of HOTAIR and ECM-related genes(MMP-3,MMP-9,MMP-10,type II collagen,and aggrecan);western blotting was used to detect the expression of senescence biomarkers,apoptosis-related proteins,and Wnt/β-catenin pathway;flow cytometry was used to detect apoptosis and cell cycle phases of NP cells;MTT assay was used to determine cell proliferation,Immunofluorescence staining was used to assess the expression of MMP-9;TUNEL staining was used to detect apoptosis of NP cells;and the SA-β-Gal staining was performed to examine the degree of senescence in NP cells.Moreover,a classic needle-punctured rat tail model was used to investigate the role of HOTAIR in IDD in vivo.Results: The results showed that the expression of HOTAIR was significantly upregulated in IDD patients compared to that in idiopathic scoliosis patients,and the HOTAIR expression positively correlated with IDD grade.The overexpression of HOTAIR was found to induce NP cell senescence,apoptosis,and ECM degradation.HOTAIR silencing by RNA interference in NP cells prevented interleukin-1β-induced NP cell senescence,apoptosis,and ECM degradation.Furthermore,we found that the Wnt/β-catenin pathway played a regulatory role in regulating HOTAIR to induce these changes in NP cells.Moreover,HOTAIR inhibition in a rat model effectively attenuated IDD symptoms in vivo.Conclusions: Our findings confirmed that HOTAIR promoted NP cell senescence,apoptosis,and ECM degradation via the activation of the Wnt/β-catenin pathway,while silencing HOTAIR attenuated this degeneration process,indicating a potential therapeutic target against IDD.