ALKBH5-mediated MA Demethylation of Runx2 MRNA Promotes Extracellular Matrix Degradation and Intervertebral Disc Degeneration

Background: N6-methyladenosine (mA) methylation is a prevalent RNA modification implicated in various diseases. However, its role in intervertebral disc degeneration (IDD), a common cause of low back pain, remains unclear.

Results: In this investigation, we explored the involvement of mA demethylation in the pathogenesis of IDD. Our findings revealed that ALKBH5 (alkylated DNA repair protein AlkB homolog 5), an mA demethylase, exhibited upregulation in degenerative discs upon mild inflammatory stimulation. ALKBH5 facilitated mA demethylation within the three prime untranslated region (3'-UTR) of Runx2 mRNA, consequently enhancing its mRNA stability in a YTHDF1 (YTH N6-methyladenosine RNA binding protein F1)-dependent manner. The subsequent elevation in Runx2 expression instigated the upregulation of ADAMTSs and MMPs, pivotal proteases implicated in extracellular matrix (ECM) degradation and IDD progression. In murine models, subcutaneous administration of recombinant Runx2 protein proximal to the lumbar disc in mice elicited complete degradation of intervertebral discs (IVDs). Injection of recombinant MMP1a and ADAMTS10 proteins individually induced mild to moderate degeneration of the IVDs, while co-administration of MMP1a and ADAMTS10 resulted in moderate to severe degeneration. Notably, concurrent injection of the Runx2 inhibitor CADD522 with recombinant Runx2 protein did not result in IVD degeneration in mice. Furthermore, genetic knockout of ALKBH5 and overexpression of YTHDF1 in mice, along with lipopolysaccharide (LPS) treatment to induce inflammation, did not alter the expression of Runx2, MMPs, and ADAMTSs, and no degeneration of the IVDs was observed.

Conclusion: Our study elucidates the role of ALKBH5-mediated mA demethylation of Runx2 mRNA in activating MMPs and ADAMTSs, thereby facilitating ECM degradation and promoting the occurrence of IDD. Our findings suggest that targeting the ALKBH5/Runx2/MMPs/ADAMTSs axis may represent a promising therapeutic strategy for preventing IDD.