METTL3 promotes IL-1β-induced degeneration of endplate chondrocytes by driving m6A-dependent maturation of miR-126-5p.

METTL3 is an important regulatory molecule in the process of RNA biosynthesis. It mainly regulates mRNA translation, alternative splicing and microRNA maturation by mediating m6A-dependent methylation. Interleukin 1β (IL-1β) is an important inducer of cartilage degeneration that can induce an inflammatory cascade reaction in chondrocytes and inhibit the normal biological function of cells. However, it is unclear whether IL-1β is related to METTL3 expression or plays a regulatory role in endplate cartilage degeneration. In this study, we found that the expression level of METTL3 and methylation level of m6A in human endplate cartilage with different degrees of degeneration were significantly different, indicating that the methylation modification of m6A mediated by METTL3 was closely related to the degeneration of human endplate cartilage. Next, through a series of functional experiments, we found that miR-126-5p can play a significant role in IL-1β-induced degeneration of endplate chondrocytes. Moreover, we found that miR-126-5p can inhibit the PI3K/Akt signalling pathway by targeting PIK3R2 gene, leading to the disorder of cell vitality and functional metabolism. To further determine whether METTL3 could regulate miR-126-5p maturation, we first confirmed that METTL3 can bind the key protein underlying pri-miRNA processing, DGCR8. Additionally, when METTL3 expression was inhibited, the miR-126-5p maturation process was blocked. Therefore, we hypothesized that METTL3 can promote cleavage of pri-miR-126-5p and form mature miR-126-5p by combining with DGCR8.