Dynamics of N6-methyladenosine modification during aging and their potential roles in the degeneration of intervertebral disc.

BACKGROUND

The N6-methyladenosine (m6A) dynamics in the progression of intervertebral disc (IVD) aging remain largely unknown. This study aimed to explore the distribution and pattern of mA modification in nucleus pulpous (NP) tissues of rats at different ages.

METHODS

Histological staining and MRI were performed to evaluate the degeneration of IVD. The expression of m6A modifiers was analyzed using qRT-PCR and western blot. Subsequently, methylated RNA immunoprecipitation next generation sequencing and RNA-seq were conducted to identify differences in m6A methylome and transcriptome of NP tissues.

RESULTS

Compared to 2-month-old rats, we found significant changes in the global m6A level and the expression of Mettl3 and FTO in NP tissues from 20-month-old rats. During the progression of NP aging, there were 1126 persistently differentially m6A peaks within 931 genes, and 51 persistently differentially expressed genes. GO and KEGG analyses showed that these m6A peaks and m6A modified genes were mainly engaged in the biological processes and pathways of intervertebral disc degermation (IDD), such as extracellular matrix metabolism, angiogenesis, inflammatory response, mTOR and AMPK signaling pathways. Meanwhile, conjoint analyses and Venn diagram revealed a total of 405 aging related genes contained significant methylation and expression levels in 20-month-old rats in contrast to 2-month-old and 10-month-old rats. Moreover, it was found that four aging related genes with hypermethylated modification including BUB1, CA12, Adamts1, and Adamts4 depicted differentially expressed at protein level, of which BUB1 and CA12 were decreased, while Adamts1 and Adamts4 were increased during the progression of NP aging.

CONCLUSION

Collectively, this study elucidated the distribution and pattern of m6A modification during the aging of IVD. Furthermore, the m6A modified genes were involved in the IDD related biological processes and pathways. These findings may provide novel insights into the mechanisms and therapies of IDD from the perspective of aging.