Bone-derived mesenchymal stem cells alleviate compression-induced apoptosis of nucleus pulposus cells by N6 methyladenosine of autophagy

N6 methyladenosine (m⁶A) is one of the most prevalent epitranscriptomic modifications of mRNAs, and plays a critical role in various bioprocesses. Bone-derived mesenchymal stem cells (BMSCs) can attenuate Apoptosis of nucleus pulposus cells (NPCs) under compression; however, the underlying mechanisms are poorly understood. This study showed that the level of m⁶A mRNA modifications was decreased, and the autophagic flux was increased in NPCs under compression when they were cocultured with BMSCs. We report that under coculture conditions, RNA demethylase ALKBH5-mediated FIP200 mRNA demethylation enhanced autophagic flux and attenuated the Apoptosis of NPCs under compression. Specific silencing of ALKBH5 results in impaired autophagic flux and a higher proportion of apoptotic NPCs under compression, even when cocultured with BMSCs. Mechanistically, we further identify that the m⁶A "reader" YTHDF2 is likely to be involved in the regulation of Autophagy, and lower m⁶A levels in the coding region of FIP200 lead to a reduction in YTHDF2-mediated mRNA degradation of FIP200, a core molecular component of the ULK1 complex that participates in the initiating process of Autophagy. Taken together, our study reveals the roles of ALKBH5-mediated FIP200 mRNA demethylation in enhancing Autophagy and reducing Apoptosis in NPCs when cocultured with BMSCs.