Department of Orthopedics, First Affiliated Hospital of Zhengzhou University, Zhengzhou, People's Republic of China.
Clinical College of Orthopedics, Tianjin Medical University, Tianjin, People's Republic of China.
J Gerontol A Biol Sci Med Sci. 2024 Aug 1;79(8). doi: 10.1093/gerona/glae150.
Nucleus pulposus cell (NPC) senescence in intervertebral disc (IVD) tissue is the major pathological cause of intervertebral disc degeneration (IDD). N6-methyladenosine (m6A) methylation and gut microbiota play important roles in the progression of IDD. This study investigated whether methyltransferase-like 3 (METTL3) regulates TLR2 m6A modification and gut microbiota to influence NPC senescence.
An IDD rat model was established by lumbar IVD puncture and NPCs were challenged with IL-1β to mimic IVD injury. IDD rats and IL-1β-exposed NPCs were treated with METTL3-interfering lentivirus and the TLR2 agonist Pam3CSK4. Compositional changes in the rat gut microbiota were analyzed and fecal microbiota transplantation procedures were used. NPC senescence, cell cycle, and the expression of senescence-associated secretory phenotype (SASP) factors were assessed. The m6A enrichment of TLR2 and the binding of IGF2BP1 to TLR2 mRNA were examined.
METTL3 and TLR2 were highly expressed in IDD rats. METTL3 silencing attenuated senescent phenotypes and reduced secretion of SASP factors. Pam3CSK4 reversed the beneficial effects of METTL3 silencing on NPC senescence and IVD injury. METTL3 stabilized TLR2 mRNA in an IGF2BP1-dependent manner. METTL3 silencing restored specific gut microbiota levels in IDD rats, which was further reversed by administration of Pam3CSK4. Fecal microbiota from METTL3 silenced IDD rats altered the pathological phenotypes of IDD rats.
These results demonstrate the beneficial effects of METTL3 silencing on NPC senescence and amelioration of IVD injury, involving modulation of TLR2 m6A modification and gut microbiota. These findings support METTL3 silencing as a potential therapeutic target for IDD.
椎间盘（IVD）组织中的髓核细胞（NPC）衰老，是椎间盘退变（IDD）的主要病理原因。N6-甲基腺苷（m6A）甲基化和肠道微生物群在 IDD 的进展中发挥重要作用。本研究旨在探讨甲基转移酶样 3（METTL3）是否通过调节 TLR2 m6A 修饰和肠道微生物群来影响 NPC 衰老。
通过腰椎 IVD 穿刺建立 IDD 大鼠模型，并用白细胞介素 1β（IL-1β）处理 NPC 以模拟 IVD 损伤。用 METTL3 干扰慢病毒和 TLR2 激动剂 Pam3CSK4 处理 IDD 大鼠和暴露于 IL-1β的 NPC。分析大鼠肠道微生物群的组成变化，并进行粪便微生物群移植程序。评估 NPC 衰老、细胞周期和衰老相关分泌表型（SASP）因子的表达。检测 TLR2 的 m6A 富集和 IGF2BP1 与 TLR2 mRNA 的结合。
METTL3 和 TLR2 在 IDD 大鼠中高表达。沉默 METTL3 可减轻衰老表型并减少 SASP 因子的分泌。Pam3CSK4 逆转了 METTL3 沉默对 NPC 衰老和 IVD 损伤的有益作用。METTL3 以 IGF2BP1 依赖的方式稳定 TLR2 mRNA。沉默 METTL3 可恢复 IDD 大鼠中特定的肠道微生物群水平，而 Pam3CSK4 进一步逆转了这一作用。来自沉默 METTL3 的 IDD 大鼠的粪便微生物群改变了 IDD 大鼠的病理表型。
这些结果表明，沉默 METTL3 对 NPC 衰老和改善 IVD 损伤具有有益作用，涉及 TLR2 m6A 修饰和肠道微生物群的调节。这些发现支持将 METTL3 沉默作为 IDD 的潜在治疗靶点。
