Abstract：
Long-term usage of bisphosphonates, especially zoledronic acid (ZA), induces osteogenesis disorders and medication-related osteonecrosis of the jaw (MRONJ) in patients, thereby contributing to the destruction of bone remodeling and the continuous progression of osteonecrosis. Menaquinone-4 (MK-4), a specific vitamin K2 isoform converted by the mevalonate (MVA) pathway in vivo, exerts the promotion of bone formation, whereas ZA administration suppresses this pathway and results in endogenous MK-4 deficiency. However, no study has evaluated whether exogenous MK-4 supplementation can prevent ZA-induced MRONJ. Here we showed that MK-4 pretreatment partially ameliorated mucosal nonunion and bone sequestration among ZA-treated MRONJ mouse models. Moreover, MK-4 promoted bone regeneration and inhibited osteoblast apoptosis in vivo. Consistently, MK-4 downregulated ZA-induced osteoblast apoptosis in MC3T3-E1 cells and suppressed the levels of cellular metabolic stresses, including oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, and DNA damage, which were accompanied by elevated sirtuin 1 (SIRT1) expression. Notably, EX527, an inhibitor of the SIRT1 signaling pathway, abolished the inhibitory effects of MK-4 on ZA-induced cell metabolic stresses and osteoblast damage. Combined with experimental evidences from MRONJ mouse models and MC3T3-E1 cells, our findings suggested that MK-4 prevents ZA-induced MRONJ by inhibiting osteoblast apoptosis through suppression of cellular metabolic stresses in a SIRT1-dependent manner. The results provide a novel translational direction for the clinical application of MK-4 for preventing MRONJ.
摘要：
长期使用双膦酸盐，特别是唑来膦酸（ZA），在患者中诱导成骨障碍和药物相关的颌骨坏死（MRONJ），从而导致骨重建的破坏和骨坏死的持续发展。甲基萘醌-4(MK-4),通过甲羟戊酸（MVA）途径在体内转化的特定维生素K2同工型，发挥促进骨形成的作用，而ZA给药抑制该途径并导致内源性MK-4缺乏。然而,尚无研究评估外源性MK-4补充是否可以预防ZA诱导的MRONJ。在这里，我们表明MK-4预处理部分改善了ZA处理的MRONJ小鼠模型中的粘膜骨不连和骨隔离。此外，MK-4在体内促进新骨再生并抑制成骨细胞凋亡。始终如一，MK-4下调ZA诱导的MC3T3-E1细胞成骨细胞凋亡，抑制细胞代谢应激水平，包括氧化应激,内质网应激,线粒体功能障碍，和DNA损伤,伴有沉默调节蛋白1（SIRT1）表达升高。值得注意的是,EX527，SIRT1信号通路的抑制剂，消除了MK-4对ZA诱导的细胞代谢应激和成骨细胞损伤的促进作用。结合MRONJ小鼠模型和MC3T3-E1细胞的实验证据，我们的研究结果表明,MK-4通过抑制细胞代谢应激以SIRT1依赖性方式抑制成骨细胞凋亡,从而阻止ZA诱导的MRONJ.该结果为MK-4预防MRONJ的临床应用提供了新的平移方向。
