Department of Orthopedics, The Second Hospital of Shandong University, Shandong University, Jinan, Shandong, People's Republic of China.
Department of Orthopedics, Shouguang Hospital of Traditional Chinese Medicine, Shouguang, Shandong, People's Republic of China.
PLoS One. 2018 Aug 20;13(8):e0202269. doi: 10.1371/journal.pone.0202269. eCollection 2018.
Zoledronic acid (ZA) exerts complex influence on bone by suppressing bone resorption, mostly due to the direct osteoclasts inhibition and uncertain influence on osteoblasts. Vitamin K2 (VK2, Menaquinone-4) as an anabolic agent stimulates bone formation via anti-apoptosis in osteoblasts and mild osteoclasts inhibition. Based on these knowledge, the therapeutic effect of the combined or sequential therapy of VK2 and ZA depends on the influence on the osteoblasts, since both cases exert similar inhibitory effect on osteoclasts. In a series of in vitro studies, we confirmed the protective effect of VK2 in osteoblasts culture, especially when followed by exposure to ZA, and the proliferation and mineralization inhibition induced by ZA towards osteoblasts. For mechanism study, expression of bcl-2/bax, Runx2 and Sost in cells were examined. For in vivo studies, an osteoporosis animal model was established in rats via ovariectomy (OVX) and subjected to sequential treatment, namely VK2 followed by ZA. Bone mineral density (BMD) was measured by Dual energy X-ray absorptionmetry (DEXA), morphology and mechanical parameters by micro-computed tomography (micro-CT), mechanical strength by an electro-hydraulic fatigue-testing machine. The bone calcium, hydroxyproline content, blood lipids were evaluated using microplate technique, and the bone surface turnover was evaluated using the fluorescence in corporation method. It was found that VK2 pretreatment partially prevented the inhibition of bone formation caused by ZA, which was reflected by indices like BMD, bone calcium content and bone strength. The underling mechanisms for protection of VK2 pretreatment, mainly demonstrated via in vitro studies, included inhibiting apoptosis and depressing Sost expression in osteoblasts, which in turn improved the osteoporosis therapeutic effects of ZA. These findings suggested that pretreatment with VK2 before ZA therapy might serve a new long-term therapy protocol for osteoporosis.
唑来膦酸（ZA）通过抑制骨吸收对骨骼产生复杂影响，主要是由于对破骨细胞的直接抑制作用和对成骨细胞的不确定影响。维生素 K2（VK2，甲萘醌-4）作为一种合成代谢剂，通过抗成骨细胞凋亡和轻度抑制破骨细胞来刺激骨形成。基于这些知识，VK2 和 ZA 的联合或序贯治疗的治疗效果取决于对成骨细胞的影响，因为这两种情况对破骨细胞都有类似的抑制作用。在一系列体外研究中，我们证实了 VK2 在成骨细胞培养中的保护作用，尤其是在随后暴露于 ZA 时，以及 ZA 对成骨细胞的增殖和矿化抑制作用。为了进行机制研究，检查了细胞中 bcl-2/bax、Runx2 和 Sost 的表达。在体内研究中，通过卵巢切除术（OVX）建立骨质疏松症大鼠动物模型，并进行序贯治疗，即 VK2 后用 ZA。通过双能 X 射线吸收法（DEXA）测量骨密度（BMD），通过微计算机断层扫描（micro-CT）测量形态和力学参数，通过电液疲劳试验机测量力学强度。使用微孔板技术评估骨钙、羟脯氨酸含量和血脂，使用荧光掺入法评估骨表面转换。结果发现，VK2 预处理部分预防了 ZA 引起的成骨抑制，这反映在 BMD、骨钙含量和骨强度等指标上。VK2 预处理的保护机制主要通过体外研究表明，包括抑制成骨细胞凋亡和下调 Sost 表达，从而提高 ZA 的骨质疏松症治疗效果。这些发现表明，ZA 治疗前用 VK2 预处理可能成为骨质疏松症的一种新的长期治疗方案。
