唑来膦酸对大鼠颌面骨和外周骨创伤后骨改建的影响

目的 研究唑来膦酸对大鼠颌面骨和外周骨创伤后骨改建的影响。方法 SD大鼠随机分为实验组和对照组,每周分别给予尾静脉注射唑来膦酸(80 μg/kg)和PBS。用药两周后,在全麻下拔除一侧上颌第一磨牙,并在同侧胫骨近心端制备骨缺损,缝合创口,继续用药至术后1、4和12周后分批处死,分离并收集骨组织样本。Micro-CT分析各组骨缺损区新骨形成情况。HE和Masson染色分析骨缺损区软组织愈合情况、新骨形成情况、有无炎症反应和死骨形成等。ELISA法检测骨改建过程中关键因子RANKL和OPG的表达。结果 Micro-CT结果显示,实验组拔牙创表面高低不平,中部浅凹处可见游离的死骨片,而对照组拔牙创新骨形成区域与周边骨质均匀连续,进行了正常的生理性骨改建。实验组胫骨缺损区愈合,骨皮质完整连续,较对照组厚且致密,骨松质内的新生骨亦明显较对照组排列紧密。术后4周和12周,实验组胫骨BV/TV值较对照组明显上升(P<0.05),实验组颌骨BV/TV值较对照组差异无统计学意义。组织学染色显示,实验组颌骨拔牙创黏膜未愈合或延迟愈合,未愈合的黏膜下方可见暴露骨坏死,骨质出现不同程度的硬化,且周围伴有大量的炎性细胞浸润,为典型的双膦酸盐相关性颌骨坏死(BRONJ)组织病理表现。对照组颌骨拔牙创上皮正常愈合,覆盖创面,拔牙窝进行了正常的生理性骨改建。实验组胫骨骨缺损已愈合,骨皮质较对照组增厚,新骨生成和骨改建速度较对照组快,松质骨内新生骨小梁数量和密度亦较对照组增高。细胞因子检测显示,实验组颌骨RANKL/OPG比值较对照组明显下降(P<0.05),实验组胫骨RANKL/OPG比值则较对照组明显上升(P<0.05)。结论 唑来膦酸抑制大鼠颌骨拔牙后骨改建,引起颌骨BRONJ样病变,却在一定程度上促进大鼠外周骨骨创后骨改建。RANKL/OPG值可能在BRONJ发生过程中起重要作用。

Effects of zoledronate on bone remodeling of maxillofacial and peripheral bones after trauma in rats

Objective To evaluate and compare the effects of zoledronate on bone remodeling of maxillofacial and peripheral bones after trauma in rats. Methods Sprague-Dawley rats were randomly divided into experimental group and control group, and then injected intravenously with zoledronate (80 μg/kg every week) and PBS via the tail vein, respectively. Two weeks later, the first molar from maxilla was extracted, and cylindrical bone defect was prepared on the ipsilateral tibia under general anesthesia. Drugs were continuously injected for 1, 4, and 12 weeks after surgery. Thereafter, rats were sacrificed by parcel, and bone samples were collected. New bone formation in the bone defect area was investigated with Micro-CT. Soft tissue healing, new bone formation, inflammatory response, dead bone formation and other indicators were observed using HE and Masson staining. The expressions of RANKL and OPG involved in bone remodeling were detected using ELISA. Results Rats in experimental maxillofacial group showed non-healed bone defect and exposed necrotic bone, while rats in control group exhibited continuous cortical bone and normal bone remodeling according to Micro-CT results. The experimental tibial bones showed thicker bone cortex, denser mineral density and faster bone remodeling progress than that of the control group. BV/TV ratio in the experimental tibial group 4 weeks and 12 weeks after surgery increased significantly compared with the control group (P<0.05), while the difference between the two groups in maxillofacial bones has no statistical significance. Histological staining presented major clinical and histopathological manifestations of the human bisphosphonate-related osteonecrosis of the jaw(BRONJ), including non-healed or delay-healed mucosa, exposed necrotic bone, osseous sclerosis and inflammatory infiltration in zoledronate-treated rats. While rats in control group exhibited normal reepithelialization and bone remodeling, the experimental tibial bones showed increased cortical thickness, bone formation, trabecular bone volume and bone mineral density compared with the control group. Cytokines results showed that RANKL/OPG ratio in the experimental maxillofacial bones decreased significantly compared with the control group (P<0.05), while RANKL/OPG ratio in the experimental tibial bones increased significantly (P<0.05). Conclusion Zoledronate suppresses maxillofacial bone remodeling after tooth extraction, and causes BRONJ-like disease in rats, but promotes peripheral bone remodeling after bone trauma. RANKL/OPG ratio may play an essential role in the occurrence of BRONJ.