以斑馬魚模式動物探討雙磷酸鹽藥物對血管新生的影響

The effects of a bisphosphonate on angiogenesis using zebrafish as an in vivo animal model

許丹菁(Tan-Ching Hsu)

指導教授 ： 王若松 ； 張百恩

國立臺灣大學/牙醫專業學院/臨床牙醫學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.00274

摘要

目的：
雙磷酸鹽類藥物應用相當廣泛，在臨床上常用於治療骨質疏鬆症、惡性腫瘤全身性骨轉移、多發性骨髓瘤等病症上。然而，2003年美國口腔顎面外科醫師 Marx提出有雙磷酸鹽藥物相關顎骨壞死 (Bisphosphonate-related osteonecrosis of the jaw, BRONJ) 的案例。所有關於牙科的侵入性治療，如拔牙、牙結石刮除、牙周手術、植牙等，都要特別注意。因此，本實驗室期望可以了解雙磷酸鹽相關顎骨壞死的成因，以期可以找出可以預防、評估與治療的方法。
近年來有多篇研究對BRONJ提出主要有兩個可能的致病機轉：一個是雙磷酸鹽類藥物會抑制蝕骨細胞的作用，導致骨修復功能缺損；另外一個則是會抑制血管再生。本實驗室之前的研究方向，主要是針對藥物對骨細胞及蝕骨細胞的作用機制。結果發現，骨頭再生受到抑制，有生長間隙(bone gap)的情形。其中，尾鰭再生長度較短且不規則、TRAP的染色會呈現大範圍暈染的情形，也懷疑藥物會抑制血管新生作用。
因此本實驗的研究方向，會朝著bisphosphonate抑制血管新生的作用來進行。另外，也會加入mevalonate pathway下游生化產物-香葉基香葉醇 (geranylgeraniol, GGOH)進行挽救實驗(rescue experiment)，以期將來可以找出BRONJ治療的方向。

實驗材料與方法：
本實驗以斑馬魚的尾鰭再生作為研究BRONJ的動物模式，來觀察雙磷酸鹽對於血管新生作用的影響。使用基因轉殖斑馬魚(TG(fli1:EGFP)，在螢光顯微鏡下觀察血管的螢光表現。
將斑馬魚尾鰭切除後，每個組別分別養在飼育過濾水(對照組)、與不同濃度的Alendronate中 (2.5×10 -5M及5.0 ×10 -5M)，在截尾後第一天到第七天，連續觀察血管再生的表現。另外，也會加入GGOH，觀察是否可以回復藥物抑制血管新生的作用。

結果：
在血管新生的表現上，泡藥組別較晚形成接合橋狀 (anastomotic bridges)連結因截尾而開放的傷口。血管網絡 (vascular plexus)的長度較短，且相連血管的密度 (inter-vessel commissure density) 也會降低。因此實驗結果顯示，在有浸泡雙磷酸鹽的組別，血管新生作用會受到抑制，導致尾鰭再生及修復功能的異常甚至魚隻死亡，而且抑制作用會和雙磷酸鹽藥物的劑量有關。而在加入GGOH後，可以回復血管受抑制的情形。

總結：
利用基因轉殖斑馬魚，觀察血管新生的現象。實驗結果顯示在雙磷酸鹽的影響之下，血管新生會受到抑制，進而影響到傷口的癒合、骨頭修復與再生的能力。因此，臨床上常見服用此藥物的病人，會有BRONJ的情形產生。加入GGOH後，對抑制再生的現象，有顯著復原的情形，這也可以作為將來治療的方向。
由本實驗室的研究結果，可以推論血管新生作用與骨頭再生關係密切，其中的連結機制則需要更進一步的實驗來證實。

關鍵字

雙磷酸鹽 ； 斑馬魚 ； 顎骨壞死 ； 血管新生 ； TG(fli1:EGFP)基因轉殖斑馬魚

並列摘要

Objectives：
The prescriptions of bisphosphonates are world-wide, often used in osteoporosis, bone metastasis of malignant tumors, multiple myeloma. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) was first reported in 2003 by the American Oral and Maxillofacial Surgeons, Marx. Due to wound healing of the jaw bone was delayed after bisphosphonate use, all dentoalveolar surgeries were involved, such as tooth extraction, root planing, periodontal surgeries, or implantation. Dentists pay special attention to this topic and phenomenon. Thus, we would like to unveil the etiology of BRONJ, and hopping to find the preventive measures and treatment methods.
Several causative mechanisms of BRONJ have been proposed. Inhibition of osteoclast function and angiogenesis were considered to be the two main mechanism recently, leading to defect in bone remodeling. The direct mechanism of action was still unknown. To date, there is no effective therapy of the BRONJ. Bisphosphonates inhibit pyrophosphate synthase (FPPS) in the mevalonate pathway, with decreased synthesis of the downstream metabolites, geranylgeraniol (GGOH).
Therefore, the research goal of this experiment was to explore the effects of a bisphosphonate on angiogenesis, and demonstrate that the application of GGOH may reverse the adverse effects of bisphosphonates.

Materials and Methods：
We used transgenic zebrafish (TG (fli1:EGFP)) as an animal model to explore the effects of bisphosphonates on angiogenesis.
First of all, we amputated the zebrafish tail fin in half, and all fishes were divided into five groups according to breeding condition by concentration of Alendronate: the control group, 2.5 × 10-5M of Alendronate, 5.0 × 10-5M of Alendronate, 2.5 × 10-5M of Alendronate and GGOH, 5.0 × 10-5M of Alendronate and GGOH.
The observation of the angiogenesis took place on day 2, day 3, day 5 and day 7 after fin amputation by the fluorescence microscopy. Furthermore, these findings could help us understand the inhibited angiogenic function affected by bisphosphonates, and expecting to find the potential medication for BRONJ.

Results：
The results showed that the vascular plexus and inter-vessel density were decreased after bisphosphonate treatments, suggesting that bisphosphonates could supress angiogenesis, and delayed wound healing.
The angiogenesis impaired by alendronate was reversed to normal in the presence of GGOH. Hence, systemic application of GGOH may reduce the adverse effects of bisphosphonate therapy.

Conclusion：
Our study in zebrafish provides a vivid animal model to investigate the role of angiogenesis in the BRONJ in vivo. This experiment showed that angiogenesis may be suppressed under the influence of bisphosphonates, leading to defects in wound healing, bone repair and regeneration eventually resulting in BRONJ. We also demonstrate that the impairing effects of alendronate on angiogenesis may be reversed by application of GGOH. And the results may further extend to the clinical applications in treating BRONJ.
In this study, the results suggested that there was close relationship between angiogenesis and osteogenesis, and the complex cross-linked mechanism would require further experiments to confirm.

並列關鍵字

Bisphosphonate ； zebrafish ； angiogenesis ； osteonecrosis ； TG(fli1:EGFP) transgenic zebrafish

參考文獻

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