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  • 學位論文

年齡以及運動對於成年斑馬魚軟骨組織持恆作用之影響

The Effect of Age and Exercise on Tissue Homeostasis of Cartilage in Adult Zebrafish (Danio rerio)

指導教授 : 劉逸軒

摘要


退化性骨關節炎為一種關節軟骨退化性疾病,特別在老年人身上發生。雖然目 前對於運動與否造成關節軟骨之利與弊仍沒有足夠之證據,卻仍然相信運動所造 成的物理性壓力與年齡的增長是導致關節退化的主要原因。而究竟關節軟骨是如 何走向退化之機制卻不得而知。近期的研究顯示,斑馬魚隨著年齡增長會出現類 似退化性骨關節炎的現象;而給予年幼斑馬魚運動刺激,亦能促使關節軟骨的發 育。因此,為了了解年齡以及運動這兩項因素是如何影響關節軟骨之生理持恆, 本試驗以四月齡及十二月齡之成年斑馬魚作為觀察不同年齡在軟骨持恆之影響; 同時也設計一套斑馬魚的劇烈運動裝置,令十二月齡之斑馬魚接受劇烈運動訓 練,並觀察軟骨組織之變化。在體型測量與電腦斷層掃描之結果中,我們發現斑 馬魚儘管在性成熟後其體成熟卻尚未達到完全,隨著年齡增長,其體型大小與骨 質密度仍持續上升;而相反的,劇烈的運動訓練卻會造成斑馬魚體長與體重之下 降,並抑制原本穩定成長的骨質密度。在量化軟骨組織胞外基質之染色中,第二 型膠原蛋白隨著年齡增長與運動訓練皆有顯著上升之趨勢;但整體醣胺聚醣之表 現僅隨著軟骨組織發育而擴張它的分佈範圍。有趣的是,我們發現十二月齡之斑 馬魚比起四月齡之組別,其軟骨組織內之細胞數量明顯下降,但在運動試驗組之 間並沒有差異。而進一步在細胞凋亡之試驗中,我們觀察到十二月齡之斑馬魚在 軟骨組織內之凋亡比率亦確實較高,說明年齡增長而引發的軟骨退化很有可能是 軟骨細胞持續凋亡所導致。最後,利用溴化去氧尿苷標記細胞增殖效率,我們發 現四月齡之成年斑馬魚其軟骨細胞之新生成作用較為旺盛,且組織內具有軟骨胚 細胞 (chondroblast) 之存在,以維持軟骨組織之替換更新。但相對的,在十二月齡 之組別則幾乎觀察不到具有增殖能力的軟骨細胞。綜合上述之結果,本試驗認為 年齡之增長確實是影響關節軟骨持恆作用之主要因素,它能藉由降低組織內細胞 更新之來源而導致。此外,我們亦證實斑馬魚適合作為研究關節軟骨在年齡增長 過程逐漸退化之動物模式,在未來可繼續探討其可能的機制發生。

並列摘要


Osteoarthritis is the degeneration of joint, especially the hyaline cartilage. Both age and exercise are considered critical risk factors for osteoarthritis, although the evidence on whether the exercise beneficial or a risk for osteoarthritis remains controversial. Recent studies suggested that aging-related degeneration of the spinal cartilage in zebrafish resembles the progress of osteoarthritis, while the development of cartilaginous tissue in zebrafish larvae can be altered by swim training. In this study, the spinal cartilages of 4- and 12-month old zebrafish were compared to study the mechanism of age-induced osteoarthritis. In addition, a swim-tunnel device was designed and created to evaluate the effect of intensive exercise on spinal cartilage in adult zebrafish. According to the body measuring, both age and exercise altered the body length and body weight. In addition, in micro-CT image, spinal bone mineral density of 12-month old zebrafish, which was stronger than 4-month old zebrafish, was affected by exercise training. Moreover, quantitative analysis of immunohistochemistry indicated that cartilaginous contents of the extracellular matrix, type II collagen, was significantly increased in both experimental groups. However, in Safranin O staining, the distribution of glycosaminoglycans was expanded only in age group. Interestingly, histochemistry staining showed that hematoxylin positive nuclear counts were higher in 4-month old zebrafish than in 12-month old. Indeed, terminal deoxynucleotidyl transferase dUTP nick end labeling displayed that the spinal cartilage of 12-month zebrafish has higher percentage of apoptotic cells. Moreover, although bromodeoxyuridine staining indicated that cell proliferation is not affected by excessive exercise, the 4-month old zebrafish has significantly more newly proliferated cells and chondroblast than the ones of 12-month old. Taken together, our results indicated that aging is a critical factor to compromise cartilage homeostasis due to the loss of chondrocyte neogenesis. Furthermore, we demonstrated that zebrafish is an excellent model to study aging process such as the mechanisms for cartilaginous homeostasis and osteoarthritis.

參考文獻


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