published_or_final_version / abstract / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

吸煙是引起骨質疏鬆症的因素之一。臨床研究清楚表明吸煙者的骨密度降低，但其他干擾因素可能掩蓋了吸煙對骨頭的不良效果。使用動物模型用以研究吸煙和骨質疏鬆症之間是否有直接的因果關係與它潛在的機制是有必要的。為此，我們使用年輕和雌激素耗盡的小鼠作被動吸煙模型以及小鼠成骨細胞和破骨細胞株來作研究。 / 年輕的Balb/c小鼠暴露於2%或4% (v/v)的香煙煙霧中，代表中度和重度吸煙的人。骨代謝生物標誌物明顯增加，4%吸煙組在14週後股骨的微觀結構4%顯著下降，這相等於人類吸煙12年。此外，雌性Balb/c小鼠進行4%吸煙和/或卵巢切除術(OVX)。吸煙+OVX組增加血清中骨轉換指標水平。4%吸煙組的股骨生長板較薄。μ-CT數據進一步表明，相對骨體積(BV / TV)和結構模型指數(SMI)在吸煙組有顯著影響，而且在吸煙+ OVX組上有更大程度的影響。 / 在細胞研究中使用氯仿(CSE)和乙醇的香煙提取物(ESE)。CSE抑制小鼠細胞株RAW 264.7形成破骨細胞，並刺激小鼠成骨細胞株的分化和功能。這個與體內研究矛盾的結果暗示直接從煙霧中提取的化學成分並不是引起骨質疏鬆的元兇。影響骨代謝的很可能是其他從煙霧中生成的活性代謝物和一些吸煙引起的內源性激素物質。在吸煙引起的骨質流失中，這些代謝物或內源性物質可能是非常重要的。 / 有見及此，4%吸煙小鼠的血清用以研究其對成骨細胞和破骨細胞活動的影響。吸煙小鼠血清顯著降低在成骨細胞中鹼性磷酸酶(ALP)活性和鈣沉積，一些成骨細胞標記基因和蛋白表達均下降，而且 Wnt/β-catenin信號通路下調。此外，吸煙小鼠血清顯著增加形成破骨細胞的數量，組織蛋白酶K的基因和蛋白表達增加，在NF-κB和p-38 MAPK信號傳導途徑的信號分子表達增加。 / 總而言之，大量吸煙可能影響年輕小鼠和雌激素耗竭小鼠的骨代謝和微結構，通過類似的行動機制，人類也可能有同樣的骨疾病風險。這項研究揭示了吸煙導致的骨質疏鬆症在青少年和絶經後婦女的發病機制。這也給我們線索如何預防和治療與吸煙有關的骨骼疾病。這項研究還傳達了一個明確的信息：在年輕時應開始應控制吸煙。 / Cigarette smoking is one of the risk factors for osteoporosis. Clinical studies clearly showed that smokers have lower bone mineral density, but other confounding factors could mask the adverse actions of smoking on bones. Animal models are warranted to study the direct causal relationship between cigarette smoking and osteoporosis, and also the underlying mechanisms. In this regard, we used a mouse passive smoking model in both young and estrogen depleted mice, and the mouse osteoblast and osteoclast cell lines. / Young Balb/c mice were exposed to 2 or 4% (v/v) of cigarette smoke, similar to moderate or heavy smoking respectively in humans. Biomarkers for bone turnover were increased and bone microstructure of femur was significantly deteriorated after 4% smoking for 14 weeks which is similar to cigarette smoking for 12 years in humans. Furthermore, the effects of heavy smoking on ovariectomized mice were also investigated. Female Balb/c mice were subjected to 4% cigarette smoking and/or ovariectomy (OVX). Cigarette smoking together with OVX further increased the levels of bone turnover markers in serum. Femur growth plate was thinner in the 4% smoking group when compared to those in the SHAM- and OVX-operated groups. Micro-CT data further indicated that the relative bone volume (BV/TV) and structural model index (SMI) were significantly affected in the smoking groups, and to a greater extent in the 4% smoking + OVX group. / Chloroform (CSE) and ethanol smoke extracts (ESE) were used in cell studies. CSE suppressed the formation of osteoclasts, and stimulated the differentiation and function of mouse osteoblasts. These findings are contradictory to those found in in vivo study implying that chemical components directly extracted from cigarette smoke are not the culprits in causing bone disorder in animals. It is likely that other active metabolites from cigarette smoke and some endogenous hormonal substances released by cigarette smoking could affect bone metabolism. These active metabolites together with the endogenous bone hormones are perhaps crucial in smoking-induced bone loss in the body. / In view of this hypothesis, sera from 4% smoking mice were used to investigate their effects on osteoblast and osteoclast activities. It was found that the alkaline phosphatase (ALP) activity and calcium deposition in osteoblast were reduced significantly by the sera from smoking mice. Gene and protein expressions of some osteoblast markers were also decreased. The downregulation of Wnt/β-catenin signaling pathway was observed after the treatment with the serum obtained from the 4% smoking group. Moreover, the number of osteoclasts being formed was increased significantly by the smoking mouse serum. Cathepsin K gene and protein expressions were also induced. The increased expressions of the signaling molecules including NF-κB and p-38 MAPK were also observed. / In conclusion, heavy cigarette smoking could deteriorate bone metabolism and microstructures in young female and also estrogen depleted mice. The same kind of risk in bone disease may also apply to humans through similar mechanisms of action. This study sheds light in understanding the pathogenesis of smoking-induced bone disorders in teenagers and also postmenopausal women. It also gives us clues how to prevent and treat smoking related bone diseases. This study also conveys a clear message that cigarette smoking control should be started in young ages. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chan, Lok Yi Ruby. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 182-207). / Abstracts also in Chinese. / Chan, Lok Yi Ruby.