Dexamethasone是一種合成的葡萄糖皮質素，經常被添加在細胞培養液裡，以促進造骨母細胞的生長與分化。但有關dexamethasone對於造骨母細胞在生長與分化上的影響，仍然是有很大的爭議性的。實驗的模型、實驗中使用的劑量以及作用的時間長短，都會影響實驗的結果。不同的學者，採用不同的實驗設計，得到不同的實驗結果。針對這樣的現象，我們想要了解，如果在相同的實驗模型、相同的作用時間之下，使用不同濃度的dexamethasone，dexamethasone會如何的對造骨母細胞的生長與分化產生影響呢？如果使用相同濃度的dexamethasone、相同的作用時間，實驗模型不同，對於dexamethasone的反應，在生長與分化上又是如何呢？我們以SD rat的成鼠長骨骨髓以及胎兒頭蓋骨造骨母細胞做為實驗模型，分別在細胞培養液裡添加10-8、 10-7、10-6 M的dexamethasone，然後用MTT assay來比較細胞在生長方面的差異。我們用Alkaline phosphatase staining以及Alkaline phosphatase activity assay來比較不同的dex濃度對於這些樣本在鹼性磷酸脢表現上的影響。我們也利用Alizarin red S staining、calcium assay來了解dexamethasone的濃度對於造骨母細胞在骨質沉積上的影響。我們使用Real time RT PCR偵測細胞BSP和osteocalcin的表現，藉此了解dexamethasone的濃度對於造骨母細胞在基因表現上的影響。實驗的結果顯示，在細胞生長方面，10-8M dex有助於成鼠長骨骨髓造骨母細胞的生長，但濃度太強時，對生長反而產生抑制的效果；而dexamethasone劑量上的變化對於胎兒頭蓋骨造骨母細胞的生長，影響不大。在細胞分化方面，成鼠長骨骨髓造骨母細胞的各項分化指標，在10-8M dex誘導下，有比較突出的表現，但當濃度增加時，對細胞分化的促進效果反而相對減弱；以 SD rat的胎兒頭蓋骨造骨母細胞作為實驗模型，10-6M的誘導效果比10-7M 和10-8M的好，比較高的劑量對於胎兒頭蓋骨造骨母細胞的分化並不會產生抑制的作用。Dexamethasone的劑量變化和實驗模型的不同，都會影響造骨母細胞對於dexamethasone的反應。藉由本實驗，我們對dexamethasone的劑量在造骨母細胞生長分化上的影響，有更清晰的了解。我們希望我們的研究成果對於造骨母細胞的培養與研究上能有所貢獻，並有助於日後骨組織工程學在人工牙根手術及顎骨重建的發展。

　Dexamethasone is a synthetic glucocorticoid, and is added in cell culture medium to stimulate proliferation and differentiation of osteoblasts. According to literature review, there is still much controversile over this issue. Study models, dosage of dex, and reaction duration have been known to influent the response of osteoblasts to dex. Different study designs make different results. The aim of our study were to testify the effects of dex over the proliferation and differentiation of osteogenic stromal cells. In our research model, the primary cultured osteoblasts were harvested from the bone marrow of long bones of adult SD rats and from the calvaria of fetal SD rat . We added 10-8 M,10-7 M and 10-6 M dex to cell culture medium, and then MTT assay was processed to compare the difference in cell proliferation. We used alkaline phosphatase staining and alkaline phosphatase activity assay to compare the dosage effects of dexamethasone on ALP expression. We also applied Alizarin red S staining and calcium assay to assess the dosage effects of dexamethasone on bony deposition. Real time RT PCR was performed to evaluate BSP and osteocalcin mRNA expression. Our results showed that 10-8 M dex stimulated cell proliferation of osteoblasts from bone marrow significantly, but higher concentrations caused inhibit effects. We also found that dexamethasone did not have any significant effects on proliferation of osteoblasts from fetal calvaria. Under the stimulation of 10-8 M dex, osteoblasts from bone marrow had the most obvious expression in all of the differentiation markers; increasing the dexamethasone dosage did not increase the induction effects. To osteoblasts from fetal calvaria, 10-6 M dex had the best stimulation effect on cell differentiation; higher concentrations did not inhibit osteogenesis. We hope our study results can make benefit for future research in bone tissue engineering. In conclusion, 10-8 M dex has the modest osteogenic effects on these osteogenic stromal cells in both proliferation and differentiation. The results of this study can make benefit for the future research in bone tissue engineering, such as in dental implantation and jaw bone reconstruction.

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