| 摘要: | 組織工程是利用細胞、支架以及訊息因子等三大要素進行組織修補，達到組織修復的目的。組織工程體外培養細胞，研究細胞新陳代謝，進而影響細胞在支架內生長情況，探討細胞增殖、隨機漫步、碰撞、接觸抑制等微觀行為。 本研究以數學模型模擬軟骨細胞在支架培養情況，探討葡萄糖、氧氣與乳酸濃度，以及酸鹼值對細胞代謝速率的影響。結果顯示在高葡萄糖濃度下，細胞代謝葡萄糖而生成乳酸，致使培養環境酸度增加，減緩細胞代謝速率，減低細胞對葡萄糖及氧氣的攝取。由於氧氣可獲得補充，使得在高酸的環境中，支架內氧氣濃度產生不減反增的情況。在低葡萄糖濃度條件，氧氣濃度不減反增情況則不明顯。以上結果可提供軟骨細胞體外培養代謝資訊，了解細胞培養對於養分消耗、乳酸分泌以及環境酸鹼值變化等作用的交互影響。 本論文亦結合連續體養分擴散方程式及離散體格狀自動機模型，建立靜態培養細胞生長模型，模擬細胞增殖、隨機漫步、碰撞、接觸抑制等微觀行為，以探討細胞移動與種殖模式對細胞生長的影響。細胞在支架內的移動速度會影響到整體細胞生長，在細胞培養初期，不移動細胞增殖速率較緩慢，增高細胞移動速率，會得到較高細胞體積分率。到培養後期，不移動細胞形成群落，養分擴散到支架內部，使細胞得到較高的體積分率，但是，高移動速度細胞因養分傳輸的阻礙，細胞增殖受到限制。在不同持續移動時間，細胞持續移動時間愈長，細胞碰撞與接觸抑制機率較高，細胞體積分率會降低。在不同初始種殖模式下，以中間種殖模式，因支架周圍較少細胞，使養分得以擴散至內部，最終可得到最高的細胞體積分率。本研究期望能將單一細胞在微觀上的行為詳實描述，提供組織工程體外培養上有用的模擬數據，並應用在實際細胞培養系統上，來改進細胞培養技術。 Tissue engineering integrates biomedicine and engineering by introducing engineering analysis into biomedical research in order to develop artificial tissue substitutes with complete biological functions. These tissue substitutes can be used to repair, maintain, or improve human tissues and organs. This study presents a mathematical model for simulating cartilaginous culture of chondrocytes seeded in scaffolds and investigating the effects of cell density, glucose, oxygen, lactate concentration, and pH value on cell metabolic rates. Results show that under high glucose concentration (HG) condition, cells are able to metabolize effectively and form large amounts of lactate, increasing acidity in the environment. This increased acidity reversely causes cell metabolic rate to decrease and consequently lower oxygen and glucose uptake. Since oxygen can be replenished through the free surface of the culture medium, oxygen concentration within the scaffold increases rather than decreases over time in acidic environment. In low glucose concentration (LG) conditions, however, oxygen concentration monotonically decreases with culture time. From the simulation results, additional information regarding in vitro culture of chondrocytes can be obtained. The correlations between nutrient consumption, lactate secretion and pH changes during cell culture are also understood. The nutrient metabolic model is then incorporates into a hybrid cellular automata model that combines the differential nutrient transport equation to investigate the nutrient limited cell-construct development for cartilage tissue engineering. Individual cell behaviors of migration, contact inhibition and cell collision, coupled with the cell proliferation regulated by nutrients concentration are studied. Using this model, this study investigates the influence of cell migration speed on the overall cell growth within the cellular scaffolds. It is found that intense cell motility can enhance initial cell growth rates. However, since cell growth is also significantly modulated by the nutrient contents, increasing cell motility may lead to reduced cell growth in the final time because concentrated cell population has been growing around the scaffold periphery to block the nutrient transport from outside culture media. Under different cell persistence time conditions, increasing the persistence time, cell collision and contact inhibition are increased, but the cell amount is decreased. This paper also compares cell growth in scaffolds with various seeding modes, and proposes a seeding mode with cells initially residing in the middle area of the scaffold that may efficiently reduce the nutrient blockage and result in a better cell amount for tissue engineering construct developments. Mathematical models help interpret experimental results and may serve as a reference for in vitro cell culture research of tissue engineering. |
