細胞生長在微小的環境中，其力學及生化特性對細胞生長及功能表現扮演相同重要的角色。細胞黏著是影響細胞功能行為的重要因子，如細胞型態、細胞貼附、細胞移動、細胞運動及分化等，同時也是組織工程中形成組織結構及整合細胞與生物材料最重要的一步。黏著行為會受到細胞本身生理調控及外界環境的影響，透過區域黏著增加細胞與基材間的黏著能力；區域黏著蛋白酶(FAK)是細胞中的蛋白質，細胞即透過FAK的調控與細胞外基質接觸並形成黏著點(FAs)，而細胞生長微環境中不同的基材硬度會影響細胞的功能，如細胞凋亡(apoptosis)、細胞分化(differentiation)、及癌細胞轉移(cancer invasion)。本研究將利用聚丙烯醯胺膠体(polyacrylamide gel)製成三種軟硬度不同的基材(1000Pa、33800Pa、玻璃基材)，利用細胞黏著力刮取機構及螢光觀測系統，探討細胞內FAK於不同硬度基材之表現對細胞黏著力的影響。本研究假設FAK為細胞中主要感測基材硬度的因子，選用三種不同特性的極性上皮細胞MDCK來釐清FAK的功能，分別為控制組(Vector control)、FAK基因過度表現組(FAK-WT)及無表現組(FRNK)。實驗結果顯示，細胞面積、細胞黏著力及刮取所需總能量-功，皆隨著基材硬度的增加而增加；過度表現FAK和無表現FAK兩組間，除了細胞面積和標準化後的黏著力外，其他參數皆有顯著差異；區域黏著蛋白酶於30kPa及1kPa基材上，能促進細胞攤附並增加對面積做標準化後的細胞黏著力，於三種硬度上，能增加細胞黏著力。本研究對FAK於不同基材上發揮的效益定義一個AI (affecting index)比，AI比值愈大表示FAK的效益愈大：於玻璃和30kPa的基材上，細胞黏著力及功之AI值相近，最大值發生在1Kpa軟性基材上，而細胞攤附面積之AI值於三種硬度的基材上幾乎相同；過度表現FAK基因的細胞，其AI值和基材硬度呈反比，無表現FAK的細胞則與基材硬度呈正比，推論FAK於較硬的基材上其效益比在軟性基材上來得小。

Both biochemical and mechanical properties of the microenvironment are equally important for cell growth and functional expression. Cell adhesion not only plays a critical role in cell physiology functions including morphology, spreading, migration, and differentiation, but also a critical step in the tissue engineering approach for maintenance of tissue structure and cell integration of biomaterial. The adhesion between cell-ECM is affected by intracellular regulations and extracellular environment, and is strengthened through focal adhesions. The focal adhesion kinase (FAK) at focal adhesions (FAs) is the major part for cell binding to the extracellular matrix (ECM). The substrate rigidity is playing an important factor for various cell behaviors, such as apoptosis, differentiation, and cancer invasion. In present study, we plate MDCK epithelial cell on glass surface, 1kPa, and 30kPa polyacrylamide gels, respectively. The FAK expression for substrate rigidity sensing and adhesion force management will be sty cytodetachment device and fluorescent microscopy. We hypothesize that FAK is the rigidity sensor in response to different rigidity of substrates. Different expression levels of FAK by gene Overexpression (FAK-WT) and knock-out (FRNK) will be also used to probe the function of FAK in rigidity sensing. The results indicate that cell spreading area, adhesion force, and work are increasing with increasing substrate rigidity. Except for cell area and normalized adhesion force, all parameters reach significantly different between FAK-WT and FRNK cells. FAK can enhance cell spreading and increase the normalized adhesion force on 30kPa and 1kPa gels. On three kinds of substrate rigidity, FAK can enhance adhesion force. We define a ratio of affecting index (AI) between FAK-WT, control and FRNK. Control, respectively. The AI ration means the effect of FAK on different substrate rigidity, the higher value of AI and the stronger effect of FAK. The AI ratio of adhesion force in glass dish and 30kPa gel are approximate the same, and the highest value occurs in 1kPa gel. The AI ratio of cell area is almost no difference between three kinds of substrate rigidity. Moreover, the affecting index of FAK-WT is inversely proportional to the substrate rigidity, but proportional to the substrate rigidity in FRNK cell. We suggest that the effect of FAK is weaker on stiffer substrate than on softer matrix.

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