正常的組織細胞無法以懸浮的方式生存於流體中，他們必須黏附於較硬的基質上以利其伸展並增生。然而，腫瘤細胞缺乏這樣的生長特性。在臨床上，腫瘤比正常組織來的硬，故臨床醫師常用觸診的方式診療腫瘤。已有許多文獻指出，細胞外間質會影響細胞的生長、存活率、分化及移動；另外，也有研究指出不同軟硬度的膠原蛋白會以一種未知的機制影響細胞功能。在我們的實驗中，我們分別利用不同軟硬度的基材：培養皿、培養皿鋪上較薄的一層膠原蛋白（二者彈力係數大於Giga 帕）以及培養皿鋪上一層較厚的膠原蛋白（彈力係數約為20 帕）的環境來比較正常子宮頸上皮細胞以及癌化的子宮頸上皮細胞（SiHa）培養在不同的軟硬度基材上的影響，實驗結果發現正常的子宮頸上皮細胞養在軟的基質上（培養皿上鋪較厚的膠原蛋白）時，正常的子宮頸上皮細胞會有皺縮以及細胞凋亡的現象。深入探討其分子機轉發現軟性基質會引起正常子宮頸上皮細胞內的酵素μ-calpain的活化和引起細胞內質網的鈣離子濃度上升以及填充式鈣離子湧入 (capacitative calcium entry)增加的現象。接著，我們利用鈣離子螯合劑螯合細胞內的鈣離子，實驗結果顯示，細胞內μ-calpain的活化會減少而細胞凋亡的現象也會降低。相反地，在癌化的子宮頸上皮細胞則沒有明顯的觀察到細胞形態的改變以及細胞凋亡和細胞內鈣離子濃度上升的現象。綜合以上結果，我們認為軟性基質會去調控正常子宮頸上皮細胞的生長及細胞的凋亡的現象，而這種現象是由於細胞內的鈣離子失衡導致細胞內calpain活化的緣故。

　　Normal tissue cells are generally not viable when suspended in a fluid. Such cells must adhere to a solid support and thus are able to stretch for proliferation. Tumorous tissues however are more rigid due to a stiff extracellular matrix which enables clinicians to diagnose tumors subjectively based on tissue rigidity by palpation. Several studies have suggested that extracellular matrix rigidity influences cell growth, viability, differentiation and motility. However, different rigidities of adhesive collagen substrate affect cellular functions with unclear mechanisms. Here, we cultured the normal cervical epithelial cells and cervical cancer cells on substrates of different rigidities and compared the cell type-specific responses. The culture dish was coated with a very thin layer of collagen gel (control group) or overlaid with collagen gel (soft substrate). Detected by the dynamic mechanical analyzer, the substrate rigidity of control group is more than 1 giga pascal, similar to that of culture dish without any coated substances. In contrast, overlaying the culture dish with collagen gel remarkably decreased the substrate rigidity to 30–100 pascals. Normal cervical epithelial cells contracted as they grew on collagen gel and the apoptotic bodies obviously appeared with time. μ-calpain was activated when normal cervical epithelial cells cultured on collagen gel. In addition, soft substrate caused elevated cytosolic Ca2+, Ca2+ overload in endoplasmic reticulum and upregulation of capacitative calcium entry. Ca2+ chelator partially rescued the collagen-gel induced apoptosis by inhibiting μ-calpain activation. In contrast, for cervical cancer cells cultured either on collagen gel or on gel-coated dish, there was no significant change in cell morphology and positive Annexin V staining. In conclusion, soft substrate regulates growth and apoptosis of normal cervical epithelial cells but not cervical cancer cells by calpain activation via the disturbance of Ca2+ homeostasis.

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