上皮間質轉換過程在許多生理及病理過程中扮演非常重要的角色，例如癌症與疾病演進、體內平衡及胚胎發育。上皮間質轉換過程透過改變細胞本身塑性及貼附行為以賦予細胞具有侵襲及遷移特性。文獻證實轉化生長因子可誘發及維持上皮間質轉換過程，使上皮細胞失去其極性及細胞與細胞之間連接，進而使細胞骨架進行重組及重建細胞與基質間之貼附狀況。
本研究為使用原子力顯微鏡之細胞探針技術以探討正常乳腺上皮細胞及其經轉化生長因子誘發上皮間質轉換後與第一型膠原蛋白基質間的貼附力量變化。上皮間質轉換之細胞表型則使用免疫螢光染色進行確認。
結果顯示，正常乳腺上皮細胞於轉化生長因子誘發48小時後生長較分散且細胞型態趨向纖維母細胞，其纖維型肌動蛋白分佈由表層網絡結構形成具整齊性排列束狀結構，而間質細胞之α平滑肌肌動蛋白的螢光表現較上皮細胞強。於力學量測方面，間質細胞呈現較高的貼附力量及作功，推測為上皮細胞經轉化生長因子刺激後，增加細胞與基質間的單一鍵結強度及數目所致。此外，增加細胞與基質接觸時間(30秒、60 秒及300 秒)會量測到較大的貼附力量及作功。期望此上皮細胞與間質細胞之力學行為能進一步提供闡釋上皮間質轉換特性，並對疾病診斷與治療上有所幫助。

The epithelial to mesenchymal transitions (EMT) plays crucial roles in many physiological and pathological processes such as carcinoma and disease progression, homeostasis, and embryonic development. EMT endows cells with invasive and migratory properties through complex changes in cell plasticity and adhesion behavior. Transforming growth factor-β (TGF-β) is well-documented to initiate and maintain EMT that causes loss of cell-cell junction and epithelial polarity, reorganization of cytoskeleton, and remodeling of cell-matrix adhesion.
The purpose of present study was to compare the detachment forces between the cells and collagen type I substrate using cell probe approach of atomic force microscopy (AFM). Two kinds of cells, normal murine mammary gland (NMuMG) cells and NMuMG cells after EMT with TGF-β1 induction, were used in this study. The cell-substrate contact duration was set at 30 sec, 60 sec and 300 sec, respectively. The phenotype of EMT cells were confirmed and investigated by immunofluoresent stain.
The morphology of NMuMG cells grew into separately and fibroblast-like shape after 48-hour TGF-β1 induction, and F-actin exhibited from cortical actin network to linear and more organized bundles of actin filaments. Mesenchymal cells presented extensive alpha-smooth muscle actin (α-SMA). Nevertheless, TGF-β1 induction led the transition of epithelial cells to higher detachment force and work, which might be contributed by the strength and number of adhesive units. The increasing cell-substrate contact duration (30 sec, 60 sec and 300 sec) resulted in higher cell detachment force and work for both the epithelial cells and the mesenchymal cells. In accordance with cell appearances and mechanical properties proven, TGF-β1 plays a promising inducer for EMT. Furthermore, the mechanical behavior related to epithelial cells and mesenchymal cells could provide better elucidation for the advanced characteristics of EMT and contribute to disease diagnosis and relevant treatment in clinical applications.

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