Extracellular Matrix Modulates Sensitivity of Hepatocytes to Fibroblastoid Dedifferentiation and Transforming Growth Factor β-induced Apoptosis
Extracellular Matrix Modulates Sensitivity of Hepatocytes to Fibroblastoid Dedifferentiation and Transforming Growth Factor β-induced Apoptosis
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DOI：
10.1002/hep.22880
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发表时间：
2009-06-01
期刊：
影响因子：
13.5
通讯作者：
Dooley, Steven
中科院分区：
文献类型：
--
作者：
Godoy, Patricio;Hengstler, Jan G.;Dooley, Steven
培养的肝细胞是研究肝脏对细胞因子反应机制的重要工具。然而，众所周知，在干燥的硬胶原单层上培养的肝细胞会去分化，失去专门的肝脏功能。在这项研究中，我们表明肝细胞去分化是细胞外基质触发的特定信号网络群的可逆结果。干燥僵硬的胶原蛋白通过 Src 激活粘着斑激酶 (FAK)，从而激活 Akt 和细胞外信号调节激酶 (ERK) 1/2 通路。 Akt 通过拮抗 p38 来抵抗转化生长因子 β (TGF-β) 诱导的细胞凋亡，而 ERK1/2 信号传导则打开上皮间质转化 (EMT) 的途径。通过抑制 Akt 或 Src 可以逆转细胞凋亡抵抗，并且可以通过阻断 ERK1/2 途径来消除 EMT。与坚硬的胶原蛋白相比，较软的胶原蛋白凝胶不会激活 FAK，从而使肝细胞保持对 TGF-β 诱导的细胞凋亡保持敏感的状态，并且不会经历 EMT。在该培养系统中，p38 的抑制以及组成型活性 Akt 的过度表达会导致细胞凋亡抵抗，而组成型活性 Ras 则会诱导 EMT。最后，我们证明，通过将细胞从干燥的硬胶原重新接种到软凝胶胶原，基质诱导的 EMT 是可逆的。我们的结果表明，体外肝细胞去分化是一个由 FAK 介导的 Akt 和 ERK1/2 信号驱动的主动过程。这会导致与体内肝细胞再生所观察到的类似的功能和形态学改变，并且当 Akt 和/或 ERK1/2 信号通路被拮抗时，这种改变是可逆的。结论：肝细胞可以以可逆的分化和去分化状态存在，并且可以通过操纵信号网络的关键因子来切换。 （肝病学 2009；49：2031-2043。）
Hepatocytes in culture are a valuable tool to investigate mechanisms involved in the response of the liver to cytokines. However, it is well established that hepatocytes cultured on monolayers of dried stiff Collagen dedifferentiate, losing specialized liver functions. In this study, we show that hepatocyte dedifferentiation is a reversible consequence of a specific signaling network constellation triggered by the extracellular matrix. A dried stiff Collagen activates focal adhesion kinase (FAK) via Src, leading to activation of the Akt and extracellular signal-regulated kinase (ERK) 1/2 pathways. Akt causes resistance to transforming growth factor beta (TGF-beta)-induced apoptosis by antagonizing p38, whereas ERK1/2 signaling opens the route to epithelial-mesenchymal transition (EMT). Apoptosis resistance is reversible by inhibiting Akt or Src, and EMT can be abrogated by blocking the ERK1/2 pathway. In contrast to stiff Collagen, a softer Collagen gel does not activate FAK, keeping the hepatocytes in a state where they remain sensitive to TGF-beta-induced apoptosis and do not undergo EMT. In this culture system, inhibition of p38 as well as overexpression of constitutively active Akt causes apoptosis resistance, whereas constitutively active Ras induces EMT. Finally, we show that matrix-induced EMT is reversible by replating cells from dried stiff to soft gel Collagen. Our results demonstrate that hepatocyte dedifferentiation in vitro is an active process driven by FAK-mediated Akt and ERK1/2 signaling. This leads to similar functional and morphological alterations as observed for regenerating hepatocytes in vivo and is reversible when Akt and/or ERK1/2 signaling pathways are antagonized. Conclusion: Hepatocytes can exist in a differentiated and a dedifferentiated state that are reversible and can be switched by manipulating the responsible key factors of the signaling network. (HEPATOLOGY 2009;49:2031-2043.)