Laboratory for the Study of Molecular Biointerfaces, Department of Oral Histology and Developmental Biology, Program of Cell and Developmental Biology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749, Republic of Korea.
Biomaterials. 2012 Apr;33(10):2902-15. doi: 10.1016/j.biomaterials.2011.12.051. Epub 2012 Jan 13.
The proliferation of anchorage-dependent cells of mesenchymal origin requires the attachment of the cells to substrates. Thus, cells that are poorly attached to substrates exhibit retarded cell cycle progression or apoptotic death. A major disadvantage of most polymers used in tissue engineering is their hydrophobicity; hydrophobic surfaces do not allow cells to attach firmly and, therefore, do not allow normal proliferation rates. In this study, we investigated the molecular mechanism underlying the reduced proliferation rate of cells that are poorly attached to substrates. There was an inverse relationship between the activity of the small GTPase RhoA (RhoA) and the cell proliferation rate. RhoA activity correlated inversely with the strength of cell adhesion to the substrates. The high RhoA activity in the cells poorly attached to substrates caused an increase in the activity of Rho-associated kinase (ROCK), a well-known effector of RhoA that upregulated the activity of phosphatase and tensin homolog (PTEN). The resulting activated PTEN downregulated Akt activity, which is essential for cell proliferation. Thus, the cells that were poorly attached to substrates showed low levels of cell proliferation because the RhoA-ROCK-PTEN pathway was hyperactive. In addition, RhoA activity seemed to be related to focal adhesion kinase (FAK) activity. Weak FAK activity in these poorly attached cells failed to downregulate the high RhoA activity that restrained cell proliferation. Interestingly, reducing the expression of any component of the RhoA-ROCK-PTEN pathway rescued the proliferation rate without physico-chemical surface modifications. Based on these results, we suggest that the RhoA-ROCK-PTEN pathway acts as a molecular switch to control cell proliferation and determine anchorage dependence. In cells that are poorly attached to substrates, its inhibition is sufficient to restore cell proliferation without the need for physico-chemical modification of the material surface.
依赖锚定的间充质来源细胞的增殖需要细胞附着在基质上。因此，与基质附着不良的细胞表现出细胞周期进程的延迟或凋亡死亡。组织工程中使用的大多数聚合物的一个主要缺点是它们的疏水性；疏水性表面不允许细胞牢固地附着，因此不允许正常的增殖率。在这项研究中，我们研究了细胞与基质附着不良时增殖率降低的分子机制。小 GTP 酶 RhoA（RhoA）的活性与细胞增殖率呈反比关系。RhoA 活性与细胞与基质的粘附强度呈反比。与基质附着不良的细胞中 RhoA 活性高导致 Rho 相关激酶（ROCK）的活性增加，ROCK 是 RhoA 的一种众所周知的效应物，可上调磷酸酶和张力蛋白同源物（PTEN）的活性。由此产生的激活的 PTEN 下调 Akt 活性，这对于细胞增殖是必需的。因此，与基质附着不良的细胞显示出低水平的细胞增殖，因为 RhoA-ROCK-PTEN 途径过度活跃。此外，RhoA 活性似乎与粘着斑激酶（FAK）活性有关。在这些附着不良的细胞中，FAK 活性较弱，无法下调限制细胞增殖的高 RhoA 活性。有趣的是，降低 RhoA-ROCK-PTEN 途径的任何组成部分的表达都可以挽救增殖率，而无需进行物理化学表面改性。基于这些结果，我们认为 RhoA-ROCK-PTEN 途径作为一种分子开关来控制细胞增殖并决定锚定依赖性。在与基质附着不良的细胞中，抑制其足以恢复细胞增殖，而无需对材料表面进行物理化学改性。
