Black Lauren D, Allen Philip G, Morris Shirley M, Stone Phillip J, Suki Béla
Department of Biomedical Engineering, Boston University.
Biophys J. 2008 Mar 1;94(5):1916-29. doi: 10.1529/biophysj.107.107144. Epub 2007 Nov 9.
The goal of this study was to determine how alterations in protein composition of the extracellular matrix (ECM) affect its functional properties. To achieve this, we investigated the changes in the mechanical and failure properties of ECM sheets generated by neonatal rat aortic smooth muscle cells engineered to contain varying amounts of collagen and elastin. Samples underwent static and dynamic mechanical measurements before, during, and after 30 min of elastase digestion followed by a failure test. Microscopic imaging was used to measure thickness at two strain levels to estimate the true stress and moduli in the ECM sheets. We found that adding collagen to the ECM increased the stiffness. However, further increasing collagen content altered matrix organization with a subsequent decrease in the failure strain. We also introduced collagen-related percolation in a nonlinear elastic network model to interpret these results. Additionally, linear elastic moduli correlated with failure stress which may allow the in vivo estimation of the stress tolerance of ECM. We conclude that, in engineered replacement tissues, there is a tradeoff between improved mechanical properties and decreased extensibility, which can impact their effectiveness and how well they match the mechanical properties of native tissue.
本研究的目的是确定细胞外基质（ECM）蛋白质组成的改变如何影响其功能特性。为实现这一目标，我们研究了经工程改造含有不同量胶原蛋白和弹性蛋白的新生大鼠主动脉平滑肌细胞所生成的ECM片的力学和破坏特性变化。样本在弹性蛋白酶消化30分钟之前、期间和之后进行了静态和动态力学测量，随后进行破坏试验。使用显微镜成像在两个应变水平测量厚度，以估计ECM片中的真实应力和模量。我们发现，向ECM中添加胶原蛋白会增加其硬度。然而，进一步增加胶原蛋白含量会改变基质组织，随后破坏应变会降低。我们还在非线性弹性网络模型中引入了与胶原蛋白相关的渗流来解释这些结果。此外，线性弹性模量与破坏应力相关，这可能有助于在体内估计ECM的应力耐受性。我们得出结论，在工程化替代组织中，改善力学性能与降低伸展性之间存在权衡，这可能会影响其有效性以及它们与天然组织力学性能的匹配程度。
