Marom Y, Gengrinovitch S, Shalev E, Shilo D
Department of Mechanical Engineering, Technion, Haifa 3200003, Israel.
Rappaport Faculty of Medicine, Technion, Haifa 3200003, Israel; Trottner Laboratory for Research, Emek Medical Center, Afula 18101, Israel.
J Biomech. 2020 Jul 17;108:109896. doi: 10.1016/j.jbiomech.2020.109896. Epub 2020 Jun 13.
We study irreversible collagen arrangement processes in ex-vivo human amnions subjected to inflation tests, which simulate the mechanical conditions prior to and during the initiation of labor uterine contractions. The investigation is focused on the center of the membrane where the stresses are maximal and equibiaxial. Second harmonic generation reveals an unexpected collagen rearrangement in the compact layer that is responsible for the structural integrity of the fetal membrane. The observed bundling and alignment of the collagen fibers indicate a deviation from the expected equibiaxial stress state. The statistical analysis of the fiber orientations provides information on two driving forces for collagen alignment: microscale flaws and macroscale deviation from the equibiaxial strain. As the pressure increases, the macroscale effect becomes dominant, and a high density of fibers that are aligned along a specific direction is observed. A model that explains these observations and relates them to the material properties is presented. The results of this study indicate that a temporal increase in intrauterine pressure or uterine cervix dilatation causes irreversible changes in collagen molecular connections that may lead to biological changes, such as the initiation of term and preterm labor.
我们研究了在体外人羊膜上进行的充气试验中的不可逆胶原蛋白排列过程，该试验模拟了分娩子宫收缩开始前及期间的机械条件。研究聚焦于膜的中心，此处应力最大且为双轴等向应力。二次谐波产生揭示了致密层中意外的胶原蛋白重排，这对胎膜的结构完整性至关重要。观察到的胶原纤维束集和排列表明偏离了预期的双轴应力状态。对纤维取向的统计分析提供了关于胶原蛋白排列的两种驱动力的信息：微观尺度的缺陷和双轴应变的宏观尺度偏差。随着压力增加，宏观尺度效应占主导，观察到沿特定方向排列的高密度纤维。提出了一个解释这些观察结果并将其与材料特性相关联的模型。本研究结果表明，子宫内压力或子宫颈扩张的时间性增加会导致胶原蛋白分子连接的不可逆变化，这可能会引发生物学变化，如足月和早产的开始。
