Transitions in early embryonic atrioventricular valvular function correspond with changes in cushion biomechanics that are predictable by tissue composition
Transitions in early embryonic atrioventricular valvular function correspond with changes in cushion biomechanics that are predictable by tissue composition
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DOI：
10.1161/circresaha.107.148684
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发表时间：
2007-05-25
影响因子：
20.1
通讯作者：
Markwald, Roger R.
中科院分区：
文献类型：
--
作者：
Butcher, Jonathan T.;McQuinn, Tim C.;Markwald, Roger R.
内皮细胞垫对于在不断增加的血流动力学力下维持单向血流至关重要，但内皮细胞垫结构与房室交界功能力学之间的相互关系知之甚少。应用超声技术对17、21、25期鸡胚在Hamburger和汉密尔顿（HH）阶段的房室（AV）管运动和血流速度进行了定量研究。类似于胚胎斑马鱼的心脏，HH 17 AV段的功能就像一个抽吸泵，在心肌收缩高峰期，缓冲垫以波浪形扩张，在舒张期变得不可检测。到HH 25时，AV管对血液的活塞式推进几乎没有贡献，但缓冲垫起到阻挡器的作用，以接近恒定的厚度对抗血流。使用定制的细观力学测试系统，我们量化了开发AV垫的非线性伪弹性生物力学，并发现两个AV垫在HH 17和HH 25之间的有效模量增加。酶消化的主要结构成分胶原蛋白或糖胺聚糖导致明显不同的应力-应变曲线，暗示他们的个人贡献。混合物理论使用组织学确定的细胞，胶原蛋白和糖胺聚糖的体积分数表现出良好的预测垫材料的性能，无论阶段和垫的位置。这些结果对瓣膜发育具有重要影响，因为生物力学在刺激瓣膜发生事件方面可能比以前认为的发挥更大的作用。
Endocardial cushions are critical to maintain unidirectional blood flow under constantly increasing hemodynamic forces, but the interrelationship between endocardial cushion structure and the mechanics of atrioventricular junction function is poorly understood. Atrioventricular (AV) canal motions and blood velocities of embryonic chicks at Hamburger and Hamilton (HH) stages 17, 21, and 25 were quantified using ultrasonography. Similar to the embryonic zebrafish heart, the HH17 AV segment functions like a suction pump, with the cushions expanding in a wave during peak myocardial contraction and becoming undetectable during the relaxation phase. By HH25, the AV canal contributes almost nothing to the piston- like propulsion of blood, but the cushions function as stoppers apposing blood flow with near constant thickness. Using a custom built mesomechanical testing system, we quantified the nonlinear pseudoelastic biomechanics of developing AV cushions, and found that both AV cushions increased in effective modulus between HH17 and HH25. Enzymatic digestion of major structural constituent collagens or glycosaminoglycans resulted in distinctly different stress-strain curves suggestive of their individual contributions. Mixture theory using histologically determined volume fractions of cells, collagen, and glycosaminoglycans showed good prediction of cushion material properties regardless of stage and cushion position. These results have important implications in valvular development, as biomechanics may play a larger role in stimulating valvulogenic events than previously thought.