Liao Jun, Priddy Lauren B, Wang Bo, Chen Joseph, Vesely Ivan
Cardiovascular Tissue Biomechanics Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, 130 Creelman Street, Room 222, Mississippi State, MS 39762, USA.
J Heart Valve Dis. 2009 May;18(3):292-9.
The chordae tendineae, which form an important component of the mitral valve apparatus, experience continuous cyclic loading and are thus well-adapted for effectively storing and dissipating energy. An understanding of their microstructure would be expected to shed light on the mechanism of their remarkable durability.
In these studies, porcine mitral valve chordae from freshly slaughtered pigs were used. Histological samples of Picrosirius Red-stained and Movat's pentachrome-stained chordae were examined with optical microscopy and laser scanning confocal microscopy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the ultrastructure at high magnification.
Both, optical microscopy and SEM revealed that the waviness of collagen fibers was uniform across the thickness of the chordae, with no straight fibers in the core. Wavy fibers and fiber bundles were found to be in skewed-register, rather than transverse. Collagen fiber bundles were found to undulate in a three-dimensional path, rather than the planar waveform, as reported previously. TEM showed that different types of chordae had different fibril configurations. Marginal chordae had smaller diameters but a higher fibril density than did basal and strut chordae.
The configuration of collagen fibrils in the mitral valve chordae is more complex than initially thought, and different chordae have morphologies that are likely specific to their mechanical role in the mitral apparatus. These findings provide insight into possible improvements for chordal repair surgery, and form a structural basis for accurate computational modeling.
腱索是二尖瓣装置的重要组成部分，承受持续的周期性负荷，因此能很好地适应有效储存和消散能量。对其微观结构的了解有望揭示其非凡耐久性的机制。
在这些研究中，使用了刚屠宰猪的猪二尖瓣腱索。对经苦味酸天狼星红染色和莫瓦特五色染色的腱索组织学样本进行光学显微镜和激光扫描共聚焦显微镜检查。使用扫描电子显微镜（SEM）和透射电子显微镜（TEM）在高倍放大下研究超微结构。
光学显微镜和SEM均显示，胶原纤维的波纹在腱索厚度上是均匀的，核心部位没有直纤维。发现波浪状纤维和纤维束呈斜向排列，而非横向排列。胶原纤维束呈三维路径波动，而非先前报道的平面波形。TEM显示不同类型的腱索具有不同的原纤维构型。边缘腱索的直径较小，但原纤维密度高于基底腱索和支柱腱索。
二尖瓣腱索中胶原原纤维的构型比最初认为的更复杂，不同的腱索具有可能与其在二尖瓣装置中的机械作用相关的特定形态。这些发现为腱索修复手术的可能改进提供了见解，并为精确的计算建模奠定了结构基础。
