Department of Mechanical and Aerospace Engineering, North Carolina State University, R3158 Engineering Building 3, Campus Box 7910, 911 Oval Drive, Raleigh, NC, 27695, USA.
Biomech Model Mechanobiol. 2017 Dec;16(6):1911-1923. doi: 10.1007/s10237-017-0927-1. Epub 2017 Jun 19.
Venous valve incompetence has been implicated in diseases ranging from chronic venous insufficiency (CVI) to intracranial venous hypertension. However, while the mechanical properties of venous valve leaflet tissues are central to CVI biomechanics and mechanobiology, neither stress-strain curves nor tangent moduli have been reported. Here, equibiaxial tensile mechanical tests were conducted to assess the tangent modulus, strength and anisotropy of venous valve leaflet tissues from bovine jugular veins. Valvular tissues were stretched to 60% strain in both the circumferential and radial directions, and leaflet tissue stress-strain curves were generated for proximal and distal valves (i.e., valves closest and furthest from the right heart, respectively). Toward linking mechanical properties to leaflet microstructure and composition, Masson's trichrome and Verhoeff-Van Gieson staining and collagen assays were conducted. Results showed: (1) Proximal bovine jugular vein venous valves tended to be bicuspid (i.e., have two leaflets), while distal valves tended to be tricuspid; (2) leaflet tissues from proximal valves exhibited approximately threefold higher peak tangent moduli in the circumferential direction than in the orthogonal radial direction (i.e., proximal valve leaflet tissues were anisotropic; [Formula: see text]); (3) individual leaflets excised from the same valve apparatus appeared to exhibit different mechanical properties (i.e., intra-valve variability); and (4) leaflets from distal valves exhibited a trend of higher soluble collagen concentrations than proximal ones (i.e., inter-valve variability). To the best of the authors' knowledge, this is the first study reporting biaxial mechanical properties of venous valve leaflet tissues. These results provide a baseline for studying venous valve incompetence at the tissue level and a quantitative basis for prosthetic venous valve design.
静脉瓣膜功能不全与从慢性静脉功能不全（CVI）到颅内静脉高压等多种疾病有关。然而，尽管静脉瓣膜瓣叶组织的力学性能是 CVI 生物力学和力学生物学的核心，但既没有报道过应力-应变曲线，也没有报道过切变模量。在这里，进行了等双轴拉伸力学测试，以评估牛颈静脉静脉瓣膜瓣叶组织的切变模量、强度和各向异性。瓣膜组织在周向和径向方向上分别拉伸至 60%的应变，并为近侧瓣膜（即最靠近和最远离右心的瓣膜）和远侧瓣膜（即最靠近和最远离右心的瓣膜）生成瓣叶组织的应力-应变曲线。为了将力学性能与瓣叶微观结构和组成联系起来，进行了 Masson 三色和Verhoeff-Van Gieson 染色以及胶原蛋白测定。结果表明：（1）近侧牛颈静脉静脉瓣膜倾向于二叶瓣（即有两个瓣叶），而远侧瓣膜倾向于三叶瓣；（2）近侧瓣膜瓣叶组织在周向方向上的峰值切变模量约为正交径向方向的三倍（即近侧瓣膜瓣叶组织各向异性；[公式：见正文]）；（3）从同一瓣膜装置中切下的单个瓣叶似乎表现出不同的力学性能（即瓣膜内变异性）；（4）远侧瓣膜的可溶胶原蛋白浓度呈升高趋势高于近侧瓣膜（即瓣膜间变异性）。据作者所知，这是第一项报道静脉瓣膜瓣叶组织双轴力学性能的研究。这些结果为在组织水平上研究静脉瓣膜功能不全提供了基线，并为人工静脉瓣膜设计提供了定量基础。
