Rowe Andrea J, Finlay Helen M, Canham Peter B
Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
J Vasc Res. 2003 Jul-Aug;40(4):406-15. doi: 10.1159/000072831. Epub 2003 Aug 8.
Collagen is the main matrix protein of the artery wall. We have used the known correlation between collagen birefringence and its mechanical properties to assess the wall structural integrity in brain arteries and their bifurcation regions, which are the sites of formation of saccular aneurysms. Segments of 28 brain arteries, including bifurcations, were pressure fixed and sectioned in one of three orthogonal planes. Measurements were taken by polarizing microscopy of the birefringence of collagen fibers at the apex of bifurcations and in the main layers of the artery wall - adventitia, media and intima. Dimensional data were obtained of the layers in order to estimate wall properties. Along the apex of the flow divider we measured a narrow band of collagen (birefringence 30% higher than the adjacent adventitia) providing strength and stiffness in that region. There is a thin cell-free outer layer of the tunica media (mean thickness 11 microm) comprised of densely packed coaligned collagen with high birefringence. From the fiber birefringence and directional alignment of the individual layers we calculated that the adventitia contributes about one third of circumferential and almost all of longitudinal strength of intracranial arteries.
胶原蛋白是动脉壁的主要基质蛋白。我们利用胶原蛋白双折射与其力学性能之间的已知相关性，来评估脑动脉及其分叉区域（即囊状动脉瘤形成部位）的血管壁结构完整性。对28条脑动脉的节段（包括分叉处）进行压力固定，并在三个正交平面之一进行切片。通过偏振显微镜测量分叉顶端和动脉壁主要层（外膜、中膜和内膜）中胶原纤维的双折射。获取各层的尺寸数据以评估血管壁特性。沿着分流器顶端，我们测量到一条狭窄的胶原带（双折射比相邻外膜高30%），为该区域提供强度和刚度。中膜有一层无细胞外层（平均厚度11微米），由紧密排列、高度双折射的平行胶原组成。根据各层纤维的双折射和方向排列，我们计算出，外膜对颅内动脉周向强度的贡献约为三分之一，对纵向强度几乎贡献了全部。
