Analysis of Heterogeneous Deformation in the Wall of Rabbit Thoracic Aorta at Microscopic Level
Analysis of Heterogeneous Deformation in the Wall of Rabbit Thoracic Aorta at Microscopic Level
复制标题
DOI：
10.14326/abe.8.7
复制
发表时间：
2019-01-01
影响因子：
1
通讯作者：
Matsumoto, Takeo
中科院分区：
文献类型：
--
作者：
Fan, Yong;Wang, Junfeng;Matsumoto, Takeo
主动脉壁在机械刺激的作用下会改变其尺寸和力学性能。由于这些变化是由壁内细胞驱动的，而且它们的力学反应与核变形密切相关，因此有必要在微观水平上研究主动脉壁的变形。为此，我们制作了200亩厚的兔胸主动脉环-径向和纵-径向切片，在显微镜下分别沿周向和纵向拉伸。采用Hoechst33342免疫组织化学染色方法检测血管平滑肌细胞(SMC)细胞核。每个切片重复拉伸4%，每一步都捕捉细胞核的荧光图像以及弹性蛋白的自体荧光。从荧光图像中得到宏观和微观拉伸比。局部格林应变是由沿圆周方向拉伸的试件中核间距离的变化来计算的。周向局部组织应变是宏观组织应变的0.8~2.1倍，说明主动脉壁变形在微观水平上是不均匀的。相邻弹性层之间的剪切变形在特定位置很明显，导致了高达10%的剪切应变。我们还从周向和纵向拉伸试件中核形状的变化来评估组织变形和核变形之间的关系。在周向拉伸时，由细胞核长度计算的应变不到宏观应变的70%，这表明SMC的核比胞液成分要坚硬得多。在整个拉伸过程中，部分核团发生了明显的旋转，平均旋转角度为5度，最大旋转角度为11度。在纵向拉伸中，核长度的变化并不显著，这表明机械刺激对SMC的影响可能较小，正如先前报道的那样。目前的研究表明，细胞外基质和细胞核的变形都是高度不均匀的，这可能对血管生物学产生深远的影响。
Aortic wall changes dimensions and mechanical properties in response to mechanical stimulation. As these changes are driven by the cells inside the wall, and their mechanical response has been suggested to exhibit a close correlation with nuclear deformation, it is necessary to study the deformation of the aortic wall at microscopic level. Hence, we obtained 200-mu m-thick slices of rabbit thoracic aortas in the circumferential-radial and longitudinal-radial planes, and stretched them in the circumferential and longitudinal directions, respectively, under a microscope. The nuclei of smooth muscle cells (SMCs) were stained with Hoechst33342. Each slice was repeatedly stretched stepwise by 4%, while the fluorescence images of the cell nuclei as well as the elastin auto-fluorescence were captured at each step. Macroscopic and microscopic stretch ratios were obtained from the fluorescence images. Local Green strain was calculated from the change in internuclear distance in a specimen stretched in the circumferential direction. The local tissue strain in the circumferential direction was 0.8 to 2.1 times the macroscopic tissue strain, indicating that the aortic wall deformation was heterogeneous at microscopic level. The shear deformation between adjacent elastic laminas was evident at specific locations, resulting in a shear strain as large as 10%. We also evaluated the relationship between tissue deformation and nuclear deformation from the change in nuclear shape in the specimen stretched in the circumferential and longitudinal directions. In the circumferential stretch, the strain calculated from the length of the nuclei was less than 70% of the macroscopic strain, suggesting that the nuclei of the SMCs are much stiffer than the cytosolic components. Some nuclei rotated noticeably in response to the stretch, and the average and maximum rotation angle was 5 degrees and 11 degrees, respectively, during the entire stretching process. In the longitudinal stretch, the change in nuclear length was not significant, suggesting that mechanical stimulation to the SMCs may be smaller in this direction, as reported previously. The present study shows that the deformations of both the extracellular matrix and cell nuclei are highly heterogeneous, which may have a profound effect on the vascular biology.