MR tagging demonstrates quantitative differences in regional ventricular wall motion in mice, rats, and men
MR tagging demonstrates quantitative differences in regional ventricular wall motion in mice, rats, and men
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DOI：
10.1152/ajpheart.01016.2005
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发表时间：
2006-11-01
影响因子：
4.8
通讯作者：
Yu, Xin
中科院分区：
文献类型：
--
作者：
Liu, Wei;Ashford, Marvin W.;Yu, Xin
大鼠和基因操纵的小鼠模型在探索心血管疾病的分子病因方面发挥了重要作用。然而，小鼠或大鼠和人类是否表现出相似的室壁运动模式还没有得到充分的研究。虽然解剖学和肌纤维构筑的相似性表明，室壁运动的基本模式可能是相似的，但心脏大小、心率和肌节蛋白亚型的显著差异可能会导致室壁力学的定量差异。为了进一步了解肌纤维收缩性能的基本机制，我们使用磁共振(MR)成像技术对小鼠、大鼠和人的室壁运动的局部和整体指数进行了量化。来自6名男性志愿者、6只Fischer 344大鼠和7只C57BL/6小鼠的常规电影和标记的心尖、脑室中和基础水平的磁共振图像。直接从电影图像计算形态参数和射血分数。心肌扭转(旋转角)、扭转(单位长度的净扭转)、周向应变和归一化径向缩短由标记图像的均匀应变分析计算。我们的数据显示，在这三个物种中，心室扭转是保守的，导致男性的扭转显著较小，以单位长度的净扭转衡量。然而，男性受试者的周向应变和归一化径向缩短都是最大的。尽管其他参数，如周向-纵向剪切应变还需要评估，收缩力学中这些差异的原因仍有待阐明，但扭转的保留似乎是心脏功能的基础，在将数据从动物外推到人类的研究中应予以考虑。
Rats and genetically manipulated mouse models have played an important role in the exploration of molecular causes of cardiovascular diseases. However, it has not been fully investigated whether mice or rats and humans manifest similar patterns of ventricular wall motion. Although similarities in anatomy and myofiber architecture suggest that fundamental patterns of ventricular wall motion may be similar, the considerable differences in heart size, heart rate, and sarcomeric protein isoforms may yield quantitative differences in ventricular wall mechanics. To further our understanding of the basic mechanisms of myofiber contractile performance, we quantified regional and global indexes of ventricular wall motion in mice, rats, and men using magnetic resonance (MR) imaging. Both regular cine and tagged MR images at apical, midventricular, and basal levels were acquired from six male volunteers, six Fischer 344 rats, and seven C57BL/6 mice. Morphological parameters and ejection fraction were computed directly from cine images. Myocardial twist (rotation angle), torsion (net twist per unit length), circumferential strain, and normalized radial shortening were calculated by homogeneous strain analysis from tagged images. Our data show that ventricular twist was conserved among the three species, leading to a significantly smaller torsion, measured as net twist per unit length, in men. However, both circumferential strain and normalized radial shortening were the largest in male subjects. Although other parameters, such as circumferential-longitudinal shear strain, need to be evaluated, and the causes of these differences in contractile mechanics remain to be elucidated, the preservation of twist appears fundamental to cardiac function and should be considered in studies that extrapolate data from animals to humans.