School of Engineering, Cardiff University, UK; School of Health Sciences, Birmingham City University, UK.
FET - Engineering, Design and Mathematics, University of West of England, UK.
Acta Biomater. 2023 Nov;171:166-192. doi: 10.1016/j.actbio.2023.09.044. Epub 2023 Oct 4.
Cardiac tissue growth and remodelling (G & R) occur in response to the changing physiological demands of the heart after birth. The early shift to pulmonary circulation produces an immediate increase in ventricular workload, causing microstructural and biomechanical changes that serve to maintain overall physiological homoeostasis. Such cardiac G & R continues throughout life. Quantifying the tissue's mechanical and microstructural changes because of G & R is of increasing interest, dovetailing with the emerging fields of personalised and precision solutions. This study aimed to determine equibiaxial, and non-equibiaxial extension, stress-relaxation, and the underlying microstructure of the passive porcine ventricles tissue at four time points spanning from neonatal to adulthood. The three-dimensional microstructure was investigated via two-photon excited fluorescence and second-harmonic generation microscopy on optically cleared tissues, describing the 3D orientation, rotation and dispersion of the cardiomyocytes and collagen fibrils. The results revealed that during biomechanical testing, myocardial ventricular tissue possessed non-linear, anisotropic, and viscoelastic behaviour. An increase in stiffness and viscoelasticity was noted for the left and right ventricular free walls from neonatal to adulthood. Microstructural analyses revealed concomitant increases in cardiomyocyte rotation and dispersion. This study provides baseline data, describing the biomechanical and microstructural changes in the left and right ventricular myocardial tissue during G & R, which should prove valuable to researchers in developing age-specific, constitutive models for more accurate computational simulations. STATEMENT OF SIGNIFICANCE: There is a dearth of experimental data describing the growth and remodelling of left and right ventricular tissue. The published literature is fragmented, with data reported via different experimental techniques using tissues harvested from a variety of animals, with different gender and ages. This prevents developing a continuum of data spanning birth to death, so limiting the potential that can be leveraged to aid computational modelling and simulations. In this study, equibiaxial, non-equibiaxial, and stress-relaxation data are presented, describing directional-dependent material responses. The biomechanical data is consolidated with equivalent microstructural data, an important element for the development of future material models. Combined, these data describe microstructural and biomechanical changes in the ventricles, spanning G &R from neonatal to adulthood.
心脏组织的生长和重塑（G & R）是在出生后心脏对生理需求变化的反应。向肺循环的早期转变会立即增加心室工作量，导致微结构和生物力学变化，以维持整体生理平衡。这种心脏 G & R 会持续一生。量化 G & R 引起的组织力学和微观结构变化越来越受到关注，与个性化和精准解决方案的新兴领域相吻合。本研究旨在确定四个时间点（从新生儿到成年）的猪心室组织的等双轴和非等双轴拉伸、应力松弛和潜在微观结构。通过双光子激发荧光和二次谐波产生显微镜对光学透明组织进行三维微观结构研究，描述了心肌细胞和胶原纤维的三维取向、旋转和分散。结果表明，在生物力学测试过程中，心肌心室组织具有非线性、各向异性和粘弹性行为。从新生儿到成年，左、右心室游离壁的刚度和粘弹性增加。微观结构分析显示，心肌细胞的旋转和分散同时增加。本研究提供了基础数据，描述了 G & R 过程中左、右心室心肌组织的生物力学和微观结构变化，这对于研究人员开发特定年龄的本构模型以进行更准确的计算模拟应该是有价值的。
缺乏描述左、右心室组织生长和重塑的实验数据。已发表的文献很分散，数据是通过不同的实验技术报告的，使用的是从各种动物身上采集的不同组织，具有不同的性别和年龄。这阻止了从出生到死亡的连续数据的发展，从而限制了可用于辅助计算建模和模拟的潜力。在这项研究中，呈现了等双轴、非等双轴和应力松弛数据，描述了与方向相关的材料响应。生物力学数据与等效微观结构数据相结合，这是开发未来材料模型的重要元素。综合这些数据描述了心室的微观结构和生物力学变化，跨越了从新生儿到成年的 G & R。
