Department of Pediatrics, Emory University School of Medicine , Atlanta, Georgia.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia.
Am J Physiol Heart Circ Physiol. 2019 Jul 1;317(7):H13-H25. doi: 10.1152/ajpheart.00161.2019. Epub 2019 Mar 29.
Engineered cardiac tissue and cardiomyocyte cell cultures offer wide opportunities for improved therapeutic intervention and laboratory heart models. Electrical field excitation is a common intervention in the production of engineered tissue and the investigation of the electrical properties of in vitro cell cultures. In this work, we use strength-duration relationships to investigate systematically factors influencing electrical excitability of two- (2D) and three-dimensional (3D) neonatal rat ventricular myocyte cultures. We find that the strength of the voltage pulse is negatively correlated with the threshold duration, as predicted by the Lapicque-Hill equation, and show that higher pacing frequencies require higher thresholds to capture paced cultures. We also study the impact of properties intrinsic to the 2D and 3D cultures on strength-duration relationships. We show that a smaller culture dimension, perpendicular anisotropic culture orientation with respect to electrical field, higher proportion of added fibroblasts, and TBX18-induced pacemaker reprogramming independently result in higher stimulation thresholds. These properties reflect the characteristics of the well-insulated endogenous pacemaking tissue in the heart (sinoatrial node) and should guide the engineering of biological pacemakers for improved outcomes. Gaps exist in the availability of in vitro functional assessment tools that can emulate the integration of regenerative cells and tissues to the host myocardium. We use strength-duration relationships of electrically stimulated two- and three-dimensional myocardial constructs to study the effects of pacing frequency, culture dimensions, anisotropic cell alignment, fibroblast content, and pacemaker phenotype on electrical excitability. Our study delivers electrical strength-duration as a quantifiable parameter to evaluate design parameters of engineered cardiac tissue constructs.
工程化心脏组织和心肌细胞培养为改善治疗干预和实验室心脏模型提供了广泛的机会。电场激发是工程化组织生产和体外细胞培养电特性研究中常用的干预手段。在这项工作中，我们使用强度-持续时间关系系统地研究了影响两种（2D）和三维（3D）新生大鼠心室肌细胞培养物电兴奋性的因素。我们发现，电压脉冲的强度与阈值持续时间呈负相关，这与 Lapicque-Hill 方程的预测一致，并表明更高的起搏频率需要更高的阈值来捕获起搏培养物。我们还研究了 2D 和 3D 培养物固有特性对强度-持续时间关系的影响。我们表明，较小的培养物尺寸、相对于电场的垂直各向异性培养方向、更高比例的添加成纤维细胞以及 TBX18 诱导的起搏器重编程独立导致更高的刺激阈值。这些特性反映了心脏（窦房结）中具有良好绝缘的内源性起搏组织的特征，应指导生物起搏器的工程设计以获得更好的结果。 目前缺乏能够模拟再生细胞和组织与宿主心肌整合的体外功能评估工具。我们使用电刺激的 2D 和 3D 心肌构建体的强度-持续时间关系来研究起搏频率、培养物尺寸、各向异性细胞排列、成纤维细胞含量和起搏器表型对电兴奋性的影响。我们的研究提供了电强度-持续时间作为可量化的参数来评估工程化心脏组织构建体的设计参数。
