Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany.
Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany; University Heart and Vascular Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
J Mol Cell Cardiol. 2022 Feb;163:97-105. doi: 10.1016/j.yjmcc.2021.10.001. Epub 2021 Oct 8.
One third of heart failure patients exhibit dyssynchronized electromechanical activity of the heart (evidenced by a broad QRS-complex). Cardiac resynchronization therapy (CRT) in the form of biventricular pacing improves cardiac output and clinical outcome of responding patients. Technically demanding and laborious large animal models have been developed to better predict responders of CRT and to investigate molecular mechanisms of dyssynchrony and CRT. The aim of this study was to establish a first humanized in vitro model of dyssynchrony and CRT.
Cardiomyocytes were differentiated from human induced pluripotent stem cells and cast into a fibrin matrix to produce engineered heart tissue (EHT). EHTs were either field stimulated in their entirety (symmetrically) or excited locally from one end (asymmetrically) or they were allowed to beat spontaneously.
Asymmetrical pacing led to a depolarization wave from one end to the other end, which was visualized in human EHT transduced with a fast genetic Ca-sensor (GCaMP6f) arguing for dyssynchronous excitation. Symmetrical pacing in contrast led to an instantaneous (synchronized) Ca-signal throughout the EHT. To investigate acute and long-term functional effects, spontaneously beating human EHTs (0.5-0.8 Hz) were divided into a non-paced control group, a symmetrically and an asymmetrically paced group, each stimulated at 1 Hz. Symmetrical pacing was clearly superior to asymmetrical pacing or no pacing regarding contractile force both acutely and even more pronounced after weeks of continuous stimulation. Contractile dysfunction that can be evoked by an increased afterload was aggravated in the asymmetrically paced group. Consistent with reports from paced dogs, p38MAPK and CaMKII-abundance was higher under asymmetrical than under symmetrical pacing while pAKT was considerably lower.
This model allows for long-term pacing experiments mimicking electrical dyssynchrony vs. synchrony in vitro. Combined with force measurement and afterload stimulus manipulation, it provides a robust new tool to gain insight into the biology of dyssynchrony and CRT.
三分之一的心衰患者表现出心脏的电机械活动不同步（表现为宽 QRS 复合波）。心脏再同步治疗（CRT）形式的双心室起搏可改善心脏输出和应答患者的临床预后。为了更好地预测 CRT 的应答者，并研究不同步和 CRT 的分子机制，已经开发出了技术要求高且繁琐的大型动物模型。本研究旨在建立一个首次人类化的体外不同步和 CRT 模型。
将人诱导多能干细胞分化为心肌细胞，并铸造成纤维蛋白基质，以产生工程化心脏组织（EHT）。EHT 要么整体（对称地）进行场刺激，要么从一端（不对称地）局部激发，要么让它们自主跳动。
不对称起搏导致从一端到另一端的去极化波，这在转导了快速遗传 Ca 传感器（GCaMP6f）的人类 EHT 中可见，这表明存在不同步的激发。相比之下，对称起搏导致整个 EHT 中瞬间（同步）的 Ca 信号。为了研究急性和长期的功能影响，将自主跳动的人类 EHT（0.5-0.8 Hz）分为无起搏对照组、对称起搏组和不对称起搏组，每组以 1 Hz 进行刺激。在急性和连续刺激数周后，对称起搏在收缩力方面明显优于不对称起搏或无起搏。在不对称起搏组中，可通过增加后负荷引起的收缩功能障碍更为严重。与起搏犬的报告一致，p38MAPK 和 CaMKII 丰度在不对称起搏下高于对称起搏，而 pAKT 则明显较低。
该模型允许进行长期起搏实验，模拟体外电不同步与同步。结合力测量和后负荷刺激操作，它提供了一个强大的新工具，可以深入了解不同步和 CRT 的生物学。
