Saito Yukihiro, Nakamura Kazufumi, Yoshida Masashi, Sugiyama Hiroki, Takano Makoto, Nagase Satoshi, Morita Hiroshi, Kusano Kengo F, Ito Hiroshi
Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences.
Department of Chronic Kidney Disease and Cardiovascular Disease, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences.
Int Heart J. 2018 May 30;59(3):601-606. doi: 10.1536/ihj.17-241. Epub 2018 May 6.
A biological pacemaker is expected to solve the persisting problems of an artificial cardiac pacemaker including short battery life, lead breaks, infection, and electromagnetic interference. We previously reported HCN4 overexpression enhances pacemaking ability of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) in vitro. However, the effect of these cells on bradycardia in vivo has remained unclear. Therefore, we transplanted HCN4-overexpressing mESC-CMs into bradycardia model animals and investigated whether they could function as a biological pacemaker. The rabbit Hcn4 gene was transfected into mouse embryonic stem cells and induced HCN4-overexpressing mESC-CMs. Non-cardiomyocytes were removed under serum/glucose-free and lactate-supplemented conditions. Cardiac balls containing 5 × 10 mESC-CMs were made by using the hanging drop method. One hundred cardiac balls were injected into the left ventricular free wall of complete atrioventricular block (CAVB) model rats. Heart beats were evaluated using an implantable telemetry system 7 to 30 days after cell transplantation. The result showed that ectopic ventricular beats that were faster than the intrinsic escape rhythm were often observed in CAVB model rats transplanted with HCN4-overexpressing mESC-CMs. On the other hand, the rats transplanted with non-overexpressing mESC-CMs showed sporadic single premature ventricular contraction but not sustained ectopic ventricular rhythms. These results indicated that HCN4-overexpressing mESC-CMs produce rapid ectopic ventricular rhythms as a biological pacemaker.
生物起搏器有望解决人工心脏起搏器一直存在的问题，包括电池寿命短、导线断裂、感染和电磁干扰。我们之前报道过，HCN4过表达可增强小鼠胚胎干细胞衍生的心肌细胞（mESC-CMs）在体外的起搏能力。然而，这些细胞在体内对心动过缓的影响仍不清楚。因此，我们将过表达HCN4的mESC-CMs移植到心动过缓模型动物体内，研究它们是否能作为生物起搏器发挥作用。将兔Hcn4基因转染到小鼠胚胎干细胞中，诱导产生过表达HCN4的mESC-CMs。在无血清/葡萄糖和补充乳酸的条件下去除非心肌细胞。采用悬滴法制作含有5×10个mESC-CMs的心肌球。将100个心肌球注射到完全房室传导阻滞（CAVB）模型大鼠的左心室游离壁。在细胞移植后7至30天，使用植入式遥测系统评估心跳。结果显示，在移植了过表达HCN4的mESC-CMs的CAVB模型大鼠中，经常观察到比固有逸搏心律更快的异位心室搏动。另一方面，移植了未过表达mESC-CMs的大鼠出现散在的单发性室性早搏，但没有持续的异位心室节律。这些结果表明，过表达HCN4的mESC-CMs作为生物起搏器可产生快速的异位心室节律。
