HCN4-Overexpressing Mouse Embryonic Stem Cell-Derived Cardiomyocytes Generate a New Rapid Rhythm in Rats with Bradycardia

Abstract

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.

Enhancement of pacing function by HCN4 overexpression in human pluripotent stem cell-derived cardiomyocytes

“…Recently, designer cells with functions added by genetic modification, such as cells used in chimeric antigen receptor (CAR) T-cell therapy, are expected to become new tools for cell-based therapy [9,10]. Previously, we have transduced HCN4 into mouse embryonic stem cell-derived cardiomyocytes (ESC-CMs) to intensify their pacing function in vitro and in vivo [11,12]. HCN4 encodes a hyperpolarization-activated cyclic nucleotidegated potassium channel (HCN channel) producing a pacemaker current.…”

Identification of TTN as a novel candidate gene for atrioventricular block in a Chinese pedigree by whole-exome sequencing

“…As reported previously, many gap junction and ion channel genes such as KCNQ1, KCNE1, KCNH2, KCNE2, KCNJ2, SCN5A, CASQ2, ANK2, GJA5 and HCN4 were known to relate with AVB. 10–16 Besides, the structural protein TTN mutation (TTN p.Glu5365Asp;TTN p.Arg3067His; TTN p.Arg8985Cys) was reported previously to be detected among AVB patients. 6 TTN mutation was reported previously to be the genetic cause of cardiomyopathy, 17,18 one of the potential causes of AVB.…”

Gene Therapy Approaches to Biological Pacemakers

“…HCN4 mutations have been shown to cause sinus node dysfunction [23,24,25]. Overexpressing HCN4 specifically in the heart or delivering cardiomyocytes overexpressing HCN4 exhibited pacemaker activity in small animal models [26,27]. On the other hand, working cardiomyocytes maintain the resting membrane potentials during diastole.…”