Abstract 3229: Cell Therapies for Arrhythmias: Genetically Engineered Coupling Determines the Effect on Anisotropic Cardiac Conduction
Cell therapies with genetically modified unexcitable cells could be used to improve conduction in an arrhythmogenic substrate. In this study, aligned confluent neonatal rat CMs (Fig. A1⇓) were covered at 75–100% density for 2 days with neonatal rat cardiac fibroblasts (CFs), HEK 293 cells (controls), or HEK 293 cells genetically engineered to overexpress the gap junction proteins connexin-43 (Cx43 HEKs) or connexin-45 (Cx45 HEKs) (Fig. A2– 4⇓). Gap junction expression and function were assessed by immunostaining (Fig. B1–3⇓), immunoblotting (not shown), and fluorescence recovery after photobleaching (Fig. B4⇓) and were correlated with optically mapped and intracellularly recorded action potential conduction. We found that CFs and Cx45 HEKs weakly coupled to CMs, and without significantly depolarizing CM resting potential, slowed CM conduction to 75% of control. Cx43 HEKs slightly depolarized CM resting potential from −71.6±4.9mV to −65.0±3.8mV (Fig. C3⇓), but significantly decreased CM conduction velocity to 22% (Fig. C1⇓) and increased CM action potential duration to 212% (Fig. C2⇓) of the respective controls. Velocity anisotropy ratio and fraction of spontaneously active monolayers (Fig. C4⇓) were not affected by the described loading. In conclusion, by genetically engineering strong coupling in high input resistance cells, we were for the first time able to experimentally separate capacitive from resistive loading effects on CM conduction. Significant conduction slowing with only moderate cardiac resting potential depolarization using Cx43 HEKs reveals pure capacitive loading as a potent modulator of action potential duration and conduction in cardiomyocytes.
This research has received full or partial funding support from the American Heart Association, Mid-Atlantic Affiliate (Maryland, North Carolina, South Carolina, Virginia & Washington, DC).