Abstract 1562: Skeletal Myoblasts Overexpressing Connexin 43 Form Functional Gap Junctions with Adult Cardiomyocytes in vitro and in vivo
Several studies have suggested that engineered skeletal myoblast cardiomyoplasty may have beneficial mechanical effects. However, synchronized electromechanical coupling of skeletal and cardiac myoblasts via gap junctions has not been demonstrated, potentially leading to observed ventricular arrhythmias. In this study, mouse skeletal myoblasts transduced with a retroviral vector expressing the connexin 43 (Cx 43) gene were used to determine whether functional gap junctions form between skeletal muscle cells and cardiomyocytes in tissue culture; and whether this improves conduction in the AV node. Myoblasts expressing the lacZ gene (TRZ cells) were used as a control. Cx 43 mRNA levels in TRZ myotubes decreased significantly by day 7 after differentiation. In contrast, there was no significant change in connexin expression in Cx 43 transduced cells between day 0 and day 7. Cx 43 cells demonstrated dye transfer with the gap junction permeable dye, Lucifer yellow, to cardiomyocytes. In contrast, there was no dye transfer between TRZ cells and cardiomyocytes. Further, we targeted injections of Cx 43-transduced myoblasts to the nude rat AV conduction axis. Injections into the AV node were performed via a sternotomy and produced transient AV block. 2.5 × 106 cells in 25 μl of TRZ or Cx 43 myoblasts cells were injected. Cardiac electrophysiological changes were accessed 14 days after injection and compared to non-injected nude rats (control). The injection of Cx 43 myoblasts preserved AV conduction, whereas TRZ myoblasts with no gap junction expression profoundly altered AV conduction. Our data suggest that constitutive overexpression of Cx 43 in skeletal myoblasts is feasible, resulting in functional gap junctions with adult cardiomyocytes in vitro and preserving conduction thru the AV node. These findings have important implications for cellular transplantation for myocardial repair.