Long-Term Reduction of Post-Infarct Ventricular Tachycardia by Transplantation of Connexin 43 Overexpressing Cardiac Fibroblasts

Objectives: Ventricular tachycardias (VT) represent a frequent and potentially lethal complication in myocardial infarction. To improve electrophysiological properties of the myocardial scar, Connexin 43 (Cx43) overexpressing cardiac fibroblasts (cFB) were transplanted in a chronic murine infarction model, and short as well as long-term effects on VT occurrence were investigated.

Methods: Murine cFB were lentivirally transduced in vitro with either a Cx43-IRES-eGFP or IRES-eGFP control construct. Before intramyocardial transplantation cFB were loaded with magnetic nanoparticles and injected (2 × 105 cells) under magnetic attraction into cryolesioned hearts of syngeneic WT mice. In vivo electrophysiological investigation was performed 2 and 8 weeks after myocardial infarction, and ventricular function was evaluated by echocardiography. Grafted cells were identified by their eGFP fluorescence, the Cx43 content of the scar was determined by western blot (WB) analysis and morphological changes were investigated by histology.

Result: In vitro analysis showed a significantly increased Cx43 expression in cFB following lentiviral transduction with Cx43-IRES-eGFP. Postoperatively in short-term experiments electrophysiological testing showed a significantly reduced VT incidence in Cx43-cFb grafted mice compared with controls (40%, n = 15 vs. 89.5%, n = 19). If mice showed VT, further analysis showed no difference in observed VT numbers (Cx43 = 3.7 vs. control = 3.9) and VT duration (Cx43 = 0.5 second vs. control = 0.8 second per animal, when the same stimulation protocols were applied. After 8 weeks a significantly decreased overall VT incidence could still be observed (Cx43 = 33.3%, n = 9 vs. control = 66.7%, n = 12). At this time point also a significant reduction of VT frequency (Cx43 = 1.3 vs. control = 4.6) and VT duration (Cx43 = 0.4 second vs. control = 0.7 second was observed. cFB therapy had no significant influence on cardiac function. Macroscopically transplanted cFB were identified by their eGFP expression at 2 and 8 weeks postoperatively. Histological examination and WB analysis revealed significantly increased Cx43 protein expression as well as significantly reduced aSMA expression in Cx43-cFB transplanted hearts.

Conclusion: Transplantation of Cx43-cFB in cryolesioned hearts reduces post-infarction VT, while cardiac function is unaltered. Besides changes of the electrophysiological properties of the scar by increased Cx43 expression also paracrine effects of engrafted Cx43-cFB seem to be involved.