Transplantation of Cx43 Expressing Fibroblasts: An Option for Postinfarct Arrhythmia Prevention?

Objectives: Myocardial infarction can result in a reduced ejection fraction (EF) and post-infarct ventricular tachycardia (VT). Since lost cardiomyocytes are substituted by fibroblasts during scar formation. The content of Connexin 43 (Cx43) and also gap junctions is massively reduced within the infarct area. This fact critically impairs the electrical conduction throughout the lesion and VT can originate by re-entry mechanisms. By magnet-assisted intramyocardial transplantation of magnetic nanoparticle (MNP) loaded Cx43 (over-) expressing cardiac fibroblasts we aimed to reduce post-infarct VT and stabilize the myocardial wall mechanically.

Methods: Murine embryonic cardiac fibroblasts (eCF) were isolated from E13.5 hearts, cultured for 7 days, and then transduced with lentiviral constructs encoding for Cx43-IRES-eGFP or eGFP only. One day prior to intramyocardial transplantation, eCF were loaded with fluorescently labelled MNP. Thereafter, 200,000 cells were injected into cryolesioned hearts of adult female CD1 wildtype mice with or without application of a magnetic field during and 10 minutes after injection. Heart function was analyzed 14 days post infarction by echocardiography and electrophysiological testing. Cell engraftment and Cx43 expression was examined via western blotting and immunohistochemistry.

Results: The used MNP, tagged with a TAMRA fluorochrome, showed a low cell toxicity and high magnetic cell retention rates in vitro. Overnight incubation with lentivirus resulted in a transduction efficacy of ca. 30% for the two used lentiviral constructs and significantly increased protein expression of eGFP and Cx43 was shown by western blotting. Two weeks post transplantation, engrafted eGFP positive eCF were found in a majority of hearts. Functional analysis resulted in significantly increased anterior wall thickening but not significantly increased global left ventricular function when MNP loaded, Cx43 transduced eCF were transplanted with application of a magnetic field. Electrophysiological testing revealed reduced VT incidence after transplantation of Cx43 expressing eCF (+magnet: VT incidence 25%, n = 8 (p < 0.05); −magnet: VT incidence 50%, n = 10) compared to control animals (injection of eGFP expressing eCF, +magnet, VT incidence 78%, n = 9).

Conclusions: Cellular cardiomyoplasty using Cx43 expressing cardiac fibroblasts results in significant reduction of postinfarct arrhythmias but cannot augment cardiac pump function substantially.