Inducible Overexpression of Connexin 43 in Cardiac Myofibroblasts to Mitigate Postinfarct Electrical Vulnerability

Background: Upon myocardial infarction (MI), the incidence of severe ventricular arrhythmias (VT) originating from the border zone (BZ) and/or the scar is strongly increased. This might be due to differences in conduction rates related to altered expression of the gap junction (GJ) protein Cx43 and the onset of re-entry events. Migrating and resident (myo-)fibroblasts (mFB) play a key role in post-MI scar formation, but poorly express Cx43 and cannot compensate the loss of functional GJ. To restore conduction inhomogeneities between BZ, scar area and native myocardium and investigate the consequences on cell viability, lesion size and VT incidence, we generated a transgenic mouse model enabling inducible overexpression of Cx43 in mFB of the scar.

Method: We generated a CRE-inducible mouse line expressing Cx43-P2A and the fluorochrome mCherry (mCh) under the control of the CAG promoter. Crossing the mice (Rosa26(CAG-Cx43-P2A-mCherryloxP)) with a periostin (Postn)-MerCreMer deleter line allows Cx43 overexpression exclusively in activated mFB after left ventricular (LV) cryoinjury and 5 days of tamoxifen treatment. Western blot (WB) analyses and immunostainings were performed to determine Cx43 (over-)expression in the scar and monitor the fate of activated mFB during different stages of scar formation.

Results: Double transgenic mice (Rosa26(Postn-CAG-Cx43-P2A-mCherry)) overexpressed Cx43 in mFB of the LV-scar and BZ following cryoinjury, as demonstrated by immunostainings and WB analyses. mCh expression was restricted to mFB (ASMAC+, Postn+) underscoring the utility of this mouse model. We could also observe expansion of Cx43+/mCh+ mFB starting at 1 week post-MI into the BZ and its spreading into the center of the scar area within 2 weeks. Additionally, we also found that Cx43+/mCh+ mFB migrate and interdigitate with the native myocardium in the BZ and beyond. Preliminary immunostainings (Cx43, mCh, α-actinin/WGA) suggest heterocellular coupling of healthy CM and mCh-labeled transgenic mFBs.

Conclusion: We have established a mouse model enabling to explore the impact of Cx43 overexpression in the BZ and the myocardial scar onto cardiac cell biology, function and post-infarct electrical vulnerability. We hope that our studies will provide novel insight into molecular approaches to treat and reduce post-infarct electrical vulnerability.

Publication History

Article published online:
03 February 2022