Abstract 18616: Connexin43 Expression Modulation Affects Myofibroblast-Cardiomyocyte Coupling: Implications for Infarct Borderzone Expansion
Infarct borderzone (BZ) expansion after acute myocardial infarction is accompanied by functional and structural remodeling, ultimately leading to heart failure. We showed that in vitro myofibroblasts (MFBs) can form gap junctions with adjacent cardiomyocytes (CMs) contributing to CM depolarization, impulse propagation slowing and ectopic activity. Connexin43 (Cx43) plays an important role in establishing electrical coupling, but its involvement in the dynamics of heterocellular coupling has never been investigated in live cells, due to the limit of the nanoscale resolution. Scanning Ion Conductance Microscopy (SICM) can be used to overcome this limit. SICM is a non-invasive method capable of resolving the dynamics of live cell-to-cell contact between neonatal rat CMs and MFBs. We collected consecutive topographical images of live coupled areas (~15 μm2) at ~5 min/scan for 1h. Images were analysed by measuring the movement of randomly selected pixels in the contact area using Matlab-based software.
We found that contacts between CMs were stable over 1h (0.039±0.005 μm/min). In contrast, CM-MFB contacts moved at the rate of 0.13±0.03 μm/min, with de novo forming and disrupting micro-contacts characterizing this movement. Interestingly, Cx43 suppression in MFBs seeded with control CMs reduced contact speed (0.027±0.008 μm/min). Contacts between MFBs are also dynamic (0.29±0.1 μm/min) and Cx43 suppression reduced movement speed (0.035±0.007 μm/min). In seeking to understand the possible underlying mechanisms we found that hypoxia-induced membrane internalization of Cx43 significantly reduced CM-MFB movement. Additionally, interference with Cx43 modulation by a peptide (ACT1) targeting Zonula Occludens-1 in MFBs led to decreased movement, but increased lamellipodia activity. In CMs and co-cultures it increased BZ movement at the contact among CMs, suggesting that the propensity of establishing electrical coupling affects the mechanical coupling.
Author Disclosures: M. Miragoli: None. F. Schultz: None. D. Pijnappels: None. J. Jourdan: None. R. Gourdie: None. M.J. Lab: None. J. Gorelik: None.
- © 2014 by American Heart Association, Inc.