Cellular Size, Gap Junctions, and Sodium Channel Properties Govern Developmental Changes in Cardiac Conduction

Area of Science:

• Cardiovascular Physiology
• Computational Biology
• Biophysics

Background:

• Electrical conduction in the heart relies on sodium channels and gap junctions.
• Intercalated discs (IDs) in adult hearts show preferential localization of sodium channels and gap junctions, enabling ephaptic coupling (EpC).
• Neonatal cardiomyocytes have immature IDs with diffuse ion channel distribution, unlike mature adult IDs.

Purpose of the Study:

• To investigate the developmental regulation of cardiac conduction using in silico methods.
• To determine how age-dependent properties like cell size and ion channel distribution affect electrical conduction velocity (CV).

Main Methods:

• Computational simulations of cardiac ventricular tissue.
• Modeling age-dependent changes in sodium channel and gap junction properties.
• Analysis of conduction velocity based on simulated cellular parameters.

Main Results:

• Conduction velocity (CV) exhibits a biphasic dependence on cell size, modulated by gap junction coupling strength.
• Sodium channel conductance predicts CV in highly coupled tissue but not in weakly coupled tissue.
• Ephaptic coupling effects are most pronounced in larger cells with low gap junction coupling, typical of intermediate developmental stages.

Conclusions:

• Developmental changes in cellular properties significantly influence cardiac conduction.
• Variability in cellular properties across developmental stages leads to a wider range of CV in intermediate stages compared to neonatal and adult stages.
• Simulations highlight the critical role of age-related changes in ion channel distribution and cell size in regulating cardiac electrical activity.