Assembling And Imaging Long Cables Of Live Cardiomyocytes For Validation Of Cable Theory Relationships

Abstract

Theoretical work on excitable tissue (heart, brain, muscle) often employs concepts from cable theory and resorts to one-dimensional models of wave propagation for capture of essential functional properties. We offer an experimental technique to spatially pack, image and computationally unpack quasi-one dimensional long cables (>10cm) of live excitable cells within the imaging field of view. This is achieved by micropatterning neonatal rat cardiomyocytes into Archimedean spiral topologies and imaging the whole cable at ultra-high resolution. We validate the method's applicability to studies of wave propagation assessing distortions due to curvature effects.Specific demonstrations of the utility of the proposed method include experimental verification of the eikonal relationship linking the velocity of a wave in homogenous cardiac tissue and the radius of curvature seen by the wavefront. This is achieved by patterning thin cables with well defined linearly varying curvature. Furthermore, the technique is applied to validation of theoretical predictions regarding spatially discordant alternans - beat-to-beat alternations in cardiac signals that can be out-of-phase over space. Previous attempts to uncover mechanisms for spatially discordant alternans have utilized purely computational representations and fluorescence imaging of whole-heart preparations and two-dimensional cardiomyocyte monolayer networks. The cable-like geometry (∼10cm) used here facilitate the direct comparison to analytical and numerical derivations done exclusively in 1D.In conclusion, our experimental approach allows for systematic validation of different aspects of cable theory and various excitable tissue phenomena in a well-controlled setting, including wavefront-waveback interactions, implementations of distributed feedback control strategies etc.