Abstract
Cardiomyocytes (CMs) and fibroblast cells are two essential elements for cardiac tissue structure and function. The interactions between them can alter cardiac electrophysiology and thus contribute to cardiac diseases, such as arrhythmogenesis. One possible explanation is that fibroblasts can directly affect cardiac electrophysiology through electrical coupling with CMs. Therefore, detecting the electrical activities in the CM-fibroblast network is vital for understanding the coupling dynamics among them. Current commercialized platforms for studying cardiac electrophysiology utilize planar microelectrode arrays (MEAs) to record the extracellular field potential (FP) in real-time, but the prearranged electrode configuration highly limits the measurement capabilities at specific locations. Here, we report a custom-designed MEA device with a novel micropatterning method to construct a controlled network of neonatal rat CMs (rCMs) and fibroblast connections for monitoring the electrical activity of rCM-fibroblast co-cultures in a spatially controlled fashion. For the micropatterning of the co-culture, surface topographical features and mobile blockers were used to control the initial attachment locations of a mixture of rCMs and fibroblasts, to form separate beating rCM-fibroblast clusters while leaving empty space for fibroblast growth to connect these clusters. Once the blockers are removed, the proliferating fibroblasts connect and couple the separate beating clusters. Using this method, electrical activity of both rCMs and human-induced-pluripotent-stem-cell-derived cardiomyocytes (iCMs) was examined. The coupling dynamics were studied through the extracellular FP and impedance profile recorded from the MEA device, indicating that the fibroblast bridge provided an RC-type coupling of physically separate rCM-containing clusters and enabled synchronization of these clusters.
Highlights
While cardiomyocytes (CMs) are known as the vital cell type for heart contraction, two-thirds of heart cells are non-cardiomyocytes, among which cardiac fibroblasts constitute the largest fraction
We present a micropatterning method on a custom-designed microelectrode arrays (MEAs) device that allows the long-term monitoring of the electrical activity of a CM-fibroblast network in a spatially controlled fashion
Electrodes located at clusters can be used to detect the field potential (FP) from contracting rat CMs (rCMs), while the electrodes located at the bridges can be used to obtain propagation signals (Figure 1C)
Summary
While cardiomyocytes (CMs) are known as the vital cell type for heart contraction, two-thirds of heart cells are non-cardiomyocytes, among which cardiac fibroblasts constitute the largest fraction. The interaction between the CMs and fibroblasts can alter cardiac electrophysiology and contribute to arrhythmogenesis. There is increasingly more research indicating that fibroblasts can directly affect the cardiac electrophysiology through electrical coupling with CMs [2]. Such electrical coupling between CMs and fibroblasts is achieved via action potential propagation, which is caused by ion fluxes through their heterocellular gap junctions [3]. One technology capable of detecting the electrical activity in the CM-fibroblast network is the microelectrode array (MEA) platform. Conventional electrophysiological monitoring methods, including patch-clamp, brightfield video-based and fluorescent dye-based assessment, are invasive and require further investigation in the relationship between contraction and electrical activity [4,5,6]
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