Embryonic stem cells form an organized, functional cardiac conduction system in vitro

Area of Science:

• Cardiology
• Stem Cell Biology
• Molecular Biology

Background:

• A functional cardiac pacemaking-conduction system is vital for normal heart function.
• Existing in vitro models for studying this specialized system are not reproducible.
• Identifying functional cardiac pacemaking cells in vitro is challenging due to unknown cellular characteristics.

Purpose of the Study:

• To develop a reproducible in vitro model system for studying the cardiac pacemaking-conduction system.
• To identify and isolate functional cardiac pacemaking cells using molecular markers.
• To characterize the electrophysiological and genetic properties of isolated pacemaking cells.

Main Methods:

• Utilized differentiating murine embryonic stem cells.
• Coexpressed the minK-lacZ transgene and the chicken GATA6 (cGATA6) enhancer to identify cardiac pacemaking-conduction system components.
• Isolated cGATA6/minK copositive cells for functional and molecular analysis.

Main Results:

• Developed an organized in vitro cardiac pacemaking-conduction system.
• Identified pacemaking
• nodes
• (cGATA6-positive cell clusters) functionally coupled with contracting regions.
• Isolated cells exhibited morphology, action potential waveforms, and ionic currents characteristic of specialized cardiac pacemaking myocytes.
• Demonstrated that cGATA6-positive cells spontaneously depolarize and drive contractions in surrounding cells.

Conclusions:

• Generated a novel, reproducible in vitro model for studying the cardiac pacemaking-conduction system.
• Successfully isolated a renewable population of cells with characteristics of cardiac pacemaking myocytes using molecular markers.
• This model system facilitates the study of functional properties and molecular phenotypes of cardiac pacemaking cells.