Micron-scale voltage and [Ca(2+)]i imaging in the intact heart

Area of Science:

• Cardiovascular Physiology
• Cellular Electrophysiology
• Biomedical Imaging

Background:

• Isolated cardiomyocyte studies provide cellular insights into transmembrane voltage (Vm) and intracellular calcium ([Ca(2+)]i) regulation.
• Translating these findings to the complex system of the intact heart, particularly regarding ion channels and Ca(2+) handling proteins, remains challenging.

Purpose of the Study:

• To review laser scanning fluorescence microscopy-based approaches for monitoring dynamic changes in [Ca(2+)]i and Vm in Langendorff-perfused mouse hearts.
• To discuss the application of these techniques in assessing functional syncytium formation by transplanted cells and characterizing Ca(2+) handling phenotypes.
• To highlight the utility of microscopy in resolving subcellular Vm dynamics and voltage gradients in normal and diseased hearts.

Main Methods:

• Development of single- or dual-photon laser scanning fluorescence microscopy techniques.
• Utilizing transgenic reporter technology for [Ca(2+)]i imaging.
• Employing fast-response voltage-sensitive dyes for Vm dynamics.
• Application in immobilized, Langendorff-perfused mouse hearts at sub-cellular to multi-cellular levels.

Main Results:

• Demonstrated ability to assess electrical coupling of transplanted myocytes (donor-derived or stem cell-derived) by entrainment of [Ca(2+)]i transients.
• Characterized Ca(2+) handling phenotypes of cellular implants.
• Resolved subcellular Vm dynamics during cardiac action potentials in Langendorff-perfused mouse hearts.
• Showcased utility in measuring microscopic-scale voltage gradients in normal and diseased hearts.

Conclusions:

• Laser scanning fluorescence microscopy provides powerful tools to bridge the gap between cellular and whole-heart function.
• These techniques are crucial for evaluating the functional integration of cardiac cell therapies.
• The methods offer unprecedented resolution for studying cardiac electrophysiology and disease mechanisms at the subcellular level.