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Updated: Jun 7, 2026
Imaging Ca2+ Signals in Small Pulmonary Veins at Physiological Intraluminal Pressures
Published on: March 21, 2025
Diverse cell morphology and intracellular calcium dynamics in pulmonary vein cardiomyocytes
Ming-Chih Yu1, Chun-Feng Huang, Che-Ming Chang
1Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan.
Insights
Pulmonary vein cardiomyocyte morphology influences electrical activity. Spindle-shaped cells exhibit greater calcium transients and sparks, potentially increasing arrhythmia risk.
Area of Science:
- Cardiology
- Cell Biology
- Electrophysiology
Background:
- Pulmonary veins (PVs) harbor cardiomyocytes with complex morphology and high arrhythmogenesis.
- Calcium (Ca2+) regulation and Ca2+ sparks are crucial for cardiomyocyte electrical activity.
Purpose of the Study:
- To investigate the impact of cardiomyocyte cell morphology on PV electrical activity and Ca2+ homeostasis.
- To determine if cell shape influences Ca2+ handling and arrhythmogenesis in PV cardiomyocytes.
Main Methods:
- Confocal microscopy with fluo-3 Ca2+ fluorescence was used.
- Ca2+ sparks and Ca2+ transients were evaluated in isolated rabbit left atrial and PV cardiomyocytes.
- Cardiomyocytes were classified by morphology: rod, rod-spindle, and spindle/bifurcated.
Main Results:
- Spindle/bifurcated cardiomyocytes, prevalent in PVs with pacemaker activity, showed larger Ca2+ transient amplitude and higher frequency, amplitude, and duration of Ca2+ sparks compared to rod/rod-spindle types.
- Cell length correlated positively with Ca2+ transient amplitude and Ca2+ spark duration.
- PV cardiomyocytes with pacemaker activity predominantly exhibited spindle/bifurcated morphology.
Conclusions:
- Cardiomyocyte cell morphology and length significantly influence Ca2+ homeostasis and Ca2+ spark characteristics.
- The enhanced Ca2+ transients and frequent, high-amplitude Ca2+ sparks in spindle/bifurcated PV cardiomyocytes may contribute to their high arrhythmogenic potential.
Abstract:
Pulmonary veins (PVs) contain cardiomyocytes with a complex cellular morphology and high arrhythmogenesis. Ca(2+) regulation and Ca(2+) sparks play a pivotal role in the electrical activity of cardiomyocytes. The purpose of this study was to investigate whether the cell morphology can determine the PV electrical activity and Ca(2+) homeostasis. Through confocal microscopy with fluo-3 Ca(2+) fluorescence, Ca(2+) sparks and Ca(2+) transients were evaluated in isolated single rabbit left atria (LA) and PV cardiomyocytes according to the cell morphology (rod, rod-spindle and spindle/bifurcated). Twenty-two (20%) rod, 49 (43%) rod-spindle and 41 (37%) spindle/bifurcated cardiomyocytes were identified in the LA (n = 29) and PV (n = 83) cardiomyocytes. The PV cardiomyocytes with pacemaker activity had a higher incidence of spindle/bifurcated morphology than LA and PV cardiomyocytes without pacemaker activity. As compared to those in the rod or rod-spindle cardiomyocytes, spindle/bifurcated cardiomyocytes had a larger Ca(2+) transient amplitude and higher frequency of the Ca(2+) sparks with larger amplitude and longer duration. In contrast, rod-spindle and rod cardiomyocytes had similar Ca(2+) transients and Ca(2+) sparks. The cell length correlated well with the amplitude of the Ca(2+) transient and Ca(2+) spark duration with a linear regression. In conclusion, cell morphology and cell length play a potential role in the Ca(2+) homeostasis and Ca(2+) spark. The large Ca(2+) transients and high frequency of Ca(2+) sparks in spindle/bifurcated cardiomyocytes may cause a high arrhythmogenesis in the PV cardiomyocytes with pacemaker activity.
