High-resolution tissue Doppler imaging of the zebrafish heart during its regeneration.

The human heart cannot regenerate after injury, whereas the adult zebrafish can fully regenerate its heart even after 20% of the ventricle is amputated. Many studies have begun to reveal the cellular and molecular mechanisms underlying this regenerative process, which have exciting implications for human cardiac diseases. However, the dynamic functions of the zebrafish heart during regeneration are not yet understood. This study established a high-resolution echocardiography for tissue Doppler imaging (TDI) of the zebrafish heart to explore the cardiac functions during different regeneration phases. Experiments were performed on AB-line adult zebrafish (n=40) in which 15% of the ventricle was surgically removed. An 80-MHz ultrasound TDI based on color M-mode imaging technology was employed. The cardiac flow velocities and patterns from both the ventricular chamber and myocardium were measured at different regeneration phases relative to the day of amputation. The peak velocities of early diastolic inflow, early diastolic myocardial motion, late diastolic myocardial motion, early diastolic deceleration slope, and heart rate were increased at 3 days after the myocardium amputation, but these parameters gradually returned to close to their baseline values for the normal heart at 7 days after amputation. The peak velocities of late diastolic inflow, ventricular systolic outflow, and systolic myocardial motion did not significantly differ during the heart regeneration.