Longitudinal study of adult zebrafish heart regeneration using high frequency echocardiography

Understanding heart regeneration in a vertebrate model system is a highly relevant public health concern. Coronary heart disease is among the leading causes of disability and mortality worldwide. Injured human hearts caused by myocardial infarction (MI) results in decreased cardiac performance and eventually the development of heart failure. In contrast to mammals, zebrafish fully regenerate myocardium after 20% ventricular resection and provide an excellent model system to study the mechanisms of heart regeneration. It has been shown that high-frequency echocardiography is potentially feasible to obtain in vivo structural, physiological and functional information of zebrafish heart [1]. In this research, heart amputated fish (n=12) were allowed to regenerate for 14 days. Real-time B-mode images and ventricular pulsed-wave Doppler waveforms were acquired daily for 14 days. Measurement on the echocardiographic data was performed to obtain longitudinal cardiac parameters, such as scar volumes, heart rates, and E/A ratios. Experimental results show a consistent decrease of the scar volume from 0.05 +/- 0.012 to 0.015 +/- 0.004 mm(3) along the days post amputation, which suggests the replacement of the blood clot by regenerated myocardium. The E/A ratio display a sudden increase from 0.08 +/- 0.05 to 0.31 +/- 0.15 immediately after the ventricular amputation, followed by a gradual decrease to 0.18 +/- 0.08 at 9dpa. This indicates the continuing recovery of ventricular functions, correlating well with the structural regeneration. Heart rate, however, was not observed significant change along the regenerative process.