High-frequency ultrasound deformation imaging for adult zebrafish during heart regeneration

Background: The adult human heart cannot efficiently generate new cardiac muscle cells in response to injury, and, therefore, cardiac injury results in irreversible damage to cardiac functions. The zebrafish (Danio rerio) is a crucial animal model in cardiac research because of its remarkable capacity for tissue regeneration. An adult zebrafish can completely regenerate cardiac tissue without a scar being formed, even after 20% of its ventricular myocardium has been resected. Zebrafish have been utilized in developmental biology and genetics research; however, the details of myocardium motions during their cardiac cycle in different regeneration phases are still not fully understood. Methods: In this study, we used a 70-MHz high-resolution ultrasound deformation imaging system to observe the functional recovery of zebrafish hearts after amputation of the ventricular apex. Results: The myocardial deformation and cardiac output (CO) were measured in different regeneration phases relative to the day of amputation. In response to the damage to the heart, the peak systolic strain (epsilon(max)) and strain during ejection time (epsilon(ej)) were lower than normal at 3 days after the myocardium amputation. The CO had normalized to the baseline values at 7 days after surgery. Conclusions: Our results confirm that the imaging system constructed for this study is suitable for examining zebrafish cardiac functions during heart regeneration.