Zebrafish heart regenerates after chemoptogenetic cardiomyocyte depletion

Abstract

Background: Zebrafish can regenerate adult cardiac tissue following injuries from ventricular apex amputation, cryoinjury, and cardiomyocyte genetic ablation. Here, we characterize cardiac regeneration from cardiomyocyte chemoptogenetic ablation caused by localized near-infrared excited photosensitizer-mediated reactive oxygen species (ROS) generation. Results: Exposure of transgenic adult zebrafish, Tg(myl7:fapdl5-cerulean), to di-iodinated derivative of the cell-permeable Malachite Green ester fluorogen (MG-2I) and whole-body illumination with 660 nm light resulted in cytotoxic damage to about 30% of cardiac tissue. After chemoptogenetic cardiomyocyte ablation, heart function was compromised, and macrophage infiltration was detected, but epicardial and endocardial activation response was much muted when compared to ventricular amputation. The spared cardiomyocytes underwent proliferation and restored the heart structure and function in 45-60 days after ablation.Conclusions: This cardiomyocyte ablation system did not appear to activate the epicardium and endocardium as is noted in other cardiac injury models. This approach represents a useful model to study specifically cardiomyocyte injury, proliferation and regeneration in the absence of whole organ activation. Moreover, this system can be adapted to ablate distinct cell populations in any organ system to study their function in regeneration.

Two decades of heart regeneration research: Cardiomyocyte proliferation and beyond

“…Wang et al, 2015). In contrast, a recent report using a selective chemoptogenetic cardiomyocyte ablation strategy in zebrafish resulted in minimal activation of the epicardium and endocardium prior to successful heart regeneration (Missinato et al, 2021). However, epicardial and endocardium marker activation was only evaluated at 3 days post-chemoptogenetic ablation in this study.…”

“…Genetic ablation of the epicardium in transgenic zebrafish using nitroreductase to induce the conversion of the non‐toxic metronidazole to a cytotoxin was also shown to significantly reduce the reparative processes of the heart after apical resection, suggesting that the epicardium has an important role in heart regeneration (J. Wang et al, 2015). In contrast, a recent report using a selective chemoptogenetic cardiomyocyte ablation strategy in zebrafish resulted in minimal activation of the epicardium and endocardium prior to successful heart regeneration (Missinato et al, 2021). However, epicardial and endocardium marker activation was only evaluated at 3 days post‐chemoptogenetic ablation in this study.…”

The multifaceted nature of endogenous cardiac regeneration

“…More recently a similar approach to the NTR system has also been developed which relies on chemoptogenetic abalation of cardiomyocytes ( 15 ). This technique relies on the ability of a fluorogen-activating protein (FAP) to bind fluorgenic dyes such as malachite green-ester fluorogen and subseqeuntly produce cytotoxic reactive oxygen species upon illumination with 660 nm light.…”

Development of a Zebrafish Larvae Model for Diabetic Heart Failure With Reduced Ejection Fraction

“…Therefore, zebrafish larvae are widely used in cardiovascular defect studies. 9) In zebrafish larvae, which have transparent bodies, cells and organs can be directly observed under a microscope. As heart is a continuously beating organ, it is necessary to observe its contraction to accurately evaluate its function.…”