Fig. 2.

Drug discovery using the AA-induced heart failure model. (A) Protocol for drug discovery using the AA model. In phase I, zebrafish embryos were obtained by in vitro fertilization. On the next day, normal 24 hpf embryos were selected and arrayed into a 96-well plate, 5 embryos/well with AA and/or test compounds. At around 55 hpf, the cardiac function and morphology was analyzed with a dissection microscope. Positive compounds were further characterized in phase II to understand their dosage curve, toxicity, and functional time window. (B–E) Scoring for the cardiac phenotypes. A four-category scoring system was established to distinguish the severity of heart failure in the treated embryos. Category I (B): embryos show almost no contraction in the heart. Category II (C): embryos show no contraction in ventricle but weak or slow contraction in the atria. Category III (D): embryos show contraction in both atria and ventricles along with distinguishable morphological defects, including cardiac edema, enlarged hearts, blood pool, and slow circulation. Category IV (E): embryos show normal cardiac morphology and function. Video clips of each category are available in the Supplementary Data. hpf, hours post-fertilization.