Three-dimensional quantification of ethanol-induced pericardial edema in zebrafish: A structural endpoint for cardiotoxicity assessment.

Ethanol-induced pericardial edema is a common morphological manifestation of developmental cardiotoxicity in zebrafish. However, there is currently a lack of methods that can provide objective and reproducible quantitative measurements of pericardial edema severity. Here, we established a non-invasive, three-dimensional (3D) quantitative framework using Spectral Domain Optical Coherence Tomography (SD-OCT) to resolve this limitation. Validation using a lipid-filled scattering phantom yielded measured and theoretical values with a relative error below 1%. No significant difference existed between these two values (P > 0.05). In the in vivo experiments, zebrafish embryos were exposed to 0%, 0.5%, 1.0%, or 2.0% ethanol. At 72 hpf, pericardial edema volume (PEV) was quantified from consecutive OCT cross-sectional images, while lateral-view bright-field images were used for qualitative morphological assessment. Notably, OCT-based three-dimensional volumetric analysis revealed an increase in PEV at 0.5% ethanol. Visual inspection of stereomicroscope images did not reveal obvious morphological changes. Heart rate decreased and malondialdehyde (MDA) levels increased in the ethanol-exposed groups, providing complementary functional and biochemical evidence of ethanol toxicity. These findings support OCT-derived PEV as a complementary quantitative structural endpoint for characterizing ethanol-induced pericardial alterations in zebrafish.