Zebrafish have come to the forefront as a flexible, relevant animal model to study human disease, including cardiovascular disorders. Zebrafish are optically transparent during early developmental stages, enabling unparalleled imaging modalities to examine cardiovascular structure and function in vivo and ex vivo. At later stages, however, the options for systematic cardiovascular phenotyping are more limited. To visualise the complete vascular tree of adult zebrafish, we have optimised a vascular corrosion casting method. We present several improvements to the technique leading to increased reproducibility and accuracy. We designed a customised support system and used a combination of the commercially available Mercox II methyl methacrylate with the Batson's catalyst for optimal vascular corrosion casting of zebrafish. We also highlight different imaging approaches, with a focus on scanning electron microscopy (SEM) and X‐ray microtomography (micro‐CT) to obtain highly detailed, faithful three‐dimensional reconstructed images of the zebrafish cardiovascular structure. This procedure can be of great value to a wide range of research lines related to cardiovascular biology in small specimens.

Introduction Marfan syndrome (MFS) is the most common type of fibrillinopathy with a high predisposition to develop TAAD. A thorough understanding of the underlying mechanisms is still lacking, indicating a particular need for more flexible in vivo models to address this knowledge gap. Objectives We aimed to generate a relevant zebrafish model to gain insight into the molecular mechanisms relating fibrillin defects to the cardiovascular system. Methods The CRISPR/Cas9 system was used to systematically target the three different fibrillin genes (fbn1, fbn2a and fbn2b) in Tg(kdrl:GFP) reporter zebrafish. Time-lapse fluorescent microscopy was used to evaluate the cardiovascular phenotype. Results zebrafish lacking fbn1 and/or fbn2a do not show any cardiovascular phenotype during early-stage development. On the other hand, approximately 50% of homozygous fbn2b mutant (fbn2b-/-) zebrafish embryo's show a severe phenotype characterized by endocardial detachment, leading to vascular embolism and premature mortality at 7–9 dpf. Interestingly, the remaining fbn2b-/- zebrafish survive until adulthood, but during larval stages already develop a dilation of the bulbus arteriosus. The caudal vein of all fbn2b-/- embryos also develops abnormally as a cavernous structure lacking vessel integrity. This phenotype is resolved in embryos retaining normal blood flow and aggravated upon pharmacological inhibition of blood flow during development. Conclusion These data indicate that fbn2b-/- zebrafish model recapitulates cardiovascular complications, and can be considered as a relevant model to study the mechanisms underlying MFS pathogenesis. Our preliminary data suggest that there is an interplay between fibrillin deficiency and biomechanical signaling in the regulation of cardiovascular development.