PET/CT Technology in Adult Zebrafish: A Pilot Study Toward Live Longitudinal Imaging

Abstract

Decades of research have confirmed the beneficial and advantageous use of zebrafish (Danio rerio) as a model of human disease in biomedical studies. Not only are 71% of human genes shared with the zebrafish many of these genes are linked to human diseases. Currently, numerous transgenic and mutant genetic zebrafish lines are now widely available for use in research. Furthermore, zebrafish are relatively inexpensive to maintain compared to rodents. However, a limiting factor to fully utilising adult zebrafish in research is not the fish but the technological imaging tools available. In order to increase the utilisation of adult zebrafish, which are not naturally transparent, requires new imaging approaches. Therefore, this feasibility study: (1) presents an innovative designed PET/CT adult zebrafish imaging platform, capable of maintaining normal aquatic physiology during scanning; (2) assesses the practical aspects of adult zebrafish imaging; and (3) set basic procedural guidelines for zebrafish imaging during a PET/CT acquisition.Methods: With computer aided design (CAD) software an imaging platform was developed for 3D printing. A 3D printed zebrafish model was created from a CT acquisition of a zebrafish using the CAD software. This model and subsequently euthanised zebrafish were imaged post-injection using different concentrations of the radiotracer [18F]FDG with CT contrast.Results: PET/CT imaging was successful, revealing levels as low as 0.01 MBq could be detected in the fish. In the zebrafish imaging post-injection distribution of the radiotracer was observed away from the injection site as well as tissue uptake. Potential preliminary husbandry and welfare guidelines for the fish during and after PET/CT imaging were determined.Conclusion: Using PET/CT for adult zebrafish imaging as a viable non-invasive technological tool is feasible. Adult zebrafish PET/CT imaging has the potential to be a key imaging technique offering the possibilities of enhanced biomedical understanding and new translational data sets.

Extracellular Vesicles and Intercellular Communication: Challenges for In Vivo Molecular Imaging and Tracking

“…Zebrafish have emerged as a powerful model organism in research because they present many advantages, including high fecundity, rapid external development, and unrivaled cellular level in vivo imaging, and stable transgenic zebrafish lines expressing cell membrane-tethered fluorophores would also label EVs produced by those cells. The high percentage (more than 70%) of orthologous genes in common with Homo sapiens, the easy management, and the low cost with respect to rodents [ 125 ] represent additional advantages associated with the use of this specimen to be considered a versatile pre-mouse model [ 69 ]. Despite that, the use of this animal model involves some difficulties [ 69 ], especially when the use of the adult model and more sophisticated imaging techniques are requested.…”

“…Despite that, the use of this animal model involves some difficulties [ 69 ], especially when the use of the adult model and more sophisticated imaging techniques are requested. The limiting factor is the technological equipment [ 125 ] since tomographic scanners are not suitable for the imaging of fish, although numerous studies are currently underway to overcome this obstacle [ 126 , 127 ].…”

“…Surface or membrane radiolabeling is the most common method of radiolabeling EVs, which can involve direct labeling, the incorporation of the radionuclide by genetic modification, the incorporation into the membrane, and the labeling by a chelator (with a metal-binding moiety for sequestering radiometals) [97]. The most often used radionuclide for surface tagging are isotopes of iodine ( 123 I, 124 I, 125 I, and 131 I) and Tecnetium-99m. 131 I-labeled EVs from endothelial progenitor cells were used to assess the differential in vivo distribution in metastatic breast cancer animal models by SPECT [98].…”

New Enclosure for in vivo Medical Imaging of Zebrafish With Vital Signs Monitoring

“…The non-invasive image provided by PET technology and its ability to detect changes in metabolic, biological, chemical, and molecular processes may provide new scientific discoveries and economic advantages in research with zebrafish ( Bufkin and Leevy, 2015 ; Dorsemans et al, 2017 ). However, only a few studies using PET in zebrafish are reported in the literature ( Bufkin and Leevy, 2015 ; Dorsemans et al, 2017 ; Jones et al, 2017 ; Snay, 2017 ; Tucker et al, 2021 ). In all of those, the equipment used has been particularly rudimentary for physiological preservation and animal welfare.…”

“…In all of those, the equipment used has been particularly rudimentary for physiological preservation and animal welfare. In these in vivo studies, zebrafish were either upright or wrapped in absorbent tissue ( Bufkin and Leevy, 2015 ; Dorsemans et al, 2017 ; Jones et al, 2017 ; Snay, 2017 ; Tucker et al, 2021 ). These conditions are not natural for the fish, adding undesirable physiological stress.…”