Ultrastructural Mapping of the Zebrafish Gastrointestinal System as a Basis for Experimental Drug Studies

Figure 6

Illustration showing the different routes of administration possible in zebrafish larvae to study the uptake, transport, metabolism, and efficacy of therapeutic drug- and/or cell-based approaches. (I) Indirect administration of complexes dissolved in water or administered directly via the oral route, mixed with food pellets. (II-III) Local and targeted microinjection of fluorescent macromolecular complexes at the site of interest or the use of microcapillary needles to deposit genetically modified cells within the digestive glands (II) or intestines (III). Note that those three administering routes are typically employed in routine preclinical screening studies in rodent models and human studies as well underpinning the relevance of the zebrafish model to investigate the pharmacology, toxicology, and effectiveness of new therapeutic interventions. Taking advantage of the optical translucent properties of the larvae, subsequent whole-mount live-cell imaging allows systematic monitoring of the treatment regimes using fluorescent navigation. The results can be combined with correlated electron microscopy techniques as depicted under Figures 1–4. Colour legend for the zebrafish: swim bladder (yellow); stomach and intestines (purple); liver (blue); pancreas (green).