The present work aims to fill in the missing histological pieces of the Zebrafish (ZF) Gastro Digestive System (GDS) at high-resolution using correlative and combined x-ray, light and electron microscopy. The ZF has emerged as an experimental model organism due to its high degree of genetic, molecular mechanisms and cell development resemblance to humans1. To-date, the ZF model has been employed to research different diseases such as neural defects, development disorders and cancer. However, the ZF is still not well studied in the fields of gastroenterology & hepatology, to-date, mainly due to the limited literature available on ZF GDS subcellular structure-function properties.
In order to allow combined and correlative imaging across different microscopy platforms, a workflow and a specific sample preparation protocol was designed. A series of combinatorial heavy metal staining agents were used following fixation. Once in Epon resin, the sample is scanned with X-ray micro CT. Next, sagittal and transverse serial semi-thin sections throughout the entire ZF were then cut and collected using array tomography. Sections were stained with compatible histological stains and imaged by LM to identify different tissue types and/or carbon-coated for correlative back-scattered scanning EM. Every 100 mm, an ultra-thin and a semi-thick section were collected for combined high-resolution transmitted EM and tomography.
3D models of the ZF GDS were generated by X-ray micro CT and in combination with LM. In addition, EM data provided 2D/3D information such as total surface area and volume, of sub-cellular structures. In particular, the site of exchange within the different digestive organs (e.g. brush border and hepatocyte sinusoids) and circulatory systems were analysed.
The detailed knowledge gathered assesses the extent to which the ZF can be used, as a gastrointestinal experimental model for future drug delivery studies to cure diseases such as cancer and adverse lipid transport.