In Vivo and Ex Vivo CT Imaging of Zebrafish Gonads.

3D imaging of the gonads in adult zebrafish in vivo is of great interest, as it allows to follow up on their development and/or the egg development in the same individual over time. Optical-based imaging methods can hardly be applied on the adult zebrafish, due to their limited transparency. In this chapter, we will demonstrate the application of micro computer tomography (CT) imaging for in vivo 3D imaging of the gonads in adult zebrafish. We explain how the limited soft-tissue contrast in CT can be overcome and which X-ray dose levels can be expected using this technique. Moreover, we will use high-resolution microCT to perform ex vivo 3D virtual histology of the adult zebrafish, which allows a simple quantitative analysis of the gonad regions, malformation or alterations in the development of the follicles.

miR-486 is modulated by stretch and increases ventricular growth.

Perturbations in biomechanical stimuli during cardiac development contribute to congenital cardiac defects such as hypoplastic left heart syndrome (HLHS). This study sought to identify stretch-responsive pathways involved in cardiac development. miRNA-Seq identified miR-486 as being increased in cardiomyocytes exposed to cyclic stretch in vitro. The right ventricles (RVs) of patients with HLHS experienced increased stretch and had a trend toward higher miR-486 levels. Sheep RVs dilated from excessive pulmonary blood flow had 60% more miR-486 compared with control RVs. The left ventricles of newborn mice treated with miR-486 mimic were 16.9%-24.6% larger and displayed a 2.48-fold increase in cardiomyocyte proliferation. miR-486 treatment decreased FoxO1 and Smad signaling while increasing the protein levels of Stat1. Stat1 associated with Gata-4 and serum response factor (Srf), 2 key cardiac transcription factors with protein levels that increase in response to miR-486. This is the first report to our knowledge of a stretch-responsive miRNA that increases the growth of the ventricle in vivo.