Magnetic resonance microscopy for studying the development of chicken and mouse embryos

Abstract

In this new era of transgenic mouse models, the need to evaluate the effects of gene manipulation during embryonic development is increasing. Traditional embryological studies are invasive, sacrificing embryos before processing in order to reveal specific information like morphology, histology, antigen distribution, gene expression patterns, or physiological parameters. Each objective requires a specific method, excluding the use of one specimen for multiple questions, while for temporal information each method has to be repeated on several specimens during development. The non-invasive character of magnetic resonance microscopy (MRM) allows the study of subsequent stages of normal development in a single embryo in utero over extended periods. In addition, MRM offers the possibility of studying the onset and course of a malformation during development. MRM has proven to be a powerful tool for fixed embryos [1] and living chicken embryos in ovo [2]. Recently, Smith and coworkers [3] managed to visualize and follow living rat embryos in utero in a 2.0T MR microscope by a 3D projection encoding technique with a total scanning time of 27 min The objectives of the present study are to visualize fixed chicken embryos and living mouse embryos in utero. Imaging of the embryo requires very high resolution in combination with excellent contrast. To achieve this, we used moderate to ultra high magnetic fields of 7.0 and 17.6T for the chicken material and 7.0T for the mouse embryos in utero and explored various fast imaging sequences. Fast imaging is necessary to avoid artifacts from embryonic movements that cannot be controlled by the researcher.