Magnetic Resonance Microscopy Defines Ethanol‐Induced Brain Abnormalities in Prenatal Mice: Effects of Acute Insult on Gestational Day 8

Abstract

Background Magnetic resonance microscopy (MRM), magnetic resonance imaging (MRI) at microscopic levels, provides unprecedented opportunities to aid in defining the full spectrum of ethanol’s insult to the developing brain. This is the first in a series of reports that, collectively, will provide an MRM-based atlas of developmental stage-dependent structural brain abnormalities in a Fetal Alcohol Spectrum Disorders (FASD) mouse model. The ethanol exposure time and developmental stage examined for this report is gestational day (GD) 8 in mice, when the embryos are at early neurulation stages; stages present in humans early in the fourth week postfertilization. Methods For this study, pregnant C57Bl/6J mice were administered an ethanol dosage of 2.8 g/kg intraperitoneally at 8 days, 0 hour and again at 8 days, 4 hours postfertilization. On GD 17, fetuses that were selected for MRM analyses were immersion fixed in a Bouin’s/Prohance solution. Control fetuses from vehicle-treated dams were stage-matched to those that were ethanol-exposed. The fetal mice were scanned ex vivo at 7.0 T and 512 · 512 · 1024 image arrays were acquired using 3-D spin warp encoding. The resulting 29 lm (isotropic) resolution images were processed using ITK-SNAP, a 3-D segmentation/visualization tool. Linear and volume measurements were determined for selected brain, head, and body regions of each specimen. Comparisons were made between control and treated fetuses, with an emphasis on determining (dis)proportionate changes in specific brain regions. Results As compared with controls, the crown-rump lengths of stage-matched ethanol-exposed GD 17 fetuses were significantly reduced, as were brain and whole body volumes. Volume reductions were notable in every brain region examined, with the exception of the pituitary and septal region, and were accompanied by increased ventricular volumes. Disproportionate regional brain volume reductions were most marked on the right side and were significant for the olfactory bulb, hippocampus, and cerebellum; the latter being the most severely affected. Additionally, the septal region and the pituitary were disproportionately large. Linear measures were consistent with those of volume. Other dysmorphologic features noted in the MR scans were choanal stenosis and optic nerve coloboma. Conclusions This study demonstrates that exposure to ethanol occurring in mice at stages corresponding to the human fourth week postfertilization results in structural brain abnormalities that are readily identifiable at fetal stages of development. In addition to illustrating the utility of MR microscopy for analysis of an FASD mouse model, this work provides new information that confirms and extends human clinical observations. It also provides a framework for comparison of structural brain abnormalities resulting from ethanol exposure at other developmental stages and dosages.

Imaging modalities to assess structural birth defects in mutant mouse models

“…The MRI system detects changes in the magnetic field of hydrogen atoms within the sample, converting this information into 2D or 3D images of the sample. For small animal imaging, MRI systems with high-magnetic field strengths (micro-MRI) with 7 to 14-Tesla magnets are commercially available (Schneider et al, 2004;Yelbuz et al, 2004;Cleary et al, 2009;Pallares et al, 2009;Parnell et al, 2009;French et al, 2010;Yamada et al, 2010;Zouagui et al, 2010). These systems have imaging resolution of 20 lm, similar to micro-CT and better than ultrasound biomicroscopy.…”

Mitogen-activated protein kinase modulates ethanol inhibition of cell adhesion mediated by the L1 neural cell adhesion molecule

“…Both substrains were administered one dose of ethanol (2.9 g/kg) at the beginning of gestational day (GD) 7 and another dose 4 h later. This well-established ethanol exposure paradigm induces ocular defects similar to those observed in children with FAS (43). Examination of GD 14 fetuses from ethanol-exposed dams revealed right ocular defects in 50.9% of 6J mice (n = 55) and 28.2% of 6N mice (n = 71; P = 0.0104, Fisher's exact test) and left ocular defects in 41.8% of 6J mice and 11.3% of 6N mice (P = 0.0001).…”

Radiological studies of fetal alcohol spectrum disorders in humans and animal models: An updated comprehensive review

“…GD8 ethanol exposure [157] caused a 25% reduction in total body volume and 19.5% reduction in brain volume. Overall brain volume reduction was traced back to many sub-regions, such as the cortex, striatum, hippocampus, cerebellum, and pons/medulla, but not to the septal region and the pituitary as was observed with GD7 exposure.…”