Three-Dimensional Imaging Modalities for Craniofacial Analysis in Mouse Embryos

Cleft palate is one of the most common congenital birth defects in humans and current surgical treatment for the craniofacial abnormality is complex and invasive. Defects in multiple genes have been linked to a failure in the process of palate development, some of which also affect tongue size and volume.  

Objective: Although recent studies using various mutant animal models have advanced our knowledge of the regulatory mechanism of palatogenesis, most studies rely on traditional two-dimensional histology to analyze defects in mutant mice. This study aims to characterize wildtype and mutant mice palates and tongues using three-dimensional micro-MRI and CT scans. We will generate a resource of volumetric data for palate and tongue anatomy comparing the of benefits and limitations of each imaging modality.

Method: Imaging modalities were developed and optimized to visualize and analyze palate and tongue anatomy in wildtype and Tgfbr2 mutant mouse embryos (Wnt1-Cre; Tgfbr2(fl/+) Alk5(fl/fl) and Tgfbr2(fl/fl)_Alk5(fl/+)). Three-dimensional magnetic resonance micro-imaging and x-ray computed tomography data were acquired from multiple embryos staged at E18.5 days of gestation. Individual voxel labeling methods were used to detail the anatomy and extract the volume of the palate and tongue for analysis. 

Result: Using micro-MRI and CT scans, we were able to characterize the defects in palatal shelf and tongue of Tgfbr2 mutant in comparison to wildtype mice. These results demonstrate that both scans are powerful tools for analyzing phenotypes in a variety of genetically engineered mice. The higher image resolution and detail of the micro-CT provides excellent platform for anatomical labeling of muscle and bone whereas the micro-MRI has better volumetric consistency with more accurate surface rendering.  

Conclusion: Micro-MRI and CT imaging modalities can be used to facilitate visualization and analyses of three dimensional and volumetric anatomy to characterize differences in craniofacial growth patterns and structures. Supported by the FaceBase Consortium, U01020065, NIDCR, NIH.