Craniofacial Morphology of Juvenile Mice with Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) type III is a severe genetic disorder of type I collagen (Col1) which results in bone fragility, reduced stature, and impaired craniofacial growth. To investigate the mechanisms by which Col1 mutations alter craniofacial growth, we used the homozygous recessive OI murine (OIM) mouse model, which is known to exhibit human-like adult phenotypes but for which the juvenile phenotype is unknown. Weaning OIM and wild type (WT) littermates were µCT scanned at 21 days. Craniofacial landmarks were collected using 3D Slicer software. Interlandmark distances (ILDs) and centroid sizes were calculated using Past 2.17 software. ILDs were scaled against skull/mandible centroid size to remove the effect of overall body size for shape analyses. Mann-Whitney U-tests were used to compare absolute and relative (scaled) ILDs between genotypes. Craniomandibular centroid sizes and absolute linear distances (skull, rostrum, palate, and mandible lengths) demonstrate that OIM mice are smaller overall compared to WT littermates. When scaled to centroid size, juvenile OIM mice have a decrease in midface height, nasal and mandibular diastema length but increased hemimandible length compared to WT mice. For a given skull length, OIM mice have shorter faces in both the anteroposterior and dorsoventral dimensions. The morphometric changes seen in juvenile OIM mice replicate the midfacial hypoplasia seen in human children with OI. This mouse model can be used to investigate the structural changes underlying the human OI phenotype and potential therapeutic interventions. These results can be used to inform future investigations of Col1 in craniofacial development.