Cranial bone microarchitecture in a mouse model for syndromic craniosynostosis

Crouzon syndrome is a congenital craniofacial disorder caused by mutations in the Fibroblast Growth Factor Receptor 2 (FGFR2). It is characterized by the premature fusion of cranial sutures, leading to a brachycephalic head shape, and midfacial hypoplasia. The aim of this study was to investigate the effect of the FGFR2 mutation on the microarchitecture of cranial bones at different stages of postnatal skull development, using the FGFR2C342Y mouse model. Apart from craniosynostosis, this model shows cranial bone abnormalities. High-resolution synchrotron microtomography images of the frontal and parietal bone were acquired for both FGFR2C342Y/+ (Crouzon, heterozygous mutant) and FGFR2+/+ (control, wild-type) mice at five ages (postnatal days 1, 3, 7, 14 and 21, n = 6 each). Morphometric measurements were determined for cortical bone porosity: osteocyte lacunae and canals. General linear model to assess the effect of age, anatomical location and genotype was carried out for each morphometric measurement. Histological analysis was performed to validate the findings. In both groups (Crouzon and wild-type), statistical difference in bone volume fraction, average canal volume, lacunar number density, lacunar volume density and canal volume density was found at most age points, with the frontal bone generally showing higher porosity and fewer lacunae. Frontal bone showed differences between the Crouzon and wild-type groups in terms of lacunar morphometry (average lacunar volume, lacunar number density and lacunar volume density) with larger, less dense lacunae around the postnatal age of P7-P14. Histological analysis of bone showed marked differences in frontal bone only. These findings provide a better understanding of the pathogenesis of Crouzon syndrome and will contribute to computational models that predict postoperative changes with the aim to improve surgical outcome. Crouzon syndrome, caused by FGFR2 mutations, leads to premature cranial suture fusion and abnormal head shapes. This study used FGFR2C342Y mice to examine the mutation's effect on cranial bone microarchitecture during postnatal development. High-resolution imaging of frontal and parietal bones in mutant and wild-type mice revealed significant differences in bone volume fraction, canal and lacunar morphometry, especially in frontal bones. Mutants had larger, less dense lacunae around postnatal days 7-14. These findings improve understanding of Crouzon syndrome and aid in enhancing surgical outcomes.image