The calvaria or skullcap is the vault-like part of the neurocranium that covers the cranial cavity and thereby protects the brain. The calvarial bones are joined by collagenous fibrous sutures consisting of Sharpey’s fibres. This soft-hard (suture-bone) tissue interface not only provides cranial flexibility during birth, but is also the primary site of intramembranous bone growth to accommodate the rapid expansion of neurocranium through embryonic development and early postnatal growth. These sutures transmit biomechanical signals and balance the proliferation of osteogenic cells and their differentiation to form new bone. The aim of the project is to link a structural characterization of the soft-hard tissue interface on multiple length scales to its functionalities, in particular, the extension of calvarial bone fronts during growth.
In contrast to humans, who experience most calvarial fusion within the first two years of life, mice tend to have gradual fusion over their life time. Therefore, mouse calvarial sutures are an outstanding model to investigate how such a fusion process alters the surrounding bone structures and material properties and its biomechanical consequences. In this study starting at a length scale of the whole skull, two groups of mice of different ages (10 and 29 weeks old) were sacrificed and dissected for microCT imaging of their skulls. The image sets were segmented for quantitative analysis, to examine structural differences with respect to the 1D extension of the suture, the 2D arrangement of the bony plates and the overall 3D vault of changing curvature with age. Our analysis showed that these two age groups of mice demonstrate very different extents of calvarial fusion across several anatomical landmarks, in particular, localized changes in bone porosities. Following this outcome, finite element models will be created to further assess the variation in mechanical status between these two age groups.