ASC Deficiency Compromises Skeletal Architecture and Mechanical Competence in Mice

Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is a key adaptor of canonical inflammasome signaling and has been implicated in osteoblast differentiation and bone formation. However, whether ASC deficiency alters the structural and mechanical properties of the intact skeleton remains unclear. In this study, the skeletal phenotype of 9-week-old male Asc-homozygous-deficient (Asc^-/-) mice was characterized using micro-computed tomography, three-point bending, tibial microindentation, and silver staining of the osteocyte lacunar-canalicular system (LCS). Trabecular microarchitecture, cortical geometry, whole-bone mechanical behavior, tissue-level hardness, and LCS morphology were quantified. Associations between cortical geometric parameters and whole-bone mechanical outcomes were assessed by Pearson correlation analysis. Asc^-/- mice had shorter femora despite greater body weight. Trabecular bone volume fraction, thickness, and number were reduced, whereas trabecular separation was increased. Cortical analysis showed reductions in total cross-sectional area, cortical area, cortical thickness, periosteal perimeter, minimum principal moment of inertia, and polar moment of inertia. Femoral maximum load, stiffness, yield force, and work to fracture were reduced, together with lower tibial cortical hardness. ASC deficiency was also associated with enlarged osteocyte lacunae, reduced canalicular length and density, and increased canalicular width. Cortical area, thickness, and moment of inertia showed strong positive associations with whole-bone mechanical outcomes. Overall, ASC deficiency is associated with a distinct skeletal phenotype characterized by impaired trabecular architecture, reduced cortical size and load-bearing geometry, decreased whole-bone mechanical competence, lower tissue-level hardness, and altered osteocyte LCS organization. These findings extend the known skeletal role of ASC beyond osteogenesis and bone repair to the structural and mechanical phenotype of the intact skeleton.