Deletion of absent in melanoma (AIM) 2 gene alters bone morphology

Absent in Melanoma (AIM) 2 is a gene that is induced by interferon and acts as a cytosolic sensor for double-stranded (ds) DNA. It forms the AIM2 inflammasome, leading to the production of interleukin (IL)-1β and IL-18. Our previous research demonstrated that mice lacking AIM2 exhibit spontaneous obesity, insulin resistance, and inflammation in adipose tissue. In this study, we aimed to explore the impact of AIM2 gene deletion on bone structure in adult and aged mice. Utilizing micro-computed tomography (micro-CT), we discovered that female mice lacking AIM2 showed an increase in the total cross-sectional area at 5 months of age, accompanied by an increase in cortical thickness in the mid-diaphysis of the femur at both 5 and 15 months of age. At 15 months of age, the cortical bone mineral density (BMD) significantly decreased in AIM2 null females compared to wild-type (WT) mice. In AIM2 null mice, both trabecular bone volume and BMD at the distal metaphysis of the femur significantly decreased at 5 and 15 months of age. Similarly, micro-CT analysis of the L4 vertebra revealed significant decreases in trabecular bone volume and BMD in aged AIM2 null females compared to WT mice. Histological examination of femurs from aged mice demonstrated increased bone marrow adiposity in AIM2 null mice, accompanied by a significant increase in CD45-/CD31-/Sca1+/Pdgfa+ adipose progenitor cells, and a decrease in the ratio of CD31-/CD31+ osteogenic progenitor cells, as determined by flow cytometry of bone marrow cells. Our findings suggest that AIM2 deficiency affects bone health by promoting adipogenesis in bone marrow cells and inducing a pro-inflammatory environment, potentially contributing to the decreased bone mineral density.