Natalie K Y Wee, Narelle E McGregor, Emma C Walker, Ingrid J Poulton, Michelle Kieu Mi Dang, Jonathan H Gooi, Wayne A Phillips, Natalie A Sims
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引用次数: 0
Abstract
Intracellular phosphoinositide 3-kinase (PI3K) signaling is activated by multiple bone-active receptors. Genetic mutations activating PI3K signaling are associated with clinical syndromes of tissue overgrowth in multiple organs, often including the skeleton. While one formation is increased by removing the PI3K inhibitor (phosphatase and TENsin homolog deleted on chromosome 10 (PTEN)), the effect of direct PI3K activation in the osteoblast lineage has not been reported. We introduced a known gain-of-function mutation in Pik3ca, the gene encoding the p110α catalytic subunit of PI3K, in osteocytes and late osteoblasts using the dentin matrix protein-1 Cre (Dmp1Cre) mouse and assessed the skeletal phenotype. Femur shape was grossly normal, but cortical thickness was significantly greater in both male and female Dmp1Cre.Pik3caH1047R mice, leading to almost doubled bone strength at 12 wk of age. Both sexes had smaller marrow areas from 6 wk of age. Female mice also exhibited greater cross-sectional area, which continued to increase until 24 wk of age, resulting in a further increase in bone strength. Although both male and female mice had increased endocortical mineralizing surface, only female mice had increased periosteal mineralizing surface. The bone formed in the Dmp1Cre.Pik3caH1047R mice showed no increase in intracortical remodeling nor any defect in cortical bone consolidation. In contrast, on both endocortical and periosteal surfaces, there was more lamellar bone formation, including highly organized osteocyte networks extending along the entire surface at a greater thickness than in control mice. In conclusion, direct activation of PI3Kα in cells targeted by Dmp1Cre leads to high cortical bone mass and strength with abundant lamellar cortical bone in female and male mice with no increase in intracortical remodeling. This differs from the effect of PTEN deletion in the same cells, suggesting that activating PI3Kα in osteoblasts and osteocytes may be a more suitable target to promote formation of lamellar bone.
期刊介绍:
The Journal of Bone and Mineral Research (JBMR) publishes highly impactful original manuscripts, reviews, and special articles on basic, translational and clinical investigations relevant to the musculoskeletal system and mineral metabolism. Specifically, the journal is interested in original research on the biology and physiology of skeletal tissues, interdisciplinary research spanning the musculoskeletal and other systems, including but not limited to immunology, hematology, energy metabolism, cancer biology, and neurology, and systems biology topics using large scale “-omics” approaches. The journal welcomes clinical research on the pathophysiology, treatment and prevention of osteoporosis and fractures, as well as sarcopenia, disorders of bone and mineral metabolism, and rare or genetically determined bone diseases.