Rictor/mTORC2 loss in osteoblasts impairs bone mass and strength
| Autor: | Bei Tao, Hong-yan Zhao, Dong-mei Liu, Pei-lin Jiao, Lin Zhao, Dian-dian Zhao, Ting-ting Liu, Li-hao Sun, Jian-min Liu, Mei-Shu Shih |
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| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
medicine.medical_specialty Histology Physiology Endocrinology Diabetes and Metabolism 030209 endocrinology & metabolism mTORC1 Mechanistic Target of Rapamycin Complex 2 mTORC2 Bone resorption Bone and Bones Bone remodeling Adenoviridae 03 medical and health sciences 0302 clinical medicine Internal medicine medicine Cortical Bone Animals Femur Bone Resorption PI3K/AKT/mTOR pathway Cells Cultured Bone mineral Osteoblasts Integrases Chemistry Osteoblast Cell Differentiation Organ Size X-Ray Microtomography Biomechanical Phenomena Mice Inbred C57BL 030104 developmental biology medicine.anatomical_structure Endocrinology Rapamycin-Insensitive Companion of mTOR Protein Cancellous Bone Cortical bone Gene Deletion Signal Transduction |
| Zdroj: | Bone. 90 |
| ISSN: | 1873-2763 |
| Popis: | Mammalian target of rapamycin (mTOR) is a Ser/Thr kinase conserved through evolution that coordinates extra cellular signals associated with cell growth. Main functions of mTOR present in the form of two complexes, namely mTORC1 and mTORC2, which are distinct in their unique components, raptor and rictor. In the current study, using a Cre/loxp system, we found an anabolic effect of mTORC2 signaling on skeleton. Osteoblast differentiation was reduced, with down-regulation of mTORC2 signaling activity in primary cultures of osteoblasts that did not contain rictor. Mice with a specific deletion of rictor in mature osteoblasts showed a significant reduction in lean mass and bone mineral density by dual energy x-ray absorptiometry analysis. Micro-computed tomography, histomorphometric, and molecular biological analyses revealed a marked impairment of the cortical bone mass and microarchitecture, as well as minor changes in trabecular bone, of the Rictorob(-/-) mice. Cortical bone mass and thickness of the femoral mid-shaft were dramatically reduced, with unusual increases in porosity and marrow area in Rictorob(-/-) mice. Thinner trabeculae were found in the L4 vertebrae with relatively normal structural indices of trabecular numbers and separation. A lower rate of bone turnover was observed, as the consequence of the decreased individual osteoblast activity and bone resorption. Furthermore, these changes were associated with significantly decreased bone biomechanical properties. In conclusion, expression of rictor in osteoblasts is essential for the maintenance of normal bone remodeling and microarchitecture, especially for the maintenance of the cortical bone. |
| Databáze: | OpenAIRE |
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