期刊
JOURNAL OF BONE AND MINERAL RESEARCH
卷 32, 期 3, 页码 560-574出版社
WILEY
DOI: 10.1002/jbmr.3014
关键词
AGING; SEX STEROIDS; OSTEOBLASTS; OSTEOCLASTS; MOLECULAR PATHWAYS-REMODELING
资金
- National Institutes of Health [P01 AG13918, R01 AR56679]
- Biomedical Laboratory Research and Development Service of the Veteran's Administration Office of Research and Development [I01 BX001405]
- University of Arkansas for Medical Sciences Tobacco Funds and Translational Research Institute [1UL1RR029884]
- Intramural Research Program of the National Institute on Aging of the National Institutes of Health
Old age and sex steroid deficiency are the two most critical factors for the development of osteoporosis. It remains unknown, however, whether the molecular culprits of the two conditions are similar or distinct. We show herein that at 19.5 months of age -a time by which the age-dependent decline of cortical and cancellous bone mass and cortical porosity were fully manifested in C57BL/ 6J mice-these animals remained functionally estrogen sufficient. Transgenic mice with conditional expression of mitochondria-targeted catalase-a potent H2O2 inactivating enzyme-in cells of the myeloid lineage (mitoCAT; LysM-Cre mice) were protected from the loss of cortical, but not cancellous, bone caused by gonadectomy in either sex. Consistent with these findings, in vitro studies with ERa-deficient Prx1_ cells and gonadectomized young adult mice showed that in both sexes decreased ER alpha signaling in Prx1_ cells leads to an increase in SDF1, a. k. a. CXCL12, an osteoclastogenic cytokine whose effects were abrogated in macrophages from mitoCAT; LysM-Cre mice. In contrast to sex steroid deficiency, the adverse effects of aging on either cortical or cancellous bone were unaffected in mitoCAT; LysM-Cre mice. On the other hand, attenuation of H2O2 generation in cells of the mesenchymal lineage targeted by Prx1-Cre partially prevented the loss of cortical bone caused by old age. Our results suggest the effects of sex steroid deficiency and aging on the murine skeleton are independent and result from distinct mechanisms. In the former, the prevailing mechanism of the cortical bone loss in both sexes is increased osteoclastogenesis caused by estrogen deficiency; this is likely driven, at least in part, by mesenchymal/ stromal cell-derived SDF1. Decreased osteoblastogenesis, owing in part to increased H2O2, combined with increased osteoclastogenesis caused by aging mechanisms independent of estrogen deficiency, are the prevailing mechanisms of the loss of cortical bone with old age. (C) 2016 American Society for Bone and Mineral Research.
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