DNA damage drives accelerated bone aging via an NF-κB–dependent mechanism

Authors

  • Qian Chen,

    1. Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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  • Kai Liu,

    1. Department of Oral Biology, University of Pittsburgh School of Dental Medicine, Pittsburgh, PA, USA
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  • Andria R Robinson,

    1. Department of Human Genetics, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA
    2. University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
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  • Cheryl L Clauson,

    1. University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
    2. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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  • Harry C Blair,

    1. Pittsburgh Veteran's Affairs Medical Center, Pittsburgh, PA, USA
    2. Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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  • Paul D Robbins,

    1. University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
    2. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
    Current affiliation:
    1. 7 Paul D Robbins and Laura J Niedernhofer, Department of Metabolism and Aging, Scripps Florida, Jupiter, FL 33458, USA.
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  • Laura J Niedernhofer,

    1. University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA
    2. Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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  • Hongjiao Ouyang

    Corresponding author
    1. Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
    2. Department of Restorative Dentistry and Comprehensive Care, University of Pittsburgh School of Dental Medicine, Pittsburgh, PA, USA
    3. Center for Craniofacial Regeneration, University of Pittsburgh School of Dental Medicine, Pittsburgh, PA, USA
    4. McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
    • Department of Restorative Dentistry and Comprehensive Care, University of Pittsburgh School of Dental Medicine, 630 Salk Hall 3550 Terrace Street, Pittsburgh, PA 15261, USA.
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Abstract

Advanced age is one of the most important risk factors for osteoporosis. Accumulation of oxidative DNA damage has been proposed to contribute to age-related deregulation of osteoblastic and osteoclastic cells. Excision repair cross complementary group 1–xeroderma pigmentosum group F (ERCC1-XPF) is an evolutionarily conserved structure-specific endonuclease that is required for multiple DNA repair pathways. Inherited mutations affecting expression of ERCC1-XPF cause a severe progeroid syndrome in humans, including early onset of osteopenia and osteoporosis, or anomalies in skeletal development. Herein, we used progeroid ERCC1-XPF–deficient mice, including Ercc1-null (Ercc1−/−) and hypomorphic (Ercc1−/Δ) mice, to investigate the mechanism by which DNA damage leads to accelerated bone aging. Compared to their wild-type littermates, both Ercc1−/− and Ercc1−/Δ mice display severe, progressive osteoporosis caused by reduced bone formation and enhanced osteoclastogenesis. ERCC1 deficiency leads to atrophy of osteoblastic progenitors in the bone marrow stromal cell (BMSC) population. There is increased cellular senescence of BMSCs and osteoblastic cells, as characterized by reduced proliferation, accumulation of DNA damage, and a senescence-associated secretory phenotype (SASP). This leads to enhanced secretion of inflammatory cytokines known to drive osteoclastogenesis, such as interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and receptor activator of NF-κB ligand (RANKL), and thereby induces an inflammatory bone microenvironment favoring osteoclastogenesis. Furthermore, we found that the transcription factor NF-κB is activated in osteoblastic and osteoclastic cells of the Ercc1 mutant mice. Importantly, we demonstrated that haploinsufficiency of the p65 NF-κB subunit partially rescued the osteoporosis phenotype of Ercc1−/Δ mice. Finally, pharmacological inhibition of the NF-κB signaling via an I-κB kinase (IKK) inhibitor reversed cellular senescence and SASP in Ercc1−/Δ BMSCs. These results demonstrate that DNA damage drives osteoporosis through an NF-κB–dependent mechanism. Therefore, the NF-κB pathway represents a novel therapeutic target to treat aging-related bone disease. © 2013 American Society for Bone and Mineral Research.

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