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J Dent Res. 2018 Jul;97(8):946-953. doi: 10.1177/0022034518756889. Epub 2018 Mar 7.

Tristetraprolin Is Required for Alveolar Bone Homeostasis.

Author information

1
1 Department of Oral Health Sciences and Center for Oral Health Research, Medical University of South Carolina, Charleston, SC, USA.
2
2 Department of Oral Biology, University at Buffalo, State University of New York, Buffalo, NY, USA.
3
3 Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC, USA.
4
4 Department of Comparative Medicine, Medical University of South Carolina, Charleston, SC, USA.
5
5 Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, Departments of Biochemistry & Medicine, Duke University Medical Center, Durham, NC, USA.

Abstract

Tristetraprolin (TTP) is an RNA-binding protein that targets numerous immunomodulatory mRNA transcripts for degradation. Many TTP targets are key players in the pathogenesis of periodontal bone loss, including tumor necrosis factor-α. To better understand the extent that host immune factors play during periodontal bone loss, we assessed alveolar bone levels, inflammation and osteoclast activity in periodontal tissues, and immune response in draining cervical lymph nodes in TTP-deficient and wild-type (WT) mice in an aging study. WT and TTP-deficient (knockout [KO]) mice were used for all studies under specific pathogen-free conditions. Data were collected on mice aged 3, 6, and 9 mo. Microcomputed tomography (µCT) was performed on maxillae where 3-dimensional images were generated and bone loss was assessed. Decalcified sections of specimens were scored for inflammation and stained with tartrate-resistant acid phosphate (TRAP) to visualize osteoclasts. Immunophenotyping was performed on single-cell suspensions isolated from primary and peripheral lymphoid tissues using flow cytometry. Results presented indicate that TTP KO mice had significantly more alveolar bone loss over time compared with WT controls. Bone loss was associated with significant increases in inflammatory cell infiltration and an increased percentage of alveolar bone surfaces apposed with TRAP+ cells. Furthermore, it was found that the draining cervical lymph nodes were significantly enlarged in TTP-deficient animals and contained a distinct pathological immune profile compared with WT controls. Finally, the oral microbiome in the TTP KO mice was significantly different with age from WT cohoused mice. The severe bone loss, inflammation, and increased osteoclast activity observed in these mice support the concept that TTP plays a critical role in the maintenance of alveolar bone homeostasis in the presence of oral commensal flora. This study suggests that TTP is required to inhibit excessive inflammatory host responses that contribute to periodontal bone loss, even in the absence of specific periodontal pathogens.

KEYWORDS:

RNA binding proteins; immunology; inflammation; microbiome; osteoclasts; periodontitis

PMID:
29514008
DOI:
10.1177/0022034518756889

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