Protease-activated receptor-2 expression by oral epithelial cells is required for bone loss associated with periodontal disease — ASN Events
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Protease-activated receptor-2 expression by oral epithelial cells is required for bone loss associated with periodontal disease (#43)

Nidhish Francis 1 , Charlie Pagel 1 , Babatunde A Ayodele 1 , Walter Birchmier 2 , Neil M O'Brien-Simpson 3 , Robert N Pike 4 , Eleanor J Mackie 1
  1. Department of Veterinary Biosciences, Melbourne Veterinary School, University of Melbourne, Parkville, Victoria, Australia
  2. Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Straße, Berlin, Germany
  3. Melbourne Dental School, University of Melbourne, Parkville, Victoria, Australia
  4. School of Molecular Sciences, La Trobe University, Bundoora, Victoria, Australia

Periodontal disease is characterised by gingival inflammation and alveolar bone loss. A major aetiological agent is Porphyromonas gingivalis, which secretes proteases capable of activating protease-activated receptor-2 (PAR2). We have previously demonstrated that PAR2 expressed on oral epithelial cells is activated by specific proteases released by P. gingivalis, inducing the secretion of IL-6, and that global knockout of PAR2 prevents bone loss and inflammation in a periodontal disease model in mice. We hypothesised that PAR2 expressed on oral epithelial cells is required for the establishment and progression of periodontal disease. To test this hypothesis, keratinocyte-specific PAR2 knockout mice were generated by crossing PAR2 floxed mice with mice carrying a K14-Cre (delta neo) transgene. Deletion (85-90% efficiency) of PAR2 in oral epithelial cells (but not dermal fibroblasts) was confirmed by quantitative PCR and a PAR2 functional assay (intracellular calcium mobilisation). These mice were subjected to a model of periodontitis involving placement of a ligature around a tooth together with P. gingivalis infection (‘Lig+Inf’). The intervention caused a 53% decrease in alveolar BV/TV (assessed by microCT; P<0.01, two-way ANOVA) in wildtype (PAR2+/+:K14-Cre+) mice. However, in littermate keratinocyte-specific PAR2 knockout (PAR2fl/fl:K14-Cre+) mice, Lig+Inf had no effect on alveolar BV/TV. Keratinocyte-specific knockout of PAR2 also prevented the Lig+Inf-induced increase (2.8-fold; P<0.01, two-way ANOVA) in the number of osteoclasts in alveolar bone. Quantitative PCR demonstrated that Lig+Inf-induced up-regulation (2-4-fold; P<0.01, pairwise fixed randomised reallocation test) of the inflammatory markers IL-6, IL-1β, IFN-γ, myeloperoxidase and CD11b in the gingival tissue was prevented by keratinocyte-specific knockout of PAR2. An increase  in serum IL-6 (3-fold; P<0.01, two-way ANOVA) was similarly prevented by keratinocyte-specific knockout of PAR2. These data suggest that PAR2 expressed on oral epithelial cells plays a critical role in regulating periodontitis-induced bone loss, and will help in designing novel therapies with which to treat the disease.