Generation of a T lymphocyte-specific protease-activated receptor-2 null mouse for investigation of periodontal disease-induced bone loss

Periodontal diseases are characterised by gingival inflammation and alveolar bone loss. A major etiological agent is Porphyromonas gingivalis, which secretes proteases capable of activating protease-activated receptor-2 (PAR2). Our
laboratory has previously demonstrated that when subjected to an established P.gingivalis-induced periodontitis model PAR2 global knockout mice display an impaired immune response and reduced bone loss. Hence, we hypothesised that
PAR2 expressed on T-cells is required for the establishment and progression of periodontal disease. To test this hypothesis, CD4+ T-cells were adoptively transferred from PAR2+/+ or global PAR2-/-mice into αβ T-cell receptor
knockout mice. Following the adoptive transfer, the mice were subjected to an established P.gingivalis-induced periodontitis model. Significant alveolar bone loss was observed in αβ T-cell receptor knockout mice that received Tcells
from PAR2 +/+ mice, but not in αβ T-cell receptor knockout mice that received T-cells from PAR2-/- mice, suggesting that PAR2 expression by T-cells is pivotal in P. gingivalis induced bone loss. In order to further test the role
of PAR2 on T-cells and other cell types we have generated mice harbouring floxed PAR2 alleles. These mice have been bred with lymphocyte protein tyrosine kinase (Lck)-Cre transgenic mice to produce mice in which PAR2 is deleted in Tcells during the DN3 stage of differentiation. The efficiency of PAR2 deletion was determined in T-cells isolated from various lymphoid tissues including spleen, thymus and lymph nodes. We observed a 94% and 40% deletion of the PAR2 gene in the T-cells isolated from thymus and spleen respectively, suggesting a previously unidentified role for PAR2 during β-selection in the early stages of T-cell maturation. The findings of this project will help us better understand the specific role of PAR2 and T-cells in mediating the bone loss associated with periodontitis and help in designing novel therapies with which to treat the disease.