Role of a novel G protein-coupled mast cell receptor-mediated pathways in periodontal disease

Summary: Periodontitis is a chronic inflammatory disease in which a highly orchestrated host-microbial interaction leads to the destruction of the tooth-supporting structures including periodontal tissue attachment and alveolar bone. Mast cells are found in the gingiva; their numbers are increased in chronic periodontitis and the degree of their

activation correlates well with disease severity. Not surprisingly, it has recently been shown that mast cells contribute to Porphyromonas gingivalis-induced periodontitis in mice, but the mechanisms involved in their activation and regulation remain unknown. Mas-related G protein-coupled receptor X2 (MRGPRX2, mouse

counterpart MrgprB2) is a newly described cell surface receptor that is expressed in a subtype of mast cells found predominantly in the skin and the gingiva. We recently demonstrated that MRGPRX2-expressing mast cells are present in normal gingiva and that their numbers are increased in patients with chronic periodontitis.

In addition, our unpublished preliminary data demonstrated that compared to wild-type mice, MrgprB2-/- mice are protected from mast cell recruitment, gingival inflammation, and bone loss in a ligature-induced model of periodontitis. Based on these findings, we hypothesize that recruitment and activation of mast cells

through MRGPRX2/B2 contribute to periodontitis. In aim 1, we will develop two models of humanized mice. The first involves retroviral transduction of MRGPRX2 into MrgprB2-/- mouse bone marrow stem cells, their differentiation into bone marrow-derived MCs (BMMCs) ex vivo and their engraftment into mast cell-deficient

Wsh/Wsh mice. The second involves CRISPR/Cas9-mediated replacement of MrgprB2 with MRGPRX2. These humanized mice will be used to study Porphyromonas gingivalis and ligature-induced periodontitis. In aim 2, we will modulate periodontitis by targeting MRGPRX2/MrgprB2-mediated cofilin and NF-κB signaling in mast

cells. Successful completion of this study will lead to the development of new preclinical models to modulate periodontitis through specific small molecule receptor antagonists and by targeting signaling in mast cells.