Mechanosensing of osteoclasts in periodontitis.

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Project Summary/Abstract Host immune inflammatory response to periodontal pathogens, especially, Porphyromonas gingivalis (Pg), is engaged in the destruction of tooth-supporting tissues in periodontitis. Among several virulent factors produced by Pg, a unique pathogenic lipid, phosphoglycerol dihydroceramide (PGDHC), promotes RANKL-induced OC- genesis by acting on non-muscle myosin II-A (Myh9), while inhibiting the production of OB-genesis factor, IGF- 1, from OCs. In our preliminary results, wild-type Pg cells and purified PGDHC, but not serine palmitoyl transferase (SPT) KO Pg cells (deficient in PGDHC production), abrogated mechanosensitive Piezo1-mediated downregulation of OC-genesis. The data suggested that PGDHC may represent a unique virulence factor that causes dysregulation of Piezo1-mechanosnsing system in osteoclasts which leads to retarded bone regeneration. Based on these lines of evidence and preliminary results, it is hypothesized that mechanosensitive Piezo1 elicits a cell signal in OCs that induces the production of IGF-1 and suppress OC- genesis, while the PGDHC, by its binding to Myh9, blocks the mechanosensing function of Piezo1 and, hence, diminishing the bone regenerative potential of alveolar bone affected by periodontitis. This hypothesis will be tested by the following two Specific Aims: Aim 1) To elucidate the molecular mechanism underlying PGDHC- mediated inhibition of Piezo1 channel expressed on OCs in vitro. Aim 2) To determine the effect of PGDHC on the Piezo1 expressed by OCs in a mouse model of ligature and Pg-induced periodontitis. Major four training goals for the candidate include: 1) Gain and improve expertise in advanced science methods associated with osteoimmunology and periodontology, 2) Improve skills in management and analyses of complex datasets, 3) Acquire novel image acquisition and analysis techniques to link bacterial virulent factor and Piezo1 expressed on osteoclasts, using Raman spectroscopy, in vivo imaging, micro-CT and biolayer interferometry, and 4) Develop skills required to lead a research program, including grant writing, management of laboratory personnel, project development and execution. Sponsor, Dr. Kawai, and co-sponsor, Dr. Han, who are experienced in the proposed study addressing the periodontal osteoimmunology and immunopathology as well as mentoring of postdoctoral fellows for their career development in the academic research fields, will be committed to support the candidate’s training, along with consultation committees composed of 5 expert researchers in the fields of lipidomics, bone biology, mechanosensory system, microbiology, and Raman spectroscopy, respectively. All required equipment, devices, protocols and materials are available in the laboratories of sponsors and consultants. The candidate is given a desk and laboratory space in Center for Collaborative Research (CCR) which is the largest biomedical research building in South Florida, equipped with a variety of cutting-edge equipment in the core facilities, all of which are available for the candidate’s research project.