Author ORCID Identifier
0009-0001-7011-739X
Defense Date
2026
Document Type
Thesis
Degree Name
Master of Science
Department
Microbiology & Immunology
First Advisor
Huizhi Wang
Abstract
Periodontitis is a polymicrobial infection mediated chronic inflammatory disease characterized by progressive, irreversible destruction of the tooth-supporting tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. Although macrophages exhibit substantial phenotypic and functional plasticity and participate in every stage of periodontitis, the molecular mechanisms that fine-tune macrophage polarization and phagocytic function within the oral microenvironment, and thereby maintenance of periodontal immune homeostasis, remain poorly understood. MG53, also known as TRIM72, is a tripartite motif (TRIM) family E3 ubiquitin ligase predominantly expressed in skeletal and cardiac myocytes. It has been shown to play a well-established role in plasma membrane repair. Recent studies have reported that MG53 may also regulate NF-kB, AKT, and STAT1 signaling and suppress type I interferon and NLRP3 inflammasome activity in non-muscle tissues. However, whether MG53 regulates periodontal immune homeostasis and alveolar bone integrity, and the underlying mechanism involved in these processes, has not previously been investigated.
To identify the role of MG53 in periodontitis, WT and MG53 KO mice were subjected to ligature-induced periodontitis, with or without oral administration of P. gingivalis (ATCC 33277), followed by analysis using micro-CT for six bone morphometric features including distance between CEJ and ABC (CEJ-ABC), bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and trabecular number (Tb.N). Moreover, in vitro assays were performed using BMDMs from WT and KO mice. The cells were polarized into different macrophage subsets including M1, M2a, and M2c, and then stimulated with P. gingivalis or E. coli LPS. Macrophage polarization was further characterized using multiple complementary approaches, NF-kB/AKT/STAT1 signaling activation, expression of cytokines and chemokines, inducibility of MG53 by P. gingivalis, and the phagocytic capability of macrophages were assessed by Western blotting, RT-qPCR and the gentamicin protection assay, respectively. All experiments were repeated at least in three independent biological replicates.
MG53 deficient mice showed dramatically increased alveolar bone loss compared to WT mice under all six micro-CT measurements, and the extent of bone destruction was further aggravated by P. gingivalis infection. In vitro, MG53 KO macrophages were skewed toward M1 polarization, as indicated by increased protein expression of CD38 and CD86, and enhanced phosphorylation of NF-kB p65, AKT and STAT1. mRNA expression of TNF-α and IL-6 was significantly increased in KO macrophages following LPS stimulation (at the 2-hour and 4-hour timepoints, respectively), with MCP-1 and MIP-2 showing consistent KO-biased numerical trends across the time course; CXCL-1 showed comparable expression between genotypes. Protein expression of the M2 marker Arg-1 was reduced in MG53 KO macrophages, and IL-10 mRNA showed a numerically lower trend in KO cells following LPS stimulation, though this difference did not reach statistical significance. Furthermore, P. gingivalis up-regulated MG53 expression in WT macrophages within 30 minutes and peaking at 1 hour. In addition, intracellular P. gingivalis recovery following gentamicin protection was numerically reduced in MG53 KO macrophages in a single, unreplicated preliminary experiment, raising the possibility of enhanced ROS-mediated intracellular bacterial killing associated with their M1-skewed phenotype, though this finding requires confirmation with additional biological replicates.
Together, these findings demonstrate MG53 as a previously uncharacterized regulator of periodontal macrophage homeostasis and alveolar bone integrity. By attenuating pro-inflammatory macrophage polarization, restricting NF-kB and interferon signaling, and modulating phagocytosis, MG53 serves as a pivotal immunomodulatory checkpoint of periodontal inflammation. Importantly, this study uncovered a novel muscle-immune-bone axis underlying periodontal pathology, suggesting a broader role of muscle-derived protein MG53 in macrophage-mediated periodontal immune homeostasis and alveolar bone integrity. These discoveries expand the scope of periodontal immunopathogenesis and pinpoint MG53 as a potential target of host-modulatory therapies to counteract inflammation-induced alveolar bone loss.
Rights
© Binh Do
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
8-6-2026