Single-cell RNA-sequencing for functional analysis of monocytes and macrophages in periodontitis

PROJECT SUMMARY Periodontitis is a common, chronic, inflammatory disease, triggered by subgingival microbial agents, which can lead to tooth loss and contribute to systemic inflammation. Type 2 diabetes (T2DM) is an important systemic modifier of periodontitis, associated with increased severity and progression of periodontal destruction in affected individuals. Of note, there are large disparities in the prevalence of both periodontitis and T2DM, with minority and low socio-economic status individuals, especially Blacks, being disproportionately affected. Although pro-oxidative and pro-inflammatory signaling have been described as mechanisms underlying enhanced periodontal destruction, especially in the presence of T2DM, the specific, upstream events involving innate immunity and immune cell recruitment are still not fully understood. Recent studies at the single-cell level from our group revealed that: 1) there is heterogeneity in resident immune cells in gingival tissue and in circulating monocytes/macrophages in periodontitis and T2DM; 2) there is a systemic pre-programming of circulating monocytes towards a pro-inflammatory state in patients with periodontitis and T2DM; 3) there are race-specific cellular changes in gingival tissue in periodontitis, including a decrease in immune tolerant PD-L1+ monocyte/macrophages in Blacks, associated with reduced anti-inflammatory macrophage phenotype; and 4) the epigenetic regulator JMJD3 can control macrophage polarization and function in periodontitis. These preliminary findings strongly support the feasibility and significance of the three specific aims in the present application. The proposed work is original and innovative as it seeks to shift current thinking in the field. We plan to build upon our previous work and test our overarching hypothesis that periodontitis, on its own and especially when complicated by T2DM, significantly affects the cellular composition, transcriptomic profile, and monocyte/macrophage activation and function locally (gingival tissue) and systemically (circulation), and that race plays an important role in this setting. First, we propose to dissect the single-cell transcriptomic signature and functional network of myeloid-derived cells in periodontitis patients without or with T2DM. Using single-cell RNA-sequencing, we will identify the transcriptional networks associated with immune cells in gingival tissue and blood samples of periodontitis patients versus healthy controls, and the added burden conferred by T2DM. Then, we propose to identify the effects of race on monocyte/macrophage signaling and function in periodontitis patients without or with T2DM. We will explore the biological basis for the observed periodontal health disparities in Blacks, namely differences in immune cellular composition, function, and signaling locally and systemically. Lastly, we aim to identify the role of the epigenetic regulator JMJD3 in modulation of macrophage phenotype and function in periodontitis. Taken together, several notable conceptual and methodological innovations have been introduced in this application to move the field forward. The proposed studies, with a focus on health disparities, will assist in increasing our understanding of the pathogenesis of periodontitis and its link with T2DM.