Gingival Transcriptome of Innate Antimicrobial Factors and the Oral Microbiome With Aging and Periodontitis

Use of Nonhuman Primates in Periodontal Disease Research: Contribution of the Caribbean Primate Research Center and Cayo Santiago Rhesus Colony

This review article provides a historical summary regarding the use, value, and validity of the nonhuman primate model of periodontal disease. The information provided cites results regarding the features of naturally occurring periodontitis in various nonhuman primate species, as well as the implementation of a model of experimental periodontitis. Clinical similarities to human disease are discussed, as well as the use of these models to document physiological and pathophysiological tissue changes in the periodontium related to the initiation and progression of the disease. Additionally, the use of these analytics in examination of the tissue characteristics of the disease, and the utility of nonhuman primates in testing and describing various therapeutic modalities are described. As periodontitis represents a disease of an oral microbiome dysbiosis, features of the altered microbiome in the disease in nonhuman primates are related to similar findings in the human condition. The review then provides a summary of the features of local and systemic host responses to a periodontal infection in an array of nonhuman primate species. This includes attributes of innate immunity, acute and chronic inflammation, and adaptive immune responses. Finally, extensive information is presented regarding the role of Macaca mulatta derived from the Cayo Santiago community in evaluating critical biologic details of disease initiation, progression, and resolution. This unique resource afforded the capacity to relate risk and expression of disease and traits of the responses to age, sex, and matriline derivation (e.g., heritability) of the animals. The Cayo Santiago colony continues to provide a critical preclinical model for assessment of molecular aspects of the disease process that can lead to both new targets for therapeutics and consideration of vaccine approaches to preventing and/or treating this global disease.

Transcriptomic features of programmed and inflammatory cell death in gingival tissues

The local gingival tissue environment with homeostasis and tissue-destructive events of periodontitis demonstrates major changes in histological features and biology of the oral/sulcular epithelium, fibroblasts, vascular cells, inflammatory cell infiltration, and alveolar bone.

OBJECTIVE

This study used an experimental periodontitis model to detail the gingival transcriptome related to cell death processes of pyroptosis, necroptosis, ferroptosis, and cuproptosis.

MATERIALS AND METHODS

Healthy Macaca mulatta primates stratified by age, ≤3 years (young), 7-12 years (adolescent), 12-15 years (adult), and 17-23 years (aged), provided gingival tissue biopsies for microarray analysis focused on 257 genes representative of the four cell death processes and bacterial plaque samples for 16S rRNA gene analysis.

RESULTS

Age differences in the profiles of gene expression in healthy tissues were noted for cuproptosis, ferroptosis, necroptosis, and pyroptosis. Major differences were then observed with disease initiation, progression, and resolution also related to the age of the animals. Distinct bacterial families/consortia of species were significantly related to the gene expression differences for the cell death pathways.

CONCLUSIONS

These results emphasized age-associated differences in the gingival tissue molecular response to changes in the quality and quantity of bacteria accumulating with the disease process reflected in regulated cell death pathways that are both physiological and pathophysiological.

Protein Network Alterations in G-CSF Treated Severe Congenital Neutropenia Patients and Beneficial Effects of Oral Health Intervention

PURPOSE

Severe congenital neutropenia (SCN) is a raredisorder characterized by diminished neutrophil levels. Despite granulocytecolony-stimulating factor (G-CSF) treatment, SCN patients remain still prone tosevere infections, including periodontal disease-a significant oral healthrisk. This study investigates the host proteome and metaproteome in saliva andgingival crevicular fluid (GCF) of G-CSF-treated patients.

EXPERIMENTAL DESIGN

We used label-free quantitative proteomics on saliva and GCF samples from SCN patients before (n = 10, mean age: 10.7 ± 6.6 years) and after a 6-month oral hygiene intervention (n = 9,mean age: 11.6 ± 5.27 years), and from 12 healthy controls.

RESULTS

We quantified 894 proteins in saliva (648 human,246 bacterial) and 756 proteins in GCF (493 human, 263 bacterial). Predominant bacterial genera included Streptococcus, Veillonella, Selenomonas, Corynebacterium, Porphyromonas, and Prevotella. SCN patients showed reduced antimicrobial peptides (AMPs) and elevated complement proteins compared tohealthy controls. Oral hygiene intervention improved oral epithelial conditionsand reduced both AMPs and complement proteins.

CONCLUSIONS AND CLINICAL RELEVANCE

SCN patients have aunique proteomic profile with reduced AMPs and increased complement proteins, contributing to infection susceptibility. Oral hygiene intervention not onlyimproved oral health in SCN patients but also offers potential overall therapeuticbenefits.

Impact of Fixed Partial Dentures on Oral Microbial Flora and Gingival Health: An In Vitro Assessment of Salivary Microbial Profiles

Introduction The oral cavity hosts diverse microorganisms affected by factors like pH, temperature, and oxygen levels, influencing disease potential. Dentists manage oral diseases and improve aesthetics using durable restorations. Understanding periodontal response to crowns and fixed partial dentures (FPDs) is essential for effective treatment. This study aims to assess the impact of FPDs on periodontal health by comparing microbial colonies in individuals with and without FPDs. The hypothesis is that there will be no difference in microbial flora and gingival health between the two groups. Materials and methods This in vitro study utilized 40 salivary samples divided into two groups: 20 from patients with FPDs/crowns (Group 1) and 20 from patients without (Group 2). Unstimulated saliva was collected, diluted, and cultured on nutrient agar and Sabouraud Dextrose Agar to quantify anaerobic bacteria and Candida colonies. Colony counts were scored from 0 to IV based on colony-forming unit (CFU), and microscopic examination identified the types of microbes present. Data were analyzed using an unpaired t-test with IBM SPSS Statistics for Windows, Version 26 (Released 2019; IBM Corp., Armonk, New York, United States), with significance set at p < 0.05. Results The independent t-test analysis showed significantly higher mean CFUs of anaerobic microbes in Group 1 (experimental) compared to Group 2 (control) (p = 0.000). However, mean CFUs of Candida did not significantly differ between groups (p = 0.194). Microscopic examination identified Enterococcus faecalis, Pseudomonas aeruginosa, Candida albicans, Staphylococcus aureus, and Streptococcus mutans in the experimental group, whereas the control group contained only Staphylococcus aureus and Streptococcus mutans. Conclusion Individuals with FPDs exhibit higher concentrations of anaerobic microbes and specific bacteria, suggesting an increased risk of gingival inflammation and emphasizing the importance of maintaining good oral hygiene.

Transcriptional Signatures and Network-Based Approaches Identified Master Regulators Transcription Factors Involved in Experimental Periodontitis Pathogenesis

Periodontitis is a chronic inflammatory disease characterized by the progressive and irreversible destruction of the periodontium. Its aetiopathogenesis lies in the constant challenge of the dysbiotic biofilm, which triggers a deregulated immune response responsible for the disease phenotype. Although the molecular mechanisms underlying periodontitis have been extensively studied, the regulatory mechanisms at the transcriptional level remain unclear. To generate transcriptomic data, we performed RNA shotgun sequencing of the oral mucosa of periodontitis-affected mice. Since genes are not expressed in isolation during pathological processes, we disclose here the complete repertoire of differentially expressed genes (DEG) and co-expressed modules to build Gene Regulatory Networks (GRNs) and identify the Master Transcriptional Regulators of periodontitis. The transcriptional changes revealed 366 protein-coding genes and 42 non-coding genes differentially expressed and enriched in the immune response. Furthermore, we found 13 co-expression modules with different representation degrees and gene expression levels. Our GRN comprises genes from 12 gene clusters, 166 nodes, of which 33 encode Transcription Factors, and 201 connections. Finally, using these strategies, 26 master regulators of periodontitis were identified. In conclusion, combining the transcriptomic analyses with the regulatory network construction represents a powerful and efficient strategy for identifying potential periodontitis-therapeutic targets.

The First Transcriptomic Atlas of the Adult Lacrimal Gland Reveals Epithelial Complexity and Identifies Novel Progenitor Cells in Mice

The lacrimal gland (LG) secretes aqueous tears. Previous studies have provided insights into the cell lineage relationships during tissue morphogenesis. However, little is known about the cell types composing the adult LG and their progenitors. Using scRNAseq, we established the first comprehensive cell atlas of the adult mouse LG to investigate the cell hierarchy, its secretory repertoire, and the sex differences. Our analysis uncovered the complexity of the stromal landscape. Epithelium subclustering revealed myoepithelial cells, acinar subsets, and two novel acinar subpopulations: Tfrchi and Car6hi cells. The ductal compartment contained Wfdc2+ multilayered ducts and an Ltf+ cluster formed by luminal and intercalated duct cells. Kit+ progenitors were identified as: Krt14+ basal ductal cells, Aldh1a1+ cells of Ltf+ ducts, and Sox10+ cells of the Car6hi acinar and Ltf+ epithelial clusters. Lineage tracing experiments revealed that the Sox10+ adult populations contribute to the myoepithelial, acinar, and ductal lineages. Using scRNAseq data, we found that the postnatally developing LG epithelium harbored key features of putative adult progenitors. Finally, we showed that acinar cells produce most of the sex-biased lipocalins and secretoglobins detected in mouse tears. Our study provides a wealth of new data on LG maintenance and identifies the cellular origin of sex-biased tear components.

Antimicrobial peptides: Defending the mucosal epithelial barrier

The recent epidemic caused by aerosolized SARS-CoV-2 virus illustrates the importance and vulnerability of the mucosal epithelial barrier against infection. Antimicrobial proteins and peptides (AMPs) are key to the epithelial barrier, providing immunity against microbes. In primitive life forms, AMPs protect the integument and the gut against pathogenic microbes. AMPs have also evolved in humans and other mammals to enhance newer, complex innate and adaptive immunity to favor the persistence of commensals over pathogenic microbes. The canonical AMPs are helictical peptides that form lethal pores in microbial membranes. In higher life forms, this type of AMP is exemplified by the defensin family of AMPs. In epithelial tissues, defensins, and calprotectin (complex of S100A8 and S100A9) have evolved to work cooperatively. The mechanisms of action differ. Unlike defensins, calprotectin sequesters essential trace metals from microbes, which inhibits growth. This review focuses on defensins and calprotectin as AMPs that appear to work cooperatively to fortify the epithelial barrier against infection. The antimicrobial spectrum is broad with overlap between the two AMPs. In mice, experimental models highlight the contribution of both AMPs to candidiasis as a fungal infection and periodontitis resulting from bacterial dysbiosis. These AMPs appear to contribute to innate immunity in humans, protecting the commensal microflora and restricting the emergence of pathobionts and pathogens. A striking example in human innate immunity is that elevated serum calprotectin protects against neonatal sepsis. Calprotectin is also remarkable because of functional differences when localized in epithelial and neutrophil cytoplasm or released into the extracellular environment. In the cytoplasm, calprotectin appears to protect against invasive pathogens. Extracellularly, calprotectin can engage pathogen-recognition receptors to activate innate immune and proinflammatory mechanisms. In inflamed epithelial and other tissue spaces, calprotectin, DNA, and histones are released from degranulated neutrophils to form insoluble antimicrobial barriers termed neutrophil extracellular traps. Hence, calprotectin and other AMPs use several strategies to provide microbial control and stimulate innate immunity.