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Systemic dissemination of inflammation-related proteins has been linked to unhealthy ageing and increased mortality. Yet, the systemic inflammatory profile of periodontitis, a common oral inflammatory disease, remains poorly characterised. The aim of this study was to evaluate the existing evidence linking alterations in serum levels of inflammation-related proteins to periodontitis. This study was registered in Prospero (CRD42024597308). The inclusion criteria were original, English language studies of human participants ≥16 years that assessed serum biomarkers in individuals with periodontitis and periodontally healthy controls. PubMed, Scopus, and Web of Science were searched on October 13, 2024, and complemented with a hand search. Two independent reviewers performed abstract screening, full-text assessment, risk-of-bias assessment (modified Newcastle-Ottawa Scale), and extraction of summary data. A random-effects meta-analysis was performed to estimate the ratio of mean protein (RoM) level between periodontitis cases and controls. From 9120 screened records, 206 studies were included in the qualitative data synthesis, yielding 17953 participants (157 unique proteins) in total. Data from 144 studies (39 proteins) were included in the meta-analysis. In individuals with periodontitis compared with controls, analyses showed significantly (P<0.05) higher levels of C-C motif chemokine ligand 2 (CCL2); interleukin (IL)-1β, IL-6, IL-17, IL-17A and IL-18; leptin; matrix metalloproteinase 8 (MMP-8), myeloperoxidase (MPO); receptor activator of nuclear factor kappa-Β ligand (RANKL); and tumour necrosis factor α (TNF-α). Notably, CCL2, IL-1β, IL-6, IL-17, IL-17A, MMP-8, RANKL and TNF-α remained significantly elevated even in analyses restricted to systemically healthy participants, with additional significant associations observed for IL-12 and IL-33. Periodontitis is, independently of comorbidities, associated with systemic inflammation and with specific cytokines involved in metabolic and immune dysregulation, including inflammaging. These findings highlight the systemic impact of periodontitis and the importance of reducing the inflammatory burden to promote healthy aging and longevity.

Introduction: Periodontitis is associated with rheumatoid arthritis (RA). One hypothesis posits that this connection arises from the formation of autoantibodies against citrullinated proteins (ACPA) in inflamed gums, possibly triggered by Porphyromonas gingivalis. We previously demonstrated an increased antibody response to P. gingivalis arginine gingipains (anti-Rgp IgG), not only in individuals with severe periodontitis compared to controls, but in RA versus controls, with an association to ACPA. In the present study, we set out to further explore the relationship between anti-Rgp IgG, ACPA and periodontitis, including clinical periodontal parameters, in the large and well-characterized PerioGene North case-control study.

Methods: We measured serum levels of anti-Rgp and ACPA IgG by enzyme-linked immunosorbent assay (ELISA), in 478 patients with periodontitis and 509 periodontally healthy controls within PerioGene North. Subsequently, anti-Rgp IgG levels and ACPA status were analysed in relation to periodontitis and clinical periodontal parameters.

Results: Serum anti-Rgp IgG levels were elevated in cases versus controls (p< 0.001). However, receiver operating characteristic (ROC) curve analysis revealed that anti-Rgp IgG could not efficiently discriminate cases from controls (AUC= 0.63; 95% CI: 0.60 – 0.66). Among cases, increased anti-Rgp IgG levels associated with high periodontal inflammation and advanced alveolar bone loss (p<0.001 for both). An ACPA response was detected in 15 (3.1%) cases and 6 (1.2%) controls (p=0.033), but no association to periodontitis was evident after adjustment for age and smoking and anti-Rgp IgG levels did not differ between ACPA-positive and ACPA-negative individuals.

Conclusion: We show that anti-Rgp IgG identifies a subgroup of periodontitis patients with high degree of periodontal inflammation and advanced alveolar bone loss, but we do not find support for a link between periodontitis or anti-Rgp IgG and ACPA status in PerioGene North. Given the association between anti-Rgp and alveolar bone loss, the mechanistic role of gingipains in bone resorption should be experimentally explored.

Background: Host-modulating therapy is a possible treatment for individuals that respond poorly to conventional periodontal therapy. B cells, abundant in periodontitis lesions, require the cytokines B cell-activating factor (BAFF) and A proliferation-inducing ligand (APRIL) for survival and maturation. Although mRNA levels of BAFF and APRIL are increased in tissue from periodontitis lesions, it is unknown if periodontal resident cells express BAFF and/or APRIL during periodontal inflammation. In this study, we aim to analyze the expression of BAFF and APRIL in human gingival fibroblasts after stimulation with proinflammatory cytokines. Furthermore, we perform protein analysis in tissues and serum from periodontitis patients and healthy controls.

Methods: Human gingival fibroblasts were cultured and stimulated with the proinflammatory cytokines’ tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). The mRNA expression of BAFF and APRIL was analyzed by real-time quantitative polymerase chain reaction (qPCR), and the protein was detected in tissue sections using immune staining. Serum levels of BAFF were analyzed with enzyme-linked immunosorbent assay (ELISA).

Results: In gingival fibroblasts, TNF-α upregulated BAFF mRNA, but APRIL was unaffected. IL-1β affected neither BAFF nor APRIL expression. BAFF protein was detected in the oral epithelium and in cells of the underlying connective tissue in periodontitis tissue, and BAFF protein was increased in the serum of periodontitis patients.

Conclusion: Periodontal resident cells express BAFF during periodontal inflammation and participate in providing a favorable milieu for the survival and action of B cells.

Aim: To evaluate the protein profiles in gingival crevicular fluid (GCF) in relation to clinical outcomes after periodontal surgery and examine if any selected proteins affect the mRNA expression of pro-inflammatory cytokines in human gingival fibroblasts.

Materials and Methods: This exploratory study included 21 consecutive patients with periodontitis. GCF was collected, and the protein pattern (n = 92) and clinical parameters were evaluated prior to surgery and 3, 6 and 12 months after surgery. Fibroblastic gene expression was analysed by real-time quantitative polymerase chain reaction.

Results: Surgical treatment reduced periodontal pocket depth (PPD) and changed the GCF protein pattern. Twelve months after surgery, 17% of the pockets showed an increase in PPD. Levels of a number of proteins in the GCF decreased after surgical treatment but increased with early signs of tissue destruction, with LIGHT being one of the proteins that showed the strongest association. Furthermore, LIGHT up-regulated the mRNA expression of pro-inflammatory cytokines interleukin (IL)-6, IL-8 and MMP9 in human gingival fibroblasts.

Conclusions: LIGHT can potentially detect subjects at high risk of periodontitis recurrence after surgical treatment. Moreover, LIGHT induces the expression of inflammatory cytokines and tissue-degrading enzymes in gingival fibroblasts.

The sequalae of periodontitis include irreversible degradation of tooth-supporting structures and circulatory spread of inflammatory mediators. However, the serum protein profile in periodontitis is not well described, which is partly attributable to the limited number of studies based on large and well-characterized periodontitis cohorts. This study aims to identify novel, circulating inflammation-related proteins associated with periodontitis within the PerioGene North case-control study, which includes 478 cases with severe periodontitis and 509 periodontally healthy controls. The serum concentrations of high-sensitivity C-reactive protein (hs-CRP) and a panel of 45 inflammation-related proteins were analyzed using targeted proteomics. A distinguishable serum protein profile was evident in periodontitis cases. The protein pattern could separate cases from controls with a sensitivity of 0.81 and specificity of 0.81 (area under the curve = 0.87). Adjusted levels for hs-CRP and 24 of the 45 proteins were different between cases and controls. High levels of hs-CRP and matrix metalloproteinase–12, and low levels of epidermal growth factor (EGF) and oxidized low-density lipoprotein receptor 1 (OLR-1) were detected among the cases. Furthermore, the levels of C-C motif chemokine–19, granulocyte colony-stimulating factor–3 (CSF-3), interleukin-7 (IL-7), and hs-CRP were significantly higher in cases with a high degree of gingival inflammation. The levels of CSF-3 and tumor necrosis factor ligand superfamily member–10 TNFSF-10 were higher in cases with many deep periodontal pockets. The PerioGene North study includes detailed clinical periodontal data and uncovers a distinct serum protein profile in periodontitis. The findings of lower EGF and OLR-1 among the cases are highlighted, as this has not been presented before. The role of EGF and OLR-1 in periodontitis pathogenesis and as possible future biomarkers should be further explored.

Based on the epidemiological link between periodontitis and rheumatoid arthritis (RA), and the unique feature of the periodontal bacterium Porphyromonas gingivalis to citrullinate proteins, it has been suggested that production of anti-citrullinated protein antibodies (ACPA), which are present in a majority of RA patients, may be triggered in the gum mucosa. To address this hypothesis, we investigated the antibody response to a citrullinated P. gingivalis peptide in relation to the autoimmune ACPA response in early RA, and examined citrulline-reactivity in monoclonal antibodies derived from human gingival B cells. Antibodies to a citrullinated peptide derived from P. gingivalis (denoted CPP3) and human citrullinated peptides were analyzed by multiplex array in 2,807 RA patients and 372 controls; associations with RA risk factors and clinical features were examined. B cells from inflamed gingival tissue were single-cell sorted, and immunoglobulin (Ig) genes were amplified, sequenced, cloned and expressed (n=63) as recombinant monoclonal antibodies, and assayed for citrulline-reactivities by enzyme-linked immunosorbent assay. Additionally, affinity-purified polyclonal anti-cyclic-citrullinated peptide (CCP2) IgG, and monoclonal antibodies derived from RA blood and synovial fluid B cells (n=175), were screened for CPP3-reactivity. Elevated anti-CPP3 antibody levels were detected in RA (11%), mainly CCP2+ RA, compared to controls (2%), p<0.0001, with a significant association to HLA-DRB1 shared epitope alleles, smoking and baseline pain, but with low correlation to autoimmune ACPA fine-specificities. Monoclonal antibodies derived from gingival B cells showed cross-reactivity between P. gingivalis CPP3 and human citrullinated peptides, and a CPP3+/CCP2+ clone, derived from an RA blood memory B cell, was identified. Our data support the possibility that immunity to P. gingivalis derived citrullinated antigens, triggered in the inflamed gum mucosa, may contribute to the presence of ACPA in RA patients, through mechanisms of molecular mimicry.

There is accumulating data suggesting that periodontitis is associated with increased risk of systemic and autoimmune diseases, including cardiovascular disease, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), and there is an unmet need to identify these individuals early. With the periodontal bacteria Porphyromonas gingivalis (Pg) as one of the key drivers of periodontitis, we set out to investigate whether antibodies to Pg virulence factor arginine gingipain (Rgp) could serve as a biomarker for periodontitis patients at increased risk of autoimmunity and systemic disease. We measured serum anti-Rgp IgG in three study populations: PAROKRANK (779 individuals with myocardial infarction (MI); 719 controls), where 557 had periodontitis, and 312 were positive for autoantibodies associated with RA/SLE; the PerioGene North pilot (41 periodontitis; 39 controls); and an SLE case/control study (101 SLE; 100 controls). Anti-Rgp IgG levels were increased in severe periodontitis compared to controls (p < 0.0001), in individuals positive for anti-citrullinated protein antibodies (p = 0.04) and anti-dsDNA antibodies (p = 0.035), compared to autoantibody-negative individuals; and in MI patients versus matched controls (p = 0.035). Our data support longitudinal studies addressing the role of anti-Rgp antibodies as biomarkers for periodontitis patients at increased risk of developing autoimmunity linked to RA and SLE, and mechanisms underpinning these associations.

We recently showed that adult male mice that lacked the C–C-chemokine receptor 3 (CCR3) exhibited disturbed bone remodeling, which resulted in a cortical bone phenotype of thin femoral cortical bone. However, it remains unknown whether this phenotype would be present during bone modeling, or it affects female mice. Here, we analyzed juvenile and adolescent CCR3-deficient mice to determine when bone modeling was affected in the absence of CCR3 signaling. To investigate whether the CCR3 bone phenotype was sex-related, we analyzed both young female and male mice, and adult females.

Micro-computed tomography (μCT) and histomorphometric analyses in adolescent CCR3-deficient male mice revealed reduced cortical bone volume and thickness, and an increase in periosteal mineralization. Interestingly, no skeletal phenotype was observed in adolescent or adult female CCR3-deficient mice. Among juvenile CCR3-deficient mice, neither males nor females showed a skeletal phenotype, which indicated that bone modeling was not affected by the CCR3 deficiency.

In summary, adolescent and adult male mice that lacked CCR3 receptors exhibited a cortical phenotype that was not present in female mice, probably due to an estrogen protective mechanism. Based on these and our previous results, we suggest that the importance of CCR3 in cortical bone turnover is related to sex hormones. Because only a few molecules are known to control cortical bone turnover, our novel finding that CCR3 regulated cortical bone thickness only in males suggested that CCR3 is a novel target for controlling cortical bone morphology in male individuals, and perhaps, in post-menopausal women.

Increasing evidence emphasizes the importance of chemokines and chemokine receptors as regulators of bone remodeling. The C–C chemokine receptor 3 (CCR3) is dramatically upregulated during osteoclastogenesis, but the role of CCR3 in osteoclast formation and bone remodeling in adult mice is unknown. Herein, we used bone marrow macrophages derived from adult male CCR3-proficient and CCR3-deficient mice to study the role of CCR3 in osteoclast formation and activity. CCR3 deficiency was associated with formation of giant hypernucleated osteoclasts, enhanced bone resorption when cultured on bone slices, and altered mRNA expression of related chemokine receptors and ligands. In addition, primary mouse calvarial osteoblasts isolated from CCR3-deficient mice showed increased mRNA expression of the osteoclast activator–related gene, receptor activator of nuclear factor kappa-B ligand, and osteoblast differentiation–associated genes. Microcomputed tomography analyses of femurs from CCR3-deficient mice revealed a bone phenotype that entailed less cortical thickness and volume. Consistent with our in vitro studies, the total number of osteoclasts did not differ between the genotypes in vivo. Moreover, an increased endocortical osteoid mineralization rate and higher trabecular and cortical bone formation rate was displayed in CCR3-deficient mice. Collectively, our data show that CCR3 deficiency influences osteoblast and osteoclast differentiation and that it is associated with thinner cortical bone in adult male mice.

BACKGROUND: Innate lymphoid cells (ILCs) are the most recently identified leukocytes of the immune system and these cells are increasingly acknowledged to play important roles in host defence and tissue repair. ILCs are also contributors of inflammatory diseases such as asthma and colitis. We analyzed the presence and relative proportions of the different ILC subsets (ILC1, ILC2 and ILC3) in gingivitis and periodontitis. Further, we investigated if ILCs express receptor activator of nuclear factor kappa-B ligand (RANKL), a cytokine crucial for osteoclast differentiation and bone resorption.

METHODS: We collected gingivitis and periodontitis soft tissue and characterized ILC subsets including RANKL expression in single-cell suspensions using flow cytometry.

RESULTS: ILCs were detected both in gingivitis and periodontitis. The majority of ILCs, in both conditions, were ILC1s. Furthermore, RANKL expression was detected on a fraction of the ILC1s.

CONCLUSIONS: Our discovery of the presence of ILCs both in gingivitis and periodontitis and concomitant expression of RANKL on a fraction of the ILC1 population suggest that these cells may be of importance in periodontal disease. In addition, our findings provide a new insight into the field of oral immunology.