Immune and regulatory functions of neutrophils in inflammatory bone loss

Fibrin aggravates periodontitis through inducing NETs formation from mitochondrial DNA

OBJECTIVES

This study investigated the role of fibrin on neutrophil extracellular traps (NETs) formation from neutrophils and to elucidate the involvement of mitochondria in NETs formation during periodontitis.

MATERIALS AND METHODS

Plasminogen-deficient (Plg-/-) mice were employed to evaluate the effects of fibrin deposition on inflammation, bone resorption, and neutrophil infiltration in periodontal tissues. In addition, in vitro tests evaluated fibrin's impact on neutrophil-driven inflammation. Mitochondrial reactive oxygen species (mtROS) levels within neutrophils were quantified utilizing flow cytometry and immunofluorescence in vitro. Furthermore, the anti-inflammatory properties of the mtROS scavenger, Mito-TEMPO, were confirmed to regulate the NET formation in vitro and in vivo.

RESULTS

Plasminogen deficiency resulted in increased fibrin deposition, neutrophil infiltration, inflammatory factors concentration, and alveolar bone resorption in periodontal tissues. After neutrophils were treated by fibrin in vitro, the expression of inflammatory factors, the formation of mtROS, and NETs enriched in mitochondrial DNA (mtDNA) were upregulated, which were reversed by Mito-TEMPO in vitro. Moreover, Mito-TEMPO alleviated inflammation in Plg-/- mice.

CONCLUSIONS

This study showed that fibrin deposition in gingiva induced the NET formation in Plg-/- mice, in which the DNA in NETs was from mitochondria depending on increasing mtROS.

Bite-sized immunology; damage and microbes educating immunity at the gingiva

Immune cells residing at the gingiva experience diverse and unique signals, tailoring their functions to enable them to appropriately respond to immunological challenges and maintain tissue integrity. The gingiva, defined as the mucosal barrier that surrounds and supports the teeth, is the only barrier site completely transected by a hard structure, the tooth. The tissue is damaged in early life during tooth eruption and chronically throughout life by the process of mastication. This occurs alongside challenges typical of barrier sites, including exposure to invading pathogens, the local commensal microbial community and environmental antigens. This review will focus on the immune network safeguarding gingival integrity, which is far less understood than that resident at other barrier sites. A detailed understanding of the gingiva-resident immune network is vital as it is the site of the inflammatory disease periodontitis, the most common chronic inflammatory condition in humans which has well-known detrimental systemic effects. Furthering our understanding of how the immune populations within the gingiva develop, are tailored in health, and how this is dysregulated in disease would further the development of effective therapies for periodontitis.

A new direction in periodontitis treatment: biomaterial-mediated macrophage immunotherapy

Periodontitis is a chronic inflammation caused by a bacterial infection and is intimately associated with an overactive immune response. Biomaterials are being utilized more frequently in periodontal therapy due to their designability and unique drug delivery system. However, local and systemic immune response reactions driven by the implantation of biomaterials could result in inflammation, tissue damage, and fibrosis, which could end up with the failure of the implantation. Therefore, immunological adjustment of biomaterials through precise design can reduce the host reaction while eliminating the periodontal tissue's long-term chronic inflammation response. It is important to note that macrophages are an active immune system component that can participate in the progression of periodontal disease through intricate polarization mechanisms. And modulating macrophage polarization by designing biomaterials has emerged as a new periodontal therapy technique. In this review, we discuss the role of macrophages in periodontitis and typical strategies for polarizing macrophages with biomaterials. Subsequently, we discuss the challenges and potential opportunities of using biomaterials to manipulate periodontal macrophages to facilitate periodontal regeneration.

Effects of a stabilized stannous fluoride dentifrice on clinical, immunomodulatory, and microbial outcomes in a human experimental gingivitis model

BACKGROUND

Stannous fluoride dentifrice is well established for its beneficial clinical effects. In this study, we evaluated the effects of stannous fluoride on inflammation and oral microbiome.

METHODS

In this randomized, parallel-arm, double-blind, controlled clinical trial, we compared clinical resolution of experimental gingivitis by evaluating bleeding on probing, gingival index, and plaque index between stannous fluoride stabilized with zinc phosphate (test) and sodium fluoride (control) dentifrices. Further, these groups were compared for oral neutrophil counts, systemic priming of neutrophils, gingival crevicular fluid (GCF) expression of inflammatory markers, and the oral microbiome.

RESULTS

We found significant reduction in bleeding on probing in the test group compared to the control group in experimental gingivitis when participants used the test dentifrice prior to induction of experimental gingivitis. The test group also showed significant reductions in GCF levels of inflammatory markers (matrix metalloproteinase 8 [MMP8], receptor activator of nuclear factor kappa-Β ligand [RANKL]), oral polymorphonuclear neutrophil (PMN) counts, and systemic neutrophil priming (CD11b expression) during experimental gingivitis. Further, significant reductions in the gram-negative genera Porphyromonas, Tannerella, and Treponema were noted in the test group.

CONCLUSION

The stannous fluoride stabilized with zinc phosphate dentifrice formulation demonstrated clinical reduction in gingival inflammation and a beneficial effect on microbiome and immune markers. This intervention should be explored as a preventive aid in the progression of plaque-induced gingivitis to periodontitis.

Periodontal disease in patients with WHIM syndrome

AIM

WHIM (warts, hypogammaglobulinaemia, infections and myelokathexis) syndrome is a rare combined primary immunodeficiency disease caused by gain-of-function (GOF) mutations in the chemokine receptor CXCR4 and includes severe neutropenia as a common feature. Neutropenia is a known risk factor for periodontitis; however, a detailed periodontal evaluation of a WHIM syndrome cohort is lacking. This study aimed to establish the evidence base for the periodontal status of patients with WHIM syndrome.

MATERIALS AND METHODS

Twenty-two adult WHIM syndrome patients and 22 age- and gender-matched healthy volunteers (HVs) were evaluated through a comprehensive medical and periodontal examination. A mouse model of WHIM syndrome was assessed for susceptibility to naturally progressing or inducible periodontitis.

RESULTS

Fourteen patients with WHIM syndrome (63.6%) and one HV (4.5%) were diagnosed with Stage III/IV periodontitis. No WHIM patient presented with the early onset, dramatic clinical phenotypes typically associated with genetic forms of neutropenia. Age, but not the specific CXCR4 mutation or absolute neutrophil count, was associated with periodontitis severity in the WHIM cohort. Mice with a Cxcr4 GOF mutation did not exhibit increased alveolar bone loss in spontaneous or ligature-induced periodontitis.

CONCLUSIONS

Overall, WHIM syndrome patients presented with an increased severity of periodontitis despite past and ongoing neutrophil mobilization treatments. GOF mutations in CXCR4 may be a risk factor for periodontitis in humans.

Interaction between immuno-stem dual lineages in jaw bone formation and injury repair

The jawbone, a unique structure in the human body, undergoes faster remodeling than other bones due to the presence of stem cells and its distinct immune microenvironment. Long-term exposure of jawbones to an oral environment rich in microbes results in a complex immune balance, as shown by the higher proportion of activated macrophage in the jaw. Stem cells derived from the jawbone have a higher propensity to differentiate into osteoblasts than those derived from other bones. The unique immune microenvironment of the jaw also promotes osteogenic differentiation of jaw stem cells. Here, we summarize the various types of stem cells and immune cells involved in jawbone reconstruction. We describe the mechanism relationship between immune cells and stem cells, including through the production of inflammatory bodies, secretion of cytokines, activation of signaling pathways, etc. In addition, we also comb out cellular interaction of immune cells and stem cells within the jaw under jaw development, homeostasis maintenance and pathological conditions. This review aims to eclucidate the uniqueness of jawbone in the context of stem cell within immune microenvironment, hopefully advancing clinical regeneration of the jawbone.

Periplogenin attenuates LPS-mediated inflammatory osteolysis through the suppression of osteoclastogenesis via reducing the NF-κB and MAPK signaling pathways

The key target for treating inflammatory osteolysis is osteoclasts. In an inflammatory environment, osteoclast differentiation increases, and bone resorption is enhanced. Periplogenin (Ppg) is a traditional Chinese medicine. It has anti-inflammatory and antitumor effects, but its impact on inflammatory osteolysis is unknown. This study found that Ppg prevented LPS-induced skull osteolysis by inhibiting the expression of inflammatory cytokines and osteoclast production. In vitro, Ppg blocked the RANKL-induced generation of osteoclasts, the development of pseudopodia bands, and bone resorption. Ppg also attenuated the expression of NFATc1, c-Fos, CTSK, and Atp6v0d2 proteins by inhibiting the NFATc1 signaling pathway. In addition, Ppg inhibited the expression of osteoclast-specific genes, including NFATc1, c-Fos, CTSK, Atp6v0d2, and Mmp9. Moreover, Ppg also inhibited NF-κB and MAPK pathways. In vivo, Ppg reduced the number of osteoclasts on the surface of the bone and suppressed LPS-induced osteolysis of the skull. These outcomes suggest that Ppg can serve as a new alternative therapy for treating inflammatory osteolysis by inhibiting inflammation and osteoclasts.

Blocking CXCR1/2 attenuates experimental periodontitis by suppressing neutrophils recruitment

Periodontitis (PD) is a common chronic oral inflammatory disease that cause alveolar bone loss. Current strategies for bone regeneration achieve limited results in PD. The aberrant host osteoimmunity to pathogenic bacteria is responsible for the destruction of alveolar bone in PD. We aimed to investigate the distinctive activity of immune cells in PD to create more effective and precise therapeutic approaches for treating PD. In this study, we revealed that neutrophils in the inflamed alveolar bone of PD patients expressed higher levels of CXCR1/2 and had a stronger pro-inflammatory capacity and chemotactic ability than that in healthy individuals. Suppressing the recruitment of neutrophils to inflamed sites with the CXCR1/2 inhibitor reparixin reduced alveolar bone loss in PD mice. In this study, we not only revealed that neutrophils exhibit a heterogeneously stronger pro-inflammatory capacity in the inflamed alveolar bone of PD patients but also provided a precise therapeutic treatment for PD involving the suppression of neutrophil recruitment.

Flavonoid extract from propolis alleviates periodontitis by boosting periodontium regeneration and inflammation resolution via regulating TLR4/MyD88/NF-κB and RANK/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, propolis has been used for treating oral diseases for centuries, widely. Flavonoid extract is the main active ingredient in propolis, which has attracted extensive attention in recent years.

AIM OF THE STUDY

The objective and novelty of the current study aims to identify the mechanism of total flavonoid extract of propolis (TFP) for the treatment of periodontitis, and evaluate the therapeutic effect of TFP-loaded liquid crystal hydrogel (TFP-LLC) in rats with periodontitis.

METHODS

In this study, we used lipopolysaccharide-stimulated periodontal ligament stem cells (PDLSCs) to construct in vitro inflammation model, and investigated the anti-inflammatory effect of TFP by expression levels of inflammatory factors. Osteogenic differentiation was assessed using alkaline phosphatase activity and alizarin red staining. Meanwhile, the expression of toll like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor-kappa B (NF-κB), receptor activator of NF-κB (RANK) etc, were quantitated to investigate the therapeutic mechanism of TFP. Finally, we constructed TFP-LLC using a self-emulsification method and administered it to rats with periodontitis via periodontal pocket injection to evaluate the therapeutic effects. The therapeutic index, microcomputed tomography (Micro-CT), H&E staining, TRAP staining, and Masson staining were used for this evaluation.

RESULTS

TFP reduced the expression of TLR4, MyD88, NF-κB and inflammatory factor in lipopolysaccharide-stimulated PDLSCs. Meanwhile, TFP simultaneously regulating alkaline phosphatase, RANK, runt-associated transcription factor-2 and matrix metalloproteinase production to accelerate osteogenic differentiation and collagen secretion. In addition, TFP-LLC can stably anchor to the periodontal lesion site and sustainably release TFP. After four weeks of treatment with TFP-LLC, we observed a decrease in the levels of NF-κB and interleukin-1β (IL-1β) in the periodontal tissues of rats, as well as a significant reduction in inflammation in HE staining. Similarly, Micro CT results showed that TFP-LLC could significantly inhibit alveolar bone resorption, increase bone mineral density (BMD) and reduce trabecular bone space (Tb.Sp) in rats with periodontitis.

CONCLUSION

Collectively, we have firstly verified the therapeutic effects and mechanisms of TFP in PDLSCs for periodontitis treatment. Our results indicate that TFP perform anti-inflammatory and tissue repair activities through TLR4/MyD88/NF-κB and RANK/NF-κB pathways in PDLSCs. Meanwhile, for the first time, we employed LLC delivery system to load TFP for periodontitis treatment. The results showed that TFP-LLC could be effectively retained in the periodontal pocket and exerted a crucial role in inflammation resolution and periodontal tissue regeneration.

Current concepts in the pathogenesis of periodontitis: from symbiosis to dysbiosis

The primary etiological agent for the initiation and progression of periodontal disease is the dental plaque biofilm which is an organized aggregation of microorganisms residing within a complex intercellular matrix. The non-specific plaque hypothesis was the first attempt to explain the role of the dental biofilm in the pathogenesis of periodontal diseases. However, the introduction of sophisticated diagnostic and laboratory assays has led to the realisation that the development of periodontitis requires more than a mere increase in the biomass of dental plaque. Indeed, multispecies biofilms exhibit complex interactions between the bacteria and the host. In addition, not all resident microorganisms within the biofilm are pathogenic, since beneficial bacteria exist that serve to maintain a symbiotic relationship between the plaque microbiome and the host’s immune-inflammatory response, preventing the emergence of pathogenic microorganisms and the development of dysbiosis. This review aims to highlight the development and structure of the dental plaque biofilm and to explore current literature on the transition from a healthy (symbiotic) to a diseased (dysbiotic) biofilm in periodontitis and the associated immune-inflammatory responses that drive periodontal tissue destruction and form mechanistic pathways that impact other systemic non-communicable diseases.

NLRP3-Induced NETosis: A Potential Therapeutic Target for Ischemic Thrombotic Diseases?

Ischemic thrombotic disease, characterized by the formation of obstructive blood clots within arteries or veins, is a condition associated with life-threatening events, such as stroke, myocardial infarction, deep vein thrombosis, and pulmonary embolism. The conventional therapeutic strategy relies on treatments with anticoagulants that unfortunately pose an inherent risk of bleeding complications. These anticoagulants primarily target clotting factors, often overlooking upstream events, including the release of neutrophil extracellular traps (NETs). Neutrophils are integral components of the innate immune system, traditionally known for their role in combating pathogens through NET formation. Emerging evidence has now revealed that NETs contribute to a prothrombotic milieu by promoting platelet activation, increasing thrombin generation, and providing a scaffold for clot formation. Additionally, NET components enhance clot stability and resistance to fibrinolysis. Clinical and preclinical studies have underscored the mechanistic involvement of NETs in the pathogenesis of thrombotic complications, since the clots obtained from patients and experimental models consistently exhibit the presence of NETs. Given these insights, the inhibition of NETs or NET formation is emerging as a promising therapeutic approach for ischemic thrombotic diseases. Recent investigations also implicate a role for the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome as a mediator of NETosis and thrombosis, suggesting that NLRP3 inhibition may also hold potential for mitigating thrombotic events. Therefore, future preclinical and clinical studies aimed at identifying and validating NLRP3 inhibition as a novel therapeutic intervention for thrombotic disorders are imperative.

High systemic immune-inflammation index is relevant to osteoporosis among middle-aged and older people: A cross-sectional study

BACKGROUND

As one of novel inflammatory indexes proposed in recent years, systemic immune-inflammation index (SII) can comprehensively reflect the inflammatory and immune state of the body. This study aims to explore the relationship between SII and osteoporosis among middle-aged and older people.

MATERIALS AND METHODS

Our study includes 20,497 individuals from National Health and Nutrition Examination Survey (NHANES) 2005-2008, and target study population are confined to people aged 45 years and above. SII is calculated as platelet count × neutrophil count/lymphocyte count. Multivariate logistic regression analysis is used to explore the link between SII and osteoporosis, and receiver operating characteristics curve is used to screen optimal cut-off value of SII for indicating the occurrence of osteoporosis.

RESULTS

A total of 435 people with osteoporosis are screened among 4625 middle-aged and older people, and individuals in osteoporosis group have higher SII than those in nonosteoporosis group (p = .024). Logistic regression analysis indicates that with the enhancement of SII, prevalence of osteoporosis in each tertile category also increases (p < .001). This tendency is also not changed in univariate model (p < .001), as well as the adjustments for different parameters. Moreover, we also identify that SII of 530.09 is the optimal cut-off value for indicating the occurrence of osteoporosis among middle-aged and older people.

CONCLUSIONS

This present NHANES-based study noticed that higher SII is positively linked to osteoporosis among middle-aged and older people, and SII should not exceed 530.09 for them to obtain a potentially lower risk of osteoporosis.

Dysregulation of CXCL1 Expression and Neutrophil Recruitment in Insulin Resistance and Diabetes-Related Periodontitis in Male Mice

Insulin resistance and hyperglycemia are risk factors for periodontitis and poor wound healing in diabetes, which have been associated with selective loss of insulin activation of the PI3K/Akt pathway in the gingiva. This study showed that insulin resistance in the mouse gingiva due to selective deletion of smooth muscle and fibroblast insulin receptor (SMIRKO mice) or systemic metabolic changes induced by a high-fat diet (HFD) in HFD-fed mice exacerbated periodontitis-induced alveolar bone loss, preceded by delayed neutrophil and monocyte recruitment and impaired bacterial clearance compared with their respective controls. The immunocytokines, CXCL1, CXCL2, MCP-1, TNFα, IL-1β, and IL-17A, exhibited delayed maximal expression in the gingiva of male SMIRKO and HFD-fed mice compared with controls. Targeted overexpression of CXCL1 in the gingiva by adenovirus normalized neutrophil and monocyte recruitment and prevented bone loss in both mouse models of insulin resistance. Mechanistically, insulin enhanced bacterial lipopolysaccharide-induced CXCL1 production in mouse and human gingival fibroblasts (GFs), via Akt pathway and NF-κB activation, which were reduced in GFs from SMIRKO and HFD-fed mice. These results provided the first report that insulin signaling can enhance endotoxin-induced CXCL1 expression to modulate neutrophil recruitment, suggesting CXCL1 as a new therapeutic direction for periodontitis or wound healing in diabetes.

ARTICLE HIGHLIGHTS

The mechanism for the increased risks for periodontitis in the gingival tissues due to insulin resistance and diabetes is unclear. We investigated how insulin action in gingival fibroblasts modulates the progression of periodontitis in resistance and diabetes. Insulin upregulated the lipopolysaccharide-induced neutrophil chemoattractant, CXCL1, production in gingival fibroblasts via insulin receptors and Akt activation. Enhancing CXCL1 expression in the gingiva normalized diabetes and insulin resistance-induced delays in neutrophils recruitment and periodontitis. Targeting dysregulation of CXCL1 in fibroblasts is potentially therapeutic for periodontitis and may also improve wound healing in insulin resistance and diabetes.

Identification of key immune genes of osteoporosis based on bioinformatics and machine learning

Introduction

Immunity is involved in a variety of bone metabolic processes, especially osteoporosis. The aim of this study is to explore new bone immune-related markers by bioinformatics method and evaluate their ability to predict osteoporosis.

Methods

The mRNA expression profiles were obtained from GSE7158 in Gene expression Omnibus (GEO), and immune-related genes were obtained from ImmPort database (https://www.immport.org/shared/). immune genes related to bone mineral density(BMD) were screened out for differential analysis. protein-protein interaction (PPIs) networks were used to analyze the interrelationships between different immune-related genes (DIRGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DIRGs function were performed. A least absolute shrinkage and selection operation (LASSO) regression model and multiple Support Vector Machine-Recursive Feature Elimination (mSVM-RFE) model were constructed to identify the candidate genes for osteoporosis prediction The receiver operator characteristic (ROC) curves were used to validate the performances of predictive models and candidate genes in GEO database (GSE7158,GSE13850).Through the RT - qPCR verify the key genes differentially expressed in peripheral blood mononuclear cells Finally, we constructed a nomogram model for predicting osteoporosis based on five immune-related genes. CIBERSORT algorithm was used to calculate the relative proportion of 22 immune cells.

Results

A total of 1158 DEGs and 66 DIRGs were identified between high-BMD and low-BMD women. These DIRGs were mainly enriched in cytokine-mediated signaling pathway, positive regulation of response to external stimulus and the cellular components of genes are mostly localized to external side of plasma membrane. And the KEGG enrichment analysis were mainly involved in Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Neuroactive ligand-receptor interaction,Natural killer cell mediated cytotoxicity. Then five key genes (CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1) were identified and used as features to construct a predictive prognostic model for osteoporosis using the GSE7158 dataset.

Conclusion

Immunity plays an important role in the development of osteoporosis.CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1were play an important role in the occurrences and diagnosis of OP.

Maresin1: A multifunctional regulator in inflammatory bone diseases

Inflammation plays a crucial role in the physical response to danger signals, the elimination of toxic stimuli, and the restoration of homeostasis. However, dysregulated inflammatory responses lead to tissue damage, and chronic inflammation can disrupt osteogenic-osteoclastic homeostasis, ultimately leading to bone loss. Maresin1 (MaR1), a member of the specialized pro-resolving mediators (SPMs) family, has been found to possess significant anti-inflammatory, anti-allergic, pro-hemolytic, pro-healing, and pain-relieving properties. MaR1 is synthesized by macrophages (Mφs) and omega-3 fatty acids, and it may have the potential to promote bone homeostasis and treat inflammatory bone diseases. MaR1 has been found to stimulate osteoblast proliferation through leucine-rich repeat G protein-coupled receptor 6 (LGR6). It also activates Mφ phagocytosis and M2-type polarization, which helps to control the immune system. MaR1 can regulate T cells to exert anti-inflammatory effects and inhibit neutrophil infiltration and recruitment. In addition, MaR1 is involved in antioxidant signaling, including nuclear factor erythroid 2-related factor 2 (NRF2). It has also been found to promote the autophagic behavior of periodontal ligament stem cells, stimulate Mφs against pathogenic bacteria, and regulate tissue regeneration and repair. In summary, this review provides new information and a comprehensive overview of the critical roles of MaR1 in inflammatory bone diseases, indicating its potential as a therapeutic approach for managing skeletal metabolism and inflammatory bone diseases.

Detection of orthodontically induced inflammatory root resorption-associated biomarkers from the gingival crevicular fluid by proteomics analysis: a randomized-controlled clinical trial

Orthodontically induced inflammatory root resorption (OIIRR) is an undesirable complication of orthodontic treatment (OT) with an ambiguous aetiologic mechanism. This study aimed to identify OIIRR-associated biomarkers in the gingival crevicular fluid (GCF) using proteomic analysis. In this randomized clinical trial, the upper first premolars (UFP) were exposed either to light or heavy force. The GCF was collected at 1 h, 1 day, 7 days, 14 days, 21 days, and 28 days following force application. After extraction of UFP, roots were imaged and resorption premolar, was used to deliver either light forcecraters were measured. Proteomic analysis of GCF was performed using 2D gel electrophoresis with MALDI-TOF/TOF MS/MS. Results were further analyzed by bioinformatics analyses showing the biological functions and predicted pathways. The predicted canonical pathways showed that the expression of immunoglobulin kappa (IGKC), neutrophil gelatinase-associated lipocalin (NGAL), neurolysin mitochondrial (NEUL), keratin, type II cytoskeletal 1 (K2C1), S100-A9, and the extracellular calcium-sensing receptor (CASR) were significantly associated with a range of biological and inflammatory processes. In conclusion, up-regulation of S100A9, CASR, and K2C1 suggested a response to force-related inflammation, chemotactic activities, osteoclastogenesis, and epithelial cell breakdown. Meanwhile, the up-regulation of IGKC, NGAL, and K2C1 indicated a response to the inflammatory process, innate immunity activation, and epithelial cell breakdown.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03572-5.

Neutrophils are gatekeepers of mucosal immunity

Mucosal tissues are constantly exposed to the outside environment. They receive signals from the commensal microbiome and tissue-specific triggers including alimentary and airborne elements and are tasked to maintain balance in the absence of inflammation and infection. Here, we present neutrophils as sentinel cells in mucosal immunity. We discuss the roles of neutrophils in mucosal homeostasis and overview clinical susceptibilities in patients with neutrophil defects. Finally, we present concepts related to specification of neutrophil responses within specific mucosal tissue microenvironments.

Neutrophils in the periodontium: Interactions with pathogens and roles in tissue homeostasis and inflammation

Neutrophils are of key importance in periodontal health and disease. In their absence or when they are functionally defective, as occurs in certain congenital disorders, affected individuals develop severe forms of periodontitis in early age. These observations imply that the presence of immune-competent neutrophils is essential to homeostasis. However, the presence of supernumerary or hyper-responsive neutrophils, either because of systemic priming or innate immune training, leads to imbalanced host-microbe interactions in the periodontium that culminate in dysbiosis and inflammatory tissue breakdown. These disease-provoking imbalanced interactions are further exacerbated by periodontal pathogens capable of subverting neutrophil responses to their microbial community's benefit and the host's detriment. This review attempts a synthesis of these findings for an integrated view of the neutrophils' ambivalent role in periodontal disease and, moreover, discusses how some of these concepts underpin the development of novel therapeutic approaches to treat periodontal disease.

Positive Effects of Biologics on Osteoporosis in Rheumatoid Arthritis

Osteoporosis is a systemic skeletal disorder that causes vulnerability of bones to fracture owing to reduction in bone density and deterioration of the bone tissue microstructure. The prevalence of osteoporosis is higher in patients with autoimmune inflammatory rheumatic diseases, including rheumatoid arthritis (RA), than in those of the general population. In this autoimmune inflammatory rheumatic disease, in addition to known risk factors for osteoporosis, various factors such as chronic inflammation, autoantibodies, metabolic disorders, drugs, and decreased physical activity contribute to additional risk. In RA, disease-related inflammation plays an important role in local or systemic bone loss, and active treatment for inflammation can help prevent osteoporosis. In addition to conventional synthetic disease-modifying anti-rheumatic drugs that have been traditionally used for treatment of RA, biologic DMARDs and targeted synthetic DMARDs have been widely used. These agents can be employed more selectively and precisely based on disease pathogenesis. It has been reported that these drugs can inhibit bone loss by not only reducing inflammation in RA, but also by inhibiting bone resorption and promoting bone formation. In this review, the pathogenesis and research results of the increase in osteoporosis in RA are reviewed, and the effects of biological agents on osteoporosis are discussed.

Upregulated Vanins and their potential contribution to periodontitis

BACKGROUND

Although Vanins are closely related to neutrophil regulation and response to oxidative stress, and play essential roles in inflammatory diseases with clinical significance, their contribution to periodontitis remains to be determined. This research was designed to assess the expression of Vanins in human gingiva, and to define the relationship between Vanins and periodontitis.

METHODS

Forty-eight patients with periodontitis and forty-two periodontal healthy individuals were enrolled for gingival tissue sample collection. Expression levels of VNN1, VNN2 and VNN3 were evaluated by RT-qPCR and validated in datasets GSE10334 and GSE16134. Western blot and immunohistochemistry identified specific proteins within gingiva. The histopathological changes in gingival sections were investigated using HE staining. Correlations between Vanins and clinical parameters, PD and CAL; between Vanins and inflammation, IL1B; and between Vanins and MPO in periodontitis were investigated by Spearman's correlation analysis respectively. Associations between VNN2 and indicators of neutrophil adherence and migration were further validated in two datasets.

RESULTS

Vanins were at higher concentrations in diseased gingival tissues in both RT-qPCR and dataset analysis (p < 0.01). Assessment using western blot and immunohistochemistry presented significant upregulations of VNN1 and VNN2 in periodontitis (p < 0.05). The higher expression levels of Vanins, the larger the observed periodontal parameters PD and CAL (p < 0.05), and IL1B (p < 0.001). Moreover, positive correlations existed between VNN2 and MPO, and between VNN2 and neutrophil-related indicators.

CONCLUSION

Our study demonstrated upregulation of Vanins in periodontitis and the potential contribution of VNN2 to periodontitis through neutrophils-related pathological processes.

Excessive inflammatory response to infection in experimental peri-implantitis: Resolution by Resolvin D2

AIM

The aetiology and pathogenesis of peri-implantitis are currently under active research. This study aimed to dissect the pathogenesis of murine experimental peri-implantitis and assess Resolvin D2 (RvD2) as a new treatment modality.

MATERIALS AND METHODS

Four weeks following titanium implant insertion, mice were infected with Porphyromonas gingivalis using single or multiple oral lavages. RvD2 was administrated following infection, and tissues were analysed using flow cytometry, quantitative RT-PCR, taxonomic profiling, and micro-computed tomography.

RESULTS

Repeated infections with Pg resulted in microbial dysbiosis and a higher influx of innate and adaptive leukocytes to the peri-implant mucosa (PIM) than to gingiva surrounding the teeth. This was accompanied by increased expression levels of IFN-α, IL-1β, and RANKL\OPG ratio. Interestingly, whereas repetitive infections resulted in bone loss around implants and teeth, a single infection induced bone loss only around implants, suggesting a higher susceptibility of the implants to infection. Treatment with RvD2 prevented Pg-driven bone loss and reduced leukocyte infiltration to the PIM.

CONCLUSIONS

Murine dental implants are associated with dysregulated local immunity and increase susceptibility to pathogen-induced peri-implantitis. However, the disease can be prevented by RvD2 treatment, highlighting the promising therapeutic potential of this treatment modality.

Porphyromonas gingivalis and dental stem cells crosstalk amplify inflammation and bone loss in the periodontitis niche

Periodontitis is the sixth most prevalent disease, and almost 3.5 billion people are affected globally by dental caries and periodontal diseases. The microbial shift from a symbiotic microbiota to a dysbiotic microbiota in the oral cavity generally initiates periodontal disease. Pathogens in the periodontal microenvironment interact with stem cells to modulate their regenerative potential. Therefore, this review focuses on the interaction between microbes and stem cells in periodontitis conditions. Microbes direct dental stem cells to secrete a variety of pro-inflammatory cytokines and chemokines, which increase the inflammatory burden in the damaged periodontal tissue, which further aggravates periodontitis. Microbial interaction also decreases the osteogenic differentiation potential of dental stem cells by downregulating alkaline phosphatase, runt-related transcription factor 2, type 1 collagen, osteocalcin, osteopontin, and so on. Microbe and stem cell interaction amplifies pro-inflammatory cytokine signaling in the periodontitis niche, decreasing the osteogenic commitment of dental stem cells. A clear understanding of microbial stem cell interactions is crucial in designing regenerative therapies using stem cells in the management of periodontitis.

Critical roles for CCR2 and the therapeutic potential of cenicriviroc in periodontitis: a pre-clinical study

AIM

CCR2 plays important roles in many inflammatory and bone metabolic diseases, but its specific role in periodontitis is unknown. In the present study, we aimed to explore the role of CCR2 in the progression of periodontitis and evaluate the effect of cenicriviroc (CVC) on periodontitis.

METHODS

The expression of CCR2 was studied in patients with periodontitis and in ligation-induced murine model of periodontitis. The role of CCR2 in promoting inflammation and bone resorption in periodontitis was evaluated in Ccr2^-/- mice and wild-type mice. The effect of CVC in the prevention and treatment of periodontitis was evaluated by systemic and local medication. Micro-CT, Hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, real-time qPCR, ELISA, and flow cytometric were used for histomorphology, molecular biology and cytology analysis respectively.

RESULTS

In this study, we demonstrated that CCR2 was highly expressed in human and murine periodontitis and that CCR2 deficiency was associated with decreased inflammation, alveolar bone resorption, osteoclast number, monocyte and macrophage infiltration. Prevention and treatment with CVC significantly reduced the severity of periodontitis, regardless of whether it was administered systemically or locally.

CONCLUSION

CCR2 plays an important role in the development and progression of periodontitis and CVC is a potential drug for the prevention and treatment of periodontitis.

Immunology of osteoporosis: relevance of inflammatory targets for the development of novel interventions

Osteoporosis is recognized as low bone mass and deteriorated bone microarchitecture. It is the leading cause of fractures and consequent morbidity globally. The established pathophysiological evidence favors the endocrine factors for osteoporosis and the role of the immune system on the skeletal system has been recently identified. Due to the common developmental niche bone and immune system interactions have led to the emergence of osteoimmunology. Immune dysregulation can initiate inflammatory conditions that adversely affect bone integrity. The role of immune cells, such as T-lymphocytes subsets (Th17), cannot be neglected in the pathogenesis of osteoporosis. Local inflammation within the bone from any cause attracts immune cells that participate in the activation of osteoclasts. This work summarizes the present knowledge of osteoimmunology in reference to osteoporosis and identifies novel targets for immunotherapy of osteoporosis.

Erxian herbal pair enhances bone formation in infected bone nonunion models and attenuates lipopolysaccharide-induced osteoblastinhibition by regulating miRNA-34a-5p

Bacterium-induced inflammatory responses cause bone nonunion. Although antibiotics suppress infection, bone loss after antibacterial treatment remains a critical challenge. Erxian herbal pair (EHP) has been proven effective in promoting bone formation. Our study aimed to investigate the effect of EHP on bone repair after anti-infection treatment, explore its effect on a lipopolysaccharide (LPS)-induced osteoblast. We evaluated effects of EHP on bone repair with Micro-CT, and morphology detecting. Chemical constituents of EHP and EHP-containing serum (EHP-CS) were identified by UHPLC-Q/TOF-MS. In addition, osteoblast induced by LPS was established and administrated with EHP-CS. Cell proliferationwas assessed by MTT. Target prediction identified SMAD2 as a potential target of miRNA-34a-5p. MiRNA mimic, inhibitor and siRNA were transiently transfected into osteoblasts. The mRNA levels and protein expressions of miRNA-34a-5p, BMP2, Runx2, SMAD2 were assessed. The results showed that the main biocactivity ingredients in EHP-CS were Baohuoside Ι and Orcinol Glucoside. EHP could promote bone remolding after anti-infection therapy and restore the activity of LPS-induced osteoblasts. Moreover, miRNA-34a-5p was dramatically downregulated and SMAD2 was upregulated after LPS stimulation, while EHP resisted the inhibition of LPS by promoting miRNA-34a-5p, ALP, and BMP2 expressions. Whereas downregulation of miRNA-34a-5p reversed these effects. Silencing endogenous SMAD2 expression markedly promoted BMP2 and ALP activity and enhanced osteogenesis. Taken together, EHP restored LPS-induced bone loss by regulating miRNA-34a-5p levels and repressing its target gene SMAD2. EHP might be a potential adjuvant herbal remedy for the treatment of bone nonunion, and miRNA-34a-5p is a novel target for controlling bone and metabolic diseases.

Comparative Analysis of Gene Expression Patterns for Oral Epithelial Cell Functions in Periodontitis

The structure and function of epithelial cells are critical for the construction and maintenance of intact epithelial surfaces throughout the body. Beyond the mechanical barrier functions, epithelial cells have been identified as active participants in providing warning signals to the host immune and inflammatory cells and in communicating various detailed information on the noxious challenge to help drive specificity in the characteristics of the host response related to health or pathologic inflammation. Rhesus monkeys were used in these studies to evaluate the gingival transcriptome for naturally occurring disease samples (GeneChip® Rhesus Macaque Genome Array) or for ligature-induced disease (GeneChip® Rhesus Gene 1.0 ST Array) to explore up to 452 annotated genes related to epithelial cell structure and functions. Animals were distributed by age into four groups: ≤ 3 years (young), 3–7 years (adolescent), 12–16 years (adult), and 18–23 years (aged). For naturally occurring disease, adult and aged periodontitis animals were used, which comprised 34 animals (14 females and 20 males). Groups of nine animals in similar age groups were included in a ligature-induced periodontitis experiment. A buccal gingival sample from either healthy or periodontitis-affected tissues were collected, and microarray analysis performed. The overall results of this investigation suggested a substantial alteration in epithelial cell functions that occurs rapidly with disease initiation. Many of these changes were prolonged throughout disease progression and generally reflect a disruption of normal cellular functions that would presage the resulting tissue destruction and clinical disease measures. Finally, clinical resolution may not signify biological resolution and represent a continued risk for disease that may require considerations for additional biologically specific interventions to best manage further disease.

Oral Cells-On-Chip: Design, Modeling and Experimental Results

Recent advances in periodontal studies have attracted the attention of researchers to the relation between oral cells and gum diseases, which is a real threat to overall human health. Among various microfabrication technologies, Complementary Metal Oxide Semiconductors (CMOSs) enable the development of low-cost integrated sensors and circuits for rapid and accurate assessment of living cells that can be employed for the early detection and control of periodontal diseases. This paper presents a CMOS capacitive sensing platform that can be considered as an alternative for the analysis of salivatory cells such as oral neutrophils. This platform consists of two sensing electrodes connected to a read-out capacitive circuitry designed and fabricated on the same chip using Austria Mikro Systeme (AMS) 0.35 µm CMOS process. A graphical user interface (GUI) was also developed to interact with the capacitive read-out system and the computer to monitor the capacitance changes due to the presence of saliva cells on top of the chip. Thanks to the wide input dynamic range (IDR) of more than 400 femto farad (fF) and high resolution of 416 atto farad (aF), the experimental and simulation results demonstrate the functionality and applicability of the proposed sensor for monitoring cells in a small volume of 1 µL saliva samples. As per these results, the hydrophilic adhesion of oral cells on the chip varies the capacitance of interdigitated electrodes (IDEs). These capacitance changes then give an assessment of the oral cells existing in the sample. In this paper, the simulation and experimental results set a new stage for emerging sensing platforms for testing oral samples.

Osteoimmunology in Periodontitis: Local Proteins and Compounds to Alleviate Periodontitis

Periodontitis is one of the most common oral diseases resulting in gingival inflammation and tooth loss. Growing evidence indicates that it results from dysbiosis of the oral microbiome, which interferes with the host immune system, leading to bone destruction. Immune cells activate periodontal ligament cells to express the receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL) and promote osteoclast activity. Osteocytes have active roles in periodontitis progression in the bone matrix. Local proteins are involved in bone regeneration through functional immunological plasticity. Here, we discuss the current knowledge of cellular and molecular mechanisms in periodontitis, the roles of local proteins, and promising synthetic compounds generating a periodontal regeneration effect. It is anticipated that this may lead to a better perception of periodontitis pathophysiology.

NLRP3 Is Involved in Neutrophil Mobilization in Experimental Periodontitis

The NLRP3 inflammasome is overexpressed in gingiva of periodontitis patients but its role remains unclear. In our study, we use a periodontitis mouse model of ligature, impregnated or not with Porphyromonas gingivalis, in WT or NLRP3 KO mice. After 28 days of induction, ligature alone provoked exacerbated periodontal destruction in KO mice, compared to WT mice, with an increase in activated osteoclasts. No difference was observed at 14 days, suggesting that NLRP3 is involved in regulatory pathways that limit periodontitis. In contrast, in the presence of P. gingivalis, this protective effect of NLRP3 was not observed. Overexpression of NLRP3 in connective tissue of WT mice increased the local production of mature IL-1β, together with a dramatic mobilization of neutrophils, bipartitely distributed between the site of periodontitis induction and the alveolar bone crest. P. gingivalis enhanced the targeting of NLRP3-positive neutrophils to the alveolar bone crest, suggesting a role for this subpopulation in bone loss. Conversely, in NLRP3 KO mice, mature IL-1β expression was lower and almost no neutrophils were mobilized. Our study sheds new light on the role of NLRP3 in periodontitis by highlighting the ambiguous role of neutrophils, and P. gingivalis which affects NLRP3 functions.

Understanding the Role of LFA-1 in Leukocyte Adhesion Deficiency Type I (LAD I): Moving towards Inflammation?

LFA-1 (Lymphocyte function-associated antigen-1) is a heterodimeric integrin (CD11a/CD18) present on the surface of all leukocytes; it is essential for leukocyte recruitment to the site of tissue inflammation, but also for other immunological processes such as T cell activation and formation of the immunological synapse. Absent or dysfunctional expression of LFA-1, caused by mutations in the ITGB2 (integrin subunit beta 2) gene, results in a rare immunodeficiency syndrome known as Leukocyte adhesion deficiency type I (LAD I). Patients suffering from severe LAD I present with recurrent infections of the skin and mucosa, as well as inflammatory symptoms complicating the clinical course of the disease before and after allogeneic hematopoietic stem cell transplantation (alloHSCT); alloHSCT is currently the only established curative treatment option. With this review, we aim to provide an overview of the intrinsic role of inflammation in LAD I.

Periodontal Disease Augments Cardiovascular Disease Risk Biomarkers in Rheumatoid Arthritis

Objectives: Periodontal disease (PD) and rheumatoid arthritis (RA) are known chronic conditions with sustained inflammation leading to osteolysis. Cardiovascular diseases (CVD) are frequent comorbidities that may arise from sustained inflammation associated with both PD and RA. In order to determine CVD risk, alterations at the molecular level need to be identified. The objective of this study, therefore, was to assess the relationship of CVD associated biomarkers in RA patients and how it is influenced by PD. Methods: The study consisted of patient (26 RA with PD, 21 RA without PD, 51 patients with PD only) and systemically and periodontally healthy control (n = 20) groups. Periodontal parameters bleeding on probing, probing pocket depth, and marginal bone loss were determined to characterize the patient groups. Proteomic analysis of 92 CVD-related protein biomarkers was performed using a multiplex proximity extension assay. Biomarkers were clustered using the search tool for retrieval of interacting genes (STRING) to determine protein−protein interaction (PPI) networks. Results: RA patients with PD had higher detection levels for 47% of the measured markers (ANGPT1, BOC, CCL17, CCL3, CD4, CD84, CTRC, FGF-21, FGF-23, GLO1, HAOX1, HB-EGF, hOSCAR, HSP 27, IL16, IL-17D, IL18, IL-27, IL6, LEP, LPL, MERTK, MMP12, MMP7, NEMO, PAPPA, PAR-1, PARP-1, PD-L2, PGF, PIgR, PRELP, RAGE, SCF, SLAMF7, SRC, THBS2, THPO, TNFRSF13B, TRAIL-R2, VEGFD, VSIG2, and XCL1) as compared to RA without PD. Furthermore, a strong biological network was identified amongst these proteins (clustering coefficient = 0.52, PPI enrichment p-value < 0.0001). Coefficients for protein clusters involved in CVD (0.59), metabolic (0.53), and skeletal (0.51) diseases were strongest in the PD group. Conclusion: Periodontal disease augments CVD-related biomarkers in RA through shared pathological clusters, concurrently enhancing metabolic and skeletal disease protein interactions, independent of autoimmune status.

Nociceptor Neurons Magnify Host Responses to Aggravate Periodontitis

Periodontitis is a highly prevalent chronic inflammatory disease that progressively destroys the structures supporting teeth, leading to tooth loss. Periodontal tissue is innervated by abundant pain-sensing primary afferents expressing neuropeptides and transient receptor potential vanilloid 1 (TRPV1). However, the roles of nociceptive nerves in periodontitis and bone destruction are controversial. The placement of ligature around the maxillary second molar or the oral inoculation of pathogenic bacteria induced alveolar bone destruction in mice. Chemical ablation of nociceptive neurons in the trigeminal ganglia achieved by intraganglionic injection of resiniferatoxin decreased bone loss in mouse models of experimental periodontitis. Consistently, ablation of nociceptive neurons decreased the number of osteoclasts in alveolar bone under periodontitis. The roles of nociceptors were also determined by the functional inhibition of TRPV1-expressing trigeminal afferents using an inhibitory designer receptor exclusively activated by designer drugs (DREADD) receptor. Noninvasive chemogenetic functional silencing of TRPV1-expressing trigeminal afferents not only decreased induction but also reduced the progression of bone loss in periodontitis. The infiltration of leukocytes and neutrophils to the periodontium increased at the site of ligature, which was accompanied by increased amount of proinflammatory cytokines, such as receptor activator of nuclear factor κΒ ligand, tumor necrosis factor, and interleukin 1β. The extents of increase in immune cell infiltration and cytokines were significantly lower in mice with nociceptor ablation. In contrast, the ablation of nociceptors did not alter the periodontal microbiome under the conditions of control and periodontitis. Altogether, these results indicate that TRPV1-expressing afferents increase bone destruction in periodontitis by promoting hyperactive host responses in the periodontium. We suggest that specific targeting of neuroimmune and neuroskeletal regulation can offer promising therapeutic targets for periodontitis supplementing conventional treatments.

Immunoporosis: Role of immune system in the pathophysiology of different types of osteoporosis

Osteoporosis is a skeletal system disease characterized by low bone mass and altered bone microarchitecture, with an increased risk of fractures. Classical theories hold that osteoporosis is essentially a bone remodeling disorder caused by estrogen deficiency/aging (primary osteoporosis) or secondary to diseases/drugs (secondary osteoporosis). However, with the in-depth understanding of the intricate nexus between both bone and the immune system in recent decades, the novel field of "Immunoporosis" was proposed by Srivastava et al. (2018, 2022), which delineated and characterized the growing importance of immune cells in osteoporosis. This review aimed to summarize the response of the immune system (immune cells and inflammatory factors) in different types of osteoporosis. In postmenopausal osteoporosis, estrogen deficiency-mediated alteration of immune cells stimulates the activation of osteoclasts in varying degrees. In senile osteoporosis, aging contributes to continuous activation of the immune system at a low level which breaks immune balance, ultimately resulting in bone loss. Further in diabetic osteoporosis, insulin deficiency or resistance-induced hyperglycemia could lead to abnormal regulation of the immune cells, with excessive production of proinflammatory factors, resulting in osteoporosis. Thus, we reviewed the pathophysiology of osteoporosis from a novel insight-immunoporosis, which is expected to provide a specific therapeutic target for different types of osteoporosis.

Immune Checkpoint Inhibitor Therapy for Bone Metastases: Specific Microenvironment and Current Situation

The treatment of bone metastases is a thorny issue. Immunotherapy may be one of the few hopes for patients with unresectable bone metastases. Immune checkpoint inhibitors are the most commonly used immunotherapy drugs currently. In this review, the characteristics and interaction of bone metastases and their immune microenvironment were systematically discussed, and the relevant research progress of the immunological mechanism of tumor bone metastasis was reviewed. On this basis, we expounded the clinical application of immune checkpoint inhibitors for bone metastasis of common tumors, including non-small-cell lung cancer, renal cell carcinoma, prostate cancer, melanoma, and breast cancer. Then, the deficiencies and limitations in current researches were summarized. In-depth basic research on bone metastases and optimization of clinical treatment is needed.

Loss of Neutrophil Homing to the Periodontal Tissues Modulates the Composition and Disease Potential of the Oral Microbiota

Periodontal disease is considered to arise from an imbalance in the interplay between the host and its commensal microbiota, characterized by inflammation, destructive periodontal bone loss, and a dysbiotic oral microbial community. The neutrophil is a key component of defense of the periodontium: defects in their number or efficacy of function predisposes individuals to development of periodontal disease. Paradoxically, neutrophil activity, as part of a deregulated inflammatory response, is considered an important element in the destructive disease process. In this investigation, we examined the role the neutrophil plays in the regulation of the oral microbiota by analysis of the microbiome composition in mice lacking the CXCR2 neutrophil receptor required for recruitment to the periodontal tissues. A breeding protocol was employed that ensured that only the oral microbiota of wild-type (CXCR2^+/+) mice was transferred to subsequent generations of wild-type, heterozygote, and homozygote littermates. In the absence of neutrophils, the microbiome undergoes a significant shift in total load and composition compared to when normal levels of neutrophil recruitment into the gingival tissues occur, and this is accompanied by a significant increase in periodontal bone pathology. However, transfer of the oral microbiome of CXCR2^-/- mice into germfree CXCR2^+/+ mice led to restoration of the microbiome to the wild-type CXCR2^+/+ composition and the absence of pathology. These data demonstrate that the composition of the oral microbiome is inherently flexible and is governed to a significant extent by the genetics and resultant phenotype of the host organism.

The psychobiological links between chronic stress-related diseases, periodontal/peri-implant diseases, and wound healing

Chronic stress is a relevant disease to periodontal practice, encompassing 25%-28% of the US population (American Psychological Association 2015). While it is well established that chronic psychologic stress can have significant deleterious systemic effects, only in recent decades have we begun to explore the biochemical, microbial, and physiologic impacts of chronic stress diseases on oral tissues. Currently, chronic stress is classified as a "risk indicator" for periodontal disease. However, as the evidence in this field matures with additional clinically controlled trials, more homogeneous data collection methods, and a better grasp of the biologic underpinnings of stress-mediated dysbiosis, emerging evidence suggests that chronic stress and related diseases (depression, anxiety) may be significant contributing factors in periodontal/peri-implant disease progression and inconsistent wound healing following periodontal-related therapeutics. Ideal solutions for these patients include classification of the disease process and de-escalation of chronic stress conditions through coping strategies. This paper also summarizes periodontal/implant-related therapeutic approaches to ensure predictable results for this specific patient subpopulation.

Immunoporosis: Role of Innate Immune Cells in Osteoporosis

Osteoporosis or porous bone disorder is the result of an imbalance in an otherwise highly balanced physiological process known as 'bone remodeling'. The immune system is intricately involved in bone physiology as well as pathologies. Inflammatory diseases are often correlated with osteoporosis. Inflammatory mediators such as reactive oxygen species (ROS), and pro-inflammatory cytokines and chemokines directly or indirectly act on the bone cells and play a role in the pathogenesis of osteoporosis. Recently, Srivastava et al. (Srivastava RK, Dar HY, Mishra PK. Immunoporosis: Immunology of Osteoporosis-Role of T Cells. Frontiers in immunology. 2018;9:657) have coined the term "immunoporosis" to emphasize the role of immune cells in the pathology of osteoporosis. Accumulated pieces of evidence suggest both innate and adaptive immune cells contribute to osteoporosis. However, innate cells are the major effectors of inflammation. They sense various triggers to inflammation such as pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), cellular stress, etc., thus producing pro-inflammatory mediators that play a critical role in the pathogenesis of osteoporosis. In this review, we have discussed the role of the innate immune cells in great detail and divided these cells into different sections in a systemic manner. In the beginning, we talked about cells of the myeloid lineage, including macrophages, monocytes, and dendritic cells. This group of cells explicitly influences the skeletal system by the action of production of pro-inflammatory cytokines and can transdifferentiate into osteoclast. Other cells of the myeloid lineage, such as neutrophils, eosinophils, and mast cells, largely impact osteoporosis via the production of pro-inflammatory cytokines. Further, we talked about the cells of the lymphoid lineage, including natural killer cells and innate lymphoid cells, which share innate-like properties and play a role in osteoporosis. In addition to various innate immune cells, we also discussed the impact of classical pro-inflammatory cytokines on osteoporosis. We also highlighted the studies regarding the impact of physiological and metabolic changes in the body, which results in chronic inflammatory conditions such as ageing, ultimately triggering osteoporosis.

Modulating immune microenvironment during bone repair using biomaterials: Focusing on the role of macrophages

Bone is a self-regenerative tissue that can repair small defects and fractures. In large defects, bone tissue is unable to provide nutrients and oxygen for repair, and autologous grafting is used as the gold standard. As an alternative method, the bone tissue regeneration approach uses osteoconductive biomaterials to overcome bone graft disadvantages. However, biomaterials are considered as foreign components that can stimulate host immune responses. Although traditional principles have been aimed to minimize immune reactions, the design of biomaterials has steadily shifted toward creating an immunomodulatory microenvironment to harness immune cells and responses to repair damaged tissue. Among immune cells, macrophages secrete various immunomodulatory mediators and crosstalk with bone-forming cells and play key roles in bone tissue engineering. Macrophage polarization toward M1 and M2 subtypes mediate pro-inflammatory and anti-inflammatory responses, respectively, which are crucial for bone repairing at different stages. This review provides an overview of the crosstalk between various immune cells and biomaterials, macrophage polarization, and the effect of physicochemical properties of biomaterials on the immune responses, especially macrophages, in bone tissue engineering.

Effects of curcumin gel on osteoclastogenic bone markers in experimental periodontitis and alveolar bone loss in wistar rats

BACKGROUND/PURPOSE

Curcumin has anti-inflammatory impacts and was suggested as an inflammatory disease therapy. This study aimed to investigate the implications of curcumin gel on experimental periodontitis (EPD) and alveolar bone loss in rats.

MATERIALS AND METHODS

In this study, twenty-four male Wistar rats were divided equally into four groups: negative control (with no EPD); positive control (EPD induced around lower centrals without treatment); control-treated group: EPD treated with chlorhexidine; and test EPD group treated with curcumin. After 30 days, the serum concentrations of RANKL and IL-1β were measured via ELISA. All animals were sacrificed, and mandibular central incisors with the periodontium were removed. The lingual probing depth and radiographical alveolar bone loss were measured, then samples processed for routine preparation of H&E stained sections and histologically assessed for counting inflammatory cells, osteoclasts, and PDL width.

RESULTS

A significant decrease in the inflammatory cells infiltration, probing depth, and osteoclast numbers with the improvement of PDL associated with a reduction in RANKL and IL-1β serum concentration were seen in both EPD treated groups.

CONCLUSION

Curcumin is as effective as chlorhexidine in treating experimental periodontitis in rats. It was demonstrated to stop bone destruction related to periodontitis by regulating the RANKL and IL-1β markers level in the blood.

Inverse association between systemic immune-inflammation index and bone mineral density in postmenopausal women

OBJECTIVE

The aim of the present study was to investigate whether systemic immune-inflammation index (SII) and neutrophil-to-platelet ratio (NLR) were associated with bone mineral density (BMD) in postmenopausal women.

METHODS

In this cross-sectional study, we enrolled 413 postmenopausal women who never received menopause hormone therapy. The relationship between SII, NLR, and BMD was investigated by linear regression analysis.

RESULTS

Significant inverse association was observed between SII and BMD in postmenopausal women. The mean BMD in each quartile of SII level were 0.923, 0.914, 0.900, and 0.876 g/cm², respectively (p = .011). After adjusting for covariates, SII levels remained significantly associated with BMD (regression coefficients for quartiles 1-3 vs. quartile 4 were 0.035, 0.029, and 0.023, respectively; p for trend <.05). An inverse association was also found between NLR and BMD in postmenopausal women. However, there was no significant association between NLR and BMD after adjusting for covariates.

CONCLUSION

The quartile of SII was negatively associated with the mean BMD in postmenopausal women, independent of age, body mass index, sex hormone levels, and other factors. Therefore, SII can be used as a new predictor of bone loss in postmenopausal women.

Investigation of Intravenous Zoledronic Acid Therapy on Circulating Lymphocyte Subpopulation in Patients with Primary Osteoporosis: A Pilot Study

BACKGROUND

Several studies have investigated the immunomodulating properties of zoledronic acid on T lymphocytes, but the causal relationship between the function of T cells and the efficacy of zoledronic acid has not been elucidated.

OBJECTIVE

To investigate the causal relationship between the function of zoledronic acid and T cells.

METHODS

We conducted an observational perspective study to observe the effect of intravenous zoledronic acid once yearly for 2 years on lymphocyte subsets in patients with primary osteoporosis through observing the blood cells analysis and the level of lymphocyte subpopulations before and on day 1, 2, and 3 after first and second administration of intravenous zoledronic acid and bone mineral destiny 1 year after a single administration of zoledronic acid.

RESULTS

White blood cell count and neutrophils increased, whereas lymphocytes and eosinophils decreased after the first and second zoledronic acid infusion. The count of CD3+T cells, CD3+CD4+T cells, and CD16+CD56+ natural killer lymphocytes decreased from day 1 to day 3 after the first and second zoledronic acid infusion, but the results of second infusion showed no significance.

CONCLUSIONS

Further, larger size, more in-depth studies are indicated to examine whether the short-term changes in white blood cells and lymphocyte subtypes noted after 2 once-yearly zoledronic acid injections in this small population of adult patients is associated with the stimulation of immune mechanisms. (Curr Ther Res Clin Exp. 2021; 82:XXX-XXX).

Periodontal status in children with primary immunodeficiencies

OBJECTIVE

This study aimed to assess associations between neutrophil-related primary immunodeficiencies (PIDs) and the presence of periodontal disease and other oral diseases and response to periodontal treatment.

BACKGROUND

Presence of neutrophil-related PIDs is thought to be a major risk factor for development of periodontitis.

METHODS

This study had both a cross-sectional and cohort design. Twenty-four children (age 4-16) with PIDs and 24 age-matched systemically healthy subjects received a dental clinical examination, including measures of probing pocket depths (PPD), clinical attachment loss (CAL) and bleeding on probing (BOP). Those found to be affected by periodontal disease were offered periodontal treatment and reassessed 6 months later.

RESULTS

Diagnosis of PIDs was associated with increased odds of presence of periodontal disease (p = .008 adjusted for age, gender, plaque, OR = 10.0, 95% CI = 1.83-54.38) and with continuous measures of periodontal disease such as number of PPDs >4 mm, mean PPD and mean CAL (all p < .001) and BOP (p = .001). However, only 7 out of 24 children were diagnosed with periodontitis. PIDs were also associated with a history of oral ulcers (p = .001, OR 12.47, 95% CI 2.71-57.29). An improvement in periodontal parameters (PPD and CAL) was detected following oral hygiene instructions and non-surgical periodontal therapy.

CONCLUSION

Although children affected by neutrophil-associated PIDs exhibited a higher prevalence of periodontal disease compared with systemically healthy children, severe periodontitis was rarely seen. This suggests that good systemic control of the PIDs may reduce their impact on the periodontium.

Cross-Talk among Polymorphonuclear Neutrophils, Immune, and Non-Immune Cells via Released Cytokines, Granule Proteins, Microvesicles, and Neutrophil Extracellular Trap Formation: A Novel Concept of Biology and Pathobiology for Neutrophils

Polymorphonuclear neutrophils (PMNs) are traditionally regarded as professional phagocytic and acute inflammatory cells that engulf the microbial pathogens. However, accumulating data have suggested that PMNs are multi-potential cells exhibiting many important biological functions in addition to phagocytosis. These newly found novel activities of PMN include production of different kinds of cytokines/chemokines/growth factors, release of neutrophil extracellular traps (NET)/ectosomes/exosomes and trogocytosis (membrane exchange) with neighboring cells for modulating innate, and adaptive immune responses. Besides, PMNs exhibit potential heterogeneity and plasticity in involving antibody-dependent cellular cytotoxicity (ADCC), cancer immunity, autoimmunity, inflammatory rheumatic diseases, and cardiovascular diseases. Interestingly, PMNs may also play a role in ameliorating inflammatory reaction and wound healing by a subset of PMN myeloid-derived suppressor cells (PMN-MDSC). Furthermore, PMNs can interact with other non-immune cells including platelets, epithelial and endothelial cells to link hemostasis, mucosal inflammation, and atherogenesis. The release of low-density granulocytes (LDG) from bone marrow initiates systemic autoimmune reaction in systemic lupus erythematosus (SLE). In clinical application, identification of certain PMN phenotypes may become prognostic factors for severe traumatic patients. In the present review, we will discuss these newly discovered biological and pathobiological functions of the PMNs.

Natural Killer-Like B Cells Secreting Interleukin-18 Induces a Proinflammatory Response in Periodontitis

Natural killer-like B (NKB) cells, which are newly identified immune subsets, reveal a critical immunoregulatory property in the eradication of microbial infection via the secretion of interleukin (IL)-18. For the first time, this study investigated the role of NKB cells in secreting IL-18 in the pathogenesis of periodontitis. In this study, NKB cells' percentage and IL-18 concentration in peripheral blood and periodontium in periodontitis patients was measured using flow cytometry and ELISA. The role of IL-18 in regulating periodontal inflammation was examined in a Porphyromonas gingivalis (P. gingivalis)-induced periodontitis murine model. Peripheral and periodontal-infiltrating CD3^-CD19⁺NKp46⁺ NKB cells, which were the main source of IL-18, were elevated and correlated with attachment loss in periodontitis patients. In vitro IL-18 stimulation promoted proinflammatory cytokine production in periodontal ligament cells. P. gingivalis infection induced elevation of IL-18 receptor in periodontium in a periodontitis murine model. IL-18 neutralization not only suppressed P. gingivalis-induced alveolar bone resorption, but also inhibited recruitment of antigen-non-specific inflammatory cells into the periodontium, probably via dampening expressions of cytokines, chemokines, and matrix metalloproteinases. NKB cells secreting IL-18 appeared to be an important mediator in the inflammatory response following intraoral P. gingivalis infection. These findings might be relevant to the development of immunotherapies for periodontitis.

Advances in mesenchymal stem cell transplantation for the treatment of osteoporosis

Osteoporosis is a systemic metabolic bone disease with characteristics of bone loss and microstructural degeneration. The personal and societal costs of osteoporosis are increasing year by year as the ageing of population, posing challenges to public health care. Homing disorders, impaired capability of osteogenic differentiation, senescence of mesenchymal stem cells (MSCs), an imbalanced microenvironment, and disordered immunoregulation play important roles during the pathogenesis of osteoporosis. The MSC transplantation promises to increase osteoblast differentiation and block osteoclast activation, and to rebalance bone formation and resorption. Preclinical investigations on MSC transplantation in the osteoporosis treatment provide evidences of enhancing osteogenic differentiation, increasing bone mineral density, and halting the deterioration of osteoporosis. Meanwhile, the latest techniques, such as gene modification, targeted modification and co-transplantation, are promising approaches to enhance the therapeutic effect and efficacy of MSCs. In addition, clinical trials of MSC therapy to treat osteoporosis are underway, which will fill the gap of clinical data. Although MSCs tend to be effective to treat osteoporosis, the urgent issues of safety, transplant efficiency and standardization of the manufacturing process have to be settled. Moreover, a comprehensive evaluation of clinical trials, including safety and efficacy, is still needed as an important basis for clinical translation.

Periodontal Pathogens' strategies disarm neutrophils to promote dysregulated inflammation

Periodontitis is an irreversible, chronic inflammatory disease where inflammophilic pathogenic microbial communities accumulate in the gingival crevice. Neutrophils are a major component of the innate host response against bacterial challenge, and under homeostatic conditions, their microbicidal functions typically protect the host against periodontitis. However, a number of periodontal pathogens developed survival strategies to evade neutrophil microbicidal functions while promoting inflammation, which provides a source of nutrients for bacterial growth. Research on periodontal pathogens has largely focused on a few established species: Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis. However, advances in culture-independent techniques have facilitated the identification of new bacterial species in periodontal lesions, such as the two Gram-positive anaerobes, Filifactor alocis and Peptoanaerobacter stomatis, whose characterization of pathogenic potential has not been fully described. Additionally, there is not a full understanding of the pathogenic mechanisms used against neutrophils by organisms that are abundant in periodontal lesions. This presents a substantial barrier to the development of new approaches to prevent or ameliorate the disease. In this review, we first summarize the neutrophil functions affected by the established periodontal pathogens listed above, denoting unknown areas that still merit a closer look. Then, we review the literature on neutrophil functions and the emerging periodontal pathogens, F. alocis and P. stomatis, comparing the effects of the emerging microbes to that of established pathogens, and speculate on the contribution of these putative pathogens to the progression of periodontal disease.

Biocultural pathways linking periodontal disease expression to food insecurity, immune dysregulation, and nutrition

OBJECTIVES

In this article, we test theoretical pathways leading to and resulting from periodontal disease to better understand how periodontal disease, which is measurable in both past and present populations, integrates biocultural context and affects whole-body physiology.

METHODS

We use data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and logistic and linear regressions to test pathways linking psychosocial stress to periodontal disease, and periodontal disease to serum vitamin C levels. We then use causal mediation analysis to test the role of mediating variables in these pathways (n = 1853 individuals).

RESULTS

Food insecurity was positively associated with periodontal disease and negatively associated with serum counts of C-reactive protein (CRP) and neutrophils. Neither CRP nor neutrophils significantly mediated the relationship between food insecurity and periodontal disease. Periodontal disease was negatively associated with serum vitamin C levels and positively associated with neutrophil counts. Neutrophils may mediate the relationship between periodontal disease and vitamin C.

CONCLUSIONS

We identify two main findings: (a) periodontal disease contributes to and may result from immune dysregulation, particularly of neutrophils, and (b) an immune response to chronic infection such as periodontal disease is metabolically expensive for the body to maintain and likely depletes serum micronutrient levels. Both micronutrient status and serum neutrophil counts affect multiple skeletal and physiological phenotypes and thus position periodontal disease in whole-body context.

NETs Are Double-Edged Swords with the Potential to Aggravate or Resolve Periodontal Inflammation

Periodontitis is a general term for diseases characterised by inflammatory destruction of tooth-supporting tissues, gradual destruction of the marginal periodontal ligament and resorption of alveolar bone. Early-onset periodontitis is due to disturbed neutrophil extracellular trap (NET) formation and clearance. Indeed, mutations that inactivate the cysteine proteases cathepsin C result in the massive periodontal damage seen in patients with deficient NET formation. In contrast, exaggerated NET formation due to polymorphonuclear neutrophil (PMN) hyper-responsiveness drives the pathology of late-onset periodontitis by damaging and ulcerating the gingival epithelium and retarding epithelial healing. Despite the gingival regeneration, periodontitis progression ends with almost complete loss of the periodontal ligament and subsequent tooth loss. Thus, NETs help to maintain periodontal health, and their dysregulation, either insufficiency or surplus, causes heavy periodontal pathology and edentulism.

Targeted pharmacologic immunomodulation for inborn errors of immunity

Inborn errors of immunity consist of over 400 known single gene disorders that may manifest with infection susceptibility, autoimmunity, autoinflammation, hypersensitivity and cancer predisposition. Most patients are treated symptomatically with immunoglobulin replacement, prophylactic antimicrobials or broad immunosuppression pertaining to their disease phenotype. Other than haematopoietic stem cell transplantation, the aforementioned treatments do little to alter disease morbidity or mortality. Further, many patients may not be transplant candidates. In this review, we describe monogenic disorders affecting leucocyte migration, disorders of immune synapse formation and dysregulation of immune cell signal transduction. We highlight the use of off-label small molecules and biologics mechanistically targeted to altered disease pathophysiology of such diseases.