Characterization of the Protective Role of Regulatory T Cells in Experimental Periapical Lesion Development and Their Chemoattraction Manipulation as a Therapeutic Tool

Systemic administration of propranolol reduces bone resorption and inflammation in apical periodontitis of chronically stressed rats

AIM

To evaluate the effect of systemic administration of propranolol on the severity of apical periodontitis (AP) in chronically stressed rats.

METHODOLOGY

Twenty-four 70-day-old male Wistar rats (Rattus norvegicus, albinus) were distributed into three groups (n = 8): rats with AP without stressful conditions (AP-Control), rats with AP and submitted to a chronic unpredictable stress (CUS) protocol (AP + S) and rats with AP and submitted to a CUS protocol treated with propranolol (AP + S + PRO). Stress procedures were applied daily until the end of the experiment. After 3 weeks of CUS, AP was induced in all groups by exposing the pulpal tissue of mandibular and maxillary first molars to the oral environment. Propranolol treatment was administered orally once a day for the entire period of the experiment. Rats were sacrificed at 42 days, and the blood was collected for stress biomarkers serum dosage by multiplex assay. Mandibles were removed and submitted to microtomography and histopathological analyses. Periapical tissue surrounding the upper first molar was homogenized and subjected to RT-PCR analysis to evaluate the mRNA expression of RANKL, TRAP and OPG. Parametric data were assessed using one-way ANOVA followed by Tukey's test while the nonparametric data were analysed by the Kruskal-Wallis followed by Dunn's test. Significance level was set at 5% (p < .05) for all assessed parameters.

RESULTS

Micro-CT revealed statistically significant differences in bone resorption which was greater in the AP + S group (p < .05), but no differences were observed between the Control and AP + S + PRO groups (p > .05). The AP + S + PRO group had a lower intensity and extent of inflammatory infiltrate compared to the AP + S group with smaller areas of bone loss (p < 0.05). The gene expression of RANKL and TRAP was significantly higher in the stressed group AP + S compared to the control group (p < .05), and a significantly higher OPG expression was observed in AP + S + PRO compared to the AP + S group (p < .05).

CONCLUSIONS

Oral administration of propranolol had a significant effect on the AP severity in stressed rats, suggesting an anti-inflammatory effect and a protective role on bone resorption of AP in stressed animals. Further research is necessary to fully comprehend the underlying mechanisms.

Is there any association between the presence of biomarkers and apical periodontitis? A systematic review

This systematic review aimed to verify whether there is evidence of an association between apical periodontitis and the presence of systemic biomarkers. This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - PRISMA. For this, the acronym PECO was used; population (P) of adult humans exposed (E) to the presence of apical periodontitis, compared (C) to adult humans without apical periodontitis, and the outcome (O) of the presence of biomarkers was observed. The articles were searched in PubMed, Scopus, Web of Science, LILACS, Cochrane Library, OpenGray, and Google Scholar grey databases. Subsequently, studies were excluded based on title, abstract, and full article reading, following the eligibility criteria. The methodological quality of the selected studies was evaluated using the Newcastle-Ottawa qualifier. After exclusion, 656 studies were identified, resulting in 17 final articles that were divided into case-control, cross-sectional, and cohort studies. Eight studies were considered to have a low risk of bias, one had a medium risk of bias, and eight had a high risk of bias. In addition, 12 articles evaluated biomarkers in blood plasma, four evaluated them in saliva, and only one evaluated them in gingival crevicular fluid. The results of these studies indicated an association between apical periodontitis and the systemic presence of biomarkers. These markers are mainly related to inflammation, such as interleukins IL-1, IL-2, and IL-6, oxidative markers, such as nitric oxide and superoxide anions, and immunoglobulins IgG and IgM.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42023493959).

TLR2 agonist prevents the progression of periapical lesions in mice by reducing osteoclast activity and regulating the frequency of Tregs

AIM

To evaluate the role of regulatory T lymphocytes (Tregs) in the presence or absence of the synthetic ligand Pam3Cys during the progression of periapical lesion in wild-type (WT) and toll-like receptor 2 knockout (TLR2KO) mice.

METHODOLOGY

A total of 130 C57BL/6 male WT and TLR2KO mice were allocated into control (n = 5) and experimental (periapical lesion induction) (n = 10) groups. In specific groups (WT+Pam3cys and TLR2KO+Pam3cys), the synthetic ligand Pam3cys was administered intraperitoneally every 7 days, according to the experimental period (14, 21 and 42 days). At the end of those periods, the animals were euthanized, and the mandible and the spleen were submitted to histotechnical processing. Mandible histological sections were analysed by haematoxylin and eosin, TRAP histoenzymology and immunohistochemistry (FOXP3, RANK, RANKL and OPG). Spleen sections were analysed by immunohistochemistry (FOXP3).

RESULTS

The inflammatory infiltrate and bone resorption were more intense in the TLR2KO group compared to the WT group. The animals that received the Pam3cys had smaller periapical lesions when compared to the animals that did not receive the ligand (p < .05). TLR2KO animals showed a significant increase in the number of osteoclasts when compared to TLR2KO+Pam3cys group (p < .05). At 21 days, the WT+Pam3cys group had a lower number of osteoclasts when compared to the WT animals (p = .02). FOXP3 expression was more intense in the WT+Pam3cys groups when compared to the WT animals in the 42 days (p = .03). In the spleen analysis, the WT+Pam3cys group also had a higher expression of FOXP3 when compared to the WT animals at 14 and 42 days (p = .02). Concerning RANKL, there was a reduction in staining in the KOTLR2+Pam3cys groups at 21 and 42 days (p = .03) and a higher binding ratio between RANK/RANKL in animals that did not receive the ligand.

CONCLUSION

Administration of the Pam3cys increased the proliferation of Tregs, showed by FOXP3 expression and prevented the progression of the periapical lesion in WT mice. On the other hand, in the TLR2KO animals, Treg expression was lower with larger areas of periapical lesions. Finally, systemic administration of the Pam3cys in KO animals was able to limit the deleterious effects of the absence of the TLR2 receptor.

Heterogeneity of T cells in periapical lesions and in vitro validation of the proangiogenic effect of GZMA on HUVECs

AIM

T cells are key immunomodulatory cells in periapical lesions. This study aimed to explore the roles of T cells in chronic apical periodontitis (CAP) using single-cell RNA sequencing and to further investigate Granzyme A (GZMA) in angiogenesis regulation.

METHODOLOGY

A total of five CAP samples were collected for single-cell RNA sequencing. We performed subcluster and lineage-tracing analyses for T cells. According to differential gene expression, distinct biological functions enriched in T cells of CAP were presented by gene set enrichment analysis (GSEA) and compared with healthy gingiva (data obtained from the GEO database). CellChat was used to explore potential ligand-receptor interactions between T cells and endothelial cells in CAP. The coculture of primary human umbilical vein endothelial cells (HUVECs) and Jurkat T cells, as well as the addition of GZMA recombinant protein, was used to validate the predicted pair of GZMA and coagulation factor II thrombin receptor (F2R) by RT-PCR, angiogenesis and migration assays.

RESULTS

A transcriptomic atlas of 44 746 individual cells was constructed from the periapical lesions of five patients with CAP by single-cell RNA-seq, and eight cell types were identified. We identified nine subsets of T cells and deciphered the cellular heterogeneity of T cells in CAP at the functional level by subclustering and GSEA. Lineage tracing revealed a distinct lineage of T cells in CAP and predicted the transition of the T cellular state upon CAP. GSEA revealed multiple biological processes and relevant angiogenesis genes upregulated in CAP T cells. GZMA-F2R pairs were predicted by cell-cell interactions in CAP. High expression of GZMA and F2R was observed in the coculture of HUVECs and Jurkat T cells, and the proangiogenic capacity of the GZMA recombinant protein was emphasized by in vitro experiments.

CONCLUSIONS

Our study provides novel insights into the heterogeneity of T cells in periapical lesions and reveals the potential role of GZMA in T cells in regulating angiogenesis in HUVECs.

Recent Advances in Apical Periodontitis Treatment: A Narrative Review

Apical periodontitis is an inflammatory response caused by pulp infection. It induces bone resorption in the apical and periapical regions of the tooth. The most conservative approach to treat this condition is nonsurgical endodontic treatment. However, clinical failure has been reported with this approach; thus, alternative procedures are required. This review highlights recent literature regarding advanced approaches for the treatment of apical periodontitis. Various therapies, including biological medications, antioxidants, specialized pro-resolving lipid mediators, and stem cell therapy, have been tested to increase the success rate of treatment for apical periodontitis. Some of these approaches remain in the in vivo phase of research, while others have just entered the translational research phase to validate clinical application. However, a detailed understanding of the molecular mechanisms that occur during development of the immunoinflammatory reaction in apical periodontitis remains unclear. The aim of this review was to summarize advanced approaches for the treatment of apical periodontitis. Further research can confirm the potential of these alternative nonsurgical endodontic treatment approaches.

Adaptive immune response in pathogenesis and treatment of head and neck squamous cell carcinoma: the influence of immunosuppression factors and gender

An obvious trend of the last decade in head and neck squamous cell carcinoma pathogenesis evaluation is awareness of the impact of immune response disorders on disease manifestation. The review presents an analysis of the differences in the type and degree of immunosuppression, as well as treatment response in head and neck squamous cell carcinoma patients in accordance with influencing carcinogenic factor, gender, age of the patient and concomitant diseases. An increase in CD8+ T-lymphocytes and a decrease of memory T-cells has been evaluated in smoking and alcohol abusing patients with head and neck squamous cell carcinoma, and a smaller number of CD8+ T-lymphocytes were detected in the tumor microenvironment compared to non-smoking and non-drinking patients. Studies have shown that the improved prognosis of patients with human papillomavirus (Hpv) – associated head and neck squamous cell carcinoma is largely due to the presence of antibodies against Hpv E6 and E7, E7-specific CD8+T lymphocytes in periphe ral blood and a high level of tumor-infiltrating T lymphocytes. The issue of gender differences in the type of immune response is widely discussed. It has been shown that the use of immune response checkpoint inhibitors is more effective in improving survival rates in men, and the use of these drugs in combination with chemotherapy is more effective in women. In addition, in elderly cancer patients, numerous age-associated T-lymphocyte’s function changes were revealed, including a decrease in the number of naive T-lymphocytes due to age-related involution of the thymus and an in crease in the relative number of memory cells and effector cells. Thus, it is clear that immunosuppression type, as well as treatment response, differ depending on the influencing factor, gender, age of the patient, as well as comorbidities.

Protective Actions in Apical Periodontitis: The Regenerative Bioactivities Led by Mesenchymal Stem Cells

Resulting from bacterial infection, apical periodontitis (AP) is a common inflammatory disease of the periapical region of the tooth. The regeneration of the destroyed periapical alveolar bone and the surrounding periodontium tissues has long been a difficult task in clinical practice. These lesions are closely related to pathogen invasion and an overreactive immune response. It is worth noting that the protective healing process occurs simultaneously, in which mesenchymal stem cells (MSCs) have a crucial function in mediating the immune system and promoting regeneration. Here, we review the recent studies related to AP, with a focus on the regulatory network of MSCs. We also discuss the potential therapeutic approaches of MSCs in inflammatory diseases to provide a basis for promoting tissue regeneration and modulating inflammation in AP. A deeper understanding of the protective action of MSCs and the regulatory networks will help to delineate the underlying mechanisms of AP and pave the way for stem-cell-based regenerative medicine in the future.

Polarization Profiles of T Lymphocytes and Macrophages Responses in Periodontitis

Periodontitis is a multifactorial, chronic inflammatory disease affecting the supporting structures of teeth triggered by the complex interactions between a dysbiotic bacterial biofilm and the host's immune response that results in the characteristic loss of periodontal attachment and alveolar bone. The differential phenotypic presentations of periodontitis emerge from inter-individual differences in immune response regulatory mechanisms. The monocyte-macrophage system has a crucial role in innate immunity and the initiation of the T and B lymphocyte adaptive immune responses. Macrophages involve a heterogeneous cell population that shows wide plasticity and differentiation dynamics. In response to the inflammatory milieu, they can skew at the time of TLR ligation to predominant M1 -pro-inflammatory- or M2 -anti-inflammatory/healing- functional phenotypes. The perpetuation of inflammation by M1 macrophages leads to the recruitment of the adaptive immune response, promoting Th1, Th17, and Th22 differentiation, which are directly associated with periodontal breakdown. In contrast, M2 macrophages induce Th2 and Treg responses which are associated with periodontal homeostasis. In this article, we review the recent advances comprising the role of macrophages and lymphocyte polarization profiles and their reprogramming as potential therapeutic strategies. For this purpose, we reviewed the available literature targeting periodontitis, macrophage, and lymphocyte subpopulations with an emphasis in the later 5 years. The active reprogramming of macrophages and lymphocytes polarization crosstalk opens a promising area for therapeutic development.

Local induction of regulatory T cells prevents inflammatory bone loss in ligature-induced experimental periodontitis in mice

Periodontitis (periodontal disease) is a highly prevalent disease, affecting over 65 million adults in the United States alone. Characterized by an overburden of invasive bacteria, gum inflammation and plaque buildup, over time, these symptoms can result in severe loss of gingival tissue attachment, bone resorption and even tooth loss. Although current treatments (local antibiotics and scaling and root planing procedures) target the bacterial dysbiosis, they do not address the underlying inflammatory imbalance in the periodontium. In the healthy steady state, the body naturally combats destructive, imbalanced inflammatory responses through regulatory pathways mediated by cells such as regulatory T cells (Tregs). Consequently, we hypothesized that local enrichment of regulatory lymphocytes (Tregs) could restore local, immunological homeostasis and prevent the main outcome of bone loss. Accordingly, we locally delivered a combination of TGFβ, Rapamycin, and IL2 microspheres in a ligature-induced murine periodontitis model. Herein, we have demonstrated this preventative treatment decreases alveolar bone loss, increases the local ratio of Tregs to T effector cells and changes the local microenvironment’s expression of inflammatory and regenerative markers. Ultimately, these Treg-inducing microspheres appear promising as a method to improve periodontitis outcomes and may be able to serve as a platform delivery system to treat other inflammatory diseases.

Immune Tolerance in the Oral Mucosa

The oral mucosa is a site of intense immune activity, where a large variety of immune cells meet to provide a first line of defense against pathogenic organisms. Interestingly, the oral mucosa is exposed to a plethora of antigens from food and commensal bacteria that must be tolerated. The mechanisms that enable this tolerance are not yet fully defined. Many works have focused on active immune mechanisms involving dendritic and regulatory T cells. However, epithelial cells also make a major contribution to tolerance by influencing both innate and adaptive immunity. Therefore, the tolerogenic mechanisms concurring in the oral mucosa are intertwined. Here, we review them systematically, paying special attention to the role of oral epithelial cells.

The Potential Roles of T Cells in Periapical Lesions

INTRODUCTION

Periapical lesions are inflammatory diseases mainly caused by microbial infection from the root canal system, affecting the integrity of alveolar bone, periapical cementum, and periodontal ligament. The invasion of pathogenic microorganisms activates local inflammation and host immune response, especially the recruitment and differentiation of T cells. Many studies have discussed the fundamental roles of T cell-related immunological regulation and the possible clinical significance of cytokine disorders in periapical lesions. However, oral pathogen-mediated T cell immune response is far more clarified. Therefore, the aim of this study was to discuss the research status of T cell-related immunology involved in the progression of periapical lesions and potential future directions.

METHODS

We conducted a literature review focusing on T cell-related immunology in periapical lesions by searching PubMed, Web of Science, Scopus and ScienceDirect online databases.

RESULTS

In total 108 articles were involved in this narrative review. During the development of periapical lesions, the infiltrated number of different types of T cells and the secretion of T cell-related cytokines in root apex region reflected the inflammatory status of periapical lesions. In addition, it was also highly correlated with the periapical bone destruction. Future study could attempt to provide a wider and deeper study on the expression profile and regulatory function of T cells in the development of periapical lesions.

CONCLUSION

This review would help us understand the essence of the T cell-related pathology of periapical lesions and raise the potential therapeutic targets for the treatment of apical periodontitis.

VISTA Blockade Aggravates Bone Loss in Experimental Murine Apical Periodontitis

V-domain Ig suppressor of T cell activation (VISTA) is a novel coinhibitory immune checkpoint molecule that maintains immune homeostasis. The present study explored the role of VISTA in human and murine inflammatory tissues of apical periodontitis (AP). VISTA was upregulated in inflammatory tissues of human AP. In mice, the expression of VISTA gradually increased with the development of mouse experimental apical periodontitis (MAP), the CD3+ T cells, CD11b+ myeloid cells, and FOXP3+ regulatory T cells also gradually accumulated. Moreover, a blockade of VISTA using a mouse in vivo anti-VISTA antibody aggravated periapical bone loss and enhanced the infiltration of immune cells in an experimental mouse periapical periodontitis model. The collective results suggest that VISTA serves as a negative regulator of the development and bone loss of apical periodontitis.

Evidence revealing the role of T cell regulators (Tregs) in periodontal diseases: A review

Periodontitis is an inflammatory disease of the periodontium, which is a reflection of the overgrowth of oral commensals. This alteration in the oral microbiota initiates inflammation of the gingiva, which when left untreated, terminates with the resorption of the alveolar bone that may lead to a poor and hopeless prognosis. With upcoming trends in modulating the host's immunity, the role of regulatory T-cells has gained importance. These T-cells defend against inflammation and autoimmunity as they suppress both. However, in both the conditions, the regulatory cells are invariably reduced in number. Novel methods to enhance the function of Tregs have made their way in dentistry, as a promising approach to cure periodontitis. This article discusses various significant tests and trials of Tregs in the recent years.

Treg: A Promising Immunotherapeutic Target in Oral Diseases

With the pandemic of COVID-19, maintenance of oral health has increasingly become the main challenge of global health. Various common oral diseases, such as periodontitis and oral cancer, are closely associated with immune disorders in the oral mucosa. Regulatory T cells (Treg) are essential for maintaining self-tolerance and immunosuppression. During the process of periodontitis and apical periodontitis, two typical chronic immune-inflammatory diseases, Treg contributes to maintain host immune homeostasis and minimize tissue damage. In contrast, in the development of oral precancerous lesions and oral cancer, Treg is expected to be depleted or down-regulated to enhance the anti-tumor immune response. Therefore, a deeper understanding of the distribution, function, and regulatory mechanisms of Treg cells may provide a prospect for the immunotherapy of oral diseases. In this review, we summarize the distribution and multiple roles of Treg in different oral diseases and discuss the possible mechanisms involved in Treg cell regulation, hope to provide a reference for future Treg-targeted immunotherapy in the treatment of oral diseases.

Tuning cytokines enriches dendritic cells and regulatory T cells in the periodontium

BACKGROUND

Periodontal disease results from the pathogenic interactions between the tissue, immune system, and microbiota; however, standard therapy fails to address the cellular mechanism underlying the chronic inflammation. Dendritic cells (DC) are key regulators of T cell fate, and biomaterials that recruit and program DC locally can direct T cell effector responses. We hypothesized that a biomaterial that recruited and programmed DC toward a tolerogenic phenotype could enrich regulatory T cells within periodontal tissue, with the eventual goal of attenuating T cell mediated pathology.

METHODS

The interaction of previously identified factors that could induce tolerance, granulocyte-macrophage colony stimulating factor (GM-CSF) and thymic stromal lymphopoietin (TSLP), with the periodontitis network was confirmed in silico. The effect of the cytokines on DC migration was explored in vitro using time-lapse imaging. Finally, regulatory T cell enrichment in the dermis and periodontal tissue in response to alginate hydrogels delivering TSLP and GM-CSF was examinedin vivo in mice using immunohistochemistry and live-animal imaging.

RESULTS

The GM-CSF and TSLP interactome connects to the periodontitis network. GM-CSF enhances DC migration in vitro. An intradermal injection of an alginate hydrogel releasing GM-CSF enhanced DC numbers and the addition of TSLP enriched FOXP3+ regulatory T cells locally. Injection of a hydrogel with GM-CSF and TSLP into the periodontal tissue in mice increased DC and FOXP3+ cell numbers in the tissue, FOXP3+ cells in the lymph node, and IL-10 in the tissue.

CONCLUSION

Local biomaterial-mediated delivery of GM-CSF and TSLP can enrich DC and FOXP3+ cells and holds promise for treating the pathologic inflammation of periodontal disease.

Determinants of Periodontal/Periapical Lesion Stability and Progression

Periodontal and periapical lesions are infectious inflammatory osteolitytic conditions in which a complex inflammatory immune response mediates bone destruction. However, the uncertainty of a lesion's progressive or stable phenotype complicates understanding of the cellular and molecular mechanisms triggering lesion activity. Evidence from clinical and preclinical studies of both periodontal and periapical lesions points to a high receptor activator of NF-κB ligand/osteoprotegerin (RANKL/OPG) ratio as the primary determinant of osteolytic activity, while a low RANKL/OPG ratio is often observed in inactive lesions. Proinflammatory cytokines directly modulate RANKL/OPG expression and consequently drive lesion progression, along with pro-osteoclastogenic support provided by Th1, Th17, and B cells. Conversely, the cooperative action between Th2 and Tregs subsets creates an anti-inflammatory and proreparative milieu associated with lesion stability. Interestingly, the trigger for lesion status switch from active to inactive can originate from an unanticipated RANKL immunoregulatory feedback, involving the induction of Tregs and a host response outcome with immunological tolerance features. In this context, dendritic cells (DCs) appear as potential determinants of host response switch, since RANKL imprint a tolerogenic phenotype in DCs, described to be involved in both Tregs and immunological tolerance generation. The tolerance state systemically and locally suppresses the development of exacerbated and pathogenic responses and contributes to lesions stability. However, immunological tolerance break by comorbidities or dysbiosis could explain lesions relapse toward activity. Therefore, this article will provide a critical review of the current knowledge concerning periodontal and periapical lesions activity and the underlying molecular mechanisms associated with the host response. Further studies are required to unravel the role of immunological responsiveness or tolerance in the determination of lesion status, as well as the potential cooperative and/or inhibitory interplay among effector cells and their impact on RANKL/OPG balance and lesion outcome.

An update of knowledge on the regulatory role of Treg cells in apical periodontitis

Apical periodontitis (AP) is a prevalent infectious and inflammatory disorder that involves inflammation of periapical tissues and the disintegration of alveolar bone. AP may eventually lead to tooth loss if not timely treated. This disease is caused by pathogenic bacteria in the necrotic pulps and root canals, thereby triggering responses from the innate and adaptive immune system of the periapical tissues. Regulatory T (Treg) cells play a major role in maintaining immune homoeostasis and immunological self-tolerance; however, these only account for roughly 5%-10% of human peripheral CD4⁺ T cells. Several studies have examined the possible role and underlying mechanism of Treg cells in different inflammatory and autoimmune disorders to facilitate the development of novel treatments for these diseases. Recent studies have indicated that Treg cells may gather at the sites of infection, thus limiting the generation of immune responses and bone resorption in the periapical area. This review will summarize studies regarding the presence and regulatory role of Treg cells in AP.

Vasoactive Intestinal Peptide Immunoregulatory Role at the Periapex: Associative and Mechanistic Evidences from Human and Experimental Periapical Lesions

INTRODUCTION

The balance between the host proinflammatory immune response and the counteracting anti-inflammatory and reparative responses supposedly determine the outcome of periapical lesions. In this scenario, the vasoactive intestinal peptide (VIP) may exert a protective role because of its prominent immunoregulatory capacity. In this study, we investigated (in a cause-and-effect manner) the potential involvement of VIP in the development of human and experimental periapical lesions.

METHODS

Periapical granulomas (n = 124) and control samples (n = 48) were comparatively assessed for VIP and multiple immunologic/activity marker expression through real-time polymerase chain reaction. Experimental periapical lesions (C57Bl/6 wild-type mice) were evaluated regarding endogenous VIP expression correlation with lesion development and the effect of recombinant VIP therapy in lesion outcome. CCR4KO and IL4KO strains and anti-glucocorticoid-induced TNFR-related protein inhibition were used to test the involvement of Treg and Th2 cells in VIP-mediated effects.

RESULTS

VIP expression was more prevalent in periapical granulomas than in controls, presenting a positive association with immunoregulatory factors and an inverse association/correlation with proinflammatory mediators and the receptor activator of nuclear factor kappa B ligand/osteoprotegerin ratio. Endogenous VIP expression up-regulation was temporally associated with lesion immunoregulation and a decline of bone loss. VIP therapy in mice prompted the arrest of lesion development, being associated with an anti-inflammatory and proreparative response that limits the proinflammatory, Th1, Th17, and osteoclastogenic response in the periapex. The VIP protective effect was dependent of Treg migration and activity and independent of interleukin 4.

CONCLUSIONS

Our results show that VIP overexpression in human and experimental periapical lesions is associated with lesion inactivity and that VIP therapy results in the attenuation of experimental lesion progression associated with the immunosuppressive response involving Treg cells.

Osteoimmunology of Oral and Maxillofacial Diseases: Translational Applications Based on Biological Mechanisms

The maxillofacial skeleton is highly dynamic and requires a constant equilibrium between the bone resorption and bone formation. The field of osteoimmunology explores the interactions between bone metabolism and the immune response, providing a context to study the complex cellular and molecular networks involved in oro-maxillofacial osteolytic diseases. In this review, we present a framework for understanding the potential mechanisms underlying the immuno-pathobiology in etiologically-diverse diseases that affect the oral and maxillofacial region and share bone destruction as their common clinical outcome. These otherwise different pathologies share similar inflammatory pathways mediated by central cellular players, such as macrophages, T and B cells, that promote the differentiation and activation of osteoclasts, ineffective or insufficient bone apposition by osteoblasts, and the continuous production of osteoclastogenic signals by immune and local stromal cells. We also present the potential translational applications of this knowledge based on the biological mechanisms involved in the inflammation-induced bone destruction. Such applications can be the development of immune-based therapies that promote bone healing/regeneration, the identification of host-derived inflammatory/collagenolytic biomarkers as diagnostics tools, the assessment of links between oral and systemic diseases; and the characterization of genetic polymorphisms in immune or bone-related genes that will help diagnosis of susceptible individuals.

Engineering immunomodulatory biomaterials for type 1 diabetes

A cure for type 1 diabetes (T1D) would help millions of people worldwide, but remains elusive thus far. Tolerogenic vaccines and beta cell replacement therapy are complementary therapies that seek to address aberrant T1D autoimmune attack and subsequent beta cell loss. However, both approaches require some form of systematic immunosuppression, imparting risks to the patient. Biomaterials-based tools enable localized and targeted immunomodulation, and biomaterial properties can be designed and combined with immunomodulatory agents to locally instruct specific immune responses. In this Review, we discuss immunomodulatory biomaterial platforms for the development of T1D tolerogenic vaccines and beta cell replacement devices. We investigate nano- and microparticles for the delivery of tolerogenic agents and autoantigens, and as artificial antigen presenting cells, and highlight how bulk biomaterials can be used to provide immune tolerance. We examine biomaterials for drug delivery and as immunoisolation devices for cell therapy and islet transplantation, and explore synergies with other fields for the development of new T1D treatment strategies.

Inflammatory profile of chronic apical periodontitis: a literature review

Apical periodontitis caused by root canal infection is the most frequent pathological lesion in the jaws, mainly manifested as periapical granulomas and cysts. Understanding of the formation and progression of apical periodontitis as well as the identification of inflammatory biomarkers can help increase the knowledge of pathogenic mechanisms, improve the diagnosis and provide support for different therapeutic strategies. The objective of the present article is to review inflammatory biomarkers such as cytokines, chemokines, inflammatory cells, neuropeptides, RANK/RANKL/OPG system and other inflammatory markers and to relate these systems to the development and progression of pathological conditions related to apical periodontitis.

The Presence and involvement of interleukin-17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)-17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL-17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL-17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL-17 in AP. A search related to IL-17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL-17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL-17 in AP.

Engineering Immune Tolerance with Biomaterials

Autoimmune diseases, rejection of transplanted organs and grafts, chronic inflammatory diseases, and immune-mediated rejection of biologic drugs impact a large number of people across the globe. New understanding of immune function is revealing exciting opportunities to help tackle these challenges by harnessing-or correcting-the specificity of immune function. However, realizing this potential requires precision control over the interaction between regulatory immune cues, antigens attacked during inflammation, and the tissues where these processes occur. Engineered materials-such as polymeric and lipid particles, scaffolds, and inorganic materials-offer powerful features that can help to selectively regulate immune function during disease without compromising healthy immune functions. This review highlights some of the exciting developments to leverage biomaterials as carriers, depots, scaffolds-and even as agents with intrinsic immunomodulatory features-to promote immunological tolerance.

CD8+ Foxp3+ T Cells Affect Alveolar Bone Homeostasis via Modulating Tregs/Th17 During Induced Periodontitis: an Adoptive Transfer Experiment

Periodontitis is a dysbiotic bacteria-mediated disease characterized by periodontal inflammations and alveolar bone damage. Its mechanisms were complicated, involving an inflammation-mediated bone destruction. We sought to determine roles and rules that CD8⁺ regulatory T cells (CD8⁺ Tregs) affect alveolar bone homeostasis during periodontitis. Presence of CD8⁺ Tregs in the gingiva, cervical lymph nodes (CLNs), and spleens of healthy or periodontitis animals was analyzed. CD8⁺ regulatory T cells from periodontitis animals were sorted by magnetic-activated cell sorting and fluorescent-activated cell sorting technique, subsequently injected into recipient animals to set adoptive transfer model. We induced experimental periodontitis on transfer models and equal number healthy animals. Four weeks later, their alveolar bone loss and osteoclast coverage length were measured. We also detected CD8⁺ Tregs, CD4⁺ T cell, CD4⁺ Tregs, Th17 cell, and IL-1β, IL-6, IL-10, IL-17A, RANKL, TGF-β expression in the gingiva, CLNs, and spleen to illustrate possible working mechanism of CD8⁺ regulatory T cells. Periodontitis does not induce significant change on proportion or amount of CD8⁺ Tregs. Adoptive transfer of CD8⁺ Tregs reduces alveolar bone destruction and osteoclast formation. In addition, experimental periodontitis increases percentage of Th17 cells and decreases CD4⁺ Tregs in the gingiva and CLNs. More IL-1β, IL-6, IL-17A, and RANKL, and less IL-10 and TGF-β are also detected in the gingiva and CLNs from animals with periodontitis than the one from healthy animals. Adoptive transfer of CD8⁺ regulatory T cells remedies all above pathological change effectively. We did not find any significant difference in spleen, regardless group and detected items. Outcomes of present study clarify function that CD8⁺ regulatory T cells affect alveolar bone homeostasis, and disclose its possible working mechanisms. CD8⁺ regulatory T cells protect alveolar bone via reducing osteoclastogenesis and modulating local immune response.

TBX21-1993T/C polymorphism association with Th1 and Th17 response at periapex and with periapical lesions development risk

TBX21-1993T/C (rs4794067) polymorphism increases the transcriptional activity of the Tbx21, essential for interferon gamma (IFNg) transcription, but its functional impact on development Th1- response in vivo remains unclear, as well its potential influence over inflammatory osteolytic conditions, such as periapical lesions. Therefore, this study comprises a case-control and functional investigation of Tbx21 genetic variations impact on Th1 response in vivo and in vitro, and its impact on periapical lesions risk and outcome, performed with a population of healthy controls (H; N = 283) and patients presenting periapical lesions (L; N = 188) or deep caries (DC; N = 152). TBX21-1993T/C genotyping demonstrated that the polymorphic allele C, as well TC/TC+CC genotypes, was significantly less frequent in the L patients compared to H and DC groups. Additionally, gene expression analysis demonstrates that T-cell-specific T-box transcription factor (Tbet) and IFNg transcripts levels were downregulated whereas IL-17 levels were upregulated in the TBX21-1993 C carriers (TC/TC+CC) in comparison with the TT group. Also, while TT and TC+CC genotypes are equally prevalent in the lesions presenting low IFN/IL17 ratio, a significant decrease in polymorphic TC+CC genotypes was observed in lesions presenting intermediate and high IFN/IL17 ratio. In vitro experiments confirmed the predisposition to Th1 polarization associated with TBX21-1993, since PBMC CD4 T cells from T allele carriers produce higher IFNg levels upon CD3/CD28 stimulation than the C group, in both standard/neutral and Th1-polarizing culture conditions. In conclusion, the TBX21-1993 T allele and TC/CC genotypes predispose to Th1-type immune response development in vitro, influence immune response polarization in vivo, and consequently account for the risk for apical periodontitis development.

DNA methylation profiles of immune response-related genes in apical periodontitis

AIM

To investigate the DNA methylation profiles of immune response-related genes in apical periodontitis (AP) lesions.

METHODOLOGY

The methylation profiles on the cytosine-phosphate-guanine (CpG) regions of 22 gene promoters involved in inflammation and autoimmunity were assessed in 60 human AP lesions and 24 healthy periodontal ligaments (controls) using a pathway-specific real-time polymerase chain reaction array (EpiTect® Methyl Signature PCR Array Human Inflammatory Response). Differentially methylated genes were subsequently assessed for their mRNA expression. Data analyses (One-way anova, Tukey's multiple comparisons tests and Mann-Whitney tests) were performed using GraphPad Prism 6 software. P values ≤ 0.05 were considered statistically significant.

RESULTS

Significant DNA hypermethylation was observed for CXCL3 and FADD gene promoters in AP lesions when compared to control tissues (P < 0.001) and among other genes (P < 0.05). In contrast, IL12B and IL4R were associated with significant hypomethylation in comparison to other genes (P < 0.05). IL12B, IL4R, CXCL3 and FADD had differential mRNA expression in AP lesions and controls (P < 0.001).

CONCLUSIONS

Differential methylation profiles of immune response-related genes, such as FADD, CXCL3, IL12B and IL4R, may have an influence on individual AP susceptibility and patient treatment outcomes, through their potential contributions to altered expression of disease-relevant genes. Methylation and/or genetic variations in additional genes may also contribute to the dynamics of AP development and should be considered in future studies.

RANKL Triggers Treg-Mediated Immunoregulation in Inflammatory Osteolysis

The chronic inflammatory immune response triggered by the infection of the tooth root canal system results in the local upregulation of RANKL, resulting in periapical bone loss. While RANKL has a well-characterized role in the control of bone homeostasis/pathology, it can play important roles in the regulation of the immune system, although its possible immunoregulatory role in infectious inflammatory osteolytic conditions remains largely unknown. Here, we used a mouse model of infectious inflammatory periapical lesions subjected to continuous or transitory anti-RANKL inhibition, followed by the analysis of lesion outcome and multiple host response parameters. Anti-RANKL administration resulted in arrest of bone loss but interfered in the natural immunoregulation of the lesions observed in the untreated group. RANKL inhibition resulted in an unremitting proinflammatory response, persistent high proinflammatory and effector CD4 response, decreased regulatory T-cell (Treg) migration, and lower levels of Treg-related cytokines IL-10 and TGFb. Anti-RANKL blockade impaired the immunoregulatory process only in early disease stages, while the late administration of anti-RANKL did not interfere with the stablished immunoregulation. The impaired immunoregulation due to RANKL inhibition is characterized by increased delayed-type hypersensitivity in vivo and T-cell proliferation in vitro to the infecting bacteria, which mimic the effects of Treg inhibition, reinforcing a possible influence of RANKL on Treg-mediated suppressive response. The adoptive transfer of CD4+FOXp3+ Tregs to mice receiving anti-RANKL therapy restored the immunoregulatory capacity, attenuating the inflammatory response in the lesions, reestablishing normal T-cell response in vivo and in vitro, and preventing lesion relapse upon anti-RANKL therapy cessation. Therefore, while RANKL inhibition efficiently limited the periapical bone loss, it promoted an unremitting host inflammatory response by interfering with Treg activity, suggesting that this classic osteoclastogenic mediator plays a role in immunoregulation.

MMP1-1607 polymorphism increases the risk for periapical lesion development through the upregulation MMP-1 expression in association with pro-inflammatory milieu elements

Increased matrix metalloproteinases (MMPs) activity is a hallmark of periapical granulomas. However, the factors underlying the MMPs expression modulation in healthy and diseased periapical tissues remains to be determined.