Salivary Colony Stimulating Factor-1 and Interleukin-34 in Periodontal Disease

Role of IL-34 and its receptors in inflammatory diseases

In recent years, IL-34 has been widely discussed as a novel cytokine. IL-34 is a pro-inflammatory cytokine binding four distinct receptors, namely CSF-1R, syndecan-1, PTP-ζ and TREM2. Previous studies have shown that IL-34 and its receptors play important roles in the development and progression of various inflammatory diseases. Therefore, IL-34 has the potential to be a biomarker and therapeutic target for inflammatory diseases. However, further study is still needed to identify the specific mechanism through which IL-34 contributes to illness. In this article, we review the recent advances in the biological roles of IL-34 and its receptors as well as their roles in the development and therapeutic application of inflammatory diseases.

Interleukin 34 in Disease Progressions: A Comprehensive Review

IL-34, a cytokine, discovered a decade before and is known to be a colony stimulating factor CSF-1 receptor (CSF-1R) ligand. Along with CSF-1R, it also interacts with syndecan-1 receptors and protein-tyrosine phosphatase (PTP-ζ). Hence, IL-34 takes part in a number of biological activities owing to its involvement in different signaling pathways. This review was done to analyze the recent studies on the functions of IL-34 in progression of diseases. The role of IL-34 under the physiological and pathological settings is studied by reviewing current data. In the last ten years, studies suggested that the IL-34 was involved in the regulation of morbid states such as inflammatory diseases, infections, transplant rejection, autoimmune diseases, neurologic diseases, and cancer. In general, the involvement of IL-34 is observed in many serious health ailments like metabolic diseases, heart diseases, infections and even cancer. As such, IL-34 can be regarded as a therapeutic target, potential biomarker or as a therapeutic tool, which ought to be assessed in future research activities.

Clinical and Biochemical Effects of Smoking on Non-Surgical Periodontal Treatment in Grade III Stage C Periodontitis Patients

Objective: The purpose of this study was to evaluate the effect of smoking on clinical parameters and the serum and saliva levels of RANKL, OPG, and IL-34 in periodontitis stage III grade C (III-C) patients after non-surgical periodontal treatment (NSPT). Methods: A total of 60 subjects, 40 periodontitis-III-C patients (20 smokers and 20 non-smokers) and 20 non-smoker periodontally healthy individuals, were included. All clinical periodontal parameters were recorded, and unstimulated saliva and serum samples were collected from all patients at baseline, but at 1 and 3 months only from periodontitis patients (N=40). Saliva and serum levels of RANKL, OPG, and IL-34 were analyzed by ELISA. Results: At baseline only whole mouth probing depth (PD) and percent of sites with PD>5mm were higher in smokers than non-smoker periodontitis patients (p

Interleukin-34 Permits Porphyromonas gingivalis Survival and NF-κB p65 Inhibition in Macrophages

Interleukin-34 (IL-34) is a cytokine that supports the viability and differentiation of macrophages. An important cytokine for the development of epidermal immunity, IL-34 is present and plays a role in the immunity of the oral environment. IL-34 has been linked to inflammatory periodontal diseases, which involve innate phagocytes, including macrophages. Whether IL-34 can alter the ability of macrophages to effectively interact with oral microbes is currently unclear. Using macrophages derived from human blood monocytes with either the canonical cytokine colony-stimulating factor (CSF)1 or IL-34, we compared the ability of the macrophages to phagocytose, kill, and respond through the production of cytokines to the periodontal keystone pathogen Porphyromonas gingivalis. While macrophages derived from both cytokines were able to engulf the bacterium equally, IL-34 derived macrophages were much less capable of killing internalized P. gingivalis. Of the macrophage cell surface receptors known to interact with P. gingivalis, DC-SIGN was found to have the largest variation between IL-34 and CSF1-derived macrophages. We also found that upon interaction with P. gingivalis, IL-34 derived macrophages produced significantly less of the neutrophil chemotactic factor IL-8 than macrophages derived in the presence of CSF1. Mechanistically, we identified that levels of IL-8 corresponded with P. gingivalis survival and dephosphorylation of the major transcription factor NF-κB p65. Overall, we found that macrophages differentiated in the presence of IL-34, a dominant cytokine in the oral gingiva, have a reduced ability to kill the keystone pathogen P. gingivalis and may be susceptible to specific bacteria-mediated cytokine modification. This article is protected by copyright. All rights reserved.

Gingival crevicular fluid CSF-1 and IL-34 levels in patients with stage III grade C periodontitis and uncontrolled type 2 diabetes mellitus

PURPOSE

Periodontal diseases are inflammatory conditions that alter the host's response to microbial pathogens. Type 2 diabetes mellitus (T2DM) is a complex disease that affects the incidence and severity of periodontal diseases. This study investigated the gingival crevicular fluid (GCF) levels of colony-stimulating factor-1 (CSF-1) and interleukin-34 (IL-34) in patients with stage III grade C periodontitis (SIII-GC-P) and stage III grade C periodontitis with uncontrolled type 2 diabetes (SIII-GC-PD).

METHODS

In total, 72 individuals, including 24 periodontally healthy (PH), 24 SIII-GC-P, and 24 SIII-GC-PD patients, were recruited for this study. Periodontitis patients (stage III) had interdental attachment loss (AL) of 5 mm or more, probing depth (PD) of 6 mm or more, radiographic bone loss advancing to the middle or apical part of the root, and tooth loss (<5) due to periodontal disease. Radiographic bone loss in the teeth was also evaluated; grade C periodontitis was defined as a ratio of the percentage of root bone loss to age greater than 1.0. The plaque index (PI), gingival index (GI), presence of bleeding on probing (BOP), PD, and clinical AL were used for clinical periodontal assessments. GCF samples were obtained and analyzed using an enzyme-linked immunosorbent assay.

RESULTS

All clinical parameters-PD, AL, GI, BOP, and PI-were significantly higher in the SIII-GC-PD group than in the PH and SIII-GC-P groups for both the full mouth and each sampling site (P<0.05). The total IL-34 and CSF-1 levels were significantly higher in the SIII-GC-PD group than in the PH and SIII-GC-P groups (P<0.05), and there were significant differences between the periodontitis groups (P<0.05).

CONCLUSIONS

These findings suggest that IL-34 and CSF-1 expression increases in patients with SIII-GC-PD. CSF-1 was associated with the inflammatory status of periodontal tissues and T2DM, while IL-34 was associated only with T2DM.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04891627.

Effect of Non-surgical Periodontal Treatment on Salivary and Serum Biomarkers in Stage III Grade B and C Periodontitis

BACKGROUND

This study aimed to evaluate the levels of total matrix metalloproteinase-8 (MMP-8), macrophage-activating factors (MAF), macrophage inflammatory protein (MIP)-1α, macrophage colony-stimulating factor (M-CSF), interleukin (IL)-34 in saliva and serum of periodontally healthy, periodontitis stage III grade B (P-III-B) and grade C (P-III-C) participants and to compare the changes after non-surgical periodontal treatment (NSPT).

METHODS

A total of non-smoker and systemically healthy 65 participants, 20 periodontally healthy, 20 P-III-B, and 25 P-III-C were recruited for the study. The periodontal parameters were recorded, saliva and serum samples were obtained from all participants at baseline. In periodontitis groups, the periodontal parameters were reevaluated, and the samples were recollected at 1 and 3 months following the NSPT. MMP-8, MAF, MIP-1α, M-CSF, and IL34 levels were measured by ELISA. Receiver operating characteristics curve was performed for estimating the area under the curve (AUC).

RESULTS

All periodontal parameters were improved in periodontitis groups after NSPT (p<0.05). Among tested molecules, salivary MMP-8 and MAF were higher in both periodontitis groups compared to healthy controls (p<0.05) at baseline and significantly decreased after NSPT (p<0.05) to healthy levels or below. Salivary MMP-8 had the highest diagnostic ability both for P-III-B (AUC:0.78 sensitivity: 80%; specificity: 80%) and P-III-C (AUC:0.88 sensitivity: 88%; specificity: 80%). Moreover, after adjusting for age, periodontitis groups were associated with salivary MMP-8 and MAF levels (p<0.05).

CONCLUSION

The present study showed that high salivary MMP-8 and MAF levels were associated with non-smoker, systemically healthy P-III-B and P-III-C. Moreover, NSPT was remarkably reduced their levels. This article is protected by copyright. All rights reserved.

IL-34, the rationale of its expression in physiological and pathological condition

IL-34 is a cytokine that shares one of its receptors with CSF-1. It has long been thought that CSF-1 receptor (CSF-1R) receives signals only from CSF-1, but the identification of IL-34 reversed this stereotype. Regardless of low structural homology, IL-34 and CSF-1 emanate similar downstream signaling through binding to CSF-1R and provoke similar but different physiological events afterward. In addition to CSF-1R, protein-tyrosine phosphatase (PTP)-ζ and Syndecan-1 were also identified as IL-34 receptors and shown to be at play. Although IL-34 expression is limited to particular tissues in physiological conditions, previous studies have revealed that it is upregulated in several diseases. In cancer, IL-34 is produced by several types of tumor cells and contributes to therapy resistance and disease progression. A recent study has demonstrated that tumor cell-derived IL-34 abrogates immunotherapy efficacy through myeloid cell remodeling. On the other hand, IL-34 expression is downregulated in some brain and dermal disorders. Despite accumulating insights, our understanding of IL-34 may not be even close to its nature. This review aims to comprehensively describe the physiological and pathological roles of IL-34 based on its similarity and differences to CSF-1 and discuss the rationale for its disease-dependent expression pattern.

Interleukin-34 promotes tumorigenic signals for colon cancer cells

Colorectal carcinoma (CRC) is one of the most common forms of malignancy in the Western world. Accumulating evidence indicates that colon carcinogenesis is tightly controlled by tumour-associated immune cells and stromal cells, which can either stimulate or suppress CRC cell growth and survival, mainly via the production of cytokines. Interleukin-34 (IL-34), a cytokine known to regulate mainly monocyte/macrophage survival and function, is highly produced within the CRC microenvironment by several cell types, including cancer cells, tumour-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), and regulates the pro-tumoural functions of such cells. In this article, we summarize the available data supporting the multiple effects of IL-34 in human CRC.

Colony-stimulating factor-1 receptor blockade attenuates inflammation in inflamed gingival tissue explants

BACKGROUND AND OBJECTIVE

Colony-stimulating factor-1 receptor (CSF-1R) regulates myeloid cell function and mediates osteoclastogenesis. CSF-1R blockade has been suggested as a potential therapeutic target to halt inflammation and bone resorption; however, the expression and function of CSF-1R in human gingiva is yet unknown.

METHODS

Gingival tissue was collected from 22 non-periodontitis controls and 31 periodontitis (PD) patients. CSF-1R expression in gingival tissue was assessed with q-PCR, western blot, and immunohistochemistry (IHC). Cell surface expression of CSF-1R was analyzed by flow cytometry. The effects of CSF-1R inhibition on the production of inflammatory mediators by inflamed gingival tissue explants and peripheral blood mononuclear cells (PBMCs) were assessed with a bead-based multiplex array and ELISA.

RESULTS

CSF-1R protein expression was increased in gingival tissue from PD patients compared with controls as assessed with western blot (1.5-fold increase) and IHC (4.5-fold increase). Similar proportions of HLA-DR⁺ CD64⁺ cells and comparable CSF-1R expression in this cell population were found in gingival tissue from PD patients and controls. In peripheral blood monocytes, CSF-1R was predominantly expressed by non-classical and intermediate monocytes. Targeting CSF-1R in gingival tissue explants attenuated the production of MMP-1, MMP-2, MMP-12, and MMP-13. The blocking in PBMCs attenuated the production of IL-8 and MMP-9.

CONCLUSION

These results indicate that CSF-1R is elevated in PD, and its inhibition attenuates inflammatory mediators in the inflamed gingival tissue and circulating myeloid cells. Together these findings suggest that CSF-1R might be involved in regulating inflammatory processes in PD, and a potential therapeutic target to reduce the harmful inflammation.

Levels of myeloid-related proteins in saliva for screening and monitoring of periodontal disease

AIM

To evaluate the salivary levels of myeloid-related markers in relation to periodontal disease and their potential screening capability, as well as the effects of periodontal treatment on these markers in periodontitis patients.

MATERIALS AND METHODS

Participants with a healthy periodontium (n = 60) and with gingivitis (n = 63) and periodontitis (n = 72) were recruited. Periodontitis patients received non-surgical treatment and were re-examined after 3 and 6 months. Unstimulated saliva was collected at baseline and at 1, 3, and 6 months after therapy for the periodontitis patients. Levels of colony-stimulating factor-1 (CSF-1), interleukin-34 (IL-34), S100A8/A9, S100A12, hepatocyte growth factor (HGF), IL-1β, and matrix metalloproteinase-8 (MMP-8) were analysed by immunoassays.

RESULTS

CSF-1, S100A8/A9, S100A12, IL-1β, MMP-8, and HGF were significantly elevated in saliva from periodontitis and gingivitis patients in comparison to healthy individuals, whereas IL-34 was significantly lower in periodontitis compared to both healthy individuals and gingivitis patients. IL-34 increased significantly 3 months after treatment, while IL-1β and MMP-8 decreased 1 month after therapy. Additionally, periodontitis patients clustered in high and low levels of S100A8/A9, whereby those with high levels had more bleeding, deeper pockets, and higher S100A12.

CONCLUSIONS

Salivary levels of myeloid-related markers are altered in periodontitis and are partially modulated by periodontal treatment. Measuring S100A8/A9 in saliva may identify distinct groups of periodontitis patients.

Emerging roles of Interleukin-34 together with receptor activator of nuclear factor-kB ligand and osteoprotegerin levels in periodontal disease

OBJECTIVE

The dependence between gingival crevicular fluid (GCF) of Interleukin-34 (IL-34) level and Receptor activator of nuclear factor -kB ligand/ osteoprotegerin (RANKL/OPG) ratio in the severity of periodontitis might reveal an unknown pathway of diseases with bone destruction. There is no study about the evaluation of IL-34 levels together with GCF RANKL and OPG levels in periodontitis patients before and after non-surgical periodontal treatment (NSPT). The objectives of this research were to investigate changes in the levels and relative ratios of IL-34, OPG, and RANKL in the GCF of patients with periodontitis before and after NSPT.

MATERIALS AND METHODS

20 healthy participants (CTRL), 20 patients with stage 3-grade B periodontitis and 20 with stage 3-grade C periodontitis were recruited. GCF and clinical periodontal recordings were investigated at the baseline and 6 weeks after NSPT. Enzyme-linked immunosorbent assay (ELISA) were used for quantifying of GCF IL-34, RANKL and OPG levels and their relative ratios were calculated.

RESULTS

Greater values for GCF IL-34 and RANKL levels were found in the both of periodontitis groups than in CTRL group at baseline, whereas GCF OPG levels were statistically lower at baseline (P < 0.05). GCF IL-34 and RANKL levels decreased in the 6th week after NSPT in the both periodontitis groups, while the concentration OPG levels statistically increased (P < 0.05). Significantly positive correlations among the IL-34 with RANKL, sampled-site clinical attachment level (CAL), and gingival index (GI), whereas negative correlation with OPG were reported (P < 0.05).

CONCLUSIONS

GCF IL-34 levels was high in patients with periodontitis and decreased after NSPT and its levels showed positive correlations with RANKL/OPG ratio levels CAL and GI. Determining of IL-34 levels together with RANKL/OPG ratio in GCF may therefore be valuable in detecting high risk individuals with periodontitis patients.

IL-34 and CSF-1, deciphering similarities and differences at steady state and in diseases

Although IL-34 and CSF-1 share actions as key mediators of monocytes/macrophages survival and differentiation, they also display differences that should be identified to better define their respective roles in health and diseases. IL-34 displays low sequence homology with CSF-1 but has a similar general structure and they both bind to a common receptor CSF-1R, although binding and subsequent intracellular signaling shows differences. CSF-1R expression has been until now mainly described at a steady state in monocytes/macrophages and myeloid dendritic cells, as well as in some cancers. IL-34 has also 2 other receptors, protein-tyrosine phosphatase zeta (PTPζ) and CD138 (Syndecan-1), expressed in some epithelium, cells of the central nervous system (CNS), as well as in numerous cancers. While most, if not all, of CSF-1 actions are mediated through monocyte/macrophages, IL-34 has also other potential actions through PTPζ and CD138. Additionally, IL-34 and CSF-1 are produced by different cells in different tissues. This review describes and discusses similarities and differences between IL-34 and CSF-1 at steady state and in pathological situations and identifies possible ways to target IL-34, CSF-1, and its receptors.

Recent insights of the role and signalling pathways of interleukin-34 in liver diseases

Liver disease is a global health problem and is a primary cause of mortality and morbidity worldwide. Specifically, it accounts for approximately two million deaths per year worldwide. The common causes of mortality are the complications of liver cirrhosis, viral hepatitis and hepatocellular carcinoma (HCC). The mechanism of immune response and infiltration of cellular immunity is essential for promoting hepatic inflammatory, especially when the liver is abundant with lymphocytes and phagocytic cells. The injured and immunity cells secret different types of interleukins (cytokines), which can directly or indirectly amplify or inhibit liver inflammation. Many types of cells can produce interleukin-34 (IL-34) that induces the release of multiple inflammatory factors in patients via interaction with various cytokines. This phenomenon leads to the enlargement of the inflammatory response to liver diseases and induces liver fibrosis. This review highlights the proposed roles of IL-34 in liver diseases and discusses the recent findings of IL-34 that support its emerging role in HCC. Specifically, the facilitating effects of these new insights on the rational development of IL-34 for targeted therapies in the future are explored.

Role of Interleukin-34 in Cancer

Cross-talk between cancer cells and the immune cells occurring in the tumor microenvironment is crucial in promoting signals that foster tumor growth and metastasis. Both cancer cells and immune cells secrete various interleukins (IL), which, either directly or indirectly, stimulate cancer-cell proliferation, survival, and diffusion, as well as contribute to sculpt the immune microenvironment, thereby amplifying tumorigenic stimuli. IL-34, a cytokine produced by a wide range of cells, has been initially involved in the control of differentiation, proliferation, and survival of myeloid cells. More recent studies documented the overexpression of IL-34 in several cancers, such as hepatocarcinoma, osteosarcoma, multiple myeloma, colon cancer, and lung cancer, and showed that tumor cells can produce and functionally respond to this cytokine. In this review, we summarize the multiple roles of IL-34 in various cancers, with the aim to better understand the relationship between the expression of this cytokine and cancer behavior and to provide new insights for exploring a new potential therapeutic target.

Interleukin-34 as a promising clinical biomarker and therapeutic target for inflammatory arthritis

Interleukin-34 (IL-34), recently identified as a novel inflammatory cytokine and the second ligand for colony-stimulating factor-1 receptor, is known to play regulatory roles in the development, maintenance, and function of mononuclear phagocyte lineage cells - especially osteoclasts. Regarding its primary effect on osteoclasts, IL-34 has been shown to stimulate formation and activation of osteoclasts, which in turn magnifies osteoclasts-resorbing activity. In addition to its role in osteoclastogenesis, IL-34 has been implicated in inflammation of synovium via augmenting production of inflammatory mediators, in which altered IL-34 expression is regulated by pro-inflammatory cytokines responsible for cartilage degradation. Indeed, IL-34 has been documented to be highly expressed in inflamed synovium of rheumatoid arthritis (RA) and knee osteoarthritis (OA) patients, which are recognized as inflammatory arthritis. Furthermore, a number of clinical studies demonstrated that IL-34 levels were significantly increased in the circulation and synovial fluid of patients with RA and knee OA. Its levels were also found to be positively associated with disease severity - especially radiographic severity of both RA and knee OA patients. Interestingly, emerging evidence has accumulated that functional blockage of IL-34 with specific antibody can alleviate the severity of inflammatory arthritis. It is therefore reasonable to speculate that IL-34 may be developed as a potential biomarker and a new therapeutic candidate for inflammatory arthritis. To date, there are numerous studies showing IL-34 involvement and association with many aspects of inflammatory arthritis. Herein, this review aimed to summarize the recent findings regarding regulatory role of IL-34 in synovial inflammation-mediated cartilage destruction and update the current comprehensive knowledge on usefulness of IL-34-based treatment in inflammatory arthritis - particularly RA and knee OA.

Biological functions and clinical implications of interleukin-34 in inflammatory diseases

Interleukin (IL)-34 is a recently discovered cytokine and ligand of the colony-stimulating factor (CSF)-1 receptor. Although CSF-1 and IL-34 share similar biological properties, their expression patterns and downstream signaling pathways are distinct. IL-34 can influence differentiation and has functions in multiple cell types (e.g., dendritic cells, monocytes, macrophages). In the pathological conditions, IL-34 is induced by pro-inflammatory stimuli (e.g., cytokines, pathogen-associated molecular patterns, and infection). Current evidence shows that IL-34 is a critical player in inflammatory response and is involved in the pathogenesis of inflammatory autoimmune dysfunction. Therefore, IL-34 may be a promising clinical biomarker and therapeutic target for treating inflammatory related disorders. In this article, we review the advances in biological functions of IL-34 and our understanding of its role in the development of inflammatory diseases as well as therapeutic applications.

Interleukin-34 Levels in Gingival Crevicular Fluid and Plasma in Healthy and Diseased Periodontal Tissue in Presence or Absence of Obesity: A Clinico-biochemical Study

Interleukin (IL)-34 has recently been identified as an alternative ligand for colonystimulating factor-1 receptor and plays an important role in osteoclastogenesis. The aim of this study was to assess and compare IL-34 levels in gingival crevicular fluid (GCF) and plasma in obese individuals in the presence or absence of periodontal disease and to determine whether they showed a correlation with disease severity. Forty patients aged between 25 and 40 yr were enrolled and categorized into 4 groups: 10 non-obese patients with healthy periodontium (Group I); 10 obese patients with healthy periodontium (Group II); 10 non-obese patients with chronic periodontitis (Group III); and 10 obese patients with chronic periodontitis (Group IV). Demographic variables such as age and body mass index score were recorded and assessed, together with clinical periodontal parameters such as the gingival index, probing pocket depth, and clinical attachment level scores in all groups. The GCF and plasma levels of IL-34 were quantified using enzyme-linked immunosorbent assay. The results showed that the mean IL-34 concentrations in GCF or plasma were highest in Group IV, followed by Group III, Group II, and Group I, with the difference among them being statistically significant (p<0.05). These results suggest that obese individuals with periodontitis have higher GCF and plasma IL-34 levels than non-obese individuals with healthy periodontium. This suggests IL-34 as a potential inflammatory marker of periodontal disease and obesity.

Interleukin-34, a comprehensive review

IL-34 is a novel cytokine that was identified in 2008 in a comprehensive proteomic analysis as a tissue-specific ligand of CSF-1 receptor (CSF-1R). IL-34 exists in all vertebrates including fish, amphibians, birds, and mammals, showing high conservation among species. Structurally, IL-34 belongs to the short-chain helical hematopoietic cytokine family but shows no apparent consensus structural domains, motifs, or sequence homology with other cytokines. IL-34 is synthesized as a secreted homodimeric glycoprotein that binds to the extracellular domains of CSF-1R and receptor-type protein-tyrosine phosphatase-zeta (PTP-ζ) in addition to the chondroitin sulfate chains of syndecan-1. These interactions result in activating several signaling pathways that regulate major cellular functions, including proliferation, differentiation, survival, metabolism, and cytokine/chemokine expression in addition to cellular adhesion and migration. In the steady state, IL-34 contributes to the development and maintenance of specific myeloid cell subsets in a tissue-specific manner: Langerhans cells in the skin and microglia in the brain. In pathological conditions, changes in IL-34 expression-increased or decreased-are involved in disease pathogenesis and correlate with progression, severity, and chronicity. One decade after its discovery, IL-34 has been introduced as a newcomer to the big family of interleukins with specific physiological functions, critical pathological roles, and promising clinical applications in disease diagnosis and treatment. In this review, we celebrate the 10th anniversary of IL-34 discovery, introducing its biological characteristics, and discussing the importance of IL-34 signaling network in health and disease.

Enhanced expression of IL-34 in an inflammatory cyst of the submandibular gland: a case report

Background

Cysts of the salivary glands are common lesions that occur in the context of various etiologies. Although the diagnostic importance of cysts in salivary gland diseases has been well studied, molecular mechanisms that control the related pathological process remain largely unknown. IL-34 is a novel cytokine that was discovered recently as a tissue-specific ligand of colony stimulating factor-1 receptor. Since its discovery, accumulating evidence has revealed emerging roles of IL-34 in various pathological conditions and has been suggested to correlate remarkably with inflammation. In this study, we report a medical case of an inflammatory cyst within the submandibular gland, through which evaluating the possible involvement of IL-34 in salivary gland disorders.

Case presentation

A 37-year-old male patient suffered from a sudden swelling in the right submandibular region, started initially small and had gradually increased in size to reach 3–4 cm in 1 week, accompanied by pain and local fever. Ultrasonography and MRI imaging revealed the existence of a well-defined cystic lesion with sharp borders measuring 39.8 mm × 19.7 mm within the right submandibular gland. The cyst was removed surgically, and the diagnostic decision was determined based on histopathological observations as an inflammatory cyst in the submandibular gland. Sections were generated from different regions of the surgically resected inflammatory cyst and used to examine IL-34 expression by immunohistochemistry compared to normal salivary gland tissues. Immunohistochemical staining showed enhanced expression of IL-34 in the ductal epithelial cells and endothelial cells of blood vessels, with a tendency to be accompanied with high infiltration of immune cells, which suggests a possible involvement of IL-34 in the pathogenesis of salivary gland inflammation.

Conclusions

In this report, we introduce interesting findings of enhanced IL-34 expression in a case of an inflamed submandibular gland. Our findings emphasize the pathological roles of IL-34 as an inflammation amplifier and angiogenic enhancer in inflammatory conditions, such as in salivary gland disorders.

Electronic supplementary material

The online version of this article (10.1186/s41232-018-0069-6) contains supplementary material, which is available to authorized users.

Salivary matrix metalloproteinase (MMP)-8 as a biomarker for periodontitis: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

Salivary matrix metalloproteinase (MMP)-8 is currently considered to be one of the most promising biomarkers for early diagnosis of periodontitis, however, several recent studies showed conflicting results.

OBJECTIVE

To determine the salivary matrix metalloproteinase (MMP)-8 levels between periodontitis patients and healthy individuals, and to assess its diagnostic value in periodontitis.

METHODS

Literatures were searched on PubMed and Embase databases up to August 2017, for articles reporting salivary MMP-8 levels between periodontitis patients and health controls with the data of means ± standard deviation (SD). Methodological quality was assessed by the Newcastle Ottawa scale (NOS). Standard mean differences (SMDs), heterogeneity, and publication bias were assessed by Stata 13.0 software.

RESULTS

A total of 10 studies including 485 periodontitis patients and 379 healthy controls that met the preset inclusion criteria were included, the qualities of these studies were either good (n = 7) or moderate (n = 3). Eight studies showed salivary MMP-8 levels were higher in periodontitis patients compared with healthy controls (P < .05), while 2 studies showed opposite results (P > .05). The pooled SMD was 1.195 (95% CI: 0.720-1.670), with I of 89.3%, indicating high heterogeneity. Funnel plot showed publication bias existed.

CONCLUSION

Our meta-analysis showed that salivary MMP-8 levels were significantly higher in periodontitis patients compared with healthy controls overall. Due to the heterogeneity and publication bias of included studies, further high quality studies are still needed to verify the conclusion.

Colony stimulating factor-1 in saliva in relation to age, smoking, and oral and systemic diseases

Colony stimulating factor (CSF)-1 is a growth factor that stimulates the survival, proliferation and differentiation of mononuclear phagocytes, which has been implicated in several inflammatory diseases. This study evaluated the possible influence of age, sex, smoking, periodontitis, caries, and several systemic conditions on salivary levels of CSF-1. Four-hundred and forty-one individuals were enrolled in this study. All participants answered a health questionnaire and underwent a comprehensive oral examination. Stimulated saliva was collected and CSF-1 levels were analysed by enzyme-linked immunosorbent assay. Salivary levels of CSF-1 were significantly increased in participants over 64 years old and in non-smoking individuals, whereas no difference was observed between men and women. Individuals having periodontitis and manifest caries had significantly higher levels of CSF-1. Participants with muscle and joint disease exhibited increased CSF-1 levels as compared to those without. Age, smoking, percentage of pockets ≥4 mm, number of manifest caries lesions, and presence of tumor were associated with CSF-1 levels. Salivary levels of CSF-1 are associated with age, smoking, periodontitis, manifest caries, and the presence of muscle and joint diseases and tumors. CSF-1 might be a promising biomarker candidate in saliva of both local and systemic conditions that needs further investigation.