Sodium-chloride-induced effects on the expression profile of human periodontal ligament fibroblasts with focus on simulated orthodontic tooth movement

Matrix Metalloproteinases in the Periodontium-Vital in Tissue Turnover and Unfortunate in Periodontitis

The extracellular matrix (ECM) is a complex non-cellular three-dimensional macromolecular network present within all tissues and organs, forming the foundation on which cells sit, and composed of proteins (such as collagen), glycosaminoglycans, proteoglycans, minerals, and water. The ECM provides a fundamental framework for the cellular constituents of tissue and biochemical support to surrounding cells. The ECM is a highly dynamic structure that is constantly being remodeled. Matrix metalloproteinases (MMPs) are among the most important proteolytic enzymes of the ECM and are capable of degrading all ECM molecules. MMPs play a relevant role in physiological as well as pathological processes; MMPs participate in embryogenesis, morphogenesis, wound healing, and tissue remodeling, and therefore, their impaired activity may result in several problems. MMP activity is also associated with chronic inflammation, tissue breakdown, fibrosis, and cancer invasion and metastasis. The periodontium is a unique anatomical site, composed of a variety of connective tissues, created by the ECM. During periodontitis, a chronic inflammation affecting the periodontium, increased presence and activity of MMPs is observed, resulting in irreversible losses of periodontal tissues. MMP expression and activity may be controlled in various ways, one of which is the inhibition of their activity by an endogenous group of tissue inhibitors of metalloproteinases (TIMPs), as well as reversion-inducing cysteine-rich protein with Kazal motifs (RECK).

Development of a short-form Chinese health literacy scale for low salt consumption (CHLSalt-22) and its validation among hypertensive patients

Background

With the accelerated pace of people’s life and the changing dietary patterns, the number of chronic diseases is increasing and occurring at a younger age in today’s society. The speedily rising hypertensive patients have become one of the main risk factors for chronic diseases. People should focus on health literacy related to salt consumption and reach a better quality of life. Currently, there is a lack of local assessment tools for low salt consumption in mainland China.

Objective

To develop a short-form version of the Chinese Health Literacy Scale For Low Salt Consumption instrument for use in mainland China.

Methods

A cross-sectional design was conducted on a sample of 1472 people in Liaoxi, China. Participants completed a sociodemographic questionnaire, the Chinese version of the CHLSalt-22, the measuring change in restriction of salt (sodium) in the diet in hypertensives (MCRSDH-SUST), the Brief Illness Perception Questionnaire (BIPQ), and the Benefit-Finding Scales (BFS) to test the hypothesis. Exploratory factor analysis and confirmatory factor analyses were performed to examine the underlying factor structure of the CHLSalt-22. One month later, 37 patients who participated in the first test were recruited to evaluate the test-retest reliability.

Results

The CHLSalt-22 demonstrated adequate internal consistency, good test-retest reliability, satisfactory construct validity, convergent validity and discriminant validity. The CHLSalt-22 count scores were correlated with age, sex, body mass index (BMI), education level, income, occupation, the Measuring Change in Restriction of Salt (sodium) in Diet in Hypertensives (MCRSDH-SUST), the Brief Illness Perception Questionnaire (BIPQ), and the Benefit-Finding Scales (BFS).

Conclusion

The results indicate that the Chinese Health Literacy Scale For Low Salt Consumption (CHLSalt-22) version has good reliability and validity and can be considered a tool to assess health literacy related to salt consumption in health screenings.

Xanthohumol exerts anti-inflammatory effects in an in vitro model of mechanically stimulated cementoblasts

Xanthohumol (XN) is a prenylated plant polyphenol that naturally occurs in hops and its products, e.g. beer. It has shown to have anti-inflammatory and angiogenesis inhibiting effects and it prevents the proliferation of cancer cells. These effects could be in particular interesting for processes within the periodontal ligament, as previous studies have shown that orthodontic tooth movement is associated with a sterile inflammatory reaction. Based on this, the study evaluates the anti-inflammatory effect of XN in cementoblasts in an in vitro model of the early phase of orthodontic tooth movement by compressive stimulation. XN shows a concentration-dependent influence on cell viability. Low concentrations between 0.2 and 0.8 µM increase viability, while high concentrations between 4 and 8 µM cause a significant decrease in viability. Compressive force induces an upregulation of pro-inflammatory gene (Il-6, Cox2, Vegfa) and protein (IL-6) expression. XN significantly reduces compression related IL-6 protein and gene expression. Furthermore, the expression of phosphorylated ERK and AKT under compression was upregulated while XN re-established the expression to a level similar to control. Accordingly, we demonstrated a selective anti-inflammatory effect of XN in cementoblasts. Our findings provide the base for further examination of XN in modulation of inflammation during orthodontic therapy and treatment of periodontitis.

The degradation of gelatin/alginate/fibrin hydrogels is cell type dependent and can be modulated by targeting fibrinolysis

In tissue engineering, cell origin is important to ensure outcome quality. However, the impact of the cell type chosen for seeding in a biocompatible matrix has been less investigated. Here, we investigated the capacity of primary and immortalized fibroblasts of distinct origins to degrade a gelatin/alginate/fibrin (GAF)-based biomaterial. We further established that fibrin was targeted by degradative fibroblasts through the secretion of fibrinolytic matrix-metalloproteinases (MMPs) and urokinase, two types of serine protease. Finally, we demonstrated that besides aprotinin, specific targeting of fibrinolytic MMPs and urokinase led to cell-laden GAF stability for at least forty-eight hours. These results support the use of specific strategies to tune fibrin-based biomaterials degradation over time. It emphasizes the need to choose the right cell type and further bring targeted solutions to avoid the degradation of fibrin-containing hydrogels or bioinks.

Dietary salt and myeloid NFAT5 (nuclear factor of activated T cells 5) impact on the number of bone-remodelling cells and frequency of root resorption during orthodontic tooth movement

PURPOSE

The aim of the study was to investigate the impact of dietary salt and the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5) in myeloid cells on bone remodelling cells as osteocytes, osteoblasts and osteoclasts and on force-induced dental root resorptions in a mouse model.

METHODS

Control mice and mice lacking myeloid NFAT5 (nuclear factor of activated T cells 5) were either kept on low, normal or high salt diets. After one week on the specified diet an elastic band was inserted between the first and second molar to induce orthodontic tooth movement. One week later the mice were euthanised and jaws were fixed for histological analysis. Osteocyte, osteoblast and osteoclast numbers as well as extent of root resorptions were assessed histologically.

RESULTS

Osteocyte number was diminished with high salt diet in wildtype mice. Osteoblast numbers increased with low salt diet in control mice and reduced with high salt diet in mice without NFAT5 in myeloid cells. High salt diet tended to increase osteoclast number in control mice. In mice without myeloid NFAT5, numbers of osteoclasts were reduced under high salt diet. Frequency of force-induced root resorptions tended to be dependent on dietary salt content in control mice.

CONCLUSION

During orthodontic tooth movement dietary salt impacts on the frequency of root resorptions and the number of osteoclasts and osteoblasts in alveolar bone of mice. This can affect bone remodelling during orthodontic treatment. Myeloid NFAT5 impacts on this salt-dependent reaction.

Apolipoprotein E is an effective biomarker for orthodontic tooth movement in patients treated with transmission straight wire appliances

INTRODUCTION

Orthodontic tooth movement (OTM) is the core component of orthodontic treatment and is increasingly popular for treating malocclusions. In this study, we aimed to investigate the role of apolipoprotein E (ApoE) in OTM.

METHODS

Thirty patients treated with transmission straight wire technology were selected and longitudinally tracked at 2 different stages of orthodontic treatment (initial 2 months and 12 months of orthodontic treatment). Total saliva was collected and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Western blotting was used to detect the difference in ApoE expression in the saliva samples of the 2 groups. The expression of ApoE was further verified by immunohistochemical staining in a mouse model of tooth movement.

RESULTS

The results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry showed significant differences in the components of the salivary peptides in the 2 groups and peptides with a molecular weight of 2010.7 Da were predicted to be ApoE by database analysis. Western blotting further verified a significant difference in the expression of salivary ApoE in the 2 groups. In addition, an OTM model was successfully constructed in mice. The immunohistochemical staining results showed that ApoE expression significantly increased after force loading in the OTM model.

CONCLUSIONS

This study indicated that ApoE participated in and played a role during OTM in patients treated with transmission straight wire technology. This relationship might be related to alveolar bone reconstruction and root resorption. The results provide new ideas for research on the mechanism of tooth movement using precision medicine based on saliva detection.

Effects of histamine and various histamine receptor antagonists on gene expression profiles of macrophages during compressive strain

Purpose

Tissue hormone histamine can accumulate locally within the periodontal ligament via nutrition or may be released during allergic reactions by mast cells, which may have an impact on orthodontic tooth movement. In addition to periodontal ligament fibroblasts, cells of the immune system such as macrophages are exposed to compressive strain. The aim of this study was thus to investigate the impact of histamine on the gene expression profile of macrophages in the context of simulated orthodontic compressive strain.

Methods

Macrophages were incubated with different histamine concentrations (50, 100, 200 µM) for 24 h and then either left untreated or compressed for another 4 h. To assess the role of different histamine receptors, we performed experiments with antagonists for histamine 1 receptor (cetirizine), histamine 2 receptor (ranitidine) and histamine 4 receptor (JNJ7777120) under control and pressure conditions. We tested for lactate dehydrogenase release and analyzed the expression of genes involved in inflammation and bone remodeling by reverse transcription quantitative polymerase chain reaction (RT-qPCR).

Results

Histamine elevated gene expression of tumor necrosis factor under control conditions and in combination with pressure application. Increased prostaglandin-endoperoxide synthase‑2 mRNA was observed when histamine was combined with compressive force. Interleukin‑6 gene expression was not affected by histamine treatment. In macrophages, compressive strain increased osteoprotegerin gene expression. Histamine further elevated this effect. Most of the observed histamine effects were blocked by the histamine 1 receptor antagonist cetirizine.

Conclusions

Histamine has an impact on the gene expression profile of macrophages during compressive strain in vitro, most likely having an impairing effect on orthodontic tooth movement by upregulation of osteoprotegerin expression.

Impact of Leptin on Periodontal Ligament Fibroblasts during Mechanical Strain

Orthodontic treatment to correct dental malocclusions leads to the formation of pressure zones in the periodontal ligament resulting in a sterile inflammatory reaction, which is mediated by periodontal ligament fibroblasts (PDLF). Leptin levels are elevated in obesity and chronic inflammatory responses. In view of the increasing number of orthodontic patients with these conditions, insights into effects on orthodontic treatment are of distinct clinical relevance. A possible influence of leptin on the expression profile of PDLF during simulated orthodontic mechanical strain, however, has not yet been investigated. In this study, PDLF were exposed to mechanical strain with or without different leptin concentrations. The gene and protein expression of proinflammatory and bone-remodelling factors were analysed with RT-qPCR, Western-blot and ELISA. The functional analysis of PDLF-induced osteoclastogenesis was analysed by TRAP (tartrate-resistant acid phosphatase) staining in coculture with human macrophages. Pressure-induced increase of proinflammatory factors was additionally elevated with leptin treatment. PDLF significantly increased RANKL (receptor activator of NF-kB ligand) expression after compression, while osteoprotegerin was downregulated. An additional leptin effect was demonstrated for RANKL as well as for subsequent osteoclastogenesis in coculture after TRAP staining. Our results suggest that increased leptin concentrations, as present in obese patients, may influence orthodontic tooth movement. In particular, the increased expression of proinflammatory factors and RANKL as well as increased osteoclastogenesis can be assumed to accelerate bone resorption and thus the velocity of orthodontic tooth movement in the orthodontic treatment of obese patients.

Differential gene expression response of synovial fibroblasts from temporomandibular joints and knee joints to dynamic tensile stress

Purpose

Apart from other risk factors, mechanical stress on joints can promote the development of osteoarthritis (OA), which can also affect the temporomandibular joint (TMJ), resulting in cartilage degeneration and synovitis. Synovial fibroblasts (SF) play an important role in upkeeping joint homeostasis and OA pathogenesis, but mechanical stress as a risk factor might act differently depending on the type of joint. We thus investigated the relative impact of mechanical stress on the gene expression pattern of SF from TMJs and knee joints to provide new insights into OA pathogenesis.

Methods

Primary SF isolated from TMJs and knee joints of mice were exposed to mechanical strain of varying magnitudes. Thereafter, the expression of marker genes of the extracellular matrix (ECM), inflammation and bone remodelling were analysed by quantitative real-time polymerase chain reaction (RT-qPCR).

Results

SF from the knee joints showed increased expression of genes associated with ECM remodelling, inflammation and bone remodelling after mechanical loading, whereas TMJ-derived SF showed reduced expression of genes associated with inflammation and bone remodelling. SF from the TMJ differed from knee-derived SF with regard to expression of ECM, inflammatory and osteoclastogenesis-promoting marker genes during mechanical strain.

Conclusions

Osteoarthritis-related ECM remodelling markers experience almost no changes in strain-induced gene expression, whereas inflammation and bone remodelling processes seem to differ depending on synovial fibroblast origin. Our data indicate that risk factors for the development and progression of osteoarthritis such as mechanical overuse have a different pathological impact in the TMJ compared to the knee joint.

Supplementary Information

The online version of this article (10.1007/s00056-021-00309-y) contains supplementary material, which is available to authorized users.

Dietary Salt Accelerates Orthodontic Tooth Movement by Increased Osteoclast Activity

Dietary salt uptake and inflammation promote sodium accumulation in tissues, thereby modulating cells like macrophages and fibroblasts. Previous studies showed salt effects on periodontal ligament fibroblasts and on bone metabolism by expression of nuclear factor of activated T-cells-5 (NFAT-5). Here, we investigated the impact of salt and NFAT-5 on osteoclast activity and orthodontic tooth movement (OTM). After treatment of osteoclasts without (NS) or with additional salt (HS), we analyzed gene expression and the release of tartrate-resistant acid phosphatase and calcium phosphate resorption. We kept wild-type mice and mice lacking NFAT-5 in myeloid cells either on a low, normal or high salt diet and inserted an elastic band between the first and second molar to induce OTM. We analyzed the expression of genes involved in bone metabolism, periodontal bone loss, OTM and bone density. Osteoclast activity was increased upon HS treatment. HS promoted periodontal bone loss and OTM and was associated with reduced bone density. Deletion of NFAT-5 led to increased osteoclast activity with NS, whereas we detected impaired OTM in mice. Dietary salt uptake seems to accelerate OTM and induce periodontal bone loss due to reduced bone density, which may be attributed to enhanced osteoclast activity. NFAT-5 influences this reaction to HS, as we detected impaired OTM and osteoclast activity upon deletion.

Role and Regulation of Mechanotransductive HIF-1α Stabilisation in Periodontal Ligament Fibroblasts

Orthodontic tooth movement (OTM) creates compressive and tensile strain in the periodontal ligament, causing circulation disorders. Hypoxia-inducible factor 1α (HIF-1α) has been shown to be primarily stabilised by compression, but not hypoxia in periodontal ligament fibroblasts (PDLF) during mechanical strain, which are key regulators of OTM. This study aimed to elucidate the role of heparan sulfate integrin interaction and downstream kinase phosphorylation for HIF-1α stabilisation under compressive and tensile strain and to which extent downstream synthesis of VEGF and prostaglandins is HIF-1α-dependent in a model of simulated OTM in PDLF. PDLF were subjected to compressive or tensile strain for 48 h. In various setups HIF-1α was experimentally stabilised (DMOG) or destabilised (YC-1) and mechanotransduction was inhibited by surfen and genistein. We found that HIF-1α was not stabilised by tensile, but rather by compressive strain. HIF-1α stabilisation had an inductive effect on prostaglandin and VEGF synthesis. As expected, HIF-1α destabilisation reduced VEGF expression, whereas prostaglandin synthesis was increased. Inhibition of integrin mechanotransduction via surfen or genistein prevented stabilisation of HIF-1α. A decrease in VEGF expression was observed, but not in prostaglandin synthesis. Stabilisation of HIF-1α via integrin mechanotransduction and downstream phosphorylation of kinases seems to be essential for the induction of VEGF, but not prostaglandin synthesis by PDLF during compressive (but not tensile) orthodontic strain.

A sprinkle of salt in the pressure cooker of innate immunity and inflammation

In this issue, Schroder et al. assess the impacts of mechanical strain and salt on macrophage inflammatory responses in vitro. They demonstrate a complex role for the transcription NFAT5 in cytokine release in response to stress, strain and salt in the context of orthodontic treatments.

A Human Periodontal Ligament Fibroblast Cell Line as a New Model to Study Periodontal Stress

The periodontal ligament (PDL) is exposed to different kinds of mechanical stresses such as bite force or orthodontic tooth movement. A simple and efficient model to study molecular responses to mechanical stress is the application of compressive force onto primary human periodontal ligament fibroblasts via glass disks. Yet, this model suffers from the need for primary cells from human donors which have a limited proliferative capacity. Here we show that an immortalized cell line, PDL-hTERT, derived from primary human periodontal ligament fibroblasts exhibits characteristic responses to glass disk-mediated compressive force resembling those of primary cells. These responses include induction and secretion of pro-inflammatory markers, changes in expression of extracellular matrix-reorganizing genes and induction of genes related to angiogenesis, osteoblastogenesis and osteoclastogenesis. The fact that PDL-hTERT cells can easily be transfected broadens their usefulness, as molecular gain- and loss-of-function studies become feasible.

Impact of salt and the osmoprotective transcription factor NFAT-5 on macrophages during mechanical strain

Myeloid cells regulate bone density in response to increased salt (NaCl) intake via the osmoprotective transcription factor, nuclear factor of activated T cells-5 (NFAT-5). Because orthodontic tooth movement (OTM) is a pseudoinflammatory immunological process, we investigated the influence of NaCl and NFAT-5 on the expression pattern of macrophages in a model of simulated OTM. RAW264.7 macrophages were exposed for 4 h to 2 g cm^-2 compressive or 16% tensile or no mechanical strain (control), with or without the addition of 40 mm NaCl. We analyzed the expression of inflammatory genes and proteins [tumor necrosis factor (TNF), interleukin (IL)-6 and prostaglandin endoperoxide synthase-2 (Ptgs-2)/prostaglandin E2 (PG-E2)] by real-time-quantitative PCR and ELISA. To investigate the role of NFAT-5 in these responses, NFAT-5 was both constitutively expressed and silenced. Salt and compressive strain, but not tensile strain increased the expression of NFAT-5 and most tested inflammatory factors in macrophages. NaCl induced the expression of Ptgs-2/PG-E2 and TNF, whereas secretion of IL-6 was inhibited. Similarly, a constitutive expression of NFAT-5 reduced IL-6 expression, while increasing Ptgs-2/PG-E2 and TNF expression. Silencing of NFAT-5 upregulated IL-6 and reduced Ptgs-2/PG-E2 and TNF expression. Salt had an impact on the expression profile of macrophages as a reaction to compressive and tensile strain that occur during OTM. This was mediated via NFAT-5, which surprisingly also seems to play a regulatory role in mechanotransduction of compressive strain. Sodium accumulation in the periodontal ligament caused by dietary salt consumption might propagate local osteoclastogenesis via increased local inflammation and thus OTM velocity, but possibly also entail side effects such as dental root resorptions or periodontal bone loss.

Effects of sodium chloride on the gene expression profile of periodontal ligament fibroblasts during tensile strain

Purpose

During orthodontic tooth movement, pressure and tension zones develop in the periodontal ligament, and periodontal ligament fibroblasts (PDLF) become exposed to mechanical strain. Enhanced salt (NaCl) concentrations are known to modulate responses of PDLF and immune cells to different stimuli like mechanical strain. Here, we investigated the impact of tensile strain on the gene expression profile of PDLF under normal (NS) and high salt (HS) conditions.

Methods

After preincubation under NS or HS (+40 mM NaCl in medium) conditions for 24 h, PDLF were stretched 16% for 48 h using custom-made spherical cap silicone stamps using an established and published setup. After determination of cell number and cytotoxicity, we analyzed expression of genes involved in extracellular matrix reorganization, angiogenesis, bone remodeling, and inflammation by quantitative real-time polymerase chain reaction (RT-qPCR).

Results

Tensile strain did not affect the expression of genes involved in angiogenesis or extracellular matrix reorganization by PDLF, which however modulate inflammatory responses and bone remodeling in reaction to 16% static tensile strain. Salt (NaCl) treatment triggered enhanced extracellular matrix formation, expression of cyclooxygenase 2 and bone metabolism in PDLF during tensile strain.

Conclusions

Salt (NaCl) consumption may influence orthodontic tooth movement and periodontal bone loss via modulation of extracellular matrix and bone metabolism. Excessive salt intake during orthodontic therapy may cause adverse effects regarding periodontal inflammation and bone resorption.