Macrophage polarization in periodontal ligament stem cells enhanced periodontal regeneration

Inducing the "re-development state" of periodontal ligament cells via tuning macrophage mediated immune microenvironment

INTRODUCTION

Periodontal regeneration, specifically the restoration of the cementum-periodontal ligament (PDL)-alveolar bone complex, remains a formidable challenge in the field of regenerative dentistry. In light of periodontal development, harnessing the multi-tissue developmental capabilities of periodontal ligament cells (PDLCs) and reinitiating the periodontal developmental process hold great promise as an effective strategy to foster the regeneration of the periodontal complex.

OBJECTIVES

This study aims to delve into the potential effects of the macrophage-mediated immune microenvironment on the "developmental engineering" regeneration strategy and its underlying molecular mechanisms.

METHODS

In this study, we conducted a comprehensive examination of the periodontium developmental process in the rat mandibular first molar using histological staining. Through the induction of diverse immune microenvironments in macrophages, we evaluated their potential effects on periodontal re-development events using a cytokine array. Additionally, we investigated PDLC-mediated periodontal re-development events under these distinct immune microenvironments through transcriptome sequencing and relevant functional assays. Furthermore, the underlying molecular mechanism was also performed.

RESULTS

The activation of development-related functions in PDLCs proved challenging due to their declined activity. However, our findings suggest that modulating the macrophage immune response can effectively regulate PDLCs-mediated periodontium development-related events. The M1 type macrophage immune microenvironment was found to promote PDLC activities associated with epithelial-mesenchymal transition, fiber degradation, osteoclastogenesis, and inflammation through the Wnt, IL-17, and TNF signaling pathways. Conversely, the M2 type macrophage immune microenvironment demonstrated superiority in inducing epithelium induction, fibers formation, and mineralization performance of PDLCs by upregulating the TGFβ and PI3K-Akt signaling pathway.

CONCLUSION

The results of this study could provide some favorable theoretical bases for applying periodontal development engineering strategy in resolving the difficulties in periodontal multi-tissue regeneration.

Membrane-anchoring selenophene viologens for antibacterial photodynamic therapy against periodontitis via restoring subgingival flora and alleviating inflammation

Antibacterial photodynamic therapy (aPDT) has emerged as a promising strategy for treating periodontitis. However, the weak binding of most photosensitizers to bacteria and the hypoxic environment of periodontal pockets severely hamper the therapeutic efficacy. Herein, two novel oxygen-independent photosensitizers are developed by introducing selenophene into viologens and modifying with hexane chains (HASeV) or quaternary ammonium chains (QASeV), which improve the adsorption to bacteria through anchoring to the negatively charged cell membrane. Notably, QASeV binds only to the bacterial surface of Porphyromonas gingivalis and Fusobacterium nucleatum due to electrostatic binding, but HASeV can insert into their membrane by strong hydrophobic interactions. Therefore, HASeV exhibits superior antimicrobial activity and more pronounced plaque biofilm disruption than QASeV when combined with light irradiation (MVL-210 photoreactor, 350-600 nm, 50 mW/cm2), and a better effect on reducing the diversity and restoring the structure of subgingival flora in periodontitis rat model was found through 16S rRNA gene sequencing analysis. The histological and Micro-CT analyses reveal that HASeV-based aPDT has a better therapeutic effect in reducing periodontal tissue inflammation and alveolar bone resorption. This work provides a new strategy for the development of viologen-based photosensitizers, which may be a favorable candidate for the aPDT against periodontitis.

Microbial- and host immune cell-derived extracellular vesicles in the pathogenesis and therapy of periodontitis: A narrative review

Periodontitis is a chronic inflammatory disease caused by dysbiotic biofilms and destructive host immune responses. Extracellular vesicles (EVs) are circulating nanoparticles released by microbes and host cells involved in cell-to-cell communication, found in body biofluids, such as saliva and gingival crevicular fluid (GCF). EVs are mainly involved in cell-to-cell communication, and may hold promise for diagnostic and therapeutic purposes. Periodontal research has examined the potential involvement of bacterial- and host-cell-derived EVs in disease pathogenesis, diagnosis, and therapy, but data remains scarce on immune cell- or microbial-derived EVs. In this narrative review, we first provide an overview of the role of microbial and host-derived EVs on disease pathogenesis. Recent studies reveal that Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans-derived outer membrane vesicles (OMVs) can activate inflammatory cytokine release in host cells, while M1 macrophage EVs may contribute to bone loss. Additionally, we summarised current in vitro and pre-clinical research on the utilisation of immune cell and microbial-derived EVs as potential therapeutic tools in the context of periodontal treatment. Studies indicate that EVs from M2 macrophages and dendritic cells promote bone regeneration in animal models. While bacterial EVs remain underexplored for periodontal therapy, preliminary research suggests that P. gingivalis OMVs hold promise as vaccine candidates. Finally, we acknowledge the current limitations present in the field of translating immune cell derived EVs and microbial derived EVs in periodontology. It is concluded that microbial and host immune cell-derived EVs have a role in periodontitis pathogenesis and hence may be useful for studying disease pathophysiology, and as diagnostic and treatment monitoring biomarkers.

Human Umbilical Cord Mesenchymal Stem Cells Promote Anti-Inflammation and Angiogenesis by Targeting Macrophages in a Rat Uterine Scar Model

BACKGROUND

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have demonstrated efficacy in repairing uterine scars, although the underlying mechanisms remain unclear.

METHODS

Uterine injury was surgically induced in a rat model, followed by immediate transplantation of 5 × 10 ^ 5 hUC-MSCs to each side of the uterus. Uterine morphology was evaluated at days 14 and 30 using HE and Masson staining. Immunohistochemistry assessed macrophage polarization, angiogenesis and endometrial receptivity in the endometrium. Additionally, the regulatory effects of hUC-MSCs on macrophage polarization were explored through coculture. qRT-PCR quantified the expression of anti-inflammatory (IL10 and Arg1) and pro-inflammatory (iNOS and TNF-α) factors. Western blotting evaluated CD163 expression.

RESULTS

Transplantation of hUC-MSCs promoted the healing of uterine injuries and tissue regeneration while inhibiting tissue fibrosis. Immunohistochemistry at days 14 and 30 post-transplantation demonstrated the polarization of macrophages toward the M2 phenotype in the uterine injury area in the presence of hUC-MSCs. Furthermore, hUC-MSC transplantation improved angiogenesis and endometrial receptivity in the uterine injury rat model, associated with increased IL10 expression. hUC-MSC-induced angiogenesis can be resisted by depleted macrophages. In vitro coculture experiments further demonstrated that hUC-MSCs promoted IL10 expression in macrophages while suppressing TNF-α and iNOS expression. Western blotting showed enhanced CD163 expression in macrophages following hUC-MSC treatment.

CONCLUSIONS

hUC-MSCs contribute to the healing of uterine injuries by targeting macrophages to promote angiogenesis and the expression of anti-inflammatory factors.

Emerging role of mesenchymal stem cell-derived extracellular vesicles in periodontal regeneration

Periodontitis is a prevalent oral ailment that harms both hard and soft tissues of the periodontium, leading to loosening and eventual removal of the teeth. Current clinical treatments have limitations in achieving complete periodontal tissue regeneration. Mesenchymal stem cells (MSCs) have garnered attention due to their unique characteristics and potential as a promising new therapy for periodontitis. Research suggests that the role of MSCs in regenerative medicine primarily occurs through the paracrine pathway, involving the emission of particles encased by lipids called extracellular vesicles (EVs) abundant in bioactive compounds. These EVs play a vital function in controlling the activities of periodontal tissues and immune system cells, and by influencing the immediate surrounding, thus fostering the healing of periodontal damage and renewal of tissues. EVs obtained from MSCs (MSC-EVs), in the form of a cell-free treatment, offer advantages in terms of stability, reduced immune rejection, and ethical considerations, elevating their potential as a hopeful choice for broad clinical applications. This concise overview highlights the mechanisms of MSC-EVs and the possibilities they hold in clinical application for periodontal regeneration.

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

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

Temporal and spatial effects on C-reactive protein's regulation of inducible nitric oxide synthase production in periodontal disease

BACKGROUND

Inducible nitric oxide synthase (iNOS) is associated with inflammation and osteoclastic differentiation in periodontal disease. This study was conducted to compare the time-dependent variation in iNOS production between the gingiva and other periodontal tissues and to explore the potential association with C-reactive protein (CRP) in early periodontal disease.

METHODS

Ligature-induced periodontal disease models (0-14 days) were established in wild-type and CRP knockout rats. Changes in CRP, iNOS, and autophagy levels were examined in the gingiva and other periodontal tissues. Macrophages were treated with lipopolysaccharide and chloroquine to explore the role of autophagy in iNOS production. iNOS, CRP, and autophagy-related proteins were analyzed using Western blotting, immunostaining, and enzyme-linked immunosorbent assays. mRNA expression was detected by quantitative real-time polymerase chain reaction. Hematoxylin and eosin staining was used for histological analysis. Cathepsin K immunostaining and microcomputed tomography of the maxillae were performed to compare alveolar bone resorption.

RESULTS

iNOS and CRP levels increased rapidly in periodontal tissues, as observed on Day 2 of ligature, then decreased more rapidly in the gingiva than in other periodontal tissues. CRP deficiency did not prevent iNOS generation, but effectively accelerated iNOS reduction and delayed alveolar bone loss. The CRP effect on iNOS was accompanied by a change in autophagy, which was reduced by CRP knockout.

CONCLUSIONS

The regulation of iNOS by CRP shows temporospatial variation in early periodontal disease and is potentially associated with autophagy. These findings may contribute to the early detection and targeted treatment of periodontal disease.

Periodontal Ligament Stem Cell-Derived Exosomes Regulate Muc5ac Expression in Rat Conjunctival Goblet Cells via Regulating Macrophages Toward an Anti-Inflammatory Phenotype

BACKGROUND

Several studies have reported the protective effects of mesenchymal stem cell-derived exosomes (MSC-Exos) in reducing inflammation and decreasing conjunctival goblet cell (CGC) loss in dry eye disease. However, whether MSC-Exos provide anti-inflammatory profiles in macrophages, thus contributing to CGC protection, has remained elusive.

METHODS

Macrophages were incubated with PKH26-labeled periodontal ligament mesenchymal stem cell-derived exosomes (PDLSC-Exos) for 12 h, and uptake of PDLSC-Exos by macrophages was observed by a confocal fluorescence microscope. The mRNA expression of TNF-α, IL-10, and Arg1 was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein expression of TNF-α and IL-10 were quantified using western blotting. Then, CGCs were exposed to different macrophage supernatants and qRT-PCR was used to detect the Muc5ac mRNA expression of CGCs in response to or absence of cholinergic stimulation. ELISA was used to determine the Muc5ac secretion of CGCs in response to cholinergic stimulation.

RESULTS

The uptake of PDLSC-Exos by M1 macrophages facilitates M2 macrophage polarization with the elevated expressions of IL-10 and Arg1. In macrophage supernatant-treated CGCs systems, PDLSC-Exo-treated M1 macrophage supernatant significantly enhanced the Muc5ac expression of CGCs in response to, or in the absence of, cholinergic stimulation, while the addition of PDLSC-Exos to the control macrophage supernatant did not generate a change in Muc5ac expression. Conversely, the addition of PDLSC-Exos to the diluted control macrophage supernatant induced a significant increase in Muc5ac expression.

CONCLUSION

PDLSC-Exos could protect CGCs against M1 macrophage-mediated inflammation, and the protective effects of PDLSC-Exos are partly attributable to their effects on M1 macrophages.

Exosomal circ_0000722 derived from periodontal ligament stem cells undergoing osteogenic differentiation promotes osteoclastogenesis

Periodontal ligament stem cells (PDLSCs), which are considered promising stem cells for regeneration of periodontal bony tissue, can also manipulate alveolar bone remodeling by exosomes. In this study, we investigated interactions between PDLSCs under osteogenic differentiation and osteoclast precursors. The results showed that conditioned medium from PDLSCs under 5d osteogenic induction promoted osteoclastogenesis of RAW264.7 cells. The exosomes extracted from those conditioned media showed similar effects on osteoclastogenesis. Furthermore, exosomes from PDLSCs under 5d of osteogenic induction showed significantly high expression of circ_0000722, compared with exosomes from PDLSCs before osteogenic induction. Downregulation of circ_0000722 significantly attenuated the effect of PDLSC-derived exosomes on the osteoclastogenesis of RAW264.7 cells. Our findings suggested that exosomal circ_0000722 derived from periodontal ligament stem cells undergoing osteogenic differentiation might promote osteoclastogenesis by upregulating TRAF6 expression and activating downstream NF-κB and AKT signaling pathways.

Mesenchymal Stromal Cells Derived from Dental Tissues: Immunomodulatory Properties and Clinical Potential

Mesenchymal stem/stromal cells (MSCs) are multipotent cells located in different areas of the human body. The oral cavity is considered a potential source of MSCs because they have been identified in several dental tissues (D-MSCs). Clinical trials in which cells from these sources were used have shown that they are effective and safe as treatments for tissue regeneration. Importantly, immunoregulatory capacity has been observed in all of these populations; however, this function may vary among the different types of MSCs. Since this property is of clinical interest for cell therapy protocols, it is relevant to analyze the differences in immunoregulatory capacity, as well as the mechanisms used by each type of MSC. Interestingly, D-MSCs are the most suitable source for regenerating mineralized tissues in the oral region. Furthermore, the clinical potential of D-MSCs is supported due to their adequate capacity for proliferation, migration, and differentiation. There is also evidence for their potential application in protocols against autoimmune diseases and other inflammatory conditions due to their immunosuppressive capacity. Therefore, in this review, the immunoregulatory mechanisms identified at the preclinical level in combination with the different types of MSCs found in dental tissues are described, in addition to a description of the clinical trials in which MSCs from these sources have been applied.

Resveratrol modulates the inflammatory response in hPDLSCs via the NRF2/HO-1 and NF-κB pathways and promotes osteogenic differentiation

OBJECTIVE

The purpose of this study was to investigate resveratrol's specific role as an anti-inflammatory and osteogenic differentiation of hPDLSCs in periodontitis and to reveal the mechanisms involved.

BACKGROUND

Numerous studies have shown that inhibiting the inflammatory response of periodontal tissues and promoting the regeneration of alveolar bone are crucial treatments for periodontitis. Resveratrol has been found to have certain anti-inflammatory property. However, the anti-inflammatory mechanism and osteogenic effect of resveratrol in periodontitis are poorly understood.

MATERIALS AND METHODS

We constructed an in vitro periodontitis model by LPS stimulation of hPDLSCs and performed WB, RT-qPCR, and immunofluorescence to analyze inflammatory factors and related pathways. In addition, we explored the osteogenic ability of resveratrol in in vitro models.

RESULTS

In vitro, resveratrol ameliorated the inflammatory response associated with activation of the NF-κB pathway through activation of the NRF2/HO-1 pathway, characterized by inhibition of p65/p50 nuclear translocation and the proinflammatory cytokines interleukin-1β levels. Resveratrol also has a positive effect on osteogenic differentiation.

CONCLUSIONS

Observations suggest that resveratrol modulates the inflammatory response in hPDLSCs via the NRF2/HO-1 and NF-κB pathways and promotes osteogenic differentiation.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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

AIM OF THE STUDY

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

METHODS

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

RESULTS

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

CONCLUSION

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

Exosomes and exosome composite scaffolds in periodontal tissue engineering

Promoting complete periodontal regeneration of damaged periodontal tissues, including dental cementum, periodontal ligament, and alveolar bone, is one of the challenges in the treatment of periodontitis. Therefore, it is urgent to explore new treatment strategies for periodontitis. Exosomes generated from stem cells are now a promising alternative to stem cell therapy, with therapeutic results comparable to those of their blast cells. It has great potential in regulating immune function, inflammation, microbiota, and tissue regeneration and has shown good effects in periodontal tissue regeneration. In addition, periodontal tissue engineering combines exosomes with biomaterial scaffolds to maximize the therapeutic advantages of exosomes. Therefore, this article reviews the progress, challenges, and prospects of exosome and exosome-loaded composite scaffolds in periodontal regeneration.

The Genetic Aspects of Periodontitis Pathogenesis and the Regenerative Properties of Stem Cells

Periodontitis (PD) is a prevalent and chronic inflammatory disease with a complex pathogenesis, and it is associated with the presence of specific pathogens, such as Porphyromonas gingivalis. Dysbiosis and dysregulated immune responses ultimately lead to chronic inflammation as well as tooth and alveolar bone loss. Multiple studies have demonstrated that genetic polymorphisms may increase the susceptibility to PD. Furthermore, gene expression is modulated by various epigenetic mechanisms, such as DNA methylation, histone modifications, or the activity of non-coding RNA. These processes can also be induced by PD-associated pathogens. In this review, we try to summarize the genetic processes that are implicated in the pathogenesis of PD. Furthermore, we discuss the use of these mechanisms in diagnosis and therapeutic purposes. Importantly, novel treatment methods that could promote tissue regeneration are greatly needed in PD. In this paper, we also demonstrate current evidence on the potential use of stem cells and extracellular vesicles to stimulate tissue regeneration and suppress inflammation. The understanding of the molecular mechanisms involved in the pathogenesis of PD, as well as the impact of PD-associated bacteria and stem cells in these processes, may enhance future research and ultimately improve long-term treatment outcomes.

Nicotine destructs dental stem cell-based periodontal tissue regeneration

Background/purpose

Nicotine is a widely known addictive and toxic substance in cigarette that exacerbates periodontitis. However, its deleterious effects on dental stem cells and subsequent implications in tissue regeneration remain unclear. This study aimed to explore the effects of nicotine on the regenerative capacity of human periodontal ligament stem cells (hPDLSCs) based on transcriptomics and proteomics, and determined possible targeted genes associated with smoking-related periodontitis.

Materials and methods

hPDLSCs were treated with different concentrations of nicotine ranging from 10-3 to 10-8 M. Transcriptomics and proteomics were performed and confirmed employing Western blot, 5-ethynyl-2'-deoxyuridine (EdU), and alkaline phosphatase (ALP) staining. A ligature-induced periodontitis mouse model was established and administrated with nicotine (16.2 μg/10 μL) via gingival sulcus. The bone resorption was assessed by micro-computed tomography and histological staining. Key genes were identified using multi-omics analysis with verifications in hPDLSCs and human periodontal tissues.

Results

Based on enrichments analysis, nicotine-treated hPDLSCs exhibited decreased proliferation and differentiation abilities. Local administration of nicotine in mouse model significantly aggravated bone resorption and undermined periodontal tissue regeneration by inhibiting the endogenous dental stem cells regenerative ability. HMGCS1, GPNMB, and CHRNA7 were hub-genes according to the network analysis and corelated with proliferation and differentiation capabilities, which were also verified in both cells and tissues.

Conclusion

Our study investigated the destructive effects of nicotine on the regeneration of periodontal tissues from aspects of in vitro and in vivo with the supporting information from both transcriptome and proteome, providing novel targets into the molecular mechanisms of smoking-related periodontitis.

Osteogenic Differentiation of Human Periodontal Ligament Stromal Cells Influences Their Immunosuppressive Potential toward Allogenic CD4+ T Cells

The differentiation ability of human periodontal ligament mesenchymal stromal cells (hPDL-MSCs) in vivo is limited; therefore, some studies considered strategies involving their pre-differentiation in vitro. However, it is not known how the differentiation of hPDL-MSCs influences their immunomodulatory properties. This study investigated how osteogenic differentiation of hPDL-MSCs affects their ability to suppress CD4+ T-lymphocyte proliferation. hPDL-MSCs were cultured for 21 days in osteogenic differentiation or standard culture media. Allogeneic CD4+ T lymphocytes were co-cultured with undifferentiated and differentiated cells in the presence or absence of interferon (IFN)-γ, interleukin (IL)-1β or tumor necrosis factor (TNF)-α, and their proliferation and apoptosis were measured. Additionally, the effects of these cytokines on the expression of immunomodulatory or pro-inflammatory factors were investigated. Our data show that osteogenic differentiation of hPDL-MSCs reduced their ability to suppress the proliferation of CD4+ T lymphocytes in the presence of IFN-γ and enhanced this ability in the presence of IL-1β. These changes were accompanied by a slightly decreased proportion of apoptotic CD4+ in the presence of IFN-γ. The osteogenic differentiation was accompanied by decreases and increases in the activity of indoleamine-2,3-dioxygenase in the presence of IFN-γ and IL-1β, respectively. The basal production of interleukin-8 by hPDL-MSCs was substantially increased upon osteogenic differentiation. In conclusion, this study suggests that pre-differentiation strategies in vitro may impact the immunomodulatory properties of hPDL-MSCs and subsequently affect their therapeutic effectiveness in vivo. These findings provide important insights for the development of MSC-based therapies.

Alterations in macrophage polarization play a key role in control and development of periodontal diseases

Periodontitis is a chronic inflammatory disease driven by complex interplays between a dysbiotic oral microbiome and a dysregulated host inflammatory response that results in the destruction of the tooth-supporting apparatus. Among the inflammatory cells involved in the pathogenesis of periodontitis, macrophages are recruited early on to sites of periodontal infection. These cells can polarize in different phenotypes that mediate the initiation and resolution of inflammatory responses, as well as in tissue healing. Macrophage phenotypic plasticity is thought to play a critical role in the induction and resolution of inflammation and may be compromised in patients with chronic inflammatory diseases. Here, we reviewed the role of macrophage polarization in periodontal disease and therapy.

Dental pulp stem cells accelerate wound healing through CCL2-induced M2 macrophages polarization

The crosstalk between mesenchymal stem cells (MSCs) and the host immune function plays a key role in the efficiency of tissue regeneration and wound healing. However, the difference in immunological modulation and tissue regeneration function between MSCs from different sources remains unclear. Compared to PDLSCs, BMMSCs, and ADSCs, DPSCs exhibited greater tissue regeneration potential and triggered more M2 macrophages in vivo. DPSCs elicited the polarization of M2a macrophages by conditioned medium and transwell assay and exhibited higher expression levels of C-C motif chemokine ligand 2 (CCL2). Specific blocking of CCL2 could significantly inhibit the DPSCs-induced polarization of M2 macrophages. DPSCs promoted wound healing of the palatal mucosa and M2 macrophages polarization in vivo, which could be significantly impaired by CCL2-neutralized antibody. Our data indicate that DPSCs exert better tissue regeneration potential and immunoregulatory function by secreting CCL2, which can enhance MSCs-mediated tissue regeneration or wound healing.

Bacterial growth stage determines the yields, protein composition, and periodontal pathogenicity of Porphyromonas gingivalis outer membrane vesicles

Introduction

P. gingivalis (W83), as the keystone pathogen in chronic periodontitis, has been found to be tightly bound to systemic diseases. Outer membrane vesicles (OMVs) produced by P. gingivalis (W83) are thought to serve key functions in bacterial virulence and pathogenicity. This study aims to comprehend the biological functions of P. gingivalis OMVs isolated from different growth stages by comparing their physicochemical properties and pathogenicity.

Methods

Protein composition was analyzed via isotope-labeled relative and absolute quantification (iTRAQ). Macrophage polarization and the expression of IL-6 and IL-1β were detected. The proliferation, migration, osteogenic differentiation, and IL-1b/NLRP3 expression of periodontal ligament stem cells (PDLSCs) were evaluated. P. gingivalis/P. gingivalis OMVs-induced periodontal models were also constructed in Sprague Dawley rats.

Results

The protein composition of P. gingivalis OMVs isolated from different growth stages demonstrated obvious differences ranging from 25 KDa to 75 KDa. In the results of flow cytometry, we found that in vitro experiments the M1 subtype of macrophages was more abundant in the late-log OMVs and stationary OMVs groups which boosted the production of inflammatory cytokines more than pre-log OMVs. Compared to pre-log OMVs, late-log OMVs and stationary OMVs had more pronounced inhibitory effects on proliferation, migration, and early osteogenesis of PDLSCs. The NLRP3 inflammasome was activated to a larger extent in the stationary OMVs group. Micro-computed tomography (Micro CT), hematoxylin-eosin staining (HE), and tartrate acid phosphatase (TRAP) results showed that the periodontal damage in the stationary OMVs group was worse than that in the pre-log OMVs and late-log OMVs group, but almost equal to that in the positive control group (P. gingivalis).

Discussion

In general, both in vivo and in vitro experiments showed that late-log OMVs and stationary OMVs have more significant pathogenicity in periodontal disease.

Enhanced Anti-inflammatory Capacity of the Conditioned Medium Derived from Periodontal Ligament Stem Cells Modified with an Iron-Based Nanodrug

Cell-free therapy using conditioned medium (CM) from mesenchymal stem cells takes full advantage of the bioactive factors secreted by the cells while avoiding disadvantages such as immune rejection and tumor formation due to cell transplantation. In this study, human periodontal ligament stem cells (PDLSCs) are modified with the superparamagnetic iron oxide nanoparticle (SPION)-based nanodrug ferumoxytol (PDLSC-SPION). Compared with PDLSCs, PDLSC-SPION showed good cell viability and better osteogenic differentiation ability. Cell-free CM is collected and the anti-inflammatory capacity of PDLSC CM and PDLSC-SPION CM is assessed by treatment of lipopolysaccharide-stimulated macrophages and IL-17-stimulated human gingival fibroblasts. Both CMs inhibited the expression of proinflammatory cytokines in cells, and the therapeutic effect is more distinct for PDLSC-SPION CM than PDLSC CM, which may be due to their different proteomic compositions. Therefore, modification of PDLSCs with ferumoxytol enhances the anti-inflammatory capacity of its CM, making it more potentially useful for the treatment of inflammatory diseases such as periodontitis.

Osteogenic induction of asiatic acid derivatives in human periodontal ligament stem cells

Asiatic acid (AA) and asiaticoside, pentacyclic triterpenoid compounds derived from Centella asiatica, are known for their biological effects in promoting type I collagen synthesis and inducing osteogenesis of stem cells. However, their applications in regenerative medicine are limited due to their low potency and poor aqueous solubility. This work aimed to evaluate the osteogenic induction activity of AA derivatives in human periodontal ligament stem cells (hPDLSCs) in vitro. Four compounds were synthesised, namely 501, 502, 503, and 506. AA was used as the control. The 502 exhibited low water solubility, while the 506 compound showed the highest. The cytotoxicity analysis demonstrated that 503 caused significant deterioration in cell viability, while other derivatives showed no harmful effect on hPDLSCs. The dimethyl aminopropyl amine derivative of AA, compound 506, demonstrated a relatively high potency in inducing osteogenic differentiation. An elevated mRNA expression of osteogenic-related genes, BMP2, WNT3A, ALP, OSX and IBSP was observed with 506. Additionally, the expression of BMP-2 protein was enhanced with increasing dose of 506, and the effect was pronounced when the Erk signalling molecule was inhibited. The 506 derivative was proposed for the promotion of osteogenic differentiation in hPDLSCs by upregulating BMP2 via the Erk signalling pathway. The 506 molecule showed promise in bone tissue regeneration.

Histological evaluation of mouse tongue incisions after Er:YAG laser surgery with different pulse energies versus after conventional scalpel surgery

PURPOSE

To identify the surgical instrument that allows for optimal healing of tongue incisions.

METHODS

An Er:YAG laser was compared with different pulse energies to a conventional scalpel for the incision of mouse tongue tissues. Mice were sacrificed through cervical dislocation at 24, 48, and 72 h postoperatively, followed by extraction of their tongues for incision experiments. The healing of the incisions and expression of inflammation- and pain-related factors in the tongues were compared between the surgical procedure groups.

RESULTS

In laser-treated mice, tongue incisions healed the fastest when the laser output energy was 60 MJ per pulse. Macrophage chemotaxis toward the incisional area was triggered on the first postoperative day for the 60-MJ group, while the time for macrophage chemotaxis to the surgical area was later in the 80-MJ group. Tumor necrosis factor-alpha expression increased and then decreased in the 80-MJ group; however, it gradually decreased in the 60-MJ and conventional scalpel groups. Prostaglandin E2 expression increased and then decreased in the 80-MJ and conventional scalpel groups but gradually decreased in the 60-MJ group. The expression of transforming growth factor beta 1 gradually decreased in the 60-MJ and 80-MJ groups but gradually increased in the conventional scalpel group.

CONCLUSION

Compared with surgical procedures using conventional scalpels, those using an Er:YAG laser with appropriate pulse energies can inhibit inflammation in the incisional area and promote incision healing. The use of an Er:YAG laser with appropriate pulse energies can alleviate intraoperative and postoperative pain in the incisional area.

Evaluation of Cytotoxicity of Calcium Silicate-based Mineral Trioxide Aggregate Sealers: A Systematic Review of In Vitro Studies

AIM

This review aimed to evaluate the in vitro studies done with regard to the cytotoxicity associated with mineral trioxide aggregate (MTA)-based root canal sealers.

BACKGROUND

Root canal sealers are used during endodontic treatment as fillers to seal the gaps between the canal gutta-percha cone and canal walls. It is necessary to understand the cytotoxicity of these materials on human-derived cells as these materials interact with human cells periapically.

REVIEW RESULTS

Six in vitro studies were chosen for review. In these selected studies, along with MTA-based root canal sealers, other sealers were tested for cytotoxicity on human periodontal ligament (PDL) stem cells, human PDL fibroblasts, and human osteoblast cells. Regarding cytotoxicity, the studies were diverse, and most were based on 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide) (MTT) assay. In general, the studies suggested that root canal sealers cause mild to severe cytotoxic effects and that several factors influence this effect, such as material setting time, concentration, and duration of exposure.

CONCLUSION

All studies in the review indicated that MTA. Fillapex must be used cautiously as it exhibited the highest cytotoxic effect compared to other MTA-based and non-MTA-based sealers.

CLINICAL SIGNIFICANCE

Endodontic sealers do serve the purpose of bridging the gaps between the gutta-percha cone and the canal wall but knowing its biocompatibility becomes important as the material is extruded beyond the apical foramen where it comes in contact with the surrounding tissues. The effect of sealers on the surrounding tissues affects the healing and prognosis of the treatment.

Clinical usage of dental stem cells and their derived extracellular vesicles

Stem cell-based therapies remain at the forefront of tissue engineering and regenerative medicine because stem cells are a unique cell source with enormous potential to treat incurable diseases and even extend lifespans. The search for the best stem cell candidates continues to evolve and in recent years, dental stem cells have received significant attention due to their easy accessibility, high plasticity, and multipotential properties. Dental stem cells have been the subject of extensive research in both animal models and human clinical trials over the past two decades, and have demonstrated significant potential in ocular therapy, bone tissue engineering, and, of course, therapeutic applications in dentistry such as regenerative endodontics and periodontal tissue regeneration. These new sources of cells may be advantageous for cellular therapy and the advancement of regenerative medicine strategies, such as allogeneic transplantation or therapy with extracellular vesicles (EVs), which are functional nanoscale membrane vesicles produced by cells. This chapter discusses the accumulating research findings on cell-based regenerative therapy utilizing dental stem cells and their derived EVs, which could be a viable tool for the treatment of a variety of diseases and hence extremely valuable to mankind in the long run.

Nanosilicate-functionalized nanofibrous membrane facilitated periodontal regeneration potential by harnessing periodontal ligament cell-mediated osteogenesis and immunomodulation

Although various new biomaterials have enriched the methods for periodontal regeneration, their efficacy is still controversial, and the regeneration of damaged support tissue in the periodontium remains challenging. Laponite (LAP) nanosilicate is a layered two-dimensional nanoscale, ultrathin nanomaterial with a unique structure and brilliant biocompatibility and bioactivity. This study aimed to investigate the effects of nanosilicate-incorporated PCL (PCL/LAP) nanofibrous membranes on periodontal ligament cells (PDLCs) in vitro and periodontal regeneration in vivo. A PCL/LAP nanofibrous membrane was fabricated by an electrospinning method. The characterization of PCL/LAP nanofibrous membrane were determined by scanning electron microscopy (SEM), energy dispersive spectrum of X-ray (EDS), inductively coupled plasma mass spectrometry (ICP-MS) and tensile test. The proliferation and osteogenic differentiation of PDLCs on the PCL/LAP nanofibrous membrane were evaluated. A PDLCs and macrophage coculture system was used to explore the immunomodulatory effects of the PCL/LAP nanofibrous membrane. PCL/LAP nanofibrous membrane was implanted into rat calvarial and periodontal defects, and the regenerative potential was evaluated by microcomputed topography (micro-CT) and histological analysis. The PCL/LAP nanofibrous membrane showed good biocompatibility and bioactivity. It enhanced the proliferation and osteogenic differentiation of PDLCs. The PCL/LAP nanofibrous membrane also stimulated anti-inflammatory and pro-remodeling N2 neutrophil formation, regulated inflammatory responses and induced M2 macrophage polarization by orchestrating the immunomodulatory effects of PDLCs. The PCL/LAP nanofibrous membrane promoted rat calvarial defect repair and periodontal regeneration in vivo. LAP nanosilicate-incorporated PCL membrane is capable of mediating osteogenesis and immunomodulation of PDLCs in vitro and accelerating periodontal regeneration in vivo. It could be a promising biomaterial for periodontal regeneration therapy.

Macrophages-bone marrow mesenchymal stem cells crosstalk in bone healing

Bone healing is associated with many orthopedic conditions, including fractures and osteonecrosis, arthritis, metabolic bone disease, tumors and periprosthetic particle-associated osteolysis. How to effectively promote bone healing has become a keen topic for researchers. The role of macrophages and bone marrow mesenchymal stem cells (BMSCs) in bone healing has gradually come to light with the development of the concept of osteoimmunity. Their interaction regulates the balance between inflammation and regeneration, and when the inflammatory response is over-excited, attenuated, or disturbed, it results in the failure of bone healing. Therefore, an in-depth understanding of the function of macrophages and bone marrow mesenchymal stem cells in bone regeneration and the relationship between the two could provide new directions to promote bone healing. This paper reviews the role of macrophages and bone marrow mesenchymal stem cells in bone healing and the mechanism and significance of their interaction. Several new therapeutic ideas for regulating the inflammatory response in bone healing by targeting macrophages and bone marrow mesenchymal stem cells crosstalk are also discussed.

Glycolytic reprogramming underlies immune cell activation by polyethylene wear particles

Primary total joint arthroplasties (TJAs) are widely and successfully applied reconstructive procedures to treat end-stage arthritis. Nearly 50 % of TJAs are now performed in young patients, posing a new challenge: performing TJAs which last a lifetime. The urgency is justified because subsequent TJAs are costlier and fraught with higher complication rates, not to mention the toll taken on patients and their families. Polyethylene particles, generated by wear at joint articulations, drive aseptic loosening by inciting insidious inflammation associated with surrounding bone loss. Down modulating polyethylene particle-induced inflammation enhances integration of implants to bone (osseointegration), preventing loosening. A promising immunomodulation strategy could leverage immune cell metabolism, however, the role of immunometabolism in polyethylene particle-induced inflammation is unknown. Our findings reveal that immune cells exposed to sterile or contaminated polyethylene particles show fundamentally altered metabolism, resulting in glycolytic reprogramming. Inhibiting glycolysis controlled inflammation, inducing a pro-regenerative phenotype that could enhance osseointegration.

Klotho enhances bone regenerative function of hPDLSCs via modulating immunoregulatory function and cell autophagy

BACKGROUND

Human periodontal ligament stem cells (hPDLSCs) have a superior ability to promote the formation of new bones and achieve tissue regeneration. However, mesenchymal stem cells (MSCs) are placed in harsh environments after transplantation, and the hostile microenvironment reduces their stemness and hinders their therapeutic effects. Klotho is an antiaging protein that participates in the regulation of stress resistance. In our previous study, we demonstrated the protective ability of Klotho in hPDLSCs.

METHODS

A cranial bone defect model of rats was constructed, and the hPDLSCs with or without Klotho pretreatment were transplanted into the defects. Histochemical staining and micro-computed tomography were used to detect cell survival, osteogenesis, and immunoregulatory effects of hPDLSCs after transplantation. The in vitro capacity of hPDLSCs was measured by a macrophage polarization test and the inflammatory level of macrophages. Furthermore, we explored autophagy activity in hPDLSCs, which may be affected by Klotho to regulate cell homeostasis.

RESULTS

Pretreatment with the recombinant human Klotho protein improved cell survival after hPDLSC transplantation and enhanced their ability to promote bone regeneration. Furthermore, Klotho pretreatment can promote stem cell immunomodulatory effects in macrophages and modulate cell autophagy activity, in vivo and in vitro.

CONCLUSION

These findings suggest that the Klotho protein protects hPDLSCs from stress after transplantation to maintain stem cell function via enhancing the immunomodulatory ability of hPDLSCs and inhibiting cell autophagy.

Unlocking the Potential of Dental-Derived Mesenchymal Stem Cells in Regenerative Medicine

Over the past few decades, life expectancy has been increasing in several countries [...].

Mesenchymal-Stromal-Cell-Conditioned Media and Their Implication for Osteochondral Regeneration

Despite significant advances in biomedical research, osteochondral defects resulting from injury, an autoimmune condition, cancer, or other pathological conditions still represent a significant medical problem. Even though there are several conservative and surgical treatment approaches, in many cases, they do not bring the expected results and further permanent damage to the cartilage and bones occurs. Recently, cell-based therapies and tissue engineering have gradually become promising alternatives. They combine the use of different types of cells and biomaterials to induce regeneration processes or replace damaged osteochondral tissue. One of the main challenges of this approach before clinical translation is the large-scale in vitro expansion of cells without changing their biological properties, while the use of conditioned media which contains various bioactive molecules appears to be very important. The presented manuscript provides a review of the experiments focused on osteochondral regeneration by using conditioned media. In particular, the effect on angiogenesis, tissue healing, paracrine signaling, and enhancing the properties of advanced materials are pointed out.

An altered oral microbiota induced by injections of superparamagnetic iron oxide nanoparticle-labeled periodontal ligament stem cells helps periodontal bone regeneration in rats

Stem cell injection is good for periodontal regeneration due to the capacity of stem cells to differentiate toward osteogenic direction and to regulate the production of pro- and anti-inflammatory cytokines. However, injected cells are difficult to track in vivo. And there is microbiota in oral cavity, the dysbiosis of which leads to the damage and loss of periodontal tissue. Here, we demonstrated an enhanced periodontal repair was due to an altered oral microbiota. Periodontal defects were surgically prepared in rats, and periodontal ligament stem cells (PDLSCs) labeled by superparamagnetic iron oxide (SPIO) nanoparticles (PC-SPIO) were injected, with PDLSCs and saline treatments as controls. Detected by magnetic resonance imaging (MRI) and histological staining, PC-SPIO was major at limited areas in regenerated periodontal tissues. PC-SPIO-treated rats achieved better periodontal regeneration than the other two groups. Concurrently, the oral microbiota of PC-SPIO-treated rats was changed, presenting SPIO-Lac as a biomarker. SPIO-Lac assisted periodontal repair in vivo, inhibited the inflammation of macrophages induced by lipopolysaccharide (LPS) and antibacterial in vitro. Therefore, our study proved that SPIO-labeled cells can be tracked in periodontal defect and highlighted a potential positive role of an oral microbiota in periodontal regeneration, suggesting the possibility of periodontal repair promotion by manipulating oral microbiota.

Immortalized cell lines derived from dental/odontogenic tissue

Stem cells derived from dental/odontogenic tissue have the property of multiple differentiation and are prospective in tooth regenerative medicine and cellular and molecular studies. However, in the face of cellular senescence soon in vitro, the proliferation ability of the cells is limited, so studies are hindered to some extent. Fortunately, immortalization strategies are expected to solve the above issues. Cellular immortalization is that cells are immortalized by introducing oncogenes, human telomerase reverse transcriptase genes (hTERT), or miscellaneous immortalization genes to get unlimited proliferation. At present, a variety of immortalized stem cells from dental/odontogenic tissue has been successfully generated, such as dental pulp stem cells (DPSCs), periodontal ligament cells (PDLs), stem cells from human exfoliated deciduous teeth (SHEDs), dental papilla cells (DPCs), and tooth germ mesenchymal cells (TGMCs). This review summarized establishment and applications of immortalized stem cells from dental/odontogenic tissues and then discussed the advantages and challenges of immortalization.

Leptin-deficient ob/ob mice exhibit periodontitis phenotype and altered oral microbiome

BACKGROUND AND OBJECTIVE

Leptin-deficient obesity is associated with various systemic diseases including diabetes and low bone mass phenotype. However, the periodontal status of leptin-deficient obese individuals is still unclear. In this study, we aimed to analyze the periodontal status, alveolar bone phenotype, and oral microbiome status in leptin-deficient obese mice (ob/ob mice).

METHODS

This study used 12-week-old wild-type and ob/ob male mice. The alveolar bone phenotype and periodontal status in the maxilla were analyzed by micro-CT and histological analysis. Osteoclasts in alveolar bone were visualized by TRAP staining. Expressions of inflammatory markers (MMP-9, IL-1β, and TGF-β1) and osteoclastogenic markers (RANKL and OPG) in periodontium were analyzed by immunohistochemistry and RT-qPCR. The oral microbiome was analyzed by 16 S rDNA sequencing.

RESULTS

CEJ-ABC distance in maxillary molars (M1-M3) of ob/ob mice was significantly higher compared with that of wild-type. The alveolar bone BV/TV ratio was reduced in ob/ob mice compared with wild-type. Higher numbers of osteoclasts were observed in ob/ob mice alveolar bone adjacent to the molar root. Epithelial hyperplasia in gingiva and disordered periodontal ligaments was observed in ob/ob mice. RANKL/OPG expression ratio was increased in ob/ob mice compared with wild-type. Expressions of inflammatory markers MMP-9, IL-1β, and TGF-β1 were increased in ob/ob mice compared with wild-type. Oral microbiome analysis showed that beneficial bacteria Akkermansia and Ruminococcaceae_UCG_014 were more abundant in the wild-type mice while the inflammation-related Flavobacterium was more abundant in ob/ob mice.

CONCLUSION

In conclusion, ob/ob mice showed higher expressions of inflammatory factors, increased alveolar bone loss, lower abundance of the beneficial bacteria, and higher abundance of inflammatory bacteria in the oral cavity, suggesting leptin-deficient obesity as a risk factor for periodontitis development in ob/ob mice.

Effect of Different Sealers on the Cytocompatibility and Osteogenic Potential of Human Periodontal Ligament Stem Cells: An In Vitro Study

Background: There is tendency for unavoidable sealer extrusion in some clinical cases. This might adversely affect host stem cells and affect healing. This study aimed to investigate the effect of different sealers on the cytocompatibility and osteogenic potential of human periodontal ligament stem cells (hPDLSCs). Methods: The cytotoxic effect of the extracted elutes of VDW.1Seal (VDW.1), Endosequence BC Sealer HiFlow (ES), GuttaFlow-2 (GF), and ADSeal (AD-S) on the hPDLSCs was determined using the MTT assay. Cell proliferation and migration were assessed by the scratch wound healing assay. Osteogenic differentiation potential was assessed. Measurement of pH values and calcium ions release was performed. Results: GF had a significantly higher percentage of viable cells. The cell migration assay showed that GF demonstrated the lowest open wound area percentage. GF and AD-S showed the highest calcium nodule deposition. GF demonstrated higher ALP activity than ES. Expression of RUNX2 and OC genes was similar for all sealers, while OPG gene expression was significantly higher for VDW.1 and GF. ES and AD-S displayed the highest pH values on day 1. Calcium ion release of ES and VDW.1 was significantly the highest. Conclusions: GuttaFlow-2 and VDW.1Seal sealers have favorable behavior toward host stem cells.

Conditioned media of deer antler stem cells accelerate regeneration of alveolar bone defects in rats

The destruction of periodontal alveolar bone (AB) caused by periodontitis is regarded as one of the major reasons for tooth loss. The inhibition of bone resorption and regeneration of lost AB are the desirable outcomes in clinical practice but remain in challenge. The use of mesenchymal stem cells (MSCs) is one current approach for achieving true restoration of AB defects (ABD). Antler stem cells (AnSC) are capable of renewing a huge mammalian bony appendage, the deer antler, suggesting an unparalleled potential for bone regeneration. Herein, we investigated the effectiveness of deer AnSCs conditioned medium (CM, AnSC-CM) for repair of surgically-created ABD using a rat model and sought to define the underlying mechanisms. The results showed that AnSC-CM effectively induced regeneration of AB tissue; the outcome was significantly better than human bone marrow mesenchymal stem cell conditioned medium (hBMSC-CM). AnSC-CM treatment upregulated osteogenic factors and downregulated osteoclastic differentiation factors; stimulated proliferation, migration and differentiation of resident MSCs toward osteogenic lineage cells; modulated macrophage polarization toward the M2 phenotype and suppressed osteoclastogenesis. That AnSC-CM resulted in better outcomes than hBMSC-CM in treating ABD was attributed to the cell compatibility as both AnSCs and AB tissue are neural crest-derived. In conclusion, the effects of AnSC-CM on AB tissue regeneration were achieved through both promotion of osteogenesis and inhibition of osteoclastogenesis. We believe that AnSC-CM is a candidate for effective treatment of ABD in dental clinical practice but will require investment in further development.

Highly efficient photothermal branched Au-Ag nanoparticles containing procyanidins for synergistic antibacterial and anti-inflammatory immunotherapy

Periodontitis is an inflammatory disease caused by bacterial infection. Excessive immune response and high levels of reactive oxygen species (ROS) further lead to the irreversible destruction of surrounding tissues. Developing new antimicrobial materials that regulate the immune system to resist inflammation can effectively treat periodontal inflammation. A nanoplatform integrating Ag⁺, photothermal therapy (PTT), and procyanidins (PC) for precision antibacterial and synergistic immunotherapy for periodontitis was proposed. This work loaded PC into AuAg nanoparticles, and the resulting nanocomposite was named AuAg-PC. PTT can effectively remove pathogenic bacteria, but high temperatures can cause tissue damage. Ag⁺ contributes to the preparation of a nanoparticle branched structure that improves the photothermal efficiency and helps PTT achieve an excellent antibacterial effect and avoid periodontal tissue damage. PC regulates host immunity by eliminating intracellular ROS, inhibiting inflammatory factors, and regulating macrophage polarisation in periodontal disease sites. It enhances the host's resistance to bacterial inflammation. AuAg-PC exerted an excellent anti-inflammatory effect and promoted tissue repair in animal periodontal inflammation models. Hence, AuAg-PC significantly combats periodontal pathogens and shows great application potential in the photothermal-assisted immunotherapy of periodontitis. This design provided a new controllable and efficient treatment platform for controlling persistent inflammation infection and regulating immunity.

Mechanisms and clinical application potential of mesenchymal stem cells-derived extracellular vesicles in periodontal regeneration

Periodontitis is a high prevalence oral disease which damages both the hard and soft tissue of the periodontium, resulting in tooth mobility and even loss. Existing clinical treatment methods cannot fully achieve periodontal tissue regeneration; thus, due to the unique characteristics of mesenchymal stem cells (MSCs), they have become the focus of attention and may be the most promising new therapy for periodontitis. Accumulating evidence supports the view that the role of MSCs in regenerative medicine is mainly achieved by the paracrine pathway rather than direct proliferation and differentiation at the injured site. Various cells release lipid-enclosed particles known as extracellular vesicles (EVs), which are rich in bioactive substances. In periodontitis, EVs play a pivotal role in regulating the biological functions of both periodontal tissue cells and immune cells, as well as the local microenvironment, thereby promoting periodontal injury repair and tissue regeneration. As a cell-free therapy, MSCs-derived extracellular vesicles (MSC-EVs) have some preponderance on stability, immune rejection, ethical supervision, and other problems; therefore, they may have a broad clinical application prospect. Herein, we gave a brief introduction to MSC-EVs and focused on their mechanisms and clinical application in periodontal regeneration.

Regulation of the Host Immune Microenvironment in Periodontitis and Periodontal Bone Remodeling

The periodontal immune microenvironment is a delicate regulatory system that involves a variety of host immune cells including neutrophils, macrophages, T cells, dendritic cells and mesenchymal stem cells. The dysfunction or overactivation of any kind of local cells, and eventually the imbalance of the entire molecular regulatory network, leads to periodontal inflammation and tissue destruction. In this review, the basic characteristics of various host cells in the periodontal immune microenvironment and the regulatory network mechanism of host cells involved in the pathogenesis of periodontitis and periodontal bone remodeling are summarized, with emphasis on the immune regulatory network that regulates the periodontal microenvironment and maintains a dynamic balance. Future strategies for the clinical treatment of periodontitis and periodontal tissue regeneration need to develop new targeted synergistic drugs and/or novel technologies to clarify the regulatory mechanism of the local microenvironment. This review aims to provide clues and a theoretical basis for future research in this field.

Macrophages contribute to periodontal wound healing mainly in the tissue proliferation stage

OBJECTIVE

The aim of this study was to determine the preliminary role of macrophages in different stages of periodontal healing.

BACKGROUND

Macrophages are promising target cells for periodontal regeneration. However, the stage at which they play a more important role during periodontal repair has not been elucidated till date.

METHODS

First, the dynamic changes in M1 and M2 macrophages were analyzed in a rat periodontal-defect model at Days 1, 3, 5, 7, 14, 21, and 28 post-surgery. Macrophages were then depleted after 1, 6, and 14 days of surgery, and the healing results were evaluated via micro-computed tomography and histopathological detection. Finally, the effects of M1 and M2 macrophages on the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) were verified in vitro.

RESULTS

During natural periodontal healing, the number of M1 macrophages increased the most during the early stage of healing (3 days post-operation), and subsequently, it decreased rapidly. The number of M2 macrophages was at its peak during the middle and late stages of tissue healing (5-21 days post-surgery). Interestingly, the highest number of M2 macrophages was observed at 5-14 days post-operation in the alveolar bone, while it was observed at 21 days post-operation in the cementum area. On the first and 14th day post-operation, the clearance of macrophages had no significant effect on tissue healing; however, on the sixth day post-operation, macrophage depletion significantly inhibited tissue regeneration (p < .05). In vitro studies showed that M2 macrophages, rather than M1 macrophages, could significantly promote the proliferation of MSCs (p < .01).

CONCLUSION

It is better to intervene in tissue proliferation phase when a M2 macrophage regulation-based periodontal regenerative therapy is planned in the future.

Dental pulp stem cells induce anti-inflammatory phenotypic transformation of macrophages to enhance osteogenic potential via IL-6/GP130/STAT3 signaling

Background

Periodontitis is a major oral condition and current treatment outcomes can be unsatisfactory. Macrophages are essential to the regeneration process, so we investigated the influence of human dental pulp stem cells (hDPSCs) on macrophage differentiation and the microenvironment and the underlying mechanism.

Methods

hDPSCs were isolated from healthy third molars extracted from patients undergoing maxillofacial surgery. The surface antigens CD73, CD45, CD90 and CD11b of the hDPSCs were detected using flow cytometry. hDPSCs were induced for osteogenic and adipogenic differentiation, and the outcome was assessed by alizarin red staining or Oil Red O staining. The IL-6 level released by hDPSCs was measured by enzyme linked immunosorbent assay (ELISA). Tohoku Hospital Pediatrics-1 (THP-1) cells were cultured and induced into macrophages by phorbol-12-myristate-13-acetate. After coculture of THP-1-derived macrophages with hDPSCs, interleukin 6 (IL-6), Argininase-1 (Arg-1), Mannose receptor C-1 (Mrc-1), inducible nitric oxide synthase (iNOS), and tumor necrosis factor-α (TNF-α) levels in the medium were measured using ELISA and quantificational RT-PCR (qRT-PCR). The numbers of CD80⁺ and CD163⁺ macrophages were counted by immunofluorescence, and GP130/STAT3 signaling protein expression was detected. After coculturing the culture medium of hDPSCs with human bone marrow stem cells (BMSCs), scratch assays and transwell assays were performed to evaluate cell migration and invasion.

Results

Alkaline phosphatase (ALP) staining, alizarin red staining, and western blots were performed to assess osteoblast differentiation. The hDPSCs were positive for surface antigens CD73 and CD90 and negative for CD45 and CD11b expression. The level of IL-6 secreted by hDPSCs significantly increased the number of CD80⁺ cells as well as the levels of Arg-1 and Mrc-1. It also promoted M2 macrophage polarization and activated GP130/STAT3 signaling. However, the medium cocultured with THP-1-derived macrophages by hDPSCs facilitated the migration, invasion, and osteogenic abilities of human bone marrow-derived stem cells (hBMSCs).

Conclusions

hDPSCs can regulate the periodontal microenvironment through IL-6 by inducing phenotypic transformation of M2 macrophages and stimulating osteogenic differentiation of BMSCs.

Bioactive Decellularized Tendon-Derived Stem Cell Sheet for Promoting Graft Healing After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Stem cell sheets provide a scaffold-free option for the promotion of graft healing after anterior cruciate ligament reconstruction (ACLR). However, cell viability, stability, and potential uncontrolled actions create challenges for clinical translation. The decellularization of cell sheets may overcome these problems as studies have shown that the natural extracellular matrix of stem cells is bioactive and can promote tissue repair.

HYPOTHESIS

The decellularized tendon-derived stem cell (dTDSC) sheet can promote graft healing after ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

An optimized decellularization protocol was developed to decellularize the TDSC sheets. A total of 64 Sprague-Dawley rats underwent ACLR with or without the dTDSC sheet wrapping the tendon graft (n = 32/group). At 2 and 6 weeks after surgery, graft healing was assessed by micro-computed tomography, histology, and biomechanical testing. The accumulation of iNOS⁺ and CD206⁺ cells and the expression of metalloproteinase 1 (MMP-1), MMP-13, and tissue inhibitor of metalloprotease 1 (TIMP-1) were assessed by immunohistochemistry.

RESULTS

The decellularization was successful, with the removal of 98.4% nucleic acid while preserving the collagenous proteins and bioactive factors. The expression of bone morphogenetic protein 2 (BMP-2) and VEGF in the dTDSC sheet was comparable with the TDSC sheet (P > .05). Micro-computed tomography showed significantly more tunnel bone formation in the dTDSC sheet group. The dTDSC sheet group demonstrated better graft osteointegration and higher integrity of graft midsubstance with significantly higher ultimate failure load (16.58 ± 7.24 vs 8.93 ± 2.45 N; P = .002) and stiffness (11.97 ± 5.21 vs 6.73 ± 2.20 N/mm; P = .027). Significantly fewer iNOS⁺ cells but more CD206⁺ cells, as well as lower MMP-1 and MMP-13 but higher TIMP-1 expression, were detected at the tendon-bone interface and graft midsubstance in the dTDSC sheet group.

CONCLUSION

An optimized decellularization protocol for producing bioactive dTDSC sheets was developed. Wrapping tendon graft with a dTDSC sheet promoted graft healing after ACLR, likely via enhancing bone formation and angiogenesis by BMP-2 and VEGF, modulating macrophage polarization and MMP/TIMP expression, and physically protecting the tendon graft.

CLINICAL RELEVANCE

dTDSC sheets alleviate the quality control and safety concerns of cell transplantation and can be used as a cell-free alternative for the promotion of graft healing in ACLR.

Comprehensive analysis of M2 macrophage-derived exosomes facilitating osteogenic differentiation of human periodontal ligament stem cells

BACKGROUND

The role of periodontal ligament stem cells (PDLSCs) and macrophage polarization in periodontal tissue regeneration and bone remodeling during orthodontic tooth movement (OTM) has been well documented. Nevertheless, the interactions between macrophages and PDLSCs in OTM remain to be investigated. Consequently, the present study was proposed to explore the effect of different polarization states of macrophages on the osteogenic differentiation of PDLSCs.

METHODS

After M0, M1 and M2 macrophage-derived exosomes (M0-exo, M1-exo and M2-exo) treatment of primary cultured human PDLSCs, respectively, mineralized nodules were observed by Alizarin red S staining, and the expression of ALP and OCN mRNA and protein were detected by RT-qPCR and Western blotting, correspondingly. Identification of differentially expressed microRNAs (DE-miRNA) in M0-exo and M2-exo by miRNA microarray, and GO and KEGG enrichment analysis of DE-miRNA targets, and construction of protein-protein interaction networks.

RESULTS

M2-exo augmented mineralized nodule formation and upregulated ALP and OCN expression in PDLSCs, while M0-exo had no significant effect. Compared to M0-exo, a total of 52 DE-miRNAs were identified in M2-exo. The expression of hsa-miR-6507-3p, hsa-miR-4731-3p, hsa-miR-4728-3p, hsa-miR-3614-5p and hsa-miR-6785-3p was significantly down-regulated, and the expression of hsa-miR-6085, hsa-miR-4800-5p, hsa-miR-4778-5p, hsa-miR-6780b-5p and hsa-miR-1227-5p was significantly up-regulated in M2-exo compared to M0-exo. GO and KEGG enrichment analysis revealed that the downstream targets of DE-miRNAs were mainly involved in the differentiation and migration of multiple cells.

CONCLUSIONS

In summary, we have indicated for the first time that M2-exo can promote osteogenic differentiation of human PDLSCs, and have revealed the functions and pathways involved in the DE-miRNAs of M0-exo and M2-exo and their downstream targets.

A Novel Perspective on Tissue Engineering Potentials of Periodontal Ligament Stem Cells

It is challenging to completely and predictably regenerate the missing periodontal tissues caused by the trauma or disease. To regenerate the periodontium, there is a need to consider several aspects that co-occur with periodontal development. This study provides an overview of the most up-to-date investigations on the characteristics and immunomodulatory features of Periodontal Ligament Stem Cells (PDLSCs) and the recent interventions performed using these cells, focusing on cell survival, proliferation, and differentiation. Keeping in mind the relationship between age and potency of PDLSCs, this work also demonstrates the necessity of establishing dental-derived stem cell banks for tissue regeneration applications. The data were collected from Pubmed and Google Scholar databases with the keywords of periodontal ligament stem cells, tissue engineering, characteristics, and stem cell therapy. The results showed the presence of wide-ranging research reports supporting the usability of PDLSCs for periodontal reconstruction. However, a better understanding of self-restoration for adequate regulation of adult stem cell growth is needed for various applied purposes.

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.

Advances in novel therapeutic approaches for periodontal diseases

Periodontal diseases are pathological processes resulting from infections and inflammation affecting the periodontium or the tissue surrounding and supporting the teeth. Pathogenic bacteria living in complex biofilms initiate and perpetuate this disease in susceptible hosts. In some cases, broad-spectrum antibiotic therapy has been a treatment of choice to control bacterial infection. However, increasing antibiotic resistance among periodontal pathogens has become a significant challenge when treating periodontal diseases. Thanks to the improved understanding of the pathogenesis of periodontal disease, which involves the host immune response, and the importance of the human microbiome, the primary goal of periodontal therapy has shifted, in recent years, to the restoration of homeostasis in oral microbiota and its harmonious balance with the host periodontal tissues. This shift in therapeutic goals and the drug resistance challenge call for alternative approaches to antibiotic therapy that indiscriminately eliminate harmful or beneficial bacteria. In this review, we summarize the recent advancement of alternative methods and new compounds that offer promising potential for the treatment and prevention of periodontal disease. Agents that target biofilm formation, bacterial quorum-sensing systems and other virulence factors have been reviewed. New and exciting microbiome approaches, such as oral microbiota replacement therapy and probiotic therapy for periodontal disease, are also discussed.

Investigation of macrophage polarization in herniated nucleus pulposus of patients with lumbar intervertebral disc herniation

Macrophage infiltration and polarization during lumbar intervertebral disc herniation (LDH) have attracted increased attention but their role remains unclear. To explore macrophage polarization in herniated nucleus pulposus (NP) tissue of patients with LDH and investigate the association between cell frequency and different clinical characteristics or symptoms, we conducted a retrospective study by analyzing NP tissue samples from 79 patients. Clinical features and symptoms, using the visual analog scale (VAS) and Oswestry disability index (ODI), were collected. The macrophage markers CD68, CCR7, CD163, and CD206; pro-inflammatory cytokine TNF-α; and anti-inflammatory factor IL-4 were analyzed by immunohistochemistry. The frequency of polarized macrophages and positivity rate of pro- and anti-inflammatory cytokines showed significant differences in some of clinical characteristics. Specifically, higher CCR7⁺ and TNF-α + proportions were identified in the high-intensity zone (HIZ) and the type of extrusion and sequestration NP tissue than in non-HIZ and protrude NP tissue. Higher CD206⁺ and IL-4+ proportion were detected in Modic changes. However, no differences in gender, age, smoking status, Pfirrmann grade, analgesic use, leg pain duration, and segments were found between groups. CD68⁺ , CCR7⁺ , and CD206⁺ cell proportions, and TNF-α and IL-4 showed positive associations with VAS scores preoperation. Associations between ODI and the macrophages markers were weak/insignificant. Our results indicated that macrophage polarization or macrophage-like cells contribute to LDH pathological features. Macrophage populations displaying significant associations with VAS score reflected continuous M1/M2 transition contributing to pain during LDH. These findings may contribute to enhanced/personalized pharmacological interventions for patients with LDH considering pain heterogeneity.

Immune senescence and periodontitis: From mechanism to therapy

Periodontitis is one of the most prevalent infectious inflammatory diseases, characterized by irreversible destruction of the supporting tissues of teeth, which is correlated with a greater risk of multiple systemic diseases, thus regarded as a major health concern. Dysregulation between periodontal microbial community and host immunity is considered to be the leading cause of periodontitis. Comprehensive studies have unveiled the double-edged role of immune response in the development of periodontitis. Immune senescence, which is described as age-related alterations in immune system, including a diminished immune response to endogenous and exogenous stimuli, a decline in the efficiency of immune protection, and even failure in immunity build-up after vaccination, leads to the increased susceptibility to infection. Recently, the intimate relationship between immune senescence and periodontitis has come into focus, especially in the aging population. In this review, both periodontal immunity and immune senescence will be fully introduced, especially their roles in the pathology and progression of periodontitis. Furthermore, novel immunotherapies targeting immune senescence are presented to provide potential targets for research and clinical intervention in the future.