Periodontal ligament-derived mesenchymal stem cells modulate neutrophil responses via paracrine mechanisms

Stem cell therapies: a new era in the treatment of multiple sclerosis

Multiple Sclerosis (MS) is an immune-mediated condition that persistently harms the central nervous system. While existing treatments can slow its course, a cure remains elusive. Stem cell therapy has gained attention as a promising approach, offering new perspectives with its regenerative and immunomodulatory properties. This article reviews the application of stem cells in MS, encompassing various stem cell types, therapeutic potential mechanisms, preclinical explorations, clinical research advancements, safety profiles of clinical applications, as well as limitations and challenges, aiming to provide new insights into the treatment research for MS.

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.

METTL3-Mediated m6A Modification Regulates the Osteogenic Differentiation through LncRNA CUTALP in Periodontal Mesenchymal Stem Cells of Periodontitis Patients

Objective

Periodontitis is a chronic inflammatory disease that causes loss of periodontal support tissue. Our objective was to investigate the mechanism by which METTL3-mediated N6-methyladenosine modification regulates the osteogenic differentiation through lncRNA in periodontal mesenchymal stem cells in patients with periodontitis (pPDLSCs). Material and Methods. We carried out a series of experiments, including methylated RNA immunoprecipitation-PCR, quantitative real-time polymerase chain reaction, and western blotting. The expressions of alkaline phosphatase (ALP), Runx2, Col1, Runx2 protein level, ALP staining, and Alizarin red staining were used to demonstrate the degree of osteogenic differentiation.

Results

We found that METTL3 was the most significantly differentially expressed methylation-related enzyme in pPDLSCs and promoted osteogenic differentiation of pPDLSCs. METTL3 regulated the stability and expression of lncRNA CUTALP, while lncRNA CUTALP promoted osteogenic differentiation of pPDLSCs by inhibiting miR-30b-3p. At different time points of osteogenic differentiation, lncRNA CUTALP expression was positively correlated with Runx2, while miR-30b-3p showed the opposite pattern. The attenuated osteogenic differentiation induced by METTL3 knockdown was recovered by lncRNA CUTALP overexpression. The attenuated osteogenic differentiation induced by lncRNA CUTALP knockdown could be reversed by the miR-30b-3p inhibitor.

Conclusions

In summary, METTL3/lncRNA CUTALP/miR-30b-3p/Runx2 is a regulatory network in the osteogenic differentiation of pPDLSCs.

An injectable photopolymerizable chitosan hydrogel doped anti-inflammatory peptide for long-lasting periodontal pocket delivery and periodontitis therapy

Periodontitis is a common chronic inflammatory disease caused by plaque that leads to alveolar bone resorption and tooth loss. Inflammation control and achieving better tissue repair are the key to periodontitis treatment. In this study, human β-Defensin 1 short motif Pep-B with inflammation inhibition and differentiation regulation properties, is firstly used in the treatment of periodontitis, and an injectable photopolymerizable Pep-B/chitosan methacryloyl composite hydrogel (CMSA/Pep-B) is constructed. We confirm that Pep-B improves inflammation, and restores osteogenic behavior and function of injured stem cells. CMSA/Pep-B has good injectability, fluidity and photopolymerizability, and can sustainably release Pep-B to maintain drug concentration in periodontal pockets. Furthermore, animal experiments showed that CMSA/Pep-B significantly ameliorated the inflammation of the periodontium and reduced the alveolar bone loss by decreasing inflammatory infiltration, osteoclast formation and collagen destruction. In conclusion, CMSA/Pep-B is envisaged to be a novel bioactive material or therapeutic drug for treating periodontitis.

Roles of human periodontal ligament stem cells in osteogenesis and inflammation in periodontitis models: Effect of 1α,25-dihydroxyvitamin D3

Periodontitis is a chronic inflammatory disease caused by Porphyromonas gingivalis and other bacteria, and human periodontal ligament stem cells (hPDLSCs) are a promising candidate for the treatment of periodontal supporting tissue defects. This study aimed to investigate the effect of 1α,25-dihydroxyvitamin D3 [1,25(OH)2VitD3] on osteogenic differentiation of hPDLSCs in an in vitro periodontitis model and whether it can improve inflammatory status. hPDLSCs were in vitro isolated and identified. After treatment with 1,25(OH)2VitD3 and ultrapure pure Porphyromonas gingivalis lipopolysaccharide (LPS-G), the viability of hPDLSCs was detected using Cell Counting Kit-8, the expressions of osteogenic markers and inflammatory genes using Western blotting and quantitative reverse transcription PCR (qRT-PCR), the levels of inflammatory factors in cells using enzyme linked immunosorbent assay (ELISA), and the fluorescence signal intensity of osteoblastic markers and inflammatory genes in cells using immunofluorescence assay. It was found that 1,25(OH)2VitD3 reversed the inhibition of hPDLSCs proliferation by LPS-G; LPS-G exhibited inhibitory effect on ALP, Runx2, and OPN expressions, and such inhibitory effect was significantly weakened when co-acting with 1,25(OH)2VitD3. Meanwhile, LPS-G upregulated the expressions of inflammatory genes IL-1β and Casp1, whereas 1,25(OH)2VitD3 antagonized such an effect and improved the inflammatory status. In conclusion, 1,25(OH)2VitD3 can reverse the inhibitory effect of LPS-G on hPDLSCs proliferation and osteogenic differentiation and suppress LPS-G-induced upregulation of inflammatory gene expressions.

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

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

Molecular Research on Oral Diseases and Related Biomaterials: A Journey from Oral Cell Models to Advanced Regenerative Perspectives

Oral diseases such as gingivitis, periodontitis, and oral cancer affect millions of people worldwide. Much research has been conducted to understand the pathogenetic mechanisms of these diseases and translate this knowledge into therapeutics. This review aims to take the reader on a journey from the initial molecular discoveries to complex regenerative issues in oral medicine. For this, a semi-systematic literature search was carried out in Medline and Web of Science databases to retrieve the primary literature describing oral cell models and biomaterial applications in oral regenerative medicine. First, an in vitro cell model of gingival keratinocytes is discussed, which illustrates patho- and physiologic principles in the context of oral epithelial homeostasis and carcinogenesis and represents a cellular tool to understand biomaterial-based approaches for periodontal tissue regeneration. Consequently, a layered gradient nonwoven (LGN) is described, which demonstrates that the key features of biomaterials serve as candidates for oral tissue regeneration. LGN supports proper tissue formation and obeys the important principles for molecular mechanotransduction. Furthermore, current biomaterial-based tissue regeneration trends, including polymer modifications, cell-based treatments, antimicrobial peptides and optogenetics, are introduced to represent the full spectrum of current approaches to oral disease mitigation and prevention. Altogether, this review is a foray through established and new concepts in oral regenerative medicine and illustrates the process of knowledge translation from basic molecular and cell biological research to future clinical applications.

Immunomodulatory Activities of Periodontal Ligament Stem Cells in Orthodontic Forces-Induced Inflammatory Processes: Current Views and Future Perspectives

Orthodontic tooth movement (OTM) is induced by applying active mechanical forces, causing a local non-infectious inflammatory response in the periodontal ligament (PDL). As a prerequisite for OTM, the inflammation status is associated with increased levels of various cytokines and involves the interaction between immune cells and periodontal ligament stem cells (hPDLSCs). It is well established that hPDLSCs respond to orthodontic forces in several ways, such as by secreting multiple inflammatory factors. Another essential feature of hPDLSCs is their immunomodulatory activities, which are executed through cytokine (e.g., TNF-α and IL-1β)-induced production of various soluble immunomediators (e.g., indoleamine-2,3-dioxygenase-1, tumor necrosis factor-inducible gene 6 protein, prostaglandin E₂) and direct cell-to-cell contact (e.g., programmed cell death ligand 1, programmed cell death ligand 2). It is well known that these immunomodulatory abilities are essential for local periodontal tissue homeostasis and regeneration. So far, only a handful of studies provides first hints that hPDLSCs change immunological processes during OTM via their immunomodulatory activities. These studies demonstrate the pro-inflammatory aspect of immunomodulation by hPDLSCs. However, no studies exist which investigate cytokine and cell-to-cell contact mediated immunomodulatory activities of hPDLSCs. In this perspective article, we will discuss the potential role of the immunomodulatory potential of hPDLSCs in establishing and resolving the OTM-associated non-infectious inflammation and hence its potential impact on periodontal tissue homeostasis during OTM.

A Review of Antimicrobial Activity of Dental Mesenchymal Stromal Cells: Is There Any Potential?

Antimicrobial defense is an essential component of host-microbial homeostasis and contributes substantially to oral health maintenance. Dental mesenchymal stromal cells (MSCs) possess multilineage differentiation potential, immunomodulatory properties and play an important role in various processes like regeneration and disease progression. Recent studies show that dental MSCs might also be involved in antibacterial defense. This occurs by producing antimicrobial peptides or attracting professional phagocytic immune cells and modulating their activity. The production of antimicrobial peptides and immunomodulatory abilities of dental MSCs are enhanced by an inflammatory environment and influenced by vitamin D3. Antimicrobial peptides also have anti-inflammatory effects in dental MSCs and improve their differentiation potential. Augmentation of antibacterial efficiency of dental MSCs could broaden their clinical application in dentistry.

The Effects of Porphyromonas gingivalis on Inflammatory and Immune Responses and Osteogenesis of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are increasingly used in tissue regeneration, not only because of their multilineage differentiation ability, but also because of their immunomodulatory function, which allows them to play a role in the inflammatory milieu, especially in periodontitis. Porphyromonas gingivalis (P. gingivalis) is an important pathogen associated with the progression of periodontitis. Heterogeneous MSC sources show differences in their inflammatory-immune responsiveness and osteogenesis capabilities when exposed to P. gingivalis and its virulence factors. This article reviews the promoted inflammatory and immune responses of periodontal ligament stem cells, which are potential pitfalls in bone regeneration. MSCs from other sources showed contradictory inflammatory and immune reactions in the few studies on this topic. We also summarize the mechanisms involved in the inflammatory, immune responses and osteogenic potential of MSCs exposed to P. gingivalis and its virulence factors to inform an improved utilization of MSCs in regenerative therapies for periodontitis.

Therapeutic potential of periodontal ligament stem cells

Inflammatory periodontal disease known as periodontitis is one of the most common conditions that affect human teeth and often leads to tooth loss. Due to the complexity of the periodontium, which is composed of several tissues, its regeneration and subsequent return to a homeostatic state is challenging with the therapies currently available. Cellular therapy is increasingly becoming an alternative in regenerative medicine/dentistry, especially therapies using mesenchymal stem cells, as they can be isolated from a myriad of tissues. Periodontal ligament stem cells (PDLSCs) are probably the most adequate to be used as a cell source with the aim of regenerating the periodontium. Biological insights have also highlighted PDLSCs as promising immunomodulator agents. In this review, we explore the state of knowledge regarding the properties of PDLSCs, as well as their therapeutic potential, describing current and future clinical applications based on tissue engineering techniques.

Periodontal ligament stem cells in the periodontitis niche: inseparable interactions and mechanisms

Periodontitis is characterized by the periodontium's pathologic destruction due to the host's overwhelmed inflammation to the dental plaque. The bacterial infections and subsequent host immune responses have shaped a distinct microenvironment, which generally affects resident periodontal ligament stem cells (PDLSCs). Interestingly, recent studies have revealed that impaired PDLSCs may also contribute to the disturbance of periodontal homeostasis. The putative vicious circle underlying the interesting "positive feedback" of PDLSCs in the periodontitis niche remains a hot research topic, whereas the inseparable interactions between resident PDLSCs and the periodontitis niche are still not fully understood. This review provides a microscopic view on the periodontitis progression, especially the quick but delicate immune responses to oral dysbacterial infections. We also summarize the interesting crosstalk of the resident PDLSCs with their surrounding periodontitis niche and potential mechanisms. Particularly, the microenvironment reduces the osteogenic properties of resident PDLSCs, which are closely related to their reparative activity. Reciprocally, these impaired PDLSCs may disrupt the microenvironment by aggravating the host immune responses, promoting aberrant angiogenesis, and facilitating the osteoclastic activity. We further recommend that more in-depth studies are required to elucidate the interactions of PDLSCs with the periodontal microenvironment and provide novel interventions for periodontitis.

Coaxial nanofibrous scaffolds mimicking the extracellular matrix transition in the wound healing process promoting skin regeneration through enhancing immunomodulation

Numerous studies have shown that scaffolds incorporated with extracellular matrix (ECM) proteins could regulate cell behaviors and improve wound healing. However, most ECM-containing scaffolds fail to capture the dynamic features of the native ECM. In this regard, nanofibrous scaffolds which mimic the composition transition of the ECM during wound healing may have great potential in promoting skin regeneration through dynamically modulating the microenvironment. Herein, we report a novel skin ECM-biomimetic coaxial nanofibrous scaffold for the repair of chronic wounds. Two essential ECM proteins, fibrinogen and collagen I, were incorporated into the shell and the core of nanofibers, respectively, to mimic the sequential appearance of fibrinogen and collagen I in the wound healing process. The regulation of the biomimetic coaxial scaffolds on adipose-derived mesenchymal stromal cells (ASCs) was compared with that of the PLGA/fibrinogen, PLGA/collagen I and PLGA uniaxial scaffolds. Our results showed that the biomimetic coaxial scaffolds remarkably promoted the immunomodulatory paracrine secretion of ASCs. By incubating macrophages with ASC conditioned medium, the enhanced immunomodulation of ASCs on the biomimetic coaxial scaffolds was confirmed by the enhanced M1-to-M2 polarization of macrophages. Furthermore, the biomimetic coaxial scaffolds effectively promoted wound repair through resolving inflammation in diabetic rats. These findings helped reveal the role of the dynamic ECM change in regulating wound healing and suggest the potential utility of the biomimetic coaxial scaffolds as a promising alternative to treat chronic wounds.

Effect of TNF-α on the proliferation and osteogenesis of human periodontal mesenchymal stem cells

The aim of the present study was to investigate the effect of tumor necrosis factor-α (TNF-α) on the proliferation and osteogenesis of human periodontal mesenchymal stem cells (hPDLSCs). Antigen expression in hPDLSCs was detected by flow cytometry. hPDLSCs were divided into four groups: A control group with no TNF-α treatment, and three experimental groups treated with 0.1, 1 and 10 ng/ml TNF-α, respectively. The effect of TNF-α on proliferation of hPDLSCs in vitro was detected using a Cell Counting Kit-8 assay. Differentiation into an osteogenic lineage was detected by alkaline phosphatase sand alizarin red staining, and the mRNA and protein expression levels of runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and type I collagen (Col-I) were detected using reverse transcription-quantitative PCR and western blot respectively. Following treatment with 10 ng/ml TNF-α, proliferation was significantly increased compared with an untreated control group (P<0.01). Additionally, there was a significant inhibition of alkaline phosphatase enzyme activity, alizarin red mineralization node size, and in the gene and protein expression levels of osteogenic differentiation markers, including Runx2, OCN and COL-I (all, P<0.05). Taken together, the results indicated that treatment with 10 ng/ml TNF-α promoted the proliferation of hPDLSCs in vitro and inhibited osteogenic differentiation of hPDLSCs, providing an experimental basis for regulation of hPDLSC-mediated periodontal tissue regeneration.

IL-1 Receptor Antagonist Protects the Osteogenesis Capability of Gingival-Derived Stem/Progenitor Cells under Inflammatory Microenvironment Induced by Porphyromonas gingivalis Lipopolysaccharides

Mesenchymal stem cells (MSCs) have been considered to be a future treatment option for periodontitis due to their excellent regenerative capability. However, it is still a challenge to protect MSCs' biological properties from multiple bacterial toxins in local inflammatory environment. The present study is aimed at investigating the treatment effect of interleukin-1 receptor antagonist (IL-1ra) on cell proliferation, migration, and osteogenic differentiation of gingival-derived mesenchymal stem cells (GMSCs) under an inflammatory microenvironment induced by Porphyromonas gingivalis lipopolysaccharides (P. gingivalis-LPS). GMSCs derived from Sprague-Dawley (SD) rats' free gingival tissues were treated with P. gingivalis-LPS (10 μg/mL) to create in vitro inflammatory environment. Different concentrations of IL-1ra (0.01-1 μg/mL) were used to antagonize the negative effect of LPS. Cell behaviors including proliferation, cloning formation unit (CFU), cell migration, osteogenic differentiation, mineral deposition, and cytokine production were assessed to investigate the protection effect of IL-1ra on GMSCs under inflammation. The toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) pathway activated by LPS was evaluated by real-time quantitative polymerase chain reaction (RT-PCR) and western blot. In response to P. gingivalis-LPS treatment, cell numbers, cloning formation rate, cell migration rate, proinflammatory cytokine production, and osteogenic differentiation-associated protein/mRNA expressions as well as mineralized nodules were suppressed in a time-dependent manner. These negative effects were effectively attenuated by IL-1ra administration in a time- and dose-dependent manner. In addition, mRNA expressions of TLR4 and IkBα decreased dramatically when IL-1ra was added into LPS-induced medium. IL-1ra also reversed the LPS-induced TLR4/NF-κB activation as indicated by western blot. The present study revealed that IL-1ra decreased inflammatory cytokine production in a supernatant, so as to protect GMSCs' osteogenesis capacity and other biological properties under P. gingivalis-LPS-induced inflammatory environment. This might be explained by IL-1ra downregulating TLR4-mediated NF-κB signaling pathway activation.

ROS-Scavenging Nanomaterials to Treat Periodontitis

The incidence of periodontitis is very high, and up to 45-50% of people are suffering from periodontitis. Periodontitis is caused by pathogens that invade teeth-supporting tissues such as gingiva, periodontal ligament, and alveolar bone. Pathogens trigger host immune responses characterized by the overproduction of reactive oxygen species (ROS). The development of effective ROS scavengers through nanotechnology has been emerging as a promising strategy for the treatment of periodontitis. Nanomaterial-based antioxidants can effectively scavenge ROS, prevent ROS-mediated tissue damage, and relieve inflammation in periodontitis. This mini-review focuses on the generation of ROS in periodontitis and its molecular mechanism of destroying periodontal tissue. Meanwhile, we summarize the research progress of ROS-scavenging nanomaterials in the treatment of periodontitis and discuss the challenges and prospects of its application.

Mesenchymal Stromal Cells as Potential Antimicrobial for Veterinary Use-A Comprehensive Review

The emergence of “superbugs” resistant to antimicrobial medications threatens populations both veterinary and human. The current crisis has come about from the widespread use of the limited number of antimicrobials available in the treatment of livestock, companion animal, and human patients. A different approach must be sought to find alternatives to or enhancements of present conventional antimicrobials. Mesenchymal stromal cells (MSC) have antimicrobial properties that may help solve this problem. In the first part of the review, we explore the various mechanisms at work across species that help explain how MSCs influence microbial survival. We then discuss the findings of recent equine, canine, and bovine studies examining MSC antimicrobial properties in which MSCs are found to have significant effects on a variety of bacterial species either alone or in combination with antibiotics. Finally, information on the influence that various antimicrobials may have on MSC function is reviewed. MSCs exert their effect directly through the secretion of various bioactive factors or indirectly through the recruitment and activation of host immune cells. MSCs may soon become a valuable tool for veterinarians treating antimicrobial resistant infections. However, a great deal of work remains for the development of optimal MSC production conditions and testing for efficacy on different indications and species.

Medicinal signaling cells: A potential antimicrobial drug store

Medicinal signaling cells (MSCs) are multipotent cells derived from mammalian bone marrow and periosteum that can be extended in culture. They can keep their ability in vitro to form a variety of mesodermal phenotypes and tissues. Over recent years, there has been great attention over MSCs since they can impact the organ transplantation as well as autoimmune and bacterial diseases. MSCs can secrete different bioactive factors such as growth factors, antimicrobial peptides/proteins and cytokines that can suppress the immune system and prevent infection via direct and indirect mechanisms. Moreover, MSCs are able to increase bacterial clearance in sepsis models by producing antimicrobial peptides such as defensins, cathelicidins, lipocalin and hepcidin. It is the aim of the present review to focus on the antibacterial effector functions of MSCs and their mechanisms of action against the pathogenic microbes.

Oral Mesenchymal Stem/Progenitor Cells: The Immunomodulatory Masters

Oral mesenchymal stem/progenitor cells (MSCs) are renowned in the field of tissue engineering/regeneration for their multilineage differentiation potential and easy acquisition. These cells encompass the periodontal ligament stem/progenitor cells (PDLSCs), the dental pulp stem/progenitor cells (DPSCs), the stem/progenitor cells from human exfoliated deciduous teeth (SHED), the gingival mesenchymal stem/progenitor cells (GMSCs), the stem/progenitor cells from the apical papilla (SCAP), the dental follicle stem/progenitor cells (DFSCs), the bone marrow mesenchymal stem/progenitor cells (BM-MSCs) from the alveolar bone proper, and the human periapical cyst-mesenchymal stem cells (hPCy-MSCs). Apart from their remarkable regenerative potential, oral MSCs possess the capacity to interact with an inflammatory microenvironment. Although inflammation might affect the properties of oral MSCs, they could inversely exert a multitude of immunological actions to the local inflammatory microenvironment. The present review discusses the current understanding about the immunomodulatory role of oral MSCs both in periodontitis and systemic diseases, their "double-edged sword" uniqueness in inflammatory regulation, their affection of the immune system, and the underlying mechanisms, involving oral MSC-derived extracellular vesicles.

TLR3 activation modulates immunomodulatory properties of human periodontal ligament cells

BACKGROUND

Toll-like receptors (TLR) are a group of receptors that play roles in the innate immune system. Human periodontal ligament cells (hPDL cells) express several TLRs, including TLR3, a nucleotide sensing receptor that recognizes double-stranded RNA from viral infection. However, its role in hPDL cells is unclear. The aim of this study was to investigate the responses of hPDL cells in terms of immunomodulation after TLR3 engagement.

METHODS

HPDL cells were treated with various doses of poly I:C, a TLR3 activator. The expression of interferon-gamma (IFNγ), indoleamine 2,3 dioxygenase (IDO), and human leukocyte antigen G (HLA-G) was determined. Chemical inhibitors and small interfering RNA (siRNA) were used to confirm the role of TLR3. Coculture with human peripheral blood mononuclear cells (PBMCs) with poly I:C-activated hPDL cells was performed.

RESULTS

Endosomal TLR3 in hPDL cells was observed by immunocytochemistry. Addition of poly I:C significantly enhanced the expression and secretion of IFNγ, IDO, and HLA-G. Knockdown of TLR3 using siRNA decreased the poly I:C-induced expression of these three molecules. Bafilomycin-A, an inhibitor of auto-phagosome and lysosome fusion, inhibited poly I:C-induced IDO and HLA-G expression, whereas cycloheximide and a TLR3-neutralizing antibody had no effect. In co-culture experiments, poly I:C-activated hPDL cells inhibited PBMCs proliferation and increased mRNA expression of forkhead box P3 (FOXP3), a transcription factor which is a marker of regulatory T cells.

CONCLUSION

Our findings indicated that TLR3 engagement of hPDL cells induced immunosuppressive properties of these cells. Because immunosuppressive properties play an important role in tissue healing and regeneration, activation of TLR3 may help to attenuate tissue destruction by limiting the inflammatory process and perhaps initiate the healing and regeneration process of the periodontium.

Inflammasomes and their regulation in periodontal disease: A review

Interleukin-1β (IL-1β), which is secreted by host tissues leading to periodontal tissue inflammation, is a major pro-inflammatory cytokine in the pathogenesis of periodontal disease. The conversion of pro-IL-1β into its biologically active form is controlled by multiprotein complexes named as inflammasomes, which are key regulator of host defense mechanisms and inflammasome involved diseases, including the periodontal diseases. Inflammasomes are regulated by different proteins and processes, including pyrin domain (PYD)-only proteins (POPs), CARD-only proteins (COPs), tripartite motif family proteins (TRIMs), autophagy, and interferons. A review of in vitro, in vivo, and clinical data from these publications revealed that several inflammasomes including (NOD)-like receptor (NLR) pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) have been found to be involved in periodontal disease pathogenesis. To the best of our knowledge, the current article provides the first review of the literature focusing on studies that evaluated both inflammasomes and their regulators in periodontal disease. An upregulation for inflammasomes and a downregulation of inflammasome regulator proteins including POPs, COPs, and TRIMs have been reported in periodontal disease. Although interferons (types I and II) and autophagy have been found to be involved in periodontal disease, their possible role in inflammasome activation has not evaluated yet. Modulating the excessive inflammatory response by the use of inflammasome regulators may have potential in the management of periodontal disease.

A Role for Exosomes in Craniofacial Tissue Engineering and Regeneration

Tissue engineering and regenerative medicine utilize mesenchymal stem cells (MSCs) and their secretome in efforts to create or induce functional tissue replacement. Exosomes are specific extracellular vesicles (EVs) secreted by MSCs and other cells that carry informative cargo from the MSC to targeted cells that influence fundamental cellular processes including apoptosis, proliferation, migration, and lineage-specific differentiation. In this report, we review the current knowledge regarding MSC exosome biogenesis, cargo and function. This review summarizes the use of MSC exosomes to control or induce bone, cartilage, dentin, mucosa, and pulp tissue formation. The next-step engineering of exosomes provides additional avenues to enhance oral and craniofacial tissue engineering and regeneration.

Immunomodulatory properties of dental tissue-derived mesenchymal stem cells: Implication in disease and tissue regeneration

Mesenchymal stem cells (MSCs) are considered as an attractive tool for tissue regeneration and possess a strong immunomodulatory ability. Dental tissue-derived MSCs can be isolated from different sources, such as the dental pulp, periodontal ligament, deciduous teeth, apical papilla, dental follicles and gingiva. According to numerous in vitro studies, the effect of dental MSCs on immune cells might depend on several factors, such as the experimental setting, MSC tissue source and type of immune cell preparation. Most studies have shown that the immunomodulatory activity of dental MSCs is strongly upregulated by activated immune cells. MSCs exert mostly immunosuppressive effects, leading to the dampening of immune cell activation. Thus, the reciprocal interaction between dental MSCs and immune cells represents an elegant mechanism that potentially contributes to tissue homeostasis and inflammatory disease progression. Although the immunomodulatory potential of dental MSCs has been extensively investigated in vitro, its role in vivo remains obscure. A few studies have reported that the MSCs isolated from inflamed dental tissues have a compromised immunomodulatory ability. Moreover, the expression of some immunomodulatory proteins is enhanced in periodontal disease and even shows some correlation with disease severity. MSC-based immunomodulation may play an essential role in the regeneration of different dental tissues. Therefore, immunomodulation-based strategies may be a very promising tool in regenerative dentistry.