High dose of TNF-α suppressed osteogenic differentiation of human dental pulp stem cells by activating the Wnt/β-catenin signaling

Therapeutic trends of priming mesenchymal stem cells: A bibliometric analysis

Mesenchymal stem cells (MSCs) have gained substantial attention in regenerative medicine due to their multilineage differentiation potential and immunomodulatory capabilities. MSCs have demonstrated therapeutic promise in numerous preclinical and clinical studies across a variety of diseases, including neurodegenerative disorders, cardiovascular diseases, and autoimmune conditions. Recently, priming MSCs has emerged as a novel strategy to enhance their therapeutic efficacy by preconditioning them for optimal survival and function in challenging in vivo environments. This study presented a comprehensive bibliometric analysis of research activity in the field of priming mesenchymal stem cells (MSCs) from 2003 to 2023. Utilizing a dataset of 585 documents, we explored research trends, leading authors and countries, productive journals, and frequently used keywords. We also explored priming strategies to augment the therapeutic efficacy of MSCs. Our findings show increasing research productivity with a peak in 2019, identified the United States as the leading contributor, and highlighted WANG JA as the most prolific author. The most published journal was Stem Cell Research & Therapy. Keyword analysis revealed core research areas emerging hotspots, while coword and cited sources visualizations elucidated the conceptual framework and key information sources. Further studies are crucial to advance the translation of primed MSCs from bench to bedside, potentially revolutionizing the landscape of regenerative medicine.

Odontogenic and anti-inflammatory effects of magnesium-doped bioactive glass in vital pulp therapy

This study aimed to investigate the effects of magnesium-doped bioactive glass (Mg-BG) on the mineralization, odontogenesis, and anti-inflammatory abilities of human dental pulp stem cells (hDPSCs). Mg-BG powders with different Mg concentrations were successfully synthesized via the sol-gel method and evaluated using x-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Apatite formation was observed on the surfaces of the materials after soaking in simulated body fluid. hDPSCs were cultured with Mg-BG powder extracts in vitro, and no evident cytotoxicity was observed. Mg-BG induced alkaline phosphatase (ALP) expression and mineralization of hDPSCs and upregulated the expression of odontogenic genes, including those encoding dentin sialophosphoprotein, dentin matrix protein 1, ALP, osteocalcin, and runt-related transcription factor 2. Moreover, Mg-BG substantially suppressed the secretion of inflammatory cytokines (interleukin [IL]-4, IL-6, IL-8, and tumor necrosis factor-alpha). Collectively, the results of this study suggest that Mg-BG has excellent in vitro bioactivity and is a potential material for vital pulp therapy of inflamed pulps.

About a Possible Impact of Endodontic Infections by Fusobacterium nucleatum or Porphyromonas gingivalis on Oral Carcinogenesis: A Literature Overview

Periodontitis is linked to the onset and progression of oral squamous cell carcinoma (OSCC), an epidemiologically frequent and clinically aggressive malignancy. In this context, Fusobacterium (F.) nucleatum and Porphyromonas (P.) gingivalis, two bacteria that cause periodontitis, are found in OSCC tissues as well as in oral premalignant lesions, where they exert pro-tumorigenic activities. Since the two bacteria are present also in endodontic diseases, playing a role in their pathogenesis, here we analyze the literature searching for information on the impact that endodontic infection by P. gingivalis or F. nucleatum could have on cellular and molecular events involved in oral carcinogenesis. Results from the reviewed papers indicate that infection by P. gingivalis and/or F. nucleatum triggers the production of inflammatory cytokines and growth factors in dental pulp cells or periodontal cells, affecting the survival, proliferation, invasion, and differentiation of OSCC cells. In addition, the two bacteria and the cytokines they induce halt the differentiation and stimulate the proliferation and invasion of stem cells populating the dental pulp or the periodontium. Although most of the literature confutes the possibility that bacteria-induced endodontic inflammatory diseases could impact on oral carcinogenesis, the papers we have analyzed and discussed herein recommend further investigations on this topic.

Triptolide mitigates the inhibition of osteogenesis induced by TNF-α in human periodontal ligament stem cells via the p-IκBα/NF-κB signaling pathway: an in-vitro study

BACKGROUND

Triptolide is a widely utilized natural anti-inflammatory drug in clinical practice. Aim of this study was to evaluate effects of triptolide on hPDLSCs osteogenesis in an inflammatory setting and to investigate underlying mechanisms.

METHODS

Using the tissue block method to obtain hPDLSCs from extracted premolar or third molar. Flow cytometry, osteogenic and adipogenic induction were carried out in order to characterise the features of the cells acquired. hPDLSC proliferative activity was assessed by CCK-8 assay to determine the effect of TNF-α and/or triptolide. The impact of triptolide on the osteogenic differentiation of hPDLSCs was investigated by ALP staining and quantification. Osteogenesis-associated genes and proteins expression level were assessed through PCR and Western blotting assay. Finally, BAY-117,082 was used to study the NF-κB pathway.

RESULTS

In the group treated with TNF-α, there was an elevation in inflammation levels while osteogenic ability and the expression of both osteogenesis-associated genes and proteins decreased. In the group co-treated with TNF-α and triptolide, inflammation levels were reduced and osteogenic ability as well as the expression of both osteogenesis-associated genes and proteins were enhanced. At the end of the experiment, both triptolide and BAY-117,082 exerted similar inhibitory effects on the NF-κB pathway.

CONCLUSION

The osteogenic inhibition of hPDLSCs by TNF-α can be alleviated through triptolide, with the involvement of the p-IκBα/NF-κB pathway in this mechanism.

Insight into Steroid-Induced ONFH: The Molecular Mechanism and Function of Epigenetic Modification in Mesenchymal Stem Cells

Osteonecrosis of the femoral head (ONFH) is a common refractory orthopedic disease, which is one of the common causes of hip pain and dysfunction. ONFH has a very high disability rate, which is associated with a heavy burden to patients, families, and society. The pathogenesis of ONFH is not completely clear. At present, it is believed that it mainly includes coagulation dysfunction, abnormal lipid metabolism, an imbalance of osteogenic/adipogenic differentiation, and poor vascularization repair. The prevention and treatment of ONFH has always been a great challenge for clinical orthopedic surgeons. However, recent studies have emphasized that the use of mesenchymal stem cells (MSCs) to treat steroid-induced ONFH (SONFH) is a promising therapy. This review focuses on the role and molecular mechanism of epigenetic regulation in the progress of MSCs in the treatment of SONFH, and discusses the significance of the latest research in the treatment of SONFH from the perspective of epigenetics.

Immunomodulation by mesenchymal stem cells during osteogenic differentiation: Clinical implications during bone regeneration

Critical bone defects resulting in delayed and non-union are a major concern in the field of orthopedics. Over the past decade, mesenchymal stem cells (MSCs) have become a promising frontier for bone repair and regeneration owing to their high expansion rate and osteogenic differentiation potential ex vivo. MSCs have also long been associated with their ability to modulate immune response in the recipients. These can even skew the immune response towards pro-inflammatory or anti-inflammatory type by sensing their local microenvironment. MSCs adopt anti-inflammatory phenotype at bone injury site and secrete various immunomodulatory factors such as IDO, NO, TGFβ1 and PGE-2 which have redundant role in osteoblast differentiation and bone formation. As such, several studies have also sought to decipher the immunomodulatory effects of osteogenically differentiated MSCs. The present review discusses the immunomodulatory status of MSCs during their osteogenic differentiation and summarizes few mechanisms that cause immunosuppression by osteogenically differentiated MSCs and its implication during bone healing.

Reparative Dentin Formation Following Dental Pulp Capping is Mediated by TNFR1 In Vivo

INTRODUCTION

Tumor necrosis factor (TNF)-α is a pro-inflammatory cytokine that promotes biomineralization in vitro in dental pulp cells. However, the role of TNF-α-TNF receptor 1 (TNFR1) signaling in reparative dentin formation and related inflammatory pathways is not known. Therefore, the aim of this study was to evaluate the role of the TNF-α-TNFR1 axis in dental pulp repair following pulp capping in vivo.

METHODS

Dental pulp repair response of genetically deficient TNF-α receptor-1 mice (TNFR1-/-; n = 20) was compared with that of C57Bl6 mice (wild type [WT]; n = 20). Pulp capping was performed with mineral trioxide aggregate on the mandibular first molars of mice. After 7 and 70 days, tissues were collected and stained with hematoxylin and eosin for histopathological and histometric evaluation, and assessed by the Brown and Brenn methods for histomicrobiological analysis and by immunohistochemistry to localize TNF-α, Runt-related transcription factor 2, Dentin Sialoprotein (DSP) and Osteopontin (OPN) expression.

RESULTS

Compared with WT mice, TNFR1-/- mice showed significantly decreased reparative dentin formation with a lower mineralized tissue area (P < .0001). Unlike WT mice, TNFR1-/- mice also exhibited significant dental pulp necrosis, neutrophil recruitment, and apical periodontitis formation (P < .0001) without bacterial tissue invasion. TNFR1-/- animals further exhibited decreased TNF-α, DSP, and OPN expression (P < .0001), whereas Runt-related transcription factor 2 expression was unchanged (P > .05).

CONCLUSION

The TNF-α-TNFR1 axis is involved in reparative dentin formation following dental pulp capping in vivo. Genetic ablation of TNFR1 modified the inflammatory process and inhibited the expression of the DSP and OPN mineralization proteins, which culminated in dental pulp necrosis and development of apical periodontitis.

Low concentrations of tumor necrosis factor-alpha promote human periodontal ligament stem cells osteogenic differentiation by activation of autophagy via inhibition of AKT/mTOR pathway

BACKGROUND

Tumor necrosis factor-alpha (TNF-α) is one of the crucial inflammatory factors in alveolar bone metabolism during the process of periodontitis. Autophagy is indispensable for proper osteoblast function. However, the effects of autophagy on osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) in inflammatory microenvironment and the underlying mechanisms remain to be clarified. The aim of the present study was to investigate whether autophagy participates in hPDLSCs differentiation after treated with TNF-α and explore the underlying mechanisms.

METHODS AND RESULTS

Characterizations of hPDLSCs were evaluated by Alizarin-red S staining, Oil red staining and flow cytometry. hPDLSCs were treated with various concentrations of TNF-α. Rapamycin or 3MA was used to achieve or inhibit autophagy activation. AKT signaling was inhibited using ARQ092. Cell proliferation was evaluated using Cell Counting Kit-8 (CCK8) assay. Real-time reverse transcriptase-polymerase chain reaction assay (RT-PCR), western blot, alkaline phosphatase (ALP) staining and Alizarin Red S staining were applied to evaluate levels of osteogenic differentiation and autophagy. CCK8 showed that low concentrations of TNF-α had no influence on cell proliferation, while high concentrations of TNF-α inhibited proliferation. Low concentrations of TNF-α promoted osteogenic differentiation and autophagy, while high concentrations of TNF-α inhibited osteogenic differentiation and autophagy in hPDLSCs. The levels of osteogenic differentiation in hPDLSCs were partly effected after co-incubation with 0.1 ng/mL TNF-α with 3MA or Rapamycin. ARQ092 enhanced 0.1 ng/mL TNF-α-induced ALP expression and mineral nodule formation.

CONCLUSION

Low concentrations of TNF-α promote hPDLSCs osteogenic differentiation by activation of autophagy via inhibition of AKT/mTOR signaling.

Superior protective effects of PGE2 priming mesenchymal stem cells against LPS-induced acute lung injury (ALI) through macrophage immunomodulation

BACKGROUND

Mesenchymal stem cells (MSCs) have demonstrated remarkable therapeutic promise for acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS). MSC secretomes contain various immunoregulatory mediators that modulate both innate and adaptive immune responses. Priming MSCs has been widely considered to boost their therapeutic efficacy for a variety of diseases. Prostaglandin E2 (PGE2) plays a vital role in physiological processes that mediate the regeneration of injured organs.

METHODS

This work utilized PGE2 to prime MSCs and investigated their therapeutic potential in ALI models. MSCs were obtained from human placental tissue. MSCs were transduced with firefly luciferase (Fluc)/eGFP fusion protein for real-time monitoring of MSC migration. Comprehensive genomic analyses explored the therapeutic effects and molecular mechanisms of PGE2-primed MSCs in LPS-induced ALI models.

RESULTS

Our results demonstrated that PGE2-MSCs effectively ameliorated lung injury and decreased total cell numbers, neutrophils, macrophages, and protein levels in bronchoalveolar lavage fluid (BALF). Meanwhile, treating ALI mice with PGE2-MSCs dramatically reduced histopathological changes and proinflammatory cytokines while increasing anti-inflammatory cytokines. Furthermore, our findings supported that PGE2 priming improved the therapeutic efficacy of MSCs through M2 macrophage polarization.

CONCLUSION

PGE2-MSC therapy significantly reduced the severity of LPS-induced ALI in mice by modulating macrophage polarization and cytokine production. This strategy boosts the therapeutic efficacy of MSCs in cell-based ALI therapy.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: The Novel Therapeutic Option for Regenerative Dentistry

Dental mesenchymal stem cells (MSCs) are characterized by unlimited self-renewal ability and high multidirectional differentiation potential. Since dental MSCs can be easily isolated and exhibit a high capability to differentiate into odontogenic cells, they are considered as attractive therapeutic agents in regenerative dentistry. Recently, MSC-derived extracellular vesicles (MSC-EVs) have attracted widespread attention as carriers for cell-free therapy due to their potential functions. Many studies have shown that MSC-EVs can mediate microenvironment at tissue damage site, and coordinate the regeneration process. Additionally, MSC-EVs can mediate intercellular communication, thus affecting the phenotypes and functions of recipient cells. In this review, we mainly summarized the types of MSCs that could be potentially applied in regenerative dentistry, the possible molecular cargos of MSC-EVs, and the major effects of MSC-EVs on the therapeutic induction of osteogenic differentiation.

Effect of MicroRNA-138 on Tumor Necrosis Factor-Alpha-Induced Suppression of Osteogenic Differentiation of Dental Pulp Stem Cells and Underlying Mechanism

High doses of tumor necrosis factor-α (TNF-α) suppress osteogenic differentiation of human dental pulp stem cells (hDPSCs). In the present study, we aimed to explore the role and potential regulatory mechanism of microRNA-138 (miR-138) in the osteogenic differentiation of hDPSCs after treatment with a high dose of TNF-α. The hDPSCs were cultured in osteogenic medium with or without 50 ng/ml TNF-α. The miR-138 levels were upregulated during osteogenic differentiation of the hDPSCs following TNF-α treatment. The miR-138 overexpression accelerated but miR-138 knockdown alleviated the TNF-α-induced suppression of the alkaline phosphatase activity, calcium deposition, and protein abundance of dentin sialophosphoprotein, dentin matrix protein 1, bone sialoprotein, and osteopontin during osteogenic differentiation induction of hDPSCs. Additionally, miR-138 overexpression accelerated but miR-138 knockdown alleviated the suppression of the focal adhesion kinase- (FAK-) extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway during osteogenic differentiation induction of hDPSCs under TNF-α treatment. In conclusion, miR-138 accelerates TNF-α-induced suppression of osteogenic differentiation of hDPSCs. Inactivation of the FAK-ERK1/2 signaling pathway may be one of the mechanisms underlying the effect of miR-138. Inhibition of miR-138 expression may be a strategy to weaken the inhibitory effect of high-dose TNF-α on the osteogenic differentiation of hDPSCs.

Regulation of osteogenic differentiation by the pro-inflammatory cytokines IL-1β and TNF-α: current conclusions and controversies

Treatment of complex bone fracture diseases is still a complicated problem that is urged to be solved in orthopedics. In bone tissue engineering, the use of mesenchymal stromal/stem cells (MSCs) for tissue repair brings hope to the medical field of bone diseases. MSCs can differentiate into osteoblasts and promote bone regeneration. An increasing number of studies show that the inflammatory microenvironment affects the osteogenic differentiation of MSCs. It is shown that TNF-α and IL-1β play different roles in the osteogenic differentiation of MSCs via different signal pathways. The main factors that affect the role of TNF-α and IL-1β in osteogenic differentiation of MSCs include concentration and the source of stem cells (different species and different tissues). This review in-depth analyzes the roles of pro-inflammatory cytokines in the osteogenic differentiation of MSCs and reveals some current controversies to provide a reference of comprehensively understanding.

Inflammation and Bone Metabolism in Rheumatoid Arthritis: Molecular Mechanisms of Joint Destruction and Pharmacological Treatments

Rheumatoid arthritis (RA) is an inflammatory disease characterized by a variety of symptoms and pathologies often presenting with polyarthritis. The primary symptom in the initial stage is joint swelling due to synovitis. With disease progression, cartilage and bone are affected to cause joint deformities. Advanced osteoarticular destruction and deformation can cause irreversible physical disabilities. Physical disabilities not only deteriorate patients' quality of life but also have substantial medical economic effects on society. Therefore, prevention of the progression of osteoarticular destruction and deformation is an important task. Recent studies have progressively improved our understanding of the molecular mechanism by which synovitis caused by immune disorders results in activation of osteoclasts; activated osteoclasts in turn cause bone destruction and para-articular osteoporosis. In this paper, we review the mechanisms of bone metabolism under physiological and RA conditions, and we describe the effects of therapeutic intervention against RA on bone.

Human dental pulp stem cells and hormesis

This paper represents the first assessment of hormetic dose responses by human dental pulp stem cells (hDPSCs) with particular emphasis on cell renewal (proliferation) and differentiation. Hormetic dose responses were commonly reported in this model, encompassing a broad range of chemicals, including principally pharmaceuticals (e.g., metformin and artemisinin), dietary supplements/extracts from medicinal plants (e.g., berberine, N-acetyl-L-cysteine, and ginsenoside Rg1) and endogenous agents (e.g., ATP, TNF-α). The paper assesses mechanistic foundations of the hDPSCs hormetic dose responses for both cell proliferation and cell differentiation, study design considerations, and therapeutic implications.

SNHG7 promotes the osteo/dentinogenic differentiation ability of human dental pulp stem cells by interacting with hsa-miR-6512-3p in an inflammatory microenvironment

Excessive inflammation leads to periodontitis, which inhibits the osteogenic differentiation of human dental pulp stem cells (hDPSCs), irreversibly injured and difficultly repaired for the important dental pulp. Hence, it is necessary to study the functional gene to enhance the osteogenic differentiation of hDPSCs. Previous found that SNHG7 expression was increased in the osteogenic differentiation of hDPSCs. However, the regulatory functions of SNHG7 on osteogenic differentiation of hDPSCs in the inflammatory microenvironment still remains unknown. In this study, hDPSCs treatment with 50 ng/mL TNF-α to mimic the inflammatory microenvironment, then cultured in osteoblast differentiation medium for 14 days. SNHG7, miR-6512-3p, BSP, DSPP, DMP-1, RUNX2 and OPN in hDPSCs were detect by RT-qPCR. We found that SNHG7 expression was reduced during the osteogenic differentiation of hDPSCs after different concentrations TNF-α treatment. SNHG7 overexpression improved the TNF-α-induced suppression of calcium deposition, ALP activity, and the expression of BSP, DSPP, DMP-1, RUNX2 and OPN. Furthermore, SNHG7 can sponge with miR-6512-3p. miR-6512-3p expression was increased during the osteogenic differentiation of hDPSCs after different concentrations TNF-α treatment while inhibited after SNHG7 overexpression. knockdown of miR-6512-3p improved the TNF-α-induced suppression of calcium deposition, ALP activity, and the expression of BSP, DSPP, DMP-1, RUNX2 and OPN. Finally, miR-6512-3p overexpression reversed the effect of SNHG7 on the osteo/dentinogenic differentiation of TNF-α-treated hDPSCs. In conclusions, SNHG7 improves the osteogenic differentiation of hDPSCs by inhibiting miR-6512-3p expression under 50 ng/mL TNF-α-induced inflammatory environment, which provided potential targets for the treatment of periodontitis.

Priming strategies for controlling stem cell fate: Applications and challenges in dental tissue regeneration

Mesenchymal stromal cells (MSCs) have attracted intense interest in the field of dental tissue regeneration. Dental tissue is a popular source of MSCs because MSCs can be obtained with minimally invasive procedures. MSCs possess distinct inherent properties of self-renewal, immunomodulation, proangiogenic potential, and multilineage potency, as well as being readily available and easy to culture. However, major issues, including poor engraftment and low survival rates in vivo, remain to be resolved before large-scale application is feasible in clinical treatments. Thus, some recent investigations have sought ways to optimize MSC functions in vitro and in vivo. Currently, priming culture conditions, pretreatment with mechanical and physical stimuli, preconditioning with cytokines and growth factors, and genetic modification of MSCs are considered to be the main strategies; all of which could contribute to improving MSC efficacy in dental regenerative medicine. Research in this field has made tremendous progress and continues to gather interest and stimulate innovation. In this review, we summarize the priming approaches for enhancing the intrinsic biological properties of MSCs such as migration, antiapoptotic effect, proangiogenic potential, and regenerative properties. Challenges in current approaches associated with MSC modification and possible future solutions are also indicated. We aim to outline the present understanding of priming approaches to improve the therapeutic effects of MSCs on dental tissue regeneration.

Progranulin promotes osteogenic differentiation of periodontal membrane stem cells in both inflammatory and non-inflammatory conditions

Objective

The growth factor progranulin (PGRN) is widely expressed and plays important roles in anti-inflammatory signaling and bone regeneration. However, the anti-inflammatory and pro-osteogenic roles of PGRN in periodontitis are seldom studied. We used an in vitro model to investigate whether PGRN can promote osteogenic differentiation of periodontal ligament stem cells (PDLSCs).

Methods

PDLSCs were treated with PGRN (0 to 100 ng/mL) and the optimal concentrations required to induce proliferation and osteogenesis were identified. PDLSCs were cultured with 10 ng/mL tumor necrosis factor (TNF)-α, 25 ng/mL PGRN, or 10 ng/mL TNF-α + 25 ng/ml PGRN; untreated PDLSCs were used as controls. The effects of PGRN on PDLSC proliferation and osteogenic differentiation were assessed.

Results

PGRN (5, 25, and 50 ng/mL) promoted PDLSC proliferation and osteogenic differentiation, with the 25-ng/mL dose showing the largest effect. Furthermore, 25 ng/mL PGRN reversed inhibition of osteogenic differentiation by TNF-α.

Conclusion

PGRN promotes PDLSC proliferation, osteogenic differentiation, and mineralization in both inflammatory and non-inflammatory conditions. The 25-ng/mL PRGN dose was the most suitable for inducing proliferation and osteogenesis. Further studies using animal models will be required to obtain pre-clinical evidence to support using PGRN as a treatment for periodontitis.

Tumor Necrosis Factor Alpha Signaling and Organogenesis

Tumor necrosis factor alpha (TNF-α) plays important roles in processes such as immunomodulation, fever, inflammatory response, inhibition of tumor formation, and inhibition of viral replication. TNF-α and its receptors are ubiquitously expressed in developing organs and they regulate the survival, proliferation, and apoptosis of embryonic stem cells (ESCs) and progenitor cells. TNF-α is an important inflammatory factor that also regulates the inflammatory response during organogenesis, and its cytotoxic effects can interfere with normal developmental processes, even leading to the onset of diseases. This review summarizes the various roles of TNF-α in organogenesis in terms of its secreting pattern, concentration-dependent activities, and interactions with other signaling pathways. We also explored new potential functions of TNF-α.

Human gingiva-derived mesenchymal stem cells promote osteogenic differentiation through their immunosuppressive function

OBJECTIVES

Human gingiva-derived mesenchymal stem cells (GMSCs) have emerged as a new MSC population exhibiting robust immune regulatory functions, multipotent differentiation potential, and regenerative ability. However, the effects of GMSCs on T cells remain unexplored. Herein, we aimed to evaluate whether GMSCs promote osteogenic differentiation by regulating immune cells.

METHODS

The GMSC phenotype was confirmed using the colony-forming assay, immunophenotyping, Oil red O staining, and Alizarin red staining. mRNA expression levels of proinflammatory molecules (interleukin-1β [IL-1β] and tumor necrosis factor-α [TNF-α]) and anti-inflammatory factors (IL-10) were measured by quantitative reverse-transcription PCR (qRT-PCR). Then, MC3T3-E1 cells were treated with the collected co-culture supernatant, followed by alkaline phosphatase (ALP) and immunofluorescence staining to evaluate osteogenic differentiation of MC3T3-E1 cells. qRT-PCR and western blotting were employed to analyze the expression levels of osteogenic differentiation proteins, including collagen type I (COL-1), ALP, osteopontin (OPN), and runt-related transcription factor 2 (RUNX2).

RESULTS

GMSCs were successfully isolated and identified. We observed that GMSCs suppressed the activated T-cell function by downregulating IL-1β and TNF-α and upregulating IL-10. Simultaneously, the expression levels of osteogenesis-related genes (COL-1, ALP, OPN, and RUNX2) were markedly lower in the co-culture supernatant and Jurkat T cell supernatant groups than those in the normal culture medium group; however, expression levels were significantly increased in the co-culture supernatant group when compared with the Jurkat T cell supernatant group.

CONCLUSION

Our findings indicate that GMSCs could promote the osteogenic differentiation of MC3T3-E1 cells by inhibiting the biological activity of activated T cells.

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.

Deciphering Reparative Processes in the Inflamed Dental Pulp

Research over several decades has increased our understanding of the nature of reparative and regenerative processes in the dental pulp, at both the cellular and molecular level. However, advances in scientific knowledge have not translated into novel clinical treatment strategies for caries-induced pulpitis. This narrative review explores the evidence regarding the ability of inflamed pulp tissue to heal and how this knowledge may be used therapeutically. A literature search and evidence analysis covering basic, translational and clinical pulp biology research was performed. The review focuses on (1) the regenerative and defense capabilities of the pulp during caries-induced inflammation; (2) the potential of novel biomaterials to harness the reparative and regenerative functions of the inflamed pulp; and (3) future perspectives and opportunities for conservative management of the inflamed pulp. Current conservative management strategies for pulpitis are limited by a combination of unreliable diagnostic tools and an outdated understanding of pulpal pathophysiological responses. This approach leads to the often unnecessary removal of the entire pulp. Consequently, there is a need for better diagnostic approaches and a focus on minimally-invasive treatments utilizing biologically-based regenerative materials and technologies.

Shared Genetic and Epigenetic Mechanisms between the Osteogenic Differentiation of Dental Pulp Stem Cells and Bone Marrow Stem Cells

OBJECTIVE

To identify the shared genetic and epigenetic mechanisms between the osteogenic differentiation of dental pulp stem cells (DPSC) and bone marrow stem cells (BMSC).

MATERIALS AND METHODS

The profiling datasets of miRNA expression in the osteogenic differentiation of mesenchymal stem cells from the dental pulp (DPSC) and bone marrow (BMSC) were searched in the Gene Expression Omnibus (GEO) database. The differential expression analysis was performed to identify differentially expressed miRNAs (DEmiRNAs) dysregulated in DPSC and BMSC osteodifferentiation. The target genes of the DEmiRNAs that were dysregulated in DPSC and BMSC osteodifferentiation were identified, followed by the identification of the signaling pathways and biological processes (BPs) of these target genes. Accordingly, the DEmiRNA-transcription factor (TFs) network and the DEmiRNAs-small molecular drug network involved in the DPSC and BMSC osteodifferentiation were constructed.

RESULTS

16 dysregulated DEmiRNAs were found to be overlapped in the DPSC and BMSC osteodifferentiation, including 8 DEmiRNAs with a common expression pattern (8 upregulated DEmiRNAs (miR-101-3p, miR-143-3p, miR-145-3p/5p, miR-19a-3p, miR-34c-5p, miR-3607-3p, miR-378e, miR-671-3p, and miR-671-5p) and 1 downregulated DEmiRNA (miR-671-3p/5p)), as well as 8 DEmiRNAs with a different expression pattern (i.e., miR-1273g-3p, miR-146a-5p, miR-146b-5p, miR-337-3p, miR-382-3p, miR-4508, miR-4516, and miR-6087). Several signaling pathways (TNF, mTOR, Hippo, neutrophin, and pathways regulating pluripotency of stem cells), transcription factors (RUNX1, FOXA1, HIF1A, and MYC), and small molecule drugs (curcumin, docosahexaenoic acid (DHA), vitamin D3, arsenic trioxide, 5-fluorouracil (5-FU), and naringin) were identified as common regulators of both the DPSC and BMSC osteodifferentiation.

CONCLUSION

Common genetic and epigenetic mechanisms are involved in the osteodifferentiation of DPSCs and BMSCs.

Quercetin reverses TNF‑α induced osteogenic damage to human periodontal ligament stem cells by suppressing the NF‑κB/NLRP3 inflammasome pathway

Quercetin (Quer) is a typical antioxidant flavonoid from plants that is involved in bone metabolism, as well as in the progression of inflammatory diseases. Elevated levels of tumor necrosis factor-α (TNF-α), a typical pro-inflammatory cytokine, can affect osteogenesis. In the present study, TNF-α was used to establish an in vitro model of periodontitis. The effects of Quer on, as well as its potential role in the osteogenic response of human periodontal ligament stem cells (hPDLSCs) under TNF-α-induced inflammatory conditions and the underlying mechanisms were then investigated. Within the appropriate concentration range, Quer did not exhibit any cytotoxicity. More importantly, Quer significantly attenuated the TNF-α induced the suppression of osteogenesis-related genes and proteins, alkaline phosphatase (ALP) activity and mineralized matrix in the hPDLSCs. These findings were associated with the fact that Quer inhibited the activation of the NF-κB signaling pathway, as well as the expression of NLRP3 inflammation-associated proteins in the inflammatory microenvironment. Moreover, the silencing of NLRP3 by small interfering RNA (siRNA) was found to protect the hPDLSCs against TNF-α-induced osteogenic damage, which was in accordance with the effects of Quer. On the whole, the present study demonstrates that Quer reduces the impaired osteogenesis of hPDLSCs under TNF-α-induced inflammatory conditions by inhibiting the NF-κB/NLRP3 inflammasome pathway. Thus, Quer may prove to be a potential remedy against periodontal bone defects.

miR-23b mediates TNF-α-Inhibited Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Targeting Runx2

Periodontitis is the most prevalent oral infection disease, which causes the destruction of periodontal supporting tissues and eventual tooth loss. This study aimed to investigate the molecular mechanism of miRNA-23b (miR-23b) in regulating the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) in an inflammatory environment. Results revealed that tumor necrosis factor-α (TNF-α), a notoriously inflammatory cytokine, remarkably attenuated the osteogenic differentiation of hPDLSCs, which were partially rescued by SKL2001 (Wnt/β-catenin agonist). We further explored the underlying roles of miRNAs involved in TNF-α-inhibited osteogenesis of hPDLSCs. The miR-23b significantly increased with TNF-α stimulation, which was abolished by SKL2001. Similar to the effect of TNF-α, miR-23b agonist (agomir-23b) dramatically reduced the expression of runt-related transcription factor 2 (Runx2) and suppressed the osteogenic differentiation of hPDLSCs. The inhibition of miR-23b significantly increased Runx2, which is the major transcription factor during osteogenesis, thereby indicating that miR-23b was an endogenous regulator of Runx2 in hPDLSCs. Bioinformatic analysis and dual luciferase reporter assays confirmed that Runx2 was a target gene of miR-23b. Furthermore, the gain function assay of Runx2 revealed that the Runx2 overexpression efficiently reversed the suppression of the osteogenic differentiation of hPDLSCs with miR-23b agonist, suggesting that the suppressing effect of miR-23b on osteogenesis was mediated by Runx2 inhibition. Our study clarified that miR-23b mediated the TNF-α-inhibited osteogenic differentiation of hPDLSCs by targeting Runx2. Therefore, the expanded function of miR-23b in the osteogenesis of hPDLSCs under inflammatory conditions. This study might provide new insights and a novel therapeutic target for periodontitis.

TNF‑α regulates the osteogenic differentiation of bone morphogenetic factor 9 adenovirus‑transduced rat follicle stem cells via Wnt signaling

Periodontitis is a chronic infectious disease that alters the cellular microenvironment and promotes bone absorption. Bone morphogenetic protein 9 (BMP9) serves an important role in proliferation and differentiation, and tumor necrosis factor‑alpha (TNF‑α) is an important contributor to bone resorption. The present study aimed to investigate the effect of osteogenic differentiation in the presence of BMP9 and TNF‑α in rat follicle stem cells (rDFCs). rDFCs were transfected with adenoviruses expressing BMP9 (AdBMP9) and the expression levels of important proteins [BMP9, β‑catenin, glycogen synthase kinase 3β (GSK3β), phosphorylated‑GSK3β, calcium/calmodulin dependent protein kinase II and nemo like kinase] were determined using western blotting. The effect of osteogenesis was analyzed using reverse transcription‑quantitative PCR, in addition to alkaline phosphatase, Alizarin Red S, and hematoxylin and eosin staining methods. The results of the present study revealed that TNF‑α activated the canonical Wnt signaling pathway and suppressed osteogenesis. High concentrations of Dickkopf 1 (DKK1) reduced the osteogenic differentiation of AdBMP9‑transduced rDFCs, whereas low concentrations of DKK1 promoted BMP9‑induced bone formation, which was discovered to partially act via the canonical and non‑canonical Wnt signaling pathways. In conclusion, the findings of the present study suggested that the enhanced promoting effect of BMP9 alongside the treatment with low concentrations of DKK1 may be useful for treating periodontitis bone absorption.

Inflammatory niche: Mesenchymal stromal cell priming by soluble mediators

Mesenchymal stromal/stem cells (MSCs) are adult stem cells of stromal origin that possess self-renewal capacity and the ability to differentiate into multiple mesodermal cell lineages. They play a critical role in tissue homeostasis and wound healing, as well as in regulating the inflammatory microenvironment through interactions with immune cells. Hence, MSCs have garnered great attention as promising candidates for tissue regeneration and cell therapy. Because the inflammatory niche plays a key role in triggering the reparative and immunomodulatory functions of MSCs, priming of MSCs with bioactive molecules has been proposed as a way to foster the therapeutic potential of these cells. In this paper, we review how soluble mediators of the inflammatory niche (cytokines and alarmins) influence the regenerative and immunomodulatory capacity of MSCs, highlighting the major advantages and concerns regarding the therapeutic potential of these inflammatory primed MSCs. The data summarized in this review may provide a significant starting point for future research on priming MSCs and establishing standardized methods for the application of preconditioned MSCs in cell therapy.

Short- and long-term treatment with TNF-α inhibits the induction of osteoblastic differentiation in cyclic tensile-stretched periodontal ligament fibroblasts

Background

Cyclic tensile stretching (CTS) induces osteoblastic differentiation of periodontal ligament fibroblasts (PDLF). On the other hand, increased concentrations of tumour necrosis factor-α (TNF-α) are found in inflammatory conditions, leading to periodontal disease and tooth loss. Accordingly, our aim was to investigate the short- and long-term effect of TNF-α on the response of human PDLF to CTS and its implication on osteoblastic differentiation.

Methods

PDLF were either pre-incubated for 4 hours or were repeatedly exposed to TNF-α for up to 50 days and then subjected to CTS. Gene expression was determined by quantitative real-time polymerase chain reaction. Activation of mitogen-activated protein kinase (MAPK) was monitored by western analysis and cell proliferation by bromodeoxyuridine incorporation. Intracellular reactive oxygen species were determined by the 2´, 7´-dichlorofluorescein-diacetate assay and osteoblastic differentiation by Alizarin Red-S staining after an osteo-inductive period of 21 days.

Results

CTS of PDLF induced an immediate upregulation of the c-fos transcription factor and, further downstream the overexpression of alkaline phosphatase and osteopontin, two major osteoblast marker genes. A 4-hour pre-incubation with TNF-α repressed these effects. Similarly, long-term propagation of PDLF along with TNF-α diminished their osteoblastic differentiation capacity and suppressed cells’ CTS-elicited responses. The observed phenomena were not linked with TNF-α-induced premature senescence or oxidative stress. While CTS induced the activation of MAPKs, involved in mechanotransduction, TNF-α treatment provoked a small delay in the phosphorylation of extracellular signal-regulated kinase and c-Jun N-terminal kinase.

Conclusion

Increased concentrations of TNF-α, such as those recorded in many inflammatory diseases, suppress PDLF’s immediate responses to mechanical forces compromising their osteoblastic differentiation potential, possibly leading to tissue’s impaired homeostasis.

Mesenchymal Stem Cells from Human Exfoliated Deciduous Teeth and the Orbicularis Oris Muscle: How Do They Behave When Exposed to a Proinflammatory Stimulus?

Mesenchymal stem cells (MSCs) have been studied as a promising type of stem cell for use in cell therapies because of their ability to regulate the immune response. Although they are classically isolated from the bone marrow, many studies have sought to isolate MSCs from noninvasive sources. The objective of this study was to evaluate how MSCs isolated from the dental pulp of human exfoliated deciduous teeth (SHED) and fragments of the orbicularis oris muscle (OOMDSCs) behave when treated with an inflammatory IFN-γ stimulus, specifically regarding their proliferative, osteogenic, and immunomodulatory potentials. The results demonstrated that the proliferation of SHED and OOMDSCs was inhibited by the addition of IFN-γ to their culture medium and that treatment with IFN-γ at higher concentrations resulted in a greater inhibition of the proliferation of these cells than treatment with IFN-γ at lower concentrations. SHED and OOMDSCs maintained their osteogenic differentiation potential after stimulation with IFN-γ. Additionally, SHED and OOMDSCs have been shown to have low immunogenicity because they lack expression of HLA-DR and costimulatory molecules such as CD40, CD80, and CD86 before and after IFN-γ treatment. Last, SHED and OOMDSCs expressed the immunoregulatory molecule HLA-G, and the expression of this antigen increased after IFN-γ treatment. In particular, an increase in intracellular HLA-G expression was observed. The results obtained suggest that SHED and OOMDSCs lack immunogenicity and have immunomodulatory properties that are enhanced when they undergo inflammatory stimulation with IFN-γ, which opens new perspectives for the therapeutic use of these cells.

Hyperbaric Oxygen Therapy Improves the Osteogenic and Vasculogenic Properties of Mesenchymal Stem Cells in the Presence of Inflammation In Vitro

Hyperbaric oxygen (HBO) therapy has been reported to be beneficial for treating many conditions of inflammation-associated bone loss. The aim of this work was to in vitro investigate the effect of HBO in the course of osteogenesis of human Mesenchymal Stem Cells (MSCs) grown in a simulated pro-inflammatory environment. Cells were cultured with osteogenic differentiation factors in the presence or not of the pro-inflammatory cytokine Tumor Necrosis Factor-α (TNF-α), and simultaneously exposed daily for 60 min, and up to 21 days, at 2,4 atmosphere absolute (ATA) and 100% O₂. To elucidate osteogenic differentiation-dependent effects, cells were additionally pre-committed prior to treatments. Cell metabolic activity was evaluated by means of the MTT assay and DNA content quantification, whereas osteogenic and vasculogenic differentiation was assessed by quantification of extracellular calcium deposition and gene expression analysis. Metabolic activity and osteogenic properties of cells did not differ between HBO, high pressure (HB) alone, or high oxygen (HO) alone and control if cells were pre-differentiated to the osteogenic lineage. In contrast, when treatments started contextually to the osteogenic differentiation of the cells, a significant reduction in cell metabolic activity first, and in mineral deposition at later time points, were observed in the HBO-treated group. Interestingly, TNF-α supplementation determined a significant improvement in the osteogenic capacity of cells subjected to HBO, which was not observed in TNF-α-treated cells exposed to HB or HO alone. This study suggests that exposure of osteogenic-differentiating MSCs to HBO under in vitro simulated inflammatory conditions enhances differentiation towards the osteogenic phenotype, providing evidence of the potential application of HBO in all those processes requiring bone regeneration.

DKK1 and TNF-alpha influence osteogenic differentiation of adBMP9-infected-rDFCs

OBJECTIVES

Rat dental follicle cells (rDFCs) function as precursor cells of periodontal tissues. Bone morphogenetic protein (BMP9) plays an important role in proliferation and differentiation. Tumour necrosis factor-alpha (TNF-alpha) is an important contributor to bone resorption. Wnt canonical pathway can be inhibited by Dickkopf 1 (DKK1). The aim of the study was to enhance the osteogenesis of BMP9 treated rDFCs in an inflammatory environment and elucidate the mechanism.

MATERIALS AND METHODS

rDFCs were infected by adenoviruses expressing BMP9 (adBMP9). Expression levels of proteins and genes were measured by Western blotting and qPCR. The effect on osteogenesis was evaluated by measuring the activity of alkaline phosphatase (ALP), observation of Alizarin Red S and haematoxylin and eosin staining.

RESULTS

TNF-alpha activated the canonical Wnt pathway and inhibited the non-canonical pathway. DKK1 suppressed the canonical pathway and promoted the non-canonical pathway. Addition of TNF-alpha or DKK1 inhibited BMP9/Smad pathway. However, this inhibition was reduced by the addition of DKK1 with TNF-alpha.

CONCLUSIONS

DKK1 reduces the inhibitory effects of TNF-alpha in adBMP9-infected-rDFCs, possibly through interaction with the Smad signalling pathway and Wnt pathways. These findings may lead to a novel approach for the treatment of periodontitis-related alveolar bone defects.

Progranulin Promotes Regeneration of Inflammatory Periodontal Bone Defect in Rats via Anti-inflammation, Osteoclastogenic Inhibition, and Osteogenic Promotion

Progranulin (PGRN) has been proved to play a crucial role in anti-inflammation and osteogenesis promotion; thus, it was hypothesized that PGRN could promote bone regeneration in periodontal disease. In this experiment, the periodontal bone defects were established in periodontitis rats; recombinant human progranulin (rhPGRN), tumor necrosis factor alpha inhibitor (anti-TNF-α), or phosphate buffer saline (PBS)-loaded collagen membrane scaffolds were implanted within defects and the rats were sacrificed at scheduled time points. Volume of new bone was assessed by radiological and histomorphometric analyses. Expression of osteogenesis-related markers and tumor necrosis factor-α (TNF-α) was evaluated using immunohistochemistry. Tartrate-resistant acid phosphatase (TRAP) staining was also performed to determine the number of osteoclasts. Immunofluorescence (IF) staining was performed to explore the interaction between rhPGRN and tumor necrosis factor receptors (TNFRs). The results showed that the rhPGRN group had significantly superior quantity and quality of newly formed bone, higher expression of alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and TNFR2 compared with the PBS group and the anti-TNF-α group. Similarly to the anti-TNF-α group, the rhPGRN group also exhibited the significant inhibitory effect on the expression of TNF-α and the number of TRAP-positive cells compared with the PBS group. Hence, our experiment suggests that PGRN promotes regeneration of inflammatory periodontal bone defect in rats via anti-inflammation, osteoclastogenic inhibition, and osteogenic promotion. Local administration of PGRN may provide a new therapeutic strategy for periodontal bone regeneration.

Mechanical Stress Modulates the RANKL/OPG System of Periodontal Ligament Stem Cells via α7 nAChR in Human Deciduous Teeth: An In Vitro Study

The aim of this study was to investigate the mechanism by which periodontal ligament stem cells (PDLSCs) modulate root resorption of human deciduous teeth under mechanical stress. In this investigation, the PDLSCs were derived from deciduous and permanent teeth at different stages of root resorption. A cyclic hydraulic pressure was applied on the PDLSCs to mimic chewing forces in the oral environment. The cultured cells were characterized using osteogenic and adipogenic differentiation assays, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting analysis. The PDLSCs exhibited the ability to induce osteoclast differentiation under certain mechanical stresses. As the expressions of RUNX2, alkaline phosphatase (ALP), and osteoprotegerin (OPG) were significantly reduced, the receptor activator of the nuclear factor kappa-B ligand (RANKL) was upregulated increasing the RANKL/OPG ratio. Under hydrodynamic pressure at 0-135 kPa, the expressions of alpha 7 nicotinic acetylcholine receptors (α7 nAChR), p-GSK-3β, and active-β-catenin were markedly upregulated in PDLSCs from unresorbed deciduous teeth. Treatment with the α7 nAChR inhibitor alpha-bungarotoxin (α-BTX) and the Wnt pathway inhibitor DKK1 may reverse the mechanical stress inducing upregulation of RANKL and reduction of RUNX2, ALP, and OPG. Alizarin red staining confirmed these results. The mechanical stress applied on the deciduous tooth PDLSCs can induce osteoclastic effects through upregulation of α7 nAChR and activation of the canonical Wnt pathway. It can be suggested that chewing forces may play a major role at the beginning of the physiological root resorption of deciduous teeth.

The periodontal stem/progenitor cell inflammatory-regenerative cross talk: A new perspective

Adult multipotent stem/progenitor cells, with remarkable regenerative potential, have been isolated from various components of the human periodontium. These multipotent stem/progenitor cells include the periodontal ligament stem/progenitor cells (PDLSCs), stem cells from the apical papilla (SCAP), the gingival mesenchymal stem/progenitor cells (G-MSCs), and the alveolar bone proper stem/progenitor cells (AB-MSCs). Whereas inflammation is regarded as the reason for tissue damage, it also remains a fundamental step of any early healing process. In performing their periodontal tissue regenerative/reparative activity, periodontal stem/progenitor cells interact with their surrounding inflammatory micro-environmental, through their expressed receptors, which could influence their fate and the outcome of any periodontal stem/progenitor cell-mediated reparative/regenerative activity. The present review discusses the current understanding about the interaction of periodontal stem/progenitor cells with their surrounding inflammatory micro-environment, elaborates on the inflammatory factors influencing their stemness, proliferation, migration/homing, differentiation, and immunomodulatory attributes, the possible underlying intracellular mechanisms, as well as their proposed relationship to the canonical and noncanonical Wnt pathways.

ELP2 negatively regulates osteoblastic differentiation impaired by tumor necrosis factor α in MC3T3-E1 cells through STAT3 activation

Tumor necrosis factor‐α (TNF‐α) is a pluripotent signaling molecule. The biological effect of TNF‐α includes slowing down osteogenic differentiation, which can lead to bone dysplasia in long‐term inflammatory microenvironments. Signal transducer and activator of transcription 3 (STAT3)‐interacting protein 1 (StIP1, also known as elongator complex protein 2, ELP2) play a role in inhibiting TNF‐α‐induced osteoblast differentiation. In the present study, we investigated whether and how ELP2 activation mediates the effects of TNF‐α on osteoblastic differentiation. Using in vitro cell cultures of preosteoblastic MC3T3‐E1 cells, we found that TNF‐α inhibited osteoblastic differentiation accompanied by an increase in ELP2 expression and STAT3 activation. Forced ELP2 expression inhibited osteogenic differentiation of MC3T3‐E1 cells, with a decrease in the expression of osteoblast marker genes, alkaline phosphatase activity, and matrix mineralization capacity. In contrast, ELP2 silencing ameliorated osteogenic differentiation in MC3T3‐E1 cells, even after TNF‐α stimulation. The TNF‐α‐induced inhibitory effect on osteoblastic differentiation was therefore mediated by ELP2, which was associated with Janus kinase 2 (JAK2)/STAT3 activation. These results suggest that ELP2 is upregulated at the differentiation of MC3T3‐E1 cells into osteoblasts and inhibits osteogenic differentiation in response to TNF‐α through STAT3 activation.

Involvement of tumor necrosis factor alpha in steroid-associated osteonecrosis of the femoral head: friend or foe?

Background

The etiology and pathology osteonecrosis of the femoral head (ONFH) are not completely clarified. As a cytokine participating in systemic inflammation, tumor necrosis factor alpha (TNFα) has been shown to be involved in the pathogenesis of ONFH. However, the role of TNFα in ONFH is not clearly clarified. In the present study, we investigated the effects of TNFα on proliferation, angiogenesis, and osteogenic differentiation of rat bone mesenchymal stem cells (rMSCs) and the underlying mechanisms.

Methods

All femoral bone tissues were separated in surgeries. After extracting total RNA and protein, we evaluated TNFα content by ELISA and the relative expression levels of genes by quantitative real-time PCR and western blot. Also, immunohistochemistry staining was performed to observe the expression of Runx2 in the bone samples. Chick embryo chorioallantoic membrane (CAM) assay was performed to observe the effect of TNFα on angiogenesis. The genomic DNAs were treated by bisulfite modification, and methylation status of CpG sites in the CpG islands of human and rat Runx2 gene promoter was determined by DNA sequencing. The binding of H3K4me3 and H3K27me3 in Runx2 promoter was checked by ChIP assay. RNA-seq analysis was used to find out the genes and pathways changed by TNFα in rMSCs.

Results

The results demonstrate TNFα promotes cell proliferation and angiogenesis whereas inhibits osteogenesis. Epigenetic regulations including DNA methylation and histone modifications play important roles in mediating the effect of TNFα on osteogenic differentiation. We find an increased rate of CpG methylation in rat Runx2 promoter in TNFα-treated rMSCs, as well as significantly increased occupancy of H3K27me3 in Runx2 gene promoter. The content of TNFα in necrotic tissue is much lower than that of normal tissue. And relevantly, human Runx2 promoter is demethylated in necrotic tissue using bone samples from patient with ONFH. In addition, we have observed that Wnt signaling pathway is inhibited by TNFα as multiple Wnts are markedly decreased in TNFα-treated rMSCs by RNA-seq analysis.

Conclusion

Taken together, our study shows that TNFα plays complicated roles in the pathogenesis of ONFH, including proliferation, angiogenesis, and osteogenesis. Targeting TNFα should not be considered as an applicable strategy to inhibit the progression of ONFH.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1112-x) contains supplementary material, which is available to authorized users.

TNF-α suppresses osteogenic differentiation of MSCs by accelerating P2Y2 receptor in estrogen-deficiency induced osteoporosis

Tumor Necrosis Factor-α (TNF-α)-inhibited osteogenic differentiation of mesenchymal stem cells (MSCs) contributes to impaired bone formation, which plays a central role in the pathogenesis of postmenopausal osteoporosis. However, the exact mechanisms of TNF-α-inhibited osteoblast differentiation have not been fully elucidated. Multiple P2 purinoceptor subtypes are expressed in several species of osteoblasts and are confirmed to regulate bone metabolism. The purpose of this study is to investigate whether P2 purinoceptors are involved in TNF-α-inhibited osteoblast differentiation. This study shows TNF-α increased P2Y₂ receptor expression in the differentiation of MSCs into osteoblasts in a noticeable manner. Overexpressing or silencing of the P2Y₂ receptor either impaired or promoted osteogenic differentiation of MSCs significantly. Silencing of the P2Y₂ receptor attenuated the inhibitory effects of TNF-α on osteoblastic differentiation of MSCs. In addition, silencing of the P2Y₂ receptor evidently alleviated TNF-α-inhibited MSC proliferation. P2Y₂ receptor expression was mechanistically upregulated by TNF-α mainly through extracellular regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways. Overall, our results revealed a novel function of the P2Y₂ receptor and suggested suppressing the P2Y₂ receptor may be an effective strategy to promote bone formation in estrogen deficiency-induced osteoporosis.

IL-33 guides osteogenesis and increases proliferation and pluripotency marker expression in dental stem cells

Objectives

Soluble IL‐33 (interleukin (IL)‐1‐like cytokine) acts as endogenous alarm signal (alarmin). Since alarmins, besides activating immune system, act to restore tissue homeostasis, we investigated whether IL‐33 exerts beneficial effects on oral stem cell pull.

Materials and Methods

Clonogenicity, proliferation, differentiation and senescence of stem cells derived from human periodontal ligament (PDLSCs) and dental pulp (DPSCs) were determined after in vitro exposure to IL‐33. Cellular changes were detected by flow cytometry, Western blot, immunocytochemistry and semiquantitative RT‐PCR.

Results

IL‐33 stimulated proliferation, clonogenicity and expression of pluripotency markers, OCT‐4, SOX‐2 and NANOG, but it inhibited ALP activity and mineralization in both PDLSCs and DPSCs. Higher Ki67 expression and reduced β‐galactosidase activity in IL‐33‐treated cells were demonstrated, whereas these trends were more conspicuous in osteogenic medium. However, after 7‐day IL‐33 pretreatment, differentiation capacity of IL‐33‐pretreated cells was retained, and increased ALP activity was observed in both cell types. Results showed that IL‐33 regulates NF‐κB and β‐catenin signalling, indicating the association of these molecules with changes observed in IL‐33‐treated PDLSCs and DPSCs, particularly their proliferation, pluripotency‐associated marker expression and osteogenesis.

Conclusions

IL‐33 treatment impairs osteogenesis of PDLSCs and DPSCs, while increases their clonogenicity, proliferation and pluripotency marker expression. After exposure to IL‐33, osteogenic capacity of cells stayed intact. NF‐κB and β‐catenin are implicated in the effects achieved by IL‐33 in PDLSCs and DPSCs.

The Host Response in Tissue Engineering: Crosstalk Between Immune cells and Cell-laden Scaffolds

Implantation of cell-laden scaffolds is a promising strategy for regenerating tissue that has been damaged due to injury or disease. However, the act of implantation initiates an acute inflammatory response. If the scaffold is non-biologic (i.e., a modified biologic scaffold or synthetic-based scaffold), inflammation will be prolonged through the foreign body response (FBR), which eventually forms a fibrous capsule and walls off the implant from the surrounding host tissue. This host response, from a cellular perspective, can create a harsh environment leading to long-lasting effects on the tissue engineering outcome. At the same time, cells embedded within the scaffold can respond to this environment and influence the interrogating immune cells (e.g., macrophages). This crosstalk, depending on the type of cell, can dramatically influence the host response. This review provides an overview of the FBR and highlights important and recent advancements in the host response to cell-laden scaffolds with a focus on the impact of the communication between immune cells and cells embedded within a scaffold. Understanding this complex interplay between the immune cells, notably macrophages, and the tissue engineering cells is a critically important component to a successful in vivo tissue engineering therapy.

Mesenchymal Stem Cells of Dental Origin for Inducing Tissue Regeneration in Periodontitis: A Mini-Review

Periodontitis is a chronic disease that begins with a period of inflammation of the supporting tissues of the teeth table and then progresses, destroying the tissues until loss of the teeth occurs. The restoration of the damaged dental support apparatus is an extremely complex process due to the regeneration of the cementum, the periodontal ligament, and the alveolar bone. Conventional treatment relies on synthetic materials that fill defects and replace lost dental tissue, but these approaches are not substitutes for a real regeneration of tissue. To address this, there are several approaches to tissue engineering for regenerative dentistry, among them, the use of stem cells. Mesenchymal stem cells (MSC) can be obtained from various sources of adult tissues, such as bone marrow, adipose tissue, skin, and tissues of the orofacial area. MSC of dental origin, such as those found in the bone marrow, have immunosuppressive and immunotolerant properties, multipotency, high proliferation rates, and the capacity for tissue repair. However, they are poorly used as sources of tissue for therapeutic purposes. Their accessibility makes them an attractive source of mesenchymal stem cells, so this review describes the field of dental stem cell research and proposes a potential mechanism involved in periodontal tissue regeneration induced by dental MSC.

Dental Stem Cells in Bone Tissue Engineering: Current Overview and Challenges

The treatment of bone that is impaired due to disease, trauma or tumor resection creates a challenge for both clinicians and researchers. Critical size bone defects are conventionally treated with autografts which are associated with risks such as donor site morbidity and limitations like donor shortage. Bone tissue engineering has become a promising area for the management of critical size bone defects by the employment of biocompatible materials and the discovery of novel stem cell sources. Mesenchymal stem cells (MSCs) can be isolated with ease from various dental tissues including dental pulp stem cells, stem cells from apical papilla, dental follicle stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, gingival stem cells and tooth germ derived stem cells. Outcomes of dental MSC mediated bone tissue engineering is explored in various in vivo and in vitro preclinical studies. However, there are still obscurities regarding the mechanisms underlying in MSC mediated bone regeneration and challenges in applications of dental stem cells. In this review, we summarized dental stem cell sources and their characterizations, along with currently used biomaterials for cell delivery and future perspectives for dental MSCs in the field of bone tissue engineering. Further efforts are necessary before moving to clinical trials for future applications.

Relationship of Cx43 regulation of vascular permeability to osteopontin-tight junction protein pathway after sepsis in rats

Our previous study demonstrated that connexin (Cx)43 participated in the regulation of vascular permeability in severe sepsis. Osteopontin (OPN) has been demonstrated to participate in the occurrence of atherosclerosis, inflammation, as well as the adhesion and migration of cells. It is not clear whether OPN is involved in Cx43 regulating vascular permeability after sepsis and if it is related to tight-junction proteins. with the use of cecal ligation and puncture (CLP)-induced septic rats and lipopolysaccharide (LPS)-treated pulmonary vein vascular endothelial cells (VECs), the role of zona occuldens 1 (ZO-1) and claudin-5 in Cx43 regulation of vascular permeability and its relationship to OPN were investigated in the present study. The results showed that the expression of ZO-1 and claudin-5 in pulmonary vein were decreased in CLP rats and LPS-treated pulmonary vein VECs. Cx43-overexpressed lentivirus induced the degradation of ZO-1 and claudin-5, while Cx43 RNAi lentivirus abrogated the degradation of ZO-1 and claudin-5 induced by LPS. The vascular permeability and expression of OPN in pulmonary veins were significantly increased in CLP rats and LPS-treated pulmonary vein VECs. Silencing OPN by OPN RNAi lentivirus inhibited the vascular hyperpermeability induced by LPS. Overexpressed Cx43 lentivirus increased the expression of OPN and vascular permeability and downregulated the expression of ZO-1 and claudin-5 in pulmonary vein VECs. Silencing OPN by OPN RNAi lentivirus inhibited the effects of Cx43-overexpressed lentivirus on downregulation of ZO-1 and claudin-5 and vascular hyperpermeability in pulmonary vein VECs. Transfection of specific double-stranded RNA targeting to β-catenin and T-cell factor-4 (Tcf-4) abolished the upregulation of OPN induced by Cx43 overexpression. These results suggest that OPN participates in the regulation of vascular permeability by Cx43 after sepsis. Cx43 upregulation of OPN is via the Tcf-4/β-catenin transcription pathway; OPN increases vascular permeability by downregulating the expression of the tight junction proteins ZO-1 and claudin-5.

Bone regeneration is associated with the concentration of tumour necrosis factor-α induced by sericin released from a silk mat

To understand the osteogenic effect of the middle layer of the silk cocoon, sericin was examined for its cellular effects associated with tumor necrosis factor-α (TNF-α) signaling in this study. The fragmented sericin proteins in the silk mat were evaluated for the TNF-α expression level in murine macrophages. The concentration of protein released from silk mats was higher in the outermost and the innermost layers than in the middle layers, and the protein released from the silk mat was identified as sericin. The level of TNF-α in murine macrophages was dependent on the applied concentration of sericin, and the expression of genes associated with osteogenesis in osteoblast-like cells was dependent on the applied concentration of TNF-α. In animal experiments, silk mats from the middle layers led to a higher regenerated bone volume than silk mats from the innermost layer or the outermost layer. If TNF-α protein was incorporated into the silk mats from the middle layers, bone regeneration was suppressed compared with unloaded silk mats from the middle layers. Accordingly, silk mats from the silk cocoon can be considered to be a fragmented sericin-secreting carrier, and the level of sericin secretion is associated with TNF-α induction and bone regeneration.

Blockade of LGR4 inhibits proliferation and odonto/osteogenic differentiation of stem cells from apical papillae

During tooth root development, stem cells from apical papillae (SCAPs) are indispensable, and their abilities of proliferation, migration and odontoblast differentiation are linked to root formation. Leucine-rich repeat-containing GPCR 4 (LGR4) modulates the biological processes of proliferation and differentiation in multiple stem cells. In this study, we showed that LGR4 is expressed in all odontoblast cell lineage cells and Hertwig's epithelial root sheath (HERS) during the mouse root formation in vivo. In vitro we determined that LGR4 is involved in the Wnt/β-catenin signaling pathway regulating proliferation and odonto/osteogenic differentiation of SCAPs. Quantitative reverse-transcription PCR (qRT-PCR) confirmed that LGR4 is expressed during odontogenic differentiation of SCAPs. CCK8 assays and in vitro scratch tests, together with cell cycle flow cytometric analysis, demonstrated that downregulation of LGR4 inhibited SCAPs proliferation, delayed migration and arrested cell cycle progression at the S and G2/M phases. ALP staining revealed that blockade of LGR4 decreased ALP activity. QRT-PCR and Western blot analysis demonstrated that LGR4 silencing reduced the expression of odonto/osteogenic markers (RUNX2, OSX, OPN, OCN and DSPP). Further Western blot and immunofluorescence studies clarified that inhibition of LGR4 disrupted β-catenin stabilization. Taken together, downregulation of LGR4 gene expression inhibited SCAPs proliferation, migration and odonto/osteogenic differentiation by blocking the Wnt/β-catenin signaling pathway. These results indicate that LGR4 might play a vital role in SCAPs proliferation and odontoblastic differentiation.

Multiplex analysis of serum hormone and cytokine in patients with cervical cOPLL: towards understanding the potential pathogenic mechanisms

Cervical ossification of the posterior longitudinal ligament (cOPLL) is one of the major causes of myelopathy. However, the mechanism underlying remains elusive. In the present study, using MILLIPLEX magnetic bead panel, we investigated four serum hormones and six serum cytokines in cOPLL patients and healthy subjects. The results showed that tumor necrosis factore-α (TNF-α) were significantly increased, and DDK-1 was significantly decreased in the serum from male and female cOPLL patients compared with those from healthy controls, respectively. Osteopontin (OPN) and fibroblast growth factor-23 (FGF-23) were significantly increased in male cOPLL patients compared with that in healthy male controls. Further analysis showed that FGF-23 and OPN significantly increased, dickkopf-1 (DKK-1) decreased in the extensive cOPLL group. In addition, a significant positive correlation between the OPN and FGF-23 was observed in male cOPLL patients. The results are useful for understanding the mechanism underlying cOPLL.

Tumor necrosis factor-alpha inhibits osteogenic differentiation of pre-osteoblasts by downregulation of EphB4 signaling via activated nuclear factor-kappaB signaling pathway

BACKGROUND AND OBJECTIVE

The majority of experiments show that tumor necrosis factor-alpha (TNF-α) inhibits osteogenic differentiation of mesenchymal stem cells and pre-osteoblasts by activated nuclear factor-kappaB (NF-κB) signaling. However, the underlying mechanisms by which NF-κB signaling inhibits osteogenic differentiation are not fully understood. The aim of the present study was to investigate whether EphB4 signaling inhibition mediates the effects of TNF-α-activated NF-κB signaling on osteogenic differentiation of pre-osteoblasts.

MATERIAL AND METHODS

Murine MC3T3-E1 pre-osteoblasts were treated with 10 ng/mL of TNF-α. NF-κB inhibitor, pyrrolidine dithiocarbamate, was used to achieve NF-κB signaling inhibition. EphB4 signaling was activated using ephrinB2-fc. The mRNA expressions of runt related transcription factor 2 (Runx2), bone sialoprotein (BSP) and EphB4 were determined using reverse transcription-polymerase chain reaction. The protein levels of Runx2, BSP, Col Ia1, osteopontin, EphB4, p-NF-κB p65 and NF-κB p65 were evaluated using western blot assays. Alkaline phosphatase (ALP) activity in MC3T3-E1 cells was evaluated by ALP activity kit, and mineral nodule formation was evaluated by Alizarin Red S staining.

RESULTS

TNF-α inhibited EphB4 expression, while it suppressed Runx2, BSP expression from gene and protein levels as well as ALP activity and mineral nodule formation in MC3T3-E1 cells. Activation of EphB4 signaling by ephrinB2-fc promoted osteogenic differentiation of MC3T3-E1 cells, whereas TNF-α impaired the osteogenic differentiation enhanced by ephrinB2-fc. Pyrrolidine dithiocarbamate blocked the activation of NF-κB signaling induced by TNF-α, while it prevented the downregulation of Runx2, BSP and EphB4, induced by TNF-α.

CONCLUSION

TNF-α inhibits osteogenic differentiation of pre-osteoblasts by downregulation of EphB4 signaling via activated NF-κB signaling pathway.

Pulp Inflammation Diagnosis from Clinical to Inflammatory Mediators: A Systematic Review

INTRODUCTION

Similar to other tissues, the dental pulp mounts an inflammatory reaction as a way to eliminate pathogens and stimulate repair. Pulp inflammation is prerequisite for dentin pulp complex repair and regeneration; otherwise, chronic disease or pulp necrosis occurs. Evaluation of pulp inflammation severity is necessary to predict the clinical success of maintaining pulp vitality. Clinical limitations to evaluating in situ inflammatory status are well-described. A molecular approach that aids clinical distinction between reversible and irreversible pulpitis could improve the success rate of vital pulp therapy. The aim of this article is to review inflammatory mediator expression in the context of clinical diagnosis.

METHODS

We searched PubMed and Cochrane databases for articles published between 1970 and December 2016. Only published studies of inflammatory mediator expression related to clinical diagnosis were eligible for inclusion and analysis.

RESULTS

Thirty-two articles were analyzed. Two molecular approaches were described by study methods, protein expression analysis and gene expression analysis. Our review indicates that interleukin-8, matrix metalloproteinase 9, tumor necrosis factor-α, and receptor for advanced glycation end products expression increase at both the gene and protein levels during inflammation.

CONCLUSIONS

Clinical irreversible pulpitis is related to specific levels of inflammatory mediator expression. The difference in expression between reversible and irreversible disease is both quantitative and qualitative. On the basis of our analysis, in situ quantification of inflammatory mediators may aid in the clinical distinction between reversible and irreversible pulpitis.

Odontoblastic inductive potential of epithelial cells derived from human deciduous dental pulp

For the dentin regeneration, dental epithelial cells are indispensible and must possess odontoblastic induction capability. Epithelial cell-like stem cells were recently identified in human deciduous dental pulp (DPESCs). However, their cellular characteristics remain poorly defined. The purpose of this study was to characterize DPESCs compared to HAT-7 ameloblastic cells. Expression levels of ameloblast-specific markers [odontogenic ameloblast-associated protein (Odam), matrix metalloproteinase (Mmp)-20, amelogenin, and ameloblastin] were detected in DPESCs. Co-culturing odontoblastic MDPC-23 cells with DPESCs increased expression of odontoblast differentiation markers (Dmp1 and Dspp) from days 4 to 10, while the expression of bone sialoprotein rapidly decreased. MDPC-23 cells cultured in DPESC-conditioned medium (CM) showed increased Dspp promoter activity compared with control MDPC-23 cultures. Mineralization was first observed in the CM groups from day 4 and proceeded rapidly until day 14, whereas mineralized nodules were found from day 7 in control media-cultured cells. In conclusion, DPESCs in human deciduous pulp possess ameloblast-like characteristics and differentiation properties, and substances derived from DPESCs promote odontoblastic differentiation. Thus, our results indicate that DPESCs can be a realistic epithelial source for use in odontoblastic induction and dentin formation of dental mesenchymal cells.

Interferon-gamma improves impaired dentinogenic and immunosuppressive functions of irreversible pulpitis-derived human dental pulp stem cells

Clinically, irreversible pulpitis is treated by the complete removal of pulp tissue followed by replacement with artificial materials. There is considered to be a high potential for autologous transplantation of human dental pulp stem cells (DPSCs) in endodontic treatment. The usefulness of DPSCs isolated from healthy teeth is limited. However, DPSCs isolated from diseased teeth with irreversible pulpitis (IP-DPSCs) are considered to be suitable for dentin/pulp regeneration. In this study, we examined the stem cell potency of IP-DPSCs. In comparison with healthy DPSCs, IP-DPSCs expressed lower colony-forming capacity, population-doubling rate, cell proliferation, multipotency, in vivo dentin regeneration, and immunosuppressive activity, suggesting that intact IP-DPSCs may be inadequate for dentin/pulp regeneration. Therefore, we attempted to improve the impaired in vivo dentin regeneration and in vitro immunosuppressive functions of IP-DPSCs to enable dentin/pulp regeneration. Interferon gamma (IFN-γ) treatment enhanced in vivo dentin regeneration and in vitro T cell suppression of IP-DPSCs, whereas treatment with tumor necrosis factor alpha did not. Therefore, these findings suggest that IFN-γ may be a feasible modulator to improve the functions of impaired IP-DPSCs, suggesting that autologous transplantation of IFN-γ-accelerated IP-DPSCs might be a promising new therapeutic strategy for dentin/pulp tissue engineering in future endodontic treatment.