Pro-inflammatory cytokines induce odontogenic differentiation of dental pulp-derived stem cells

Retracted articles in endodontic-related literature: an analysis of 60 cases

INTRODUCTION

The number of retracted articles in the bio-medical field, including dentistry, is increasing. The objective of this study was to identify retracted articles in endodontic-related literature and outline their main characteristics.

EVIDENCE ACQUISITION

The Medline and Scopus databases were searched in January 2024. Additional records were identified by consulting the online database www.retractiondatabase.org. Retracted articles concerning endodontic topics and the relative retraction notes were retrieved and relevant data extracted.

EVIDENCE SYNTHESIS

Sixty articles were identified, published between 2004 and 2022, with a mean of 3.0±2.3 retracted articles per year. The number of retracted articles per year did not significantly grow over time. The average time between the article and retraction note publication was 36.1±22.3 months. The majority of articles originated from Asia and were in-vitro studies. Only 6.7% of the articles were retracted due to honest errors. The main reasons of retraction were image/data manipulation (20%), plagiarism (18%), unavailability of raw data (10%), authorship issues (10%) and publication process issues (10%). A single research group accounted for 17 retractions.

CONCLUSIONS

Unlike the dental field, the number of retracted articles in endodontics has not increased significantly over the time period considered. Despite this, controls against research misconduct must be increased to preserve the credibility of scientific research.

Neu5Ac Induces Human Dental Pulp Stem Cell Osteo-/Odontoblastic Differentiation by Enhancing MAPK/ERK Pathway Activation

Dental pulp stem cells (DPSCs) must undergo odontoblastic differentiation in order to facilitate the process of dentin-pulp complex repair. Herein, we sought to explore the ability of Neu5Ac (one form of sialic acid) to influence DPSC osteo-/odontoblastic differentiation via modulating mitogen-activated protein kinase (MAPK) signaling. Methodology. DPSCs were isolated from human third permanent teeth and were grown in vitro. Fluorescent microscopy was used to detect the existence of sialic acid on the DPSC membrane. Following the treatment of different concentrations of Neu5Ac and removing sialic acid from the cell surface by neuraminidase, the osteo-/odontoblastic differentiation of these cells was evaluated via mineralization, alkaline phosphatase, and in vivo assays. In addition, the expression of genes related to osteo-/odontoblastic differentiation and MAPK signaling at different stages of this differentiation process was analyzed in the presence or absence of Neu5Ac. Results. The existence of sialic acid on the DPSC membrane was confirmed by fluorescent microscopy, and the ability of osteo-/odontoblastic differentiation was decreased after removing sialic acid by neuraminidase. Treatment of DPSCs with Neu5Ac (0.1 mM or 1 mM) significantly enhanced their mineralization ability and alkaline phosphatase activity. The expression levels of DMP1, DSPP, BSP, and RUNX2 were also increased. Treatment of nude mice with ManNAc (the prerequisite form of Neu5Ac) also enhanced DPSC mineralization activity in vivo. Furthermore, Neu5Ac treatment enhanced p-ERK expression in DPSCs, while ERK pathway inhibition disrupted the ability of Neu5Ac to enhance the osteo-/odontoblastic differentiation of these cells. Conclusions. Neu5Ac can promote DPSC osteo-/odontoblastic differentiation through a process associated with the modulation of the ERK signaling pathway activity.

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.

The proangiogenic effects of extracellular vesicles secreted by dental pulp stem cells derived from periodontally compromised teeth

Background

Although dental pulp stem cells (DPSCs) isolated from periodontally compromised teeth (P-DPSCs) have been demonstrated to retain pluripotency and regenerative potential, their use as therapeutics remains largely unexplored. In this study, we investigated the proangiogenic effects of extracellular vesicles (EVs) secreted by P-DPSCs using in vitro and in vivo testing models.

Methods

Patient-matched DPSCs derived from periodontally healthy teeth (H-DPSCs) were used as the control for P-DPSCs. Conditioned media (CMs) derived from H-DPSCs and P-DPSCs (H-CM and P-CM), CMs derived from both cell types pretreated with the EV secretion blocker GW4869 (H-GW and P-GW), and EVs secreted by H-DPSCs and P-DPSCs (H-EVs and P-EVs) were prepared to test their proangiogenic effects on endothelial cells (ECs). Cell proliferation, migration, and tube formation were assessed using the Cell Counting Kit-8 (CCK-8), transwell/scratch wound healing, and Matrigel assays, respectively. Specifically, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and western blot analysis were used to examine the expression levels of angiogenesis-related genes/proteins in ECs in response to EV-based incubation. Finally, a full-thickness skin defect model was applied to test the effects of EVs on wound healing and new vessel formation.

Results

Both H-CM and P-CM promoted EC angiogenesis, but the proangiogenic effects were compromised when ECs were incubated in H-GW and P-GW, wherein the EV secretion was blocked by pretreatment with GW4869. In EV-based incubations, although both H-EVs and P-EVs were found to enhance the angiogenesis-related activities of ECs, P-EVs exerted a more robust potential to stimulate EC proliferation, migration, and tube formation. In addition, P-EVs led to higher expression levels of angiogenesis-related genes/proteins in ECs than H-EVs. Similarly, both P-EVs and H-EVs were found to accelerate wound healing and promote vascularization across skin defects in mice, but wounds treated with P-EVs resulted in a quicker healing outcome and enhanced new vessel formation.

Conclusions

The findings of the present study provide additional evidence that P-DPSCs derived from periodontally diseased teeth represent a potential source of cells for research and therapeutic use. Particularly, the proangiogenic effects of P-EVs suggest that P-DPSCs may be used to promote new vessel formation in cellular therapy and regenerative medicine.

The potential application of concentrated growth factor in pulp regeneration: an in vitro and in vivo study

Background

Concentrated growth factor (CGF), as a natural biomaterial, is known to contain platelets, cytokines, and growth factors to facilitate the healing process, but there has been little information acquired in regenerative endodontics. The purpose of this study was to investigate the effects of CGF on proliferation, migration, and differentiation in human dental stem pulp cells (hDPSCs) exposed to lipopolysaccharide (LPS) in vitro and its potential role in pulp regeneration of the immature teeth in vivo.

Methods

In vitro experiments: CGF-conditioned medium were extracted by freeze-dried method. hDPSCs were isolated and identified. The proliferative potential of hDPSCs with different concentration of CGF and LPS was evaluated by Cell Counting Kit-8. Migration capacity was analyzed by Transwell assays, odonto/osteoblastic differentiation was determined by measuring alkaline phosphatase (ALP) activity using ALP staining, and the extent of mineralization was evaluated by using Alizarin red S staining. The mRNA expression level of DMP-1, DSPP, OPN, Runx2, and OCN were determined by quantitative polymerase chain reaction (qPCR).

In vivo experiments: CGF were used as root canal filling agent of the immature single-rooted teeth in the beagle dogs. The teeth were then radiographed, extracted, fixed, demineralized, and subjected to histologic analyses at 8 weeks. The newly formed dentine-pulp complex and the development of apical foramen were evaluated by the hematoxylin-eosin (HE) and Masson trichrome technique. Soft tissues were analyzed by immunohistochemical staining of vascular endothelial growth factor (VEGF) and Nestin.

Results

In vitro experiments: The cultured cells exhibited the characteristics of mesenchymal stem cell. The treatment of LPS significantly increased the expression of TNF-α, IL-1β, IL-6, and IL-8 in hDPSCs, and CGF inhibited the mRNA expression of IL-8 in LPS-stimulated hDPSCs. The proliferation values of the CGF group in LPS-stimulated hDPSCs were significantly higher than that of the control group from day 3 to day 7 (P < 0.05). In addition, the number of migratory cells of the CGF group was greater than that of the control group at 24 h with or without LPS treatment. ALP activities increased gradually in both groups from day 4 to day 7. The mineralized nodules and the expression of odontogenesis-related genes DMP-1 and DSPP, osteogenesis-related genes OPN, Runx2, and OCN were dramatically enhanced by CGF in LPS-stimulated hDPSCs at days 21 and 28.

In vivo experiments: In CGF treated group, the results of radiograph, HE, and Masson trichrome staining showed a continuing developed tooth of the immature teeth in the beagle dogs (i.e., the ingrowth of soft tissues into the root canal, the thickened internal root dentin walls, and the closed apex), which resembled the normal tooth development in the positive control group. The immunohistochemical staining showed that VEGF and Nestin were both moderately expressed in the regenerated pulp-like tissues which indicating the vascularization and innervation.

Conclusions

CGF has a positive effect on the proliferation, migration, and differentiation of hDPSCs exposed to LPS in vitro, and it can also promote the regeneration of dentine-pulp complex of the immature teeth in the beagle dogs in vivo. Therefore, CGF could be a promising alternative biomaterial in regenerative endodontics.

MiR-21/STAT3 Signal Is Involved in Odontoblast Differentiation of Human Dental Pulp Stem Cells Mediated by TNF-α

Dental pulp stem cells (DPSCs), as one type of mesenchymal stem cells (MSCs), have the capability of self-renewal and multipotency to differentiate into several cell lineages, including osteogenesis, odontoblasts, chondrogenesis, neurogenesis, and adipogenesis. It has found that tumor necrosis factor-α (TNF-α) can promote osteogenic differentiation of human DPSCs in our previous studies. Other experimentation revealed that signal transducer and activator of transcription 3 (STAT3) underwent a rapid activation both in osteogenesis and inflammation microenvironment of MSCs in vitro. MicroRNAs (miRNAs or miRs) have been proved in previous studies to regulate MSCs differentiation in vitro. In this study, we identified miR-21 as a key miRNA contributed the functional axis of odontoblast differentiation induced by STAT3. It is observed that the expression of miR-21 and STAT3 increased gradually in low concentration (1-10 ng/mL) of TNF-α, while they were suppressed in high concentration (50-100 ng/mL). The upregulation of miR-21 may facilitate the odontoblast differentiation of DPSCs coordinating with STAT3. SiSTAT3 or treated by the inhibitor of STAT3, cucurbitacin I (Cuc I), significantly increased primary miR-21 expression along with decreased mature miR-21 expression. Meanwhile, the inhibition of miR-21 (anti-miR-21) decreased the activation of STAT3 as well as suppressed the marker proteins of odontoblast differentiation. The results revealed a new function of miR-21, suggesting that miR-21/STAT3 signal may act as a modulator within a complex network of factors to regulate odontoblast differentiation of human DPSCs. It may provide a novel therapeutic strategy to regulate the odontoblast differentiation of DPSCs.

Repeated stimulation by LPS promotes the senescence of DPSCs via TLR4/MyD88-NF-κB-p53/p21 signaling

Dental pulp stem cells (DPSCs), one type of mesenchymal stem cells, are considered to be a type of tool cells for regenerative medicine and tissue engineering. Our previous studies found that the stimulation with lipopolysaccharide (LPS) might introduce senescence of DPSCs, and this senescence would have a positive correlation with the concentration of LPS. The β-galactosidase (SA-β-gal) staining was used to evaluate the senescence of DPSCs and immunofluorescence to show the morphology of DPSCs. Our findings suggested that the activity of SA-β-gal has increased after repeated stimulation with LPS and the morphology of DPSCs has changed with the stimulation with LPS. We also found that LPS bound to the Toll-like receptor 4 (TLR4)/myeloid differentiation factor (MyD) 88 signaling pathway. Protein and mRNA expression of TLR4, MyD88 were enhanced in DPSCs with LPS stimulation, resulting in the activation of nuclear factor-κB (NF-κB) signaling, which exhibited the expression of p65 improved in the nucleus while the decreasing of IκB-α. Simultaneously, the expression of p53 and p21, the downstream proteins of the NF-κB signaling, has increased. In summary, DPSCs tend to undergo senescence after repeated stimulation in an inflammatory microenvironment. Ultimately, these findings may lead to a new direction for cell-based therapy in oral diseases and other regenerative medicines.

Cytokine Expression of Stem Cells Originating from the Apical Complex and Coronal Pulp of Immature Teeth

INTRODUCTION

The aim of this study was to measure and compare the expression levels of cytokines from developing apical complex cells (DACCs) and dental pulp stem cells (DPSCs) of the immature tooth.

METHODS

DPSC-conditioned medium (CM) and DACCs-CM were obtained from human young teeth, and 174 cytokines secreted from each CM were identified and compared. A cytokine membrane array and enzyme-linked immunosorbent assay were used to measure and compare the expression levels of the cytokines. Immunocytochemistry targeting insulin-like growth factor-1 and neurotrophin-3 was additionally performed.

RESULTS

There were statistically significant differences in the expression levels of 25 cytokines: 22 and 3 were expressed more strongly in DPSCs-CM and DACCs-CM, respectively. Odontoblast differentiation-related cytokines were more strongly expressed in DPSCs-CM, while cell-proliferation-related cytokines were more strongly expressed in DACCs-CM. Proinflammatory and anti-inflammatory cytokines were predominantly expressed in DPSCs-CM and DACCs-CM, respectively.

CONCLUSIONS

DPSCs may exert a stronger paracrine effect than DACCs on regeneration of the dentin-pulp complex, in terms of odontoblast differentiation.

Mesenchymal stem cells derived from inflamed dental pulpal and gingival tissue: a potential application for bone formation

BACKGROUND

Chronic periodontal disease is an infectious disease consisting of prolonged inflammation of the supporting tooth tissue and resulting in bone loss. Guided bone regeneration procedures have become common and safe treatments in dentistry, and in this context dental stem cells would represent the ideal solution as autologous cells. In this study, we verified the ability of dental pulp mesenchymal stem cells (DPSCs) and gingival mesenchymal stem cells (GMSCs) harvested from periodontally affected teeth to produce new mineralized bone tissue in vitro, and compared this to cells from healthy teeth.

METHODS

To characterize DPSCs and GMSCs, we assessed colony-forming assay, immunophenotyping, mesenchymal/stem cell phenotyping, stem gene profiling by means of flow cytometry, and quantitative polymerase chain reaction (qPCR). The effects of proinflammatory cytokines on mesenchymal stem cell (MSC) proliferation and differentiation potential were investigated. We also observed participation of several heat shock proteins (HSPs) and actin-depolymerizing factors (ADFs) during osteogenic differentiation.

RESULTS

DPSCs and GMSCs were successfully isolated both from periodontally affected dental tissue and controls. Periodontally affected dental MSCs proliferated faster, and the inflamed environment did not affect MSC marker expressions. The calcium deposition was higher in periodontally affected MSCs than in the control group. Proinflammatory cytokines activate a cytoskeleton remodeling, interacting with HSPs including HSP90 and HSPA9, thioredoxin-1, and ADFs such as as profilin-1, cofilin-1, and vinculin that probably mediate the increased acquisition in the inflamed environment.

CONCLUSIONS

Our findings provide evidence that periodontally affected dental tissue (both pulp and gingiva) can be used as a source of MSCs with intact stem cell properties. Moreover, we demonstrated that the osteogenic capability of DPSCs and GMSCs in the test group was not only preserved but increased by the overexpression of several proinflammatory cytokine-dependent chaperones and stress response proteins.

Dental Pulp Cells Isolated from Teeth with Superficial Caries Retain an Inflammatory Phenotype and Display an Enhanced Matrix Mineralization Potential

We have isolated dental pulp cells (DPCs) from three healthy (hDPCs) and three carious (cDPCs) donors and shown that compared to hDPCs cells isolated from superficial carious lesions show higher clonogenic potential; show an equivalent proportion of cells with putative stem cell surface markers; show enhanced matrix mineralization capability; have enhanced angiogenic marker expression and retain the inflammatory phenotype in vitro characteristic of superficial caries lesions in vivo. Our findings suggest that cDPCs may be used for further investigation of the cross talk between inflammatory, angiogenic and mineralization pathways in repair of carious pulp. In addition cells derived from carious pulps (almost always discarded) may have potential for future applications in mineralized tissue repair and regeneration.

IFN-γ regulates human dental pulp stem cells behavior via NF-κB and MAPK signaling

During caries, dental pulp expresses a range of pro-inflammatory cytokines in response to the infectious challenge. Interferon gamma (IFN-γ) is a dimerized soluble cytokine, which is critical for immune responses. Previous study has demonstrated that IFN-γ at relative high concentration (100 ng/mL) treatment improved the impaired dentinogenic and immunosuppressive regulatory functions of disease-derived dental pulp stem cells (DPSCs). However, little is known about the regulatory effects of IFN-γ at relative low concentration on healthy DPSC behavior (including proliferation, migration, and multiple-potential differentiation). Here we demonstrate that IFN-γ at relatively low concentrations (0.5 ng/mL) promoted the proliferation and migration of DPSCs, but abrogated odonto/osteogenic differentiation. Additionally, we identified that NF-κB and MAPK signaling pathways are both involved in the process of IFN-γ-regulated odonto/osteogenic differentiation of DPSCs. DPSCs treated with IFN-γ and supplemented with pyrrolidine dithiocarbamate (PDTC, an NF-κB inhibitor) or SB203580 (a MAPK inhibitor) showed significantly improved potential for odonto/osteogenic differentiation of DPSCs both in vivo and in vitro. These data provide important insight into the regulatory effects of IFN-γ on the biological behavior of DPSCs and indicate a promising therapeutic strategy for dentin/pulp tissue engineering in future endodontic treatment.

The Regulatory Effects of Long Noncoding RNA-ANCR on Dental Tissue-Derived Stem Cells

Long noncoding RNAs (lncRNA) have been recognized as important regulators in diverse biological processes, such as transcriptional regulation, stem cell proliferation, and differentiation. Previous study has demonstrated that lncRNA-ANCR (antidifferentiation ncRNA) plays a key role in regulating the proliferation and osteogenic differentiation of periodontal ligament stem cells (PDLSCs). However, little is known about the role of ANCR in regulating other types of dental tissue-derived stem cells (DTSCs) behaviours (including proliferation and multiple-potential of differentiation). In this study, we investigated the regulatory effects of lncRNA-ANCR on the proliferation and differentiation (including osteogenic, adipogenic, and neurogenic differentiation) of DTSCs, including dental pulp stem cells (DPSCs), PDLSCs, and stem cells from the apical papilla (SCAP) by downregulation of lncRNA-ANCR. We found that downregulation of ANCR exerted little effect on proliferation of DPSCs and SCAP but promoted the osteogenic, adipogenic, and neurogenic differentiation of DTSCs. These data provide an insight into the regulatory effects of long noncoding RNA-ANCR on DTSCs and indicate that ANCR is a very important regulatory factor in stem cell differentiation.

SIRT1 was involved in TNF-α-promoted osteogenic differentiation of human DPSCs through Wnt/β-catenin signal

Dental pulp stem cells (DPSCs), as one type of mesenchymal stem cells (MSCs), have the capability of self-renewal and differentiating along the various directions, including osteogenic, chondrogenic, neurogenic, and adipogenic. We previously study and found that tumor necrosis factor-α (TNF-α) promoted osteogenic differentiation of human DPSCs via the Wnt/β-catenin signaling pathway in low concentration while inhibited that in high concentration. In the abovementioned process, we found that sirtuin-1 (SIRT1) had the same change compared with the characteristic protein of bone formation, such as bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (Runx2), and collagen I (COL1). We asked whether SIRT1 could regulate osteogenesis of DPSCs. In inflammation microenvironment constructed by TNF-α, we tested the expression changing of SIRT1 and analyzed the function of SIRT1 on osteogenic differentiation of DPSCs. SIRT1 deacetylated β-catenin, and then promote its accumulation in the nucleus. Accumulated β-catenin can lead to transcription of osteogenic characteristic genes. Using the activator of SIRT1, resveratrol, could promote the above-mentioned process of osteogenic differentiation. SIRT1 could regulate osteogenesis of DPSCs through Wnt/β-catenin signal. SIRT1, as a regulator of differentiation of DPSCs, may be a new target for cell-based therapy in oral diseases and other regenerative medicine.

Influence of N-methyl pyrrolidone on the activity of the pulp-dentine complex and bone integrity during osteoporosis

AIM

To analyse the effect of systemic application of N-methyl pyrrolidone (NMP) on the pulp-dentine complex and on the jawbone of ovariectomized rats.

METHOD

Female Sprague Dawley rats were randomly divided into a Sham-operated group (Sham n = 6) and an oestrogen depletion by ovariectomy (OVX n = 12) group. In 6 of the ovariectomized animals, N-methyl pyrrolidone (NMP) in phosphate-buffered saline (PBS) was administered systemically weekly by intraperitoneal injection (i.p.); the other 6 were injected with PBS (Veh). After 15 weeks of injections, the jaw bones were collected and pulps extracted from the incisors teeth. Histology was used to determine pre-dentine thickness in teeth and radiography to determine alveolar bone mass. Immunohistological staining and RT-PCR were performed to verify the presence and localization of the odontoblast-specific dentine sialoprotein and to quantify its expression in the dentine-pulp complex. Mandibular cortical width and mandibular height were evaluated by means of X-ray analysis. Statistical analysis was performed with analysis of variance (anova).

RESULTS

Both pre-dentine (P = 0.029) and alveolar bone structures (P = 0.049) were significantly reduced due to oestrogen deficiency in OVX Veh and OVX. NMP treatment normalized these parameters to the Sham level. DSPP expression in OVX NMP animals was significantly higher (P = 0.046) than in OVX Veh. X-ray analysis confirmed that ovariectomy significantly reduced the mandibular cortical width in the OVX Veh group compared to the Sham Veh and OVX NMP (P = 0.020).

CONCLUSION

N-methyl pyrrolidone (NMP) had a remarkable anti-osteoporotic ability preserving activity in the pulp-dentine complex and preventing jawbone loss. These effects make NMP a promising candidate for the preservation of the activity of the pulp-dentine complex and jawbone thickness in post-menopausal females.

17β-Estradiol induces odontoblastic differentiation via activation of the c-Src/MAPK pathway in human dental pulp cells

The present study is aimed at investigating the effects of the exogenous estrogen 17β-estradiol (E2) on odontoblastic differentiation in human dental pulp cells (HDPCs) immotalized with hTERT gene and their molecular mechanism. Proliferation was detected by BrdU assay, and odontoblast differentiation induction was evaluated by the expression of dentin sialophosphoprotein (DSPP), dentin sialoprotein (DSP) and dentin matrix protein1 (DMP1), and alkaline phosphatase (ALP) activity and mineralization. Estrogen receptor-α (ER-α), c-Src, and mitogen-activated protein kinases (MAPKs) were examined and their inhibitors were used to determine the roles on odontogenic induction. E2 significantly promoted the HDPC proliferation, which was mediated by extracellular signal-related kinase 1/2. E2 upregulated DSPP, DSP, and DMP1 as the odontogenic differentiation markers and enhanced ALP activity and mineralization. E2 increased phosphorylation of ER-α and fulvestrant, an ER downregulator, significantly downregulated DSPP, DMP1, and DSP induced by E2. Moreover, E2 treatment activated c-Src and MAPKs upon odontogenic induction, whereas chemical inhibition of c-Src and MAPKs decreased expression of DSPP, DMP1, and DSP and mineralization augmented by E2. Moreover, fulvestrant reduced E2-induced phosphorylation of c-Src and MAPK and inhibition of c-Src by PP2 attenuated activation of MAPKs during E2-induced odontoblastic differentiation. Taken together, these results indicated that E2 stimulates odontoblastic differentiation of HDPCs via coordinated regulation of ER-α, c-Src, and MAPK signaling pathways, which may play a key role in the regeneration of dentin.

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

Dental pulp stem cells (DPSCs) were a clonogenic, highly proliferative cells capable of self-renewal and multi-lineage differentiation including chondrocytes, adipocytes, neural cells and osteoblasts, which make it an attractive choice for bone regeneration and repair of craniofacial defects. Recent studies showed that tumor necrosis factor α (TNF-α) may affect osteoclastogenesis and bone formation. However, the effect and mechanism of TNF-α on DPSCs is not clear. In this study, we found that low dose TNF-α promoted mineralization and high dose TNF-α suppressed osteogenic differentiation of DPSCs. Levels of ALP, Osteopontin, Osteocalcin, Osterix and Runx2 were up-regulated in DPSCs treated with TNF-α at low concentration, while down-regulated in DPSCs treated with TNF-α at high concentration. Blockade of Wnt/β-catenin signaling reversed the inhibitory effect observed on osteogenic differentiation of DPSCs treated with TNF-α at high concentration. In addition, we did not detect any proliferative effect of TNF-α on DPSCs by cell cycle and cell counts analysis. In summary, our data suggested that high concentration TNF-α suppressed mineralization and mineralization-related gene expressions through the Wnt/β-catenin signaling in DPSCs. Our findings may provide a foundation for autologous transplantation of DPSCs.

Comparative analysis of proliferation and differentiation potentials of stem cells from inflamed pulp of deciduous teeth and stem cells from exfoliated deciduous teeth

Stem cells isolated from exfoliated deciduous teeth (SHEDs) are highly capable of proliferation and differentiation, and they represent good cell sources for mesenchymal stem cell- (MSC-) mediated dental tissue regeneration, but the supply of SHEDs is limited. A previous study found that stem cells could be isolated from inflamed tissues, but it is unknown whether primary dental pulp diagnosed with irreversible pulpitis might contain stem cells with appropriate tissue regeneration capacity. In this study, we aimed to isolate stem cells from both inflamed pulps of deciduous teeth (SCIDs) and SHEDs from Chinese children and to compare their proliferation and differentiation potentials. Our results showed that SCIDs were positive for cell surface markers, including CD105, CD90, and CD146, and they had high proliferation ability and osteogenic, adipogenic, and chondrogenic differentiation potentials. There was no significant difference in proliferation and differentiation potentials between SCIDs and SHEDs. The mRNA of inflammatory factors, including IL-1β, IL-6, and TNF-α, was expressed at similar levels in SCIDs and SHEDs, but SCIDs secreted more TNF-α protein. In conclusion, our in vitro results showed that SCIDs have proliferation and differentiation potentials similar to those of SHEDs. Thus, SCIDs represent a new potentially applicable source for MSC mediated tissue regeneration.

A short-term treatment with tumor necrosis factor-alpha enhances stem cell phenotype of human dental pulp cells

Introduction

During normal pulp tissue healing, inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) or interleukins, act in the initial 48 hours (inflammatory phase) and play important roles not only as chemo-attractants of inflammatory cells and stem/progenitor cells but also in inducing a cascade of reactions toward tissue regeneration or reparative dentin formation or both. Previous reports have shown that inflammatory cytokines regulate the differentiation capacity of dental pulp stem/progenitor cells (DPCs), but none has interrogated the impact of these cytokines on the stem cell phenotype of stem/progenitor cells. This study investigated the effects of a short-term treatment with TNF-α on the stem cell phenotype and differentiation ability of human DPCs.

Methods

An in vivo mouse model of pulp exposure was performed for analysis of expression of the mesenchymal stem cell marker CD146 in DPCs during the initial stage of inflammatory response. For in vitro studies, human DPCs were isolated and incubated with TNF-α for 2 days and passaged to eliminate TNF-α completely. Analysis of stem cell phenotype was performed by quantification of cells positive for mesenchymal stem cell markers SSEA-4 (stage-specific embryonic antigen 4) and CD146 by flow cytometry as well as by quantitative analysis of telomerase activity and mRNA levels of OCT-4 and NANOG. Cell migration, colony-forming ability, and differentiation toward odontogenesis and adipogenesis were also investigated.

Results

The pulp exposure model revealed a strong staining for CD146 during the initial inflammatory response, at 2 days after pulp exposure. In vitro experiments demonstrated that a short-term (2-day) treatment of TNF-α increased by twofold the percentage of SSEA-4⁺ cells. Accordingly, STRO-1, CD146, and SSEA-4 protein levels as well as OCT-4 and NANOG mRNA levels were also significantly upregulated upon TNF-α treatment. A short-term TNF-α treatment also enhanced DPC function, including the ability to form cell colonies, to migrate, and to differentiate into odontogenic and adipogenic lineages.

Conclusions

A short-term treatment with TNF-α enhanced the stem cell phenotype, migration, and differentiation ability of DPCs.

Inflammation-related DNA damage and expression of CD133 and Oct3/4 in cholangiocarcinoma patients with poor prognosis

Nitrative and oxidative DNA damage plays an important role in inflammation-related carcinogenesis. Chronic inflammation such as parasite infection and primary sclerosing cholangitis can be an etiological factor of cholangiocarcinoma. Using a proteomic approach and double-fluorescent staining, we identified high expression and colocalization of albumin and cytokeratin-19 in liver fluke-associated cholangiocarcinoma tissues, compared with normal livers from cholangiocarcinoma patients and cadaveric donors, respectively. Albumin was detected not only in cells of hyperplastic bile ducts and cholangiocarcinoma, but also in liver stem/progenitor cell origin, such as canal of Hering, ductules, and ductular reactions, suggesting the involvement of stem/progenitor cells in cholangiocarcinoma development. To clarify the involvement of liver stem/progenitor cells in cholangiocarcinoma, we examined several stem/progenitor cell markers (CD133, CD44, OV6, and Oct3/4) in cholangiocarcinoma tissues analyzed by immunohistochemical staining, and measured 8-oxodG levels by using HPLC-ECD as an inflammation-related DNA lesion. In addition, a stem/progenitor cell factor Bmi1, 8-nitroguanine (formed during nitrative DNA damage), DNA damage response (DDR) proteins (phosphorylated ATM and γ-H2AX), and manganese-SOD (Mn-SOD) were analyzed by immunohistochemistry. Stem/progenitor cell markers (CD133, OV6, CD44, and Oct3/4) were positively stained in 56, 38, 47, and 56% of 34 cholangiocarcinoma cases, respectively. Quantitative analysis of 8-oxodG revealed significantly increased levels in CD133- and/or Oct3/4-positive tumor tissues compared to negative tumor tissues, as well as 8-nitroguanine formation detected by immunohistochemistry. In the cases of CD44- and/or OV6-positive tissue, no significant difference was observed. Cholangiocarcinoma patients with CD133- and/or Oct3/4-positive tumor tissues showed significantly lower expression of Mn-SOD and higher DDR protein, γ-H2AX. Moreover, CD133- and/or Oct3/4-positive cholangiocarcinoma patients had significant associations with tumor histology types, tumor stage, and poor prognoses. Our results suggest that CD133 and Oct3/4 in cholangiocarcinoma are associated with increased formation of DNA lesions and the DDR protein, which may be involved in genetic instability and lead to cholangiocarcinoma development with aggressive clinical features.

10(-7) m 17β-oestradiol enhances odonto/osteogenic potency of human dental pulp stem cells by activation of the NF-κB pathway

OBJECTIVES

Oestrogen has been proven to significantly enhance osteogenic potency, while oestrogen deficiency usually leads to impaired osteogenic differentiation of mesenchymal stem cells. However, little is known concerning direct effects of oestrogen on differentiation of human dental pulp stem cells (DPSCs).

MATERIALS AND METHODS

In this study, human DPSCs were isolated and treated with 10(-7)  m 17β-oestradiol (E2). Alkaline phosphatase (ALP) assay and alizarin red staining were performed.

RESULTS

Alkaline phosphatase and alizarin red showed that E2 treatment significantly enhanced ALP activity and mineralization ability of DPSCs, but had no effect on cell proliferation. Real-time RT-PCR and western blot assay demonstrated that odonto/osteogenic markers (ALP, RUNX2/RUNX2, OSX/OSX, OCN/OCN and DSPP/DSP) were significantly upregulated in the cells after E2 treatment. Moreover, phosphorylation of cytoplasmic IκBα/P65 and expression of nuclear P65 were enhanced in a time-dependent manner following E2 treatment, suggesting activation of NF-κB signaling. Conversely, inhibition of the NF-κB pathway suppressed E2-mediated upregulation of odonto/osteogenic markers, indicating that the NF-κB pathway was pivotal for E2-mediated differentiation.

CONCLUSION

These findings provide evidence that 10(-7)  m 17β-oestradiol promoted odonto/osteogenic differentiation of human DPSCs via activation of the NF-κB signaling pathway.

TNF-α triggers osteogenic differentiation of human dental pulp stem cells via the NF-κB signalling pathway

Dental pulp stem cells (DPSCs) are a type of mesenchymal stem cells (MSCs) characterised by self-renewal and multi-lineage differentiation, including chondrocytes, adipocytes, neural cells and osteoblasts, which make it an attractive choice for tissue engineering purposes. Tumour necrosis factor α (TNF-α) had the positive effect on the mineralisation of bone marrow MSCs and stromal cells derived from human adipose tissue. However, the effect of TNF-α on DPSCs is unclear. We found that TNF-α activated the NF-κB pathway during the osteogenic differentiation of DPSCs. TNF-α also increased mineralisation and the expression of bone morphogenetic protein 2 (BMP2), alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2) and collagen type I (COL I) during this process. PDTC, an NF-κB inhibitor, blocked the osteogenic differentiation induced by TNF-α. No effect of TNF-α on proliferation of DPSCs or cell cycle was detected. In summary, TNF-α promotes mineralisation and mineralisation-related gene expression through the NF-κB signalling pathway in DPSCs, which may provide a foundation for autologous transplantation of DPSCs.

Dental pulp stem cells from traumatically exposed pulps exhibited an enhanced osteogenic potential and weakened odontogenic capacity

OBJECTIVES

Traumatic pulp exposure can bring about some permanent damages to tooth tissues including dental pulps. This study was designed to evaluate the effects of traumatic pulp exposure on the osteo/odontogenic capacity of dental pulp stem cells (DPSCs).

METHODS

Rat incisors were artificially fractured and dental pulps were exposed to the oral environment for 48 h. Then, multi-colony-derived DPSCs from the injured pulps (iDPSCs) were isolated. Their osteo/odontogenic differentiation and the involvement of NF-κB pathway were subsequently investigated.

RESULTS

iDPSCs presented a lower proliferative capacity than normal DPSCs (nDPSCs), as indicated by MTT and FCM assay. ALP levels in iDPSCs were significantly higher (P<0.01) than those in nDPSCs. Alizarin red staining revealed that iDPSCs exhibited an increased capacity of calcium deposition. Moreover, iDPSCs expressed stronger osteogenic markers (Runx2/RUNX2 and Ocn/OCN) and less odontogenic gene/protein (Dspp/DSP) than nDPSCs in vitro. In vivo transplantation showed that nDPSCs implants generated the typical dentine-pulp complex while all iDPSCs pellets formed the osteodentin-like tissues which were immunopositive for OCN. Mechanistically, iDPSCs expressed the higher levels of cytoplasmic phosphorylated IκBα/P65 and nuclear P65 than nDPSCs, indicating an active cellular NF-κB pathway in iDPSCs. After the inhibition of NF-κB pathway, the osteogenic potential in iDPSCs was significantly down-regulated while odontogenic differentiation was up-regulated, as indicated by the decreased Alp/Runx2/Ocn and uprised Dspp expression.

CONCLUSIONS

Pulp exposure for 48 h decreased the odontogenic capacity and enhanced the osteogenic potential of DPSCs via the NF-κB signalling pathway.

Taking a deep look: modern microscopy technologies to optimize the design and functionality of biocompatible scaffolds for tissue engineering in regenerative medicine

This review focuses on modern nonlinear optical microscopy (NLOM) methods that are increasingly being used in the field of tissue engineering (TE) to image tissue non-invasively and without labelling in depths unreached by conventional microscopy techniques. With NLOM techniques, biomaterial matrices, cultured cells and their produced extracellular matrix may be visualized with high resolution. After introducing classical imaging methodologies such as µCT, MRI, optical coherence tomography, electron microscopy and conventional microscopy two-photon fluorescence (2-PF) and second harmonic generation (SHG) imaging are described in detail (principle, power, limitations) together with their most widely used TE applications. Besides our own cell encapsulation, cell printing and collagen scaffolding systems and their NLOM imaging the most current research articles will be reviewed. These cover imaging of autofluorescence and fluorescence-labelled tissue and biomaterial structures, SHG-based quantitative morphometry of collagen I and other proteins, imaging of vascularization and online monitoring techniques in TE. Finally, some insight is given into state-of-the-art three-photon-based imaging methods (e.g. coherent anti-Stokes Raman scattering, third harmonic generation). This review provides an overview of the powerful and constantly evolving field of multiphoton microscopy, which is a powerful and indispensable tool for the development of artificial tissues in regenerative medicine and which is likely to gain importance also as a means for general diagnostic medical imaging.

Estrogen deficiency inhibits the odonto/osteogenic differentiation of dental pulp stem cells via activation of the NF-κB pathway

Various factors can affect the functions of dental pulp stem cells (DPSCs). However, little knowledge is available about the effects of estrogen deficiency on the differentiation of DPSCs. In this study, an estrogen-deficient rat model was constructed and multi-colony-derived DPSCs were obtained from the incisors of ovariectomized (OVX) or sham-operated rats. Odonto/osteogenic differentiation and the possible involvement of the nuclear factor kappa B (NF-κB) pathway in the OVX-DPSCs/Sham-DPSCs of these rats were then investigated. OVX-DPSCs presented decreased odonto/osteogenic capacity and an activated NF-κB pathway, as compared with Sham-DPSCs. When the cellular NF-κB pathway was specifically inhibited by BMS345541, the odonto/osteogenic potential in OVX-DPSCs was significantly upregulated. Thus, estrogen deficiency down-regulated the odonto/osteogenic differentiation of DPSCs by activating NF-κB signaling and inhibition of the NF-κB pathway effectively rescued the decreased differentiation potential of DPSCs.

Changes in proliferation and osteogenic differentiation of stem cells from deep caries in vitro

INTRODUCTION

It is suggested that dental pulp stem cells are involved in tooth regeneration and play an important role in maintaining pulp homeostasis. Previously, normal dental pulps were more widely used for experimental models than carious dental pulps. The aim of this study was to isolate and culture the dental pulp stem cells from carious and normal teeth and to evaluate stem cell parameters.

METHODS

Pulp tissues were obtained and dissociated from normal and carious teeth. Single-cell suspensions were seeded into 6-well plates and purified by collecting multiple colonies. Normal dental pulp stem cells (DPSCs) and carious dental pulp stem cells (CDPSCs) were compared for morphologic appearance and for their capacity to differentiate into 3 lineages. Colony-forming and MTT assays, cell cycle analysis, gene expression, and alkaline phosphatase activity were also evaluated.

RESULTS

Stem cells were cultured successfully from normal and carious dental pulps. CDPSCs displayed increased proliferation ability compared with DPSCs. CDPSCs also showed enhanced ALP activity, mineralization ability, and expression of osteogenesis/dentinogenesis-related genes. All cultures differentiated into 3 cell types.

CONCLUSIONS

Our data suggest that caries as a local microenvironment should be taken into account when DPSCs are intended to be used for investigations and application. Furthermore, the mechanism of the underlying changes in cell properties requires further study.