IGFBP5 enhances the dentinogenesis potential of dental pulp stem cells via JNK and ErK signalling pathways

Insulin-Like Growth Factor-Binding Protein 5 Promotes the Cell Proliferation and Osteogenic Potential of Dental Pulp Stem Cells Dependent on Its Nuclear Localisation Sequence

OBJECTIVES

Dental pulp stem cells (DPSCs) have been extensively used for tissue regeneration owing to their notable capabilities. Insulin-like growth factor-binding protein 5 (IGFBP5) regulates osteogenic differentiation of mesenchymal stem cells (MSCs); however, the underlying regulatory mechanisms require further investigation.

MATERIALS AND METHODS

Carboxyfluorescein succinimidyl ester, an alkaline phosphatase (ALP) activity assay and Alizarin Red staining were used to reveal the role of IGFBP5 in DPSCs. Protein expression levels were determined using western blotting. Immunofluorescence was used to observe cell sub-localisation. Subcutaneous transplantation in nude mice was used to observe the osteogenesis of DPSCs in vivo.

RESULTS

IGFBP5 enhanced the proliferation and osteogenic differentiation of DPSCs. Deletion of the nuclear localisation sequence (NLS) of IGFBP5 prevented its nuclear import and abolished all its promoting effects on DPSCs; ivermectin stimulation attenuated the enhancement of ALP activity by IGBFP5. Bone-like tissue formation promoted by IGFBP5 in vivo vanishes when the NLS is deleted. Inhibition of IGFBP5 nuclear import attenuated the IGFBP5-induced phosphorylation of JNK (p-JNK) and phosphorylated ERK (p-ERK) in DPSCs.

CONCLUSION

Our findings suggest that cell proliferation and osteogenic differentiation effects exerted by IGFBP5 on DPSCs are closely associated with their entry into the nucleus, thereby providing a novel potential target for tissue regeneration.

Dual-Fuel Propelled Nanomotors with Two-Stage Permeation for Deep Bacterial Infection in the Treatment of Pulpitis

Bacterial infection-induced inflammatory response could cause irreversible death of pulp tissue in the absence of timely and effective therapy. Given that, the narrow structure of root canal limits the therapeutic effects of passive diffusion-drugs, considerable attention has been drawn to the development of nanomotors, which have high tissue penetration abilities but generally face the problem of insufficient fuel concentration. To address this drawback, dual-fuel propelled nanomotors (DPNMs) by encapsulating L-arginine (L-Arg), calcium peroxide (CaO2 ) in metal-organic framework is developed. Under pathological environment, L-Arg could release nitric oxide (NO) by reacting with reactive oxygen species (ROS) to provide the driving force for movement. Remarkably, the depleted ROS could be supplemented through the reaction between CaO2 with acids abundant in the inflammatory microenvironment. Owing to high diffusivity, NO achieves further tissue penetration based on the first-stage propulsion of nanomotors, thereby removing deep-seated bacterial infection. Results indicate that the nanomotors effectively eliminate bacterial infection based on antibacterial activity of NO, thereby blocking inflammatory response and oxidative damage, forming reparative dentine layer to avoid further exposure and infection. Thus, this work provides a propagable strategy to overcome fuel shortage and facilitates the therapy of deep lesions.

Effects of Growth Factors on the Differentiation of Dental Stem Cells: A Systematic Review and Meta-analysis (Part I)

INTRODUCTION

To evaluate the biological interaction between dental stem cells (DSCs) and different growth factors in the field of regenerative endodontics.

METHODS

A systematic search was conducted in the electronic databases up to October 2021. This study followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Ex vivo studies evaluating the biological interactions of DSCs and growth factors were included. The meta-analysis was performed according to the type of growth factor. The outcomes were cell viability/ proliferation and mineralization. Standardized mean differences (SMDs) were estimated using the random-effect maximum-likelihood method (P < .05). Additional analysis was performed to find any potential source of heterogeneity.

RESULTS

Twenty articles were included in the systematic review; meta-analysis was performed for fibroblast growth factor-2 (FGF-2) and Transforming growth factor-ß1 (TGF-β1) (n = 5). Results showed that use of FGF-2 significantly increased cell proliferation on day 1-(SMD = 3.56, P = 0.00), 3-(SMD = 9.04, P = 0.00), 5-(SMD = 8.37, P = 0.01), and 7 (SMD=8.51, P=0.00) than the control group. TGF-ß1 increased alkaline phosphatase (ALP) activity more than control only on day 3 (SMD = 3.68, P = 0.02). TGF-β1 had no significant effect on cell proliferation on days 1 and 3 (P > 0.05) and on ALP activity on days 5 and 7 (P > 0.05). Meta-regression analysis showed that different covariates (i.e., cell type, passage number, and growth factors' concentration) could significantly influence the effect sizes at different follow- ups (P < 0.05).

CONCLUSION

Specific growth factors might enhance the proliferation and mineralization of DSCs; however, the obtained evidence was weak. Due to the high heterogeneity among the included studies, other growth factors' inhibitory/stimulatory effects on DSCs could not be evaluated.

GATA4 inhibits odontoblastic differentiation of dental pulp stem cells through targeting IGFBP3

OBJECTIVE

The odontogenic differentiation of human dental pulp stem cells (HDPSCs) is associated with reparative dentinogenesis. Transcription factor GATA binding protein 4 (GATA4) is proved to be essential for osteoblast differentiation and bone remodeling. This study clarified the function of GATA4 in HDPSCs odontoblast differentiation.

METHODS

The change in GATA4 expression during reparative dentin formation was detected by immunohistochemistry staining. The expression of GATA4 during HDPSCs odontoblastic differentiation was detected by western blot and quantitative polymerase chain reaction. The effect of GATA4 on odontoblast differentiation was investigated following overexpression lentivirus transfection. RNA sequencing, dual luciferase assay and chromatin immunoprecipitation (CHIP) were conducted to verify downstream targets of GATA4. GATA4 overexpression lentivirus and small interference RNA targeting IGFBP3 were co-transfected to investigate the regulatory mechanism of GATA4.

RESULTS

Upregulated GATA4 was observed during reparative dentin formation in vivo and the odontoblastic differentiation of HDPSCs in vitro. GATA4 overexpression suppressed the odontoblastic potential of HDPSCs, demonstrated by decreased alkaline phosphatase activity (p < 0.0001), mineralized nodules formation (p < 0.01), and odonto/osteogenic differentiation markers levels (p < 0.05). RNA sequencing revealed IGFBP3 was a potential target of GATA4. CHIP and dual luciferase assays identified GATA4 could activate IGFBP3 transcription. Additionally, IGFBP3 knockdown recovered the odontoblastic differentiation defect caused by GATA4 overexpression (p < 0.05).

CONCLUSIONS

GATA4 inhibited odontoblastic differentiation of HDPSCs via activating the transcriptional activity of IGFBP3, identifying its promising role in regulating HDPSCs odontoblast differentiation and reparative dentinogenesis.

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the rabbit jaw

BACKGROUND

Because of the low regeneration efficiency and unclear underlying molecular mechanism, tooth regeneration applications are limited. In this study, we explored the influence of residual periodontal ligament on the dentin regeneration potential of dental pulp stem cells (DPSCs) in the jaw.

METHODS

To establish a tooth regeneration model, the incisors of New Zealand white rabbits were extracted while preserving residual periodontal ligament, followed by the implantation of DPSCs. After 3 months, micro-computed tomography (micro-CT), stereomicroscopy and scanning electron microscopy (SEM) were used to observe the volume, morphology and microstructure of regenerated tissue. Histological staining and immunostaining analyses were used to observe the morphological characteristics and expression of the dentin-specific proteins DMP1 and DSPP. To explore the mechanism, DPSCs and periodontal ligament stem cells (PDLSCs) were cocultured in vitro, and RNA was collected from the DPSCs for RNA-seq and bioinformatic analysis.

RESULTS

The results of micro-CT and stereomicroscopy showed that the number of sites with regeneration and the volume of regenerated tissue in the DPSCs/PDL group (6/8, 1.07 ± 0.93 cm³) were larger than those in the DPSCs group (3/8, 0.23 ± 0.41 cm³). The results of SEM showed that the regenerated dentin-like tissue in the DPSCs and DPSCs/PDL groups contained dentin tubules. Haematoxylin and eosin staining and immunohistochemical staining indicated that compared with the DPSCs group, the DPSCs/PDL group showed more regular regenerated tissue and higher expression levels of the dentin-specific proteins DMP1 and DSPP (DMP1: P = 0.02, DSPP: P = 0.01). RNA-seq showed that the coculture of DPSCs with PDLSCs resulted in the DPSCs differentially expressing 427 mRNAs (285 upregulated and 142 downregulated), 41 lncRNAs (26 upregulated and 15 downregulated), 411 circRNAs (224 upregulated and 187 downregulated), and 19 miRNAs (13 upregulated and 5 downregulated). Bioinformatic analysis revealed related Gene Ontology function and signalling pathways, including extracellular matrix (ECM), tumour necrosis factor (TNF) signalling and chemokine signalling pathways.

CONCLUSIONS

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the jaw. RNA-seq and bioinformatic analysis revealed that ECM, TNF signalling and chemokine signalling pathways may represent the key factors and signalling pathways.

Administration of Epidermal Growth Factor (EGF) and Basic Fibroblast Growth Factor (bFGF) to Induce Neural Differentiation of Dental Pulp Stem Cells (DPSC) Isolates

The aging populations in many countries have developed many chronic illnesses and diseases, including chronic neurologic conditions such as Parkinson's and Azheimer's diseases. Many new lines of research and treatment are focusing on the potential for neurologic regeneration using mesenchymal stem cells (MSCs) in the rapidly growing field of regenerative medicine. This may include dental pulp stem cells (DPSCs), which have recently been demonstrated to produce neuronal precursors. Based upon this evidence, the primary aim of this study was to determine if the growth factors used in MSC-based studies are sufficient to induce neuronal differentiation among DPSCs. Using an existing biorepository, n = 16 DPSC isolates were thawed and cultured for this study, which revealed several subpopulations of rapid-, intermediate-, and slowly dividing DPSCs. Administration of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) were sufficient to induce differential changes in growth and viability mainly among some of the rapidly growing DPSCs (n = 4). These phenotypic changes included expression of neural differentiation markers including Sox1, Pax6 and NF-M, which were observed only among those DPSC isolates not expressing early odontoblast-specific biomarkers such as ALP and DSPP. Future studies will be needed to confirm if these methods are sufficient to induce consistent and reliable induction of DPSCs towards neuronal specific differentiation.

Neural Regeneration in Regenerative Endodontic Treatment: An Overview and Current Trends

Pulpal and periapical diseases are the most common dental diseases. The traditional treatment is root canal therapy, which achieves satisfactory therapeutic outcomes-especially for mature permanent teeth. Apexification, pulpotomy, and pulp revascularization are common techniques used for immature permanent teeth to accelerate the development of the root. However, there are obstacles to achieving functional pulp regeneration. Recently, two methods have been proposed based on tissue engineering: stem cell transplantation, and cell homing. One of the goals of functional pulp regeneration is to achieve innervation. Nerves play a vital role in dentin formation, nutrition, sensation, and defense in the pulp. Successful neural regeneration faces tough challenges in both animal studies and clinical trials. Investigation of the regeneration and repair of the nerves in the pulp has become a serious undertaking. In this review, we summarize the current understanding of the key stem cells, signaling molecules, and biomaterials that could promote neural regeneration as part of pulp regeneration. We also discuss the challenges in preclinical or clinical neural regeneration applications to guide deep research in the future.

Insulin-binding protein-5 down-regulates the balance of Th17/Treg

The inflammatory response plays critical important role in tissue hemostasis. Our previous study showed insulin-binding protein-5 (IGFBP5) could enhance the regeneration of tissue defect under inflammation condition, but the function of IGFBP5 in controlling inflammation and regulating immune responses remains unclear. In present study, we studied the regulatory effect of IGFBP5 on T cell immune response in vitro, and the maintenance of Th17/Treg balance in vivo by using dextran sulfate sodium salt (DSS)-induced colitis in mice. The results showed that IGFBP5 inhibited the differentiation of CD4⁺ T cells into Th17 subset while promoted its differentiation into Treg subsets. Further results of animal experiments demonstrated that recombinant IGFBP5 reversed the imbalance of Th17/Treg and alleviated the severity of DSS-induced colitis. The percentage of Th17 cells decreased and the percentage of Treg cells increased in the inflamed colon tissue and mesenteric lymph nodes of mice with colitis after IGFBP5 treatment. Besides, pro-inflammatory cytokines such as TNF-α, IL-1β and IFN-γ in serum were suppressed after the treatment of IGFBP5. Moreover, the function of IGFBP5 in regulating Th17/Treg balance could be inhibited by the inhibitors of ERK or JNK pathway. In conclusion, all these data showed that IGFBP5 could regulate Th17/Treg balance via ERK or JNK pathways. The findings of our study provide a theoretical basis for the application of IGFBP5 in inflammatory diseases.

Atlas of human dental pulp cells at multiple spatial and temporal levels based on single-cell sequencing analysis

The dental pulp plays a crucial role in the long-term maintenance of tooth function. The progress of endodontic treatment and pulp tissue regeneration engineering has made pulp-regeneration therapy promising in clinical practice. However, the mechanisms of pulp regeneration and the role of dental stem cells in development and regeneration have not been fully elucidated. Bridging the gaps between clinical operation and basic research is urgently needed. With the application of single-cell sequencing technology in dental research, the landscapes of human dental pulp cells have begun being outlined. However, the specific cellular heterogeneity of dental pulp cells, especially that of dental stem cells, at different spatial and temporal levels, is still unclear. In this study, we used single-cell RNA sequencing analysis of pulp samples at four different developmental stages and combined the findings with immunohistochemical staining to explore the development of dental pulp and stem cells. The results revealed temporal changes in the proportion of pulp cells during development. For example, mononuclear phagocytes accounted for a higher proportion in early samples. Odontoblasts identified by DMP1 had a higher expression of ion channel-related and neurodevelopment-related genes. Subpopulations were identified in fibroblasts, odontoblasts, and mesenchymal stem cells. We identified a subclass of odontoblasts that expresses DGKI and RRBP1 present in early developmental samples. A population of earlier mesenchymal stem cells expressed the SEPTIN gene, which may have greater proliferative and differentiation potential. Furthermore, dental pulp stem cells can differentiate into two directions: mineralization and myogenesis. In summary, the specific cellular heterogeneity of dental pulp cells was revealed at different spatial and temporal levels. These findings may shed light on the mechanism of tooth development. The gene expression profile of developing pulp cells may help to select cells for regenerative engineering and improve the success of dental pulp regeneration.

Cytokine co-stimulation effect on odontogenic differentiation of stem cells

OBJECTIVE

The study aims to evaluate the effect of bone morphogenetic protein-2 (BMP-2) and transforming growth factor-beta 1 (TGF-β1) co-stimulation on odontogenic differentiation of human dental pulp stem cells (hDPSCs).

MATERIALS AND METHODS

The viability/proliferation of hDPSCs treated with BMP-2 (group B), TGF-β1 (group T), or BMP-2/TGF-β1 (group BT) were evaluated. The experiments on odontogenic differentiation were done for 14 days. The following subgroups were added to investigate the effect of co-stimulation with different timing: subgroup B1, TGF-β1 co-stimulation in the first week; subgroup B2, TGF-β1 co-stimulation in the second week; subgroup T1, BMP-2 co-stimulation in the first week; and subgroup T2, BMP-2 co-stimulation in the second week. The mineralization was assessed using alizarin red staining. The expression of following genes was assessed using quantitative real-time polymerase chain reaction: dentin sialophosphoprotein (DSPP), dentin matrix protein-1 (DMP1), osteopontin (OPN), and alkaline phosphatase.

RESULTS

All groups showed viability similar to the control group (P > .05). The greater mineralization was detected in B groups on day 14. The expressions of DSPP, DMP-1, and OPN increased on day 14 (P < .05). In the combination groups, the higher expressions of DSPP and DMP-1 were observed in subgroups B1 and B2 than groups B and T (P < .05).

CONCLUSIONS

BMP-2 was the key in odontogenic differentiation of hDPSCs, which was further enhanced by co-stimulation with TGF-β1. Continuous stimulation with TGFβ-1 did not improve the differentiation of hDPSCs.

CLINICAL RELEVANCE

Combined use of the BMP-2 and TGFβ-1 at the specific sequence can provide a tissue engineering approach for the future guided dentin regeneration.

Meeting the challenges and clinical requirements for dental regeneration; the New Zealand experience

Disease and trauma leading to tooth loss and destruction of supporting bone is a significant oral handicap, which may be addressed through surgical therapies that aim to regenerate the lost tissue. Whilst complete regeneration of teeth is still aspirational, regeneration of supporting structures (dental pulp, cementum, periodontal ligament, bone) is becoming commonplace, both for teeth and for titanium dental implants that are used to replace teeth. Most grafting materials are essentially passive, however the next generation of oral regenerative devices will combine non-antibiotic antimicrobials and/or osteogenic or inductive factors and/or appropriate multipotential stem cells. The review gives an overview of the approaches taken, including fabrication of novel scaffolds, incorporation of growth factors and cell-based therapies, and discusses the preclinical animal models we employ in the development pathway.

Salidroside promotes the osteogenic and odontogenic differentiation of human dental pulp stem cells through the BMP signaling pathway

Regenerative endodontics, as an alternative approach, aims to regenerate dental pulp-like tissues and is garnering the attention of clinical dentists. This is due to its reported biological benefits for dental therapeutics. Stem cells and their microenvironment serve an important role in the process of pulp regeneration. Regulation of the stem cell microenvironment and the directed differentiation of stem cells is becoming a topic of intensive research. Salidroside (SAL) is extracted from the root of Rhodiola rosea and it has been reported that SAL exerts antiaging, neuroprotective, hepatoprotective, cardioprotective and anticancer effects. However, the ability of SAL to regulate the osteo/odontogenic differentiation of hDPSCs remains to be elucidated. In the present study, the effect of SAL on the proliferation and osteogenic/odontogenic differentiation of human dental pulp stem cells (hDPSCs) was investigated. This was achieved by performing CCK-8 ARS staining assay, reverse transcription-quantitative PCR to detect mRNA of ALP, OSX, RUNX2, OCN, DSPP and BSP, western blotting to detect the protein of MAPK, Smad1/5/8, OSX, RUNX2, BSP and GAPDH and immunofluorescence assays to detect DSPP. The results indicated that SAL promoted the cell viability and the osteogenic/odontogenic differentiation of hDPSCs whilst increasing the expression of genes associated with osteogenic/odontogenic differentiation by ARS staining assay. In addition, SAL promoted osteogenic and odontogenic differentiation by activating the phosphorylation of Smad1/5/8. Collectively, these findings suggest that SAL promoted the osteogenic and odontogenic differentiation of hDPSCs activating the BMP signaling pathway.

Overexpression of long noncoding RNA MCM3AP-AS1 promotes osteogenic differentiation of dental pulp stem cells via miR-143-3p/IGFBP5 axis

MCM3AP-AS1 regulates the cartilage repair in osteoarthritis, but how it regulates osteogenic differentiation of dental pulp stem cells (DPSCs) remains to be determined. DPSCs were isolated and induced for osteogenic differentiation. MCM3AP-AS1 expression was increased along with the osteogenic differentiation of DPSCs, whose expression was positive correlated with those of OCN, alkaline phosphatase (ALP) and RUNX2. On contrary, miR-143-3p expression was decreased along with the osteogenic differentiation and was negatively correlated with those of OCN, ALP and RUNX2. Dual-luciferase reporter gene assay showed that miR-143-3p can be negatively regulated by MCM3AP-AS1 and can regulate IGFBP5. MCM3AP-AS1 overexpression increased the expression levels of osteogenesis-specific genes, ALP activity and mineralized nodules during DPSC osteogenic differentiation, while IGFBP5 knockdown or miR-143-3p overexpression counteracted the effect of MCM3AP-AS1 overexpression in DPSCs. Therefore, this study demonstrated the role of MCM3AP-AS1/miR-143-3p/IGFBP5 axis in regulating DPSC osteogenic differentiation.

An In Vitro Study of the Effects of Crocin on the Modulation of DSPP, VEGF-A, HLA-G5, STAT3 and CD200 Expression in Human Dental Pulp Stem Cells

Dental pulp stem cells (DPSCs) have been recommended as promising candidate for cell-based therapeutic applications due to high potentials in tissue repair/regeneration and modulation of immune responses. The gene expression change strategy by natural plant enhancers is an available opportunity to improve the stemness properties of these cells. The objective of this research was the evaluation of Crocin effects (saffron plant's bioactive compound) on immunoregulation and tissue regeneration-related biomarkers expression in human DPSCs. Based on the results of cell viability assay, application of 400 μM and lower concentrations of Crocin had no toxic effects on DPSCs; however, the time-dependent cytotoxic effects were observed at higher concentrations. This study, probably for the first time, detected the surface expression of CD200 in DPSCs with a slight time-dependent upward trend and reported that treatment with Crocin could increase expression of this macromolecule up to many times over. Also, it revealed that this carotenoid significantly led to the time-dependent upregulation of dentin sialophosphoprotein, vascular endothelial growth factor A, human leukocyte antigen-G5, and signal transducer and activator of transcription-3 messenger ribonucleic acids (mRNAs); however, this significant upregulation for STAT3 occurred, followed by a remarkable reduction. The results of this study indicated that cell treatment with Crocin may be effective in improving the stemness capacities of DPSCs. Therefore, the study provided basis for more insights into the biological effects of Crocin on DPSCs that it may aid in the future improvement of mesenchymal stem cell-based therapies.

The role of insulin-like growth factors in modulating the activity of dental mesenchymal stem cells

Regenerative treatment protocols are an exciting prospect in the management of oral pathology, as they allow for tissues to be restored to their original form and function, as compared to the reparative healing mechanisms which currently govern the outcomes of the majority of dental treatment. Stem cell therapy presents with a great deal of untapped potential in this pursuit of tissue regeneration, and, in particular, mesenchymal stem cells (MSCs) derived from dental tissues are of specific relevance with regards to their applications in engineering craniofacial tissues. A number of mediatory factors are involved in modulating the actions of dental MSCs, and, of these, insulin like growth factors (IGFs) are known to have potent effects in governing the behavior of these cells. The IGF family comprises a number of primary ligands, receptors, and binding proteins which are known to modulate the key properties of dental MSCs, such as their proliferation rates, differentiation potential, and mineralisation. The aims of this review are three-fold: (i) to present an overview of dental MSCs and the role of growth factors in modulating their characteristics, (ii) to discuss in greater detail the specific role of IGFs and the benefits they may convey for tissue engineering, and (iii) to provide a summary of potential for in vivo clinical translation of the current in vitro body of evidence.