Cell-Based Transplantation versus Cell Homing Approaches for Pulp-Dentin Complex Regeneration

Dental pulp regeneration strategies: A review of status quo and recent advances

Microorganisms, physical factors such as temperature or mechanical injury, and chemical factors such as free monomers from composite resin are the main causes of dental pulp diseases. Current clinical treatment methods for pulp diseases include the root canal therapy, vital pulp therapy and regenerative endodontic therapy. Regenerative endodontic therapy serves the purpose of inducing the regeneration of new functional pulp tissues through autologous revascularization or pulp tissue engineering. This article first discusses the current clinical methods and reviews strategies as well as the research outcomes regarding the pulp regeneration. Then the in vivo models, the prospects and challenges for regenerative endodontic therapy were further discussed.

Research and development of microenvironment's influence on stem cells from the apical papilla - construction of novel research microdevices: tooth-on-a-chip

Stem cells are crucial in tissue engineering, and their microenvironment greatly influences their behavior. Among the various dental stem cell types, stem cells from the apical papilla (SCAPs) have shown great potential for regenerating the pulp-dentin complex. Microenvironmental cues that affect SCAPs include physical and biochemical factors. To research optimal pulp-dentin complex regeneration, researchers have developed several models of controlled biomimetic microenvironments, ranging from in vivo animal models to in vitro models, including two-dimensional cultures and three-dimensional devices. Among these models, the most powerful tool is a microfluidic microdevice, a tooth-on-a-chip with high spatial resolution of microstructures and precise microenvironment control. In this review, we start with the SCAP microenvironment in the regeneration of pulp-dentin complexes and discuss research models and studies related to the biological process.

Regenerative endodontic therapy: From laboratory bench to clinical practice

BACKGROUND

Maintaining the vitality and functionality of dental pulp is paramount for tooth integrity, longevity, and homeostasis. Aiming to treat irreversible pulpitis and necrosis, there has been a paradigm shift from conventional root canal treatment towards regenerative endodontic therapy.

AIM OF REVIEW

This extensive and multipart review presents crucial laboratory and practical issues related to pulp-dentin complex regeneration aimed towards advancing clinical translation of regenerative endodontic therapy and enhancing human life quality.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this multipart review paper, we first present a panorama of emerging potential tissue engineering strategies for pulp-dentin complex regeneration from cell transplantation and cell homing perspectives, emphasizing the critical regenerative components of stem cells, biomaterials, and conducive microenvironments. Then, this review provides details about current clinically practiced pulp regenerative/reparative approaches, including direct pulp capping and root revascularization, with a specific focus on the remaining hurdles and bright prospects in developing such therapies. Next, special attention was devoted to discussing the innovative biomimetic perspectives opened in establishing functional tissues by employing exosomes and cell aggregates, which will benefit the clinical translation of dental pulp engineering protocols. Finally, we summarize careful consideration that should be given to basic research and clinical applications of regenerative endodontics. In particular, this review article highlights significant challenges associated with residual infection and inflammation and identifies future insightful directions in creating antibacterial and immunomodulatory microenvironments so that clinicians and researchers can comprehensively understand crucial clinical aspects of regenerative endodontic procedures.

Combined application of mesenchymal stem cells and different glucocorticoid dosing alleviates osteoporosis in SLE murine models

OBJECTIVE

Bone mesenchymal stem cells (BMSCs) have been tentatively applied in the treatment of glucocorticoid-induced osteoporosis (GIOP) and systemic lupus erythematosus (SLE). However, the effects of BMSCs on osteoporosis within the context of glucocorticoid (GC) application in SLE remain unclear. Our aim was to explore the roles of BMSCs and different doses of GC interventions on osteoporosis in SLE murine models.

METHODS

MRL/MpJ-Faslpr mice were divided into eight groups with BMSC treatment and different dose of GC intervention. Three-dimensional imaging analysis and hematoxylin and eosin (H&E) staining were performed to observe morphological changes. The concentrations of osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) in serum were measured by enzyme-linked immunosorbent assay (ELISA). The subpopulation of B cells and T cells in bone marrows and spleens were analyzed by flow cytometry. Serum cytokines and chemokines were assessed using Luminex magnetic bead technology.

RESULTS

BMSCs ameliorated osteoporosis in murine SLE models by enhancing bone mass, improving bone structure, and promoting bone formation through increased bone mineral content and optimization of trabecular morphology. BMSC and GC treatments reduced the number of B cells in bone marrows, but the effect was not significant in spleens. BMSCs significantly promoted the expression of IL-10 while reducing IL-18. Moreover, BMSCs exert immunomodulatory effects by reducing Th17 expression and rectifying the Th17/Treg imbalance.

CONCLUSION

BMSCs effectively alleviate osteoporosis induced by SLE itself, as well as osteoporosis resulting from SLE combined with various doses of GC therapy. The therapeutic effects of BMSCs appear to be mediated by their influence on bone marrow B cells, T cell subsets, and associated cytokines. High-dose GC treatment exerts a potent anti-inflammatory effect but may hinder the immunotherapeutic potential of BMSCs. Our research may offer valuable guidance to clinicians regarding the use of BMSC treatment in SLE and provide insights into the judicious use of GCs in clinical practice.

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.

Pulp Revascularization in an Autotransplanted Mature Tooth: Visualization with Magnetic Resonance Imaging and Histopathologic Correlation

Autotransplantation of a mature tooth usually leads to pulpal necrosis. Root canal treatment is recommended to prevent related inflammatory complications a few weeks after surgery. Extraoral root-end resection may facilitate reperfusion and obviate root canal treatment, but cannot be pictured with conventional dental radiography at this point in time. In the case of a lower mature transplanted molar, contrast-enhanced magnetic resonance imaging proved to be a feasible method for visualizing pulp revascularization just 4 weeks after autotransplantation. Consequently, root canal treatment was obviated. Nevertheless, the tooth had to be extracted 18 months postoperatively due to external cervical root resorption, probably caused by the extraction trauma. This allowed the histological processing and examination of the newly generated intracanal tissue. Uninflamed fibrovascular connective tissue was found, while odontoblasts or cementoblast-like cells were absent. These findings indicated that it was most likely stem cells from the bone marrow and the periodontal ligament that drove the regeneration.

Evaluation of postoperative pain and healing following regenerative endodontics using platelet-rich plasma versus conventional endodontic treatment in necrotic mature mandibular molars with chronic periapical periodontitis. A randomized clinical trial

AIM

To evaluate the post-operative pain and the healing of necrotic mature permanent mandibular molar teeth with peri-apical periodontitis after conventional endodontic treatment versus after platelet-rich plasma (PRP) revascularization.

METHODOLOGY

The protocol of this randomized clinical trial was registered at www.

CLINICALTRIALS

gov with identification number NCT03350841. Twenty-eight patients were included in the study after confirming the diagnosis clinically and radiographically. In the first visit, mandibular molar teeth of both groups were mechanically prepared. Double antibiotic paste was prepared and injected then the cavity that was sealed with glass ionomer. At the second visit, the patients were randomized either to control group where standard endodontic treatment was completed by lateral condensation technique or assigned to intervention group where PRP revascularization technique. The degree of spontaneous pain was assessed using numerical rating scale (NRS) pre-operatively, then post-operatively after 6, 12 h and daily for 5 days. Patients were given a placebo to be administrated in case of pain. An analgesic (ibuprofen 400mg) was prescribed in case of persistent pain. Clinical and radiographic healing was assessed after 6 and 12 months. All demographic, baseline and outcome data were collected and statistically analysed.

RESULTS

Regarding the post revascularization/obturation pain, there was no statistically significant difference between severity of pain in the two groups at all time intervals except after 12 h, revascularization group showed statistically significantly higher prevalence of no pain than endodontic treatment group. Regarding the healing; the periapical lesions decrease in size significantly from the pre-operative lesion size in both groups without significant difference between the both groups.

CONCLUSION

Within the limitation of this study, PRP revascularization could be an alternative treatment to root canal treatment but further randomized clinical trials with standardized techniques and long follow up periods are recommended for more reliable results.

Stem cell homing in periodontal tissue regeneration

The destruction of periodontal tissue is a crucial problem faced by oral diseases, such as periodontitis and tooth avulsion. However, regenerating periodontal tissue is a huge clinical challenge because of the structural complexity and the poor self-healing capability of periodontal tissue. Tissue engineering has led to advances in periodontal regeneration, however, the source of exogenous seed cells is still a major obstacle. With the improvement of in situ tissue engineering and the exploration of stem cell niches, the homing of endogenous stem cells may bring promising treatment strategies in the future. In recent years, the applications of endogenous cell homing have been widely reported in clinical tissue repair, periodontal regeneration, and cell therapy prospects. Stimulating strategies have also been widely studied, such as the combination of cytokines and chemokines, and the implantation of tissue-engineered scaffolds. In the future, more research needs to be done to improve the efficiency of endogenous cell homing and expand the range of clinical applications.

Biomolecule-Mediated Therapeutics of the Dentin–Pulp Complex: A Systematic Review

The aim of this systematic review was to evaluate the application of potential therapeutic signaling molecules on complete dentin-pulp complex and pulp tissue regeneration in orthotopic and ectopic animal studies. A search strategy was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement in the MEDLINE/PubMed database. Animal studies evaluating the application of signaling molecules to pulpectomized teeth for pulp tissue or dentin-pulp complex regeneration were included. From 2530 identified records, 18 fulfilled the eligibility criteria and were subjected to detailed qualitative analysis. Among the applied molecules, basic fibroblast growth factor, vascular endothelial growth factor, bone morphogenetic factor-7, nerve growth factor, and platelet-derived growth factor were the most frequently studied. The clinical, radiographical and histological outcome measures included healing of periapical lesions, root development, and apical closure, cellular recolonization of the pulp space, ingrowth of pulp-like connective tissue (vascularization and innervation), mineralized dentin-like tissue formation along the internal dentin walls, and odontoblast-like cells in contact with the internal dentin walls. The results indicate that signaling molecules play an important role in dentin/pulp regeneration. However, further studies are needed to determine a more specific subset combination of molecules to achieve greater efficiency towards the desired tissue engineering applications.

The role of complement C5a receptor in DPSC odontoblastic differentiation and in vivo reparative dentin formation

Therapeutic dentin regeneration remains difficult to achieve, and a majority of the attention has been given to anabolic strategies to promote dentinogenesis directly, whereas, the available literature is insufficient to understand the role of inflammation and inflammatory complement system on dentinogenesis. The aim of this study is to determine the role of complement C5a receptor (C5aR) in regulating dental pulp stem cells (DPSCs) differentiation and in vivo dentin regeneration. Human DPSCs were subjected to odontogenic differentiation in osteogenic media treated with the C5aR agonist and C5aR antagonist. In vivo dentin formation was evaluated using the dentin injury/pulp-capping model of the C5a-deficient and wild-type mice. In vitro results demonstrate that C5aR inhibition caused a substantial reduction in odontogenic DPSCs differentiation markers such as DMP-1 and DSPP, while the C5aR activation increased these key odontogenic genes compared to control. A reparative dentin formation using the C5a-deficient mice shows that dentin regeneration is significantly reduced in the C5a-deficient mice. These data suggest a positive role of C5aR in the odontogenic DPSCs differentiation and tertiary/reparative dentin formation. This study addresses a novel regulatory pathway and a therapeutic approach for improving the efficiency of dentin regeneration in affected teeth.