Platelet-rich plasma enhances the differentiation of dental pulp progenitor cells into odontoblasts

Biomaterial scaffolds for clinical procedures in endodontic regeneration

Regenerative endodontic procedures have been rapidly evolving over the past two decades and are employed extensively in clinical endodontics. These procedures have been perceived as valuable adjuvants to conventional strategies in the treatment of necrotic immature permanent teeth that were deemed to have poor prognosis. As a component biological triad of tissue engineering (i.e., stem cells, growth factors and scaffolds), biomaterial scaffolds have demonstrated clinical potential as an armamentarium in regenerative endodontic procedures and achieved remarkable advancements. The aim of the present review is to provide a broad overview of biomaterials employed for scaffolding in regenerative endodontics. The favorable properties and limitations of biomaterials organized in naturally derived, host-derived and synthetic material categories were discussed. Preclinical and clinical studies published over the past five years on the performance of biomaterial scaffolds, as well as current challenges and future perspectives for the application of biomaterials for scaffolding and clinical evaluation of biomaterial scaffolds in regenerative endodontic procedures were addressed in depth.

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Overview of biomaterials for scaffolding in regenerative endodontics are presented.

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Findings of preclinical and clinical studies on the performance of biomaterial scaffolds are summarized.

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Challenges and future prospects in biomaterial scaffolds are discussed.

Platelet-Rich Plasma Induces Autophagy and Promotes Regeneration in Human Dental Pulp Cells

Regenerative endodontic procedures using autologous platelet-rich plasma (PRP) can improve the biologic outcome of treatment. However, its mechanism of action on improving pulp regeneration is not fully elucidated. Autophagy was recently shown to be related to tissue repair and osteogenesis. Therefore, the objective of this study was to investigate the effect of PRP in dental pulp regeneration and to elucidate the role of autophagy involved in this process. Human dental pulp cells (hDPCs) were isolated from healthy dental pulp and co-cultured with an increasing concentration of PRP. Cellular migration and proliferation were determined by scratch assay, transwell assay, and cell-counting kit 8 assay. Osteogenic differentiation was clarified by using alkaline phosphatase staining, alizarin red staining, and real-time polymerase chain reaction (RT-PCR) to measure the gene expression levels of alkaline phosphatase, collagen-1, osteocalcin, dentin matrix protein 1, and dentin sialophosphoprotein. Autophagic bodies were observed by transmission electron microscopy and the expression of autophagy marker light chain 3B (LC3B) was determined by immunofluorescence staining. The mRNA and protein expression level of LC3B and Beclin-1 were quantified by qRT-PCR and western blotting. The effect of PRP on cellular migration, proliferation, and osteogenic differentiation was further investigated in the milieu of autophagy activator, rapamycin, and inhibitor, 3-methyladenine. Results showed that PRP promoted cell migration, proliferation, and osteogenic differentiation. Autophagic bodies were strongly activated and the expression level of LC3B and Beclin-1 was significantly promoted by PRP. Autophagy inhibition suppressed PRP-induced hDPCs migration, proliferation, and osteogenic differentiation, whereas autophagy activator substantially augmented PRP-stimulated migration, proliferation, and differentiation. Taken together, these findings suggested that PRP could effectively promote regenerative potentials associated with autophagy.

Effects of Platelet-Rich Plasma on Proliferation, Viability, and Odontogenic Differentiation of Neural Crest Stem-Like Cells Derived from Human Dental Apical Papilla

Objective

This study is aimed at evaluating the effects of platelet-rich plasma (PRP) on proliferation, viability, and odontogenic differentiation of neural crest stem-like cells (NCSCs) derived from human dental apical papilla.

Materials and Methods

Cells from apical papillae were obtained and then induced to form neural spheres. The expression of NCSC markers p75NTR and HNK-1 in neural sphere cells was detected by immunofluorescence staining. Human PRP was prepared by a 2-step centrifugation method and activated by CaCl₂ and thrombin. The concentrations of PDGF-BB and TGF-β1 in whole blood and PRP were measured by an ELISA kit. PRP in five different concentrations (0%, 2.5%, 5%, 10%, and 25%) was applied to culture NCSCs. On the 1^st, 3^rd, 5^th, and 7^th days, cell proliferation was evaluated by CCK8. Cell viability was tested by a live/dead staining kit. mRNA and protein expression of DSPP and BMP4 were analyzed by RT-qPCR and western blot, respectively. Statistical analysis was performed by a one-way analysis of variance (ANOVA) test or t-test.

Results

Dental apical papilla cells formed neural spheres, from which cells displayed positive expression of p75NTR and HNK-1. The concentrations of PDGF-BB and TGF-β1 in PRP were about 3.5-fold higher than those in whole blood. 5% and 10% PRP significantly promoted proliferation of NCSCs, while 25% and 50% PRP inhibited cell proliferation from Day 3 to Day 7. Low-concentration (2.5%, 5%, and 10%) PRP slightly improved viability of NCSCs on Day 7. On the other hand, high-concentration (25% and 50%) PRP significantly inhibited viability of NCSCs from Day 3 to Day 7. RT-qPCR and western blot results indicated that 10% PRP could promote odontogenic differentiation of NCSCs on Day 7. mRNA and protein expression of DSPP and BMP4 were significantly upregulated in the 10% PRP group compared to those in the control group (P < 0.05).

Conclusions

PRP is a simply acquirable blood derivative which contains high concentration of growth factors like PDGF-BB and TGF-β1. PRP in a proper concentration could promote proliferation, viability, and odontogenic differentiation of NCSCs derived from human dental apical papilla.

Effect of Liquid Platelet-rich Fibrin and Platelet-rich Plasma on the Regenerative Potential of Dental Pulp Cells Cultured under Inflammatory Conditions: A Comparative Analysis

INTRODUCTION

Platelet-rich plasma (PRP) has been widely used in regenerative dentistry for over 2 decades. Nevertheless, previous studies have shown that its growth factor content is released over a short time period, and the application of anticoagulants limits its regenerative potential. Therefore, a second-generation platelet concentrate (liquid platelet-rich fibrin [PRF]) was developed without the use of anticoagulants and with shorter centrifugation times. The purpose of the present study was to compare the cellular regenerative activity of human dental pulp cells (hDPCs) when cultured with either liquid PRF or traditional PRP.

METHODS

The regenerative potential of hDPCs isolated from healthy human third molars (18-22 years, n = 5) was investigated in both normal and inflammatorylike conditions (lipopolysaccharide [LPS]) and assessed for their potential for dentin repair. The effects of liquid PRF and PRP were assessed for cellular migration, proliferation, and odontoblastic differentiation using a transwell assay, scratch assay, proliferation assay, alkaline phosphatase assay, alizarin red staining, and real-time polymerase chain reaction for genes encoding collagen type 1 alpha 1, dentin sialophosphoprotein, and dentin matrix protein 1, respectively. The effects of both platelet concentrates were also assessed for their ability to influence nuclear translocation of nuclear factor kappa B (p65) by immunofluorescence, and reverse-transcription polymerase chain reaction for genes encoding interleukin-1β, tumor necrosis factor alpha, and nuclear factor kappa B (p65) during an inflammatory condition.

RESULTS

Both PRP and liquid PRF increased the migration and proliferation of hDPCs when compared with the control group, whereas liquid PRF showed a notable significant increase in migration when compared with PRP. Furthermore, liquid PRF induced significantly greater alkaline phosphatase activity, alizarin red staining, and a messenger RNA expression of genes encoding collagen type 1 alpha 1, dentin sialophosphoprotein, and dentin matrix protein 1 when compared with PRP. When hDPCs were cultured with LPS to stimulate an inflammatory environment, a marked decrease in dentin-related repair was observed. When liquid PRF was cultured within this inflammatory environment, the reduced regenerative potential in this LPS-produced environment was significantly and markedly improved, facilitating hDPC regeneration. The messenger RNA expression of inflammatory markers including tumor necrosis factor alpha, interleukin-1β, and p65 were all significantly decreased in the presence of liquid PRF, and, furthermore, liquid PRF also inhibited the transport of p65 to the nucleus in hDPCs (suggesting a reduced inflammatory condition).

CONCLUSIONS

The findings from the present study suggest that liquid PRF promoted greater regeneration potential of hDPCs when compared with traditional PRP. Furthermore, liquid PRF also attenuated the inflammatory condition created by LPS and maintained a supportive regenerative ability for the stimulation of odontoblastic differentiation and reparative dentin in hDPCs.

Current and future options for dental pulp therapy

Dental pulp is a connective tissue and has functions that include initiative, formative, protective, nutritive, and reparative activities. However, it has relatively low compliance, because it is enclosed in hard tissue. Its low compliance against damage, such as dental caries, results in the frequent removal of dental pulp during endodontic therapy. Loss of dental pulp frequently leads to fragility of the tooth, and eventually, a deterioration in the patient’s quality of life. With the development of biomaterials such as bioceramics and advances in pulp biology such as the identification of dental pulp stem cells, novel ideas for the preservation of dental pulp, the regenerative therapy of dental pulp, and new biomaterials for direct pulp capping have now been proposed. Therapies for dental pulp are classified into three categories; direct pulp capping, vital pulp amputation, and treatment for non-vital teeth. In this review, we discuss current and future treatment options in these therapies.