Proliferation and odontogenic differentiation of human umbilical cord mesenchymal stem cells and human dental pulp cells co-cultured in hydrogel

Research Advances on Hydrogel-Based Materials for Tissue Regeneration and Remineralization in Tooth

Tissue regeneration and remineralization in teeth is a long-term and complex biological process, including the regeneration of pulp and periodontal tissue, and re-mineralization of dentin, cementum and enamel. Suitable materials are needed to provide cell scaffolds, drug carriers or mineralization in this environment. These materials need to regulate the unique odontogenesis process. Hydrogel-based materials are considered good scaffolds for pulp and periodontal tissue repair in the field of tissue engineering due to their inherent biocompatibility and biodegradability, slow release of drugs, simulation of extracellular matrix, and the ability to provide a mineralized template. The excellent properties of hydrogels make them particularly attractive in the research of tissue regeneration and remineralization in teeth. This paper introduces the latest progress of hydrogel-based materials in pulp and periodontal tissue regeneration and hard tissue mineralization and puts forward prospects for their future application. Overall, this review reveals the application of hydrogel-based materials in tissue regeneration and remineralization in teeth.

Advances in Scaffolds Used for Pulp-Dentine Complex Tissue Engineering - A Narrative Review

Pulp necrosis in immature teeth disrupts root development and predisposes roots to fracture as a consequence of their thin walls and open apices. Regenerative endodontics is a developing treatment modality whereby necrotic pulps are replaced with newly formed healthy tissue inside the root canal. Many clinical studies have demonstrated the potential of this strategy to stimulate root maturation and apical root-end closure. However, clinical outcomes are patient-dependent and unpredictable. The development of predictable clinical protocols is achieved through the interplay of the three classical elements of tissue engineering, namely, stem cells, signaling molecules, and scaffolds. Scaffolds provide structural support for cells to adhere and proliferate and also regulate cell differentiation and metabolism. Hence, designing and fabricating an appropriate scaffold is a crucial step in tissue engineering. In this review, four main classes of scaffolds used to engineer pulp-dentine complexes, including bioceramic-based scaffolds, synthetic polymer-based scaffolds, natural polymer-based scaffolds, and composite scaffolds, are covered. Additionally, recent advances in the design, fabrication, and application of such scaffolds are analysed along with their advantages and limitations. Finally, the importance of vascular network establishment in the success of pulp-dentine complex regeneration and strategies used to create scaffolds to address this challenge are discussed.

Influencing factors of pulp-dentin complex regeneration and related biological strategies

Regenerative endodontic therapy (RET) utilizing tissue engineering approach can promote the regeneration of pulp-dentin complex to restore pulp vascularization, neuralization, immune function and tubular dentin, therefore the regenerated pulp-dentin complex will have normal function. Multiple factors may significantly affect the efficacy of RET, including stem cells, biosignaling molecules and biomaterial scaffolds. Stem cells derived from dental tissues (such as dental pulp stem cells) exhibit certain advantages in RET. Combined application of multiple signaling molecules and activation of signal transduction pathways such as Wnt/β-catenin and BMP/Smad play pivotal roles in enhancing the potential of stem cell migration, proliferation, odontoblastic differentiation, and nerve and blood vessel regeneration. Biomaterials suitable for RET include naturally-derived materials and artificially synthetic materials. Artificially synthetic materials should imitate natural tissues for biomimetic modification in order to realize the temporal and spatial regulation of pulp-dentin complex regeneration. The realization of pulp-dentin complex regeneration depends on two strategies: stem cell transplantation and stem cell homing. Stem cell homing strategy does not require the isolation and culture of stem cells in vitro, so is better for clinical application. However, in order to achieve the true regeneration of pulp-dentin complex, problems related to improving the success rate of stem cell homing and promoting their proliferation and differentiation need to be solved. This article reviews the influencing factors of pulp-dentin complex regeneration and related biological strategies, and discusses the future research direction of RET, to provide reference for clinical translation and application of RET.

Efficacy of Photobiomodulation and Vitamin D on Odontogenic Activity of Human Dental Pulp Stem Cells

Introduction: The regeneration of dental pulp tissue using human dental pulp stem cells (HDPSCs) has attracted increasing attention in recent years. Recent studies have suggested that several factors such as photobiomodulation (PBM) and vitamin D affect the proliferation and differentiation of HDPSCs. Therefore, the present study evaluated the effects of PBM and vitamin D on odontogenic differentiation of HDPSCs for dentin -like tissue formation. Methods: HDPSCs were collected, isolated, and characterized and then divided into six groups: group I, control; group II, vitamin D (10^-7 Mol); group III, irradiation at 1 J/cm² of 810 nm diode laser; group IV, irradiation at 1 J/cm² and culture with vitamin D; group V, irradiation at 2 J/cm², and group VI, irradiation at 2 J/cm² and culture with vitamin D, cell viability assay was measured through MTT. Alkaline phosphatase (ALP) enzyme activity and mRNA levels of vascular endothelial growth factor (VEGF), bone morphogenic protein-2 (BMP-2), and dentin sialophosphoprotein (DSPP) were also assessed. Results: PBM at 1 and 2 J/cm² combined with vitamin D significantly promoted HDPSCs proliferation through MTT assay and odontogenic differentiation through gene expression of VEGF, BMP-2, and DSPP levels (P < 0.0001). Conclusion: PBM at 2 J/cm² combined with vitamin D enhanced the HDPSCs proliferation and odontogenic differentiation and thus could be a novel strategy for dentin regeneration in dentistry.

Mesenchymal stem cells: A comprehensive methods for odontoblastic induction

BACKGROUND

In the area of oral and maxillofacial surgery, regenerative endodontics aims to present alternative options to conventional treatment strategies. With continuous advances in regenerative medicine, the source of cells used for pulp tissue regeneration is not only limited to mesenchymal stem cells as the non-mesenchymal stem cells have shown capabilities too. In this review, we are systematically assessing the recent findings on odontoblastic differentiation induction with scaffold and non-scaffold approaches.

METHODS

A comprehensive search was conducted in Pubmed, and Scopus, and relevant studies published between 2015 and 2020 were selected following the PRISMA guideline. The main inclusion criteria were that articles must be revolving on method for osteoblast differentiation in vitro study. Therefore, in vivo and human or animal clinical studies were excluded. The search outcomes identified all articles containing the word "odontoblast", "differentiation", and "mesenchymal stem cell".

RESULTS

The literature search identified 99 related studies, but only 11 articles met the inclusion criteria. These include 5 odontoblastic differentiation induction with scaffold, 6 inductions without scaffolds. The data collected were characterised into two main categories: type of cells undergo odontoblastic differentiation, and odontoblastic differentiation techniques using scaffolds or non-scaffold.

CONCLUSION

Based on the data analysis, the scaffold-based odontoblastic induction method seems to be a better option compared to the non-scaffold method. In addition of that, the combination of growth factors in scaffold-based methods could possibly enhance the differentiation. Thus, further detailed studies are still required to understand the mechanism and the way to enhance odontoblastic differentiation.

Hydrogels for Large-Scale Expansion of Stem Cells

Stem cells demonstrate considerable promise for various preclinical and clinical applications, including drug screening, disease treatments, and regenerative medicine. Producing high-quality and large amounts of stem cells is in demand for these applications. Despite challenges, as hydrogel-based cell culture technology has developed, tremendous progress has been made in stem cell expansion and directed differentiation. Hydrogels are soft materials with abundant water. Many hydrogel properties, including biodegradability, mechanical strength, and porosity, have been shown to play essential roles in regulating stem cell proliferation and differentiation. The biochemical and physical properties of hydrogels can be specifically tailored to mimic the native microenvironment that various stem cells reside in vivo. A few hydrogel-based systems have been developed for successful stem cell cultures and expansion in vitro. In this review, we summarize various types of hydrogels that have been designed to effectively enhance the proliferation of hematopoietic stem cells (HSCs), mesenchymal stem/stromal cells (MSCs), and pluripotent stem cells (PSCs), respectively. According to each stem cell type's preference, we also discuss strategies for fabricating hydrogels with biochemical and mechanical cues and other characteristics representing microenvironments of stem cells in vivo. STATEMENT OF SIGNIFICANCE: In this review article we summarize current progress on the construction of hydrogel systems for the culture and expansion of various stem cells, including hematopoietic stem cells (HSCs), mesenchymal stem/stromal cells (MSCs), and pluripotent stem cells (PSCs). The Significance includes: (1) Provide detailed discussion on the stem cell niches that should be considered for stem cell in vitro expansion. (2) Summarize various strategies to construct hydrogels that can largely recapture the microenvironment of native stem cells. (3) Suggest a few future directions that can be implemented to improve current in vitro stem cell expansion systems.

Evaluating the potential of an amelogenin-derived peptide in tertiary dentin formation

Several novel biomaterials have been developed for dental pulp capping by inducing tertiary dentin formation. The aim of this study was to evaluate the effect of QP5, an amelogenin-based peptide, on the mineralization of dental pulp cells (DPCs) in vitro and in vivo. The cell viability of human DPCs (hDPCs) after treatment with QP5 was determined using the Cell Counting Kit-8 (CCK-8). Migration of hDPCs was assessed using scratch assays, and the pro-mineralization effect was determined using alkaline phosphatase (ALP) staining, alizarin red staining and the expression of mineralization-related genes and proteins. The results showed that QP5 had little effect on the cell viability, and significantly enhanced the migration capability of hDPCs. QP5 promoted the formation of mineralized nodules, and upregulated the activity of ALP, the expression of mRNA and proteins of mineralization-related genes. A pulp capping model in rats was generated to investigate the biological effect of QP5. The results of micro-computed tomography and haematoxylin and eosin staining indicated that the formation of tertiary dentin in QP5-capping groups was more prominent than that in the negative control group. These results indicated the potential of QP5 as a pulp therapy agent.

Hydrogels and Dentin-Pulp Complex Regeneration: From the Benchtop to Clinical Translation

Dentin-pulp complex is a term which refers to the dental pulp (DP) surrounded by dentin along its peripheries. Dentin and dental pulp are highly specialized tissues, which can be affected by various insults, primarily by dental caries. Regeneration of the dentin-pulp complex is of paramount importance to regain tooth vitality. The regenerative endodontic procedure (REP) is a relatively current approach, which aims to regenerate the dentin-pulp complex through stimulating the differentiation of resident or transplanted stem/progenitor cells. Hydrogel-based scaffolds are a unique category of three dimensional polymeric networks with high water content. They are hydrophilic, biocompatible, with tunable degradation patterns and mechanical properties, in addition to the ability to be loaded with various bioactive molecules. Furthermore, hydrogels have a considerable degree of flexibility and elasticity, mimicking the cell extracellular matrix (ECM), particularly that of the DP. The current review presents how for dentin-pulp complex regeneration, the application of injectable hydrogels combined with stem/progenitor cells could represent a promising approach. According to the source of the polymeric chain forming the hydrogel, they can be classified into natural, synthetic or hybrid hydrogels, combining natural and synthetic ones. Natural polymers are bioactive, highly biocompatible, and biodegradable by naturally occurring enzymes or via hydrolysis. On the other hand, synthetic polymers offer tunable mechanical properties, thermostability and durability as compared to natural hydrogels. Hybrid hydrogels combine the benefits of synthetic and natural polymers. Hydrogels can be biofunctionalized with cell-binding sequences as arginine-glycine-aspartic acid (RGD), can be used for local delivery of bioactive molecules and cellularized with stem cells for dentin-pulp regeneration. Formulating a hydrogel scaffold material fulfilling the required criteria in regenerative endodontics is still an area of active research, which shows promising potential for replacing conventional endodontic treatments in the near future.