Odontogenic Differentiation of Human Dental Pulp Stem Cells on Hydrogel Scaffolds Derived from Decellularized Bone Extracellular Matrix and Collagen Type I. PLoS One. 2016;11:e0148225. [PMID: 26882351 PMCID: PMC4755593 DOI: 10.1371/journal.pone.0148225]

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.

Photo-crosslinkable hydrogel incorporated with bone matrix particles for advancements in dentin tissue engineering

The objective of this study was to create injectable photo-crosslinkable biomaterials, using gelatin methacryloyl (GelMA) hydrogel, combined with a decellularized bone matrix (BMdc) and a deproteinized (BMdp) bovine bone matrix. These were intended to serve as bioactive scaffolds for dentin regeneration. The parameters for GelMA hydrogel fabrication were initially selected, followed by the incorporation of BMdc and BMdp at a 1% (w/v) ratio. Nano-hydroxyapatite (nHA) was also included as a control. A physicochemical characterization was conducted, with FTIR analysis indicating that the mineral phase was complexed with GelMA, and BMdc was chemically bonded to the amide groups of gelatin. The porous structure was preserved post-BMdc incorporation, with bone particles incorporated alongside the pores. Conversely, the mineral phase was situated inside the pore opening, affecting the degree of porosity. The mineral phase did not modify the degradability of GelMA, even under conditions of type I collagenase-mediated enzymatic challenge, allowing hydrogel injection and increased mechanical strength. Subsequently, human dental pulp cells (HDPCs) were seeded onto the hydrogels. The cells remained viable and proliferative, irrespective of the GelMA composition. All mineral phases resulted in a significant increase in alkaline phosphatase activity and mineralized matrix deposition. However, GelMA-BMdc exhibited higher cell expression values, significantly surpassing those of all other formulations. In conclusion, our results showed that GelMA-BMdc produced a porous and stable hydrogel, capable of enhancing odontoblastic differentiation and mineral deposition when in contact with HDPCs, thereby showing potential for dentin regeneration.

Induction of osteogenic differentiation by the extracellular matrix of fetal bone tissues and adult cartilage

Decellularized cortical bone powder derived from adult animals has been shown to induce bone remodeling. Furthermore, it is increasingly evident that the extracellular matrix (ECM) within decellularized tissues differs depending on the source tissue and the age of the animal, leading to distinct effects on cells. In this study, we prepared powders from decellularized fetal and adult porcine bone tissues and conducted biological analyses to determine if the decellularized tissue could induce adipose-derived stem cell differentiation. Decellularized fetal tissues and adult cortical bone were converted into powder by cryomilling, but decellularized adult bone marrow and cartilage were not powdered through this process. In vitro assessments revealed that decellularized fetal tissues, decellularized adult cartilage extract, and decellularized fetal cartilage powder can induce osteoblast differentiation. This study suggests that decellularized fetal bone tissues and adult cartilage contain ECM components that can induce osteoblast differentiation. Additionally, it highlights the utility of decellularized fetal cartilage powder for bone reconstruction.

Evaluation of dental pulp stem cells response to flowable nano-hybrid dental composites: A comparative analysis

BACKGROUND

Flowable resin composites (FRC) are tooth-colored restorative materials that contain a lower filler particle content, and lower viscosity than their bulk counterparts, making them useful for specific clinical applications. Yet, their chemical makeup may impact the cellular population of the tooth pulp. This in-vitro study assessed the cytocompatibility and odontogenic differentiation capacity of dental pulp stem cells (DPSCs) in response to two recent FRC material extracts.

METHODS

Extracts of the FRC Aura easyflow (AEF) and Polofil NHT Flow (PNF) were applied to DPSCs isolated from extracted human teeth. Cell viability of DPSCs was assessed using MTT assay on days 1, 3 and 7. Cell migration was assessed using the wound healing assay. DPSCs' capacity for osteo/odontogenic differentiation was assessed by measuring the degree of mineralization by Alizarin Red S staining, alkaline phosphatase enzyme (ALP) activity, and monitoring the expression of osteoprotegerin (OPG), RUNX Family Transcription Factor 2 (RUNX2), and the odontogenic marker dentin sialophosphoprotein (DSPP) by RT-PCR. Monomer release from the FRC was also assessed by High-performance liquid chromatography analysis (HPLC).

RESULTS

DPSCs exposed to PNF extracts showed significantly higher cell viability, faster wound closure, and superior odontogenic differentiation. This was apparent through Alizarin Red staining of calcified nodules, elevated alkaline phosphatase activity, and increased expression of osteo/odontogenic markers. Moreover, HPLC analysis revealed a higher release of TEDGMA, UDMA, and BISGMA from AEF.

CONCLUSIONS

PNF showed better cytocompatibility and enhancement of odontogenic differentiation than AEF.

Decellularization and Their Significance for Tissue Regeneration in the Era of 3D Bioprinting

Three-dimensional bioprinting is an emerging technology that has high potential application in tissue engineering and regenerative medicine. Increasing advancement and improvement in the decellularization process have led to an increase in the demand for using a decellularized extracellular matrix (dECM) to fabricate tissue engineered products. Decellularization is the process of retaining the extracellular matrix (ECM) while the cellular components are completely removed to harvest the ECM for the regeneration of various tissues and across different sources. Post decellularization of tissues and organs, they act as natural biomaterials to provide the biochemical and structural support to establish cell communication. Selection of an effective method for decellularization is crucial, and various factors like tissue density, geometric organization, and ECM composition affect the regenerative potential which has an impact on the end product. The dECM is a versatile material which is added as an important ingredient to formulate the bioink component for constructing tissue and organs for various significant studies. Bioink consisting of dECM from various sources is used to generate tissue-specific bioink that is unique and to mimic different biometric microenvironments. At present, there are many different techniques applied for decellularization, and the process is not standardized and regulated due to broad application. This review aims to provide an overview of different decellularization procedures, and we also emphasize the different dECM-derived bioinks present in the current global market and the major clinical outcomes. We have also highlighted an overview of benefits and limitations of different decellularization methods and various characteristic validations of decellularization and dECM-derived bioinks.

Biocompatibility of ABS and PLA Polymers with Dental Pulp Stem Cells Enhance Their Potential Biomedical Applications

Polylactic Acid (PLA) and Acrylonitrile-Butadiene-Styrene (ABS) are commonly used polymers in 3D printing for biomedical applications. Dental Pulp Stem Cells (DPSCs) are an accessible and proliferative source of stem cells with significant differentiation potential. Limited knowledge exists regarding the biocompatibility and genetic safety of ABS and PLA when in contact with DPSCs. This study aimed to investigate the impact of PLA and ABS on the adhesion, proliferation, osteogenic differentiation, genetic stability, proteomics, and immunophenotypic profile of DPSCs. A total of three groups, 1- DPSC-control, 2- DPSC+ABS, and 3- DPSC+PLA, were used in in vitro experiments to evaluate cell morphology, proliferation, differentiation capabilities, genetic stability, proteomics (secretome), and immunophenotypic profiles regarding the interaction between DPSCs and polymers. Both ABS and PLA supported the adhesion and proliferation of DPSCs without exhibiting significant cytotoxic effects and maintaining the capacity for osteogenic differentiation. Genetic stability, proteomics, and immunophenotypic profiles were unaltered in DPSCs post-contact with these polymers, highlighting their biosafety. Our findings suggest that ABS and PLA are biocompatible with DPSCs and demonstrate potential in dental or orthopedic applications; the choice of the polymer will depend on the properties required in treatment. These promising results stimulate further studies to explore the potential therapeutic applications in vivo using prototyped polymers in personalized medicine.

The Role of Extracellular Matrix (ECM) Adhesion Motifs in Functionalised Hydrogels

To create functional tissue engineering scaffolds, biomaterials should mimic the native extracellular matrix of the tissue to be regenerated. Simultaneously, the survival and functionality of stem cells should also be enhanced to promote tissue organisation and repair. Hydrogels, but in particular, peptide hydrogels, are an emerging class of biocompatible scaffolds which act as promising self-assembling biomaterials for tissue engineering and regenerative therapies, ranging from articular cartilage regeneration at joint defects, to regenerative spinal cord injury following trauma. To enhance hydrogel biocompatibility, it has become imperative to consider the native microenvironment of the site for regeneration, where the use of functionalised hydrogels with extracellular matrix adhesion motifs has become a novel, emerging theme. In this review, we will introduce hydrogels in the context of tissue engineering, provide insight into the complexity of the extracellular matrix, investigate specific adhesion motifs that have been used to generate functionalised hydrogels and outline their potential applications in a regenerative medicine setting. It is anticipated that by conducting this review, we will provide greater insight into functionalised hydrogels, which may help translate their use towards therapeutic roles.

Bioactive composite hydrogels as 3D mesenchymal stem cell encapsulation environment for bone tissue engineering: in vitro and in vivo studies

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

Creating a Microenvironment to Give Wings to Dental Pulp Regeneration-Bioactive Scaffolds

Dental pulp and periapical diseases make patients suffer from acute pain and economic loss. Although root canal therapies, as demonstrated through evidence-based medicine, can relieve symptoms and are commonly employed by dentists, it is still difficult to fully restore a dental pulp's nutrition, sensory, and immune-regulation functions. In recent years, researchers have made significant progress in tissue engineering to regenerate dental pulp in a desired microenvironment. With breakthroughs in regenerative medicine and material science, bioactive scaffolds play a pivotal role in creating a suitable microenvironment for cell survival, proliferation, and differentiation, following dental restoration and regeneration. This article focuses on current challenges and novel perspectives about bioactive scaffolds in creating a microenvironment to promote dental pulp regeneration. We hope our readers will gain a deeper understanding and new inspiration of dental pulp regeneration through our summary.

The potential of eggshell hydroxyapatite, collagen, and EGCG (HAp-Col-EGCG) scaffold as a pulp regeneration material

Background

Hydrogel scaffold is a biomaterial that can facilitate cells in forming a tissue structure. It can promote cell adhesion, migration, and proliferation. Further research to find a new scaffold from natural resources is challenging, so this study aimed to characterize a hydrogel composite scaffold, which has the potential to be used as a regenerative material.

Methods

The formulation of HAp-Col-EGCG was mixed with different ratios of 1%, 2%, and 4% hydroxyapatite. We analyzed its injectability, pH, and gelation time. Scanning electron microscopy (SEM), energy X-ray Spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR) were used to evaluate the surface morphologies, element composition, and chemical properties of HAp-Col-EGCG.

Results

The results showed that the injectability test was almost 90 % in all groups. There was no significant difference in the median value of the pH at 0, 20, and 60 min in all groups, but there was a significant difference at 40 min. The average gelation times in all groups were not significant. SEM-EDX showed a microporous scaffold, with the HAp particles well distributed in the collagen pores at a ratio of 1.9, 2.29, and 1.89 Ca/P. The FTIR results showed intermolecular bonds in the HAp-Col-EGCG scaffold. The X-ray diffraction analysis showed that collagen and EGCG did not affect the crystal structure and size of HAp. Cytotoxicity test showed more dental pulp cell viability at the 4 % HAp concentration at 514.35 ± 15.45.

Conclusion

This study indicates that hydrogel scaffold from eggshell hydroxyapatite, collagen, and EGCG has a high potential for pulp regenerative therapy.

Effect of PCL/nHAEA nanocomposite to osteo/odontogenic differentiation of dental pulp stem cells

Purpose

The green synthesis of nanoparticles has recently opened up a new route in material production. The aim of this study was to evaluate the effect of nanohydroxyapatite (nHA) synthesized from Elaeagnus angustifolia (EA) extract in polycaprolactone (PCL) nanofibers (PCL/nHAEA) to odontogenic differentiation of dental pulp stem cells (DPSCs) and their potential applications for dentin tissue engineering.

Methods

Green synthesis of nHA via EA extract (nHAEA) was done by the sol–gel technique. Then electrospun nanocomposites containing of PCL blended with nHA (P/nHA) and nHAEA (P/nHAEA) were fabricated, and the characterization was evaluated via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and the contact angle. The morphology of nanofibers and the cell adhesion capacity of DPSCs on nanofibers were evaluated using SEM. Cytocompatibility was assessed by MTT. Osteo/odontogenic differentiation ability of the nanocomposites were assessed using alkaline phosphatase (ALP) activity, alizarin red S (ARS) staining, and quantitative real-time polymerase chain reaction (qPCR) technique.

Results

Viability and adhesion capacity of DPSCs were higher on P/nHAEA nanofibers than PCL and P/nHA nanofibers. ARS assay, ALP activity, and qPCR analysis findings confirmed that the nHAEA blended nanofibrous scaffolds substantially increased osteo/odontogenic differentiation of DPSCs.

Conclusion

PCL/nHAEA nanocomposites had a noticeable effect on the odontogenic differentiation of DPSCs and may help to improve cell-based dentin regeneration therapies in the future.

Osteoporosis treatment by mesenchymal stromal/stem cells and their exosomes: Emphasis on signaling pathways and mechanisms

Osteoporosis is the loss of bone density, which is one of the main problems in developed and developing countries and is more common in the elderly. Because this disease is often not diagnosed until a bone fracture, it can become a life-threatening disease and cause hospitalization. With the increase of older people in a population, this disease's personal and social costs increase year by year and affect different communities. Most current treatments focus on pain relief and usually do not lead to bone tissue recovery and regeneration. But today, the use of stem cell therapy is recommended to treat and improve this disease recovery, which helps restore bone tissue by improving the imbalance in the osteoblast-osteoclast axis. Due to mesenchymal stromal/stem cells (MSCs) characteristics and their exosomes, these cells and vesicles are excellent sources for treating and preventing the progression and improvement of osteoporosis. Due to the ability of MSCs to differentiate into different cells and migrate to the site of injury, these cells are used in tissue regenerative medicine. Also, due to their contents, the exosomes of these cells help regenerate and treat various tissue injuries by affecting the injury site's cells. In this article, we attempted to review new studies in which MSCs and their exosomes were used to treat osteoporosis.

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.

Research progress of natural tissue-derived hydrogels for tissue repair and reconstruction

There are many different grafts to repair damaged tissue. Various types of biological scaffolds, including films, fibers, microspheres, and hydrogels, can be used for tissue repair. A hydrogel, which is composed a natural or synthetic polymer network with high water absorption capacity, can provide a microenvironment closely resembling the extracellular matrix (ECM) of natural tissues to stimulate cell adhesion, proliferation, and differentiation. It has been shown to have great application potential in the field of tissue repair and regeneration. Hydrogels derived from natural tissues retain a variety of proteins and growth factors in optimal proportions, which is beneficial for the regeneration of specific tissues. This article reviews the latest research advances in the field of hydrogels from a variety of natural tissue sources, including bone tissue, blood vessels, nerve tissue, adipose tissue, skin tissue, and muscle tissue, including preparation methods, advantages, and applications in tissue engineering and regenerative medicine. Finally, it summarizes and discusses the challenges faced by natural tissue-derived hydrogels used in tissue repair, as well as future research and application directions.

The Progress of Decellularized Scaffold in Stomatology

The oral and maxillofacial region contains oral organs and facial soft tissues. Due to the complexity of the structures and functions of this region, the repair of related defects is complicated. Different degrees of defects require different repair methods, which involve a great combination of medicine and art, and the material requirements are extremely high. Hence, clinicians are plagued by contemporary oral repair materials due to the limitations of bone harvesting, immune rejection, low osteogenic activity and other problems. Decellularized extracellular matrix has attracted much attention as a bioactive scaffold material because of its nonimmunogenic properties, good osteogenic properties, slow release of growth factors, promotion of seed cell adhesion and maintenance of stem cell characteristics. This article reviews the sources, preparation methods, application and research progress of extracellular matrix materials in the repair of oral and maxillofacial defects to provide an overview for fundamental research and clinical development.

Fabrication of bone‐derived decellularized extracellular matrix/ceramic‐based biocomposites and their osteo/odontogenic differentiation ability for dentin regeneration

The goal of this study was to fabricate bioactive cell‐laden biocomposites supplemented with bone‐derived decellularized extracellular matrix (dECM) with calcium phosphate ceramic, and to assess the effect of the biocomponents on the osteogenic and odontogenic differentiation of human dental pulp stem cells (hDPSCs). By evaluating the rheological properties and selecting printing parameters, mechanically stable cell‐laden 3D biocomposites with high initial cell‐viability (>90%) and reasonable printability (≈0.9) were manufactured. The cytotoxicity of the biocomposites was evaluated via MTT assay and nuclei/F‐actin fluorescent analyses, while the osteo/odontogenic differentiation of the hDPSCs was assessed using histological and immunofluorescent analyses and various gene expressions. Alkaline phosphate activity and alizarin red staining results indicate that the dECM‐based biocomposites exhibit significantly higher osteogenic activities, including calcification, compared to the collagen‐based biocomposites. Furthermore, immunofluorescence images and gene expressions demonstrated upregulation of dentin matrix acidic phosphoprotein‐1 and dentin sialophosphoprotein in the dECM‐based biocomposites, indicating acceleration of the odontogenic differentiation of hDPSCs in the printed biocomposites. The hDPSC‐laden biocomposite was implanted into the subcutaneous region of mice, and the biocomposite afforded clear induction of osteo/odontogenic ectopic hard tissue formation 8 weeks post‐transplantation. From these results, we suggest that the hDPSC‐laden biocomposite is a promising biomaterial for dental tissue engineering.

Decellularized extracellular matrix scaffolds: Recent trends and emerging strategies in tissue engineering

The application of scaffolding materials is believed to hold enormous potential for tissue regeneration. Despite the widespread application and rapid advance of several tissue-engineered scaffolds such as natural and synthetic polymer-based scaffolds, they have limited repair capacity due to the difficulties in overcoming the immunogenicity, simulating in-vivo microenvironment, and performing mechanical or biochemical properties similar to native organs/tissues. Fortunately, the emergence of decellularized extracellular matrix (dECM) scaffolds provides an attractive way to overcome these hurdles, which mimic an optimal non-immune environment with native three-dimensional structures and various bioactive components. The consequent cell-seeded construct based on dECM scaffolds, especially stem cell-recellularized construct, is considered an ideal choice for regenerating functional organs/tissues. Herein, we review recent developments in dECM scaffolds and put forward perspectives accordingly, with particular focus on the concept and fabrication of decellularized scaffolds, as well as the application of decellularized scaffolds and their combinations with stem cells (recellularized scaffolds) in tissue engineering, including skin, bone, nerve, heart, along with lung, liver and kidney.

Potential role of dental pulp stem cells conditioned medium for odontoblastic differentiation

Background

Functional bioengineered tooth regeneration using autologous or allogeneic alternative differentiated cells sources are thought to have a great potential in replacing conventional dentures. This study investigated the potential of dental pulp stem cells (DPSCs) conditioned medium for odontoblastic differentiation of Wharton’s jelly mesenchymal stem cells (WJMSCs). The DPSCs derived from healthy adult permanent first molars were cultured at high confluence prior to conditioned medium collection. The WJMSCs were cultured in six different treatments, with varying ratios of culture media to DPSCs-conditioned medium. MTT assay was used to measure the rate of proliferation of WJMSCs, while immunocytochemistry staining was utilised to detect the expression of dental matrix protein 1 (DMP-1). The deposited calcium was detected and analysed via Alizarin-Red Staining (ARS).

Results

It was found that the proliferation of WJMSCs cultured under the mixture of complete medium and DPSCs conditioned medium showed significantly lower than the control; presumably the cells started to exit proliferative state prior differentiation. In 14 days of induction, the cells in all treatments showed osteoblastic-like morphology, calcium compound deposits were observed at day 7, 10 and 14 of differentiation suggested that DPSCs conditioned medium could lead to osteoblastic/odontoblastic differentiation. However, the DMP-1 protein can be seen only expressed minimally at day 14 of conditioned medium induction.

Conclusions

In conclusion, DPSCs conditioned medium appeared as a potential odontoblastic induction approach for WJMSCs. To further investigate the stimulatory effects by DPSCs conditioned medium, specific signalling pathway need to be elucidated to enhance the differentiation efficiency.

Decellularized Dental Pulp, Extracellular Vesicles, and 5-Azacytidine: A New Tool for Endodontic Regeneration

Dental pulp is a major component of the dental body that serves to maintain the tooth life and function. The aim of the present work was to develop a system that functions as a growth-permissive microenvironment for dental pulp regeneration using a decellularized dental pulp (DDP) matrix, 5-Aza-2′-deoxycytidine (5-Aza), and Extracellular Vesicles (EVs) derived from human Dental Pulp Stem Cells (hDPSCs). Human dental pulps extracted from healthy teeth, scheduled to be removed for orthodontic purpose, were decellularized and then recellularized with hDPSCs. The hDPSCs were seeded on DDP and maintained under different culture conditions: basal medium (CTRL), EVs, 5-Aza, and EVs+-5-Aza. Immunofluorescence staining and Western blot analyses were performed to evaluate the proteins’ expression related to dentinogenesis, such as ALP, RUNX2, COL1A1, Vinculin, DMP1, and DSPP. Protein contents found in the DDP recellularized with hDPSCs were highly expressed in samples co-treated with EVs and 5-Aza compared to other culture conditions. This study developed a DDP matrix loaded by hDPSCs in co-treatment with EVs, which might enhance the dentinogenic differentiation with a high potentiality for endodontic regeneration.

Complement C5aR/LPS-induced BDNF and NGF modulation in human dental pulp stem cells

Stem cells with the ability to differentiate into a variety of cells and secrete nerve regeneration factors have become an emerging option in nerve regeneration. Dental pulp stem cells (DPSCs) appear to be a good candidate for nerve regeneration given their accessibility, neural crest origin, and neural repair qualities. We have recently demonstrated that the complement C5a system, which is an important mediator of inflammation and tissue regeneration, is activated by lipoteichoic acid-treated pulp fibroblasts, and governs the production of brain-derived nerve growth factor (BDNF). This BDNF secretion promotes neurite outgrowth towards the injury site. Here, we extend our observation to DPSCs and compare their neurogenic ability to bone marrow-derived mesenchymal stem cells (BM-MSCs) under inflammatory stimulation. Our ELISA and immunostaining data demonstrate that blocking the C5a receptor (C5aR) reduced BDNF production in DPSCs, while treatment with C5aR agonist increased the BDNF expression, which suggests that C5aR has a positive regulatory role in the BDNF modulation of DPSCs. Inflammation induced by lipopolysaccharide (LPS) treatment potentiated this effect and is C5aR dependent. Most important, DPSCs produced significantly higher levels of C5aR-mediated BDNF compared to BM-MSCs. Taken together, our data reveal novel roles for C5aR and inflammation in modulation of BDNF and NGF in DPSCs.

Future of Decellularized Dental Pulp Matrix in Regenerative Endodontics

With the advancements in tissue engineering, the repair and regeneration of oral/dental tissue are becoming possible and productive. Due to periodontal diseases, the tooth loses bone support resulting in tooth loss, but bone grafting stabilizes with new bone. It is seen that due to the progression of dental caries, pulp damage happens, and the vitality of the tooth is compromised. The current theme of dental pulp regeneration through biological and synthetic scaffolds, is becoming a potential therapy for pulp revitalization.

Effect of two different concentrations of 1α,25-dihydroxyvitamin D3 on odontogenic differentiation of stem cells from human exfoliated deciduous teeth

Background:

Stem cells from human exfoliated deciduous teeth (SHEDs) can transform into odontoblasts in vitro and in vivo. The role of 1α, 25-dihydroxyvitamin D3 (1α,25 vitD3) has been reported in the mineralization of hard tissues and teeth, as well as osteoblastic differentiation. This study aimed to assess the effect of different concentrations of 1α,25 vitD3 on odontogenic differentiation of SHEDs.

Materials and Methods:

In this experimental study, second-passage SHEDs were exposed to odontogenic medium along with 0, 10, 50, 100, and 150 nmol concentrations of in 1α, 25 vitD3 to determine its optimal concentration for odontogenic differentiation. The methyl thiazolyl tetrazolium (MTT) assay was performed. Odontogenic differentiation was evaluated by QRT- polymerase chain reaction for dentin matrix protein (DMP1) and dentin sialophosphoprotein (DSPP) genes. Morphology of differentiated cells was studied by Scanning Electron Microscopy. Data were analyzed using the Kruskal–Wallis, Mann–Whitney, Friedman, and Chi-square test. P < 0.05 is considered statistically significant.

Results:

MTT test result showed the two groups of odontogenic medium + 10 nm 1α,25 vitD3 and odontogenic medium + 150 nm 1α,25 vitD3 provided the most suitable conditions for cell viability at 72 h. Expression of both genes significantly increased in the presence of 1α,25 vitD3 (P < 0.001). Expression of both genes was significantly higher at 14 days compared with 7 days (P < 0.01). At both time points, expression of both genes was significantly higher in the presence of 150 nm 1α,25 vitD3 compared with 10 nm (P < 0.01). The accumulation of cells with odontoblastic morphology, cell interactions, and calcifications were evident.

Conclusion:

1α,25 vitD3 upregulates DMP1 and DSPP and results in odontogenic differentiation of SHEDs in odontogenic medium. This upregulation increases with time and by an increase in concentration of 1α,25 vitD3.

Application of dental pulp stem cells in oral maxillofacial tissue engineering

In the maxillofacial area, soft and hard tissue abnormalities are caused by trauma, tumors, infection, and other causes that expose the maxillofacial region to the surface of the human body. Patients' normal physiological function and appearance are interfered with, and their mental health is adversely impacted, reducing their overall life quality. The pursuit of appropriate medical treatments to correct these abnormalities is thus vital. Autologous stem cell regeneration technology mainly focused on tissues has lately emerged as a significant problem in the medical community. Because of the capacity of dental pulp stem cells (DPSCs) to self-renew, the use of DPSCs from the human pulp tissues of deciduous teeth or permanent teeth has gained popularity among scientists as a stem cell-based therapy option. Aside from that, they are simple to extract and have minimal immunogenicity. As a result, bone tissue engineering may be a critical component in treating maxillofacial and periodontal bone abnormalities. DPSCs activity in maxillofacial and periodontal tissue-engineered bone tissue was investigated in this research.

Photobiomodulation of inflamed dental pulp stem cells under different nutritional conditions

Aim: The present study aimed to investigate photobiomodulation's (PBM) effect on inflamed dental pulp stem cells (IDPSCs) under different nutritional conditions. Methods: Cell proliferation and odontogenic differentiation were evaluated using the MTT assay and real-time quantitative reverse transcription PCR, respectively after laser PBM of cells in 5 or 10% fetal bovine serum (FBS) culture conditions. Results: A significant positive effect of laser irradiation on cell proliferation under both nutritional conditions after 24 and 48 h was observed. DMP-1 gene expression increased in the groups with laser irradiation and 5% FBS. Comparison of gene expression levels in the four groups revealed no statistically significant stimulatory effect. The highest gene expression was observed in the non-laser group with 5% FBS. Conclusion: Further studies are required to obtain an irradiation setup to ideally improve inflamed dental pulp stem cells' proliferation and differentiation.

Polymeric Scaffolds for Dental, Oral, and Craniofacial Regenerative Medicine

Dental, oral, and craniofacial (DOC) regenerative medicine aims to repair or regenerate DOC tissues including teeth, dental pulp, periodontal tissues, salivary gland, temporomandibular joint (TMJ), hard (bone, cartilage), and soft (muscle, nerve, skin) tissues of the craniofacial complex. Polymeric materials have a broad range of applications in biomedical engineering and regenerative medicine functioning as tissue engineering scaffolds, carriers for cell-based therapies, and biomedical devices for delivery of drugs and biologics. The focus of this review is to discuss the properties and clinical indications of polymeric scaffold materials and extracellular matrix technologies for DOC regenerative medicine. More specifically, this review outlines the key properties, advantages and drawbacks of natural polymers including alginate, cellulose, chitosan, silk, collagen, gelatin, fibrin, laminin, decellularized extracellular matrix, and hyaluronic acid, as well as synthetic polymers including polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), poly (ethylene glycol) (PEG), and Zwitterionic polymers. This review highlights key clinical applications of polymeric scaffolding materials to repair and/or regenerate various DOC tissues. Particularly, polymeric materials used in clinical procedures are discussed including alveolar ridge preservation, vertical and horizontal ridge augmentation, maxillary sinus augmentation, TMJ reconstruction, periodontal regeneration, periodontal/peri-implant plastic surgery, regenerative endodontics. In addition, polymeric scaffolds application in whole tooth and salivary gland regeneration are discussed.

An in-vitro study investigating the effect of air-abrasion bioactive glasses on dental adhesion, cytotoxicity and odontogenic gene expression

OBJECTIVE

To assess the microtensile bond strength (MTBS) and interfacial characteristics of universal adhesives applied on dentine air-abraded using different powders. The analysis includes the cytotoxicity of the powders and their effect on odontogenic gene expression.

METHODS

Sound human dentine specimens were air-abraded using bioglass 45S5 (BAG), polycarboxylated zinc-doped bioglass (SEL), alumina (AL) and submitted to SEM analysis. Resin composite was bonded to air-abraded or smear layer-covered dentine (SML) using an experimental (EXP) or a commercial adhesive (ABU) in etch&rinse (ER) or self-etch (SE) modes. Specimens were stored in artificial saliva (AS) and subjected to MTBS testing after 24 h and 10 months. Interfacial nanoleakage assessment was accomplished using confocal microscopy. The cytotoxicity of the powders was assessed, also the total RNA was extracted and the expression of odontogenic genes was evaluated through RT-PCR.

RESULTS

After prolonged AS storage, specimens in the control (SML) and AL groups showed a significant drop in MTBS (p > 0.05), with degradation evident within the bonding interface. Specimens in BAG or SEL air-abraded dentine groups showed no significant difference, with resin-dentine interfaces devoid of important degradation. The metabolic activity of pulp stem cells was not affected by the tested powders. SEL and BAG had no effect on the expression of odontoblast differentiation markers. However, AL particles interfered with the expression of the odontogenic markers.

SIGNIFICANCE

The use of bioactive glass air-abrasion may prevent severe degradation at the resin-dentine interface. Unlike alumina, bioactive glasses do not interfere with the normal metabolic activity of pulp stem cells and their differentiation to odontoblasts.

Engineering hydrogels for personalized disease modeling and regenerative medicine

Technological innovations and advances in scientific understanding have created an environment where data can be collected, analyzed, and interpreted at scale, ushering in the era of personalized medicine. The ability to isolate cells from individual patients offers tremendous promise if those cells can be used to generate functional tissue replacements or used in disease modeling to determine optimal treatment strategies. Here, we review recent progress in the use of hydrogels to create artificial cellular microenvironments for personalized tissue engineering and regenerative medicine applications, as well as to develop personalized disease models. We highlight engineering strategies to control stem cell fate through hydrogel design, and the use of hydrogels in combination with organoids, advanced imaging methods, and novel bioprinting techniques to generate functional tissues. We also discuss the use of hydrogels to study molecular mechanisms underlying diseases and to create personalized in vitro disease models to complement existing pre-clinical models. Continued progress in the development of engineered hydrogels, in combination with other emerging technologies, will be essential to realize the immense potential of personalized medicine. STATEMENT OF SIGNIFICANCE: In this review, we cover recent advances in hydrogel engineering strategies with applications in personalized medicine. Specifically, we focus on material systems to expand or control differentiation of patient-derived stem cells, and hydrogels to reprogram somatic cells to pluripotent states. We then review applications of hydrogels in developing personalized engineered tissues. We also highlight the use of hydrogel systems as personalized disease models, focusing on specific examples in fibrosis and cancer, and more broadly on drug screening strategies using patient-derived cells and hydrogels. We believe this review will be a valuable contribution to the Special Issue and the readership of Acta Biomaterialia will appreciate the comprehensive overview of the utility of hydrogels in the developing field of personalized medicine.

Recent advancements in decellularized matrix technology for bone tissue engineering

The native extracellular matrix (ECM) provides a matrix to hold tissue/organ, defines the cellular fate and function, and retains growth factors. Such a matrix is considered as a most biomimetic scaffold for tissue engineering due to the biochemical and biological components, 3D hierarchical structure, and physicomechanical properties. Several attempts have been performed to decellularize allo- or xeno-graft tissues and used them for bone repairing and regeneration. Decellularized ECM (dECM) technology has been developed to create an in vivo-like microenvironment to promote cell adhesion, growth, and differentiation for tissue repair and regeneration. Decellularization is mediated through physical, chemical, and enzymatic methods. In this review, we describe the recent progress in bone decellularization and their applications as a scaffold, hydrogel, bioink, or particles in bone tissue engineering. Furthermore, we address the native dECM limitations and the potential of non-bone dECM, cell-based ECM, and engineered ECM (eECM) for in vitro osteogenic differentiation and in vivo bone regeneration.

Accounting for Material Changes in Decellularized Tissue with Underutilized Methodologies

Tissue decellularization has rapidly developed to be a practical approach in tissue engineering research; biological tissue is cleared of cells resulting in a protein-rich husk as a natural scaffold for growing transplanted cells as a donor organ therapy. Minimally processed, acellular extracellular matrix reproduces natural interactions with cells in vitro and for tissue engineering applications in animal models. There are many decellularization techniques that achieve preservation of molecular profile (proteins and sugars), microstructure features such as organization of ECM layers (interstitial matrix and basement membrane) and organ level macrofeatures (vasculature and tissue compartments). While structural and molecular cues receive attention, mechanical and material properties of decellularized tissues are not often discussed. The effects of decellularization on an organ depend on the tissue properties, clearing mechanism, chemical interactions, solubility, temperature, and treatment duration. Physical characterization by a few labs including work from the authors provides evidence that decellularization protocols should be tailored to specific research questions. Physical characterization beyond histology and immunohistochemistry of the decellularized matrix (dECM) extends evaluation of retained functional features of the original tissue. We direct our attention to current technologies that can be employed for structure function analysis of dECM using underutilized tools such as atomic force microscopy (AFM), cryogenic electron microscopy (cryo-EM), dynamic mechanical analysis (DMA), Fourier-transform infrared spectroscopy (FTIR), mass spectrometry, and rheometry. Structural imaging and mechanical functional testing combined with high-throughput molecular analyses opens a new approach for a deeper appreciation of how cellular behavior is influenced by the isolated microenvironment (specifically dECM). Additionally, the impact of these features with different decellularization techniques and generation of synthetic material scaffolds with desired attributes are informed. Ultimately, this mechanical profiling provides a new dimension to our understanding of decellularized matrix and its role in new applications.

A Dedifferentiation Strategy to Enhance the Osteogenic Potential of Dental Derived Stem Cells

Dental stem cells (DSCs) holds the ability to differentiate into numerous cell types. This property makes these cells particularly appropriate for therapeutic use in regenerative medicine. We report evidence that when DSCs undergo osteogenic differentiation, the osteoblast-like cells can be reverted back to a stem-like state and then further differentiated toward the osteogenic phenotype again, without gene manipulation. We have investigated two different MSCs types, both from dental tissues: dental follicle progenitor stem cells (DFPCs) and dental pulp stem cells (DPSCs). After osteogenic differentiation, both DFPCs and DPSCs can be reverted to a naïve stem cell-like status; importantly, dedifferentiated DSCs showed a greater potential to further differentiate toward the osteogenic phenotype. Our report aims to demonstrate for the first time that it is possible, under physiological conditions, to control the dedifferentiation of DSCs and that the rerouting of cell fate could potentially be used to enhance their osteogenic therapeutic potential. Significantly, this study first validates the use of dedifferentiated DSCs as an alternative source for bone tissue engineering.

Early Osteogenic Differentiation Stimulation of Dental Pulp Stem Cells by Calcitriol and Curcumin

Curcumin, as a natural phenolic substance, is extracted from the rhizome of Curcuma longa (turmeric), which is effective in bone healthfulness. Calcitriol is an effective hormone in regulating bone remodeling and mineral homeostasis and immune response. Mesenchymal stem cells (MSCs) are found in most dental tissues and resemble bone marrow-derived MSCs. In this work, we investigated the effect of combination and individual treatment of curcumin and calcitriol on early osteogenic differentiation of dental pulp stem cells (DPSCs). Early osteogenic differentiation was evaluated and confirmed by the gene expression level of ALP and its activity. Curcumin individually and in combination with calcitriol increased ALP activity and osteoblast-specific mRNA expression of ALP when DPSCs were cultured in an osteogenic medium. Calcitriol alone increased the enzyme more than in combination with curcumin. These findings demonstrate that curcumin can induce early osteogenic differentiation of DPSCs like calcitriol as a potent stimulant of osteogenesis.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

Decellularized bone extracellular matrix in skeletal tissue engineering

Bone possesses an intrinsic regenerative capacity, which can be compromised by aging, disease, trauma, and iatrogenesis (e.g. tumor resection, pharmacological). At present, autografts and allografts are the principal biological treatments available to replace large bone segments, but both entail several limitations that reduce wider use and consistent success. The use of decellularized extracellular matrices (ECM), often derived from xenogeneic sources, has been shown to favorably influence the immune response to injury and promote site-appropriate tissue regeneration. Decellularized bone ECM (dbECM), utilized in several forms - whole organ, particles, hydrogels - has shown promise in both in vitro and in vivo animal studies to promote osteogenic differentiation of stem/progenitor cells and enhance bone regeneration. However, dbECM has yet to be investigated in clinical studies, which are needed to determine the relative efficacy of this emerging biomaterial as compared with established treatments. This mini-review highlights the recent exploration of dbECM as a biomaterial for skeletal tissue engineering and considers modifications on its future use to more consistently promote bone regeneration.

In vitro Assessment of the DNA Damage Response in Dental Mesenchymal Stromal Cells Following Low Dose X-ray Exposure

Stem cells contained within the dental mesenchymal stromal cell (MSC) population are crucial for tissue homeostasis. Assuring their genomic stability is therefore essential. Exposure of stem cells to ionizing radiation (IR) is potentially detrimental for normal tissue homeostasis. Although it has been established that exposure to high doses of ionizing radiation (IR) has severe adverse effects on MSCs, knowledge about the impact of low doses of IR is lacking. Here we investigated the effect of low doses of X-irradiation with medical imaging beam settings (<0.1 Gray; 900 mGray per hour), in vitro, on pediatric dental mesenchymal stromal cells containing dental pulp stem cells from deciduous teeth, dental follicle progenitor cells and stem cells from the apical papilla. DNA double strand break (DSB) formation and repair kinetics were monitored by immunocytochemistry of γH2AX and 53BP1 as well as cell cycle progression by flow cytometry and cellular senescence by senescence-associated β-galactosidase assay and ELISA. Increased DNA DSB repair foci, after exposure to low doses of X-rays, were measured as early as 30 min post-irradiation. The number of DSBs returned to baseline levels 24 h after irradiation. Cell cycle analysis revealed marginal effects of IR on cell cycle progression, although a slight G₂/M phase arrest was seen in dental pulp stromal cells from deciduous teeth 72 h after irradiation. Despite this cell cycle arrest, no radiation-induced senescence was observed. In conclusion, low X-ray IR doses (< 0.1 Gray; 900 mGray per hour), were able to induce significant increases in the number of DNA DSBs repair foci, but cell cycle progression seems to be minimally affected. This highlights the need for more detailed and extensive studies on the effects of exposure to low IR doses on different mesenchymal stromal cells.

Development of Decellularized Oviductal Hydrogels as a Support for Rabbit Embryo Culture

The oviducts (fallopian tubes in mammals) function as the site of fertilization and provide necessary support for early embryonic development, mainly via embryonic exposure to the tubal microenvironment. The main objective of this study was to create an oviduct-specific extracellular matrix (oviECM) hydrogel rich in bioactive components that mimics the native environment, thus optimizing the developmental trajectories of cultured embryos. Rabbit oviducts were decellularized through SDS treatment and enzymatic digestion, and the acellular tissue was converted into oviductal pre-gel extracellular matrix (ECM) solutions. Incubation of these solutions at 37 °C resulted in stable hydrogels with a fibrous structure based on scanning electron microscopy. Histological staining, DNA quantification and colorimetric assays confirmed that the decellularized tissue and hydrogels contained no cellular or nuclear components but retained important components of the ECM, e.g. hyaluronic acid, glycoproteins and collagens. To evaluate the ability of oviECM hydrogels to maintain early embryonic development, two-cell rabbit embryos were cultured on oviECM-coated surfaces and compared to those cultured with standard techniques. Embryo development was similar in both conditions, with 95.9% and 98% of the embryos reaching the late morula/early blastocyst stage by 48 h under standard culture and oviECM conditions, respectively. Metabolomic analysis of culture media in the presence or absence of embryos, however, revealed that the oviECM coating may include signalling molecules and release compounds beneficial to embryo metabolism.

Advanced Multi-Dimensional Cellular Models as Emerging Reality to Reproduce In Vitro the Human Body Complexity

A hot topic in biomedical science is the implementation of more predictive in vitro models of human tissues to significantly improve the knowledge of physiological or pathological process, drugs discovery and screening. Bidimensional (2D) culture systems still represent good high-throughput options for basic research. Unfortunately, these systems are not able to recapitulate the in vivo three-dimensional (3D) environment of native tissues, resulting in a poor in vitro–in vivo translation. In addition, intra-species differences limited the use of animal data for predicting human responses, increasing in vivo preclinical failures and ethical concerns. Dealing with these challenges, in vitro 3D technological approaches were recently bioengineered as promising platforms able to closely capture the complexity of in vivo normal/pathological tissues. Potentially, such systems could resemble tissue-specific extracellular matrix (ECM), cell–cell and cell–ECM interactions and specific cell biological responses to mechanical and physical/chemical properties of the matrix. In this context, this review presents the state of the art of the most advanced progresses of the last years. A special attention to the emerging technologies for the development of human 3D disease-relevant and physiological models, varying from cell self-assembly (i.e., multicellular spheroids and organoids) to the use of biomaterials and microfluidic devices has been given.

Ex-vivo recellularisation and stem cell differentiation of a decellularised rat dental pulp matrix

Implementing the principles of tissue engineering within the clinical management of non-vital immature permanent teeth is of clinical interest. However, the ideal scaffold remains elusive. The aim of this work was to assess the feasibility of decellularising rat dental pulp tissue and evaluate the ability of such scaffold to support stem cell repopulation. Rat dental pulps were retrieved and divided into control and decellularised groups. The decellularisation protocol incorporated a low detergent concentration and hypotonic buffers. After decellularisation, the scaffolds were characterised histologically, immunohistochemistry and the residual DNA content quantified. Surface topography was also viewed under scanning electron microscopy. Biocompatibility was evaluated using cytotoxicity assays utilising L-929 cell line. Decellularised scaffolds were recellularised with human dental pulp stem cells up to 14 days in vitro. Cellular viability was assessed using LIVE/DEAD stain kit and the recellularised scaffolds were further assessed histologically and immunolabelled using makers for odontoblastic differentiation, cytoskeleton components and growth factors. Analysis of the decellularised scaffolds revealed an acellular matrix with histological preservation of structural components. Decellularised scaffolds were biocompatible and able to support stem cell survival following recellularisation. Immunolabelling of the recellularised scaffolds demonstrated positive cellular expression against the tested markers in culture. This study has demonstrated the feasibility of developing a biocompatible decellularised dental pulp scaffold, which is able to support dental pulp stem cell repopulation. Clinically, decellularised pulp tissue could possibly be a suitable scaffold for use within regenerative (reparative) endodontic techniques.

Decellularized bone matrix/oleoyl chitosan derived supramolecular injectable hydrogel promotes efficient bone integration

Hydrogels derived from decellularized extracellular matrix (ECM) have been widely used as a bioactive matrix for facilitating functional bone tissue regeneration. However, its poor mechanical strength and fast degradation restricts the extensive use for clinical application. Herein, we present a crosslinked decellularized bone ECM (DBM) and fatty acid modified chitosan (oleoyl chitosan, OC) based biohybrid hydrogel (DBM/OC) for delivering human amnion-derived stem cells (HAMSCs) for bone regeneration. DBM/OC hydrogel were benchmarked against collagen-I/OC (Col-I/OC) based hydrogel in terms of their morphological characteristics, rheological analysis, and biological performances. DBM/OC hydrogel with its endogenous growth factors recapitulates the nanofibrillar 3D tissue microenvironment with improved mechanical strength and also exhibited antimicrobial potential along with superior proliferation/differentiation ability. HAMSCs encapsulation potential of DBM/OC hydrogel was established by well spread cytoskeleton morphology post 14 days of cultivation. Further, ex-vivo chick chorioallantoic membrane (CAM) assay revealed excellent neovascularization potential of DBM/OC hydrogel. Subcutaneously implanted DBM/OC hydrogel did not trigger any severe immune response or infection in the host after 21 days. Also, DBM/OC hydrogels and HAMSCs encapsulated DBM/OC hydrogels were implanted at the tibial defect in a rabbit model to assess the bone regeneration ability. Quantitative micro-CT and histomorphological analysis demonstrated that HAMSCs encapsulated DBM/OC hydrogel can support more mature mineralized bone formation at the defect area compared to DBM/OC hydrogel or SHAM. These findings manifested the efficacy of DBM/OC hydrogel as a functional cell-delivery vehicle and osteoinductive template to accelerate bone regeneration.

Decellularization systems and devices: State-of-the-art

Extracellular matrix (ECM) is a natural biomaterial scaffold that provides biochemical and structural support to its surrounding cells, forming tissue and respective organs. These ECM proteins can be extracted from organs and tissues through decellularization, which is the process of removing cellular content and nuclear material from the organs to obtain decellularized ECM (dECM). dECM is a versatile and functional biomaterial that can be used as the base component of bioinks for rebuilding tissue and organs. Intact dECM of whole organs can be used as a scaffold for recellularization with human stem cells to produce a functioning organ. As decellularization is a relatively new lab process, the associated technologies and devices are largely non-standardized and only available in small, lab-specific scales. Additionally, there is a lack of standardized protocols to analyze the quality and consistency of harvested dECM for medical applications. This review discusses the relevant decellularization systems and devices currently available to facilitate further development of this process for larger scales with the intention to commercialize dECM materials. STATEMENT OF SIGNIFICANCE: Extracellular matrix (ECM) is a natural cocktail of biomaterials that provides biochemical and structural support to its surrounding cells. ECM proteins are extracted from organs and tissues through decellularization. Being a versatile and functional biomaterial, decellularized extracellular matrix (dECM) is being used as base component of bioinks/hydrogels for rebuilding of tissue and organ constructs. Decellularization is a relatively new lab process with associated technologies/devices being largely non-standardized and only available in lab-specific scales. We discuss categories of decellularization systems and devices for the first time being used in academic and commercial settings. We highlight inherent challenges with the current systems and suggest possible solutions. We comment on further development of these processes for large-scale and commercial applications of dECM.

Dental stem cells: The role of biomaterials and scaffolds in developing novel therapeutic strategies

Dental stem cells (DSCs) are self-renewable cells that can be obtained easily from dental tissues, and are a desirable source of autologous stem cells. The use of DSCs for stem cell transplantation therapeutic approaches is attractive due to their simple isolation, high plasticity, immunomodulatory properties, and multipotential abilities. Using appropriate scaffolds loaded with favorable biomolecules, such as growth factors, and cytokines, can improve the proliferation, differentiation, migration, and functional capacity of DSCs and can optimize the cellular morphology to build tissue constructs for specific purposes. An enormous variety of scaffolds have been used for tissue engineering with DSCs. Of these, the scaffolds that particularly mimic tissue-specific micromilieu and loaded with biomolecules favorably regulate angiogenesis, cell-matrix interactions, degradation of extracellular matrix, organized matrix formation, and the mineralization abilities of DSCs in both in vitro and in vivo conditions. DSCs represent a promising cell source for tissue engineering, especially for tooth, bone, and neural tissue restoration. The purpose of the present review is to summarize the current developments in the major scaffolding approaches as crucial guidelines for tissue engineering using DSCs and compare their effects in tissue and organ regeneration.

Early Odontogenic Differentiation of Dental Pulp Stem Cells Treated with Nanohydroxyapatite-Silica-Glass Ionomer Cement

This study aimed to investigate the effects of nanohydroxyapatite–silica–glass ionomer cement (nanoHA–silica–GIC) on the differentiation of dental pulp stem cells (DPSCs) into odontogenic lineage. DPSCs were cultured in complete Minimum Essential Medium Eagle—Alpha Modification (α-MEM) with or without nanoHA–silica–GIC extract and conventional glass ionomer cement (cGIC) extract. Odontogenic differentiation of DPSCs was evaluated by real-time reverse transcription polymerase chain reaction (rRT–PCR) for odontogenic markers: dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP1), osteocalcin (OCN), osteopontin (OPN), alkaline phosphatase (ALP), collagen type I (COL1A1), and runt-related transcription factor 2 (RUNX2) on day 1, 7, 10, 14, and 21, which were normalized to the house keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Untreated DPSCs were used as a control throughout the study. The expressions of DSPP and DMP1 were higher on days 7 and 10, that of OCN on day 10, those of OPN and ALP on day 14, and that of RUNX2 on day 1; COL1A1 exhibited a time-dependent increase from day 7 to day 14. Despite the above time-dependent variations, the expressions were comparable at a concentration of 6.25 mg/mL between the nanoHA–silica–GIC and cGIC groups. This offers empirical support that nanoHA–silica–GIC plays a role in the odontogenic differentiation of DPSCs.

Decellularized Extracellular Matrix-based Bioinks for Engineering Tissue- and Organ-specific Microenvironments

Biomaterials-based biofabrication methods have gained much attention in recent years. Among them, 3D cell printing is a pioneering technology to facilitate the recapitulation of unique features of complex human tissues and organs with high process flexibility and versatility. Bioinks, combinations of printable hydrogel and cells, can be utilized to create 3D cell-printed constructs. The bioactive cues of bioinks directly trigger cells to induce tissue morphogenesis. Among the various printable hydrogels, the tissue- and organ-specific decellularized extracellular matrix (dECM) can exert synergistic effects in supporting various cells at any component by facilitating specific physiological properties. In this review, we aim to discuss a new paradigm of dECM-based bioinks able to recapitulate the inherent microenvironmental niche in 3D cell-printed constructs. This review can serve as a toolbox for biomedical engineers who want to understand the beneficial characteristics of the dECM-based bioinks and a basic set of fundamental criteria for printing functional human tissues and organs.

Pancreatic extracellular matrix and platelet-rich plasma constructing injectable hydrogel for pancreas tissue engineering

The development of pancreatic extracellular matrices enriched with insulin-secreting β-cells is a promising tissue engineering approach to treat type 1 diabetes. However, its long-term therapeutic efficacy is restricted by the defensive mechanism of host immune response and the lack of developed vascularization as appropriate after transplantation. Platelet-rich plasma (PRP), as an autologous platelet concentrate, contains a large number of active factors that are essential for the cell viability, vascularization, and immune regulation. In this study, we have incorporated pancreatic extracellular matrix (PEM) with PRP to develop a three-dimensional (3D) injectable PEM-PRP hydrogel to coculture and transplant rat insulinoma cells (INS-1) and human umbilical vein endothelial cells (HUVECs). Results from this study demonstrated that PEM-PRP hydrogel mimicked the biochemical compositions of native extracellular matrices, and possessed the enhanced elastic modulus and resistance to enzymatic degradation that enabled biomaterials to maintain its volume and slowly degrade. Additionally, PEM-PRP hydrogel could release growth factors in a sustained manner. In vitro, PEM-PRP hydrogel significantly promoted the viability, insulin-secreting function, and insulin gene expression of gel encapsulated INS-1 cells. Moreover, HUVECs encapsulated in PEM-PRP hydrogel were found to constitute many lumen-like structures and exhibited high expression of proangiogenic genes. In vivo transplantation of PEM-PRP hydrogel encapsulated with INS-1 cells and HUVECs improved the viability of INS-1 cells, promoted vascularization, inhibited the host inflammatory response, and reversed hyperglycemia of diabetic rats. Our study suggests that the PEM-PRP hydrogel offers excellent biocompatibility and proangiogenic property, and may serve as an effective biomaterial platform to maintain the long-term survival and function of insulin-secreting β cells.

Induction of osteogenic differentiation by demineralized and decellularized bovine extracellular matrix derived hydrogels associated with barium titanate

Bone tissue-derive biomaterials have become of great interest to treat diseases of the skeletal system. Biological scaffolds of demineralized and decellularized extracellular matrices (ECM) have been developed and one of these options are ECM hydrogels derived from bovine bone. Nanomaterials may be able to regulate stem cell differentiation due to their unique physical-chemical properties. The present work aimed to evaluate the osteoinductive effects of ECM hydrogels associated with barium titanate nanoparticles (BTNP) on dental pulp cells derived from exfoliated teeth. The addition of BTNP in the ECM derived hydrogel did not affect cell proliferation and the formation of bone nodules. Furthermore, it increased the expression of bone alkaline phosphatase. The results demonstrated that the nanobiocomposites were able to promote the osteogenic differentiation, even in the absence of chemical inducing factors for osteogenic differentiation. In conclusion, bovine bone ECM hydrogel combined with BTNP presented and increased expression of markers of osteogenic differentiation in the absence of chemical inducing factors.

Therapeutic Functions of Stem Cells from Oral Cavity: An Update

Adult stem cells have been developed as therapeutics for tissue regeneration and immune regulation due to their self-renewing, differentiating, and paracrine functions. Recently, a variety of adult stem cells from the oral cavity have been discovered, and these dental stem cells mostly exhibit the characteristics of mesenchymal stem cells (MSCs). Dental MSCs can be applied for the replacement of dental and oral tissues against various tissue-damaging conditions including dental caries, periodontitis, and oral cancers, as well as for systemic regulation of excessive inflammation in immune disorders, such as autoimmune diseases and hypersensitivity. Therefore, in this review, we summarized and updated the types of dental stem cells and their functions to exert therapeutic efficacy against diseases.

Mussel-Inspired Biocoating for Improving the Adhesion of Dental Pulp Stem Cells in Dental Pulp Regeneration

Dental pulp engineering possesses a promising perspective to replacing lost pulp in the root canal and restoring its functions. Stable adhesion of dental pulp stem cells (DPSCs) on the root canal dentin wall is a key element required for reconstruction of a functional odontoblast layer in dental pulp regeneration. To address this challenge, dopamine-modified hyaluronic acid (DA-HA) is coated on dentin to obtain a stable adhesion of DPSCs. The dopamine segment provides adhesion ability to the coating, and the hyaluronic acid increases the biocompatibility. The results show that DPSCs can adhere on the DA-HA coated dentin slice better than those without coating. Simultaneously, DPSCs proliferation can be further promoted on the prepared coating. Therefore, the DA-HA coating may provide a possible way to immobilize odontoblast cell onto dentin surface for pulp regeneration.

Preparation, Characterization, and Biological Testing of Novel Magnetic Nanocomposite Hydrogels

To provide a novel approach for the clinical treatment of cartilage tissue defects, we prepared a new type of magnetic nanocomposite hydrogel with an optimal raw material ratio using Fe3O4, polyvinyl alcohol (PVA), and type-II collagen (COLII). Briefly, five groups of PVA and collagen hydrogel matrices with different mass ratios were prepared by a combination of repeated thawing cycles and foam-frozen ice crystal separation methods. Microscopic characterization was conducted using electron microscopy, and the biomechanical properties of each group of hydrogels were then tested. The highest performing component hydrogel matrix was selected after which Fe3O4 with different mass ratios was introduced to construct a new Fe3O4/PVA/COLII hydrogel. The prepared composite hydrogels were also microscopically characterized using electron microscopy along with scanning, measurements for porosity and moisture content, and biomechanical, infrared spectrum and degradation performance testing. CCK-8 detection and staining to determine the amount of living and dead cells were also performed. Collectively, these results showed that PVA/COLII,95:5 was the optimal hydrogel matrix. Using this hydrogel matrix, five groups of composite hydrogels with different Fe3O4 mass ratios were then prepared. There was no significant difference in the microscopic characteristics between these different hydrogels. Fe3O4/PVA/COLII,5:95:5 had better physical properties as well as swelling performance and cell compatibility. The PVA/COLII,95:5 hydrogel matrix was determined to be the best, while the new magnetic nanocomposite hydrogel Fe3O4/PVA/COLII,5:95:5 had good, comprehensive properties.

Promising Scaffold-Free Approaches in Translational Dentistry

Regenerative medicine has recently improved the principal therapies in several medical fields. In the past ten years, the continuous search for novel approaches to treat the most common dental pathologies has developed a new branch called regenerative dentistry. The main research fields of translational dentistry involve biomimetic materials, orally derived stem cells, and tissue engineering to populate scaffolds with autologous stem cells and bioactive growth factors. The scientific literature has reported two main research trends in regenerative dentistry: scaffold-based and scaffold-free approaches. This article aims to critically review the main biological properties of scaffold-free regenerative procedures in dentistry. The most impactful pros and cons of the exosomes, the leading role of hypoxia-based mesenchymal stem cells (MSCs), and the strategic use of heat shock proteins in regenerative dentistry will be highlighted and discussed in terms of the use of such tools in dental regeneration and repair.