Chitosan-collagen biomembrane embedded with calcium-aluminate enhances dentinogenic potential of pulp cells

Chitosan-Calcium Aluminate as a Cell-homing Scaffold: Its Bioactivity Testing in a Microphysiological Dental Pulp Platform

In vitro models of the dental pulp microenvironment have been proposed for the assessment of biomaterials, to minimise animal use in operative dentistry. In this study, a scaffold/3-D dental pulp cell culture interface was created in a microchip, under simulated dental pulp pressure, to evaluate the cell-homing potential of a chitosan (CH) scaffold functionalised with calcium aluminate (the 'CHAlCa scaffold'). This microphysiological platform was cultured at a pressure of 15 cm H2O for up to 14 days; cell viability, migration and odontoblastic differentiation were then assessed. The CHAlCa scaffold exhibited intense chemotactic potential, causing cells to migrate from the 3-D culture to its surface, followed by infiltration into the macroporous structure of the scaffold. By contrast, the cells in the presence of the non-functionalised chitosan scaffold showed low cell migration and no cell infiltration. CHAlCa scaffold bioactivity was confirmed in dentin sialophosphoprotein-positive migrating cells, and odontoblastic markers were upregulated in 3-D culture. Finally, in situ mineralised matrix deposition by the cells was confirmed in an Alizarin Red-based assay, in which the CHAlCa and CH scaffolds were adapted to fit within dentin discs. More intense deposition of matrix was observed with the CHAlCa scaffold, as compared to the CH scaffold. In summary, we present an in vitro platform that provides a simple and reproducible model for selecting and developing innovative biomaterials through the assessment of their cell-homing potential. By using this platform, it was shown that the combination of calcium aluminate and chitosan has potential as an inductive biomaterial that can mediate dentin tissue regeneration during cell-homing therapies.

In Vivo Evaluation of Collagen and Chitosan Scaffold, Associated or Not with Stem Cells, in Bone Repair

Natural polymers are increasingly being used in tissue engineering due to their ability to mimic the extracellular matrix and to act as a scaffold for cell growth, as well as their possible combination with other osteogenic factors, such as mesenchymal stem cells (MSCs) derived from dental pulp, in an attempt to enhance bone regeneration during the healing of a bone defect. Therefore, the aim of this study was to analyze the repair of mandibular defects filled with a new collagen/chitosan scaffold, seeded or not with MSCs derived from dental pulp. Twenty-eight rats were submitted to surgery for creation of a defect in the right mandibular ramus and divided into the following groups: G1 (control group; mandibular defect with clot); G2 (defect filled with dental pulp mesenchymal stem cells-DPSCs); G3 (defect filled with collagen/chitosan scaffold); and G4 (collagen/chitosan scaffold seeded with DPSCs). The analysis of the scaffold microstructure showed a homogenous material with an adequate percentage of porosity. Macroscopic and radiological examination of the defect area after 6 weeks post-surgery revealed the absence of complete repair, as well as absence of signs of infection, which could indicate rejection of the implants. Histomorphometric analysis of the mandibular defect area showed that bone formation occurred in a centripetal fashion, starting from the borders and progressing towards the center of the defect in all groups. Lower bone formation was observed in G1 when compared to the other groups and G2 exhibited greater osteoregenerative capacity, followed by G4 and G3. In conclusion, the scaffold used showed osteoconductivity, no foreign body reaction, malleability and ease of manipulation, but did not obtain promising results for association with DPSCs.

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.

Cytocompatibility and bioactivity of calcium hydroxide-containing nanofiber scaffolds loaded with fibronectin for dentin tissue engineering

OBJECTIVES

The aim of this study was to characterize polycaprolactone-based nanofiber scaffolds (PCL) incorporated with calcium hydroxide (CH) and evaluate their bioactivity on human dental pulp cells (HDPCs) when loaded with fibronectin (FN).

MATERIALS AND METHODS

CH (0.1%; 0.2%; 0.4% w/v; or 0%) was incorporated into PCL (10% w/v) scaffolds prepared by electrospinning. Morphology and composition were characterized using SEM/EDS. HDPCs were seeded on the scaffolds and evaluated for viability (alamarBlue; Live/Dead), and adhesion/spreading (F-actin). Next, scaffolds containing 0.4% CH were loaded with FN (20 µg/mL). HDPCs were evaluated for viability, adhesion/spreading, migration (Trans-well), gene expression (RT-qPCR), alkaline phosphatase activity (ALP), and mineralization nodules (Alizarin Red). Data were submitted to ANOVA and post-hoc tests (α = 5%).

RESULTS

Nanofibers with larger diameter were seen as CH concentration increased, while there was no effect on interfibrillar spaces. An increase in cell viability was seen for 0.4% CH, in all periods. Incorporation of CH and FN into the scaffolds increased cellular migration, spread, and viability, all intensified when CH and FN were combined. ALPL and DSPP expression, and ALP activity were not affected by CH and FN. COL1A1 was downregulated in all groups, while DMP1 was upregulated in the presence of CH, with no differences for the groups loaded with FN. CH increased the formation of mineralized matrix, which was not influenced by FN.

CONCLUSIONS

In conclusion, the incorporation of CH enhanced the odontogenic potential of HDPCs, irrespective of the presence of FN. The PCL + 0.4% CH formulation may be a useful strategy for use in dentin tissue engineering.

CLINICAL RELEVANCE

A change in the form of presentation of calcium hydroxide-based materials used for direct pulp capping can increase biocompatibility and prolong the vitality of dental pulp.

Platform technologies for regenerative endodontics from multifunctional biomaterials to tooth-on-a-chip strategies

OBJECTIVES

The aim of this review is to highlight recent progress in the field of biomaterials-mediated dental pulp tissue engineering. Specifically, we aim to underscore the critical design criteria of biomaterial platforms that are advantageous for pulp tissue engineering, discuss models for preclinical evaluation, and present new and innovative multifunctional strategies that hold promise for clinical translation.

MATERIALS AND METHODS

The current article is a comprehensive overview of recent progress over the last 5 years. In detail, we surveyed the literature in regenerative pulp biology, including novel biologic and biomaterials approaches, and those that combined multiple strategies, towards more clinically relevant models. PubMed searches were performed using the keywords: "regenerative dentistry," "dental pulp regeneration," "regenerative endodontics," and "dental pulp therapy."

RESULTS

Significant contributions to the field of regenerative dentistry have been made in the last 5 years, as evidenced by a significant body of publications. We chose exemplary studies that we believe are progressive towards clinically translatable solutions. We close this review with an outlook towards the future of pulp regeneration strategies and their clinical translation.

CONCLUSIONS

Current clinical treatments lack functional and predictable pulp regeneration and are more focused on the treatment of the consequences of pulp exposure, rather than the restoration of healthy dental pulp.

CLINICAL RELEVANCE

Clinically, there is great demand for bioinspired biomaterial strategies that are safe, efficacious, and easy to use, and clinicians are eager for their clinical translation. In particular, we place emphasis on strategies that combine favorable angiogenesis, mineralization, and functional tissue formation, while limiting immune reaction, risk of microbial infection, and pulp necrosis.

Hard Dental Tissues Regeneration-Approaches and Challenges

With the development of the modern concept of tissue engineering approach and the discovery of the potential of stem cells in dentistry, the regeneration of hard dental tissues has become a reality and a priority of modern dentistry. The present review reports the recent advances on stem-cell based regeneration strategies for hard dental tissues and analyze the feasibility of stem cells and of growth factors in scaffolds-based or scaffold-free approaches in inducing the regeneration of either the whole tooth or only of its component structures.

Chitosan-Based Biomaterial, Calcium Hydroxide and Chlorhexidine for Potential Use as Intracanal Medication

The objective of this study was to develop a chitosan-based biomaterial with calcium hydroxide and 2% chlorhexidine for intracanal treatment application and, consequently, to diminish the number of microorganisms in the root canal system. The chitosan solution was prepared by dissolving it in 2% and 4% acetic acid (v/v) for 1 h at room temperature (25 °C) with magnetic agitation (430 rpm). Calcium hydroxide was obtained in two stages: the first was the synthesis of the calcium oxide—CaO, and the second was that of the calcium hydroxide—Ca(OH)₂. The samples were developed using different concentrations of chitosan, calcium hydroxide, and chlorhexidine 2%. They were codified as Ca(OH)₂ + Q2% (M1), Ca(OH)₂ + Q4% (M2), Ca(OH)₂ + Q2% + CLX (M3), Ca(OH)₂ + Q4% + CLX (M4), Ca(OH)₂ + Q2% + PEG (M5), and Ca(OH)₂ + Q4% + PEG (M6). They were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and rheological measurement, and the antimicrobial activity was evaluated in vitro. Characteristic absorption bands of the source materials used in this research were observed in the FTIR spectra. The X-ray diffraction technique indicated that the material has a semi-crystalline structure and that the presence of calcium hydroxide made the biomaterial more crystalline. The viscosity measurement showed a pseudoplastic behavior of the studied samples. The microbiologic analysis was positive for all samples tested, with bigger inhibition zones for the samples M3 and M4. As a result, we conclude that the formulation developed based on chitosan is promising and has potential to be an intracanal medication.

Influence of nanoparticulated chitosan on the biomodification of eroded dentin: clinical and photographic longitudinal analysis of restorations

To evaluate the influence of the pre-treatment with 2.5% nanoparticulate chitosan (2.5% NanoChi) solution on eroded dentin before the restorative dental treatment. The sample consisted of 22 patients (age between 33 and 52 years) with shallow or medium erosion lesions located in two homologous teeth. The teeth were randomly assigned according to dentin treatment: with 2.5% NanoChi and without with chitosan (control). The NanoChi were applied immediately after acid etching. The teeth were restored with Single Bond Universal (3 M) and Charisma resin (Kulzer). Analyzes were done using modified USPHS (retention, secondary caries, marginal adaptation, and sensitivity) and photographic (color, marginal pigmentation, and anatomical form) criteria at 7 days (baseline) and 1 year. Population demographics, Kaplan-Meier estimates and log-rank test (Mantel-Cox) were calculated for 1 year (α = 0.05). No significant difference was found in the survival rates between groups (p > 0.05) at 7 days and 1 year after treatment. After 7 days, 100% of the restorations were scored as Alpha on all criteria. After 1 year, 91% of the NanoChi restorations were scored as Alpha and 9% as Charlie for the retention, marginal adaptation, and anatomical form criteria, while 86% of the control restorations (without NanoChi) received the Alpha score and 14% received the Charlie. Secondary caries, sensitivity, color, and marginal pigmentation criteria were scored as Alpha in 100% of the restorations. The biomodification of eroded dentin with 2.5% NanoChi did not influence the survival of the restorations after 1 year. The application of 2.5% NanoChi on eroded dentin did not increase failures of resin restorations after 1 year and it can be used as a pre-treatment solution.

Blended Natural Support Materials-Collagen Based Hydrogels Used in Biomedicine

Due to their unique properties-the are biocompatible, easily accessible, and inexpensive with programmable properties-biopolymers are used in pharmaceutical and biomedical research, as well as in cosmetics and food. Collagen is one of the most-used biomaterials in biomedicine, being the most abundant protein in animals with a triple helices structure, biocompatible, biomimetic, biodegradable, and hemostatic. Its disadvantages are its poor mechanical and thermal properties and enzymatic degradation. In order to solve this problem and to use its benefits, collagen can be used blended with other biomaterials such as alginate, chitosan, and cellulose. The purpose of this review article is to offer a brief paper with updated information on blended collagen-based formulations and their potential application in biomedicine.

Periodontal Ligament Cell Sheets and RGD-Modified Chitosan Improved Regeneration in the Horizontal Periodontal Defect Model

Objective  The aim of this study was to examine the potential of periodontal ligament (PDL) cells sheet and arginine-glycyl-aspartic acid (RGD)-modified chitosan scaffold for periodontal tissue regeneration in horizontal periodontal defect model.

Materials and Methods  PDL cell cytotoxicity was tested with 3–[4,5- dimethylthiazol-2yl]–2,5-diphenyl-2H-tetrazolium bromide assay. Cell migration toward the chitosan-based materials was analyzed with trans-well migration assay. Horizontal periodontal defect model was created in four maxillary and mandibular lateral incisors of Macaque nemestrina . Following periodontal therapy, the sites were transplanted with various regenerative materials: (1) chitosan, (2) RGD-modified chitosan, (3) PDL cell sheet with chitosan, (4) PDL cell sheet with RGD-modified chitosan. The periodontal tissue regeneration was evaluated clinically and radiographically. Gingival crevicular fluids were collected each week to evaluate cementum protein-1 (CEMP-1) expression with enzyme-linked immunosorbent assay, while the biopsies were retrieved after 4 weeks for histological and microcomputed tomography evaluation.

Statistical Analysis  Data was statistically analyzed using GraphPad Prism 6 for MacOS X. Normality was tested using the Shapiro–Wilk normality test. The Kruskal–Wallis test was used to compare the groups. Significance was accepted when p < 0.05.

Results  Clinical examination revealed more epithelial attachment was formed in the group with PDL cell sheet with RGD-modified chitosan. Similarly, digital subtraction radiography analysis showed higher gray scale, an indication of higher alveolar bone density surrounded the transplanted area, as well as higher CEMP-1 protein expression in this group. The incorporation of RGD peptide to chitosan scaffold in the group with or without PDL cells sheet reduced the distance of cement–enamel junction to the alveolar bone crest; hence, more periodontal tissue formed.

Conclusions  Horizontal periodontal defect model could be successfully created in M. nemestrina model. Combination of PDL cell sheet and RGD-modified chitosan resulted in the higher potential for periodontal tissue regeneration. The results of this study highlight the PDL cell sheet and RGD-modified chitosan as a promising approach for future clinical use in periodontal regeneration.

Tissue Engineering Approaches for Enamel, Dentin, and Pulp Regeneration: An Update

Stem/progenitor cells are undifferentiated cells characterized by their exclusive ability for self-renewal and multilineage differentiation potential. In recent years, researchers and investigations explored the prospect of employing stem/progenitor cell therapy in regenerative medicine, especially stem/progenitor cells originating from the oral tissues. In this context, the regeneration of the lost dental tissues including enamel, dentin, and the dental pulp are pivotal targets for stem/progenitor cell therapy. The present review elaborates on the different sources of stem/progenitor cells and their potential clinical applications to regenerate enamel, dentin, and the dental pulpal tissues.

Synergistic potential of 1α,25-dihydroxyvitamin D3 and calcium-aluminate-chitosan scaffolds with dental pulp cells

OBJECTIVES

This study aimed to develop a porous chitosan-calcium-aluminate scaffold (CH-AlCa) in combination with a bioactive dosage of 1α,25-dihydroxyvitamin D3 (1α,25VD), to be used as a bioactive substrate capable to increase the odontogenic potential of human dental pulp cells (HDPCs).

MATERIALS AND METHODS

The porous CH-AlCa was developed by the incorporation of an AlCa suspension into a CH solution under vigorous agitation, followed by phase separation at low temperature. Scaffold architecture, porosity, and calcium release were evaluated. Thereafter, the synergistic potential of CH-AlCa and 1 nM 1α,25VD, selected by a dose-response assay, for HDPCs seeded onto the materials was assessed.

RESULTS

The CH-AlCa featured an organized and interconnected pore network, with increased porosity in comparison with that of plain chitosan scaffolds (CH). Increased odontoblastic phenotype expression on the human dental pulp cell (HDPC)/CH and HDPC/CH-AlCa constructs in the presence of 1 nM 1α,25VD was detected, since alkaline phosphatase activity, mineralized matrix deposition, dentin sialophosphoprotein/dentin matrix acidic phosphoprotein 1 mRNA expression, and cell migration were overstimulated. This drug featured a synergistic effect with CH-AlCa, since the highest values of cell migration and odontoblastic markers expression were observed in this experimental condition.

CONCLUSIONS

The experimental CH-AlCa scaffold increases the chemotaxis and regenerative potential of HDPCs, and the addition of low-dosage 1α,25VD to this scaffold enhances the potential of these cells to express an odontoblastic phenotype.

CLINICAL RELEVANCE

Chitosan scaffolds enriched with calcium-aluminate in association with low dosages of 1α,25-dihydroxyvitamin D3 provide a highly bioactive microenvironment for dental pulp cells prone to dentin regeneration, thus providing potential as a cell-free tissue engineering system for direct pulp capping.

Repair of Bone Defects with Chitosan-Collagen Biomembrane and Scaffold Containing Calcium Aluminate Cement

Innovative biomaterials can provide a promising new direction for the treatment of bone defects, stimulating a proper repair process, with no damage to adjacent tissues. The purpose of this in vivo study was to evaluate the biocompatibility and the osteoinductive capacity of chitosan-collagen biomembrane and scaffold containing calcium aluminate cement. Eighteen New Zealand white rabbits (Oryctolagus cuniculus) were distributed according to the experimental times of analysis (7, 15 and 30 days). Four bone defects were created in the rabbits calvaria, which were individually filled with the biomembrane, scaffold, blood clot (negative control) and autologous bone (positive control). Histopathological analysis was performed using optical microscope at 32´, 64´, 125´ and 320´ magnifications. Cell response to inflammation and new bone tissue formation was quantified using a score system. The biomembrane group presented greater inflammatory response at 15 days, with significant difference to autologous bone group (p<0.05). There was no statistically significant difference for foreign body type reaction among groups (p>0.05). Concerning new bone formation, linear closure of the defect area was observed more evidently in the group with autologous bone. The scaffold group presented similar results compared with the autologous bone group at 30 days (p>0.05). Both tested biomaterials presented similar biocompatibility compared with the control groups. In addition, the biomembrane and scaffold presented similar osteoinductive capacity, stimulating bone repair process in the course of the experimental time intervals.

Progress in the use of dental pulp stem cells in regenerative medicine

The field of tissue engineering is emerging as a multidisciplinary area with promising potential for regenerating new tissues and organs. This approach requires the involvement of three essential components: stem cells, scaffolds and growth factors. To date, dental pulp stem cells have received special attention because they represent a readily accessible source of stem cells. Their high plasticity and multipotential capacity to differentiate into a large array of tissues can be explained by its neural crest origin, which supports applications beyond the scope of oral tissues. Many isolation, culture and cryopreservation protocols have been proposed that are known to affect cell phenotype, proliferation rate and differentiation capacity. The clinical applications of therapies based on dental pulp stem cells demand the development of new biomaterials suitable for regenerative purposes that can act as scaffolds to handle, carry and implant stem cells into patients. Currently, the development of xeno-free culture media is emerging as a means of standardization to improve safe and reproducibility. The present review aims to describe the current knowledge of dental pulp stem cells, considering in depth the key aspects related to the characterization, establishment, maintenance and cryopreservation of primary cultures and their involvement in the multilineage differentiation potential. The main clinical applications for these stem cells and their combination with several biomaterials is also covered.

Odontogenic differentiation potential of human dental pulp cells cultured on a calcium-aluminate enriched chitosan-collagen scaffold

OBJECTIVE

The study aims to evaluate the odontogenic potential of human dental pulp cells (HDPCs) in contact with an experimental porous chitosan-collagen scaffold (CHC) enriched or not with a mineral phase of calcium-aluminate (CHC-CA).

MATERIAL AND METHODS

To assess the chemotactic effect of the materials, we placed HDPCs seeded on transwell membranes in intimate contact with the CHC or CHC-CA surface, and the cell migration was monitored for 48 h. Additionally, cells were seeded onto the material surface, and the viability and proliferation were evaluated at several time points. To assess the odontoblastic differentiation, we evaluated ALP activity, DSPP/DMP-1 gene expression, and mineralized matrix deposition. HDPCs cultured onto a polystyrene surface (monolayer) were used as negative control group.

RESULTS

The experimental CHC-CA scaffold induced intense migration of HDPCs through transwell membranes, with cells attaching to and spreading on the material surface after 24-h incubation. Also, the HDPCs seeded onto the CHC-CA scaffold were capable of migrating inside it, remaining viable and featuring a proliferative rate more rapid than that of CHC and control groups at 7 and 14 days of cell culture. At long-term culture, cells in the CHC-CA scaffold featured the highest deposition of mineralized matrix and expression of odontoblastic markers (ALP activity and DSPP/DMP-1 gene expression).

CONCLUSIONS

According to the results, the CHC-CA scaffold is a bioactive and cytocompatible material capable of increasing the odontogenic potential of human pulp cells. Based on analysis of the positive data obtained in this study, one can suggest that the CHC-CA scaffold is an interesting future candidate for the treatment of exposed pulps.

CLINICAL RELEVANCE

The experimental scaffold composed by a chitosan-collagen matrix mineralized with calcium aluminate seems to be an interesting candidate for in vivo application as a cell-free approach to dentin tissue engineering, which may open a new perspective for the treatment of exposed pulp tissue.