Osteogenic differentiation of human dental pulp stem cells on β-tricalcium phosphate/poly (l-lactic acid/caprolactone) three-dimensional scaffolds

Temporomandibular Joint Fibrocartilage Contains CD105 Positive Mouse Mesenchymal Stem/Progenitor Cells with Increased Chondrogenic Potential

Objective

A specific type of mesenchymal stem/progenitor cells (MSPCs), CD105+ is reported to aid in cartilage regeneration through TGF-β/Smad2-signalling. The purpose of this study was to identify and characterize CD105+ MSPCs in temporomandibular joint (TMJ) cartilage.

Materials and Methods

MSPCs were isolated from mouse TMJ condyle explants and evaluated for their clonogenicity and pluripotential abilities. MSPC were examined for CD105 antigen using immunohistochemistry and flow cytometry.

Results

Immunohistochemistry revealed presence of CD105+ MSPCs in the proliferative zone of condyle's cartilage. Only 0.2% of isolated MSPCs exhibited CD105, along with the stem cell surface markers CD44 and Sca-1. In CD105+ MSPCs, intracellular immunostaining revealed significantly higher (p < 0.05) protein levels of collagen type 1, 2, proteoglycan 4. Ability for chondrogenic differentiation was found to be significantly higher (p < 0.05) after 4 weeks compared to CD105- cells, using alcian blue staining. CD105+ cells were found to resemble an early MSPC subgroup with significantly higher gene expression of biglycan, proteoglycan 4, collagen type 2, Gli2, Sox5 (p < 0.001) and Sox9 (p < 0.05). In contrast, significantly lower levels of Runx2 (p < 0.05), Osterix, Trps1, Col10a1 (p < 0.01), Ihh (p < 0.001) related to chondrocyte senescence and commitment to osteogenic lineage, were observed compared to CD105- cells.

Conclusion

The study showed the existence of a CD105+ MSPC subgroup within TMJ fibrocartilage that may be activated to aid in fibrocartilage repair.

The Self Assembling peptide P11-4 influences viability and osteogenic differentiation of stem cells of the apical papilla (SCAP)

OBJECTIVE

to analyze the effect of P₁₁-4 self-assembly peptide on cell viability and osteogenic capacity of SCAPs through mineral deposition and gene expression of osteogenic markers. .

METHODS

SCAPs were seeded in contact with P₁₁-4 (10 µg/ml, 100 µg/ml and 1 mg/ml) solution. Cell viability was evaluated using a colorimetric assay MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) in an experimental time of 24, 48 and 72 h (n=7). Mineral deposition and quantification provided by the cells was tested using the Alizarin Red staining and Cetylpyridinium Chloride (CPC), respectively, after 30 days (n=4). Gene expression of Runt-related transcription factor 2 (RUNX2), Alkaline phosphatase (ALP) and Osteocalcin (OCN) was quantified using quantitative polymerase chain reaction (RT-qPCR), at 3 and 7 days with Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as the housekeeping gene, and relative gene expression was measured using the ΔΔCq method. Data were analyzed using Kruskall-Wallis followed by multiple comparisons, and T-test for gene expression with α=0.05.

RESULTS

All tested concentrations (10 µg/ml, 100 µg/ml and 1 mg/ml) were not cytotoxic at time 24 and 48 h. After 72 h, a slight decrease in cell viability was observed for the lowest concentration (10 µg/ml). The concentration of 100 µg/ml P11-4 showed the highest mineral deposition. However, qPCR analysis of P11-4 (10 µg/ml) showed upregulation of RUNX2 and OCN at 3 days, with downregulation of ALP at 3 and 7d.

CONCLUSION

P11-4 did not affect cell viability, induced mineral deposition in SCAPs, and upregulated the expression of RUNX2 and OCN genes at 3 days, while downregulating ALP expression at 3 and 7 days.

CLINICAL SIGNIFICANCE

Based on the results obtained in this study it can be stated that self-assembling peptide P11-4 is a potential candidate to induce mineralization on dental stem cells for regenerative purposes and also for a clinical use as a capping agent without compromising the cells health.

Hydrophilic surface-modified 3D printed flexible scaffolds with high ceramic particle concentrations for immunopolarization-regulation and bone regeneration

Bioceramic scaffolds used in bone tissue engineering suffer from a low concentration of ceramic particles (<50 wt%), because the high concentration of ceramic particles increases the brittleness of the composite. 3D printed flexible PCL/HA scaffolds with high ceramic particle concentrations (84 wt%) were successfully fabricated in this study. However, the hydrophobicity of PCL weakens the composite scaffold hydrophilicity, which may limit the osteogenic ability to some extent. Thus, as a less time-consuming, less labour intensive, and more cost-effective treatment method, alkali treatment (AT) was employed to modify the surface hydrophilicity of the PCL/HA scaffold, and its regulation of immune responses and bone regeneration were investigated in vivo and in vitro. Initially, several concentrations of NaOH (0.5, 1, 1.5, 2, 2.5, and 5 mol L^-1) were employed in tests to determine the appropriate concentration for AT. Based on the comprehensive consideration of the results of mechanical experiments and hydrophilicity, 2 mol L^-1 and 2.5 mol L^-1 of NaOH were selected for further investigation in this study. The PCL/HA-AT-2 scaffold dramatically reduced foreign body reactions as compared to the PCL/HA and PCL/HA-AT-2.5 scaffolds, promoted macrophage polarization towards the M2 phenotype and enhanced new bone formation. The Wnt/β-catenin pathway might participate in the signal transduction underlying hydrophilic surface-modified 3D printed scaffold-regulated osteogenesis, according to the results of immunohistochemical staining. In conclusion, hydrophilic surface-modified 3D printed flexible scaffolds with high ceramic particle concentrations can regulate the immune reactions and macrophage polarization to promote bone regeneration, and the PCL/HA-AT-2 scaffold is a potential candidate for bone tissue repair.

Comparison between hydroxyapatite and polycaprolactone in inducing osteogenic differentiation and augmenting maxillary bone regeneration in rats

Background

The selection of appropriate scaffold plays an important role in ensuring the success of bone regeneration. The use of scaffolds with different materials and their effect on the osteogenic performance of cells is not well studied and this can affect the selection of suitable scaffolds for transplantation. Hence, this study aimed to investigate the comparative ability of two different synthetic scaffolds, mainly hydroxyapatite (HA) and polycaprolactone (PCL) scaffolds in promoting in vitro and in vivo bone regeneration.

Method

In vitro cell viability, morphology, and alkaline phosphatase (ALP) activity of MC3T3-E1 cells on HA and PCL scaffolds were determined in comparison to the accepted model outlined for two-dimensional systems. An in vivo study involving the transplantation of MC3T3-E1 cells with scaffolds into an artificial bone defect of 4 mm length and 1.5 mm depth in the rat's left maxilla was conducted. Three-dimensional analysis using micro-computed tomography (micro-CT), hematoxylin and eosin (H&E), and immunohistochemistry analyses evaluation were performed after six weeks of transplantation.

Results

MC3T3-E1 cells on the HA scaffold showed the highest cell viability. The cell viability on both scaffolds decreased after 14 days of culture, which reflects the dominant occurrence of osteoblast differentiation. An early sign of osteoblast differentiation can be detected on the PCL scaffold. However, cells on the HA scaffold showed more prominent results with intense mineralized nodules and significantly (p < 0.05) high levels of ALP activity with prolonged osteoblast induction. Micro-CT and H&E analyses confirmed the in vitro results with bone formation were significantly (p < 0.05) greater in HA scaffold and was supported by IHC analysis which confirmed stronger expression of osteogenic markers ALP and osteocalcin.

Conclusion

Different scaffold materials of HA and PCL might have influenced the bone regeneration ability of MC3T3-E1. Regardless, in vitro and in vivo bone regeneration was better in the HA scaffold which indicates its great potential for application in bone regeneration.

Investigating the Effects of Conditioned Media from Stem Cells of Human Exfoliated Deciduous Teeth on Dental Pulp Stem Cells

Pulp regeneration has recently attracted interest in modern dentistry. However, the success ratio of pulp regeneration is low due to the compromising potential of stem cells, such as their survival, migration, and odontoblastic differentiation. Stem cells from human exfoliated deciduous teeth (SHED) have been considered a promising tool for regenerative therapy due to their ability to secrete multiple factors that are essential for tissue regeneration, which is achieved by minimally invasive procedures with fewer ethical or legal concerns than those of other procedures. The aim of this study is to investigate the potency of SHED-derived conditioned media (SHED CM) on dental pulp stem cells (DPSCs), a major type of mesenchymal stem cells for dental pulp regeneration. Our results show the promotive efficiency of SHED CM on the proliferation, survival rate, and migration of DPSCs in a dose-dependent manner. Upregulation of odontoblast/osteogenic-related marker genes, such as ALP, DSPP, DMP1, OCN, and RUNX2, and enhanced mineral deposition of impaired DPSCs are also observed in the presence of SHED CM. The analysis of SHED CM found that a variety of cytokines and growth factors have positive effects on cell proliferation, migration, anti-apoptosis, and odontoblast/osteogenic differentiation. These findings suggest that SHED CM could provide some benefits to DPSCs in pulp regeneration.

Increased Osteogenic Activity of Dynamic Cultured Composite Bone Scaffolds: Characterization and In Vitro Study

PURPOSE

The purpose of this study was to develop and characterize beta-tricalcium phosphate (β-TCP)/polycaprolactone (PCL) scaffolds, with 2 different ratios (50/50% and 65/35%), using 3-dimensionally (3D) printed dissolvable molds, and to evaluate cellular growth and osteogenic differentiation of both groups seeded with porcine bone marrow stem cells (pBMSCs) under dynamic culture in vitro.

MATERIALS AND METHODS

Two different groups of scaffolds were produced: group 1 (n = 40) with a ratio (wt%) of 50/50% and group 2 (n = 40) with 65/35% of β-TCP/PCL. Physicochemical, morphological, and mechanical characterization of the scaffolds were performed. Scaffolds were seeded with pBMSCs and differentiated osteogenically in dynamic culture. Cell density, distribution, and viability were assessed. Osteogenic differentiation was examined through alkaline phosphatase (ALP) staining, immunofluorescence, and photospectrometry.

RESULTS

Osteogenic differentiated constructs showed homogenous and viable cell distribution. Cell density was significantly higher (P < .05) for 65/35% scaffolds at 10 days postseeding, whereas at 6 weeks, cell number equalized for both groups. ALP activity increased over time and was significantly higher (P < .05) for 65/35% scaffolds at 14 days postseeding.

CONCLUSIONS

The mechanical properties of the developed 65/35% scaffolds were within the range of natural trabecular bone. Moreover, the 65/35% scaffolds showed biological advantages, such as higher cell growth and higher ALP activity.

3D printed hybrid bone constructs of PCL and dental pulp stem cells loaded GelMA

Fabrication of scaffolds using polymers and then cell seeding is a routine protocol of tissue engineering applications. Synthetic polymers have adequate mechanical properties to substitute for some bone tissue, but they are generally hydrophobic and have no specific cell recognition sites, which leads to poor cell affinity and adhesion. Some natural polymers, have high cell affinity but are mechanically weak and do not have the strength required as a bone supporting material. In the present study, 3D printed hybrid scaffolds were fabricated using PCL and GelMA carrying dental pulp stem cells (DPSCs), which is printed in the gaps between the PCL struts. This cell loaded GelMA was shown to support osteoinductivity, while the PCL provided mechanical strength needed to mimic the bone tissue. 3D printed PCL/GelMA and GelMA scaffolds were highly stable during 21 days of incubation in PBS. The compressive moduli of the hybrid scaffolds were in the range of the compressive moduli of trabecular bone. DPSCs were homogeneously distributed throughout the entire hydrogel component and exhibited high cell viability in both scaffolds during 21 days of incubation. Upon osteogenic differentiation DPSCs expressed two key matrix proteins, osteopontin and osteocalcin. Alizarin red staining showed mineralized nodules, which demonstrates osteogenic differentiation of DPSCs within GelMA. This construct yielded a very high cell viability, osteogenic differentiation and mineralization comparable to cell culture without compromising mechanical strength suitable for bone tissue engineering applications. Thus, 3D printed, cell loaded PCL/GelMA hybrid scaffolds have a great potential for use in bone tissue engineering applications.

Comparative evaluation of osteogenic differentiation potential of stem cells derived from dental pulp and exfoliated deciduous teeth cultured over granular hydroxyapatite based scaffold

BACKGROUND

Mesenchymal stem cells isolated from the dental pulp of primary and permanent teeth can be differentiated into different cell types including osteoblasts. This study was conducted to compare the morphology and osteogenic potential of stem cells from exfoliated deciduous teeth (SHED) and dental pulp stem cells (DPSC) in granular hydroxyapatite scaffold (gHA). Preosteoblast cells (MC3T3-E1) were used as a control group.

METHODOLOGY

The expression of stemness markers for DPSC and SHED was evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR). Alkaline phosphatase assay was used to compare the osteoblastic differentiation of these cells (2D culture). Then, cells were seeded on the scaffold and incubated for 21 days. Morphology assessment using field emission scanning electron microscopy (FESEM) was done while osteogenic differentiation was detected using ALP assay (3D culture).

RESULTS

The morphology of cells was mononucleated, fibroblast-like shaped cells with extended cytoplasmic projection. In RT-PCR study, DPSC and SHED expressed GAPDH, CD73, CD105, and CD146 while negatively expressed CD11b, CD34 and CD45. FESEM results showed that by day 21, dental stem cells have a round like morphology which is the morphology of osteoblast as compared to day 7. The osteogenic potential using ALP assay was significantly increased (p < 0.01) in SHED as compared to DPSC and MC3T3-E1 in 2D and 3D cultures.

CONCLUSION

gHA scaffold is an optimal scaffold as it induced osteogenesis in vitro. Besides, SHED had the highest osteogenic potential making them a preferred candidate for tissue engineering in comparison with DPSC.

Shared Genetic and Epigenetic Mechanisms between the Osteogenic Differentiation of Dental Pulp Stem Cells and Bone Marrow Stem Cells

OBJECTIVE

To identify the shared genetic and epigenetic mechanisms between the osteogenic differentiation of dental pulp stem cells (DPSC) and bone marrow stem cells (BMSC).

MATERIALS AND METHODS

The profiling datasets of miRNA expression in the osteogenic differentiation of mesenchymal stem cells from the dental pulp (DPSC) and bone marrow (BMSC) were searched in the Gene Expression Omnibus (GEO) database. The differential expression analysis was performed to identify differentially expressed miRNAs (DEmiRNAs) dysregulated in DPSC and BMSC osteodifferentiation. The target genes of the DEmiRNAs that were dysregulated in DPSC and BMSC osteodifferentiation were identified, followed by the identification of the signaling pathways and biological processes (BPs) of these target genes. Accordingly, the DEmiRNA-transcription factor (TFs) network and the DEmiRNAs-small molecular drug network involved in the DPSC and BMSC osteodifferentiation were constructed.

RESULTS

16 dysregulated DEmiRNAs were found to be overlapped in the DPSC and BMSC osteodifferentiation, including 8 DEmiRNAs with a common expression pattern (8 upregulated DEmiRNAs (miR-101-3p, miR-143-3p, miR-145-3p/5p, miR-19a-3p, miR-34c-5p, miR-3607-3p, miR-378e, miR-671-3p, and miR-671-5p) and 1 downregulated DEmiRNA (miR-671-3p/5p)), as well as 8 DEmiRNAs with a different expression pattern (i.e., miR-1273g-3p, miR-146a-5p, miR-146b-5p, miR-337-3p, miR-382-3p, miR-4508, miR-4516, and miR-6087). Several signaling pathways (TNF, mTOR, Hippo, neutrophin, and pathways regulating pluripotency of stem cells), transcription factors (RUNX1, FOXA1, HIF1A, and MYC), and small molecule drugs (curcumin, docosahexaenoic acid (DHA), vitamin D3, arsenic trioxide, 5-fluorouracil (5-FU), and naringin) were identified as common regulators of both the DPSC and BMSC osteodifferentiation.

CONCLUSION

Common genetic and epigenetic mechanisms are involved in the osteodifferentiation of DPSCs and BMSCs.

3D-Printed Poly(ε-Caprolactone)/Hydroxyapatite Scaffolds Modified with Alkaline Hydrolysis Enhance Osteogenesis In Vitro

The 3D-printed bioactive ceramic incorporated Poly(ε-caprolactone) (PCL) scaffolds show great promise as synthetic bone graft substitutes. However, 3D-printed scaffolds still lack adequate surface properties for cells to be attached to them. In this study, we modified the surface characteristics of 3D-printed poly(ε-caprolactone)/hydroxyapatite scaffolds using O2 plasma and sodium hydroxide. The surface property of the alkaline hydrolyzed and O2 plasma-treated PCL/HA scaffolds were evaluated using field-emission scanning microscopy (FE-SEM), Alizarin Red S (ARS) staining, and water contact angle analysis, respectively. The in vitro behavior of the scaffolds was investigated using human dental pulp-derived stem cells (hDPSCs). Cell proliferation of hDPSCs on the scaffolds was evaluated via immunocytochemistry (ICC) and water-soluble tetrazolium salt (WST-1) assay. Osteogenic differentiation of hDPSCs on the scaffolds was further investigated using ARS staining and Western blot analysis. The result of this study shows that alkaline treatment is beneficial for exposing hydroxyapatite particles embedded in the scaffolds compared to O2 plasma treatment, which promotes cell proliferation and differentiation of hDPSCs.

Vitamin D3 and Dental Mesenchymal Stromal Cells

Vitamin D3 is a hormone involved in the regulation of bone metabolism, mineral homeostasis, and immune response. Almost all dental tissues contain resident mesenchymal stromal cells (MSCs), which are largely similar to bone marrow-derived MSCs. In this narrative review, we summarized the current findings concerning the physiological effects of vitamin D3 on dental MSCs. The existing literature suggests that dental MSCs possess the ability to convert vitamin D3 into 25(OH)D3 and subsequently to the biologically active 1,25(OH)2D3. The vitamin D3 metabolites 25(OH)D3 and 1,25(OH)2D3 stimulate osteogenic differentiation and diminish the inflammatory response of dental MSCs. In addition, 1,25(OH)2D3 influences the immunomodulatory properties of MSCs in different dental tissues. Thus, dental MSCs are both producers and targets of 1,25(OH)2D3 and might regulate the local vitamin D3-dependent processes in an autocrine/paracrine manner. The local vitamin D3 metabolism is assumed to play an essential role in the local physiological processes, but the mechanisms of its regulation in dental MSCs are mostly unknown. The alteration of the local vitamin D3 metabolism may unravel novel therapeutic modalities for the treatment of periodontitis as well as new strategies for dental tissue regeneration.

Effects of mineral trioxide aggregate, calcium hydroxide, biodentine and Emdogain on osteogenesis, Odontogenesis, angiogenesis and cell viability of dental pulp stem cells

BACKGROUND

Vital pulp therapy preserves and maintains the integrity and the health of dental pulp tissue that has been injured by trauma, caries or restorative procedures. The enhancement of cells viability and formation of reparative dentine and new blood vessels are vital determinants of the success of direct pulp capping. Therefore, the aims of this study was to evaluate and compare the in vitro osteogenic, odontogenic and angiogenic effects of mineral trioxide aggregate (MTA), calcium hydroxide [Ca(OH)₂], Biodentine and Emdogain on dental pulp stem cells (DPSCs) and examine the effects of the tested materials on cell viability.

METHODS

DPSCs were treated with MTA, Ca(OH)₂, Biodentine or Emdogain. Untreated cells were used as control. The cell viability was measured by MTT assay on day 3. Real-Time PCR with SYBR green was used to quantify the gene expression levels of osteogenic markers (alkaline phosphatase and osteopontin), odontogenic marker (dentin sialophosphoprotein) and angiogenic factor (vascular endothelial growth factor) on day 7 and day 14.

RESULTS

All capping materials showed variable cytotoxicity against DPSCs (77% for Emdogain, 53% for MTA, 26% for Biodentine and 16% for Ca(OH)₂ compared to control (P value < 0.0001). Osteopontin (OPN) and dentin sialophosphoprotein (DSPP) gene expression was increased by all four materials. However, alkaline phosphatase (ALP) was upregulated by all materials except Emdogain. Vascular endothelial growth factor (VEGF) expression was upregulated by all four tested materials except Ca(OH)₂.

CONCLUSIONS

Our results suggest MTA, Biodentine and Emdogain exhibit similar attributes and may score better than Ca(OH)₂. Emdogain could be a promising alternative to MTA and Biodentine in enhancing pulp repair capacity following dental pulp injury. However, further future research is required to assess the clinical outcomes and compare it with the in vitro findings.

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.

In vitro response of dental pulp stem cells in 3D scaffolds: A regenerative bone material

Three-dimensional-porous scaffolds of bone graft substitutes play a critical role in both cell targeting and transplantation strategies. These scaffolds provide surfaces that facilitate the response of stem cells related to attachment, survival, migration, proliferation, and differentiation.

Objective

The aim of this study was to evaluate the in vitro behavior of human dental pulp mesenchymal stem cells cultured on scaffolds of polylactic/polyglycolic acid with and without hydroxyapatite.

Method

We performed an in vitro experimental study using dental pulp stem cells obtained from samples of premolars, molars. The cells were cultured on scaffolds with osteogenic differentiation medium. Cell proliferation, adhesion and cell differentiation to an osteoblastic linage in the biomaterial were evaluated at three different time points: 7, 15 and 30 days. Each experiment was performed in triplicate. Analysis of the data was performed with the Split Plot block and MANOVA model.

Results

The differentiation capability of hDPSCs towards the osteoblast lineage was better in the scaffold of PLGA/HA at 7, 15 and 30 days, as indicated by the high expression of osteogenic markers RUNX2, ALP, OPN and COL-I, compared with differentiation in the PLGA scaffold. No statistically significant differences were found in cell adhesion between the two types of scaffolds.

Conclusion

The PLGA/HA scaffold provided better physical and chemical signals, as judged by the ability of dental pulp stem cells to adhere, proliferate and differentiate toward the osteogenic lineage.

Dental pulp stem cells and osteogenesis: an update

Dental pulp stem cells constitute an attractive source of multipotent mesenchymal stem cells owing to their high proliferation rate and multilineage differentiation potential. Osteogenesis is initiated by osteoblasts, which originate from mesenchymal stem cells. These cells express specific surface antigens that disappear gradually during osteodifferentiation. In parallel, the appearance of characteristic markers, including alkaline phosphatase, collagen type I, osteocalcin and osteopontin characterize the osteoblastic phenotype of dental pulp stem cells. This review will shed the light on the osteogenic differentiation potential of dental pulp stem cells and explore the culture medium components, and markers associated with osteodifferentiation of these cells.

Pulp Regeneration Concepts for Nonvital Teeth: From Tissue Engineering to Clinical Approaches

Following the basis of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontic has emerged as a new concept of dental treatment. Clinical procedures have been proposed by endodontic practitioners willing to promote regenerative therapy. Preserving pulp vitality was a first approach. Later procedures aimed to regenerate a vascularized pulp in necrotic root canals. However, there is still no protocol allowing an effective regeneration of necrotic pulp tissue either in immature or mature teeth. This review explores in vitro and preclinical concepts developed during the last decade, especially the potential use of stem cells, bioactive molecules, and scaffolds, and makes a comparison with the goals achieved so far in clinical practice. Regeneration of pulp-like tissue has been shown in various experimental conditions. However, the appropriate techniques are currently in a developmental stage. The ideal combination of scaffolds and growth factors to obtain a complete regeneration of the pulp-dentin complex is still unknown. The use of stem cells, especially from pulp origin, sounds promising for pulp regeneration therapy, but it has not been applied so far for clinical endodontics, in case of necrotic teeth. The gap observed between the hope raised from in vitro experiments and the reality of endodontic treatments suggests that clinical success may be achieved without external stem cell application. Therefore, procedures using the concept of cell homing, through evoked bleeding that permit to recreate a living tissue that mimics the original pulp has been proposed. Perspectives for pulp tissue engineering in the near future include a better control of clinical parameters and pragmatic approach of the experimental results (autologous stem cells from cell homing, controlled release of growth factors). In the coming years, this therapeutic strategy will probably become a clinical reality, even for mature necrotic teeth.

Dental Stem Cells Harvested from Third Molars Combined with Bioactive Glass Can Induce Signs of Bone Formation In Vitro

Objectives

The aim of this study was to assess the interaction of a bioactive glass scaffold with cells derived from dental pulp, dental follicle and periodontal ligament.

Material and Methods

Impacted third molars were surgically removed from three young donors. Cells from the dental pulp, follicle and periodontal ligament tissues were isolated and expanded. Different cell populations were characterised using specific CD markers. Expanded pulp, follicle and periodontal cells were then seeded onto bioactive glass scaffolds and cultured in osteogenic medium or basic medium. Cell attachment, viability, proliferation and alkaline phosphatase activity were assessed.

Results

This study revealed good biocompatibility of the specific bioactive glass configuration tested and the osteogenic induction of cells derived from dental pulp, dental follicle and periodontal ligament. Osteogenic medium seemed to increase the differentiation pattern and dental pulp stem cells showed the most positive results compared to periodontal ligament and dental follicle stem cells.

Conclusions

Dental pulp stem cells combined with a bioactive glass scaffold and exposed to osteogenic medium in vitro represent a promising combination for future study of hard tissue regeneration in the cranio-maxillofacial skeleton.

Amenable epigenetic traits of dental pulp stem cells underlie high capability of xeno-free episomal reprogramming

BACKGROUND

While a shift towards non-viral and animal component-free methods of generating induced pluripotent stem (iPS) cells is preferred for safer clinical applications, there is still a shortage of reliable cell sources and protocols for efficient reprogramming.

METHODS

Here, we show a robust episomal and xeno-free reprogramming strategy for human iPS generation from dental pulp stem cells (DPSCs) which renders good efficiency (0.19%) over a short time frame (13-18 days).

RESULTS

The robustness of DPSCs as starting cells for iPS induction is found due to their exceptional inherent stemness properties, developmental origin from neural crest cells, specification for tissue commitment, and differentiation capability. To investigate the epigenetic basis for the high reprogramming efficiency of DPSCs, we performed genome-wide DNA methylation analysis and found that the epigenetic signature of DPSCs associated with pluripotent, developmental, and ecto-mesenchymal genes is relatively close to that of iPS and embryonic stem (ES) cells. Among these genes, it is found that overexpression of PAX9 and knockdown of HERV-FRD improved the efficiencies of iPS generation.

CONCLUSION

In conclusion, our study provides underlying epigenetic mechanisms that establish a robust platform for efficient generation of iPS cells from DPSCs, facilitating industrial and clinical use of iPS technology for therapeutic needs.

Dental Stem Cells in Bone Tissue Engineering: Current Overview and Challenges

The treatment of bone that is impaired due to disease, trauma or tumor resection creates a challenge for both clinicians and researchers. Critical size bone defects are conventionally treated with autografts which are associated with risks such as donor site morbidity and limitations like donor shortage. Bone tissue engineering has become a promising area for the management of critical size bone defects by the employment of biocompatible materials and the discovery of novel stem cell sources. Mesenchymal stem cells (MSCs) can be isolated with ease from various dental tissues including dental pulp stem cells, stem cells from apical papilla, dental follicle stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, gingival stem cells and tooth germ derived stem cells. Outcomes of dental MSC mediated bone tissue engineering is explored in various in vivo and in vitro preclinical studies. However, there are still obscurities regarding the mechanisms underlying in MSC mediated bone regeneration and challenges in applications of dental stem cells. In this review, we summarized dental stem cell sources and their characterizations, along with currently used biomaterials for cell delivery and future perspectives for dental MSCs in the field of bone tissue engineering. Further efforts are necessary before moving to clinical trials for future applications.

Bone biomaterials and interactions with stem cells

Bone biomaterials play a vital role in bone repair by providing the necessary substrate for cell adhesion, proliferation, and differentiation and by modulating cell activity and function. In past decades, extensive efforts have been devoted to developing bone biomaterials with a focus on the following issues: (1) developing ideal biomaterials with a combination of suitable biological and mechanical properties; (2) constructing a cell microenvironment with pores ranging in size from nanoscale to submicro- and microscale; and (3) inducing the oriented differentiation of stem cells for artificial-to-biological transformation. Here we present a comprehensive review of the state of the art of bone biomaterials and their interactions with stem cells. Typical bone biomaterials that have been developed, including bioactive ceramics, biodegradable polymers, and biodegradable metals, are reviewed, with an emphasis on their characteristics and applications. The necessary porous structure of bone biomaterials for the cell microenvironment is discussed, along with the corresponding fabrication methods. Additionally, the promising seed stem cells for bone repair are summarized, and their interaction mechanisms with bone biomaterials are discussed in detail. Special attention has been paid to the signaling pathways involved in the focal adhesion and osteogenic differentiation of stem cells on bone biomaterials. Finally, achievements regarding bone biomaterials are summarized, and future research directions are proposed.

Collagenous matrix supported by a 3D-printed scaffold for osteogenic differentiation of dental pulp cells

OBJECTIVE

A systematic characterization of hybrid scaffolds, fabricated based on combinatorial additive manufacturing technique and freeze-drying method, is presented as a new platform for osteoblastic differentiation of dental pulp cells (DPCs).

METHODS

The scaffolds were consisted of a collagenous matrix embedded in a 3D-printed beta-tricalcium phosphate (β-TCP) as the mineral phase. The developed construct design was intended to achieve mechanical robustness owing to 3D-printed β-TCP scaffold, and biologically active 3D cell culture matrix pertaining to the Collagen extracellular matrix. The β-TCP precursor formulations were investigated for their flow-ability at various temperatures, which optimized for fabrication of 3D printed scaffolds with interconnected porosity. The hybrid constructs were characterized by 3D laser scanning microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and compressive strength testing.

RESULTS

The in vitro characterization of scaffolds revealed that the hybrid β-TCP/Collagen constructs offer superior DPCs proliferation and alkaline phosphatase (ALP) activity compared to the 3D-printed β-TCP scaffold over three weeks. Moreover, it was found that the incorporation of TCP into the Collagen matrix improves the ALP activity.

SIGNIFICANCE

The presented results converge to suggest the developed 3D-printed β-TCP/Collagen hybrid constructs as a new platform for osteoblastic differentiation of DPCs for craniomaxillofacial bone regeneration.

Zinc bioglasses regulate mineralization in human dental pulp stem cells

OBJECTIVE

A promising strategy in regenerative endodontics is the combination of human dental pulp stem cells (hDPSCs) with an appropriate biomaterial substrate. The effects of zinc and zinc containing bioactive glasses (ZnBGs) on hDPSCs have been characterized in this study.

METHODS

ZnBGs were designed and produced. Then the odontogenic differentiation and mineralization potential of hDPSCs upon ZnBGs treatment were investigated.

RESULTS

Free Zn ions (0-5ppm) enhanced proliferation and alkaline phosphatase (ALP) activity of hDPSCs. Further, ZnBGs conditioned medium (ZnBG-CM) increased the production and secretion of odontogenic markers: dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP-1). In addition, we identified that mRNA expression of the osteogenic markers RUNX2, OCN, BSP, BMP-2, MEPE and ON was increased following treatment with ZnBG-CM. Long term treatment with ZnBG-CM increases the formation rate of mineralized nodules (similar to hydroxyapatite, Ca:P=1.6), as confirmed by scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX). Lastly, the administration of ZnBG-CM induces VEGF expression.

SIGNIFICANCE

These findings implicate that ZnBG would be beneficial in regenerative endodontics and could influence the way present Zn containing clinical products are used.

Vitamin D Effects on Osteoblastic Differentiation of Mesenchymal Stem Cells from Dental Tissues

1α,25-Dihydroxyvitamin D₃ (1,25(OH)₂D₃), the active metabolite of vitamin D (Vit D), increases intestinal absorption of calcium and phosphate, maintaining a correct balance of bone remodeling. Vit D has an anabolic effect on the skeletal system and is key in promoting osteoblastic differentiation of human Mesenchymal Stem Cells (hMSCs) from bone marrow. MSCs can be also isolated from the immature form of the tooth, the dental bud: Dental Bud Stem Cells (DBSCs) are adult stem cells that can effectively undergo osteoblastic differentiation. In this work we investigated the effect of Vit D on DBSCs differentiation into osteoblasts. Our data demonstrate that DBSCs, cultured in an opportune osteogenic medium, differentiate into osteoblast-like cells; Vit D treatment stimulates their osteoblastic features, increasing the expression of typical markers of osteoblastogenesis like RUNX2 and Collagen I (Coll I) and, in a more important way, determining a higher production of mineralized matrix nodules.

Magnetic nanofiber scaffold-induced stimulation of odontogenesis and pro-angiogenesis of human dental pulp cells through Wnt/MAPK/NF-κB pathways

OBJECTIVE

Magnetic biomaterials have recently gained great attention due to their some intriguing cell and tissue responses. However, little attention has been given to the fields of dental tissue regeneration. In this sense, we aim to investigate the effects of magnetic nanofiber scaffolds on the human dental pulp cell (HDPC) behaviors and to elucidate the underlying signaling mechanisms in the events.

METHODS

Magnetic nanofiber scaffolds incorporating magnetic nanoparticles at varying contents were prepared into nanofibrous matrices to cultivate cells. Cell growth by MTS assay, odontoblastic differentiation by alkaline phosphatase (ALP) activity, mineralization, and the mRNA expression of differentiation-related genes of HDPCs, in vitro angiogenesis by migration and capillary tube formation in endothelial cells on the conditioned medium obtained from HDPSCs in the presence or absence of scaffolds. Western blot analysis and confocal immunofluorescene were used to asses signaling pathways.

RESULTS

The growth of HDPCs was significantly enhanced on the magnetic scaffolds with respect to the non-magnetic counterpart. The odontogenic differentiation of cells was significantly up-regulated by the culture with magnetic scaffolds. Furthermore, the magnetic scaffolds promoted the HDPC-induced angiogenesis of endothelial cells. The expression of signaling molecules, Wnt3a, phosphorylated GSK-3β and nuclear β-catenin, was substantially stimulated by the magnetic scaffolds; in parallel, the MAPK and NF-κB were highly activated when cultured on the magnetic nanofiber scaffolds.

SIGNIFICANCE

This study is the first to demonstrate that magnetic nanofiber scaffolds stimulate HDPCs in the events of growth, odontogenic differentiation, and pro-angiogenesis, and the findings imply the novel scaffolds can be potentially useful as dentin-pulp regenerative matrices.

Scaffolds in regenerative endodontics: A review

Root canal therapy has enabled us to save numerous teeth over the years. The most desired outcome of endodontic treatment would be when diseased or nonvital pulp is replaced with healthy pulp tissue that would revitalize the teeth through regenerative endodontics. ‘A search was conducted using the Pubmed and MEDLINE databases for articles with the criteria ‘Platelet rich plasma’, ‘Platelet rich fibrin’, ‘Stem cells’, ‘Natural and artificial scaffolds’ from 1982–2015’. Tissues are organized as three-dimensional structures, and appropriate scaffolding is necessary to provide a spatially correct position of cell location and regulate differentiation, proliferation, or metabolism of the stem cells. Extracellular matrix molecules control the differentiation of stem cells, and an appropriate scaffold might selectively bind and localize cells, contain growth factors, and undergo biodegradation over time. Different scaffolds facilitate the regeneration of different tissues. To ensure a successful regenerative procedure, it is essential to have a thorough and precise knowledge about the suitable scaffold for the required tissue. This article gives a review on the different scaffolds providing an insight into the new developmental approaches on the horizon.

Magnetic Nanocomposite Scaffold-Induced Stimulation of Migration and Odontogenesis of Human Dental Pulp Cells through Integrin Signaling Pathways

Magnetism is an intriguing physical cue that can alter the behaviors of a broad range of cells. Nanocomposite scaffolds that exhibit magnetic properties are thus considered useful 3D matrix for culture of cells and their fate control in repair and regeneration processes. Here we produced magnetic nanocomposite scaffolds made of magnetite nanoparticles (MNPs) and polycaprolactone (PCL), and the effects of the scaffolds on the adhesion, growth, migration and odontogenic differentiation of human dental pulp cells (HDPCs) were investigated. Furthermore, the associated signaling pathways were examined in order to elucidate the molecular mechanisms in the cellular events. The magnetic scaffolds incorporated with MNPs at varying concentrations (up to 10%wt) supported cellular adhesion and multiplication over 2 weeks, showing good viability. The cellular constructs in the nanocomposite scaffolds played significant roles in the stimulation of adhesion, migration and odontogenesis of HDPCs. Cells were shown to adhere to substantially higher number when affected by the magnetic scaffolds. Cell migration tested by in vitro wound closure model was significantly enhanced by the magnetic scaffolds. Furthermore, odontogenic differentiation of HDPCs, as assessed by the alkaline phosphatase activity, mRNA expressions of odontogenic markers (DMP-1, DSPP,osteocalcin, and ostepontin), and alizarin red staining, was significantly stimulated by the magnetic scaffolds. Signal transduction was analyzed by RT-PCR, Western blotting, and confocal microscopy. The magnetic scaffolds upregulated the integrin subunits (α1, α2, β1 and β3) and activated downstream pathways, such as FAK, paxillin, p38, ERK MAPK, and NF-κB. The current study reports for the first time the significant impact of magnetic scaffolds in stimulating HDPC behaviors, including cell migration and odontogenesis, implying the potential usefulness of the magnetic scaffolds for dentin-pulp tissue engineering.

Wnt Acts as a Prosurvival Signal to Enhance Dentin Regeneration

Wnt proteins are lipid-modified, short-range signals that control stem cell self-renewal and tissue regeneration. We identified a population of Wnt responsive cells in the pulp cavity, characterized their function, and then created a pulp injury. The repair response was evaluated over time using molecular, cellular, and quantitative assays. We tested how healing was impacted by wound environments in which Wnt signaling was amplified. We found that a Wnt-amplified environment was associated with superior pulp healing. Although cell death was still rampant, the number of cells undergoing apoptosis was significantly reduced. This resulted in significantly better survival of injured pulp cells, and resulted in the formation of more tertiary dentin. We engineered a liposome-reconstituted form of WNT3A then tested whether this biomimetic compound could activate cells in the injured tooth pulp and stimulate dentin regeneration. Pulp cells responded to the elevated Wnt stimulus by differentiating into secretory odontoblasts. Thus, transiently amplifying the body's natural Wnt response resulted in improved pulp vitality. These data have direct clinical implications for treating dental caries, the most prevalent disease affecting mankind.

Osteogenic Potential of Dental Mesenchymal Stem Cells in Preclinical Studies: A Systematic Review Using Modified ARRIVE and CONSORT Guidelines

Background and Objective. Dental stem cell-based tissue engineered constructs are emerging as a promising alternative to autologous bone transfer for treating bone defects. The purpose of this review is to systematically assess the preclinical in vivo and in vitro studies which have evaluated the efficacy of dental stem cells on bone regeneration. Methods. A literature search was conducted in Ovid Medline, Embase, PubMed, and Web of Science up to October 2014. Implantation of dental stem cells in animal models for evaluating bone regeneration and/or in vitro studies demonstrating osteogenic potential of dental stem cells were included. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used to ensure the quality of the search. Modified ARRIVE (Animal research: reporting in invivo experiments) and CONSORT (Consolidated reporting of trials) were used to critically analyze the selected studies. Results. From 1914 citations, 207 full-text articles were screened and 137 studies were included in this review. Because of the heterogeneity observed in the studies selected, meta-analysis was not possible. Conclusion. Both in vivo and in vitro studies indicate the potential use of dental stem cells in bone regeneration. However well-designed randomized animal trials are needed before moving into clinical trials.

A First Step in De Novo Synthesis of a Living Pulp Tissue Replacement Using Dental Pulp MSCs and Tissue Growth Factors, Encapsulated within a Bioinspired Alginate Hydrogel

INTRODUCTION

A living, self-supporting pulp tissue replacement in vitro and for transplantation is an attractive yet unmet bioengineering challenge. Our aim is to create 3-dimensional alginate-based microenvironments that replicate the shape of gutta-percha and comprise key elements for the proliferation of progenitor cells and the release of growth factors.

METHODS

An RGD-bearing alginate framework was used to encapsulate dental pulp stem cells and human umbilical vein endothelial cells in a ratio of 1:1. The alginate hydrogel also retained and delivered 2 key growth factors, vascular endothelial growth factor-121 and fibroblast growth factor, in a sufficient amount to induce proliferation. A method was then devised to replicate the shape of gutta-percha using RGD alginate within a custom-made mold of thermoresponsive N-isopropylacrylamide. Plugs of alginate containing different permutations of growth factor-based encapsulates were tested and evaluated for viability, proliferation, and release kinetics between 1 and 14 days.

RESULTS

According to scanning electron microscopic and confocal microscopic observations, the encapsulated human endothelial cells and dental pulp stem cell distribution were frequent and extensive throughout the length of the construct. There were also high levels of viability in all test environments. Furthermore, cell proliferation was higher in the growth factor-based groups. Growth factor release kinetics also showed significant differences between them. Interestingly, the combination of vascular endothelial growth factor and fibroblast growth factor synergize to significantly up-regulate cell proliferation.

CONCLUSIONS

RGD-alginate scaffolds can be fabricated into shapes to fill the pulp space by simple templating. The addition of dual growth factors to cocultures of stem cells within RGD-alginate scaffolds led to the creation of microenvironments that significantly enhance the proliferation of dental pulp stem cell/human umbilical vein endothelial cell combinations.

Effects of bioactive cements incorporating zinc-bioglass nanoparticles on odontogenic and angiogenic potential of human dental pulp cells

Background

The objective of this study was to investigate the effects of bioactive calcium phosphate cements (CPC, α-tricalcium phosphate-based) incorporating zinc-bioglass (ZnBG) on the odontogenic differentiation and angiogenesis of human dental pulp cells (HDPCs).

Methods

BGs with varying concentrations of Zn (0, 2.5 and 5%) were produced via a sol-gel process. The proliferation of HDPCs on CPC/BGs was determined by MTS assay. Alizarin red staining, RT-PCR, and ALP activity were used to assess odontogenic differentiation, and western blot analysis was used to asses signaling pathways. In vitro angiogenesis was examined via mRNA expression of angiogenic genes and tubule formation.

Results

All cement formulations showed no cytotoxicity. The CPCs with ZnBG showed increased ALP activity, enhanced formation of mineralized nodules, and upregulated mRNA expression of DMP-1, DSPP, Runx2, and osterix in a time- and dose-dependent manner, relative to CPCs without Zn. ZnBG upregulated integrins α1, α2, β1, and β3 and activated integrin downstream signal pathways, such as p-FAK, p-Akt, p-paxillin, RhoA, MAPK, and NF-κB, as well as canonical and non-canonical Wnt signaling. In addition, ZnBG upregulated VEGF mRNA in HDPCs and increased the tubular structure in endothelial cells.

Conclusions

Our results demonstrate that ZnBG incorporated within CPCs activates odontogenic differentiation and promotes angiogenesis in vitro through integrin, Wnt, MAPK, and NF-κB pathways. Thus, CPCs incorporating ZnBG are promising matrices in tissue engineering to stimulate endodontic regeneration.

Odontogenic stimulation of human dental pulp cells with bioactive nanocomposite fiber

The aim of the present study was to investigate the effects of a composite nanofibrous matrix made of biopolymer blend polycaprolactone-gelatin (BP) and mesoporous bioactive glass nanoparticles (BGNs) on the odontogenic differentiation of human dental pulp cells (HDPCs). BGN-BP nanomatrices, with BGN content of up to 20 wt%, were produced via electrospinning. The differentiation of the HDPCs was evaluated by using an ALP activity assay, calcified nodule formation, and mRNA expression for markers. Integrin and its underlying signal pathways were assessed via reverse transcriptase-polymerase chain reaction and Western blot analysis. Although cell growth and attachment on the BGN-BP nanomatrix was similar to that on BP, ALP activity, mineralized nodule formation, and mRNA, expressions involving ALP, osteocalcin, osteopontin, dentin sialophosphoprotein, and dentin matrix protein-1 were greater on BGN-BP. BGN-BP upregulated the key adhesion receptors (integrin components α1, α2, α5, and β1) and activated integrin downstream pathways, such as phosphorylated-focal adhesion kinase (p-FAK), and p-paxillin. In addition, BGN-BP activated BMP receptors, BMP-2 mRNA, and p-Smad 1/5/8, and such activation was blocked by the BMP antagonist, noggin. Furthermore, BGN-BP induced phosphorylation of extracellular signal-regulated kinase, protein kinase 38, and c-Jun-N-terminal kinase mitogen-activated protein kinases and activated expression of the transcription factors Runx2 and Osterix in HDPCs. Collectively, the results indicated for the first time that a BGN-BP composite nanomatrix promoted odontogenic differentiation of HDPCs through the integrin, BMP, and mitogen-activated protein kinases signaling pathway. Moreover, the nanomatrix is considered to be promising scaffolds for the culture of HDPCs and dental tissue engineering.

A novel therapeutic design of microporous-structured biopolymer scaffolds for drug loading and delivery

Three-dimensional (3-D) open-channeled scaffolds of biopolymers are a promising candidate matrix for tissue engineering. When scaffolds have the capacity to deliver bioactive molecules the potential for tissue regeneration should be greatly enhanced. In order to improve drug-delivery capacity, we exploit 3-D poly(lactic acid) (PLA) scaffolds by creating microporosity within the scaffold network. Macroporous channeled PLA with a controlled pore configuration was obtained by a robotic dispensing technique. In particular, a room temperature ionic liquid (RTIL) bearing hydrophilic counter-anions, such as OTf and Cl, was introduced to the biopolymer solution at varying ratios. The RTIL-biopolymer slurry was homogenized by ultrasonication, and then solidified through the robotic dispensing process, during which the biopolymer and RTIL formed a bicontinuous interpenetrating network. After ethanol wash-out treatment the RTIL was completely removed to leave highly microporous open channels throughout the PLA network. The resultant pore size was observed to be a few micrometers (average 2.43 μm) and microporosity was determined to be ∼ 70%. The microporous surface was also shown to favor initial cell adhesion, stimulating cell anchorage on the microporous structure. Furthermore, in vivo tissue responses assessed in rat subcutaneous tissue revealed good tissue compatibility, with minimal inflammatory reactions, while gathering a larger population of fibroblastic cells than the non-microporous scaffolds, and even facilitating invasion of the cells within the microporous structure. The efficacy of the micropore networks generated within the 3-D scaffolds in loading and releasing therapeutic molecules was addressed using antibiotic sodium ampicillin and protein cytochrome C as model drugs. The microporous scaffolds exhibited significantly enhanced drug loading capacity: 4-5 times increase in ampicillin and 9-10 times increase in cytochrome C compared to the non-microporous scaffolds. The release of ampicillin loaded within the microporous scaffolds was initially fast (∼ 85% for 1 week), and was then slowed down, showing a continual release up to a month. On the other hand, cytochrome C was shown to release in a highly sustainable manner over a month, without showing an initial burst release effect. This study provides a novel insight into the generation of 3-D biopolymer scaffolds with high performance in loading and delivery of biomolecules, facilitated by the creation of microporous channels through the scaffold network. The capacity to support tissue cells while in situ delivering drug molecules makes the current scaffolds potentially useful for therapeutic tissue engineering.

A novel in vivo platform for studying alveolar bone regeneration in rat

Alveolar bone regeneration is a significant challenge in dental implantation. Novel biomaterials and tissue-engineered constructs are under extensive development and awaiting in vivo animal tests to find clinical endpoint. Here, we establish a novel in vivo model, modifying gingivoperiosteoplasty in rat for the alveolar bone regeneration. Rat premaxillary bone defects were filled with silk scaffold or remained empty during the implantation period (up to 6 weeks), and harvested samples were analyzed by micro-computed tomography and histopathology. Empty defects showed increased but limited new bone formation with increasing implantation period. In defects implanted with silk sponge, the bone formation was significantly greater than that of empty defect, indicating an effective role of silk scaffold in the defect model. The modified premaxillary defect model in rat is simple to perform, while mimicking the clinical conditions, finding usefulness for the development of biomaterials and tissue-engineered constructs targeting alveolar bone regeneration in dental implantation.

Gelatin-apatite bone mimetic co-precipitates incorporated within biopolymer matrix to improve mechanical and biological properties useful for hard tissue repair

Synthetic biopolymers are commonly used for the repair and regeneration of damaged tissues. Specifically targeting bone, the composite approach of utilizing inorganic components is considered promising in terms of improving mechanical and biological properties. We developed gelatin-apatite co-precipitates which mimic the native bone matrix composition within poly(lactide-co-caprolactone) (PLCL). Ionic reaction of calcium and phosphate with gelatin molecules enabled the co-precipitate formation of gelatin-apatite nanocrystals at varying ratios. The gelatin-apatite precipitates formed were carbonated apatite in nature, and were homogeneously distributed within the gelatin matrix. The incorporation of gelatin-apatite significantly improved the mechanical properties, including tensile strength, elastic modulus and elongation at break, and the improvement was more pronounced as the apatite content increased. Of note, the tensile strength increased to as high as 45 MPa (a four-fold increase vs. PLCL), the elastic modulus was increased up to 1500 MPa (a five-fold increase vs. PLCL), and the elongation rate was ∼240% (twice vs. PLCL). These results support the strengthening role of the gelatin-apatite precipitates within PLCL. The gelatin-apatite addition considerably enhanced the water affinity and the acellular mineral-forming ability in vitro in simulated body fluid; moreover, it stimulated cell proliferation and osteogenic differentiation. Taken together, the GAp-PLCL nanocomposite composition is considered to have excellent mechanical and biological properties, which hold great potential for use as bone regenerative matrices.