Yanmei Dong

Odontogenic differentiation and dentin formation of dental pulp cells under nanobioactive glass induction.

Bioactive glass (BG) has been widely used in bone regeneration; however, reports on the biological effects of BG on dental pulp cells are rare. This study aims to investigate the effects of nanoscale BG (n-BG) on odontogenic differentiation and dentin formation of dental pulp cells and to compare these effects with those of microscale BG (m-BG). Human dental pulp cells (hDPCs) from third molars were cultured directly with m-BG and n-BG in vitro. The cell proliferation increased at 0.1mgml(-1) BG, which also had a chemotactic effect on hDPCs. The mineralization capacity and expression of odontogenic-related proteins and genes (dentin sialophosphoprotein, dentin matrix protein 1 and collagen type I) of hDPCs were significantly up-regulated under BG induction, and were particularly higher in the n-BG group than in the control group. m-BG and n-BG combined with pulp tissues were transplanted into the dorsum of immunodeficient mice to observe their biological effects on dental pulp cells in vivo. A continuous layer of dentin-like tissue with uniform thickness, a well-organized dentinal tubule structure and polarizing odontoblast-like cells aligned along it was generated upon the n-BG layer, whereas some irregular sporadic osteodentin-like mineralized tissues were observed in the control group. This study reveals that BG, especially n-BG, induces the odontogenic differentiation and dentin formation of dental pulp cells and may serve as a potential material for pulp repair and dentin regeneration.

Evaluation of a bioceramic as a pulp capping agent in vitro and in vivo.

INTRODUCTION This study aims to investigate the effects of the bioceramic iRoot BP Plus (Innovative Bioceramix Inc, Vancouver, Canada) as a pulp capping agent in vitro and in vivo. METHODS In vitro, human dental pulp cells (hDPCs) were seeded into plates with the prepared iRoot BP Plus or mineral trioxide aggregate (MTA) packed in the bottom of different wells. The proliferation of hDPCs was determined using the 3,(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Meanwhile, 2 animal models of direct pulp capping and pulpotomy were applied in Wistar rats in vivo. The exposed pulps were capped with iRoot BP Plus or MTA. After 1 and 4 weeks, maxillary segments were obtained and prepared for histologic analysis. RESULTS hDPCs grew very well even in the place contacted with MTA or iRoot BP plus in vitro. MTA and iRoot BP Plus both enhanced the proliferation of hDPCs (P < .05). In vivo, results revealed that few inflammatory cells were present in the pulpal area corresponding to the pulp exposure. A slight layer of newly generated matrix was also observed next to MTA and iRoot BP Plus after 1 week. A complete reparative dentin bridge with polarizing odontoblastlike cells was detected in all specimens in the iRoot BP Plus group after 4 weeks. CONCLUSIONS iRoot BP Plus exhibited good biocompatibility to pulp tissue and induced the proliferation of dental pulp cells and the formation of reparative dentin bridge. iRoot BP plus may be used as a pulp capping material for vital pulp therapy.

The effect of submicron bioactive glass particles on in vitro osteogenesis

This study investigated the effects of novel submicron bioactive glass (sm-BG) particles on in vitro osteogenesis and compared them to those of microscale bioactive glass (m-BG) particles. The ability of sm-BG particles to generate precipitates on their surface in the presence of simulated body fluid (SBF) was examined, and the effect of sm-BG particles on in vitro osteogenesis was evaluated by culturing human osteoblast-like osteosarcoma (MG-63) cells on particle-coated plates. It was found that sm-BG induced formation of precipitates after incubation for 24 hours in SBF. Compared with m-BG, sm-BG particles better promoted MG-63 cell adhesion and they induced expression of the ALP, RUNX2 and COL1 genes at an earlier stage and to a greater degree. This study demonstrates that submicron bioactive glass particles possess a high capacity for precipitates formation in SBF and improved osteogenic properties when compared to microscale BG particles.

A novel nano-sized bioactive glass stimulates osteogenesis via the MAPK pathway

The aims of this study were to compare the osteogenic effects of a novel nano-sized bioactive glass (BG) and a traditional micron-sized BG, and to verify whether mitogen-activated protein kinases (MAPKs) are involved and play a part in BG’s osteoblast gene activation. It was found that the effect of a nano-sized BG on MAPK phosphorylation is better than the traditional 45S5 BG. We prepared extractions of the novel nano-sized 58S BG and traditional 45S5 BG and compared their effect on osteoblast-like cells’ (MG-63 cell) proliferation, osteogenic gene and protein expressions, matrix mineralization and MAPK activation. We further investigated the signal transducing effect of the MAPK pathway on the BG’s osteogenic gene activation. Our results showed that nano-58S extraction enhanced the MG-63 cells’ proliferation and osteogenic gene expressions of alkaline phosphatase (ALP), collagen type I (Col I), Runt-related transcription factor 2 (Runx2) and osteocalcin (OCN). The results of ELISA showed more Col I and OCN protein production in the BG groups than in the control group. Greater mineralized nodule formation was found in the nano-58S BG group using alizarin red S staining. We also found that nano-58S and 45S5 BG activated MAPKs, specifically the ERK and p38 pathways, using western blotting. After blocking the ERK or p38 pathway, real-time PCR showed the osteogenic gene activation induced by the BG extractions was inhibited. Blocking the ERK pathway induced a more obvious inhibitory effect on the genes’ normal expression and activation. The significance of this study is that we found that the ERK and p38 MAPK pathways are involved and play an important part in BG’s osteogenic gene activation. The effect of the nano-sized BG on MAPK phosphorylation, osteogenic gene activation, and osteoblast differentiation and mineralization is better than the traditional 45S5 BG.

Novel bioactive glass based injectable bone cement with improved osteoinductivity and its in vivo evaluation

Recently, more and more attention has been paid to the development of a new generation of injectable bone cements that are bioactive, biodegradable and are able to have appropriate mechanical properties for treatment of vertebral compression fractures (VCFs). In this study, a novel PSC/CS composite cement with high content of PSC (a phytic acid-derived bioactive glass) was prepared and evaluated in both vitro and vivo. The PSC/CS cement showed excellent injectability, good resistance to disintegration, radiopacity and suitable mechanical properties. The in vitro test showed that the cement was bioactive, biocompatible and could maintain its shape sustainably, which made it possible to provide a long-term mechanical support for bone regeneration. Radiography, microcomputed tomography and histology of critical sized rabbit femoral condyle defects implanted with the cements proved the resorption and osteoinductivity of the cement. Compared with the PMMA and CSPC, there were more osteocyte and trabeculae at the Bone-Cement interface in the group PSC/CS cement. The volume of the residual bone cement suggested that PSC/CS had certain ability of degradation and the resorption rate was much lower than that of the CSPC cement. Together, the results indicated that the cement was a promising bone cement to treat the VCFs.

Regeneration of dental–pulp complex-like tissue using phytic acid derived bioactive glasses

Phytic acid derived bioactive calcium phosphosilicate (PSC) glasses with a high phosphate content were synthesised by using non-toxic phytic acid as a phosphorus precursor. This study aimed to verify the effects of PSC on the odontogenic differentiation and dentin–pulp complex-like tissue regeneration of dental pulp cells (DPCs). Nitrogen adsorption, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, pH measurement, and inductively coupled plasma optical emission spectroscopy analyses were performed to characterise PSC. Classical 45S5 bioactive glasses (45S5) were used as positive control. Cell proliferation (1, 3, 5, 7 and 9 days), odontogenic-related gene expression levels (3 and 7 days) and mineralisation ability (21 days) of human DPCs (hDPCs) were evaluated with methylthiazol tetrazolium assay, real-time polymerase chain reaction and alizarin red staining after hDPCs from third molars were treated with PSC or 45S5 extractions. Rat molar crowns with pulp tissues covered by PSC or 45S5 were transplanted subcutaneously into nude mice for 2 and 6 weeks to demonstrate their biological effects in vivo. Results revealed that the specific surface area of PSC was larger than that of 45S5. The PSC also induced hydroxycarbonate apatite precipitation earlier than 45S5. pH was slightly increased when the amount and dissolution time of PSCs were increased. By comparison, pH was remarkably increased by 45S5. The amounts of Si and P ions released by PSC (0.1 mg mL−1) were larger than those released by 45S5. Cell proliferation, mRNA expression levels of dentin sialophosphoprotein, dentin matrix protein 1 and osteocalcin and mineralisation of hDPCs were also more strongly promoted by PSC than by 45S5. In vivo, the amount of induced typical dentin-like tissues with odontoblast-like cells generated on the interface between materials and pulp tissues was higher in PSC than in 45S5. Only collagen-like tissues were observed in groups without bioactive glasses. These findings suggested that PSC enhanced the odontogenic differentiation of DPCs and dentin–pulp complex-like tissue regeneration. The PSC might be a potential candidate for vital pulp preservation and regeneration of the dentin–pulp complex.