A study of enamel matrix proteins on differentiation of porcine bone marrow stromal cells into cementoblasts

Mesoporous Hydroxyapatite/Chitosan Loaded With Recombinant-Human Amelogenin Could Enhance Antibacterial Effect and Promote Periodontal Regeneration

The recovery of impaired periodontium is still a challenge to the treatment of periodontitis. This study was the first to apply the mesoporous hydroxyapatites/chitosan (mHA/CS) composite scaffold to periodontal regeneration. The aim of our study is to evaluate the biological effects of mesoporous hydroxyapatite/chitosan (mHA/CS) loaded with recombinant human amelogenin (rhAm) on periodontal regeneration. The physicochemical properties of mHA/CS scaffolds were examined by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. Then, the biological effects of the mHA/CS loaded with rhAm were evaluated, including antibacterial effect, controlled-release capacity, osteogenic and cementogenic effects in vitro and in vivo. The antibacterial effect was tested on 1.5 mg/mL CS; 3 mg/mL mHA; 2.25 mg/mL mHA/CS; 4.5 mg/mL mHA/CS and 20 μg/mL rhAm. Tryptic Soy Broth culture medium was used as a baseline control. Osteogenic effect of rhAm (20 μg/mL rhAm), mHA/CS (4.5 mg/mL mHA/CS), and mHA/CS-rhAm (4.5 mg/mL mHA/CS and 20 μg/mL rhAm) on human periodontal ligament cells (hPDLCs) was evaluated in osteogenic media. The hPDLCs treated either with osteogenic media or Dulbecco's modified Eagle's medium (DMEM) alone were used as the baseline control. In the animal model, 4-week-old nude mice (BALB/c) (n = 6) implanted with root slices subcutaneously were used to observe the cementogenic effect in vivo. The root slices were treated with rhAm (20 μg/mL rhAm), mHA/CS (4.5 mg/mL mHA/CS), and mHA/CS-rhAm (4.5 mg/mL mHA/CS and 20 μg/mL rhAm). The root slices treated with osteogenic medium alone were used as the baseline control. The analyses showed that the mHA/CS particles were 2 μm in diameter and had a uniform pore size. The mesoporous structure was 7 nm in diameter and its surface area was 33.95 m²/g. The scaffold exhibited antibacterial effects against Fusobacterium nucleatum and Porphyromonas gingivalis. The mHA/CS scaffold sustainably released rhAm. The mHA/CS loaded with 20 μg/mL rhAm upregulated ALP activity, the expression levels of osteogenesis-related genes and proteins in vitro. Additionally, it promoted the formation of cementum-like tissue in vivo. Our findings suggest that mHA/CS loaded with 20 μg/mL rhAm could inhibit the growth of periodontal pathogens and promote the formation of bone and cementum-like tissue.

MagT1 regulated the odontogenic differentiation of BMMSCs induced byTGC-CM via ERK signaling pathway

Background

Bone marrow mesenchymal stem cells (BMMSCs) are suitable cell sources for dental pulp regeneration, but the mechanism of BMMSCs differentiation into odontogenic lineage remains unknown. The aim of the present study was to reveal the role of magnesium transporter protein 1 (MagT1) and MAPK pathways in the odontogenic differentiation of BMMSCs.

Methods

The RNA sequencing (RNA-seq) was performed to explore the altered transcriptome of BMMSCs undergoing odontogenic differentiation induced by tooth germ cell-condition medium (TGC-CM). Pathway analysis was conducted to explore enriched pathways of the differential expression signature. Automated western blot, real-time PCR, shRNA lentivirus, and flow cytometry were used to detect the function of MagTl and MAPK pathway in odontogenic differentiation of BMMSCs.

Results

RNA-seq identified 622 differentially expressed genes associated with odontogenic differentiation of BMMSCs induced by TGC-CM, some of which were responsible for MAPK pathway. Consistently, we verified that TGC-CM induced odontogenic differentiation of BMMSCs through activating ERK/MAPK pathway, and the inactivation of ERK/MAPK pathway inhibited the odontogenic differentiation induced by TGC-CM. We also found MagT1 protein was significantly increased during odontogenic differentiation of BMMSCs induced by TGC-CMM, in accordance, MagT1 knockdown significantly decreased the extent of mineralized nodules and the protein levels of alkaline phosphatase (ALP), dentin matrix protein 1 (DMP-1), and dentin sialophosphoprotein (DSP). Flow cytometry showed that intracellular Mg²⁺ was significantly reduced in MagT1-knockdown BMMSCs, indicating the suppression of MagT1 inhibited odontogenic differentiation of BMMSCs by decreasing intracellular Mg²⁺. Finally, we performed RNA-seq to explore the altered transcriptome of MagT1-knockdown BMMSCs undergoing odontogenic differentiation and identified 281 differentially expressed genes, some of which were involved in MAPK pathway. Consistently, automated western blot analysis found the ERK/MAPK pathway was inhibited in MagT1-knockdown BMMSCs during odontogenic differentiation, indicating that suppression of MagT1 inhibited odontogenic differentiation of BMMSCs via ERK/MAPK pathway.

Conclusions

This study identified the significant alteration of transcriptome in BMMSCs undergoing odontogenic differentiation induced by TGC-CM. We clarified the pivotal role of MagT1 and ERK/MAPK pathway in odontogenic differentiation of BMMSCs, and suppression of MagT1 inhibited the odontogenic differentiation of BMMSCs by decreasing the intracellular Mg²⁺ and inactivating ERK/MAPK pathway.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1148-6) contains supplementary material, which is available to authorized users.

Enamel matrix proteins regulate hypoxia-induced cellular biobehavior and osteogenic differentiation in human periodontal ligament cells

Hypoxia is a crucial microenvironment for inflamed periodontal tissue and periodontal wound healing. Enamel matrix proteins (EMPs) potentially can promote the formation of new periodontium. The effects of EMPs on periodontal ligament cells under hypoxia, however, remain unclear. We investigated the effects of EMPs on cellular biobehavior and osteogenic differentiation of human periodontal ligament cells (hPDLCs) under hypoxia. Under cobalt chloride (CoCl₂)-induced hypoxia, cellular biobehavior of hPDLCs, including proliferation, attachment, spreading, and migration with or without EMPs, was evaluated by 3-(4, 5-dimethylthiazol- 2-yl)-2, 5-diphenyl tetrazolium bromide (MTT), cell counting, spreading area measurement and wound scratch assay. The osteogenic activity of hPDLCs was assessed using alkaline phosphatase (ALP) and alizarin red S staining (ARS). The expressions of osteogenic genes including runt related transcription factor 2 (Runx2), ALP, osteocalcin (OCN) and collagen type I (Col-I) were detected using real time quantitative PCR, western blot and immunocytochemistry assays. The biobehavior and osteogenic differentiation of hPDLCs were inhibited significantly under hypoxia. EMPs have no effect on cell proliferation under mimicked hypoxia. EMPs partly reversed the inhibitory effects of hypoxia, however, for other cellular biobehavior including attachment, spreading and migration, and markedly up-regulated osteogenic differentiation activities including ALP, mineralization ability and the expressions of osteogenic genes such as Runx2, ALP, osteocalcin, and collagen type I in hPDLCs under hypoxia. EMPs attenuate the hypoxic injury to cellular biobehavior and osteogenic differentiation in hPDLCs under hypoxia.

Dental follicle cells rescue the regenerative capacity of periodontal ligament stem cells in an inflammatory microenvironment

Aims

Periodontal ligament stem cells (PDLSCs) are one of the best candidates for periodontal regeneration. Their function could be impaired in periodontitis microenvironment. Dental follicle cells (DFCs), serving as precursor cells and mesenchymal stem cells, have intimate connection with PDLSCs. However, it is still unknown whether DFCs could provide a favorable microenvironment to improve the proliferation and differentiation capacity of PDLSCs from healthy subjects (HPDLSCs) and patients diagnosed with periodontitis (PPDLSCs).

Methods

HPDLSCs, PPDLSCs and DFCs were harvested and identified using microscopic and flow cytometric analysis. Then, the coculture systems of DFCs/HPDLSCs and DFCs/PPDLSCs were established with 0.4 µm transwell, in which all the detection indexs were obtained from HPDLSCs and PPDLSCs. The expression of stemness-associated genes was detected by real-time PCR, and the proliferation ability was assessed using colony formation and cell cycle assays. The osteogenic differentiation capacity was evaluated by real-time PCR, western blot, ALP activity, Alizarin Red S staining and calcium level analysis, while the adipogenic differentiation capacity was determined by real-time PCR and Oil Red O staining. The cell sheet formation in vitro was observed by HE staining and SEM, and the implantation effect in vivo was evaluated using HE staining and Masson’s trichrome staining.

Results

PPDLSCs had a greater proliferation capability but lower osteogenic and adipogenic potential than HPDLSCs. DFCs enhanced the proliferation and osteogenic/adipogenic differentiation of HPDLSCs and PPDLSCs to different degrees. Moreover, coculture with DFCs increased cell layers and extracellular matrix of HPDLSCs/PPDLSCs cell sheets in vitro and improved periodontal regeneration by HPDLSCs/PPDLSCs in vivo.

Conclusions

Our data suggest that the function of PPDLSCs could be damaged in the periodontitis microenvironment. DFCs appear to enhance the self-renewal and multi-differentiation capacity of both HPDLSCs and PPDLSCs, which indicates that DFCs could provide a beneficial microenvironment for periodontal regeneration using PDLSCs.

Effects of conservatively treated diseased cementum with or without EMD on in vitro cementoblast differentiation and in vivo cementum-like tissue formation of human periodontal ligament cells

OBJECTIVES

The present study aimed to evaluate the effects of conservatively treated diseased cementum on in vitro cementoblast differentiation and in vivo cementum-like tissue formation of human periodontal ligament cells (hPDLCs), and observe differential effects of enamel matrix derivative (EMD) on in vivo cementum formation by hPDLCs.

MATERIALS AND METHODS

Forty-eight cementum slices and 48 dentin slices were prepared from periodontitis compromised teeth, and hPDLCs were inoculated on to all root slices. Twenty-four co-cultured root slices of each group were used for mRNA expression of cementum attachment protein and CEMP1. With application of EMD, 24 co-cultured root slices (divided into groups C, D, C+E, D+E) were transplanted subcutaneously into nude mice. All root fragments were reviewed by histological analysis and immunohistochemical staining for bone sialoprotein.

RESULTS

mRNA expressions of cementum attachment protein and cementum protein - 1 from hPDLCs on cementum slices were statistically higher than those of dentin slices. Seven specimens of group C and 10 specimens of group C+E revealed a layer of cementum-like tissue (NFC) on surfaces of pre-existing cementum. NFC was thicker in group C+E than in group C. All NFCs were positively stained for bone sialoprotein, however, there was no NFC formation on dentin slices.

CONCLUSION

Conservatively treated diseased cementum promoted in vitro cementoblast differentiation and in vivo cementum-like tissue formation by hPDLCs, and the in vivo effect was enhanced by the presence of EMD.

Promotion of transplanted bone marrow-derived cell migration into the periodontal tissues due to orthodontic mechanical stress

BACKGROUND

Bone marrow-derived cells (BMCs) have abilities of cell migration and differentiation into tissues/organs in the body and related with the differentiation of teeth or periodontal tissue including fibroblasts. Then, we examined the effect of orthodontic mechanical stress to the transplanted BMC migration into periodontal tissues using BMC transplantation model.

MATERIAL AND METHOD

BMC from green fluorescence protein (GFP) transgenic mice were transplanted into 8-week-old female C57BL/6 immunocompromised recipient mice, which had undergone 10 Gy of lethal whole-body-irradiation. Five mice as experimental group were received orthodontic mechanical stress using separator between first molar (M1) and second molar (M2) 1 time per week for 5 weeks and 5 mice as control group were not received mechanical stress. The maxilla with M1 and M2 was removed and was immunohistochemically analyzed using a Dako Envision + Kit-K4006 and a primary anti-GFP-polyclonal rabbit antibody. Immunohistochemically stained was defined as positive area and the pixel number of positive area in the periodontal tissue was compared with the previously calculated total pixel number of the periodontal tissue.

RESULTS

The immunohistochemistry revealed that GFP positive cells were detected in the periodontal tissues, both in the experimental and control specimens. The ratio of pixel number in the examination group showed 5.77 ± 3.24 % (mean ± SD); and that in the control group, 0.71 ± 0.45 % (mean ± SD). The examination group was significantly greater than that of control group (Mann-Whitney U test: p<0.001).

CONCLUSION

These results suggest that orthodontic mechanical stress accelerates transplanted BMC migration into periodontal tissues.

Analogous effects of recombinant human full-length amelogenin expressed by Pichia pastoris yeast and enamel matrix derivative in vitro

OBJECTIVES

Amelogenins are proposed to be responsible for enamel matrix derivative (EMD)-induced periodontal regeneration; however, heterogeneity of amelogenins makes it challenging to purify the full-length proteins. This study has been carried out to express and purify a recombinant full-length human amelogenin protein (rHhAm175) in the eukaryotic yeast Pichia pastoris, and further compare biological responses of human periodontal ligament fibroblasts (PDLFs) to rHhAm175 and porcine EMD (pEMD).

MATERIALS AND METHODS

Human cDNA encoding a 175-amino acid amelogenin was subcloned into the pPIC3.5K vector. The rHhAm175 expressed in P. pastoris GS115 (Mut+) was purified and characterized. We examined cell attachment, migration and proliferation responses of human PDLFs to rHhAm175 and pEMD respectively, and characterized associated changes of proliferation-related intracellular signalling molecules, including extracellular signal response kinase (ERK) and Akt kinases/protein kinase B (Akt/PKB) kinases.

RESULTS

The purified rHhAm175 was confirmed to be molecular mass 22 021.13 Da, phosphorylated human amelogenin, and alone significantly promoted proliferation and migration of human PDLFs to an extent comparable to that of pEMD. Cell attachment was increased over the first 60 min incubation with rHhAm175 or pEMD. Both rHhAm175 and pEMD induced PDLF mitogenesis via extracellular signal response kinase (ERK1/2), but not by Akt kinases/protein kinase B (Akt/PKB).

CONCLUSIONS

rHhAm175 modulated cell activities of human PDLFs, to a comparable extent as porcine EMD. These data suggest that rHhAm175 might be used to induce periodontal tissue regeneration.

Pre-existing root cementum may promote cementoblast differentiation of human periodontal ligament cells

OBJECTIVES

To observe whether preserved healthy cementum could promote differentiation of human periodontal ligament cells to cementoblasts.

MATERIALS AND METHODS

Symmetrical root slices from each healthy premolar were distributed into either the control group (cementum removed) or test group (cementum preserved). After isolation and characterization, human periodontal ligament cells were inoculated onto root slices for 7 days co-culture. Two slices per group were studied for cell morphology by scanning electronic microscopy. Twenty-three slices were detected for expression of cementum attachment protein and cementum protein 23, two putative cementoblast markers, by real-time polymerase chain reaction. Twenty slices were transplanted into nude mice and analysed using histology and immunohistochemistry for osteopontin and bone sialoprotein expression after 8 weeks.

RESULTS

Cells of the test group had smoother fibroblast morphology and higher cementum protein 23 and cementum attachment protein expression than those of the control group (P < 0.01). In the test group, 14 root slices revealed cementum-like matrix formation resting on old cementum; no splits were observed between newly formed matrix and old cementum. In the control group, 17 specimens had fibrous tissue formation along the root surface and varying width of splits could be seen between new fibrous tissue and dentine surface. Only three specimens demonstrated presence of newly formed thin cementum-like matrix. Newly formed cementum-like matrix was positive for osteopontin and bone sialoprotein.

CONCLUSIONS

The results demonstrate that healthy root cementum may promote differentiation of human periodontal ligament cells towards cementoblasts.

Effects of enamel matrix proteins on proliferation, differentiation and attachment of human alveolar osteoblasts

OBJECTIVES

Enamel matrix proteins (EMPs) have been demonstrated to promote periodontal regeneration. However, effects of EMPs on human alveolar osteoblasts (hAOBs), up to now, have still been unclear. The purpose of this study was to investigate influence of EMPs on proliferation, differentiation and attachment of hAOBs in vitro.

MATERIALS AND METHODS

EMPs were extracted using the acetic acid method, hAOBs were obtained and cultured in vitro. Cell proliferation, alkaline phosphatase (ALP) activity, mRNA expression of osteogenic markers and cell attachment were measured in the absence and in the presence of EMPs (50, 100 and 200 μg/ml).

RESULTS

EMPs increased proliferation of hAOBs; however, they inhibited ALP activity and mRNA expression of osteogenic markers (collagen I, ALP, runt-related protein 2, osteocalcin, bone sialoprotein and osteopontin). Meanwhile, EMPs hindered hAOBs' attachment. These effects occurred in EMPs concentration-dependent manner.

CONCLUSIONS

These results indicate that EMPs may inhibit osteoblastic differentiation and attachment to prevent ankylosis and allow other cell types to regenerate periodontal tissues.

Ectopic study of tissue-engineered bone complex with enamel matrix proteins, bone marrow stromal cells in porous calcium phosphate cement scaffolds, in nude mice

OBJECTIVE

This study aimed to investigate the potential of enamel matrix proteins (EMPs) on promoting osteogenic differentiation of porcine bone marrow stromal cells (pBMSCs), as well as new bone formation capabilities, in a tissue-engineered bone complex scaffold of EMPs, pBMSCs and porous calcium phosphate cement (CPC).

MATERIALS AND METHODS

Effects of EMPs on pBMSCs in vitro was first determined by alkaline phosphatase (ALP) activity, von Kossa staining assay and mRNA expression of ALP, bone sialoprotein (BSP) and osteocalcin (OCN) genes. Next, an ectopic new bone formation test was performed in a nude mouse model with four groups: CPC scaffold alone; CPC scaffold + EMPs; CPC scaffold + pBMSCs; and CPC scaffold + EMPs + pBMSCs, for 2 or 4 weeks.

RESULTS

ALP activity, von Kossa assay and mRNA expressions of ALP, BSP and OCN genes were all significantly higher with 150 μg/ml EMP treatment in vitro. In nude mice, new bone formation was detected only in the CPC scaffold + EMPs + pBMSCs group at 2 weeks. At 4 weeks, in the tissue-engineered construct there was significantly higher bone formation ability than other groups.

CONCLUSIONS

EMPs promoted osteogenic differentiation of pBMSCs, and the tissue-engineered complex of EMPs, pBMSCs and CPC scaffold may be a valuable alternative to be used in periodontal bone tissue engineering and regeneration.

Cementum- and periodontal ligament-like tissue formation by dental follicle cell sheets co-cultured with Hertwig's epithelial root sheath cells

Dental follicle cells (DFCs) are believed contain the precursor cells of the periodontium and can form cell sheets by secreting extracellular matrix (ECM) proteins. Cell sheet engineering has been recently developed and applied successfully in the field of tissue regeneration. However, research on the in vitro characteristics of DFC sheets is lacking and an assessment of whether DFC sheets can produce periodontal tissues in vivo has not been reported. To test the characteristics and applicability of DFC sheets in this field, we established a co-culture system of rat DFCs and Hertwig's epithelial root sheath (HERS) cells in vitro, and included the following controls: a co-culture of DFCs and alveolar mucosa epithelial cells, DFCs with no cells in the upper chamber, and DFCs cultured without an upper chamber. After 3 weeks of co-culturing the cells, the DFC sheets were transplanted into adult male rats' omenta. One week after co-culturing DFCs with HERS cells, mRNA levels of collagen type I (COL-1), alkaline phosphatase (ALP), runt related transcription factor 2 (Runx 2) and bone sialoprotein (BSP) were increased significantly. In addition, after 3 weeks of co-culturing the cells, the numbers of ALP-, osteocalcin (OCN)-, BSP- and osteoprotegerin (OPG)-positive DFCs increased. The DFCs also produced more calcified nodules and exhibited an increased number of subcellular organelles, which are important for protein synthesis and secretion. Moreover, gap junctions were found between the experimental DFCs within the sheet. Five weeks of in vivo growth of DFC sheets pre-exposed to HERS cells led to the formation of cementum-like tissues, which were positive for OCN, BSP and OPG, as well as the formation of periodontal ligament-like tissues, which were positive for COL-1. In contrast, control cells only produced fibrous tissues. These results indicate that the DFC sheets induced by HERS cells are able to produce periodontal tissues through epithelial-mesenchymal interactions. Therefore, DFC sheets may be useful in the field of periodontium regeneration.

Periodontal tissue engineering and regeneration: current approaches and expanding opportunities

The management of periodontal tissue defects that result from periodontitis represents a medical and socioeconomic challenge. Concerted efforts have been and still are being made to accelerate and augment periodontal tissue and bone regeneration, including a range of regenerative surgical procedures, the development of a variety of grafting materials, and the use of recombinant growth factors. More recently, tissue-engineering strategies, including new cell- and/or matrix-based dimensions, are also being developed, analyzed, and employed for periodontal regenerative therapies. Tissue engineering in periodontology applies the principles of engineering and life sciences toward the development of biological techniques that can restore lost alveolar bone, periodontal ligament, and root cementum. It is based on an understanding of the role of periodontal formation and aims to grow new functional tissues rather than to build new replacements of periodontium. Although tissue engineering has merged to create more opportunities for predictable and optimal periodontal tissue regeneration, the technique and design for preclinical and clinical studies remain in their early stages. To date, the reconstruction of small- to moderate-sized periodontal bone defects using engineered cell-scaffold constructs is technically feasible, and some of the currently developed concepts may represent alternatives for certain ideal clinical scenarios. However, the predictable reconstruction of the normal structure and functionality of a tooth-supporting apparatus remains challenging. This review summarizes current regenerative procedures for periodontal healing and regeneration and explores their progress and difficulties in clinical practice, with particular emphasis placed upon current challenges and future possibilities associated with tissue-engineering strategies in periodontal regenerative medicine.

Emdogain in carcinogenesis: a systematic review of in vitro studies

Emdogain is a commercial product of unknown composition and is clinically used to induce periodontal regeneration. This study aims to review current knowledge of the in vitro effects of Emdogain on oral tissues and, in particular, factors related to carcinoma. A systematic approach was used to review studies from the Embase and Pubmed databases; a total of 76 studies were included. These comprised in vitro studies of the cytokines in, or regulated by, Emdogain and assays designed to study the effects of EMD on human cells in oral tissues or malignant cells. Several studies have shown that EMD regulates the proliferation, migration, adhesion, gene expression, and cytokine production of (pre-)osteoblasts, periodontal fibroblasts, and gingival fibroblasts. However, the effects of EMD on malignant oral cells are not well understood. EMD seems to have broad regulatory effects on malignant cells and on several carcinoma-related factors. Evidence suggests that patients with premalignant or malignant mucosal lesions should not be treated with EMD.

Cellular responses and expression profiling of human bone marrow stromal cells stimulated with enamel matrix proteins in vitro

OBJECTIVES

The aim of this study was to investigate biological effects and gene expression profiles of enamel matrix proteins (EMPs), on human bone marrow stromal cells (HBMSCs), for preliminary understanding of mechanisms involved in promoting periodontal regeneration by EMPs.

MATERIALS AND METHODS

EMPs were extracted using the acetic acid method, and HBMSCs from human bone marrow aspirates were cultured. Attachment levels, level of cells morphologically attenuated, cell proliferation, alkaline phosphatase (ALP) activity and staining of HBMSCs were measured in the absence and in the presence of EMPs. Microarray analysis was performed to detect gene profiles of HBMSCs by treatment with 200 microg/ml EMPs, for 5 days. Four differential genes were selected for validation of the microarray data using real-time PCR.

RESULTS

EMPs promoted proliferation and ALP activity of HBMSCs in a time- and dose-dependent manner, and at a concentration of 200 microg/ml significantly enhanced proliferation and ALP expression. However, there were no significant changes between EMP-treated groups and the control group in cell attachment and cell process attenuation levels. Twenty-seven genes were differentially expressed by HBMSCs in the presence of EMPs. Expressions of 18 genes were upregulated and expressions of nine genes were found to be downregulated. There was good consistency between data obtained from the validation group and microarray results.

CONCLUSIONS

EMPs promoted cell proliferation and differentiation and gene expression profiles of HBMSCs were affected. This may help elucidation of mechanisms involved in promoting regeneration of periodontal tissues by EMPs.