Application of eGFP to label human periodontal ligament stem cells in periodontal tissue engineering

Carbon Monoxide Releasing Molecule-3 Enhances Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Carbon Monoxide Release

Purpose

Limited intrinsic regeneration capacity following bone destruction remains a significant medical problem. Multiple regulatory effects of carbon monoxide releasing molecule-3 (CORM-3) have been reported. The aim of this study was to investigate the effect of CORM-3 on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) during osteogenesis.

Patients and Methods

hPDLSCs obtained from healthy periodontal ligament tissues were cultured and identified with specific surface antigens by flow cytometry. Effect of CORM-3 on the proliferation of hPDLSCs was determined by CCK-8 assay. Alizarin red staining and alkaline phosphatase (ALP) activity were used to assess the osteogenic differentiation of hPDLSCs. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were used to detect the expression of the indicated genes. Critical-sized skull defect was made in Balb/c-nude mice, microcomputed tomography (Micro-CT) and Masson trichrome staining were used to assess the new bone regeneration in mice.

Results

CORM-3 (400 μmol/l) significantly promoted the proliferation of hPDLSCs. CORM-3 pretreatment not only notably enhanced the mRNA and protein expression of osteo-specific marker OPN, Runx2 and ALP, but also increased mineral deposition and ALP activity by the release of CO on day 3, 7 and 14 (P<0.05). Degassed CORM-3 did not show the same effect as CORM-3. In animal model, application of CORM-3 with hPDLSCs transplantation highly increased new bone formation in skull defect region.

Conclusion

CORM-3 promoted osteogenic differentiation of hPDLSCs, and increased hPDLSCs-induced new bone formation in mice with critical-sized skull defect, which suggests an efficient and promising strategy in the treatment of disease with bone defect.

1,25(OH)2D3 supports the osteogenic differentiation of hPDLSCs under inflammatory conditions through inhibiting PLAP-1 expression transcriptionally

BACKGROUND

Periodontal ligament-associated protein-1 (PLAP-1) is a newly identified negative regulator which is the mineralization of human periodontal ligament stem cells (hPDLSCs). The aim of the present study is to determine whether 1α, 25-dihydroxyvitamin D3 (1,25(OH)₂D₃) could enhances the osteoblastic differentiation of hPDLSCs under inflammatory condition, and if PLAP-1 is involved in this process.

MATERIALS AND METHODS

hPDLSCs were in combination or alone cultured with lipopolysaccharide (LPS) and 1,25(OH)₂D₃, in osteo-inductive medium. The expression levels of osteoblastic markers and PLAP-1 of hPDLCs during osteo-inductive culture were assessed by western blot and real-time quantitative PCR(qRT-PCR). The potential vitamin D receptor elements (VDREs) which were located in PLAP-1 promoter region were identified and confirmed.

RESULTS

The data showed that LPS inhibited osteoblastic differentiation and induced the expression of PLAP-1 in hPDLSCs. The increasing addition of 1,25(OH)₂D₃ reversed the LPS-induced inhibition of osteoblastic differentiation of hPDLSCs through the suppression of PLAP-1 expression. Moreover, a potential VDRE within the PLAP-1 promoter region was identified and shown to bind with VDR by chromatin immunoprecipitation (ChIP) assays. This negative region was also found to mediate suppressor reporter gene activity.

CONCLUSIONS

1,25(OH)₂D₃ could enhances the osteogenic differentiation of hPDLSCs under inflammatory condition through inhibiting PLAP-1 expression transcriptionally.

Effect of 1α, 25-dihydroxyvitamin D3 on the osteogenic differentiation of human periodontal ligament stem cells and the underlying regulatory mechanism

1α, 25-dihydroxyvitamin D3 (1,25-D3), an active vitamin D metabolite, is a well-known regulator of osteogenic differentiation. However, how 1,25-D3 regulates osteogenic differentiation in human periodontal ligament stem cells (hPDLSCs) remains to be fully elucidated. The present study aimed to clarify this issue through well-controlled in vitro experiments. After hPDLSCs were treated with 1,25-D3, immunofluorescence and western blotting were used to detect the expression of vitamin D receptor; Cell Counting Kit-8 and western blotting were used to assay the cell proliferation ability. Alkaline phosphatase staining, Alizarin Red staining and western blotting were used to detect the osteogenic differentiation. It was found that treating hPDLSCs with 1,25-D3: i) Inhibited cell proliferation; ii) promoted osteogenic differentiation; iii) upregulated the expression of transcriptional coactivator with PDZ-binding motif (TAZ), an important downstream effector of Hippo signaling that has been demonstrated to be involved in the osteogenic differentiation of stem/progenitor cells; and iv) that co-treatment of TAZ-overexpressing hPDLSCs with 1,25-D3 synergistically stimulated the expression of osteogenic markers. These results suggested that the induction of osteogenic differentiation promoted by 1,25-D3 in hPDLSCs involves, at least in part, the action of TAZ.

Activated Yes-Associated Protein Accelerates Cell Cycle, Inhibits Apoptosis, and Delays Senescence in Human Periodontal Ligament Stem Cells

Objectives: To provide insight into the biological effects of activated Yes-associated protein (YAP) on the proliferation, apoptosis, and senescence of human periodontal ligament stem cells (h-PDLSCs). Methods: h-PDLSCs were isolated by the limiting dilution method, and their surface markers were quantified by flow cytometry. Enhanced green fluorescence protein (EGFP)-labeled lentiviral vector was used to activate YAP in h-PDLSCs, then qRT-PCR and Western blotting were used to evaluate the expression level of YAP. Immunofluorescence was used to detect the location of YAP in h-PDLSCs. The proliferation activity was detected by cell counting kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU), and the cell cycle was determined by flow cytometry. Apoptosis was analyzed by Annexin V-APC staining. Cell senescence was detected by β-galactosidase staining. Proteins in ERK, Bcl-2, and p53 signaling pathways were detected by Western blotting. Results: h-PDLSCs were isolated successfully and were positive for human mesenchymal stem cell surface markers. After YAP was activated by lentiviral vector, the mRNA and protein of YAP were highly expressed, and more YAP translocated into the nucleus. When YAP was overexpressed in h-PDLSCs, proliferation activity was improved; early and late apoptosis rates decreased (P<0.05); the proportion of cells in G2/M phases increased (P<0.05), while that in G0/G1 phase decreased (P<0.05); cellular senescence was delayed (P<0.01); the expression of P-MEK, P-ERK, P-P90RSK and P-Msk increased, while the expression of Bcl-2 family members (Bak, Bid and Bik) decreased. Conclusions: Activated YAP promotes proliferation, inhibits apoptosis, and delays senescence of h-PDLSCs. The Hippo-YAP signaling pathway can influence ERK and Bcl-2 signaling pathways.

Enamel matrix derivative enhances the proliferation and osteogenic differentiation of human periodontal ligament stem cells on the titanium implant surface

Periodontal ligament stem cells (PDLSCs) have mesenchymal-stem-cells-like qualities, and are considered as one of the candidates of future clinical application in periodontal regeneration therapy. Enamel matrix derivative (EMD) is widely used in promoting periodontal regeneration. However, the effects of EMD on the proliferation and osteogenic differentiation of human PDLSCs grown on the Ti implant surface are still no clear. Therefore, this study examined the effects of EMD on human PDLSCs in vitro. Human PDLSCs were isolated from healthy participants, and seeded on the surface of Ti implant disks and stimulated with various concentrations of EMD. Cell proliferation was determined with Cell Counting Kit-8 (CCK-8). The osteogenic differentiation of PDLSCs was evaluated by the measurement of alkaline phosphatase (ALP) activity, Alizarin red staining, and real-time polymerase chain reaction (qRT-PCR) and Western blotting, respectively. The results indicated that EMD at concentrations (5-60 µg/ml) increased the viability and proliferation of PDLSCs. The treatment with 30 and 60 µg/ml of EMD significantly elevated ALP activity, augmented mineralized nodule formation and calcium deposition, and upregulated the mRNA and protein levels of Runx-2 and osteocalcin (OCN) in the PDLSCs grown on the Ti surface. Further investigation found that EMD treatment did not change the protein levels of phosphatidylinositol-3-kinase (PI3K), p-PI3K, Akt and mTOR, but significantly upregulated the phosphorylated levels of Akt and mTOR. Collectively, these results suggest that EMD stimulation can promote the proliferation and osteogenic differentiation of PDLSCs grown on Ti surface, which is possibly associated with the activation of Akt/mTOR signaling pathway.

Efficacy of stem cells on periodontal regeneration: Systematic review of pre-clinical studies

This systematic review aims to evaluate mesenchymal stem cells (MSC) periodontal regenerative potential in animal models. MEDLINE, EMBASE and LILACS databases were searched for quantitative pre-clinical controlled animal model studies that evaluated the effect of local administration of MSC on periodontal regeneration. The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Twenty-two studies met the inclusion criteria. Periodontal defects were surgically created in all studies. In seven studies, periodontal inflammation was experimentally induced following surgical defect creation. Differences in defect morphology were identified among the studies. Autogenous, alogenous and xenogenous MSC were used to promote periodontal regeneration. These included bone marrow-derived MSC, periodontal ligament (PDL)-derived MSC, dental pulp-derived MSC, gingival margin-derived MSC, foreskin-derived induced pluripotent stem cells, adipose tissue-derived MSC, cementum-derived MSC, periapical follicular MSC and alveolar periosteal cells. Meta-analysis was not possible due to heterogeneities in study designs. In most of the studies, local MSC implantation was not associated with adverse effects. The use of bone marrow-derived MSC for periodontal regeneration yielded conflicting results. In contrast, PDL-MSC consistently promoted increased PDL and cementum regeneration. Finally, the adjunct use of MSC improved the regenerative outcomes of periodontal defects treated with membranes or bone substitutes. Despite the quality level of the existing evidence, the current data indicate that the use of MSC may provide beneficial effects on periodontal regeneration. The various degrees of success of MSC in periodontal regeneration are likely to be related to the use of heterogeneous cells. Thus, future studies need to identify phenotypic profiles of highly regenerative MSC populations.

Knockdown of Yes-Associated Protein Induces the Apoptosis While Inhibits the Proliferation of Human Periodontal Ligament Stem Cells through Crosstalk between Erk and Bcl-2 Signaling Pathways

Objective: The purpose of this study was to provide an insight into the biological effects of knockdown Yes-associated protein (YAP) on the proliferation and apoptosis of human periodontal ligament stem cells (h-PDLSCs). Methods: Immunofluorescence and Western blot were used to evaluate Hippo-YAP signaling expression level. Enhanced green fluorescence protein lentiviral vector was constructed to down-regulate YAP in h-PDLSCs. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were used to detect the interfering efficiency of YAP expression. The proliferation activity was detected by EdU staining. Analysis of apoptosis in h-PDLSCs was done through Annexin V-APC staining, while cell cycle analysis was detected by flow cytometry. Cellular senescence was analyzed by β-galactosidase activity detection. The expression of elements in signaling pathways related with proliferation and apoptosis was detected by Western blot. Results: YAP was located in nucleus and cytoplasm. After the lentivirus transfection, the expression of YAP mRNA and protein was significantly reduced (P<0.001). When YAP was knocked down, the proliferation activity of h-PDLSCs was inhibited; the early & late apoptosis rates increased; the proportion of cells in G1 phases increased (P<0.05), while that in G2 and S phase decreased (P<0.05); cellular senescence was accelerated (P<0.01); ERK and its target proteins P-P90RSK and P-MEK were reduced while Bcl-2 family members increased. Conclusion: Knockdown of YAP inhibits the proliferation activity and induces apoptosis of h-PDLSCs with the involvement of Hippo pathway and has a crosstalk between Erk and Bcl-2 signaling pathways.

Gene Therapy for Bone Defects in Oral and Maxillofacial Surgery: A Systematic Review and Meta-Analysis of Animal Studies

Craniofacial bone defects are challenging problems for maxillofacial surgeons over the years. With the development of cell and molecular biology, gene therapy is a breaking new technology with the aim of regenerating tissues by acting as a delivery system for therapeutic genes in the craniofacial region rather than treating genetic disorders. A systematic review was conducted summarizing the articles reporting gene therapy in maxillofacial surgery to answer the question: Was gene therapy successfully applied to regenerate bone in the maxillofacial region? Electronic searching of online databases was performed in addition to hand searching of the references of included articles. No language or time restrictions were enforced. Meta-analysis was done to assess significant bone formation after delivery of gene material in the surgically induced maxillofacial defects. The search identified 2081 articles, of which 57 were included with 1726 animals. Bone morphogenetic proteins were commonly used proteins for gene therapy. Viral vectors were the universally used vectors. Sprague-Dawley rats were the frequently used animal model in experimental studies. The quality of the articles ranged from excellent to average. Meta-analysis results performed on 21 articles showed that defects favored bone formation by gene therapy. Funnel plot showed symmetry with the absence of publication bias. Gene therapy is on the top list of innovative strategies that developed in the last 10 years with the hope of developing a simple chair-side protocol in the near future, combining improvement of gene delivery as well as knowledge of the molecular basis of oral and maxillofacial structures.

Enhancement of periodontal tissue regeneration by transplantation of osteoprotegerin-engineered periodontal ligament stem cells

Introduction

The objective of the present study was to evaluate the capacity of a tissue-engineered complex of human osteoprotegerin (hOPG)-transfected periodontal ligament stem cells (PDLSCs) seeding on beta-tricalcium phosphate (β-TCP) to regenerate alveolar bone defects in New Zealand rabbits.

Methods

PDLSCs were isolated from rabbit periodontal ligament tissues and expanded in vitro to enrich PDLSC numbers, and their proliferative activities and differentiation capability were evaluated under specific induction conditions. Lentiviral vector containing hOPG and enhanced green fluorescent protein (EGFP) was constructed by using Gateway technology and transfected into rabbit PDLSCs. The expression of hOPG was determined with quantitative real-time reverse transcription-polymerase chain reaction and Western blot. The PDLSCs with or without engineered hOPG were seeded on β-TCP scaffolds prior to transplantation. Morphological characterization of cells and materials was done by scanning electron microscope. Twenty rabbits with alveolar bone defects were randomly allocated into four groups and transplanted with β-TCP, PDLSCs/β-TCP, and hOPG-transfected PDLSCs/β-TCP or were left untreated as a control. Animals were sacrificed 12 weeks after operation for histological observation and histomorphometric analysis.

Results

PDLSCs expressed STRO-1 and vementin and favored osteogenesis and adipogenesis in conditioned media. Expressions of hOPG were significantly upregulated after transfection of the lentiviral vector into PDLSCs. PDLSCs attached and spread well on β-TCP, and there was no significant difference in growth of PDLSCs on β-TCP between the hOPG transfection group and the non-transfection group. The histological observation and histomorphometric analysis showed that the hOPG-transfected PDLSCs/β-TCP complex exhibited an earlier mineralization and more bone formation inside the scaffold than control, β-TCP, and PDLSCs/β-TCP complexes. Implantation of hOPG-transfected PDLSCs contributed to new bone formation as determined by EGFP gene expression under circularly polarized light microscopy.

Conclusions

The present study demonstrated the feasibility of β-TCP scaffolds for primary PDLSC culture and expression of hOPG gene in vitro and in vivo, and hOPG-transfected PDLSCs could serve as a potential cell source for periodontal bone regeneration, which may shed light on the potential of systemic hOPG gene therapy in combination with PDLSC tissue engineering as a good candidate in periodontal tissue engineering for alveolar bone regeneration.

Transfection with follicular dendritic cell secreted protein to affect phenotype expression of human periodontal ligament cells

Follicular dendritic cell secreted protein (FDC-SP), has been found to inhibit osteogenic differentiation of human periodontal ligament cells (hPDLCs) in recent studies. Based on these findings, we further investigate its effect on phenotype expression of hPDLCs in the present study, aiming to contribute to a better understanding of the biological functions governing FDC-SP-induced hPDLC differentiation. hPDLCs were firstly identified with immunocytochemical staining, followed by transfection with FDC-SP lentiviral vector. Western blot analysis was used to confirm the expression of FDC-SP. Then the influence of FDC-SP transfection on hPDLC proliferation, osteogenic and fibrogenic phenotype expression was evaluated at the mRNA and protein level. Procollagen type I c-peptide production was measured and alizarin red staining was then conducted to demonstrate effect of FDC-SP on functional differentiation. We found that hPDLCs could be successfully transfected with FDC-SP. Cell proliferation and cell cycle tests indicated that transfection with FDC-SP did not affect hPDLC proliferation. Moreover, according to real-time PCR and Western blot results, expression levels of type 1 collagen alpha 1, type 1 collagen alpha 2 and type 3 collagen were upregulated while that of osteocalcin, osteopontin, and bone sialoprotein were downregulated in FDC-SP transfected cells. In addition, hPDLCs overexpressing FDC-SP exhibited higher PIP production than the controls. Our findings demonstrate that transfection with FDC-SP has negligible adverse effect on proliferation of hPDLCs and imply the biological function of FDC-SP as a fibroblastic phenotype stabilizer by inhibiting hPDLCs differentiation into mineralized tissue-forming cells, thus regulating regeneration in periodontal tissue engineering.