Role of fibroblast subpopulations in periodontal physiology and pathology

Anti-Inflammation of N-Benzyl-4-Bromobenzamide in Lipopolysaccharide-Induced Human Gingival Fibroblasts

OBJECTIVE

To evaluate the effect of N-benzyl-4-bromobenzamide (NBBA) on lipopolysaccharide (LPS)-induced IL-6 and prostaglandin E2 (PGE2) production in human gingival fibroblasts (HGFs).

MATERIAL AND METHODS

The benzamide compound was synthesized. The condition for IL-6 production of HGFs after induction with LPS was optimized. The HGFs were incubated with NBBA (10 µg/ml) for 30 min before LPS (1 μg/ml) was added. After 24 h of incubation time, the culture media were harvested and their IL-6 and PGE2 contents were determined using an enzyme-linked immunosorbent assay. Prednisolone (PDS) and NS-398 were used as positive controls. Statistical analysis of the IL-6 and PGE2 contents was performed using the ANOVA test followed by the Tukey multiple-comparisons test to compare replicate means. p < 0.001 was considered statistically significant.

RESULTS

The maximum IL-6 production was achieved when HGFs were exposed to 1 μg/ml of LPS for 24 h, which was inhibited by the IL-6 immunosuppressant PDS. The benzamide compound, NBBA, exhibited a potent anti-IL-6 activity with inhibition of 35.6 ± 0.5%, significantly different from in the LPS-induced HGFs (p < 0.001). In addition, it inhibited 75.6 ± 0.52% PGE2 production. Cell viability was not significantly affected by treatment with NBBA at a concentration <10 µg/ml (p < 0.001).

CONCLUSIONS

NBBA exhibited an inhibitory effect on the production of IL-6 and PGE2 in LPS-induced HGFs. It could serve as a compound with inhibiting inflammatory activity in periodontal disease.

Cytotoxicity and gelatinolytic activity of a new silicon-based endodontic sealer

PURPOSE

To compare the cytotoxicity, gelatinolytic activity, and protein levels (MMP-2 and MMP-9) produced by 3T3 fibroblasts cells after stimulation with GuttaFlow 2 and AH Plus.

METHODS

3T3 fibroblasts were incubated with elutes of GuttaFlow 2 and AH Plus for 24 h. The cytotoxicity of tested materials was determined using the MTT and the LDH assay. Supernatants of cell cultures incubated with sealers were collected to determine the levels of MMP-2 and MMP-9 gelatinolytic activity by gelatin zymography. Cell lysates were used to determine MMP-2 and MMP-9 protein levels by Western Blot. Data were analyzed using ANOVA and Tukey test (P&lt;0.05).

RESULTS

AH Plus showed significantly less cell viability (mitochondrial activity of cells) than GuttaFlow 2 (P&lt;0.01). Moreover, GuttaFlow 2 was noncytotoxic, showing no statistically significant difference in LDH leakage levels compared to the control group (P&gt;0.05). Specific characterization of MMPs demonstrated that GuttaFlow 2 seemed not to affect MMP-2 levels compared with the control group, while AH Plus had elevated gelatinolytic activity and protein levels of MMP-2 as confirmed by quantitative measurements. No detectable gelatinolytic activity or protein levels of MMP-9 (92 kDa) was observed in any tested group.

CONCLUSIONS

GuttaFlow 2 did not showed cytotoxic effects and did not induce MMP-2 or MMP-9 expression.

Distinction Between Cell Proliferation and Apoptosis Signals Regulated by Brain-Derived Neurotrophic Factor in Human Periodontal Ligament Cells and Gingival Epithelial Cells

Previously, we reported that brain-derived neurotrophic factor (BDNF) enhances periodontal tissue regeneration by inducing periodontal ligament cell proliferation in vivo. In addition, the down growth of gingival epithelial cells, which comprises a major obstacle to the regeneration, was not observed. However, the underlying molecular mechanism is still unclear. Therefore, this study aimed to investigate the effect of BDNF on cell proliferation and apoptosis in human periodontal ligament (HPL) cells and human gingival epithelial cells (OBA9 cells) and to explore the molecular mechanism in vitro. HPL cells dominantly expressed a BDNF receptor, TrkB, and BDNF increased cell proliferation and ERK phosphorylation. However, its proliferative effect was diminished by a MEK1/2 inhibitor (U0126) and TrkB siRNA transfection. Otherwise, OBA9 cells showed a higher expression level of p75, which is a pan-neurotrophin receptor, than that of HPL cells. BDNF facilitated not cell proliferation but cell apoptosis and JNK phosphorylation in OBA9 cells. A JNK inhibitor (SP600125) and p75 siRNA transfection attenuated the BDNF-induced cell apoptosis. Moreover, OBA9 cells pretreated with SP600125 or p75 siRNA showed cell proliferation by BDNF stimulation, though it was reduced by U0126 and TrkB siRNA. Interestingly, overexpression of p75 in HPL cells upregulated cell apoptosis and JNK phosphorylation by BDNF treatment. These results indicated that TrkB-ERK signaling regulates BDNF-induced cell proliferation, whereas p75-JNK signaling plays roles in cell apoptotic and cytostatic effect of BDNF. Overall, BDNF activates periodontal ligament cells proliferation and inhibits the gingival epithelial cells growth via the distinct pathway. J. Cell. Biochem. 117: 1543-1555, 2016. © 2015 Wiley Periodicals, Inc.

Follicular dendritic cell-secreted protein may enhance osteoclastogenesis in periodontal disease

PURPOSE OF THE STUDY

Follicular dendritic cell-secreted protein (FDC-SP) has been found to be expressed in periodontal ligament (PDL), a layer of soft connective tissue between tooth root and alveolar bone, and involved in immunoreaction. This study was performed to explore the potential role of FDC-SP in periodontal disease.

MATERIALS AND METHODS

The human periodontal ligament cells (hPDLCs) were stimulated with Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) and FDC-SP expression was examined by real-time PCR and western blot. Then this molecule was overexpressed or silenced in hPDLCs by transfection of FDC-SP expression plasmids or its small-interfering (si) RNA, respectively, and the effects of FDC-SP on expression of osteogenesis- and osteoclastogenesis-related genes in hPDLCs were analyzed by real-time PCR and western blot.

RESULTS

Our results showed that P. gingivalis LPS upregulated FDC-SP expression in hPDLCs. Overexpression of FDC-SP could decrease the expression of osteogenesis-related genes, increase the expression of osteoclastogenesis-related genes and RANKL/OPG ratio in hPDLCs. Meanwhile, silence of FDC-SP expression in hPDLCs remarkably inversed the above results.

CONCLUSIONS

LPS-induced upregulation of FDC-SP expression in hPDLCs may enhance osteoclastogenesis in periodontal disease.

Comparing Viability of Periodontal Ligament Stem Cells Isolated From Erupted and Impacted Tooth Root

PURPOSE

The aim of the study was to compare the viability of periodontal ligament-derived stem/progenitor cells (PDLSCs) from 2 different sources.

MATERIALS AND METHODS

Periodontal ligament (PDL) tissue was obtained from 20 surgically extracted human third molars and 20 healthy premolars extracted for orthodontic reasons. Periodontal ligament-derived stem/progenitor cells were isolated from 2 different PDL tissue sources and characterized by colony forming unit assay, cell surface marker characterizations, and their osteogenic differentiation potential. To determine cell viability within 2 groups, the colorimetric 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) metabolic activity assay was used. Data were statistically analyzed using independent t-test by SPSS 16 software (SPSS Inc, Chicago, IL).

RESULTS

According to the MTT assay, the mean viability rate ± standard deviation of PDLSCs in the impacted third molar sample cells was 0.355 ± 0.411 and for erupted premolar sample cells was 0.331 ± 0.556. Based on One-Sample Kolmogorov-Smirnov test, P value for impacted and erupted teeth was 0.954 and 0.863, respectively. No statistical difference was seen between 2 groups. (P value > 0.05) CONCLUSIONS: Our results demonstrated that if surgical aseptic technique is a method employed to maintain asepsis, PDLSCs obtained from impacted and erupted tooth root would have the same viability rate.

Activation of canonical Wnt/β-catenin signaling inhibits H2O2-induced decreases in proliferation and differentiation of human periodontal ligament fibroblasts

Human periodontal ligament fibroblasts (hPLFs) are exposed to oxidative stress during periodontal inflammation and dental treatments. It is hypothesized that hydrogen peroxide (H2O2)-mediated oxidative stress decreases survival and osteogenic differentiation of hPLFs, whereas these decreases are prevented by activation of the Wnt pathway. However, there has been a lack of reports that define the exact roles of canonical Wnt/β-catenin signaling in H2O2-exposed hPLFs. Treatment with H2O2 reduced viability and proliferation in hPLFs in a dose- and time-dependent manner and led to mitochondria-mediated apoptosis. Pretreatment with lithium chloride (LiCl) or Wnt1 inhibited the oxidative damage that occurred in H2O2-exposed hPLFs. However, knockout of β-catenin or treatment with DKK1 facilitated the H2O2-induced decreases in viability, mitochondrial membrane potential, and Bcl-2 induction. Osteoblastic differentiation of hPLFs was also inhibited by combined treatment with 100 μM H2O2, as evidenced by the decreases in alkaline phosphatase (ALP) activity and mineralization. H2O2-mediated inhibition of osteoblast differentiation in hPLFs was significantly attenuated in the presence of 500 ng/ml Wnt1 or 20 mM LiCl. In particular, H2O2 stimulated the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) at protein and mRNA levels in hPLFs, whereas the induction was almost completely suppressed in the presence of Wnt1 or LiCl. Furthermore, siRNA-mediated silencing of Nrf2 blocked H2O2-induced decreases in ALP activity and mineralization of hPLFs with the concomitant restoration of runt-related transcription factor 2 and osteocalcin mRNA expression and ALP activity. Collectively, these results suggest that activation of the Wnt/β-catenin pathway improves proliferation and mineralization in H2O2-exposed hPLFs by downregulating Nrf2.

Recombinant Human Plasminogen Activator Inhibitor-1 Promotes Cementogenic Differentiation of Human Periodontal Ligament Stem Cells

The periodontium, consisting of gingiva, periodontal ligament (PDL), cementum, and alveolar bone, is necessary for the maintenance of tooth function. Specifically, the regenerative abilities of cementum with inserted PDL are important for the prevention of tooth loss. Periodontal ligament stem cells (PDLSCs), which are located in the connective tissue PDL between the cementum and alveolar bone, are an attractive candidate for hard tissue formation. We investigated the effects of recombinant human plasminogen activator inhibitor-1 (rhPAI-1) on cementogenic differentiation of human PDLSCs (hPDLSCs) in vitro and in vivo. Untreated and rhPAI-1-treated hPDLSCs mixed with hydroxyapatite/tricalcium phosphate (HA/TCP) and dentin matrix were transplanted subcutaneously into the dorsal surface of immunocompromised mice to assess their capacity for hard tissue formation at 8 and 10 weeks posttransplantation. rhPAI-1 accelerated mineral nodule formation and increased the mRNA expression of cementoblast-associated markers in hPDLSCs. We also observed that rhPAI-1 upregulated the levels of osterix (OSX) and cementum protein 1 (CEMP1) through Smad2/3 and p38 pathways, whereas specific inhibitors of Smad3 and p38 inhibited the enhancement of mineralization of hPDLSCs by rhPAI-1. Furthermore, transplantation of hPDLSCs with rhPAI-1 showed a great ability to promote cementogenic differentiation. Notably, rhPAI-1 induced hPDLSCs to regenerate cementum-like tissue with PDL fibers inserted into newly formed cementum-like tissue. These results suggest that rhPAI-1 may play a key role in cementogenic differentiation of hPDLSCs. rhPAI-1 with hPDLSCs may be a good candidate for future clinical applications in periodontal tissue regeneration and possibly in tooth root bioengineering.

Immunomodulatory effects of stem cells

Adult-derived mesenchymal stem cells have received considerable attention over the past two decades for their potential use in tissue engineering, principally because of their potential to differentiate into multiple stromal-cell lineages. Recently, the immunomodulatory properties of mesenchymal stem cells have attracted interest as a unique property of these cells that may be harnessed for novel therapeutic approaches in immune-mediated diseases. Mesenchymal stem cells have been shown to inhibit the proliferation of activated T-cells both in vitro and in vivo but to stimulate T-regulatory cell proliferation. Mesenchymal stem cells are also known to be weakly immunogenic and to exert immunosuppressive effects on B-cells, natural killer cells, dendritic cells and neutrophils through various mechanisms. Furthermore, intravenous administration of allogeneic mesenchymal stem cells has shown a marked suppression of host immune reactions in preclinical animal models of large-organ transplant rejection and in various autoimmune- and inflammatory-based diseases. Some clinical trials utilizing human mesenchymal stem cells have also produced promising outcomes in patients with graft-vs.-host disease and autoimmune diseases. Mesenchymal stem cells identified from various dental tissues, including periodontal ligament stem cells, also possess multipotent and immunomodulatory properties. Hence, dental mesenchymal stem cells may represent an alternate cell source, not only for tissue regeneration but also as therapies for autoimmune- and inflammatory-mediated diseases. These findings have elicited interest in dental tissue mesenchymal stem cells as alternative cell sources for modulating alloreactivity during tissue regeneration following transplantation into human leukocyte antigen-mismatched donors. To examine this potential in periodontal regeneration, future work will need to assess the capacity of allogeneic periodontal ligament stem cells to regenerate periodontal ligament in animal models of periodontal disease. The present review describes the immunosuppressive effects of mesenchymal stem cells on various types of immune cells, the potential mechanisms through which they exert their mode of action and the preclinical animal studies and human clinical trials that have utilized mesenchymal stem cells, including those populations originating from dental structures.

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.

Mechano-regulation of collagen biosynthesis in periodontal ligament

Periodontal ligament (PDL) plays critical roles in the development and maintenance of periodontium such as tooth eruption and dissipation of masticatory force. The mechanical properties of PDL are mainly derived from fibrillar type I collagen, the most abundant extracellular component. The biosynthesis of type I collagen is a long, complex process including a number of intra- and extracellular post-translational modifications. The final modification step is the formation of covalent intra- and intermolecular cross-links that provide collagen fibrils with stability and connectivity. It is now clear that collagen post-translational modifications are regulated by groups of specific enzymes and associated molecules in a tissue-specific manner; and these modifications appear to change in response to mechanical force. This review focuses on the effect of mechanical loading on collagen biosynthesis and fibrillogenesis in PDL with emphasis on the post-translational modifications of collagens, which is an important molecular aspect to understand in the field of prosthetic dentistry.

Osteogenic differentiation of human periodontal ligament cells after transfection with recombinant lentiviral vector containing follicular dendritic cell secreted protein

BACKGROUND AND OBJECTIVE

Follicular dendritic cell secreted protein (FDC-SP), has been identified in human periodontal ligament (PDL) in a recent study. It is suggested that the expression of FDC-SP might be associated with the osteogenic differentiation and mineralization of human periodontal ligament cells (hPDLCs). However, the intrinsic mechanism regarding this is still unclear. The aim of this study was to establish hPDLCs with safe and efficient overexpression of FDC-SP and to elucidate the influence of FDC-SP transfection on hPDLC osteogenesis in periodontal regeneration.

MATERIAL AND METHODS

We first applied a recombinant lentiviral vector containing FDC-SP to transfect hPDLCs via different multiplicity of infection (MOI) levels (1, 10, 20, 50 and 100). Western blot was performed to confirm the expression of FDC-SP. MTT assay was employed to evaluate the proliferation status of transfected cells. Then, the extent of osteogenic differentiation was investigated by simultaneous monitoring of alkaline phosphatase (ALP) activity assessment, immunofluorescent staining, the expression patterns of osteoblastic markers and mineralization staining.

RESULTS

We found that hPDLCs transfected via MOI 20, 50 and 100 exhibited expression of FDC-SP protein compared with MOI 1 and 10. There was no significant effect of FDC-SP transfection (at different MOI levels of 1, 10 and 20) on the proliferation of hPDLCs, whereas higher MOI levels (50 and 100) inhibited cell proliferation ability. In addition, ALP activity decreased significantly in FDC-SP-transfected hPDLCs at day 7. When stained with alizarin red, cells overexpressing FDC-SP formed less mineralized nodules at 21 d post-induction of differentiation, compared with the control cultures. Osteogenic inhibition was also confirmed by ALP immunostaining. Moreover, mRNA expression levels of osteoblastic markers decreased after FDC-SP transfection, which were in accordance with western blot results.

CONCLUSION

Our data suggest that MOI 20 is optimal to transfect hPDLCs, which achieves safe and efficient overexpression of FDC-SP in transfected cells. Moreover, FDC-SP overexpression inhibits osteogenic differentiation of hPDLCs. The present study contributes to a better understanding of the biological functions governing FDC-SP-induced hPDLC differentiation.

Mechanism of drug-induced gingival overgrowth revisited: a unifying hypothesis

Drug-induced gingival overgrowth (DIGO) is a disfiguring side effect of anti-convulsants, calcineurin inhibitors, and calcium channel blocking agents. A unifying hypothesis has been constructed which begins with cation flux inhibition induced by all three of these drug categories. Decreased cation influx of folic acid active transport within gingival fibroblasts leads to decreased cellular folate uptake, which in turn leads to changes in matrix metalloproteinases metabolism and the failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue which presents as DIGO. Studies supporting this hypothesis are discussed.

Periodontal ligament-derived cells for periodontal regeneration in animal models: a systematic review

BACKGROUND AND OBJECTIVE

Implantation of periodontal ligament stem cells is emerging as a potential periodontal regenerative procedure. This systematic review considers the evidence from animal models investigating the use of periodontal ligament stem cells for successful periodontal regeneration.

MATERIAL AND METHODS

PubMed, Embase, MEDLINE and Google Scholar were searched to December 2013 for quantitative studies examining the outcome of implanting periodontal ligament stem cells into experimental periodontal defects in animals. Inclusion criteria were: implantation of periodontal ligament stem cells into surgically created periodontal defects for periodontal regeneration; animal models only; source of cells either human or animal; and published in English. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

From the literature search, 43 studies met the inclusion criteria. A wide variety of surgical defects were created in four species of animal (dog, rat, pig and sheep). Owing to wide variability in defect type, cell source and cell scaffold, no meta-analysis was possible. Outcome measures included new bone, new cementum and new connective tissue formation. In 70.5% of the results, statistically significant improvements of these measures was recorded.

CONCLUSION

These results are notable in that they indicate that irrespective of the defect type and animal model used, periodontal ligament stem cell implantation can be expected to result in a beneficial outcome for periodontal regeneration. It is recommended that there is sufficient evidence from preclinical animal studies to warrant moving to human studies to examine the efficacy, safety, feasibility (autologous vs. allogeneic transplantation) and delivery of periodontal ligament stem cells for periodontal regeneration.

Adult stem cell therapy for periodontal disease

Periodontal disease is a major cause of tooth loss and characterized by inflammation of tooth-supporting structures. Recently, the association between periodontal disease and other health problems has been reported, the importance of treating periodontal disease for general health is more emphasized. The ultimate goal of periodontal therapy is regeneration of damaged periodontal tissues. The development of adult stem cell research enables to improve the cell-based tissue engineering for periodontal regeneration. In this review, we present the results of experimental pre-clinical studies and a brief overview of the current state of stem cells therapy for periodontal diseases.

Function of chemokine (CXC motif) ligand 12 in periodontal ligament fibroblasts

The periodontal ligament (PDL) is one of the connective tissues located between the tooth and bone. It is characterized by rapid turnover. Periodontal ligament fibroblasts (PDLFs) play major roles in the rapid turnover of the PDL. Microarray analysis of human PDLFs (HPDLFs) and human dermal fibroblasts (HDFs) demonstrated markedly high expression of chemokine (CXC motif) ligand 12 (CXCL12) in the HPDLFs. CXCL12 plays an important role in the migration of mesenchymal stem cells (MSCs). The function of CXCL12 in the periodontal ligament was investigated in HPDLFs. Expression of CXCL12 in HPDLFs and HDFs was examined by RT-PCR, qRT-PCR and ELISA. Chemotactic ability of CXCL12 was evaluated in both PDLFs and HDFs by migration assay of MSCs. CXCL12 was also immunohistochemically examined in the PDL in vivo. Expression of CXCL12 in the HPDLFs was much higher than that in HDFs in vitro. Migration assay demonstrated that the number of migrated MSCs by HPDLFs was significantly higher than that by HDFs. In addition, the migrated MSCs also expressed CXCL12 and several genes that are familiar to fibroblasts. CXCL12 was immunohistochemically localized in the fibroblasts in the PDL of rat molars. The results suggest that PDLFs synthesize and secrete CXCL12 protein and that CXCL12 induces migration of MSCs in the PDL in order to maintain rapid turnover of the PDL.

Neural crest-derived dental stem cells--where we are and where we are going

OBJECTIVES

There are five types of post-natal human dental stem cells that have been identified, isolated and characterized. Here, we review the information available on dental stem cells as well as their potential applications in dentistry, regenerative medicine and the development of other therapeutic approaches.

DATA

Data pertinent to dental stem cells and their applications, published in peer-reviewed journals from 1982 to 2013 in English were reviewed.

SOURCES

Sources were retrieved from PubMed databases as well as related references that the electronic search yielded.

STUDY SELECTION

Manuscripts describing the origin, retrieval, characterization and application of dental stem cells were obtained and reviewed.

CONCLUSIONS

Dental stem cell populations present properties similar to those of mesenchymal stem cells, such as the ability to self-renew and the potential for multilineage differentiation. While they have greater capacity to give rise to odontogenic cells and regenerate dental pulp and periodontal tissue, they have the capacity to differentiate into all three germ line cells, proving that a population of pluripotent stem cells exists in the dental tissues.

CLINICAL SIGNIFICANCE

Dental stem cells have the capacity to differentiate into endoderm, mesoderm and ectoderm tissues. Consequently they do not only have applications in dentistry, but also neurodegenerative and ischemic diseases, diabetes research, bone repair, and other applications in the field of tissue regeneration.

Role of HMGB1 in proliferation and migration of human gingival and periodontal ligament fibroblasts

High mobility group box 1 (HMGB1) was originally defined as a nuclear protein. However, later studies showed that HMGB1 was released from damaged cells into the extracellular milieu and functioned as a danger signaling molecule. HMGB1 has also been shown to exert proliferative and chemoattractant effects on many cell types. In this study, we investigated the in vitro effect of human recombinant HMGB1 on the proliferation and migration of human gingival fibroblasts (HGF) and human periodontal ligament fibroblasts (HPDLF). For the proliferation assay, HGF and HPDLF were cultured in the presence of 5, 10, and 50 ng/mL HMGB1. After a period of 6 days, cell proliferation was determined by MTT assay. The migration assay was performed by culturing the two cell types in Transwells with HMGB1 in the lower chamber as a chemoattractant. Cell migration during 16 h was determined by crystal violet staining of the cells that migrated across the membrane. The results showed that HMGB1, at 50 ng/mL, was able to significantly induce proliferation of HGF by up to 171.4 ± 17.1%. No such proliferation induction was seen for HPDLF. In the migration assay, however, 100 ng/mL HMGB1 induced migration of both cell types. The counts of cells that migrated across the membrane, as compared with the control, were increased to 273 ± 24.1% and 410.3 ± 158% for HGF and HPDLF, respectively. Since proliferation and migration are basic abilities of cells required for proper tissue repair, these data suggest that HMGB1 plays an important role in these functions of periodontal cells.

Domain of dentine sialoprotein mediates proliferation and differentiation of human periodontal ligament stem cells

Classic embryological studies have documented the inductive role of root dentin on adjacent periodontal ligament differentiation.  The biochemical composition of root dentin includes collagens and cleavage products of dentin sialophosphoprotein (DSPP), such as dentin sialoprotein (DSP).  The high abundance of DSP in root dentin prompted us to ask the question whether DSP or peptides derived thereof would serve as potent biological matrix components to induce periodontal progenitors to further differentiate into periodontal ligament cells. Here, we test the hypothesis that domain of DSP influences cell fate. In situ hybridization and immunohistochemical analyses showed that the COOH-terminal DSP domain is expressed in mouse periodontium at various stages of root development. The recombinant COOH-terminal DSP fragment (rC-DSP) enhanced attachment and migration of human periodontal ligament stem cells (PDLSC), human primary PDL cells without cell toxicity. rC-DSP induced PDLSC cell proliferation as well as differentiation and mineralization of PDLSC and PDL cells by formation of mineralized tissue and ALPase activity. Effect of rC-DSP on cell proliferation and differentiation was to promote gene expression of tooth/bone-relate markers, transcription factors and growth factors. The results for the first time showed that rC-DSP may be one of the components of cell niche for stimulating stem/progenitor cell proliferation and differentiation and a natural scaffold for periodontal regeneration application.

Stem cells, tissue engineering and periodontal regeneration

The aim of this review is to discuss the clinical utility of stem cells in periodontal regeneration by reviewing relevant literature that assesses the periodontal-regenerative potential of stem cells. We consider and describe the main stem cell populations that have been utilized with regard to periodontal regeneration, including bone marrow-derived mesenchymal stem cells and the main dental-derived mesenchymal stem cell populations: periodontal ligament stem cells, dental pulp stem cells, stem cells from human exfoliated deciduous teeth, stem cells from apical papilla and dental follicle precursor cells. Research into the use of stem cells for tissue regeneration has the potential to significantly influence periodontal treatment strategies in the future.

The effects of dexamethasone on the apoptosis and osteogenic differentiation of human periodontal ligament cells

PURPOSE

The purpose of the current study was to examine the effect of dexamethasone (Dex) at various concentrations on the apoptosis and mineralization of human periodontal ligament (hPDL) cells.

METHODS

hPDL cells were obtained from the mid-third of premolars extracted for orthodontic reasons, and a primary culture of hPDL cells was prepared using an explant technique. Groups of cells were divided according to the concentration of Dex (0, 1, 10, 100, and 1,000 nM). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed for evaluation of cellular viability, and alkaline phosphatase activity was examined for osteogenic differentiation of hPDL cells. Alizarin Red S staining was performed for observation of mineralization, and real-time polymerase chain reaction was performed for the evaluation of related genes.

RESULTS

Increasing the Dex concentration was found to reduce cellular viability, with an increase in alkaline phosphatase activity and mineralization. Within the range of Dex concentrations tested in this study, 100 nM of Dex was found to promote the most vigorous differentiation and mineralization of hPDL cells. Dex-induced osteogenic differentiation and mineralization was accompanied by an increase in the level of osteogenic and apoptosis-related genes and a reduction in the level of antiapoptotic genes. The decrease in hPDL cellular viability by glucocorticoid may be explained in part by the increased prevalence of cell apoptosis, as demonstrated by BAX expression and decreased expression of the antiapoptotic gene, Bcl-2.

CONCLUSIONS

An increase in hPDL cell differentiation rather than cellular viability at an early stage is likely to be a key factor in glucocorticoid induced mineralization. In addition, apoptosis might play an important role in Dex-induced tissue regeneration; however, further study is needed for investigation of the precise mechanism.

Human periodontal ligament fibroblast response to rhPDGF-BB application on periodontally diseased root surfaces-in vitro

The aim of the present study was to evaluate the influence of recombinant platelet derived growth factor-BB (rhPDGF-BB) on the cellular proliferation, morphology and adherence of human periodontal ligament fibroblasts (PLFs) to the root surfaces of periodontally diseased and healthy human teeth roots at two different time periods. Primary cell cultures of PLFs were obtained from clinically healthy premolar or mandibular third molar teeth. 11 scaffolds were prepared from healthy teeth for group-1 (Healthy Substrates), 33 scaffolds were prepared from periodontally diseased teeth, which were further divided in Group-2 - Periodontally diseased substrates, Group-3 - Scaled and Root planed (SRP) substrates, Group-4 - SRP + rhPDGF-BB (50 ng/ml). Groups were further subdivided into two groups (n = 5 scaffolds per subgroup) and PLFs were incubated on the scaffolds for three and seven days, topographical assessment was done on the remaining substrate. Cell morphology and counting was assessed under a scanning electron microscope at 350× on day three and seven and statistically compared with the Mann-Whitney U test and the Kruskal-Wallis test. On day three, Group 1 showed least number of cells attached, whereas maximum number of cells were attached on Group 3 (SRP only) substrates. For day 7, Group 1 and Group 4 showed increase in the number of cells from day 3 to 7, while number of cells attached/substrate reduced drastically for Group 2 and 3 substrates. Group 3 and 4 showed better adhesion and proliferation of PLFs as compared to Group 1 and 2. Group-1 and Group-4 showed predominantly spindle cells with flat appearance, Group-3 showed stellate cells and Group-2 showed predominantly distorted spindle shaped cells. The results of this in-vitro study indicates that rhPDGF-BB plays a significant role as an adjunct to periodontal therapy in influencing maturity, attachment and proliferation of PLFs.

Resolvin D1 protects periodontal ligament

Resolution agonists are endogenous mediators that drive inflammation to homeostasis. We earlier demonstrated in vivo activity of resolvins and lipoxins on regenerative periodontal wound healing. The goal of this study was to determine the impact of resolvin D1 (RvD1) on the function of human periodontal ligament (PDL) fibroblasts, which are critical for wound healing during regeneration of the soft and hard tissues around teeth. Primary cells were cultured from biopsies obtained from three individuals free of periodontal diseases. Peripheral blood mononuclear cells were isolated by density gradient centrifugation from whole blood of healthy volunteers. PGE2, leukotriene B4 (LTB4), and lipoxin A4 (LXA4) in culture supernatants were measured by ELISA. The direct impact of RvD1 on PDL fibroblast proliferation was measured and wound closure was analyzed in vitro using a fibroblast culture "scratch assay." PDL fibroblast function in response to RvD1 was further characterized by basic FGF production by ELISA. IL-1β and TNF-α enhanced the production of PGE2. Treatment of PDL cells and monocytes with 0.1-10 ng/ml RvD1 (0.27-27 M) reduced cytokine induced production of PGE2 and upregulated LXA4 production by both PDL cells and monocytes. RvD1 significantly enhanced PDL fibroblast proliferation and wound closure as well as basic FGF release. The results demonstrate that anti-inflammatory and proresolution actions of RvD1 with upregulation of arachidonic acid-derived endogenous resolution pathways (LXA4) and suggest resolution pathway synergy establishing a novel mechanism for the proresolution activity of the ω-3 docosahexaenoic acid-derived resolution agonist RvD1.

Enhanced periodontal tissue regeneration by periodontal cell implantation

AIM

Due to a lack of regenerative potential, current treatments for periodontal defects do not always provide satisfactory clinical results. Previously, the implantation of a biomaterial scaffold-cell construct has been suggested as a clinically achievable approach. In this study, it was aimed to investigate the contribution of implanted periodontal ligament (PDL) cells to periodontal tissue regeneration.

MATERIALS & METHODS

Gelatin sponges were seeded with green fluorescent protein (GFP) transfected PDL or gingival fibroblasts (GF) cells, and implanted into a surgically created rat intrabony periodontal defect model. After six weeks, decalcified maxillae were used for histomorphometrical and immunohistochemical analyses.

RESULTS

After six weeks, animals that had received the PDL cells exhibited significantly more functional bone and ligament. Furthermore, there were remarkable differences in the distribution of the transplanted cells. Periodontal ligament cells were always located directly lining the newly regenerated areas. In contrast, GF cells dispersed over the whole defect area, and did not provide a favourable effect on the regeneration of the periodontal tissues.

CONCLUSION

We concluded that PDL cells transplanted into a periodontal defect survive and favour regeneration of periodontium, possibly in a paracrine manner.

Differential effects of growth factors and cytokines on the synthesis of SPARC, DNA, fibronectin and alkaline phosphatase activity in human periodontal ligament cells

Growth factors and cytokines play an important role in tissue development and repair. However, it remains unknown how they act on proliferation and differentiation of periodontal ligament cells. In this study, we investigated the effects of several growth factors and cytokines on the synthesis of DNA, alkaline phosphatase (ALPase), fibronectin, and secreted protein acidic and rich in cysteine (SPARC) in human periodontal ligament (HPL) cells. Transforming growth factor-beta (TGF-beta) increased the synthesis of DNA, fibronectin and SPARC, whereas it decreased ALPase activity. Basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) and tumor necrosis factor-alpha (TNF-alpha) decreased SPARC and ALPase levels, whereas these peptides increased DNA synthesis and did not affect fibronectin synthesis. Epidermal growth factor (EGF) up-regulated the synthesis of DNA and fibronectin and inhibited SPARC and ALPase levels. Interleukin-1beta (IL-1beta) decreased the synthesis of DNA, ALPase, fibronectin and SPARC. These findings demonstrate that TGF-beta, bFGF, EGF, PDGF, TNF-alpha and IL-1beta have characteristically different patterns of action on DNA, SPARC, fibronectin and ALPase synthesis by HPL cells. The differences in regulation of function of periodontal ligament cells by these peptides may be involved in the regeneration and repair of periodontal tissue.

Continuously generated H2O2 stimulates the proliferation and osteoblastic differentiation of human periodontal ligament fibroblasts

Numerous studies have shown that hydrogen peroxide (H(2)O(2)) inhibits proliferation and osteoblastic differentiation in bone-like cells. Human periodontal ligament fibroblasts (PLF) are capable of differentiating into osteoblasts and are exposed to oxidative stress during periodontal inflammation. However, the cellular responses of PLF to H(2)O(2) have not been identified. In this study, we examined how H(2)O(2) affects the viability and proliferation of PLF by exposing the cells to glucose oxidase (GO) or direct addition of H(2)O(2). We also explored the effects of GO on the osteoblastic differentiation of PLF and the mechanisms involved. The viability and proliferation in PLF were increased with the addition of 10 mU/ml GO but not by volumes greater than 15 mU/ml or by H(2)O(2) itself. GO-stimulated DNA synthesis was correlated with the increase in cyclin E protein levels in the cells. Osteoblastic differentiation of PLF was also augmented by combined treatment with GO, as evidenced by the increases in alkaline phosphatase activity, mineralization, collagen synthesis, and osteocalcin content in the cells. The inductions of runt-related transcription factor 2 and osterix mRNA and proteins were further increased in PLF incubated in combination with GO compared to those in untreated cells. These results demonstrate that the continuous presence of H(2)O(2) stimulates the proliferation of PLF and augments their potential to differentiate into osteoblasts through the up-regulation of bone-specific transcription factors. Collectively, we suggest that H(2)O(2) may elicit the functions of PLF in maintaining the dimensions of the periodontal ligament and in mediating a balanced metabolism in alveolar bone.

Combining human periodontal ligament cell membrane chromatography with online HPLC/MS for screening osteoplastic active compounds from Coptidis Rhizoma

We have developed an online analytical method that combines human periodontal ligament cell membrane chromatography (hPDLC/CMC) with high-performance liquid chromatography and mass spectrometry (LC/MS) for recognizing and identifying osteoplastic active components from Coptidis Rhizoma. Retention fractions on hPDLC/CMC were enriched onto an enrichment column and the components were directly analyzed by combining a 10-port column switcher with an LC/MS system for separation and preliminary identification. Using simvastatin (SIM) as a positive control, berberine from Coptidis Rhizoma was identified as the active component which could act on the hPDLC. The MTT colorimetric assay, alkaline phosphatase (ALP) activity, and staining tests revealed that berberine could promote hPDLC growth, increase the secretion of ALP in the culture medium, and enhance the formation of mineralized nodule, thus it is a potential osteoplastic ingredient. This hPDLC/CMC-online-LC/MS method can be applied for screening active components acting on hPDLC from traditional Chinese medicines exemplified by Coptidis Rhizoma and will be of great utility in drug discovery using natural medicinal herbs as a source of leading compounds.

Nicotinic acetylcholine receptor α7 and β4 subunits contribute nicotine-induced apoptosis in periodontal ligament stem cells

Nicotine, a major component of cigarette smoking, is the important risk factor for the development of periodontal disease. However, the mechanisms that underlie the cytotoxicity of nicotine in human periodontal ligament stem cells (PDLSCs) are largely unknown. Thus, the purpose of this study was to determine the cytotoxic effect of nicotine by means of nicotinic acetylcholine receptor (nAChR) activation in PDLSCs. We first detected α7 and β4 nAChRs in PDLSCs. The gene expressions of α7 and β4 nAChR were increased by nicotine administration. Nicotine significantly decreased cell viability at a concentration higher than 10(-5) M. DNA fragmentation was also detected at high doses of nicotine treatment. Moreover, the detection of sub G1 phase and TUNEL assay demonstrated that nicotine significantly induced apoptotic cell death at 10(-2) M concentration. Western blot analysis confirmed that p53 proteins were phosphorylated by nicotine. Under various doses of nicotine, a decrease in the anti-apoptotic protein Bcl-2, but an increase in p53 and cleaved caspase-3 protein levels, was detected in a dose-dependent manner. However, the apoptotic effect of nicotine was inhibited by the pretreatment of α-bungarotoxin, a selective α7 nAChR antagonist or mecamylamine, a non-selective nAChR antagonist. Finally, increases in the subG1 phase and DNA fragmentation by nicotine was attenuated by each nAChR antagonist. Collectively, the presence of α7 and β4 nAChRs in PDLSCs supports a key role of nAChRs in the modulation of nicotine-induced apoptosis.

Highly osteogenic PDL stem cell clones specifically express elevated levels of ICAM1, ITGB1 and TERT

Cells derived from the periodontal ligament (PDL) have previously been reported to have stem cell-like characteristics (PDL stem cells; PDLSCs) and play an important part in bone engineering, including that of alveolar bone. However, these populations have been heterogeneous, and thus far no specific marker has yet been established from adult human stem cells derived from PDL tissue. We have previously isolated highly purified single cell-derived PDLSC clones and delineated their phenotypic and functional characteristics. In this report, we further obtained three homogeneous and distinct PDLSC clones demonstrating low, moderate and high mineralized matrix forming ability-namely PC12, PC4 and PC3, respectively, and the expression of mesenchymal stem cell pathway-specific genes in these clones was investigated. PCR array revealed that the expression of intercellular adhesion molecule 1 (ICAM1), integrin beta 1 (ITGB1) and telomerase reverse transcriptase (TERT) was associated with highly osteogenic PDLSC clones, as determined by the expression of key osteoblastic markers and their ability to form alizarin red S positive mineralized matrix in vitro. The present results suggest that these three mesenchymal stem cell-associated markers could potentially be used to isolate PDLSCs with high osteogenic capability for engineering new bone.

Effect of FDC-SP on the phenotype expression of cultured periodontal ligament cells

INTRODUCTION

Recently, a novel protein, follicular dendritic cell secreted protein (FDC-SP), has been identified in human periodontal ligament (PDL) tissue and a biomolecular study suggested that the expression of FDC-SP might be associated with the expression of the PDL phenotype. The purpose of this study was to test the effect of FDC-SP on the proliferation and phenotype of PDL cells.

MATERIAL AND METHODS

Periodontal ligament cells obtained following the 3(rd) passage were exposed to various concentrations of FDC-SP. The cell proliferation was monitored by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide(MTT) assay. Then, as a measure of osteogenic activity, the alkaline phosphatase (ALP) activity was recorded after 4, 7, and 14 days using p-nitrophenylphosphate as a substrate. Finally, total RNA was extracted and RT-PCR was performed for gene analysis.

RESULTS

The results indicated that PDL cells exposed to 50 ng/ml FDC-SP could proliferate more rapidly. RT-PCR results showed that the mRNA expression of epidermal growth factor receptor (EGFR) was obviously upregulated and the mRNA expression of osteocalcin (OCN) and bone sialoprotein (BSP) were downregulated in PDL cells exposed to FDC-SP. Moreover, two groups of PDL cells exposed to FDC-SP showed a significant decrease of ALP activity during all the culture days.

CONCLUSIONS

In sum, the findings observed in this study suggest that FDC-SP in PDL cells could positively affect the proliferation and act as a fibroblastic phenotype stabilizer by inhibiting their differentiation into mineralized tissue-forming cells.

Induced pluripotent stem cell lines derived from human gingival fibroblasts and periodontal ligament fibroblasts

BACKGROUND AND OBJECTIVE

Human induced pluripotent stem (iPS) cells, which have similar properties to human embryonic stem (hES) cells, have been generated from neonatal and adult human dermal fibroblasts by reprogramming. iPS cells have high pluripotency and differentiation potential, and may be a potential autologous stem cell source for future regenerative therapy.

MATERIAL AND METHODS

iPS cell lines from human gingival fibroblasts and, for the first time, from periodontal ligament fibroblasts, were generated by reprogramming using a retroviral transduction cocktail of OCT3/4, SOX2, KLF4 and c-MYC. iPS induction was investigated through expression of the embryonic stem cell markers SSEA4, OCT4, NANOG, GCTM-2, TG30 and TRA-1-60. Following in vitro differentiation, the expression of genes for differentiation markers for ectoderm (SOX1, PAX6), mesoderm [RUNX1, T(Brachyury)] and endoderm (GATA4, AFP) was assessed by real-time RT-PCR. The ability to form teratomas following implantation into mouse testes was assessed by histology.

RESULTS

Human gingival fibroblast- and periodontal ligament fibroblast-derived iPS cells showed similar characteristics to hES cells. Both sets of iPS cells displayed colony morphology comparable to that of hES cells and expressed the hES cell-associated cell-surface antigens, SSEA3, SSEA4, GCTM-2, TG30 (CD9) and Tra-1-60, and the hES cell marker genes, OCT4, NANOG and GDF3. These iPS cells showed differentiation potential to form embryoid bodies in vitro and expressed genes for endoderm, ectoderm and mesoderm. Teratoma formation following implantation into mouse testes was observed.

CONCLUSION

These results demonstrate that iPS cells can be successfully generated from adult human gingival and periodontal ligament fibroblasts.

Validation of human periodontal ligament-derived cells as a reliable source for cytotherapeutic use

AIM

Periodontal ligament (PDL) is a reliable cell source for periodontal regeneration. In this study, an optimal protocol for the extraction, expansion, and characterization of human PDL (hPDL) cells was examined for clinical trials.

MATERIALS AND METHODS

hPDL tissues were obtained from 41 surgically extracted teeth and digested with enzymes. Human adipose-derived stem cells (hADSCs), bone marrow-derived mesenchymal stem cells (hBMMSCs), and gingival fibroblasts (hGFs) were used for comparison. For each sample, the proliferative capacity, colony-forming ability, alkaline phosphatase activity, differentiation ability, the cell surface antigens, gene expression, and regenerative potential were examined.

RESULTS

hPDL cells were more successfully extracted with collagenase/dispase [29/30 (96.7%)] than with trypsin/EDTA [8/11 (72.7%)], and exhibited osteogenic potential both in vitro and in vivo. The proliferation of hPDL cells was rapid at a low cell density. hPDL cells frequently differentiated into cementoblastic/osteoblastic lineage (∼60%). In contrast, their adipogenic and chondrogenic potentials were lower than those of hADSCs and hBMMSCs. Some genes (NCAM1, S100A4, and periostin) were preferentially expressed in hPDL cells compared with those of hBMMSCs and hGFs. Immunohistochemical studies revealed the expressions of S100A4 and periostin in hPDL tissue.

CONCLUSION

A protocol for the successful cultivation and validation of hPDL cells is proposed for clinical settings.

Characteristics of high-molecular-weight hyaluronic acid as a brain-derived neurotrophic factor scaffold in periodontal tissue regeneration

Brain-derived neurotrophic factor (BDNF), for which bovine collagen-derived atelocollagen is used as a scaffold, enhances periodontal tissue regeneration. However, a scaffold that does not contain unknown ingredients is preferable. Since the synthesized high-molecular-weight (HMW)-hyaluronic acid (HA) is safe and inexpensive, we evaluated the efficacy of HMW-HA as a BDNF scaffold. CD44, a major receptor of HA, was expressed in cultures of human periodontal ligament cells, and HMW-HA promoted the adhesion and proliferation of human periodontal ligament cells, although it did not influence the mRNA expression of bone (cementum)-related proteins. The in vitro release kinetics of BDNF from HMW-HA showed that BDNF release was sustained for 14 days. Subsequently, we examined the effect of BDNF/HMW-HA complex on periodontal tissue regeneration in dogs. A greater volume of newly formed alveolar bone and a longer newly formed cementum were observed in the BDNF/HMW-HA group than in the HMW-HA group, suggesting that HMW-HA assists the regenerative capacity of BDNF, although HMW-HA itself does not enhance periodontal tissue regeneration. Neither the poly (lactic-co-glycolic acid) group nor the BDNF/poly (lactic-co-glycolic acid) group enhanced periodontal tissue regeneration. In conclusion, HMW-HA is an adequate scaffold for the clinical application of BDNF.

Characterization of stem cells from alveolar periodontal ligament

Complete and predicable regeneration of complex periodontal structures, which include cementum, periodontal ligament (PDL), and alveolar bone, has been a great challenge for periodontal researchers. It is generally believed that human PDL from the root surface contains stem cells (r-PDLSCs), which can enhance cementum/PDL-like tissues regeneration in vivo. In this work, PDL was found to possess asymmetrically distributed stem cells observed by long-term bromodeoxyuridine (BrdU) labeling. Putative stem cells from human PDL on the alveolar bone surface (a-PDLSCs) were then isolated and characterized. It was shown that a-PDLSCs exhibited strong proliferation capability and expressed high percentages of mesenchymal stem cell markers. Comparatively, a-PDLSCs had higher multilineage differentiation potential than r-PDLSCs with regard to both osteogenic and adipogenic differentiation. Alkaline phosphatase activity and the expression of mineralization-related markers of a-PDLSCs were also higher than those of r-PDLSCs. In vivo, a-PDLSCs could regenerate bone/PDL-like structures and repair critical-size defects created in calvarial bone of NOD/SCID mice. Autologous PDLSC-mediated periodontal regeneration showed that a-PDLSCs could accomplish reconstruction of alveolar bone more perfectly than r-PDLSCs. Our data suggest that PDLSCs may have quite different characteristics depending on locations. a-PDLSCs may take a synergistic effect with r-PDLSCs in periodontal regeneration.

Comparison of characteristics of periodontal ligament cells obtained from outgrowth and enzyme-digested culture methods

OBJECTIVE

Periodontal ligament (PDL) cells have an important role in periodontal regeneration. The unique characteristics of PDL cells, mainly outgrown cells derived from PDL tissue, have been investigated. Recently, mesenchymal stem cells have been obtained from PDL tissue using enzyme digestion. The differences in properties of those PDL cells cultured by the two methods (outgrowth and enzyme digestion) are unclear. The objective of this study was to investigate the characteristics of PDL cells obtained by these methods.

METHODS

PDL cells from extracted tooth were cultured using outgrowth and enzyme digest methods. Cell proliferation, colony-forming activity and differentiation capacity to osteoblast, adipocyte and chondrocyte were compared. Gene expressions for PDL cells, mesenchymal stem cells and fibroblasts were also investigated by reverse transcription polymerase chain reaction. Procollagen type I c-peptide (PIP) production was measured using an enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS

PDL cells cultured by enzyme digest methods showed a higher proliferation rate, colony-forming activity and differentiation capacity into osteoblast, adipocyte and chondrocyte than those in PDL cells by outgrowth method. CD166, one of the mesenchymal stem cell markers, was slightly higher in enzyme-digested PDL than in outgrowth PDL, whilst gene expressions for type 1 collagen alpha 1 and type 3 collagen were higher in outgrown PDL cells. Moreover, outgrowth PDL exhibited higher PIP production than enzyme-digested PDL cells.

CONCLUSION

PDL cells obtained by outgrowth and enzyme digestion showed different characteristics. The enzyme digestion method yielded cells with higher proliferation rate and mesenchymal stem cell-like properties, whereas cells with fibroblast-like properties were collected in the outgrowth method. PDL cell properties by different culture methods may provide information for inventing new therapeutic uses of PDL cells.

Oestrogen regulates proliferation, osteoblastic differentiation, collagen synthesis and periostin gene expression in human periodontal ligament cells through oestrogen receptor beta

OBJECTIVE

The present study was designed to examine how oestrogen regulates proliferation, osteoblastic differentiation, collagen synthesis and periostin gene expression in primary human periodontal ligament (hPDL) cells.

DESIGN

The short interfering RNA (siRNA) technique was used to inhibit oestrogen receptor beta (ERβ) expression hPDL cells. hPDL cell were isolated and fully characterized. A colorimetric assay was applied for the determination of alkaline phosphatase (ALP). An ELISA kit was used to detect osteocalcin (OCN) levels. Collagen synthesis was determined by measuring the incorporation of L-[3H] praline. RT-PCR was performed to detection of periostin mRNA relative gene expression.

RESULTS

ERβ mRNA was expressed in hPDL cells and significant inhibition of mRNA expression and ERβ mature protein of the ERβ was evident in the siRNA group. At 72h, there was a significant increase in non-transfected hPDL cell proliferation after estradiol stimulation. Addition of 17β-estradiol significantly enhanced ALP activity and production of OCN in non-transfected cells but had no effect on collagen synthesis. A clear increase in periostin mRNA expression levels was observed after incubating hPDL cells with estradiol. In hPDL-siERβ cells, the application of estradiol did not produce any evident differences in periostin mRNA expression

CONCLUSIONS

ERβ may play important roles in oestrogen-induced effects on hPDL cell proliferation, osteoblastic differentiation and expression of key molecules for the functional and structural integrity of the periodontium (i.e. periostin).