Isolation and characterization of fibroblasts derived from regenerating human periodontal defects

Harnessing the Native Extracellular Matrix for Periodontal Regeneration Using a Melt Electrowritten Biphasic Scaffold

Scaffolds have been used to promote periodontal regeneration by providing control over the spacio-temporal healing of the periodontium (cementum, periodontal ligament (PDL) and alveolar bone). This study proposes to enhance the biofunctionality of a biphasic scaffold for periodontal regeneration by means of cell-laid extracellular matrix (ECM) decoration. To this end, a melt electrowritten scaffold was cultured with human osteoblasts for the deposition of bone-specific ECM. In parallel, periodontal ligament cells were used to form a cell sheet, which was later combined with the bone ECM scaffold to form a biphasic PDL-bone construct. The resulting biphasic construct was decellularised to remove all cellular components while preserving the deposited matrix. Decellularisation efficacy was confirmed in vitro, before the regenerative performance of freshly decellularised constructs was compared to that of 3-months stored freeze-dried scaffolds in a rodent periodontal defect model. Four weeks post-surgery, microCT revealed similar bone formation in all groups. Histology showed higher amounts of newly formed cementum and periodontal attachment in the fresh and freeze-dried ECM functionalised scaffolds, although it did not reach statistical significance. This study demonstrated that the positive effect of ECM decoration was preserved after freeze-drying and storing the construct for 3 months, which has important implications for clinical translation.

Synthesis and Modification of Gelatin Methacryloyl (GelMA) with Antibacterial Quaternary Groups and Its Potential for Periodontal Applications

Gelatin methacryloyl (GelMA) hydrogels have been widely used for different biomedical applications due to their tunable physical characteristics and appropriate biological properties. In addition, GelMA could be modified with the addition of functional groups providing inherent antibacterial capabilities. Here, GelMA-based hydrogels were developed through the combination of a GelMA unmodified and modified polymer with quaternary ammonium groups (GelMAQ). The GelMAQ was synthesized from GelMA with a low degree of substitution of methacrylamide groups (DSMA) and grafted with glycidyltrimethylammonium chloride in the free amine groups of the lysine moieties present in the original gelatin. GelMAs with high DSMA and GelMAQ were combined 50/50% or 25/75% (w/w), respectively, and compared to controls GelMA and GelMA with added chlorhexidine (CHX) at 0.2%. The different hydrogels were characterized using 1H-NMR spectroscopy and swelling behavior and tested in (1) Porphyromonas gingivalis to evaluate their antibacterial properties and (2) human gingival fibroblast to evaluate their cell biocompatibility and regenerative properties. GelMA/GelMAQ 25/75% showed good antibacterial properties but also excellent biocompatibility and regenerative properties toward human fibroblasts in the wound healing assay. Taken together, these results suggest that the modification of GelMA with quaternary groups could facilitate periodontal tissue regeneration, with good biocompatibility and added antibacterial properties.

Evaluation of Platelet-Derived Extracellular Vesicles in Gingival Fibroblasts and Keratinocytes for Periodontal Applications

Gingival regeneration aims at restoring the architecture and functionality of oral damaged tissue. Different biomaterials or biological materials have been tested for tissue repair, such as platelet concentrates such as PL. In this article, the use of extracellular vesicles (EVs) derived from platelet lysate (PL) and their combination with hyaluronic acid biomaterials (HA) in an in vitro wound healing assay is investigated. EVs were isolated by size exclusion chromatography from PL. In addition, HA gels were formulated with PL or EVs. EVs or HA combined with EVs (HA-EVs) were tested in vitro in gingival fibroblasts and keratinocytes for biocompatibility (LDH activity and metabolic activity) and by an in vitro wound-healing assay and gene expression analysis. EVs and EVs-HA treatments were biocompatible in gingival fibroblasts and keratinocytes and showed an increase in wound healing in vitro compared to control. Moreover, changes in gene expression related to extracellular matrix remodeling were observed after the treatment with EVs. EVs can be combined with HA biomaterials, showing good biocompatibility and preserving their activity and functionality. Therefore, platelet-derived EVs could emerge as a new application for periodontal regeneration in combination with biomaterials in order to enhance their clinical use.

Stem Cell Applications in Periodontal Regeneration

In this review, the authors consider the substantial advances that have been made in recent years in stem cell-based periodontal regeneration. These advances involve identifying dental- and nondental-derived stem cells with the capacity to modulate periodontal regeneration, human clinical trials, and emerging concepts, including cell banking, good manufacturing processes, and overall clinical translation.

Influence of sterilization on the performance of anodized nanoporous titanium implants

Towards clinical translation of bioactive nano-engineered titanium implants, achieving appropriate sterilization and understanding its influence on the modified implant characteristics is essential. With limited studies exploring the influence of sterilization techniques on electrochemically anodized titanium with TiO₂ nanostructures, we aimed to advance this domain by performing an in-depth evaluation of the influence of common sterilization techniques (ethanol immersion, various UV irradiation times, gamma irradiation, and dry/wet autoclaving) on TiO₂ nanopores fabricated on micro-rough Ti surfaces (dual micro-nano) via single step anodization. Various sterilized surfaces were systematically compared in terms of topographical, chemical, crystalline, wettability and mechanical characteristics. Next, we investigated the protein adhesion capacity and functions of primary gingival fibroblasts (proliferation, adhesion/alignment and spreading morphology) to compare the bioactivity of the sterilized nanopores. Ethanol immersion, gamma irradiation and UV irradiation conserved the topography of the fabricated nanopores, while autoclave sterilization (both dry and wet) compromised the nanoporous structures. Various duration of UV-sterilization resulted in no significant changes in the surface topography and chemistry of the fabricated TNPs. Our findings revealed that UV irradiation is the most appropriate technique to sterilize nano-engineered titanium implants for appropriate wettability, protein adhesion capacity and enhanced metabolism and proliferation of human gingival fibroblasts (hGFs). This study systematically investigated the influence of sterilization on anodized nano-engineered titanium implants towards achieving reproducible outcomes (in terms of topography, chemistry and bioactivity), and found that UV irradiation holds great promise for application across different nano-engineered metal surfaces.

Comparative Evaluation of Cytotoxic and Genotoxic Effects of Three Resin-Based Sealers by 3,(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide Assay and Comet Assay - An In Vitro Study

Background and Aim

The complete sealing of the pulpal space contributes to the better healing potential after an root canal treatment, and root canal sealers are an integral part of this treatment which comes in contact with the periodontal tissue. Biocompatibility of an endodontic sealer plays an important role in the root canal treatment procedure. Hence, the aim of the study was to compare and evaluate the cytotoxicity and genotoxicity effect of three resin-based sealers on human periodontal fibroblast cells.

Settings and Design

This in vitro study was conducted in Dr. Prabhakar Kore's Basic Science and Research Center and K. L. E V. K. Institute of Dental Sciences, Belagavi.

Materials and Methods

Human periodontal fibroblasts were incubated with 15 specimens of Group 1 - AH Plus Group 2 - MTA Fillapex, and Group 3 - GuttaFlow 2, respectively. Cytotoxicity was assessed by 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and genotoxicity was assessed by Comet assay at time intervals at 24 h and 48 h.

Statistical Analysis

Data were analyzed by the Kruskal-Wallis and Mann-Whitney U-test.

Results

AH Plus and GuttaFlow 2 did not show any cytotoxicity or genotoxicity. MTA Fillapex was slightly cytotoxic throughout the time interval, and it also showed low genotoxicity throughout the time periods for which it was tested.

Conclusion

AH Plus and GuttaFlow 2 did not show any cytotoxic and genotoxic effect; however, MTA Fillapex showed cytotoxic and genotoxic effect throughout the time interval.

Comparative In Vitro Evaluation of Commercial Periodontal Gels on Antibacterial, Biocompatibility and Wound Healing Ability

In the last years, several studies testing commercial periodontal gels that contain chlorhexidine (CHX) or other antibacterial agents, have raised concerns regarding their cytotoxicity in periodontal tissues. We aimed at comparing the biocompatibility but also the efficacy as regards to the antibacterial and wound healing ability of different commercial periodontal gels. In vitro human gingival fibroblasts (GF) and a 3D model of human tissue equivalents of gingiva (GTE) were used under inflammatory conditions to evaluate wound closure, cytotoxicity and gene expression. Antibacterial effects were also investigated on Porphyromonas gingivalis growth, viability and gingipain activity. In GF and in the bacterial study, we found cytotoxic effects on GF and a high inhibition on bacterial growth rate in gels containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol. Of the two gels that were non-cytotoxic, Syntoss Biogel (containing chondrontin sulfate) and Emdogain (EMD, containing amelogenin and propylene glycol alginate), EMD showed the best wound closure, with no effect on P. gingivalis growth but decreased gingipain activity. On the other hand, Syntoss Biogel reduced viability and gingipain activity of P. gingivalis, but lack wound healing capacity. In the 3D GTE, Syntoss Biogel and EMD showed a good biocompatibility. Among all the tested gels, formulations containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol showed high antibacterial effect but also showed high cytotoxicity in eukaryotic cells. EMD was the one with the best biocompatibility and wound healing ability at the conditions tested.

Old is Gold: Electrolyte Aging Influences the Topography, Chemistry, and Bioactivity of Anodized TiO2 Nanopores

Titanium dioxide (TiO₂) nanostructures including nanopores and nanotubes have been fabricated on titanium (Ti)-based orthopedic/dental implants via electrochemical anodization (EA) to enable local drug release and enhanced bioactivity. EA using organic electrolytes such as ethylene glycol often requires aging (repeated anodization of nontarget Ti) to fabricate stable well-ordered nanotopographies. However, limited information is available with respect to its influence on topography, chemistry, mechanical stability, and bioactivity of the fabricated structures. In the current study, titania nanopores (TNPs) using a similar voltage/time were fabricated using different ages of electrolyte (fresh/0 h to 30 h aged). Current density vs time plots of EA, changes in the electrolyte (pH, conductivity, and Ti/F ion concentration), and topographical, chemical, and mechanical characteristics of the fabricated TNPs were compared. EA using 10-20 h electrolytes resulted in stable TNPs with uniform size and improved alignment (parallel to the underlying substrate microroughness). Additionally, to evaluate bioactivity, primary human gingival fibroblasts (hGFs) were cultured onto various TNPs in vitro. The findings confirmed that the proliferation and morphology of hGFs were enhanced on 10-20 h aged electrolyte anodized TNPs. This pioneering study systematically investigates the optimization of anodization electrolyte toward fabricating nanoporous implants with desirable characteristics.

Electrospun Nanofibrous Poly (Lactic Acid)/Titanium Dioxide Nanocomposite Membranes for Cutaneous Scar Minimization

Poly (lactic acid) (PLA) has been increasingly used in cutaneous tissue engineering due to its low cost, ease of handling, biodegradability, and biocompatibility, as well as its ability to form composites. However, these polymers possess a structure with nanoporous that mimic the cellular environment. In this study, nanocomposites are prepared using PLA and titanium dioxide (TiO2) (10 and 35%-w/w) nanoparticles that also function as an active anti-scarring agent. The nanocomposites were prepared using an electrospinning technique. Three different solutions were prepared as follows: PLA, 10% PLA/TiO2, and 35% PLA/TiO2 (w/w%). Electrospun PLA and PLA/TiO2 nanocomposites were characterized morphologically, structurally, and chemically using electron scanning microscopy, transmission electron microscopy, goniometry, and X-ray diffraction. L929 fibroblast cells were used for in vitro tests. The cytotoxic effect was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Versicam (VCAN), biglicam (BIG), interleukin-6 (IL6), interleukin-10 (IL-10), and type-1 collagen (COL1A1) genes were evaluated by RT-qPCR. In vivo tests using Wistar rats were conducted for up to 15 days. Nanofibrous fibers were obtained for all groups that did not contain residual solvents. No cytotoxic effects were observed for up to 168 h. The genes expressed showed the highest values of versican and collagen-1 (p < 0.05) for PLA/TiO2 nanocomposite scaffolds when compared to the control group (cells). Histological images showed that PLA at 10 and 35% w/w led to a discrete inflammatory infiltration and expression of many newly formed vessels, indicating increased metabolic activity of this tissue. To summarize, this study supported the potential of PLA/TiO2 nanocomposites ability to reduce cutaneous scarring in scaffolds.

The effect of decellularized tissue engineered constructs on periodontal regeneration

AIM

To evaluate the effect of decellularized tissue engineered constructs on cell differentiation in vitro and periodontal regeneration in vivo.

MATERIALS AND METHODS

Periodontal ligament cell (PDLC) sheets were loaded on polycaprolactone (PCL) scaffolds and then decellularized. Constructs were assessed for their effect on allogenic PDLC and mesenchymal stem cell (MSC) differentiation in vitro, as evaluated by gene expression of bone and periodontal ligament tissue markers post-seeding. Expression of MSC marker STRO-1 was assessed by immunostaining. Decellularized constructs were evaluated in a rat periodontal defect model to assess their biocompatibility and tissue integration. Microcomputed topography (μCT) and histological assessment were performed to assess the regenerative potential of the constructs at 2 and 4 weeks postoperatively.

RESULTS

There was upregulation of bone marker gene expression by PDLCs especially on the 14th day. MSCs lacked bone markers expression, but showed increased collagen I marker expression on day 14. STRO-1 expression by the MSCs decreased over the three timepoints when seeded on decellularized sheets. Histological assessment demonstrated the biocompatibility of the decellularized constructs in vivo. More new attachment formation was observed on the decellularized constructs compared to scaffold only controls.

CONCLUSION

Decellularized tissue engineered constructs are capable of inducing cell differentiation in vitro and have the potential to facilitate periodontal regeneration in vivo.

Effect of follicular dendritic cell secreted protein on gene expression of human periodontal ligament cells

OBJECTIVE

The objective of this study was to investigate the specific roles of follicular dendritic cell secreted protein (FDC-SP), a protein exists in saliva, in the inhibition of calcium precipitation during periodontal regeneration, as well as affect phenotype expression of human periodontal ligament cells (hPDLCs) during the differentiation process.

DESIGN

To investigate this, we applied microarray technology to identify gene expression changes in hPDLCs transfected with FDC-SP and then clustered them according to their biological functions.

RESULTS

One hundred seventy-one genes were found differentially expressed by at least two-fold between FDC-SP -transfected and empty vector-transfected cells. Besides, genes encoding cell-cycle proteins, blood-related and cell differentiation-related proteins tended to be up-regulated after FDC-SP transfection, whereas cytokine/growth factors, signal transduction and metabolism-related genes tended to be down-regulated in hPDLCs overexpression FDC-SP.

CONCLUSIONS

The present study investigated FDC-SP's roles in hPDLCs' phenotype expression, via comparing the gene expression profiles between FDC-SP -transfected hPDLCs and empty vector-transfected cells upon microarray analysis. hPDLCs overexpression FDC-SP appear to display different gene expression patterns. In all, these observations showed a potential of FDC-SP in the maintenance of PDL homeostasis and its ultimate contribution to periodontal would-healing processes.

Multiple functions of gingival and mucoperiosteal fibroblasts in oral wound healing and repair

Fibroblasts are cells of mesenchymal origin. They are responsible for the production of most extracellular matrix in connective tissues and are essential for wound healing and repair. In recent years, it has become clear that fibroblasts from different tissues have various distinct traits. Moreover, wounds in the oral cavity heal under very special environmental conditions compared with skin wounds. Here, we reviewed the current literature on the various interconnected functions of gingival and mucoperiosteal fibroblasts during the repair of oral wounds. The MEDLINE database was searched with the following terms: (gingival OR mucoperiosteal) AND fibroblast AND (wound healing OR repair). The data gathered were used to compare oral fibroblasts with fibroblasts from other tissues in terms of their regulation and function during wound healing. Specifically, we sought answers to the following questions: (i) what is the role of oral fibroblasts in the inflammatory response in acute wounds; (ii) how do growth factors control the function of oral fibroblasts during wound healing; (iii) how do oral fibroblasts produce, remodel and interact with extracellular matrix in healing wounds; (iv) how do oral fibroblasts respond to mechanical stress; and (v) how does aging affect the fetal-like responses and functions of oral fibroblasts? The current state of research indicates that oral fibroblasts possess unique characteristics and tightly controlled specific functions in wound healing and repair. This information is essential for developing new strategies to control the intraoral wound-healing processes of the individual patient.

A Method to Isolate, Purify, and Characterize Human Periodontal Ligament Stem Cells

Human periodontal ligament stem cells (PDLSCs) are a unique population of mesenchymal stem cells (MSCs) that demonstrate the capacity to generate cementum- and periodontal ligament-like structures in vivo. As such, PDLSCs represent a promising cell-based therapy in reconstructive dentistry for the treatment of periodontal disease. The present chapter describes two methods for isolating PDLSCs from human PDL tissue including traditional plastic adherence, and immunomagnetic selection based on the expression of MSC-associated surface markers STRO-1 antigen, CD146 (MUC-18), CD29 (Integrin β-1), CD44, and CD106 (VCAM-1). Although no single antibody demonstrates specificity for MSCs, isolation based on expression of individual markers results in homogenous preparations of PDLSCs. Methods to further characterize the immunophenotype and multipotent capacity of PDLSCs to differentiate into adipocytes, osteoblast-, and cementoblast-like cells in vitro, and cementum- and periodontal ligament-like tissues in vivo, are also described.

Non-thermal atmospheric pressure plasma increased mRNA expression of growth factors in human gingival fibroblasts

OBJECTIVES

The aim of this in vitro study was to investigate the effects of a non-thermal atmospheric pressure plasma jet (NTAPPJ) on the cellular activity of human gingival fibroblasts (HGF) for possible non-surgical application of it during gingival wound healing.

MATERIALS AND METHODS

HGF cells were exposed with NTAPPJ for 1, 2, and 4 min and were investigated for cellular attachment, cell viability, morphology of attached cells, proliferation rate, and messenger ribonucleic acid (mRNA) expression of various growth factors. Also, scavengers for chemicals produced by NTAPPJ were used to identify the chemical species responsible for the effects.

RESULTS

There was no significant change in the number of HGF cells attached or their proliferation following NTAPPJ exposure. Also, high cell viability resulted from exposure of all of HGF cells to NTAPPJ for 1, 2, and 4 min. However, cells were more stretched while the mRNA expressions of transforming growth factor and vascular endothelial growth factor were significantly increased following NTAPPJ exposure. Additionally, the scavenger test showed that nitric oxide is likely to be the chemical responsible for an increase of cellular activity.

CONCLUSION

The results demonstrated that the NTAPPJ increased mRNA expressions of growth factors in human gingival fibroblasts.

CLINICAL RELEVANCE

Application of NTAPPJ would be useful in gingival wound healing in clinics though additional studies confirming the effects would be needed.

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.

What is the Best Root Surface Treatment for Avulsed Teeth?

Dental avulsion is the most severe type of traumatic tooth injuries since it causes damage to several structures and results in avulsion of the tooth from its socket. Management protocols for avulsed teeth should include management of the pulp and periodontal ligament (PDL) cells in order to improve the long-term prognosis and survival of these teeth. The prognosis of the treatment as well as the survival of an avulsed tooth depends on intrinsic and extrinsic factors, such as the duration of the tooth's extra-alveolar period, replantation time, the type of storage medium, PDL status and duration of splinting. Recent research has led to the development of storage media. However, there is not yet a single solution that fulfills all requirements to be considered as the ideal medium for temporary storage of avulsed teeth, and research on this field should carry on. On the other hand in case of delayed replantation, due to the great risk of tooth loss after avulsion, different root surface treatments have been proposed to prevent and delay root resorption before replantation. For this purpose, researchers have applied some different root surface treatment modalities in delayed replantation of avulsed teeth. Several protocols have been used to maintain PDL viability; some involve fluorides, steroids, sodium alendronate, enamel matrix derivatives (EMD) and basic fibroblast growth factor (bFGF, FGF-2). Among these applications, bFGF shows promising results in the regeneration of natural tooth structures and tissues. Better understanding of mechanism of bFGF may help to improve new technologies of regeneration of tooth structures.

Zoledronic acid and geranylgeraniol regulate cellular behaviour and angiogenic gene expression in human gingival fibroblasts

The mevalonate pathway (MVP) and the anti-angiogenic effect of bisphosphonates have been shown to play a role in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). This study determined the effect of the bisphosphonate, zoledronic acid and the replenishment of the MVP by geranylgeraniol on human gingival fibroblasts. Cell viability, apoptosis, morphological analysis using transmission electron microscopy, and gene expression for vascular endothelial growth factor A, bone morphogenic protein 2, ras homologue gene family member B, epiregulin and interferon-alpha were conducted. Results showed cellular viability was decreased in the presence of zoledronic acid and the co-addition of zoledronic acid with geranylgeraniol restored cell viability to control levels. Caspase 3/7 was detected in zoledronic-acid-treated cells indicating apoptosis. Transmission electron microscopy revealed dilation of the rough endoplasmic reticulum with zoledronic acid and the appearance of multiple lipid-like vesicles following the addition of geranylgeraniol. Zoledronic acid significantly (P < 0.05, FR > ± 2) up-regulated vascular endothelial growth factor A, bone morphogenic protein 2, ras homologue gene family member B and epiregulin at one or more time points but not interferon-alpha. Addition of geranylgeraniol resulted in a reduction in the expression of all five genes compared with zoledronic-acid-treated human gingival fibroblasts. The study concluded geranylgeraniol partially reversed the effects of zoledronic acid in human gingival fibroblasts both at the cellular and genetic levels, suggesting the regulation of these genes is mediated via the mevalonate pathway.

bFGF-induced human periodontal ligament fibroblasts proliferation through T-type voltage-dependent calcium channels

OBJECTIVE

To test the hypothesis that T-type voltage-dependent calcium channels (T-CaCNs) are involved in basic fibroblast growth factor (bFGF)-induced proliferation of human periodontal ligament fibroblasts (HPLFs).

MATERIALS AND METHODS

This study examined the expression of the T-type calcium channel sub-units Ca(V) 3.1, Ca(V) 3.2 and Ca(V) 3.3 in HPLFs by real-time PCR. Mibefradil, a T-CaCNs antagonist, was used to block the effect of T-CaCNs and the proliferation of HPLFs was evaluated by the water-soluble tetrazolium (WST) assay. The level of intracellular calcium was measured by laser confocal microscopy.

RESULTS

Expression of the three subunits of T-CaCNs in HPLFs was detected, which was strongly up-regulated upon stimulation by bFGF. The proliferation of HPLFs induced by bFGF was decreased significantly by treatment with Mibefradil. This effect was associated with the decreased expression of T-CaCNs and a decreased level of intracellular calcium.

CONCLUSIONS

Expression of the T-CaCNs affected the proliferation of HPLFs that was induced by bFGF, indicating that T-CaCNs could be important in mediating periodontal ligament (PDL) remodeling.

Periradicular Tissue Responses to Biologically Active Molecules or MTA When Applied in Furcal Perforation of Dogs' Teeth

The aim of this study was the comparative evaluation of inflammatory reactions and tissue responses to four growth factors, or mineral trioxide aggregate (MTA), or a zinc-oxide-eugenol-based cement (IRM) as controls, when used for the repair of furcal perforations in dogs' teeth. Results showed significantly higher inflammatory cell response in the transforming growth factorβ1 (TGFβ1) and zinc-oxide-eugenol-based cement (IRM) groups and higher rates of epithelial proliferation in the TGFβ1, basic fibroblast growth factor (bFGF), and insulin growth factor-I (IGF-I) groups compared to the MTA. Significantly higher rates of bone formation were found in the control groups compared to the osteogenic protein-1 (OP-1). Significantly higher rates of cementum formation were observed in the IGF-I and bFGF groups compared to the IRM. None of the biologically active molecules can be suggested for repairing furcal perforations, despite the fact that growth factors exerted a clear stimulatory effect on cementum formation and inhibited collagen capsule formation. MTA exhibited better results than the growth factors.

A method to isolate, purify, and characterize human periodontal ligament stem cells

Human periodontal ligament stem cells (PDLSCs) are a unique population of mesenchymal stem cells (MSCs) which demonstrate the capacity to generate cementum- and periodontal ligament-like structures in vivo. As such, PDLSCs represent a promising cell-based therapy in reconstructive dentistry for the treatment of periodontal disease. The present chapter describes two methods for isolating PDLSCs from human PDL tissue including traditional plastic adherence and immunomagnetic selection based on the expression of MSC-associated surface markers STRO-1 antigen, CD146 (MUC-18), CD29 (integrin beta-1), CD44, and CD106 (VCAM-1). Although no single antibody demonstrates specificity for MSCs, isolation based on the expression of individual markers results in homogeneous preparations of PDLSCs. Methods to further characterize the immunophenotype and multipotent capacity of PDLSCs to differentiate into adipocytes, osteoblast- and cementoblast-like cells in vitro, and cementum- and periodontal ligament-like tissues in vivo are also described.

Guided tissue regeneration may modulate gene expression in periodontal intrabony defects: a human study

BACKGROUND AND OBJECTIVE

Guided tissue regeneration has been shown to lead to periodontal regeneration, however, the mechanisms involved remain to be clarified. The present study was carried out to assess the expression of genes involved in the healing process of periodontal tissues in membrane-protected vs. nonprotected intrabony defects in humans.

MATERIAL AND METHODS

Thirty patients with deep intrabony defects (> or = 5 mm, two or three walls) around teeth that were scheduled for extraction were selected and randomly assigned to receive one of the following treatments: flap surgery alone (control group) or flap surgery plus guided tissue regeneration (expanded polytetrafluorethylene (e-PTFE) membrane) (test group). Twenty-one days later, the newly formed tissue was harvested and quantitatively assessed using the polymerase chain reaction assay for the expression of the following genes: alkaline phosphatase, receptor activator of nuclear factor-kappa B ligand, osteoprotegerin, osteopontin, osteocalcin, bone sialoprotein, basic fibroblast growth factor, interleukin-1, interleukin-4, interleukin-6, matrix metalloproteinase-2 and matrix metalloproteinase-9.

RESULTS

Data analysis demonstrated that mRNA levels for alkaline phosphatase, receptor activator of nuclear factor-kappa B ligand, osteoprotegerin, osteopontin, bone sialoprotein, basic fibroblast growth factor, interleukin-1, interleukin-6, matrix metalloproteinase-2 and matrix metalloproteinase -9 were higher in the sites where guided tissue regeneration was applied compared with the control sites (p < 0.05), whereas osteocalcin mRNA levels were lower (p < 0.05). No difference was observed in interleukin-4 mRNA levels between control and test groups.

CONCLUSION

Within the limits of this study, it can be concluded that genes are differentially expressed in membrane barrier-led periodontal healing when compared with flap surgery alone, and this may account for the clinical outcome achieved by guided tissue regeneration.

Occlusal stimuli influence on the expression of IGF-1 and the IGF-1 receptor in the rat periodontal ligament

OBJECTIVE

To test the hypothesis that hypofunction/recovered occlusal function has no effect on the changes in insulin-like growth factor-1 (IGF-1) and IGF-1 receptor expressions and cell proliferation of periodontal ligament (PDL) cells.

MATERIALS AND METHODS

To produce occlusal hypofunction, the appliances were attached to the rats' maxillary and mandibular incisors. Subsequently, occlusal contact of the molar area was thoroughly recovered by removal of the appliances.

RESULTS

In periodontal sections, localization of IGF-1, the IGF-1 receptor, and proliferating cell nuclear antigen (PCNA) immunoreactive cells was significantly more expressed in the control group compared with the hypofunctional group (P < .01). In addition, after the recovery of the occlusion, IGF-1, IGF-1 receptor, and PCNA were detected significantly much more than in the hypofunction group (P < .01).

CONCLUSION

The hypothesis was rejected. This study suggests that occlusal stimuli induce cell proliferation of PDL cells by increasing IGF-1 and IGF-1 receptor expression.

Putative stem cells in regenerating human periodontium

BACKGROUND AND OBJECTIVE

Human postnatal stem cells have been identified in periodontal ligament, with the potential to regenerate the periodontium in vivo. However, it is unclear if periodontal ligament stem cells are present in regenerating periodontal tissues. The aim of this study was to identify and localize putative stem cells in block biopsies and explant cultures of regenerating human periodontal tissues.

MATERIAL AND METHODS

Guided tissue regeneration was carried out on the molars of three human volunteers. After 6 wk, the teeth with the surrounding regenerating tissues and bone were surgically removed and processed for immunohistochemistry. The mesenchymal stem cell-associated markers STRO-1, CD146 and CD44 were used to identify putative stem cells. Cell cultures established from regenerating tissue explants were analysed by flow cytometry to assess the expression of these markers. Mineralization, calcium concentration and adipogenic potential of regenerating tissue cells were assessed and compared with periodontal ligament stem cells, bone marrow stromal stem cells and gingival fibroblasts.

RESULTS

STRO-1(+), CD44(+) and CD146(+) cells were identified in the regenerating tissues. They were found mainly in the paravascular and extravascular regions. Flow cytometry revealed that cultured regenerating tissue cells expressed all three mesenchymal stem cell associated markers. The regenerating tissue cells were able to form mineral deposits and lipid-containing adipocytes. However, the level of mineralization in these cells was lower than that of periodontal ligament stem cells and bone marrow stromal stem cells.

CONCLUSION

Cells with characteristics of putative mesenchymal stem cells were found in regenerating periodontal tissues, implying their involvement in periodontal regeneration.

Stem cells and tooth tissue engineering

The notion that teeth contain stem cells is based on the well-known repairing ability of dentin after injury. Dental stem cells have been isolated according to their anatomical locations, colony-forming ability, expression of stem cell markers, and regeneration of pulp/dentin structures in vivo. These dental-derived stem cells are currently under increasing investigation as sources for tooth regeneration and repair. Further attempts with bone marrow mesenchymal stem cells and embryonic stem cells have demonstrated the possibility of creating teeth from non-dental stem cells by imitating embryonic development mechanisms. Although, as in tissue engineering of other organs, many challenges remain, stem-cell-based tissue engineering of teeth could be a choice for the replacement of missing teeth in the future.

Effects of enamel matrix derivative and transforming growth factor-beta1 on human periodontal ligament fibroblasts

AIM

The objective of this study was to evaluate the effects of enamel matrix derivative (EMD), transforming growth factor-beta1 (TGF-beta1), and a combination of both factors (EMD+TGF-beta1) on periodontal ligament (PDL) fibroblasts.

MATERIAL AND METHODS

Human PDL fibroblasts were obtained from three adult patients with a clinically healthy periodontium, using the explant technique. The effects of EMD, TGF-beta1, or a combination of both were analysed on PDL cell proliferation, adhesion, wound healing, and total protein synthesis, and on alkaline phosphatase (ALP) activity and bone-like nodule formation.

RESULTS

Treatment with EMD for 4, 7, and 10 days increased cell proliferation significantly compared with the negative control (p<0.05). At day 10, EMD and EMD+TGF-beta1 showed a higher cell proliferation compared with TGF-beta1 (p<0.01). Cell adhesion was significantly up-regulated by TGF-beta1 compared with EMD and EMD+TGF-beta1 (p<0.01). EMD enhanced in vitro wound healing of PDL cells compared with the other treatments. Total protein synthesis was significantly increased in PDL cells cultured with EMD compared with PDL cells treated with TGF-beta1 or EMD+TGF-beta1 (p<0.05). EMD induced ALP activity in PDL fibroblasts, which was associated with an increase of bone-like nodules.

CONCLUSION

These findings support the hypothesis that EMD and TGF-beta1 may play an important role in periodontal regeneration. EMD induced PDL fibroblast proliferation and migration, total protein synthesis, ALP activity, and mineralization, while TGF-beta1 increased cellular adhesion. However, the combination of both factors did not positively alter PDL fibroblast behaviour.

Gene expression profiling of cells involved in periodontal regeneration

Understanding the molecular mechanisms involved in periodontal regeneration is important for the development of more predictable clinical techniques. This study aimed to identify these mechanisms by comparing the gene expression profiles of cells derived from regenerating defects with patient-matched periodontal ligament cells. Gene profiling was carried out via Affymetrix U133A arrays containing probes for 22,000 genes. Robust differences in gene expression were obtained by identifying genes that consistently changed by a minimum of 2-fold. Analysis of molecular function as designated by gene ontology (GO) identified differentially regulated mechanisms including protein metabolism, tyrosine kinase activity, and skeletal development. The differentially expressed genes could be broadly divided into the categories of protein biosynthesis and turnover, structural constituents of the cytoskeleton and extracellular matrix, and signal transduction. The differential expression of 4 genes (EGR-1, elastin, osteoprotegerin, and IGFBP3) was confirmed via real-time polymerase chain reaction (PCR). Further, the expression of another 2 differentially expressed transcripts, decorin and biglycan, was immunohistochemically confirmed in a periodontal wound healing model and the protein expression was consistent with the pattern of gene expression. This study gives insight into the molecular processes involved in periodontal regeneration and identifies cell markers that are characteristic of regenerating periodontal tissues.

In vitro models of periodontal cells: a comparative study of long-term gingival, periodontal ligament and alveolar bone cell cultures in the presence of beta-glycerophosphate and dexamethasone

Human gingival (HG), periodontal ligament (HPL) and alveolar bone (HAB) cells (first subculture) were cultured (10(4) cells/cm2) for 35 days in alpha-Minimal Essential Medium supplemented with 10% fetal bovine serum in the presence of (i) ascorbic acid (AA, 50 microg/mL), (ii) AA + beta-glycerophosphate (betaGP, 10 mM) and (iii) AA + betaGP + dexamethasone (Dex, 10 nM). Cultures were assessed for cell attachment and spreading, cell proliferation, alkaline phosphatase (ALP) and acid phosphatase (ACP) activities and matrix mineralization. HG cell cultures presented a high proliferation rate, a low ability to synthesize ALP and ACP and the formation of a non-mineralized extracellular matrix, regardless the experimental situation. HPL cell cultures were very sensitive to the culture conditions and showed a high proliferation rate, synthesis of moderate levels of ALP and ACP and a modest matrix mineralization in the presence of AA + betaGP + Dex. HAB cell cultures presented a growth rate lower than that of HG and HPL cells, a high ALP activity and comparatively low levels of ACP, and the ready formation of a heavy mineralized matrix in the presence of betaGP. In the three periodontal cell cultures, Dex enhanced cell proliferation and expression of osteoblastic markers. Results showed that betaGP and Dex allowed the modulation of the cell proliferation/differentiation behavior within the proposed physiological and regenerative capabilities of these periodontal cells.

Role of growth factors on periodontal repair

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis and differentiation of cells from epithelium, bone and connective tissue. They express their action by binding to specific cell-surface receptors present on various target cells including osteoblasts, cementoblasts and periodontal ligament fibroblasts. The observation that growth factors participate in all cell functions led to exogenous application during periodontal tissue repair aiming to their use as an alternative therapeutic approach to periodontal therapy. Cell types and cultures conditions, dose, carrier materials, application requirements are of critical importance in the outcome of periodontal repair. The purpose of this article is to review the literature with respect to the biological actions of PDGF, TGF, FGF, IGF and EGF on periodontal cells and tissues, which are involved in periodontal regeneration.

Stem cells in the periodontal ligament

The ability to identify and manipulate stem cells has been a significant advancement in regenerative medicine and has contributed to the development of tissue engineering-based clinical therapies. Difficulties associated with achieving predictable periodontal regeneration, means that novel techniques such as tissue engineering need to be developed in order to regenerate the extensive soft and hard tissue destruction that results from periodontitis. One of the critical requirements for a tissue engineering approach is the delivery of ex vivo expanded progenitor populations or the mobilization of endogenous progenitor cells capable of proliferating and differentiating into the required tissues. By definition, stem cells fulfill these requirements and the recent identification of stem cells within the periodontal ligament represents a significant development in the progress toward predictable periodontal regeneration. In order to explore the importance of stem cells in periodontal wound healing and regeneration, this review will examine contemporary concepts in stem cell biology, the role of periodontal ligament progenitor cells in the regenerative process, recent developments in identifying periodontal stem cells and the clinical implications of these findings.

Periodontal growth factors and tissue carriers: biocompatibility and mitogenic efficacy in vitro

Clinical research has long been testing techniques of integrating biomaterials with many external factors, such as simple proteins or more complicated devices, in order to achieve the restitutio ad integrum of periodontium. This study assessed the in vitro effectiveness of platelet derivate growth factor-BB (PDGF) and insulin growth factor I (IGF); the biocompatibility of materials like Paroguide, Oclastim membranes, Gingistat sponges, Surgiplaster, and Capset; and their efficacy as carriers for the platelet derivate growth factor-BB (PDGF) and insulin growth factor I (IGF). Fibroblasts from the human periodontal ligament were incubated with growth factors free or vehiculated. Mitogenic effect was evaluated by measuring the growth rate and biocompatibility by observing cell morphology at SEM. PDGF was the most effective in stimulating cell proliferation both in solution (p < 0.001) and vehiculated (p < 0.01). Surgiplaster and Capset were more biocompatible; however, final analysis to assess their efficacy as carriers failed to disclose significant differences between experimental findings and control.

Healing and Normal Fibroblasts Exhibit Differential Proliferation, Collagen Production, α-SMA Expression, and Contraction

This study determines the differences in proliferation, collagen production, alpha-smooth muscle actin (alpha-SMA) expression, and contraction between healing and normal fibroblasts. Transected and sham-operated rat medial collateral ligaments (MCL) were used to obtain healing and normal fibroblasts, respectively. It was found that healing fibroblasts in monolayer culture proliferated 1.4-fold faster at 48 h and had 1.7-fold greater protein expression of alpha-SMA than normal fibroblasts. In addition, it was noted that the proliferation of healing fibroblasts in collagen gels was not significantly different from that of normal fibroblasts at 24 h, but it was at 48 h. Furthermore, in collagen gels, healing fibroblasts produced more type I collagen than normal fibroblasts and generated 1.6- and 1.7-fold larger contractile forces at 15 and 20 h, respectively, than their normal counterparts. Taken together, the results of this study show that healing fibroblasts possess a differential proliferation, alpha-SMA protein expression, and contraction than normal fibroblasts.

Insulin-like growth factor-I attenuates the inhibitory effect of type I collagen through β1 integrin receptor

Extracellular matrix and growth factors are the crucial factors that regulate healing and regenerating processes in human periodontal ligament cells. The purpose of this study was to examine the effects of type I collagen and insulin-like growth factor-I (IGF-I) on osteopontin (OPN) expression. The data showed that OPN expression was significantly decreased when cells were cultured on collagen-coated plates. Addition of IGF-I obviously induced OPN expression only in a collagen-coated condition, suggesting an attenuating effect of IGF-I on the decrease of OPN expression. Cells treated with a combination of inhibitory antibody to beta1 integrin and IGF-I showed the same level of OPN expression as those treated with either inhibitory antibody to beta1 integrin or IGF-I alone. These results indicate that IGF-I counteracts with the inhibitory signal from type I collagen through beta1 integrin receptor.

Role of Insulin-Like Growth Factor-1 Signaling in Dental Fibroblast Apoptosis

BACKGROUND

Studies have shown that periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) respond differently to growth factors in the repair and regeneration of periodontal tissues. The goal of this study was to determine the effects of insulin-like growth factor-1 (IGF-1) signaling on cell apoptosis in PDLF compared to GF.

METHODS

The levels of apoptosis were compared between cultured PDLF and GF by DNA fragmentation assay and trypan blue exclusion assay, either in the presence or absence of IGF-1. The transcript level of upstream signaling molecules, such as IGF binding protein-5 (IGFBP-5), IGF-1 receptor (IGF-1R), and phosphoinositide 3-kinase (PI3K), was studied using reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the role of IGFBP-5 in IGF-1 signaling was verified by annexin-V staining using flow cytometric analysis.

RESULTS

IGF-1 significantly inhibited the level of DNA fragmentation and decreased trypan blue-positive cells in PDLF compared to GF during serum deprivation. The mRNA expression of IGFBP-5, IGF-1R, and PI3K was constitutively upregulated in PDLF compared to GF. In the presence of exogenous IGFBP-5, the annexin-V-positive cells were significantly decreased in GF after IGF-1 stimulation.

CONCLUSIONS

The present study provides evidence that IGF-1 reduces apoptosis in cultured PDLF compared to GF. Upregulation of IGF-1R and PI3K in PDLF further suggests the activation of IGF signaling in PDLF. In addition, the anti-apoptotic effect of IGF-1 may be facilitated by the upregulation of IGFBP-5 in PDLF.

IGF-1 signaling enhances cell survival in periodontal ligament fibroblasts vs. gingival fibroblasts

The role of insulin-like growth factors (IGFs) in the regulation of apoptosis has been suggested, yet their impact on specific cells such as periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) remains unknown. The purpose of this study was to test the role of IGF-1 signaling in cell survival in PDLF compared with GF. In periodontal tissue sections, a significantly reduced apoptotic rate was first demonstrated in PDLF compared with GF. In vitro, IGF-1 substantially enhanced cell survival in PDLF compared with GF by the up-regulation of anti-apoptotic molecules and the down-regulation of pro-apoptotic molecules. Furthermore, the differential expression of insulin-like growth factor binding protein 5 (IGFBP-5) was observed in vitro, and its differential distribution was confirmed in vivo. Analysis of the present data suggests an enhanced cell survival in PDLF compared with GF by the up-regulation of IGF-1 signaling pathway.

Regulatory mechanisms of periodontal regeneration

The periodontal ligament, located between the cementum and the alveolar bone, has a width ranging from 0.15 to 0.38 mm. Regeneration and homeostasis of the periodontal ligament are highly significant functions in relation to periodontal therapy, tooth transplantation or replantation, and orthodontic tooth movement. The purpose of this review is to discuss the regulatory mechanisms of regenerative and homeostatic functions in the periodontal ligament based on currently published studies and also on our own experimental data. We consider the capability of the ligament tissue to promote or to suppress calcification in connection with bone and cementum formation and the maintenance of the periodontal ligament space. Also discussed are the involvement of the periodontal ligament tissue in the regenerative ability, cell proliferation, growth and differentiation factors, extracellular matrix proteins, homeostatic phenomena, function of Malassez epithelial rests, tooth movement, or occlusal loading. Regulatory mechanisms for regeneration and homeostasis of the periodontal ligament are hypothetically proposed.