Growth factors regulate expression of osteoblast-associated genes

Evaluation of the osteogenic potential of demineralized and decellularized bovine bone granules following implantation in rat calvaria critical-size defect model

The aim of this study was to compare the ability of demineralized (DMB) and decellularized (DCC) bovine bone granules to support bone regeneration in rat calvaria critical-size defects. DMB and DCC were prepared using a previously published method. The granule size used ranged between 500 and 750 μm. A total of forty-eight Sprague-Dawley rats were divided into two groups (n = 24). A pair of 5 mm diameter defects were created on the calvaria of the rats in the right and left parietal bone in both groups. Group A animals received DMB granules and Group B received DCC granules in the right parietal defect side while the left parietal untreated defect acted as sham surgery for both groups. Four animals per group were euthanized in a CO2 chamber at day 7, 14 and 21 post-surgery and the calvaria implantation site biopsy harvested was subjected to osteogenic gene expression analysis. Another four animals per group were euthanized at days 15, 30 and 60 post surgery and the calvaria implantation site biopsy harvested was subjected to histological, immunohistochemistry, RAMAN spectroscopy and Micro-CT analysis at the mentioned time points. Statistical analysis was conducted using t-tests and ANOVA. Histomorphometry showed significantly higher new bone formation in the DCC sites (p<0.05) compared to DMB. Both DMB and DCC implantation sites showed distinct staining for osteocalcin and osteopontin proteins compared to their respective sham sites. By day 21 after implantation, DCC sites demonstrated significantly elevated mRNA levels of osteonectin (p<0.001), osteopontin (p<0.001), osteocalcin (p<0.0001), ALP (p<0.01), and BMP-2 (p<0.001) compared to DMB. However, VEGF expression showed no significant differences at this time point between the two groups. Micro-CT analysis also showed enhanced defect closure and higher bone density in DCC implanted sites while RAMAN spectra demonstrated increased abundance of collagen and bone minerals, especially, PO43- ions than DMB. In conclusion, both DMB and DCC granules demonstrated favorable osteogenic potential in critical-sized defects, with DCC exhibited superior osteoconductive, osteoinductive and osteogenesis properties.

Expression and Regulatory Network Analysis of BICC1 for Aged Sca-1-Positive Bone Narrow Mesenchymal Stem Cells

Background

The impaired osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs) is a major cause of bone remodeling imbalance and osteoporosis. The bicaudal C homologue 1 (BICC1) gene is a genetic regulator of bone mineral density (BMD) and promotes osteoblast differentiation. The purpose of this study is to explore the probable function of BICC1 in osteoporosis and osteogenic differentiation of aged BMSCs.

Methods

We examined the GSE116925 microarray dataset obtained from the Gene Expression Omnibus (GEO) database. The GEO2R algorithm identified differentially expressed genes (DEGs) in Sca-1+ BMSCs from young (3 months old) and old (18 months old) mice. Then, to identify the most crucial genes, we used pathway enrichment analysis and a protein-protein interaction (PPI) network. Furthermore, starBase v2.0 was used to generate the regulatory networks between BICC1 and related competing endogenous RNAs (ceRNAs). NetworkAnalyst was used to construct TF-gene networks and TF-miRNA-gene networks of BICC1 and ceRNA. Furthermore, we investigated the Bicc1 expression in aged Sca-1-positive BMSCs.

Result

We detected 923 DEGs and discovered that epidermal growth factor receptor (EGFR) was the top hub gene with a high degree of linkage. According to the findings of the PPI module analysis, EGFR was mostly engaged in cytokine signaling in immune system and inflammation-related signaling pathways. 282 ceRNAs were found to interact with the BICC1 gene. EGFR was not only identified as a hub gene but also as a BICC1-related ceRNA. Then, we predicted 11 common TF-genes and 7 miRNAs between BICC1 and EGFR. Finally, we found that BICC1 mRNA and EGFR mRNA were significantly overexpressed in aged Sca-1-positive BMSCs.

Conclusion

As a genetic gene that affects bone mineral density, BICC1 may be a new target for clinical treatment of senile osteoporosis by influencing osteogenic differentiation of BMSCs through EGFR-related signaling. However, the application of the results requires support from more experimental data.

Biomechanical and biological responses of periodontium in orthodontic tooth movement: up-date in a new decade

Nowadays, orthodontic treatment has become increasingly popular. However, the biological mechanisms of orthodontic tooth movement (OTM) have not been fully elucidated. We were aiming to summarize the evidences regarding the mechanisms of OTM. Firstly, we introduced the research models as a basis for further discussion of mechanisms. Secondly, we proposed a new hypothesis regarding the primary roles of periodontal ligament cells (PDLCs) and osteocytes involved in OTM mechanisms and summarized the biomechanical and biological responses of the periodontium in OTM through four steps, basically in OTM temporal sequences, as follows: (1) Extracellular mechanobiology of periodontium: biological, mechanical, and material changes of acellular components in periodontium under orthodontic forces were introduced. (2) Cell strain: the sensing, transduction, and regulation of mechanical stimuli in PDLCs and osteocytes. (3) Cell activation and differentiation: the activation and differentiation mechanisms of osteoblast and osteoclast, the force-induced sterile inflammation, and the communication networks consisting of sensors and effectors. (4) Tissue remodeling: the remodeling of bone and periodontal ligament (PDL) in the compression side and tension side responding to mechanical stimuli and root resorption. Lastly, we talked about the clinical implications of the updated OTM mechanisms, regarding optimal orthodontic force (OOF), acceleration of OTM, and prevention of root resorption.

RhPDGF – Basic Characteristics and Potential Application in the Oral Surgery – An Overview

Growth factors (GFs) are bioactive molecules participating in organ development, tissue regeneration and repair. They are protein molecules with a relatively low molecular weight and are released by activated platelets. Platelet-derived growth factor (PDGF) is one of the GFs of highest amount in human platelets. It is known to stimulate cell proliferation and extracellular matrix synthesis, as well as angiogenesis in healthy tissues and neoplasms. However, most of the studies in the literature demonstrate the influence of PDGF on tissue regeneration without revealing its intimate mechanisms of action on different cell types. In the current review we emphasis on the effects of PDGF in order to stimulate various biological processes in wide number of pre-clinical and clinical studies.

Comparative Evaluation of the Efficacy of Platelet-rich Fibrin and Calcium Phosphosilicate Putty alone and in Combination in the Treatment of Intrabony Defects: A Randomized Clinical and Radiographic Study

Background:

Combination of platelet-rich fibrin (PRF) and bone substitutes for the treatment of intrabony pockets is based on sound biologic rationale. The present study aimed to explore the clinical and radiographic effectiveness of autologous PRF and calcium phosphosilicate (CPS) putty alone and in combination in treatment of intrabony defects.

Materials and Methods:

A total of 45 intrabony defects were selected and randomly divided into three groups. In Group I, mucoperiosteal flap elevation followed by placement of PRF was done. In Group II, mucoperiosteal flap elevation followed by placement of CPS putty was done. In Group III, mucoperiosteal flap elevation followed by placement of PRF and CPS putty was done. Clinical parameters such as gingival index (GI), pocket depth (PD), clinical attachment level (CAL), gingival marginal position and radiographic parameters such as bone fill, changes in crestal bone level, and defect depth resolution were recorded at baseline and after 6 months postoperatively.

Results:

Statistically significant changes in GI, PD reduction, CAL gain, defect fill, and defect depth resolution from baseline to 6 months were seen in all the three groups (P < 0.05). On intergroup comparison, no statistically significant changes were seen in all clinical parameters. However, the difference in defect fill and defect depth resolution between the Groups I and III and Group II and III was significant.

Conclusion:

Within limitations of study, combination of PRF and CPS putty showed a significant improvement in PD reduction, CAL gain, and bone fill.

Osteostimulatory effect of bone grafts on fibroblast cultures

Objective:

We analyzed the morphological changes and alkaline phosphatase (ALP) level in fibroblast, which is indicative of their functional ability when cultured in three different commercially available graft materials with osseoconductive property.

Materials and Methods:

Fibroblasts obtained from fifth passage were seeded within three different bone substitutes (bovine hydroxyapatite [HA] [Osseo-graft^®], β-tricalciumphosphate [RTR^®], bovine HA [Bio-oss^®]) and incubated under standard cell culture conditions. 10 samples in each group were evaluated for cell morphology and alkaline phosphates activity using scanning electron microscopy and spectrophotometric analysis on the 7^th day of culture.

Results:

Fibroblast cultured with RTR^® showed changes in morphology and increase in ALP activity when compared to fibroblast cultured with Osseo-graft^® and Bio-oss^®.

Conclusion:

Alkaline phosphatase activity was observed in fibroblasts when cultured with three types of commercially available bone grafts. ALP activity was highest when cultured with β-tricalcium phosphate graft material indicating its better bone regenerating capacity of this graft material.

Enamel matrix proteins exhibit growth factor activity: A review of evidence at the cellular and molecular levels

Enamel matrix derivative (EMD) is a commercially available protein extract, mainly comprising amelogenins. A number of other polypeptides have been identified in EMD, mostly growth factors, which promote cementogenesis and osteogenesis during the regeneration processes through the regulation of cell proliferation, differentiation and activity; however, not all of their functions are clear. Enamel extracts have been proposed to have numerous activities such as bone morphogenetic protein- and transforming growth factor β (TGF-β)-like activity, and activities similar to those of insulin-like growth factor, fibroblast growth factor, platelet-derived growth factor, vascular endothelial growth factor and epidermal growth factor. These activities have been observed at the molecular and cellular levels and in numerous animal models. Furthermore, it has been suggested that EMD contains an unidentified biologically active factor that acts in combination with TGF-β1, and several studies have reported functional similarities between growth factors and TGF-β in cellular processes. The effects of enamel extracts on the cell cycle and biology are summarized and discussed in this review.

Tissue engineering for bone regeneration and osseointegration in the oral cavity

OBJECTIVE

The focus of this review is to summarize recent advances on regenerative technologies (scaffolding matrices, cell/gene therapy and biologic drug delivery) to promote reconstruction of tooth and dental implant-associated bone defects.

METHODS

An overview of scaffolds developed for application in bone regeneration is presented with an emphasis on identifying the primary criteria required for optimized scaffold design for the purpose of regenerating physiologically functional osseous tissues. Growth factors and other biologics with clinical potential for osteogenesis are examined, with a comprehensive assessment of pre-clinical and clinical studies. Potential novel improvements to current matrix-based delivery platforms for increased control of growth factor spatiotemporal release kinetics are highlighting including recent advancements in stem cell and gene therapy.

RESULTS

An analysis of existing scaffold materials, their strategic design for tissue regeneration, and use of growth factors for improved bone formation in oral regenerative therapies results in the identification of current limitations and required improvements to continue moving the field of bone tissue engineering forward into the clinical arena.

SIGNIFICANCE

Development of optimized scaffolding matrices for the predictable regeneration of structurally and physiologically functional osseous tissues is still an elusive goal. The introduction of growth factor biologics and cells has the potential to improve the biomimetic properties and regenerative potential of scaffold-based delivery platforms for next-generation patient-specific treatments with greater clinical outcome predictability.

Periodontal regeneration using platelet-derived growth factor in infrabony defects: a series of three cases

The periodontal researchers and clinicians, in an effort to develop effective regenerative therapies, have sought to understand key events involved in the regeneration of periodontium. Polypeptide growth factors are a class of natural biological mediators which regulate key cellular events in tissue repair. Platelet-derived growth factor (PDGF) is the most thoroughly studied growth factor in periodontal regeneration. The present case series evaluate the effectiveness of platelet-derived growth factor (rh-PDGF-BB) in combination with beta-tricalcium phosphate ( β -TCP) to achieve periodontal regeneration in 3 infrabony defects.

Alveolar bone graft with Platelet Rich Plasma in cleft alveolus

INTRODUCTION

Cleft of the lip, palate and alveolus are the commonest congenital anomaly to affect the orofacial region. Currently, there is great interest in the alveolar bone grafting procedures that involve use of platelet-rich-plasma (PRP), to enhance bone formation and specifically to promote bone graft healing.

MATERIALS AND METHODS

20 patients with residual alveolar cleft, in the age group of 9-29 years, having unilateral or bilateral cleft lip and palate were selected. They were randomly assigned in either group A (with PRP) or group B (without PRP).

RESULTS

Primary healing was observed in 90% patients in group A. Secondary healing was seen in 30% patients in group B. There was no graft rejection in group A but was seen in one patient (10%) in group B. Pain and swelling persisted longer in group B then group A. Bone grafts with added PRP presented with increased bone density (1028.00 ± 11.30 HU) in comparison to grafts without PRP (859.50 ± 27.73 HU) at end of 6-month postoperative. However, the mean bone density (as determined by the Dentascan image analyzer software) was 1.04 times more in the PRP group than non PRP group at 3-month and 1.2 times more at 6 months.

CONCLUSION

We conclude that on preliminary investigations, PRP seems to enhance bone formation in alveolar clefts when admixed with autologous cancellous bone harvested from the iliac crest.

Coronally advanced flap and combination therapy for root coverage. Clinical strategies based on scientific evidence and clinical experience

During the past three decades, several surgical techniques have been proposed to treat single and multiple gingival recessions. Evidence indicates that coronally advanced flap-based approaches result in the best clinical results. Among all the different techniques, the use of a graft under a coronally advanced flap results in the best short- and long-term outcomes in terms of root coverage and gain in keratinized tissue. The use of a coronally advanced flap + connective tissue graft would appear to be the best choice for root coverage. However, harvesting a graft from the palate adds morbidity, surgical chair-time and requires increased surgical skills. A potential alternative could be the use of enamel matrix derivatives under a coronally advanced flap, and this achieves similar clinical outcomes and is less invasive, but adds economic costs to the treatment. Evidence shows that a coronally advanced flap alone in many instances results in complete root coverage and is stable over time. A coronally advanced flap is less invasive for the patient, requires less chair-time and probably less surgical skill. It would therefore be desirable to use a coronally advanced flap approach when indicated. It has been hypothesized that a coronally advanced flap approach alone could be successfully applied when the residual gingiva is thick and wide, although existing evidence does not support this hypothesis in full. Accordingly, the adjunctive use of a graft or enamel matrix derivatives could be restricted to sites at which there is thin and narrow residual gingiva.

Platelet-rich plasma in the treatment of Class II furcation defects: a histometrical study in dogs

Objective

This study was designed to evaluate the potential adjunctive benefits of platelet-rich plasma (PRP) when used with guided-tissue regeneration (GTR) and bioactive glass (BG) in the treatment of Class II furcation lesions.

Material and Methods

Bilateral Class II furcation lesions were surgically created and allowed to become chronic in the mandibular third premolars of 9 dogs. The defects were randomly assigned to: A) GTR+BG and B) GTR+BG+PRP. Similar defects were created in the maxillary third premolars and received the same treatments after 45 days. Dogs were sacrificed 90 days after the first treatment. The histometric parameters evaluated were: connective tissue adaptation, new cementum, new bone, mineralized bone area, non-mineralized bone area, and residual BG particle area.

Results

Data analysis showed a superior length of new cementum and a greater mineralized bone area for group B in both periods (p<0.05). The non-mineralized bone area was greater in the control group (p<0.05) in both periods.

Conclusion

Within the limits of this study, it can be concluded that the use of PRP in the treatment of Class II furcation defects may enhance the amount of new cementum and provide a more mineralized bone in a shorter period of time.

Biomaterial delivery of morphogens to mimic the natural healing cascade in bone

Complications in treatment of large bone defects using bone grafting still remain. Our understanding of the endogenous bone regeneration cascade has inspired the exploration of a wide variety of growth factors (GFs) in an effort to mimic the natural signaling that controls bone healing. Biomaterial-based delivery of single exogenous GFs has shown therapeutic efficacy, and this likely relates to its ability to recruit and promote replication of cells involved in tissue development and the healing process. However, as the natural bone healing cascade involves the action of multiple factors, each acting in a specific spatiotemporal pattern, strategies aiming to mimic the critical aspects of this process will likely benefit from the usage of multiple therapeutic agents. This article reviews the current status of approaches to deliver single GFs, as well as ongoing efforts to develop sophisticated delivery platforms to deliver multiple lineage-directing morphogens (multiple GFs) during bone healing.

Platelet-rich plasma in periodontal defect treatment after extraction of impacted mandibular third molars

PURPOSE

The extraction of mesioangular impacted third molars may cause multiple periodontal defects at the distal root of the second molar. Platelet-rich plasma (PRP) is a material containing many autologous growth factors that may be used in repairing and preventing periodontal complications at the distal root of the second molar adjacent to the extracted third molar.

MATERIALS AND METHODS

We analyzed the effects of autologous PRP on periodontal tissues after extraction of the third molar in 18 young patients (age, 20-30 years). Inclusion criteria were the presence of a pocket distal to the mandibular second molar with a probing depth [3] of 7.5 mm and a probing attachment level [3] of 6 mm.

RESULTS

We observed, at 12 weeks after surgery, a notable reduction in the probing depth and an improvement in the probing attachment level in those cases treated with PRP compared with the controls, as well as formation of new bone tissue in the bone defect.

CONCLUSION

We showed that PRP is effective in inducing and accelerating bone regeneration for the treatment of periodontal defects at the distal root of the mandibular second molar after surgical extraction of a mesioangular, deeply impacted mandibular third molar.

Growth Differentiation Factor 5 (GDF-5) Induces Matrix Metalloproteinase 2 (MMP-2) Expression in Periodontal Ligament Cells and Modulates MMP-2 and MMP-13 Activity in Osteoblasts

Growth differentiation factor 5 (GDF-5), a member of the transforming growth factor beta (TGF-β) superfamily expressed in periodontal tissues, promotes extracellular matrix (ECM) in periodontal ligament (PDL) cells. Matrix metalloproteinases (MMP) are proteolytic enzymes that degrade ECM and are expressed in PDL cells. To date, little is known about the regulation of MMP synthesis and secretion in PDL cells. The aim of this study is to examine the effects of GDF-5 on MMP production and activity in PDL cells. GDF-5 increased both collagen type I alpha 2 (Col Iα2) and MMP-2 gene expression in cells derived from mouse PDL tissues after 3 days of culture. Because PDL cells represent a heterogeneous population, we examined gelatinolytic activity and gene expression profiles in an osteoblast cell line. After 6, 12, 24, and 48 hours of culture, GDF-5 increased both Col Iα2 and MMP gene expression in osteoblasts. GDF-5 also promoted MMP-2 activity as revealed by gelatin zymography after 7 days of culture. In the presence of the p38 MAP kinase inhibitor SB202190, on the other hand, MMP-2 activity was blocked. Taken together, these results indicate that GDF-5 may increase simultaneously the gene expression of type I collagen and MMP-2 in the osteoblast-like cells among the PDL cells and p38 MAP kinase pathway in osteoblast could involve in the regulation of MMP-2 enzyme activity induced by GDF-5.

Effect of platelet-derived growth factor-BB on root resorption after reimplantation of partially denuded tooth in dog

The prognosis for a reimplanted tooth depends largely on the condition of the root. Platelet-derived growth factor (PDGF)-BB has been shown to regenerate periodontal tissue in animal and human clinical studies. However, information regarding the effect of PDGF-BB on tooth reimplantation is limited. The objective of this study was to investigate the effect of PDGF-BB on root resorption after reimplantation of a partially denuded tooth in dog. A total of 15 healthy female beagle dogs were used. Mandibular third and fourth premolars were endodontically treated and then extracted as atraumatically as possible. The coronal portion of each root was carefully scaled and planed. The roots on the right side of the mandible were treated with PDGF-BB and reimplanted, while the roots on the left side served as controls. After 2, 4, or 8 weeks, specimens were collected and processed for histopathological examination. By the 4th week after reimplantation, new periodontal ligament (PDL)-like tissue had formed around the PDGF-BB-treated root surfaces and new bone. By the 8th week, healing of the PDGF-BB-treated roots was characterized by newly formed PDL with inserting attachment formation. In contrast, control roots showed multiple areas of replacement resorption. Immunohistochemical staining of proliferating cell nuclear antigen (PCNA) performed at 2 weeks after reimplantation showed that the number of PCNA-positive cells in the connective tissue area was statistically significantly greater in the PDGF-BB-treated group than in the control group (P < 0.001). The application of PDGF-BB resulted in a significantly lower occurrence and extent of root resorption and ankylosis. These results suggest that the use of PDGF-BB reduces occurrence of ankylosis and root resorption in tooth reimplantation.

Gene expression pattern during osteogenic differentiation of human periodontal ligament cells in vitro

Purpose

Periodontal ligament (PDL) cell differentiation into osteoblasts is important in bone formation. Bone formation is a complex biological process and involves several tightly regulated gene expression patterns of bone-related proteins. The expression patterns of bone related proteins are regulated in a temporal manner both in vivo and in vitro. The aim of this study was to observe the gene expression profile in PDL cell proliferation, differentiation, and mineralization in vitro.

Methods

PDL cells were grown until confluence, which were then designated as day 0, and nodule formation was induced by the addition of 50 µg/mL ascorbic acid, 10 mM β-glycerophosphate, and 100 nM dexamethasone to the medium. The dishes were stained with Alizarin Red S on days 1, 7, 14, and 21. Real-time polymerase chain reaction was performed for the detection of various genes on days 0, 1, 7, 14, and 21.

Results

On day 0 with a confluent monolayer, in the active proliferative stage, c-myc gene expression was observed at its maximal level. On day 7 with a multilayer, alkaline phosphatase, bone morphogenetic protein (BMP)-2, and BMP-4 gene expression had increased and this was followed by maximal expression of osteocalcin on day 14 with the initiation of nodule mineralization. In relationship to apoptosis, c-fos gene expression peaked on day 21 and was characterized by the post-mineralization stage. Here, various genes were regulated in a temporal manner during PDL fibroblast proliferation, extracellular matrix maturation, and mineralization. The gene expression pattern was similar.

Conclusions

We can speculate that the gene expression pattern occurs during PDL cell proliferation, differentiation, and mineralization. On the basis of these results, it might be possible to understand the various factors that influence PDL cell proliferation, extracellular matrix maturation, and mineralization with regard to gene expression patterns.

Comparative radiographic evaluation of alveolar bone healing associated with autologous platelet-rich plasma after impacted mandibular third molar surgery

PURPOSE

This study radiographically evaluated the performance of autologous platelet-rich plasma (PRP) applied in tooth sockets.

PATIENTS AND METHODS

Thirty extractions of bilateral impacted mandibular third molars were performed in 15 volunteers (7 men, 8 women; 18 to 22 years old). After extraction of right and left mandibular third molars, the socket at 1 side received the autologous PRP (PRP group) and the other was filled with blood clot (control group). Millimeter periapical radiographs were obtained 7 days, 1 month, and 2, 3, and 6 months postoperatively. Radiographic bone density was quantified 3 times by the same examiner at different moments using HLImage 97 software, and data were statistically analyzed by Statgraf 7.0 software (analysis of variance and Tukey test).

RESULTS

In general, there was significantly faster bone formation in sockets treated with PRP (P < .01). Significant bone formation was observed in the first month (P < .01), second month (P < .05), and third month (P < .01) for the PRP group. No statistical differences were observed on the seventh day and sixth month of investigation, yet there were higher means of radiographic bone density in sockets treated with PRP. In the control group, men exhibited significant bone repair compared with women (P < .05).

CONCLUSION

Autologous PRP was found to accelerate alveolar bone regeneration, and men presented better repair after tooth extraction.

Effect of β tricalcium phosphate particle size on recombinant human platelet-derived growth factor-BB-induced regeneration of periodontal tissue in dog

The aim of this study was to investigate the effect of β tricalcium phosphate (β-TCP) particle size on recombinant human platelet-derived growth factor-BB (rhPDGF-BB)-induced regeneration of periodontal tissue in dog. The control group (rhPDGF-BB alone) was characterized by incomplete, newly formed bone. The large-particle β-TCP (L-TCP(O))/rhPDGF-BB group showed a statistically significant increase in both new bone and cementum formation compared to the small-particle β-TCP (S-TCP(G))/rhPDGF-BB group. These findings suggest that L-TCP(O)-particle promotes rhPDGF-BB-induced formation of bone and cementum.

Novel regenerative strategies to enhance periodontal therapy outcome

BACKGROUND

Chronic periodontitis is a widely prevalent inflammatory condition of the supporting tissues of the teeth and is characterized by loss of teeth with an associated risk of systemic complications. Regenerative therapies such as guided tissue and bone regeneration form an important armamentarium in periodontics with a high degree of outcome predictability in certain ideal clinical scenarios.

OBJECTIVE/METHODS

This review elaborates novel tissue regenerative treatment modalities based on sound understanding of developmental biology, tissue engineering, inflammation and wound healing. We focus on the role of biological mediators such as growth factors, gene-based therapy, cell therapy and pro-resolution lipid mediators in the regeneration of lost bone or periodontium.

RESULTS/CONCLUSIONS

These therapies have the potential to regenerate both periodontium and bone, aiding in the treatment of even clinically challenging cases.

Guided tissue regeneration-based root coverage with a platelet concentrate graft: a 3-year follow-up case series

BACKGROUND

A platelet concentrate graft (PCG) was applied underneath the barrier membrane in guided tissue regeneration (GTR)-based root coverage procedures. The purpose of this case study was to assess the effectiveness of the technique and the long-term outcomes.

METHODS

Thirty-seven Miller Class I or II recession defects in six patients were treated using the PCG and a collagen membrane covered by an advanced mucogingival flap. Clinical parameters, such as vertical gingival recession depth (VRD), clinical attachment level (CAL), probing depth (PD), and width of keratinized tissue (WKT), were recorded presurgery (at baseline [BL]) and at 6 and 36 months of follow-up. The Wilcoxon signed-rank test and the Mann-Whitney test were used to assess statistical significance (alpha = 0.05).

RESULTS

Between BL and 6 months, there was a statistically significant reduction in VRD (from 2.81 +/- 0.88 mm to 0.30 +/- 0.48 mm) and PD (from 2.59 +/- 0.50 mm to 1.14 +/- 0.35 mm), as well as an improvement in CAL (from 5.41 +/- 0.86 mm to 1.43 +/- 0.66 mm). These results remained stable over the following 30 months. There was no statistically significant change in WKT during the initial 6 months; however, the increase in WKT was statistically significant at the 36-month follow-up. When comparing the healing between the maxillary and mandibular teeth at 6 months, the VRD reduction was statistically significantly greater in the maxillary teeth, but the difference was not statistically significant 30 months later. The average root coverage at 6 and 36 months was 89.86% +/- 15.85% and 85.86% +/- 18.16%, respectively, with complete root coverage in 24 (64.86%) and 21 (56.76%) of the 37 teeth.

CONCLUSIONS

The GTR-based technique using PCG was effective in reducing gingival recession. The outcomes remained stable for 3 years.

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.

Root cementum may modulate gene expression during periodontal regeneration: a preliminary study in humans

BACKGROUND

Previous data demonstrated that root cementum may affect periodontal regeneration. As such, this study aimed to explore further possible mechanisms involved in this process by investigating in humans whether root cementum modulates gene expression in the regenerating tissue formed under membrane-protected intrabony defects.

METHODS

Thirty subjects with deep intrabony defects (> or =5 mm; 2- or 3-wall) were selected and assigned to the control or test group. The control group received scaling and root planing with the removal of granulation tissue and root cementum; the test group underwent removal of granulation tissue and soft microbial deposits by cleaning the root surface with a microbrush and saline solution, aiming at cementum preservation. Guided tissue regeneration (GTR) was applied to both groups. Twenty-one days later, the newly formed tissue under the membrane was assessed for the expression of the following genes: alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN), platelet-derived growth factor-alpha (PDGFA), bone sialoprotein (BSP), and basic fibroblast growth factor (bFGF).

RESULTS

Data analysis demonstrated that mRNA levels for PDGFA, BSP, and bFGF were higher in the sites where root cementum was kept in place compared to the sites where root cementum was removed completely as part of the periodontal therapy (P <0.05); in contrast, OCN levels were lower (P <0.05). No difference for ALP or OPN was observed between the control and test groups (P >0.05).

CONCLUSION

Root cementum may modulate the expression of growth and mineral-associated factors during periodontal regeneration.

In Vitro Effects of Combined and Sequential Bone Morphogenetic Protein Administration

OBJECTIVE

To assess the effects of combined and sequential administration of bone morphogenetic protein 2 (BMP-2) and BMP-7 on osteoblastic differentiation compared with administration of single growth factors.

DESIGN

In vitro study of osseous differentiation in murine pluripotent cells using assays of extracellular matrix calcification, alkaline phosphatase activity, and expression of osseous markers. Mesenchymal cells were cultured with BMP-2, BMP-7, or a combination of these growth factors or were sequentially exposed to the growth factors.

RESULTS

Sequential administration of BMP-2 and BMP-7 resulted in increased extracellular matrix calcification and expression of osteocalcin, whereas all groups treated with BMP up-regulated expression of the osteoblastic transcription factor Runx2/cbfa1, type I collagen, and the inhibitory BMP second messenger Smad6. None of the experimental groups demonstrated increased expression of osteopontin or Smad1, and only cells treated with concurrent administration of BMP-2 and BMP-7 increased Smad5 expression. Alkaline phosphatase activity was increased from baseline only in cells treated with BMP-2 alone.

CONCLUSIONS

Culture with BMP-2 and BMP-7, their sequential administration, and their coadministration had variable effects on osseous differentiation in mesenchymal cells. These results demonstrate the need for increased understanding of the role of growth factors and their combinations in bone development and have important implications for the ongoing development of osteoinductive therapies.

Effects of Platelet Concentrate on Palatal Wound Healing After Connective Tissue Graft Harvesting

BACKGROUND

Platelet concentrate (PC) is known to contain growth factors that stimulate cellular proliferation and differentiation. In this double-blind, placebo-controlled, randomized study, the objective was to determine whether PC accelerated connective tissue graft (CTG) wound healing and maintained donor site tissue thickness.

METHODS

Twenty healthy adult subjects with multiple bilateral gingival recessions were treated with CTGs and PC combined with CTGs. The donor sites were treated with PC and placebo. Clinical wound healing was observed for an average of 6 weeks. Biopsies were taken from donor sites and submitted for histology and immunohistochemical analysis for type I and III collagens. Palatal tissue thickness, post-surgical complications, and pain level were evaluated. Wilcoxon, Cronbach, one-sample t, and paired-sample t tests were used to assess statistical significance at P <0.05.

RESULTS

PC-treated palatal donor sites were 1.10 mm thicker than control sites. PC-treated recipient sites showed accelerated clinical healing compared to controls. PC did not accelerate donor site clinical healing. No significant statistical differences in complication occurrence and perceived pain levels were found between control and PC-treated sites. Biopsy samples revealed that during healing, PC-treated sites contained lower concentrations of inflammatory cells, more type I mature collagen, and less type III immature collagen than control sites.

CONCLUSIONS

PC may accelerate wound healing and hasten the regeneration of palatal donor tissue. PC did not influence complication occurrences or mediate pain level. PC has the potential to shorten the treatment time for patients who need multiple CTG procedures.

A simple cell motility assay demonstrates differential motility of human periodontal ligament fibroblasts, gingival fibroblasts, and pre-osteoblasts

During periodontal regeneration, multiple cell types can invade the wound site, thereby leading to repair. Cell motility requires interactions mediated by integrin receptors for the extracellular matrix (ECM), which might be useful in guiding specific cell populations into the periodontal defect. Our data demonstrate that fibroblasts exhibit differential motility when grown on ECM proteins. Specifically, gingival fibroblasts are twice as motile as periodontal ligament fibroblasts, whereas osteoblasts are essentially non-motile. Collagens promote the greatest motility of gingival fibroblasts in the following order: collagen III>collagen V>collagen I. Differences in motility do not correlate with cell proliferation or integrin expression. Osteoblasts display greater attachment to collagens than does either fibroblast population, but lower motility. Gingival fibroblast motility on collagen I is generally mediated by alpha2 integrins, whereas motility on collagen III involves alpha1 integrins. Other integrins (alpha10 or alpha11) may also contribute to gingival fibroblast motility. Thus, ECM proteins do indeed differentially promote the cell motility of periodontal cells. Because of their greater motility, gingival fibroblasts have more of a potential to invade periodontal wound sites and to contribute to regeneration. This finding may explain the formation of disorganized connective tissue masses rather than the occurrence of the true regeneration of the periodontium.

Influence of autologous platelet concentrate on healing in intra-bony defects following guided tissue regeneration therapy: a randomized prospective clinical split-mouth study

OBJECTIVES

To investigate the influence of autologous platelet concentrate (APC) on early wound healing and regeneration outcomes following guided tissue regeneration (GTR) therapy.

MATERIAL AND METHODS

In 25 patients, two contralateral deep intra-bony defects were treated with beta-TCP and a bioresorbable GTR membrane. They were randomly assigned to test and control procedure. In test defects, APC was additionally applied. After 3, 6, and 12 months, healing results were assessed by clinical parameters and quantitative digital subtraction radiography.

RESULTS

Post-operative membrane exposures occurred in 48% of the test sites and 80% of the control sites. Both groups revealed a significant clinical attachment level (CAL) gain of 5 mm after 12 months. Eighty-eight per cent of test and control sites showed a CAL gain of > or =4 mm. No clinical parameter revealed significant differences between test and control sites. A significant bone density gain was found in both groups after 3, 6, and 12 months. Only after 6 months, the bone density gain was significantly greater in the test defects.

CONCLUSION

Within the limits of this study, autologous platelet concentrate did not seem to have a noticeable influence on the clinical and most of the radiographic outcomes following GTR. However, APC might reduce the occurrence of post-operative membrane exposures and accelerate bone density gain.

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.

Platelet-rich plasma/osteoblasts complex induces bone formation via osteoblastic differentiation following subcutaneous transplantation

BACKGROUND AND OBJECTIVE

Platelet-rich plasma (PRP) has been shown to enhance the maturation of bone grafts following local application and to have biological effects on osteoblasts in vitro. However, PRP is not applied by itself clinically as a result of its poor benefits in large bone defects. The present study was undertaken to develop a clinical alternative to autologous bone, by investigating the application of PRP in combination with osteoblastic cells and evaluating its effects after transplantation.

MATERIAL AND METHODS

PRP and platelet-poor plasma (PPP) were prepared from blood, obtained from ddY mice, by two centrifugation steps. MC3T3-E1 cells were labeled with fluorescent carbocyanine just before transplantation. The combination of labeled cells and PRP gel was subcutaneously transplanted into the back of severe combined immunodeficient (SCID) mice, and the transplants were evaluated radiographically and immunohistologically after 4 wk. The effects of PRP were assessed by alkaline phosphatase (ALP) staining and von Kossa staining, and the expression of bone-related markers was analyzed by reverse transcription-polymerase chain reaction before transplantation.

RESULTS

Before transplantation, PRP enhanced the expression of Osterix and bone sialoprotein mRNAs compared with PPP. Furthermore, PRP elevated ALP activity and induced the formation of mineralized nodules. After transplantation, the combination of labeled cells and PRP gel formed mineralized tissue, and the transplanted cells visualized in the tissue using fluorescence microscopy expressed osteocalcin and type I collagen.

CONCLUSION

These results suggest that the application of a PRP/osteoblasts complex has beneficial effects for transplanting engineered cells into bone defects through the promotion of osteoblastic differentiation.

Early injection of OP-1 during distraction osteogenesis accelerates new bone formation in rabbits

Distraction osteogenesis (DO) is a surgical technique for generating new bone by applying controlled distraction of two bony segments post osteotomy. A limitation of the technique is the long time required for the new bone to consolidate. We investigated the effect of injecting osteogenic protein 1 (OP-1) at the beginning of distraction in a rabbit model of DO. Regenerate bone was evaluated using radiology, densitometry, micro-computed tomography (microCT) and histomorphometry. Immunohistochemsitry was used to evaluate changes in expression of various ligands, growth factors and receptors following OP-1 treatment. Compared to the control, a two-fold increase in bone volume was apparent for treated groups at 3 weeks post injection. An upregulation of almost all of the 41 genes examined was observed. Results suggested that applying OP-1 early during distraction can accelerate bone formation by the activation of numerous pathways. This study provides further insights on strategies to improve bone regeneration rate in DO.

Growth factor delivery for oral and periodontal tissue engineering

The treatment of oral and periodontal diseases and associated anomalies accounts for a significant proportion of the healthcare burden, with the manifestations of these conditions being functionally and psychologically debilitating. Growth factors are critical to the development, maturation, maintenance and repair of craniofacial tissues, as they establish an extracellular environment that is conducive to cell and tissue growth. Tissue-engineering principles aim to exploit these properties in the development of biomimetic materials that can provide an appropriate microenvironment for tissue development. These materials have been constructed into devices that can be used as vehicles for delivery of cells, growth factors and DNA. In this review, different mechanisms of drug delivery are addressed in the context of novel approaches to reconstruct and engineer oral- and tooth-supporting structures, namely the periodontium and alveolar bone.

Sprouty genes are expressed in osteoblasts and inhibit fibroblast growth factor-mediated osteoblast responses

Fibroblast growth factors (FGFs) and fibroblast growth factor receptors (FGFRs) are major regulators of skeletal growth and development. Signal transduction via FGFRs is complex and mediates proliferation, differentiation, or migration depending upon the cellular context. Members of the Spry gene family antagonize the FGFR signal transduction pathway and inhibit lung morphogenesis, angiogenesis, and chondrogenesis. We examined the expression of Spry2 in the osteoblastic MC3T3-E1 cell line. MC3T3-E1 cells express Spry2 in response to FGF1 stimulation. Treatment of MC3T3-E1 cells with FGF1 results in the expression of Spry2 in a manner consistent with an early response gene. Pharmacological inhibitors of mitogen-activated protein kinase activation inhibit FGF1-induced expression of Spry2 mRNA. Transient overexpression of Spry2 in MC3T3-E1 resulted in decreased FGF1-mediated extracellular signal-regulated kinase phosphorylation and FGF1-stimulated osteopontin promoter activity. Furthermore, we show that Spry2 interacts with Raf-1 in a glutathione-S-transferase pulldown assay and that this interaction may involve multiple sites. Finally, Spry2 expression precedes the onset of the expression of osteoblast differentiation markers in an in vitro assay of primary osteoblast differentiation. Taken together, these results indicate that Spry2 expression is an early response to stimulation by FGF1 in MC3T3-E1 cells and acts as a feedback inhibitor of FGF1-induced osteoblast responses, possibly through interaction with Raf1.

The contribution of platelet-derived growth factor, transforming growth factor-beta1, and insulin-like growth factor-I in platelet-rich plasma to the proliferation of osteoblast-like cells

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation of osteoblast-like cells in vitro. PRP was prepared using a centrifuge; the number of platelets (n = 32) and the levels of platelet-derived growth factor-AB (PDGF-AB), transforming growth factor-beta1 (TGF-beta1), and insulin-like growth factor-I (IGF-I) were measured (n = 16). For the proliferation assay, SaOS-2 was cultured in the presence of platelet-poor plasma (PPP), whole blood, or PRP. The cell number was counted after 36 and 72 hours. To investigate the effect of each growth factor, the cells were cultured with PRP in the absence or presence of neutralizing antibodies, and counted as described. The mean platelet count of PRP was 1546.36 +/- 382.25 x 10(3)/microL, and the mean levels of PDGF-AB, TGF-beta1 and IGF-I were 0.271 +/- 0.043, 0.190 +/- 0.039, and 0.110 +/- 0.039 ng/1500 x 10(3) platelets, respectively. Cell proliferation was enhanced in all PRP groups in a dose-dependent manner, and all neutralizing antibodies significantly suppressed proliferation compared with the PRP group, lacking antibody, at 36 hours. However, at 72 hours, the neutralizing antibodies of PDGF and TGF-beta1, but not IGF-I, significantly suppressed proliferation. These results show the beneficial abilities of PRP in the proliferation of osteoblast-like cells from the standpoint of growth factors, including the contribution of each factor.

Use of autologous platelet-rich plasma (PRP) in periodontal defect treatment after extraction of impacted mandibular third molars

PURPOSE

The extraction of mesioangular impacted third molars may cause multiple periodontal defects at the distal root of the second molar. Platelet-rich plasma (PRP) is a material containing many autologous growth factors that may be used in repairing and preventing periodontal complications at the distal root of the second molar adjacent to the extracted third molar.

PATIENTS AND METHODS

We analyzed the effects of autologous PRP on periodontal tissues after extraction of the third molar in 18 young patients (age, 21-26 years). Inclusion criteria were the presence of a pocket distal to the mandibular second molar with a probing depth>or=7.5 mm and a probing attachment level>or=6 mm.

RESULTS

We observed, at 12 weeks after surgery, a notable reduction in the probing depth and an improvement in the probing attachment level in those cases treated with PRP compared with the controls, as well as formation of new bone tissue in the bone defect.

CONCLUSION

We showed that PRP is effective in inducing and accelerating bone regeneration for the treatment of periodontal defects at the distal root of the mandibular second molar after surgical extraction of a mesioangular, deeply impacted mandibular third molar.

Molecular characterization of spontaneous and growth-factor-augmented chondrogenesis in periosteum–bone tissue transferred into a joint

Multilineage potential of progenitor cells from periosteum is well established, but conditions for differentiation within their native niche are unclear. We evaluated at cellular and molecular levels whether chondrogenesis of periosteal progenitor cells is promoted spontaneously or by growth-factor mixture (GFM) application when transferring periosteum-bone cylinders into cartilage defects. Osteochondral defects in the patellar groove of minipigs were filled with periosteum-bone cylinders and randomly supplemented with GFM. Neochondrogenesis was characterized by histology, immunohistology, and quantitative gene expression analysis. According to morphology and glycosaminoglycan accumulation, spontaneous neocartilage formation occurred in the cambium layer already at 6 weeks, increased after 12 weeks, but declined until 52 weeks, independent of GFM. Multiple cartilage differentiation markers were induced after transfer. Expression of aggrecan, COMP, decorin, and Col10a1 increased significantly within 52 weeks. Sox 9 and Col2a1 mRNA levels were elevated at 6 versus 52 weeks in the GFM group and resulted in higher collagen type II protein accumulation. Neochondrogenesis was promoted in lower periosteum layers by transfer of periosteum-bone plugs into a joint, and collagen type II protein deposition was enhanced by GFM. The final tissue subsumed typical features of periosteum and fibrocartilage but lacked an intact tide mark and features of hyaline cartilage desired for cartilage repair.

Effects of calcium and thrombin on growth factor release from platelet concentrates: kinetics and regulation of endothelial cell proliferation

Platelet concentrates (PCs) constitute new biological mediators used in osseous reconstructive surgery. In this study, we assessed (i) the effects of various concentrations of calcium and thrombin on the kinetics of platelet-derived growth factor (PDGF-BB), transforming growth factor-beta1(TGF-beta 1), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) release by PCs and (ii) the contribution of PC supernatants to endothelial cell proliferation. Our results indicate that high concentrations of calcium (Ca) and thrombin (Thr) trigger an immediate and significant increase in bFGF, TGF-beta 1 and PDGF-BB concentrations. Thereafter, PDGF-BB, VEGF and TGF-beta 1 levels remained generally constant over a 6-day period while a decrease in bFGF concentrations was noted after 24h. Lower Ca and Thr concentrations tended to reduce and delay growth factors release from PCs. Endothelial cell proliferation was greatly enhanced with PC supernatants (mean: 20-fold increase). This was especially evident when endothelial cells were treated with supernatants harvested early after PC treatment with high concentrations of Ca and Thr or later after PC treatment with low Ca and Thr concentrations. Additional research aiming to measure the effects of Ca and Thr on bone formation in vivo is needed.

A Comparative Study of Root Coverage With Connective Tissue and Platelet Concentrate Grafts: 8-Month Results

BACKGROUND

Gingival recession presents destruction of both soft and hard tissues. The objectives of this randomized clinical trial were to assess the clinical efficacy of platelet concentrate grafts (PCG) in the treatment of Miller Class I or II buccal gingival defects and to compare their soft tissue healing with those of subepithelial connective tissue grafts (SCTG).

METHODS

Seventeen arches in 15 patients with bilateral gingival recessions were treated with SCTG and PCG covered by coronally advanced flaps. Vertical recession depth (VRD), clinical attachment level (CAL), clinical probing depth (PD), and width of keratinized tissue (KTW) were measured preoperatively and 8 months postsurgery. Surveys on post-surgical discomfort level (PSDL) and manual platelet count were also performed. Esthetic outcomes were also evaluated. Paired t test, repeated measures analysis of variance (ANOVA), and chi-square and signed-rank tests were used to access statistical significance (alpha = 0.05).

RESULTS

Mean VRD statistically significantly decreased from 2.43 mm presurgery to 0.48 mm with PCG (80% root coverage) and from 2.48 mm to 0.17 mm with SCTG (95% root coverage). No statistically significant differences between the treatments were found for VRD, CAL, and KTW, while mean PD was significantly shallower in the PCG group (1.05 mm) than that in the SCTG group (1.79 mm). Complete coverage was achieved in 60% of the PCG group and in 65.5% of the SCTG group. PSDL was significantly lower in the PCG group 1 month post-surgery. Platelet counts demonstrated a five-fold increase in PC. Soft tissue in the PCG group demonstrated superior contour and texture matching when compared to the SCTG group.

CONCLUSIONS

The platelet concentrate graft may be an alternative graft material for treating gingival recession. Treatment with this graft may result in better esthetic appearance.

Insulin-like Growth Factor-1 Regulates Endogenous RUNX2 Activity in Endothelial Cells through a Phosphatidylinositol 3-Kinase/ERK-dependent and Akt-independent Signaling Pathway

Insulin-like growth factor-1 (IGF-1) is an angiogenic and oncogenic factor that activates signal transduction pathways involved in the expression of transcriptional regulators of tumorigenesis. RUNX2, a member of the Ig-loop family of transcription factors is expressed in vascular endothelial cells (EC) and regulates EC migration, invasion, and proliferation. Here we show that IGF-1 and its receptor regulate post-translational changes in RUNX2 to activate DNA binding in proliferating EC. The phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, reduced both basal and IGF-1-stimulated RUNX2 DNA binding activity in the absence of changes in RUNX2 protein as did the overexpression of the phosphatidylinositol 3-phosphate phosphatase, confirming that PI3K signaling mediates RUNX2 activation. IGF-1 increased ERK1/2 activation, which was abrogated by the inhibition of PI3K, thus linking these two pathways in EC. Treatment with U0126, which inhibits ERK1/2 activation, reduced IGF-1-stimulated RUNX2 DNA binding without affecting RUNX2 protein levels. Overexpression of constitutively active MKK1 increased RUNX2 DNA binding and phosphorylation. No additive effects of PI3K or ERK inhibitors on DNA binding were evident. Surprisingly, these IGF-1-mediated effects on RUNX2 were not regulated by Akt phosphorylation, a common downstream target of PI3K, as determined by pharmacological or genetic inhibition. However, an inhibitor of the p21-activated protein kinase-1, glutathione S-transferase-Pak1-(83-149), inhibited both basal and IGF-1-stimulated RUNX2 DNA binding, suggesting that Pak1 mediates IGF-1 signaling to increase RUNX2 activity. These results indicate that the angiogenic growth factor, IGF-1, can regulate RUNX2 DNA binding through sequential activation of the PI3K/Pak1 and ERK1/2 signaling cascade.

Growth and Amelogenin-Like Factors in Periodontal Wound Healing. A Systematic Review

BACKGROUND

Regeneration of tooth-supporting structures destroyed by periodontitis is a major goal of periodontal therapy. Periodontal tissue engineering utilizing growth and amelogenin-like factors (GAFs) applies advances in materials science and biology to regenerate alveolar bone, periodontal ligament, and cementum. Amelogenin-like factors (e.g., enamel matrix derivative [EMD]) and growth factors (e.g., platelet-derived growth factor [PDGF] and bone morphogenetic proteins [BMPs, also considered morphogens]) have demonstrated pleotrophic effects on the stimulation of several key events required for tissue regeneration including DNA synthesis, chemotaxis, differentiation, and matrix synthesis.

RATIONALE

GAFs have been used for the treatment of periodontal disease as shown in preclinical and clinical studies. This systematic review evaluates the evidence to support the utilization of EMD and growth factors (GFs) for periodontal repair and regeneration associated with natural teeth.

FOCUSED QUESTION

In patients with periodontal osseous defects, what is the effect of GAFs compared with controls on clinical, radiographic, histologic, adverse, and patient-centered outcomes?

SEARCH PROTOCOL

Two investigators searched MEDLINE, pre-MEDLINE, and the Cochrane Oral Health Group trials register for clinical and preclinical studies published in English. Hand searches were performed on the International Journal of Periodontics and Restorative Dentistry, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Periodontology, and Journal of Periodontal Research. Searches were performed for articles published through April 2002. In addition, investigators contacted manufacturers of GAF products for related unpublished data and studies in progress.

SELECTION CRITERIA

INCLUSION CRITERIA

Randomized controlled clinical trials (RCTs), cohort studies, case-control studies, case reports, and preclinical (animal) randomized controlled investigations that included a cohort population diagnosed with periodontal disease and presenting data on intrabony/interproximal defects and/or furcation defects were screened.

EXCLUSION CRITERIA

In vitro studies or those that did not include quantifiable data with respect to clinical or bone measures were not included.

DATA COLLECTION AND ANALYSIS

Meta-analyses were performed for studies that fulfilled the eligibility criteria for the following continuous variables: clinical attachment level (CAL), probing depth (PD), or bone level (radiographic, re-entry, or histologic). Heterogeneity was assessed to determine whether the differences among therapies were due to systematic confounding factors (as noted in study quality assessments).

MAIN RESULTS

1. Eight studies, representing 7 RCTs and 1 quasi-experimental study, representing a total population of 511 subjects were analyzed with respect to EMD. 2. The majority of the remaining papers had a low evidence rating. 3. Most reports were case studies or case series without controls. 4. There were insufficient data to conduct a meta-analysis on the effect of growth factors used in periodontal repair around teeth.

REVIEWERS' CONCLUSIONS

1. There is evidence supporting the use of EMD for periodontal osseous defects to improve CAL and reduce PD, although long-term benefits have not been established. 2. EMD has demonstrated notable consistency among the studies investigated in terms of superiority to controls (in general compared to open flap debridement [OFD]). 3. EMD appears to be safe for single and multiple administrations in terms of lack of elicitation of antibody responses or other local/systemic inflammatory events. 4. Preclinical and initial clinical data for growth factors appear promising but are insufficient to draw definitive conclusions at this time.

Platelet Concentrates: Effects of Calcium and Thrombin on Endothelial Cell Proliferation and Growth Factor Release

BACKGROUND

Clinical evidence suggests that platelet concentrate (PC) could have beneficial therapeutic effects on hard and soft tissue healing, due to the contents of growth factors (GFs) stored in the platelets. The objectives of this study were: 1) to determine the concentrations of platelet-derived growth factor-BB (PDGF-BB), transforming growth factor-beta1 (TGF-beta1), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) released from PCs and whole blood (WB), before and after the addition of various concentrations of calcium and thrombin, and 2) to assess the physiological importance of the released GFs on angiogenesis.

METHODS

WB and PCs were harvested and prepared from three healthy volunteers. Enzyme-linked immunosorbent assay tests, specific for PDGF-BB, TGF-beta1, VEGF, and bFGF, were performed on WB and PC supernatants, collected before and 30 minutes after the addition of various concentrations of calcium and thrombin. The supernatants were also added to human umbilical vein endothelial cell (HUVEC) cultures in order to measure their effects on endothelial cell proliferation.

RESULTS

Growth factor concentrations detected in PC supernatants were significantly greater (280% to 800% increase) than concentrations present in WB supernatants. Calcium and thrombin induced immediate GF release from PCs in a dose-dependent fashion. Furthermore, PC supernatants led to greater HUVEC proliferation rates than WB supernatants. However, there was no correlation between the concentrations of specific GFs and HUVEC proliferation rates.

CONCLUSION

These results suggest that PCs could stimulate blood vessel formation. They also reinforce the relevance for using PCs in regenerative therapies.

Effectiveness of a combination of platelet-rich plasma, bovine porous bone mineral and guided tissue regeneration in the treatment of mandibular grade II molar furcations in humans

OBJECTIVE

A combination of platelet-rich plasma (PRP), bovine porous bone mineral (BPBM) and guided tissue regeneration (GTR) has been shown to be effective as regenerative treatment for intrabony periodontal defects. The purpose of this study was to evaluate the effectiveness of PRP, BPBM and GTR used in combination as regenerative treatment for grade II molar furcation defects in humans.

MATERIAL AND METHODS

Using a split-mouth design, a total of 52 grade II mandibular molar furcation defects were treated either with PRP/BPBM/GTR (experimental group, n=26) or with an open flap debridement (control group, n=26). The primary outcomes evaluated in this study included changes in pocket depth, attachment level and re-entry bone levels (horizontal and vertical) between baseline and 6 months postoperatively.

RESULTS

The results showed that the experimental group presented with significantly greater pocket reduction (4.07+/-0.33 mm for experimental and 2.49+/-0.38 mm for control sites), gain in clinical attachment (3.29 +/- 0.42 mm for experimental and 1.68+/-0.31 mm for control sites), vertical defect fill (2.56+/- 0.36 mm for experimental and -0.19+/-0.02 for control sites) and horizontal defect fill (2.28+/-0.33 mm for experimental and 0.08+/-0.02 mm for control sites) than the control group.

CONCLUSIONS

It was concluded that the PRP/BPBM/GTR combined technique is an effective modality of regenerative treatment for mandibular grade II furcation defects. Further studies are necessary to elucidate the role played by each component of the combined therapy in achieving these results.

In vitro evaluation of the mitogenic effect of platelet-derived growth factor-BB on human periodontal ligament cells cultured with various bone allografts

BACKGROUND

Several studies have documented the role of growth factors in periodontal regeneration. It has been shown that platelet-derived growth factor (PDGF) is a potent stimulator of human periodontal ligament (PDL) cells. A variety of bone graft materials are used to treat osseous defects caused by periodontal disease. We evaluated the mitogenic effect of PDGF on human PDL cells cultured with different allografts to determine which of the allografts with or without PDGF promoted periodontal regeneration.

METHODS

Two human demineralized freeze-dried allografts of cortical (DFDBA) and cancellous (DFBA) bone and a non-demineralized freeze-dried allograft (FBA) from cancellous bone were used alone or supplemented with PDGF-BB. Human PDL cultures were derived from the mid-root of 2 maxillary premolars extracted for orthodontic reasons. Cells were grown separately in 24-well dishes with or without 20 mg of each bone allograft. On day 2 of quiescence, new medium was added with 10 ng/ml of PDGF-BB. DNA synthesis was estimated by measuring [3H] thymidine incorporation to determine the effects of the test agents on cell proliferation. Cells were processed and subjected to scintillation counting after 48 hours of incubation. Counts per minute (cpm/well) were determined for each sample.

RESULTS

There was no statistically significant difference (P<0.05) on PDL cell proliferation when the allografts were used alone. PDL cells exhibited significantly greater proliferative responses to the 2 demineralized bone allografts, DFDBA and DFBA, when combined with PDGF-BB. A statistically significant difference on DNA synthesis was noticed when PDGF-BB was added to PDL cells cultured with FBA. PDL cells displayed no significant increase in mitogenic activity when cultured with PDGF-BB alone.

CONCLUSIONS

The findings of this study demonstrate the beneficial role of DFDBA, DFBA, and FBA as synergic agents with PDGF-BB to periodontal regeneration. The significant ability of the 2 decalcified bone allografts, DFDBA and DFBA, combined with PDGF to stimulate PDL cell proliferation might be a useful adjunct in the treatment of periodontal defects.

Bone growth factors in maxillofacial skeletal reconstruction

A literature review was performed to survey the available information on the potential of bone growth factors in skeletal reconstruction in the maxillofacial area. The aim of this review was to characterize the biological and developmental nature of the growth factors considered, their molecular level of activity and their osteogenic potential in craniofacial bone repair and reconstruction. A total of 231 references were selected for evaluation by the content of the abstracts. All growth factors considered have a fundamental role in growth and development. In postnatal skeletal regeneration, PDGF plays an important role in inducing proliferation of undifferentiated mesenchymal cells. It is an important mediator for bone healing and remodelling during trauma and infection. It can enhance bone regeneration in conjunction with other growth factors but is unlikely to provide entirely osteogenic properties itself. IGFs have an important role in general growth and maintenance of the body skeleton. The effect of local application of IGFs alone in craniofacial skeletal defects has not yet shown a clear potential for enhancement of bone regeneration in the reported dosages. The combination of IGF-I with PDGF has been effective in promoting bone regeneration in dentoalveolar defects around implants or after periodontal bone loss. TGFbeta alone in skeletal reconstruction appears to be associated with uncertain results. The presence of committed cells is required for enhancement of bone formation by TGFbeta. It has a biphasic effect, which suppresses proliferation and osteoblastic differentiation at high concentrations. BMPs, BMP2, BMP4 and BMP7 in particular, appear to be the most effective growth factors in terms of osteogenesis and osseous defect repair. Efficacy of BMPs for defect repair is strongly dependent on the type of carrier and has been subject to unknown factors in clinical feasibility trials resulting in ambiguous results. The current lack of clinical data may prolong the period until this factor is introduced into routine clinical application. PRP is supposed to increase proliferation of undifferentiated mesenchymal cells and to enhance angiogenesis. There is little scientific evidence about the benefit of PRP in skeletal reconstructive and preprosthetic surgery yet and it is unlikely that peri-implant bone healing or regeneration of local bone into alloplastic material by the application of PRP alone will be significantly enhanced.

Platelet-rich plasma and bovine porous bone mineral combined with guided tissue regeneration in the treatment of intrabony defects in humans

BACKGROUND

A combination of platelet-rich plasma (PRP), bovine porous bone mineral (BPBM) and guided tissue regeneration (GTR) has been shown to be effective in promoting clinical signs of periodontal regeneration in intrabony defects. As an initial attempt to clarify the role played by each of the three treatment components, this study was performed to compare the clinical effectiveness of two regenerative techniques for intrabony defects in humans: a combination of PRP/BPBM/GTR vs. GTR.

MATERIAL AND METHODS

Eighteen patients participated in the study. Using a split-mouth design, interproximal bony defects were surgically treated with either an absorbable membrane made of polylactic acid for GTR or a combination of PRP/BPBM/GTR. Changes in pocket depth, attachment level and defect fill as revealed by 6-month reentry surgeries were evaluated.

RESULTS

Both treatment modalities resulted in significant pocket depth reduction and clinical attachment gain as compared to baseline values. Pocket depth reduction was 4.98 +/- 0.96 mm on buccal and 4.93 +/- 0.92 mm on lingual sites of the PRP/BPBM/GTR group and 3.62 +/- 0.81 mm on buccal and 3.54 +/- 0.88 mm on lingual sites of the GTR group. The gain in clinical attachment observed was 4.37 +/- 1.31 mm on buccal and 4.28 +/- 1.33 mm on lingual sites of the PRP/BPBM/GTR group and 2.62 +/- 1.23 mm on buccal and 2.44 +/- 1.21 mm on lingual sites of the GTR group. The amount of defect fill observed was 4.78 +/- 1.26 mm on buccal and 4.66 +/- 1.32 mm on lingual sites of the PRP/BPBM/GTR group and 2.31 +/- 0.76 mm on buccal and 2.26 +/- 0.81 mm on lingual sites of the GTR group. All differences between the two groups were statistically significant in favor of the PRP/BPBM/GTR group.

CONCLUSIONS

The results of this study suggest that PRP and BPBM provide an added regenerative effect to GTR in promoting the clinical resolution of intrabony defects on patients with severe periodontitis.

Platelet-derived growth factor BB secreted from osteoclasts acts as an osteoblastogenesis inhibitory factor

Osteoclasts and osteoblasts are responsible for strict bone maintenance with a balance between bone formation and resorption by interacting with each other. Recently, it has been revealed that osteoblasts/stromal cells regulate differentiation of osteoclasts/hematopoietic cells by two factors, the receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL) on the plasma membrane, and secreted osteoprotegerin (OPG). However, no factors have yet been reported by which osteoclasts/hematopoietic cells regulate osteoblasts/stromal cells. To elucidate the possibility of signal transduction from osteoclasts to osteoblasts, we studied the conditioned medium of mouse osteoclast-like myeloma cell line RAW264.7 treated with RANKL. We found that this medium contains a factor that inhibits differentiation of mouse osteoblast precursor-like cell line MC3T3-E1 to osteoblasts induced by bone morphogenetic protein 4 (BMP-4) and named this factor osteoblastogenesis inhibitory factor (OBIF). OBIF was purified by successive three-step chromatography by heparin affinity, anion exchange, and reversed-phase columns. Osteoblastogenesis inhibitory activity made one peak in each chromatography step, showing the factor is a single entity. Active fractions were loaded on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and bands of proteins were excised, digested by trypsin, and analyzed by liquid chromatography equipped with tandem mass spectrometry (LC/MS/MS). Consequently, we have identified this factor to be platelet-derived growth factor BB (PDGF BB) homodimer. Furthermore, this identification of PDGF BB as OBIF was confirmed by neutralization of the inhibitory activity of the medium with anti-PDGF antibody. These results show, for the first time, that osteoclasts regulate osteoblasts directly and suggest that PDGF BB is a key factor in bone remodeling.