Insulin-like growth factor system components in the periodontium during tooth root resorption and early repair processes in the rat

IGFs in Dentin Formation and Regeneration: Progress and Remaining Challenges

Tertiary dentin results from the interplay between the host defense and dental injury or infection. Modern endodontics aiming vital pulp treatment take the tertiary dentin formation as the interim step, with the final goal of a physiological pulp-dentin like tissue regeneration. Dental pulp stem cells have been nominated for contributing to differentiating into odontoblast-like cells who are responsible for reparative dentin formation. Understanding the original dentin formation mechanism provides us a blueprint while exploring the reparative dentin formation mechanism builds bridge to bonafide pulp-dentin tissue regeneration. Among all the regulators, growth factors have long been revealed under the spotlight. The insulin-like growth factor (IGF) family has been implicated in critical events of inducing dentin formation, which is essential for pulp treatment. The expression of IGF family members including IGF1, IGF1R, IGF2, and IGF2R has been well characterized in dental papilla cells, dental pulp stem cells, and periodontal ligament cells. Recent studies indicated IGF binding to the receptors activated pathways, including MAPK pathway, and AKT pathway, orchestrated proliferation, and differentiation, and finally, contributed to dentin formation. This review summarizes the role of IGF family in dentin formation during tooth development and tertiary dentin formation during dentin-pulp repair and sheds light on key parts of research for future treatment improvements.

Periodontal Wound Healing and Regeneration: Insights for Engineering New Therapeutic Approaches

Periodontitis is a widespread inflammatory disease that leads to loss of the tooth supporting periodontal tissues. The few therapies available to regenerate periodontal tissues have high costs and inherent limitations, inspiring the development of new approaches. Studies have shown that periodontal tissues have an inherent capacity for regeneration, driven by multipotent cells residing in the periodontal ligament (PDL). The purpose of this review is to describe the current understanding of the mechanisms driving periodontal wound healing and regeneration that can inform the development of new treatment approaches. The biologic basis underlying established therapies such as guided tissue regeneration (GTR) and growth factor delivery are reviewed, along with examples of biomaterials that have been engineered to improve the effectiveness of these approaches. Emerging therapies such as those targeting Wnt signaling, periodontal cell delivery or recruitment, and tissue engineered scaffolds are described in the context of periodontal wound healing, using key in vivo studies to illustrate the impact these approaches can have on the formation of new cementum, alveolar bone, and PDL. Finally, design principles for engineering new therapies are suggested which build on current knowledge of periodontal wound healing and regeneration.

The Role of GH/IGF Axis in Dento-Alveolar Complex from Development to Aging and Therapeutics: A Narrative Review

The GH/IGF axis is a major regulator of bone formation and resorption and is essential to the achievement of normal skeleton growth and homeostasis. Beyond its key role in bone physiology, the GH/IGF axis has also major pleiotropic endocrine and autocrine/paracrine effects on mineralized tissues throughout life. This article aims to review the literature on GH, IGFs, IGF binding proteins, and their respective receptors in dental tissues, both epithelium (enamel) and mesenchyme (dentin, pulp, and tooth-supporting periodontium). The present review re-examines and refines the expression of the elements of the GH/IGF axis in oral tissues and their in vivo and in vitro mechanisms of action in different mineralizing cell types of the dento-alveolar complex including ameloblasts, odontoblasts, pulp cells, cementoblasts, periodontal ligament cells, and jaw osteoblasts focusing on cell-specific activities. Together, these data emphasize the determinant role of the GH/IGF axis in physiological and pathological development, morphometry, and aging of the teeth, the periodontium, and oral bones in humans, rodents, and other vertebrates. These advancements in oral biology have elicited an enormous interest among investigators to translate the fundamental discoveries on the GH/IGF axis into innovative strategies for targeted oral tissue therapies with local treatments, associated or not with materials, for orthodontics and the repair and regeneration of the dento-alveolar complex and oral bones.

The tendency of reduced periodontal destruction in acromegalic patients showing similar inflammatory status with periodontitis patients

PURPOSE

Evaluate periodontal status of acromegalics through clinical and biochemical variables.

METHODS

Demographics, hormone and metabolic variables, periodontal variables, gingival crevicular fluid (GCF) volume, and content data were collected from 30 patients with acromegaly, 30 patients with periodontitis, and 20 healthy subjects and comparatively analyzed.

RESULTS

GH differences between acromegaly (2.56 ± 4.86) and periodontitis (0.53 ± 0.95) (p < 0.001) were statistically significant. IGF-1 was lowest at periodontitis (113.31 ± 45.01) and lower (152.11 ± 45.56) at healthy group compared with acromegalics (220.38 ± 167.62) (p < 0.05). GH and IGF-1 had positive correlation (p < 0.05). IGF-1 and CAL had negative (p < 0.01) correlation except healthy group that showed the same correlation at the opposite direction (p < 0.05). Besides similar plaque and gingival indices with periodontitis, acromegalics showed relatively less CAL and GCF volume but except CAL, all their periodontal variables were higher than healthy subjects. GCF GH and prolactin showed higher values in acromegalics while healthy subjects showed relatively high interleukin-1, -10 and carboxyterminal telopeptide of type I collagen compared with others.

CONCLUSION

Acromegalics have a tendency of slowed periodontal destruction with an influence of GH and IGF-1 to the inflammation- and collage metabolism-related mechanisms rather than bone-associated ones. However, this information must be confirmed with further studies exploring the mechanisms possibly bonded to others.

Regulation of IGF-I by IGFBP3 and IGFBP5 during odontoblast differentiation in mice

OBJECTIVES

Although intracellular signaling pathways of insulin-like growth factor I (IGF-I) related to the proliferation of dental pulp cells have been investigated, the switching mechanism from cell proliferation to differentiation during odontogenesis remains elusive. This study aimed to elucidate the role of IGF binding protein (IGFBP) 3 and 5 in regulation of IGF-I during odontoblast differentiation in mouse incisors.

METHODS

The detailed expression patterns of IGF-I, IGF-I receptor (IGF-IR), IGFBP3, and IGFBP5 together with that of an odontoblast differentiation marker, nestin, were examined by immunohistochemistry and/or in situ hybridization using paraffinized sections of TetOP-H2B-GFP mouse incisors at postnatal 4 weeks.

RESULTS

Undifferentiated dental papilla cells and preodontoblasts (preOB) showed intense IGF-I- and IGF-IRα-positive reactions, and the expression was observed in differentiated odontoblasts, such as immature odontoblasts (iOB) and mature odontoblasts (mOB). IGFBP3/Igfbp3 was transiently expressed in preOB and early iOB, and the intensity of expression gradually reduced with the progression of odontoblast differentiation. In contrast, immunohistochemical analysis for IGFBP5 identified a positive reaction in the undifferentiated dental papilla cells and differentiated odontoblasts, and the expression of Igfbp5 was reduced in the differentiated odontoblasts.

CONCLUSION

The present study demonstrated the expression patterns of IGF-I, IGF-IR, IGFBP3, and IGFBP5 during odontoblast differentiation in mouse incisors. These results suggested that IGFBP3 regulates the transition from the proliferative to differentiation stage by inhibiting the action of IGF-I on the proliferation of dental papilla cells, and that IGFBP5 plays an important role in the maintenance of the differentiated odontoblasts during tooth development.

Evaluation of Hypoxia on the Expression of miR-646/IGF-1 Signaling in Human Periodontal Ligament Cells (hPDLCs)

Background

This study aims to investigate the role of miR-646 in hypoxia conditions in human periodontal ligament cells (hPDLCs), exploring the effect of hypoxia on hPDLCs proliferation and apoptosis. In addition, this study aimed to explore the potential mechanism of miR-646/IGF-1 signaling in hPDLCs in hypoxia conditions.

Material/Methods

hPDLCs (fifth passage) cultured by the tissue culture method were randomly assigned to the severe hypoxia (1% O₂) group, the slight hypoxia (5% O₂) group or the control (21% O₂) group. Then reverse transcription quantitative real-time polymerase chain reaction and western blot analysis were used to detect the mRNA and protein expression of miR-646 and IGF-1. hPDLCs infected with lentivirus (LV)-pre-miR-646 or LV-anti-mR-646, and negative controls were cultured. MTT assay, caspase-3 ELISA assay, and wound healing assay were performed to evaluate how miR-646 was influenced by hypoxia. In addition, the relationship between miR-646 and IGF-1 was explored.

Results

The expression of miR-646 was downregulated and IGF-1 was upregulated in hypoxia conditions. MiR-646 was able to suppress hPDLCs proliferation and promote apoptosis in hypoxia conditions. The mRNA and protein expressions of IGF-1 were downregulated when miR-646 was overexpressed and upregulated when miR-646 was downregulated.

Conclusions

This finding identified a significant role of miR-646 in hPDLCs in suppressing cell proliferation and promoting apoptosis by inversely regulating IGF-1 expression. Meanwhile, the regulation of hPDLCs in hypoxia may be through the miR-646/IGF-1 signaling pathway, probably serving as a promising therapeutic target for periodontal diseases.

Insulin-Like Growth Factor Axis Expression in Dental Pulp Cells Derived From Carious Teeth

The insulin-like growth factor (IGF) axis plays an important role in dental tissue regeneration and most components of this axis are expressed in human dental pulp cells (DPCs). In our previous study, we analyzed IGF axis gene expression in DPCs and demonstrated a novel role of IGF binding protein (IGFBP)-2 and -3 in coordinating mineralized matrix formation in differentiating DPCs. A more recent study from our laboratory partially characterized dental pulp stem cells from teeth with superficial caries (cDPCs) and showed that their potential to differentiate odontoblasts and/or into osteoblasts is enhanced by exposure to the mild inflammatory conditions characteristic of superficial caries. In the present study, we examine whether changes apparent in IGF axis expression during osteogenic differentiation of healthy DPCs are also apparent in DPCs derived from carious affected teeth.

Reduced Orthodontic Tooth Movement in Enpp1 Mutant Mice with Hypercementosis

Previous studies revealed that cementum formation is tightly regulated by inorganic pyrophosphate (PP_i), a mineralization inhibitor. Local PP_i concentrations are determined by regulators, including ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which increases PP_i concentrations by adenosine triphosphate hydrolysis. Orthodontic forces stimulate alveolar bone remodelling, leading to orthodontic tooth movement (OTM). To better understand how disturbed mineral metabolism and the resulting altered periodontal structures affect OTM, we employed Enpp1 mutant mice that feature reduced PP_i and increased cervical cementum in a model of OTM induced by a stretched closed-coil spring ligated between the maxillary left first molar and maxillary incisors. We analyzed tooth movement, osteoclast/odontoclast response, and tooth root resorption by micro-computed tomography, histology, histomorphometry, and immunohistochemistry. Preoperatively, we noted an altered periodontium in Enpp1 mutant mice, with significantly increased periodontal ligament (PDL) volume and thickness, as well as increased PDL-bone/tooth root surface area, compared to wild-type (WT) controls. After 11 d of orthodontic treatment, Enpp1 mutant mice displayed 38% reduced tooth movement versus WT mice. Molar roots in Enpp1 mutant mice exhibited less change in PDL width in compression and tension zones compared to WT mice. Root resorption was noted in both groups with no difference in average depths, but resorption lacunae in Enpp1 mutant mice were almost entirely limited to cementum, with 150% increased cementum resorption and 92% decreased dentin resorption. Osteoclast/odontoclast cells were reduced by 64% in Enpp1 mutant mice, with a predominance of tartrate-resistant acid phosphatase (TRAP)-positive cells on root surfaces, compared to WT mice. Increased numbers of TRAP-positive cells on root surfaces were associated with robust immunolocalization of osteopontin (OPN) and receptor-activator of NF-κB ligand (RANKL). Collectively, reduced response to orthodontic forces, decreased tooth movement, and altered osteoclast/odontoclast distribution suggests Enpp1 loss of function has direct effects on clastic function/recruitment and/or indirect effects on periodontal remodeling via altered periodontal structure or tissue mineralization.

IGFBP-2 and -3 co-ordinately regulate IGF1 induced matrix mineralisation of differentiating human dental pulp cells

Human dental pulp cells (DPCs), which are known to contain a subset of stem cells capable of reforming a dentin and pulp-like complex upon in vivo transplantation, were isolated from third molars of three healthy donors and differentiated to a matrix mineralisation phenotype using by culture in dexamethasone and l-ascorbic acid. qRT-PCR analysis of insulin-like growth factor ( IGF) axis gene expression indicated that all genes, except insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein-1 ( IGFBP-1), were expressed in DPCs. During differentiation upregulation of insulin-like growth factor binding protein-2 (IGFBP-2) and downregulation of insulin-like growth factor binding protein-3 (IGFBP-3) expression was observed. Changes in IGFBP-2 and IGFBP-3 mRNA expression were confirmed at the protein level by ELISA of DPC conditioned medium functional analysis indicated that IGF1 stimulated the differentiation of DPCs and that the activity of the growth factor was enhanced by pre-complexation with IGFBP-2 but inhibited by pre-complexation with IGFBP-3. Therefore changes in IGFBP-2 and -3 expression during differentiation form part of a co-ordinated functional response to enhance the pro-differentiative action of IGF1 and represent a novel mechanism for the regulation of DPC differentiation.

The Effect of An Angiogenic Cytokine on Orthodontically Induced Inflammatory Root Resorption

Objective

Orthodontically induced inflammatory root resorption (OIIRR) is an undesirable sequel of tooth movement after sterile necrosis that takes place in periodontal ligament due to blockage of blood vessels following exertion of orthodontic force. This study sought to assess the effect of an angiogenic cytokine on OIIRR in rat model.

Materials and Methods

In this experimental animal study, 50 rats were randomly divided into 5 groups of 10 each: E10, E100 and E1000 receiving an injection of 10, 100 and 1000 ng of basic fibroblast growth factor (bFGF), respectively, positive control group (CP) receiving an orthodontic appliance and injection of phosphate buffered saline (PBS) and the negative control group (CN) receiving only the anesthetic agent. A nickel titanium coil spring was placed between the first molar and the incisor on the right side of maxilla. Twenty-one days later, the rats were sacrificed. Histopathological sections were made to assess the number and area of resorption lacunae, number of blood vessels, osteoclasts and Howship’s lacunae. Data were statistically analyzed using ANOVA and Tukey’s honest significant difference (HSD) test.

Results

Number of resorption lacunae and area of resorption lacunae in E1000 (0.97 ± 0.80 and 1. 27 ± 0.01×10^-3, respectively) were significantly lower than in CP (4.17 ± 0.90 and 2.77 ± 0.01×10-3, respectively, P=0.000). Number of blood vessels, osteoclasts and Howship’s lacunae were significantly higher in E1000 compared to CP (P<0.05).

Conclusion

Tooth movement as the outcome of bone remodeling is concomitant with the formation of sterile necrosis in the periodontal ligament following blocked blood supply. Thus, bFGF can significantly decrease the risk of root resorption by providing more oxygen and angiogenesis.

Role of Periostin in Adhesion and Migration of Bone Remodeling Cells

Periostin is an extracellular matrix protein highly expressed in collagen-rich tissues subjected to continuous mechanical stress. Functionally, periostin is involved in tissue remodeling and its altered function is associated to numerous pathological processes. In orthodontics, periostin plays key roles in the maintenance of dental tissues and it is mainly expressed in those areas where tension or pressing forces are taking place. In this regard, high expression of periostin is essential to promote migration and proliferation of periodontal ligament fibroblasts. However little is known about the participation of periostin in migration and adhesion processes of bone remodeling cells. In this work we employ the mouse pre-osteoblastic MC3T3-E1 and the macrophage-like RAW 264.7 cell lines to overexpress periostin and perform different cell-based assays to study changes in cell behavior. Our data indicate that periostin overexpression not only increases adhesion capacity of MC3T3-E1 cells to different matrix proteins but also hampers their migratory capacity. Changes on RNA expression profile of MC3T3-E1 cells upon periostin overexpression have been also analyzed, highlighting the alteration of genes implicated in processes such as cell migration, adhesion or bone metabolism but not in bone differentiation. Overall, our work provides new evidence on the impact of periostin in osteoblasts physiology.

Effect of PDGF-BB, IGF-I growth factors and their combination carried by liposomes in tooth socket healing

This work evaluated the bone-forming potential of the platelet-derived growth factor isoform BB (PDGF-BB), insulin-like growth factor I (IGF-I), and mixed PDGF-BB/IGF-I delivered in liposomes compared with phosphate buffered saline (PBS), in the healing process of rat tooth sockets. One hundred and twelve Wistar rats were randomized into 7 groups of 16 animals each and were evaluated at 3, 7, 14 and 21 days after extraction of the maxillary second molars. The left sockets were treated with PBS (P), empty liposome (L), IGF-I in PBS (IP), IGF-I in liposome (IL), PDGF-BB in PBS (PDP), PDGF-BB in liposome (PDL) and both growth factors (GFs) together within liposomes (PDIL). The right sockets were filled with blood clot (BC). Histological and histomorphometric analyses were used to evaluate the formation of new bone and blood vessels. Immunohistochemistry was performed to evaluate the expression of osteocalcin and vascular endothelial growth factor (VEGF) during bone repair. Data were tested statistically using a Tukey's test according to a Dunn's analysis and Mann-Whitney U test followed by Kruskal-Wallis one-way analysis. Results were considered significant when p<0.05. A significantly higher percentage of bone trabeculae and a higher number of blood vessels were observed in the IL, PDL and PDIL groups (p<0.05). However, these GF-liposome groups had statistically similar results. Immunohistochemical assays first detected osteocalcin and VEGF expression at 3 days followed by a peak at 7 days. Lower immunoreactivity levels were observed in the BC, L, P, IP and PDP groups compared with the IL, PDL and PDIL groups (p<0.05). The results suggest that GFs carried by liposomes, either in isolated or mixed forms, enhanced the healing process in rat tooth sockets. The differential expression of the osteogenic markers VEGF and osteocalcin in the early phases of bone healing support these findings.

Intermittent Compressive Stress Enhanced Insulin-Like Growth Factor-1 Expression in Human Periodontal Ligament Cells

Mechanical force was shown to promote IGF-1 expression in periodontal ligament both in vitro and in vivo. Though the mechanism of this effect has not yet been proved, here we investigated the molecular mechanism of intermittent mechanical stress on IGF-1 expression. In addition, the role of hypoxia on the intermittent compressive stress on IGF-1 expression was also examined. In this study, human periodontal ligament cells (HPDLs) were stimulated with intermittent mechanical stress for 24 hours. IGF-1 expression was examined by real-time polymerase chain reaction. Chemical inhibitors were used to determine molecular mechanisms of these effects. For hypoxic mimic condition, the CoCl2 supplementation was employed. The results showed that intermittent mechanical stress dramatically increased IGF-1 expression at 24 h. The pretreatment with TGF-β receptor I or TGF-β1 antibody could inhibit the intermittent mechanical stress-induced IGF-1 expression. Moreover, the upregulation of TGF-β1 proteins was detected in intermittent mechanical stress treated group. Correspondingly, the IGF-1 expression was upregulated upon being treated with recombinant human TGF-β1. Further, the hypoxic mimic condition attenuated the intermittent mechanical stress and rhTGF-β1-induced IGF-1 expression. In summary, this study suggests intermittent mechanical stress-induced IGF-1 expression in HPDLs through TGF-β1 and this phenomenon could be inhibited in hypoxic mimic condition.

The effects of low-level laser therapy on orthodontically induced root resorption

The aim of this study was to evaluate the preventive and/or reparative effects of low-level laser therapy (LLLT) on orthodontically induced inflammatory root resorption (OIIRR) in rats. Thirty rats were divided into four groups (short-term control (SC), short-term laser (SL), long-term control (LC), long-term laser (LL)). In all groups, the left first molar was moved mesially for 11 days. At the end of this period, the rats in groups SC and SL were killed in order to observe the resorption lacunas and to evaluate whether LLLT had any positive effect on root resorption. The groups LC and LL were remained for a healing period of 14 days in order to observe spontaneous repair of the resorption areas and investigate whether LLLT had reparative effects on root resorption. A Ga-Al-As diode laser (Doris, CTL-1106MX, Warsaw, Poland) with a wavelength of 820 nm was used. In SL group, the first molars were irradiated with the dose of 4.8 J/cm2 (50 mW, 12 s, 0.6 J) on every other day during force application. In LL group, the irradiation period was started on the day of appliance removal and the first molars were irradiated with the dose of 4.8 J/cm2 on every other day for the next 14 days. LLLT significantly increased the number of osteoblasts and fibroblasts, and inflammatory response in SL group in comparison with SC group (P = .001). The amount of resorption did not represent any difference between the two groups (P = .16). In LL group, LLLT significantly increased the number of fibroblasts and decreased the amount of resorption in comparison with LC group (P = .001; P = .02). Both parameters indicating the reparative and the resorptive processes were found to be increased by LLLT applied during orthodontic force load. LLLT applied after termination of the orthodontic force significantly alleyed resorption and enhanced/accelerated the healing of OIIRR. LLLT has significant reparative effects on OIIRR while it is not possible to say that it definitely has a preventive effect.

Receptor activator of nuclear factor-kappa ligand, OPG, and IGF-I expression during orthodontically induced inflammatory root resorption in the recombinant human growth hormone-treated rats

OBJECTIVE

To investigate the effects of growth hormone (GH) on local receptor activator of nuclear factor-kappa ligand (RANKL), OPG, and IGF-I expression during orthodontically induced inflammatory root resorption in rats.

MATERIALS AND METHODS

Forty Wistar rats (gender: male; age: 7 weeks) were randomly divided into control and experimental groups. A force of 50 g was applied to move the right upper first molars mesially. The experimental and control groups received daily subcutaneous injections of recombinant human growth hormone (GH; 2 mg/kg) and equivalent volumes of saline, respectively. The rats were sacrificed on days 1, 3, 7, and 14. Micro-computed tomography-reconstructed images of the upper right first molars were used to survey root resorption and tooth movement. Horizontal sections of the maxillae were prepared for hematoxylin and eosin, tartrate-resistant acid phosphatase, and immunohistochemical staining.

RESULTS

Resorption lacunae appeared on the compressed side of the distal buccal root of the right first molar on days 7 and 14. Compared with the control groups, GH-treated groups showed more RANKL-positive cells and osteoclasts on day 3 and more OPG- and IGF-I-positive cells and fewer odontoclasts on days 7 and 14. Indexes of root resorption were lower and tooth movement was faster in the GH-treated groups than in the control groups on days 7 and 14.

CONCLUSIONS

The inhibitory effect of GH on root resorption by heavy force might be mediated by RANKL/OPG and IGF-I. Short-term GH administration may be a method with which to reduce root resorption and shorten treatment time, especially in patients who are susceptible to root resorption.

Evaluation of the periodontal status in acromegalic patients: a comparative study

Aim. The aim was to compare the periodontal status of the acromegalic patients with healthy subjects from a large population-based cohort (Study of Health in Pomerania, SHIP). Materials and Methods. We studied 32 acromegalic patients (16 females) and 128 randomly selected SHIP subjects (controls) using a 1 : 4 matching. Serum IGF-I and IGFBP-3 levels were measured using the Immulite 2500 system. Periodontitis was assessed by clinical attachment loss (CAL), probing depth (PD), and number of missing teeth. Linear and logistic regression models were used to assess differences in periodontal variables between acromegalic patients and controls. Results. IGF-I levels were comparable in acromegalic patients and controls, whereas IGFBP-3 levels were significantly higher in acromegalic patients (P = 0.004). In multivariate modelling, both groups did not differ significantly with respect to mean CAL (P = 0.12) and high tooth loss (P = 0.36). Mean PD was higher in acromegalic patients by trend (B = 0.28 (-0.00; 0.56)). Conclusion. In acromegalic patients, periodontal disease severity did not differ from their healthy SHIP controls.

Association between the insulin-like growth factor axis in serum and periodontitis in the Study of Health in Pomerania: an exploratory study

AIM

To evaluate the association of Insulin-like Growth Factor (IGF) I-related variables with periodontitis in the population-based Study of Health in Pomerania (SHIP).

MATERIAL AND METHODS

From the cross-sectional SHIP, 2293 subjects with clinical attachment loss (CAL) data and 2398 subjects with tooth count data aged 20-59 years were analysed. Serum IGF-I and IGF-binding protein (BP)-3 levels were determined by chemiluminescence immunoassays. Linear and logistic regressions with fractional polynomials were used to study associations between IGF-related variables and mean CAL or high tooth loss. For non-linear relations between IGFBP-3 and mean CAL, graphical presentations of fractional polynomials were used to deduce knots for linear splines.

RESULTS

In fully adjusted models, for serum IGFBP-3 values ≤1200 ng/ml, mean CAL increased significantly for decreasing serum IGFBP-3 levels [B = -0.027 (95% CI, -0.049; -0.005), p = 0.02]. The odds for high tooth loss decreased significantly for high serum IGFBP-3 values [OR = 0.97 (0.95; 0.99), p = 0.02]. Serum IGF-I levels and the IGF-I/IGFBP-3 ratio were not related to mean CAL or tooth loss after full adjustment.

CONCLUSIONS

Low serum IGFBP-3 levels might be associated with higher levels of periodontal disease. Neither serum IGF-I nor IGF-I/IGFBP-3 ratios were associated with periodontitis.

Potential role of high mobility group box protein 1 and intermittent PTH (1-34) in periodontal tissue repair following orthodontic tooth movement in rats

OBJECTIVES

Recent studies indicate that high mobility group box protein 1 (HMGB1) can be released by necrotic and damaged cells and functions as an alarmin that is recognized by the innate immune system. Little is known about the role of HMGB1 within the periodontal ligament (PDL). Therefore, we examined HMGB1 expression by PDL cells in vitro and compared the findings to an in vivo model of orthodontically induced tooth root resorption. In addition, we addressed the question of whether a potentially anabolic intermittent administration of parathyroid hormone (iPTH) would modulate the expression of HMGB1.

MATERIALS AND METHODS

In confluent PDL cell cultures, HMGB1 messenger RNA (mRNA) expression was quantified by real-time polymerase chain reaction. In a rat model comprising 25 animals, mechanical loading for 5 days was followed by administration of either iPTH (1-34) systemically or sham injections for up to 56 days. HMGB1 expression was determined by means of immunohistochemistry and histomorphometry.

RESULTS

The in vitro experiments revealed an inhibitory effect of iPTH on basal HMGB1 mRNA expression in confluent PDL cells. In vivo, the mechanical force-induced enhanced HMGB1 protein expression declined time dependently. Intermittent PTH further inhibited HMGB1 expression. The significantly higher basal HMGB1 protein expression in the former compression side was followed by a more pronounced time- and iPTH-dependent decline in the same area.

CONCLUSIONS

These data indicate a major role for HMGB1 in the regulation of PDL wound healing following mechanical load-induced tissue injury.

CLINICAL RELEVANCE

The findings point to the potential benefit of iPTH in the attempt to support these immune-associated reparative processes.

Effect of the cyclic stretch on the expression of osteogenesis genes in human periodontal ligament cells

Periodontal ligament cells can potentially differentiate into osteoblast-like cells and influence the remodeling of periodontal tissues under mechanical strain conditions. In the present study, Gene chip technology was adopted to investigate the effect of the cyclic stretch on the expression of osteogenic-related genes in human periodontal ligament cells (HPDLCs). Cultured HPDLCs were subjected to 12% elongation cyclic stretch for 24 h using a Flexercell Strain Unit, and then GEArray Q series human osteogenesis gene expression profile chip with 96 spot array numbers was used to conduct parallel analyses on the change of the related gene expression in the osteogenic differentiation of HPDLCs stimulated by cyclic stretch. The results show that after the HPDLCs were stimulated by the cyclic stretch, the expression of 21 osteogenic-related genes was significantly upregulated, including 10 growth factor genes and their associated molecules, 10 extracellular matrix genes and their associated proteins, and 1 cell adhesion molecule. Two genes were significantly downregulated, including one growth factor gene and one cell adhesion molecule. Then the expressions of 10 candidate genes were validated using Real-time RT-PCR. These results indicate that cyclic stretch with 12% deformation can stimulate or inhibit some gene expression which was associated with the process of HPDLCs differentiation.

Geometric influence of the sagittal and vertical apical base relationship on the ANB angle

OBJECTIVE

The objective of this study consisted in determining the variability of the ANB angle in relation to the position of the A- and B-points in the sagittal vertical plane.

MATERIALS AND METHODS

Using a theoretical model, we varied the position of the cephalometric points A and B in the sagittal vertical plane while its sagittal relationship was kept constant (Wits value = 0 mm). For this purpose, seven lines were erected perpendicular to the occlusal plane on a lateral cephalogram. The position of points A and B were determined on each of the vertical lines by calculating one anterior and one posterior angle in each case. In this way, the positions of all A- and B-points were clearly defined in the sagittal vertical plane.

RESULTS

The characteristic of the ANB angle in the sagittal vertical plane was graphically represented by determining both points A and B using two angles instead of one. This revealed that the ANB angle for the same sagittal base relationship was characterized by major variations depending on the position of the A- and B-points in relation to the anterior cranial base. The larger the SNA and SNB angles were, the larger the corresponding ANB angle. At the same time, the absolute value of ANB increased with the length of the vertical distance between the points A and B.

CONCLUSION

The ANB angle is strongly influenced by geometric factors. Accurate diagnosis of the sagittal base relationship should thus take the individual character of the ANB angle into account.

Anabolic effect of intermittent PTH(1-34) on the local microenvironment during the late phase of periodontal repair in a rat model of tooth root resorption

This study examined the histological changes and possible effects of intermittent parathyroid hormone (PTH) (1-34) treatment during the early and late phase of periodontal repair in a rat model of tooth root resorption. In a total of 70 animals, which either received intermittent PTH(1-34) systemically or sham injections for up to 70 days after discontinuation of an orthodontic force, histological characteristics were correlated to time-dependent distinct expression patterns of osteoprotegerin and receptor activator of nuclear factor kappaB ligand by PDL cells in the former compression and tension side of tooth movement by means of immunohistochemistry and histomorphometrical analysis. The balance of these key regulators of bone remodeling was demonstrated to be shifted in favor of hard tissue repair by intermittent PTH administration, which was demonstrated to exert anabolic effects in several cell culture and animal experiments as well as in humans, in the late phase of repair. These data indicate a role for PDL cells as potent regulators of periodontal repair by modifying the local microenvironment and point to the anabolic potential of an intermittent PTH administration to support these reparative processes.

Cellular and extracellular factors in early root resorption repair in the rat

The aim of this study was to investigate the role of extracellular matrix components, such as collagen type I, fibronectin, and osteopontin (OPN) during cementum repair following experimentally induced tooth movement, and to characterize the cells taking part in the regenerative process. The upper right first molars were moved mesially in 21 three-month-old male Wistar rats using a coil spring with a force of 0.5 N. After 9 days, the appliance was removed and the animals were killed in groups of three immediately after withdrawal of the force and 5, 7, 10, 12, 14, and 17 days later. Three rats served as non-experimental control animals. The maxillae were prepared and processed for histological analysis. Together with the disappearance of the multinucleated odontoclasts from the resorption lacunae, signs of repair were visible 5 days after the release of the orthodontic force. The first signs of cementum repair were seen on day 10. The newly produced cementum was of the acellular extrinsic fibre type (AEFC) and reattachment was achieved with the principal periodontal ligament (PDL) fibres orientated almost perpendicular to the root surface. The initial interface formed between the old and new cementum, as well as the new AEFC, was characterized by a strong immunoreaction with OPN and collagen I antibody, but only a weak immunoreaction with the fibronectin antibody. Only a small number of mononuclear cells, which were involved in the repair process, showed a positive immunoreaction with the osteoblastic lineage markers runt-related transcription factor 2 and osteocalcin. These same cells stained sparsely with muscle segment homeobox homologue 2, but not with the E11 antibody. Thus, most of the cells associated with this reparative activity on the surface of the lacunae were differentiated PDL cells of the fibroblastic phenotype. Cells with a defined osteoblastic phenotype seemed to be of minor importance in this repair process.

High insulinlike growth factor binding protein 1 level predicts incident congestive heart failure in the elderly

BACKGROUND

Low levels of insulinlike growth factor 1 (IGF-I) may influence the development of age-related cardiovascular diseases including congestive heart failure (CHF). Insulinlike growth factor binding protein 1 (IGFBP-1), which increases during catabolic states and inhibits anabolic IGF-I effects, is increased in patients with CHF and has been associated prospectively with increased mortality among older adults and survivors of myocardial infarction. We investigated the association between fasting plasma levels of IGF-I, IGFBP-1, IGFBP-3, and insulin and risk of incident CHF in the prospective Cardiovascular Health Study.

METHODS

From among 5,888 adults 65 years old and older in the Cardiovascular Health Study, we studied 566 incident CHF cases and 1,072 comparison subjects after exclusion of underweight individuals (body mass index <18.5 kg/m(2)) and insulin users. Hazard ratios (HRs) with 95% CIs for CHF were estimated after adjustment for age, race, sex, hypertension, systolic blood pressure, lipid levels, left ventricular hypertrophy, coronary disease, C-reactive protein, health status, diabetes, and body mass index.

RESULTS

High baseline IGFBP-1 level was a significant predictor of CHF, independent of established CHF risk factors and inflammation markers. The HR per SD of IGFBP-1 was 1.22 (95% CI 1.07-1.39, P < .01). Relative to the lowest IGFBP-1 tertile, the HR was 1.29 (95% CI 0.96-1.74, P = .09) for the second IGFBP-1 tertile and 1.47 (95% CI 1.06-2.04; P = .02) for the highest IGFBP-1 tertile (tertile cut points 19.5 and 35.8 ng/mL). Total IGF-I, IGFBP-3, or insulin levels had no association with CHF after adjustment for CHF risk factors.

CONCLUSIONS

High circulating IGFBP-1 level may be a CHF risk factor among older adults.

Bisphosphonates and osteomyelitis of the jaw: a pathogenic puzzle

The maxillary and mandibular bones undergo high-turnover remodeling to maintain mechanical competence. Common dental or periodontal diseases can increase local bone turnover. Bisphosphonates (BPs) accumulate almost exclusively in skeletal sites that have active bone remodeling. The maxillary and mandibular bones are preferential sites for accumulation of BPs, which become buried under new layers of bone and remain biologically inactive for a long time. Surgical odontostomatological procedures create open bony wounds that heal quickly and without infection, as a result of activation of osteoclasts and subsequently osteoblasts. Once BPs are removed from the bone via activation of osteoclasts after a tooth extraction or a periodontal procedure, they induce osteoclast apoptosis. This inhibition of osteoclast bone resorption impairs bone wound healing because of decreased production of cytokines derived from the bone matrix, and the bone is exposed to the risk of osteomyelitis and necrosis. The pathogenic relationship between BPs and osteonecrosis of the jaw is unclear, but there is evidence to indicate an association between high-dose BP treatment and exposure to dental infections or oral surgical procedures. A better knowledge of the interactions between BPs and jaw and maxillary bone biology will improve clinical and therapeutic approaches.

Effects of insulin-like growth factor binding proteins in bone -- a matter of cell and site

The actions of the insulin-like growth factor (IGF)-system are controlled by six IGF-binding proteins (IGFBPs). The IGFBPs are thought to affect local effects of IGF-I and IGF-II due to higher affinity if compared to IGF-I receptors and due to cell-type specific IGFBP expression patterns. It was found in IGFBP knockout models that the IGFBP family is functionally redundant. Thus, functional analysis of potential effects of IGFBPs is dependent on descriptive studies and models of IGFBP overexposure in vitro and in vivo. In the literature, the role of the IGFBPs for bone growth is highly controversial and, to date, no systematic look has been taken at IGFBPs resolving functional aspects of IGFBPs at levels of cell types and specific locations within bones. Since IGFBPs are thought to represent local modulators of the IGF actions and also exert IGF-independent effects, this approach is particularly reasonable on a physiological level. By sorting the huge number of in part controversial results on IGFBP effects in bone present in the literature for distinct cell types and bone sites it is possible to generate a focused, more specific and a less controversial picture of IGFBP functions in bone.

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.