Effects of growth factors and cytokines on osteoblast differentiation

Triiodotironina não aumenta a diferenciação osteogênica reduzida pela idade de células-tronco mesenquimais da medula óssea de ratas

OBJETIVO: Avaliar se a adição de T3 aumenta o potencial osteogênico das células-tronco mesenquimais da medula óssea (CTM-MO) de ratas adultas normais comparado ao de ratas jovens. MATERIAIS E MÉTODOS: CTM-MO foram cultivadas em meio osteogênico e separadas em seis grupos: 1) CTM-MO de ratas jovens; 2) CTM-MO de ratas adultas; 3, 4, 5 e 6) CTM-MO de ratas adultas com T3 nas concentrações de 0,01; 1; 100 e 1000 nM, respectivamente. Foram avaliados: atividade da fosfatase alcalina, conversão do dimetiltiazol (MTT) e síntese de colágeno aos sete, 14 e 21 dias e celularidade e número de nódulos de mineralização aos 21 dias de diferenciação. RESULTADOS: T3 reduziu significativamente a conversão do MTT, a atividade da fosfatase alcalina, a síntese de colágeno e a formação dos nódulos de mineralização em pelo menos uma das doses e dos períodos estudados (p < 0,05). Os valores foram menores quando comparados aos das CTM-MO de ratas jovens e adultas sem T3 (p < 0,05). CONCLUSÃO: T3 apresenta efeitos negativos sobre os fatores envolvidos na diferenciação osteogênica das CTM-MO de ratas adultas.

Mesenchymal stem cell osteodifferentiation in response to alternating electric current

The present study addressed adult human mesenchymal stem cell (MSC) differentiation toward the osteoblastic lineage in response to alternating electric current, a biophysical stimulus. For this purpose, MSCs (chosen because of their proven capability for osteodifferentiation in the presence of select bone morphogenetic proteins) were dispersed and cultured within electric-conducting type I collagen hydrogels, in the absence of supplemented exogenous dexamethasone and/or growth factors, and were exposed to either 10 or 40 μA alternating electric current for 6 h per day. Under these conditions, MSCs expressed both early- (such as Runx-2 and osterix) and late- (specifically, osteopontin and osteocalcin) osteogenic genes as a function of level, and duration of exposure to alternating electric current. Compared to results obtained after 7 days, gene expression of osteopontin and osteocalcin (late-osteogenic genes) increased at day 14. In contrast, expression of these osteogenic markers from MSCs cultured under similar conditions and time periods, but not exposed to alternating electric current, did not increase as a function of time. Most importantly, expression of genes pertinent to the either adipogenic (specifically, Fatty Acid Binding Protein-4) or chondrogenic (specifically, type II collagen) pathways was not detected when MSCs were exposed to the aforementioned alternating electric-current conditions tested in the present study. The present research study was the first to provide evidence that alternating electric current promoted the differentiation of adult human MSCs toward the osteogenic pathway. Such an approach has the yet untapped potential to provide critically needed differentiated cell supplies for cell-based assays and/or therapies for various biomedical applications.

Enhanced osteogenesis of human mesenchymal stem cells by periodic heat shock in self-assembling peptide hydrogel

The mechanisms for the heat-induced osteogenesis are not completely known and the thermal regulation of human mesenchymal stem cell (hMSC) differentiation is not well studied. In this study, the direct effects of mild heat shock (HS) on the differentiation of hMSCs into osteoblasts in self-assembling peptide hydrogel and on tissue culture plates were investigated. hMSCs isolated from human bone marrow were seeded in conventional culture plates (two-dimensional [2D] culture) and on the surface of three-dimensional (3D) PuraMatrix peptide hydrogel (3D culture), followed by 1 h HS at 41°C once a week during osteogenic differentiation. Alkaline phosphatase (ALP) activity was enhanced in both 2D and 3D cultures via periodic HS at early stage of differentiation; meanwhile, HS significantly increased the calcium deposition at day 19 and 27 of differentiation in both 2D and 3D cultures. The periodic HS also upregulated osteo-specific genes, osterix (OSX) on day 11, osteopontin (OP) on day 19, and bone morphogenetic protein 2 (BMP2) on day 25 in 2D culture. In 3D PuraMatrix culture, the runt-related transcription factor 2 (Runx2) was upregulated by HS on day 25 of differentiation. The heat shock protein 70 (HSP70) was significantly upregulated by HS in differentiated hMSCs analyzed at 24 h after HS. These results demonstrate that HS induced an earlier differentiation of hMSCs and enhanced the maturation of osteoblasts differentiated from hMSCs. Therefore, mild HS treatment may be potentially used to enhance the bone regeneration using hMSCs. Our data will guide the design of in vivo heating protocols and enable further investigations in thermal treatments of MSC osteogenesis for bone tissue engineering.

Osteogenic differentiation of human dental pulp stromal cells on 45S5 Bioglass® based scaffolds in vitro and in vivo

The increasing clinical demand for bone substitutes has driven significant progress in cell-based therapies for bone tissue engineering. The underpinning goals for success are to identify the most appropriate cell source and to provide three-dimensional (3D) scaffolds that support cell growth and enhance osteogenic potential. In this study, human dental pulp stromal cells (HDPSCs) were cultured under basal or osteogenic conditions either in monolayers or on 3D Bioglass® scaffolds in vitro for 2 or 4 weeks. Cell-scaffold constructs were also implanted intraperitoneally in nude mice for 8 weeks. Osteogenic potential was assessed using quantitative real-time polymerase chain reaction and histological/immunohistochemical assays. In monolayer culture, osteoinductive conditions enhanced HDPSC expression of osteogenic gene markers (COL1A1, RUNX2, OC, and/or OCN) compared with basal conditions while culture of HDPSCs on 3D scaffolds promoted osteogenic gene expression compared with monolayer culture under both basal and osteogenic conditions. These results were confirmed using histological and immunohistochemical analyses. In vivo implantation of the HDPSC 3D Bioglass constructs showed evidence of sporadic woven bone-like spicules and calcified tissue. In conclusion, this study has demonstrated the potential of using a combination of HDPSCs with 3D 45S5 Bioglass scaffolds to promote bone-like tissue formation in vitro and in vivo, offering a promising approach for clinical bone repair and regeneration.

Ephrin-B stimulation of calvarial bone formation

INTRODUCTION

Ephrin-B2 on osteoclasts was reported to promote bone formation as part of homeostasis by activating the EphB4 tyrosine kinase receptor on osteoblasts. Little is known about the role of ephrin-B signaling to EphBs in developmental bone formation.

RESULTS

We observed expression of an ephrin-B2 LacZ chimeric allele in the periosteum, sutural bone fronts, and dura mater of embryonic and neonatal mice. Expression in the adult skull was confined to sutures, but was heavily upregulated at sites of bone injury. Culture of embryonic calvariae with soluble recombinant ephrin-B2/Fc doubled their bone content without altering suture width or overall skull morphology. Ephrin-B2/Fc also stimulated osteoblast marker gene expression in cultured MC3T3 preosteoblastic cells without the need for type 1 collagen-induced differentiation. EphB4 was absent in embryonic and adult skulls. However, EphB1 and EphB2, both physiological receptors for ephrin-Bs, were expressed at sites of osteogenesis, and EphB1 knockout mice displayed a reduction in calvarial bone content compared to controls.

CONCLUSIONS

These data support a role for ephrin-B2 in the development and healing of bone through activation of osteoblast-specific gene expression. EphB1 and EphB2 are likely candidates receptors for the ephrin-B2 in bone.

Bone cells from patients with quiescent Crohn's disease show a reduced growth potential and an impeded maturation

Patients with Crohn's disease (CD) are at increased risk of developing osteoporosis. The mechanism underlying bone loss in CD patients is only partly understood. Inflammation is thought to contribute by causing a disturbed bone remodeling. In this study, we aimed to compare functional characteristics of osteoblasts from CD patients and controls, as osteoblasts are one of the effector cells in bone remodeling. The study included 18 patients with quiescent CD and 18 healthy controls. Bone cells obtained from iliac crest biopsies were cultured in the absence and presence of the inflammatory cytokines IL-1α, IL-1β, IL-6, TNF-α, IL-10, and TGF-β. At various time points, cell proliferation and differentiation were analyzed. Bone cells from CD patients showed a prolonged culture period to reach confluence and a decreased cell number at confluence. CD patient-derived bone cell cultures produced higher alkaline phosphatase levels, whereas osteocalcin levels were considerably reduced compared to control cultures. At the proliferation level, the responsiveness to inflammatory cytokines was similar in bone cells from CD patients and controls. At the differentiation level, CD cultures showed an increased responsiveness to IL-6 and a decreased responsiveness to TGF-β. Responsiveness to the other cytokines tested was unaffected. In summary, we show a reduced growth potential and impeded maturation of bone cells from quiescent CD patients in vitro. These disease-related alterations combined with an unchanged sensitivity of CD patient-derived bone cells to inflammatory cytokines, provide a new insight in the understanding of CD-associated bone loss.

The application of bone morphogenetic proteins to periodontal and peri-implant tissue regeneration: A literature review

Progress in understanding the role of bone morphogenetic proteins (BMPs) in craniofacial and tooth development and the demonstration of stem cells in periodontal ligament have set the stage for periodontal regenerative therapy and tissue engineering. Furthermore, recent approval by the Food and Drug Administration of recombinant human BMPs for accelerating bone fusion in slow-healing fractures indicates that this protein family may prove useful in designing regenerative treatments in periodontics. In the near term, these advances are likely to be applied to periodontal surgery; ultimately, they may facilitate approaches to regenerating whole lost periodontal structures.

Cytokine combination therapy prediction for bone remodeling in tissue engineering based on the intracellular signaling pathway

The long-term performance of tissue-engineered bone grafts is determined by a dynamic balance between bone regeneration and resorption. We proposed using embedded cytokine slow-releasing hydrogels to tune this balance toward a desirable final bone density. In this study we established a systems biology model, and quantitatively explored the combinatorial effects of delivered cytokines from hydrogels on final bone density. We hypothesized that: 1) bone regeneration was driven by transcription factors Runx2 and Osterix, which responded to released cytokines, such as Wnt, BMP2, and TGFβ, drove the development of osteoblast lineage, and contributed to bone mass generation; and 2) the osteoclast lineage, on the other hand, governed the bone resorption, and communications between these two lineages determined the dynamics of bone remodeling. In our model, Intracellular signaling pathways were represented by ordinary differential equations, while the intercellular communications and cellular population dynamics were modeled by stochastic differential equations. Effects of synergistic cytokine combinations were evaluated by Loewe index and Bliss index. Simulation results revealed that the Wnt/BMP2 combinations released from hydrogels showed best control of bone regeneration and synergistic effects, and suggested optimal dose ratios of given cytokine combinations released from hydrogels to most efficiently control the long-term bone remodeling. We revealed the characteristics of cytokine combinations of Wnt/BMP2 which could be used to guide the design of in vivo bone scaffolds and the clinical treatment of some diseases such as osteoporosis.

Effects of calcium phosphate endodontic sealers on the behavior of human periodontal ligament fibroblasts and MG63 osteoblast-like cells

In regard to biological properties of endodontic sealers, there are many characteristics that should be considered. The aim of this study was to examine the biological effects of new calcium phosphate-based root canal sealers, CAPSEAL I and CAPSEAL II (CPS), on human periodontal fibroblast cells by examining the expression levels of inflammatory mediators and to compare the effects of CPS on the viability and osteogenic potential of human osteoblast MG63 cells compared to those of other commercially available calcium phosphate sealers [Apatite Root Sealer type I (ARS I) and Apatite Root Sealer III (ARS III); Sankin Kogyo, Tokyo, Japan] and a zinc oxide eugenol-based sealer (Pulp Canal Sealer EWT [PCS EWT]; Kerr, Detroit, MI). The levels of IL-6 in the new CPS group (CAPSEAL I, II) were higher than those in the control and all experimental groups at all time points after 2 h. TGF-β1 and FGF-1 levels decreased at 72 h compared to the levels in the control, in cells treated with every sealers except ARS I. The new CPS sealers showed low cytotoxicity. Reverse transcription polymerase chain reaction showed that CAPSEAL I, II, and Apatite Root Sealer type III induced expression of early stage markers of differentiation (alkaline phosphatase and osteopontin) at 7 days. Also, new CPS showed higher mineralized nodule formation at 28 days. These results suggest that CAPSEAL I and II facilitate the periapical dentoalveolar and alveolar healing by controlling cellular mediators from PDL cells and osteoblast differentiation of precursor cells.

Anabolic Actions of the Regenerative Agent Enamel Matrix Derivative (EMD) in Oral Periosteal Fibroblasts and MG 63 Osteoblasts, Modulation by Nicotine and Glutathione in a Redox Environment

Our study seeks to explore anabolic effects of a periodontal regenerative agent enamel matrix derivative (EMD). Its modulation by nicotine and the anti-oxidant glutathione (GSH) are investigated in human periosteal fibroblasts (HPF) and MG63 osteoblasts. Androgen biomarkers of oxidative stress and healing, resulting from radiolabeled androgen substrates are assayed. This in vitro model simulates a redox environment relevant to the periodontal lesion. It aims to confirm the hypothesis that EMD is an effective regenerative agent in a typically redox environment of the periodontal lesion. Monolayer cultures of MG63 osteoblasts and HPF established in culture medium are incubated with androgen substrates, and optimal concentrations of EMD, nicotine and GSH, alone and in combination. EMD significantly enhances yields of 5α-dihydrotestosterone (DHT) an effective bioactive metabolite, alone and in combination with GSH, to overcome oxidative effects of nicotine across cultures. The ‘in vitro’ findings of this study could be extrapolated to “in vivo” applications of EMD as an adjunctive regenerative therapeutic agent in an environment of chronic inflammation and oxidative stress. Increased yields of DHT implicated in matrix synthesis and direct antioxidant capacity, confirm the potential applications for enamel matrix derivative in periodontal regenerative procedures.

Control of the timing and dosage of IGF-I delivery from encapsulated cells

We report here on the development and characterization of a cell-based system for the regulated delivery of bioactive insulin-like growth factor I (IGF-I). A stable mammalian cell line, CHO-K1 Tet-IGFI, was genetically modified to have tetracycline-induced transcription of the human IGF-I gene. Cells were activated to express IGF-I in the presence of doxycycline (DOX), a tetracycline derivative, while expression was inactivated in the absence of DOX. Temporal, or on-off, release of IGF-I from cells encapsulated within Ca²⁺-alginate hydrogels was demonstrated in a pilot study over the course of 10 days in culture. Released growth factor was bioactive, exhibiting a proliferative effect comparable to recombinant purified IGF-I protein. The dosage levels and temporal control of IGF-I release from encapsulated cells meet the requirements of orthopedic wound repair, making this approach an attractive means for the controlled synthesis and delivery of growth factors in situ for wound healing.

The dynamic healing profile of human periodontal ligament stem cells: histological and immunohistochemical analysis using an ectopic transplantation model

BACKGROUND AND OBJECTIVE

Human periodontal ligament stem cells (hPDLSCs) have been reported to play the pivotal role in periodontal regeneration. However, the dynamic cellular healing process initiated by hPDLSCs still remains to be elucidated. In the present study, the sequence of regeneration by hPDLSCs was assessed using histological and immunohistochemical observation in an ectopic transplantation model, which is a well-standardized assessment tool that excludes the innate healing factors from the animals.

MATERIAL AND METHODS

Human periodontal ligament stem cells that were isolated and characterized from teeth (n=12) extracted for the purpose of orthodontic treatment were transplanted with carriers into ectopic subcutaneous pouches in immunocompromised mice (n=20). Animals were killed after several different healing periods: 3 d (n=4), 1 (n=4), 2 (n=4), 4 (n=4) and 8 wk (n=4). Histological analysis for regenerated tissues formed by hPDLSCs was conducted using hematoxylin and eosin, Masson's trichrome and picrosirius red staining. In addition, immunohistochemical staining was performed to observe the sequential expression of osteogenic/cementogenic and periodontal ligament tissue-specific markers associated with periodontal regeneration.

RESULTS

The whole healing process by transplanted hPDLSCs could be broadly divided into four distinctive phases. In the first phase, proliferated hPDLSCs migrated evenly all over the carrier, and collagenous tissues appeared in the form of amorphous collagen matrices. In the second phase, collagen fibers were well arranged among the carriers, and cementoid-like tissues were observed. In the third phase, the formation of mature collagen fibers, resembling Sharpey's fibers, was associated with active mineralization of cementum-like tissues, and in the fourth phase, the maturation of cementum-like tissues was observed on carrier surfaces. Various osteogenic/cementogenic markers related to the regeneration processes were expressed in a well-orchestrated time order. Interestingly, well-organized cementum-like and periodontal ligament fiber-like tissues and cells with early and late osteogenic/cementogenic markers were frequently observed in the secluded area of carrier surfaces. We termed this area the cell-rich zone.

CONCLUSION

The results from this study clearly demonstrated the sequential histological changes during periodontal tissue regeneration by hPDLSCs. Understanding of this process would potentially enable us to develop better cell-based treatment techniques.

Synergistic control of mesenchymal stem cell differentiation by nanoscale surface geometry and immobilized growth factors on TiO2 nanotubes

The aim of this study is to elucidate whether combined environmental signals provided by nanoscale topography and by growth factors control cell behavior of mesenchymal stem cells (MSCs) in a synergistic or simply additive manner. Chondrogenic and osteogenic differentiation of MSCs is studied on vertically aligned TiO(2) nanotubes of size 15 and 100 nm with and without immobilized bone morphogenetic protein-2 (BMP-2). Although BMP-2 coating stimulates both chondrogenic and osteogenic differentiation of MSCs, the response strongly depends on the surface nanoscale geometry of the BMP-2-coated nanotubes. Chondrogenic differentiation is strongly supported on 100 nm BMP-2-coated nanotubes, but not on 15 nm nanotubes, which induce spreading and de-differentiation of chondrocytes. A similar response is observed with primary chondrocytes, which maintain their chondrogenic phenotype on BMP-2-coated 100 nm nanotubes, but de-differentiate on 15 nm nanotubes. In contrast, osteogenic differentiation is greatly enhanced on 15 nm but not on 100 nm BMP-2-coated nanotubes as shown previously. Furthermore, covalent immobilization of BMP-2 rescues MSCs from apoptosis occurring on uncoated 100 nm TiO(2) nanotube surfaces. Thus, combined signals provided by BMP-2 immobilized to a defined lateral nanoscale spacing geometry seem to contain environmental cues that are able to modulate a lineage-specific decision of MSC differentiation and cell survival in a synergistic manner.

Pathogenesis of apical periodontitis: a literature review

OBJECTIVES

This review article discusses the host response in apical periodontitis with the main focus on cytokines, produced under this pathological condition and contributing to the degradation of periradicular tissues. The pace of research in this field has greatly accelerated in the last decade. Here we provide an analysis of studies published in this area during this period.

MATERIAL AND METHODS

Literature was selected through a search of PubMed electronic database. The keywords used for search were pathogenesis of apical periodontitis cytokines, periapical granuloma cytokines, inflammatory infiltrate apical periodontitis. The search was restricted to English language articles, published from 1999 to December 2010. Additionally, a manual search in the cytokine production, cytokine functions and periapical tissue destruction in the journals and books was performed.

RESULTS

In total, 97 literature sources were obtained and reviewed. The topics covered in this article include cellular composition of an inflammatory infiltrate in the periapical lesions, mechanisms of the formation of the innate and specific immune response. Studies which investigated cytokine secretion and functions were identified and cellular and molecular interactions in the course of apical periodontitis described.

CONCLUSIONS

The abundance and interactions of various inflammatory and anti-inflammatory molecules can influence and alter the state and progression of the disease. Therefore, periapical inflammatory response offers a model, suited for the study of many facets of pathogenesis, biocompatibility of different materials to periapical tissues and development of novel treatment methods, based on the regulation of cytokines expression.

A novel mixed-type stem cell pellet for cementum/periodontal ligament-like complex

BACKGROUND

Functional tissue regeneration underscores the construction of favorable extracellular matrix environment and neovascularization. In this study, we propose a mixed-type stem cell-pellet cultivation system for human periodontal ligament stem cells (hPDLSCs) to recreate a favorable regeneration microenvironment.

METHODS

The hPDLSCs were cocultured with human bone marrow mesenchymal stem cells (hBMMSCs) and mixed by osteoinduced ceramic bovine bone (CBB) powder as a mixed-type stem cell sheet. The influence of osteoinduced CBB on hPDLSCs was analyzed by alkaline phosphatase (ALP) and osteogenic differentiation assays. The effects of hBMMSCs on hPDLSCs were estimated by proliferating cell nuclear antigen, ALP, real-time reverse transcription polymerase chain reaction, and Western blot assays. The mixed-cell sheet was the preliminary observations in vitro that laid the foundation for additional implantation. After the cells were detached, the mixed-type sheet spontaneously contracted to produce a mixed-type stem cell pellet, which was transplanted into immunocompromised mice.

RESULTS

In vitro, the results showed that osteoinduced CBB could upregulate ALP activity and accelerate mineralization of hPDLSCs. When the hPDLSCs were cocultured with hBMMSCs, the ALP activity and proliferation kinetics were upregulated and also indicated in the expression of collagen I, osteocalcin, and vascular endothelial growth factor. It was found that, in vivo, the mixed-type hPDLSC pellets support cementum/periodontal ligament (PDL)-like tissue regeneration with neovascularization.

CONCLUSIONS

These results suggest that the mixed-type hPDLSC pellet could mimic the microenvironment of PDL and enhance the reconstruction of physiologic architecture of a dental cementum/PDL-like complex. This tissue mimicking may also be a promising alternative to promote periodontal defect repair for additional clinical applications.

Bone graft healing in reconstruction of maxillary atrophy

PURPOSE

Evaluate correlations between volume change for iliac crest bone grafts in maxillary reconstruction (graft volume change [GVC]) and bone mineral density (BMD), bone volume fraction (BVF), hematologic bone metabolic factors (I), and identify indicators of implant failure (II).

MATERIAL AND METHODS

Forty-six consecutive patients had their edentulous atrophic maxilla reconstructed with free autogenous bone grafts from anterior iliac crest. Endosteal implants were placed 6 months after graft healing. Computer tomography was performed after 3 weeks and 6 months after grafting. Bone biopsies were taken from the internal table of donor site for calculation (BVF), and blood samples were collected. Implant stability was measured at placement with resonance frequency analysis and expressed as implant stability quotient (ISQ). Implant failure was registered.

RESULTS

GVC in onlay bone graft was 37%. The BVF in iliac crest biopsies was 32%. Serum-IGFBP3 differed with 79% of the samples over normal range. Fifteen patients had one or more implant failures prior to loading (early failures). Forty-two patients were followed for a minimum of 3 years after implant loading and, in addition, 6/42 patients had one or more implants removed during the follow-up (late failures). GVC correlated to decreased BMD of lumbar vertebrae L2-L4 (Kruskal-Wallis test, p=.017). No correlation was found between GVC and hematologic factors (Pearson correlation test) or between GVC and BVF (Kruskal-Wallis test). No correlation was found between ISQ and GVC (Pearson correlation test, p=.865). The association between implant failures and the described factors were evaluated, and no significant correlations were found (unconditional logistic regression).

CONCLUSION

Onlay bone grafts decrease 37% during initial healing period, which correlate to BMD of lumbar vertebrae L2-L4. No other evaluated parameters could explain GVC. The evaluated factors could not explain implant failure.

Imbalanced dietary ascorbic acid alters molecular pathways involved in skeletogenesis of developing European sea bass (Dicentrarchus labrax)

The influence of dietary ascorbic acid (AA) on growth and morphogenesis during the larval development of European sea bass (Dicentrarchus labrax) was evaluated until 45days post hatching. Diets incorporated 0, 5, 15, 30, 50 or 400mg AA per kg diet to give AA-0, AA-5, AA-15, AA-30, AA-50 and AA-400 dietary treatments, respectively. Dietary AA levels lower than 15mg/kg reduced larval growth and survival was affected in specimens fed diets devoid of AA. Globally, disruption of the expression of genes involved in AA and calcium absorption in the intestine (SVCT-1, TRPV-6), skeletogenesis (BMP-4, IGF-1, RARγ) and bone mineralization (VDRβ, osteocalcin) were observed in groups fed doses lower and higher than 50mg AA/kg diet. Such disturbances detected at molecular level were associated with disruptions of the ossification process and the appearance of skeletal abnormalities.

A controversial role for IL-12 in immune response and bone resorption at apical periodontal sites

Periapical lesions are inflammatory conditions of tooth periapical tissues, triggered by dental pulp infection and characterized by exudation of immune cells to the affected tissues and production of inflammatory mediators such as cytokines. The inflammatory periapical reaction is mainly driven by Th1, Th2, and Th17 responses, and such polarization may modulate progression of the disease and expression of bone proresorptive cytokines. IL-12 is a potent inducer of IFN-γ production, which stimulates Th1 effector cells. Many evidences have shown a positive correlation between the bone resorptive cytokine IL-1β and the production of IL-12 and IFN-γ. Furthermore, IL-12 may have a potential role in the release of bone resorptive mediators and blockade of Th2 cytokines, affecting the progression of periapical bone loss. Nevertheless, IL-12 and IFN-γ have also been described as suppressors of osteoclast differentiation and activation, favoring bone maintenance. This paper focuses on the controversial roles of IL-12 in periapical lesions.

Relationship between periodontal disease and osteoporosis

BACKGROUND

For many years an association between the low bone density of osteoporosis and increased risk of periodontal bone loss has been suspected. In this review the relationship between osteoporosis and periodontal disease is considered.

METHODS

For this narrative review a very broad search strategy of the literature was developed using both PubMed and Scopus databases using the search words "perio" and "osteoporosis". The reference lists from the selected papers were also scanned and this provided an additional source of papers for inclusion. The inclusion/exclusion criteria, were also quite liberal with only those papers dealing with bisphosphonates and osteonecrosis of the jaws, osteoporosis in edentulous individuals, as well as those not written in English being excluded.

RESULTS

The data available suggest that reduced bone mineral density is a shared risk factor for periodontitis rather than a causal factor. However, more prospective studies are required to fully determine what, if any, relationship truly exists between periodontitis and reduced bone mineral density.

CONCLUSIONS

More prospective studies are required to determine what, if any, relationships exist between periodontal disease and reduced bone mineral density.

Dietary fatty acids and inflammation in the vertebral column of Atlantic salmon, Salmo salar L., smolts: a possible link to spinal deformities

Vegetable oils (Vo) are an alternative to fish oil (Fo) in aquaculture feeds. This study aimed to evaluate the effect of dietary soybean oil (Vo diet), rich in linoleic acid, and of dietary fish oil (Fo diet) on the development of spinal deformities under bacterial lipopolysaccharide (LPS)-induced chronic inflammation conditions in Atlantic salmon, Salmo salar L. Fish [25 g body weight (BW)] were fed the experimental diets for 99 days. On day 47 of feeding (40 g BW), fish were subjected to four experimental regimes: (i) intramuscular injections with LPS, (ii) sham-injected phosphate-buffered saline (PBS), (iii) intraperitoneally injected commercial oil adjuvant vaccine, or (iv) no treatment. The fish continued under a common feeding regime in sea water for 165 more days. Body weight was temporarily higher in the Vo group than in the Fo group prior to immunization and was also affected by the type of immunization. At the end of the trial, no differences were seen between the dietary groups. The overall prevalence of spinal deformities was approximately 14% at the end of the experiment. The Vo diet affected vertebral shape but did not induce spinal deformities. In groups injected with LPS and PBS, spinal deformities ranged between 21% and 38%, diet independent. Deformed vertebrae were located at or in proximity to the injection point. Assessment of inflammatory markers revealed high levels of plasma prostaglandin E₂ (PGE₂) in the Vo-fed and LPS-injected groups, suggesting an inflammatory response to LPS. Cyclooxigenase 2 (COX-2) mRNA expression in bone was higher in fish fed Fo compared to Vo-fed fish. Gene expression of immunoglobulin M (IgM) was up-regulated in bone of all LPS-injected groups irrespective of dietary oil. In conclusion, the study suggests that Vo is not a risk factor for the development of inflammation-related spinal deformities. At the same time, we found evidence that localized injection-related processes could trigger the development of vertebral body malformations.

Periodontal regeneration: a challenge for the tissue engineer?

Periodontitis affects around 15 per cent of human adult populations. While periodontal treatment aimed at removing the bacterial cause of the disease is generally very successful, the ability predictably to regenerate the damaged tissues remains a major unmet objective for new treatment strategies. Existing treatments include the use of space-maintaining barrier membranes (guided tissue regeneration), use of graft materials, and application of bioactive molecules to induce regeneration, but their overall effects are relatively modest and restricted in application. The periodontal ligament is rich in mesenchymal stem cells, and the understanding of the signalling molecules that may regulate their differentation has increased enormously in recent years. Applying these principles for the development of new tissue engineering strategies for periodontal regeneration will require further work to determine the efficacy of current experimental preclinical treatments, including pharmacological application of growth factors such as bone morphogenetic proteins (BMPs) or Wnts, use of autologous stem cell reimplantation strategies, and development of improved biomaterial scaffolds. This article describes the background to this problem, addresses the current status of periodontal regeneration, including the background biology, and discusses the potential for some of these experimental therapies to achieve the goal of clinically predictable periodontal regeneration.

Stimulation of osteoblastic differentiation and mineralization in MC3T3-E1 cells by yeast hydrolysate

In a previous study, it was reported that yeast hydrolysate (YH) was effective in promoting bone growth in Sprague-Dawley (SD) rats. To further clarify the mechanism of YH, the effects of YH on proliferation, differentiation and gene expression in vitro were investigated using osteoblastic cell lines (MC3T3-E1). Cell proliferation increased significantly as much as 110% of the basal value when cells were treated with 100 µg/mL of YH. Alkaline phosphatase (ALP) activity increased significantly with a YH concentration of 25-100 µg/mL, and the activity increased 152% that of the control at 100 µg/mL. The calcium content increased as much as 129% at 100 µg/mL YH. The gene expression levels of ALP and collagen type II (COL II) significantly increased approximately 1.3-fold and 1.7-fold of control, respectively, at 100 µg/mL. YH increased significantly the mRNA level of bone sialoprotein (BSP) but not in a dose-dependent manner. The mRNA levels of bone morphogenetic proteins (BMP)-2, BMP-4, collagen type I (COL I) and osteonectin (ON) did not increase. In summary, YH increased the proliferation of osteoblasts and directly stimulated ALP and bone matrix proteins (e.g. BSP, COL II), and these increases trigger osteoblastic differentiation (e.g. mineralized nodule formation).

Regulation of human adipose-derived stromal cell osteogenic differentiation by insulin-like growth factor-1 and platelet-derived growth factor-alpha

BACKGROUND

Human adipose-derived stromal cells possess a great potential for tissue engineering purposes. The authors' laboratory is interested in harnessing human adipose-derived stromal cells for skeletal tissue regeneration and identifying those factors that enhance human adipose-derived stromal cell osteogenic differentiation. The authors hypothesized that insulin-like growth factor (IGF) and platelet-derived growth factor (PDGF) would stimulate human adipose-derived stromal cell osteogenesis and that IGF would stimulate adipogenesis.

METHODS

Adipose-derived stromal cells were harvested from human lipoaspirate. Previously, a microarray analysis examined gene expression throughout osteogenic differentiation. In a candidate fashion, the authors added recombinant IGF-1 and PDGF-alpha individually and in combination. Osteogenesis and adipogenesis were assessed by alkaline phosphatase, alizarin red, and oil red O staining, and quantitative real-time polymerase chain reaction (RUNX2, ALP, OCN, IGF1, PPARG, LPL, AP2, and GCP1). Finally, intersection between IGF and PDGF signaling pathways was evaluated.

RESULTS

IGF-1 was observed to increase osteogenic differentiation by all markers (p < 0.01). However, PDGF-alpha when added alone primarily did not affect osteogenic markers. PDGF-alpha positively regulated transcription of IGF1. Addition of PDGF-alpha in combination with or before IGF-1 enhanced osteogenesis more than either alone. IGF-1 increased whereas PDGF-alpha diminished human adipose-derived stromal cell adipogenesis.

CONCLUSIONS

IGF signaling significantly increased osteogenesis in human adipose-derived stromal cells and may be used for tissue-engineering purposes. The combination of PDGF and IGF may be more beneficial than either alone in driving adipose-derived stromal cell osteogenesis. Future in vivo applications will focus on the combination of adipose-derived stromal cells, biomimetic scaffolds, and recombinant IGF.

Effects of enamel matrix derivative on bioactive glass in rat calvarium defects

Tissue engineering-based bone grafting has emerged as a viable alternative to biologic and synthetic grafts. The purpose of this study was to evaluate the effect of enamel matrix derivative (EMD; Emdogain gel, Biora AB, Malmö, Sweden) on bioactive glass in enhancing bone formation in rat calvarium defects. Twenty rats were used in the study. In all animals, 2 standardized critical-sized calvarial defects (5.0 mm diameter) were created surgically. The animals were randomly allocated into 4 groups of 5 animals each. Group AI: one calvarial defect was filled with bioactive glass plus EMD, while the contralateral defect was filled with bioactive glass alone. The healing period was 2 weeks. Groups AII and AIII: the animals were treated in the same manner as in group AI, but the healing periods were 4 and 8 weeks, respectively. Group B: one calvarial defect was filled with EMD only, while the contralateral defect was empty (CSD). The healing period was 8 weeks. New bone formation was evaluated by radiomorphometry and histomorphometry. Results of radiomorphometry showed no significant difference in the mean optical density between bioactive glass with EMD and bioactive glass alone; no defect completely regenerated with bone. The histologic analysis revealed that defects filled with bioactive glass plus EMD in all groups contained slightly more percentage of new bone than those filled with bioactive glass alone; however, the difference was not statistically significant. The highest percentage of new bone formation was present at 8 weeks in the bioactive glass plus EMD group. Bioactive glass particles, used with or without EMD, maintained the volume and contour of the area grafted in CSD. However, they did not lead to a significant difference in bone formation when compared with CSD 8 weeks postoperatively.

Non-resorbing osteoclasts induce migration and osteogenic differentiation of mesenchymal stem cells

Osteoclast activity has traditionally been regarded as restricted to bone resorption but there is some evidence that also non-resorbing osteoclasts might influence osteoblast activity. The aim of the present study was to further investigate the hypothesis of an anabolic function of non-resorbing osteoclasts by investigating their capability to recruit mesenchymal stem cells (MSC) and to provoke their differentiation toward the osteogenic lineage. Bone-marrow-derived human MSC were exposed to conditioned media (CM) derived from non-resorbing osteoclast cultures, which were generated from human peripheral blood monocytes. Osteogenic marker genes (transcription factor Runx2, bone sialoprotein, alkaline phosphatase (AP), and osteopontin) were significantly increased. Osteogenic differentiation (OD) was also proved by von Kossa and AP staining occurred in the same range as in MSC cultures stimulated with osteogenic supplements. Chemotactic responses of MSC were measured with a modified Boyden chamber assay. CM from osteoclast cultures induced a strong migratory response in MSC, which was greatly reduced in the presence of an anti-human platelet-derived growth factor (PDGF) receptor beta antibody. Correspondingly, significantly increased PDGF-BB concentrations were measured in the CM using a PDGF-BB immunoassay. CM derived from mononuclear cell cultures did not provoke MSC differentiation and had a significantly lower migratory effect on MSC suggesting that the effects were specifically mediated by osteoclasts. In conclusion, it can be suggested that human non-resorbing osteoclasts induce migration and OD of MSC. While effects on MSC migration might be mainly due to PDGF-BB, the factors inducing OD remain to be elucidated.

A review on endogenous regenerative technology in periodontal regenerative medicine

Periodontitis is a globally prevalent inflammatory disease that causes the destruction of the tooth-supporting apparatus and potentially leads to tooth loss. Currently, the methods to reconstitute lost periodontal structures (i.e. alveolar bone, periodontal ligament, and root cementum) have relied on conventional mechanical, anti-infective modalities followed by a range of regenerative procedures such as guided tissue regeneration, the use of bone replacement grafts and exogenous growth factors (GFs), and recently developed tissue engineering technologies. However, all current or emerging paradigms have either been shown to have limited and variable outcomes or have yet to be developed for clinical use. To accelerate clinical translation, there is an ongoing need to develop therapeutics based on endogenous regenerative technology (ERT), which can stimulate latent self-repair mechanisms in patients and harness the host's innate capacity for regeneration. ERT in periodontics applies the patient's own regenerative 'tools', i.e. patient-derived GFs and fibrin scaffolds, sometimes in association with commercialized products (e.g. Emdogain and Bio-Oss), to create a material niche in an injured site where the progenitor/stem cells from neighboring tissues can be recruited for in situ periodontal regeneration. The choice of materials and the design of implantable devices influence therapeutic potential and the number and invasiveness of the associated clinical procedures. The interplay and optimization of each niche component involved in ERT are particularly important to comprehend how to make the desired cell response safe and effective for therapeutics. In this review, the emerging opportunities and challenges of ERT that avoid the ex vivo culture of autologous cells are addressed in the context of new approaches for engineering or regeneration of functional periodontal tissues by exploiting the use of platelet-rich products and its associated formulations as key endogenous resources for future clinical management of periodontal tissue defects.

The role of NELL-1, a growth factor associated with craniosynostosis, in promoting bone regeneration

Efforts to enhance bone regeneration in orthopedic and dental cases have grown steadily for the past decade, in line with increasingly sophisticated regenerative medicine. To meet the unprecedented demand for novel osteospecific growth factors with fewer adverse effects compared with those of existing adjuncts such as BMPs, our group has identified a craniosynostosis-associated secreted molecule, NELL-1, which is a potent growth factor that is highly specific to the osteochondral lineage, and has demonstrated robust induction of bone in multiple in vivo models from rodents to pre-clinical large animals. NELL-1 is preferentially expressed in osteoblasts under direct transcriptional control of Runx2, and is well-regulated during skeletal development. NELL-1/Nell-1 can promote orthotopic bone regeneration via either intramembranous or endochondral ossification, both within and outside of the craniofacial complex. Unlike BMP-2, Nell-1 cannot initiate ectopic bone formation in muscle, but can induce bone marrow stromal cells (BMSCs) to form bone in a mouse muscle pouch model, exhibiting specificity that BMPs lack. In addition, synergistic osteogenic effects of Nell-1 and BMP combotherapy have been observed, and are likely due to distinct differences in their signaling pathways. NELL-1's unique role as a novel osteoinductive growth factor makes it an attractive alternative with promise for future clinical applications. [Note: NELL-1 and NELL-1 indicate the human gene and protein, respectively; Nell-1 and Nell-1 indicate the mouse gene and protein, respectively.]

Cigarette smoke inhalation modulates gene expression in sites of bone healing: a study in rats

OBJECTIVE

The aim of this study was to assess the effect of cigarette smoke inhalation (CSI) on gene expression in alveolar bone healing sites.

STUDY DESIGN

Wistar rats were randomly assigned to the groups: control [animals not exposed to CSI (n = 20)] and test [animals exposed to CSI, starting 3 days before teeth extraction and maintained until killing them (n = 20)]. First mandibular molars were bilaterally extracted, and the expression of alkaline phosphatase, bone morphogenetic protein (BMP) 2 and 7, receptor activator of nuclear factor κB ligand, osteoprotegerin, and d2 isoform of vacuolar adenosine triphosphatase V(0) domain were assessed by quantitative polymerase chain reaction in the newly formed tissue in the sockets.

RESULTS

Overall, data analysis demonstrated that CSI significantly affected the expression pattern of all of the studied genes except BMP-7.

CONCLUSION

The expression of key genes for bone healing may be affected by CSI in tooth extraction sites.

Periodontal tissue engineering and regeneration: current approaches and expanding opportunities

The management of periodontal tissue defects that result from periodontitis represents a medical and socioeconomic challenge. Concerted efforts have been and still are being made to accelerate and augment periodontal tissue and bone regeneration, including a range of regenerative surgical procedures, the development of a variety of grafting materials, and the use of recombinant growth factors. More recently, tissue-engineering strategies, including new cell- and/or matrix-based dimensions, are also being developed, analyzed, and employed for periodontal regenerative therapies. Tissue engineering in periodontology applies the principles of engineering and life sciences toward the development of biological techniques that can restore lost alveolar bone, periodontal ligament, and root cementum. It is based on an understanding of the role of periodontal formation and aims to grow new functional tissues rather than to build new replacements of periodontium. Although tissue engineering has merged to create more opportunities for predictable and optimal periodontal tissue regeneration, the technique and design for preclinical and clinical studies remain in their early stages. To date, the reconstruction of small- to moderate-sized periodontal bone defects using engineered cell-scaffold constructs is technically feasible, and some of the currently developed concepts may represent alternatives for certain ideal clinical scenarios. However, the predictable reconstruction of the normal structure and functionality of a tooth-supporting apparatus remains challenging. This review summarizes current regenerative procedures for periodontal healing and regeneration and explores their progress and difficulties in clinical practice, with particular emphasis placed upon current challenges and future possibilities associated with tissue-engineering strategies in periodontal regenerative medicine.

Betulinic acid stimulates the differentiation and mineralization of osteoblastic MC3T3-E1 cells: involvement of BMP/Runx2 and beta-catenin signals

In the field of osteoporosis, there has been growing interest in anabolic agents that enhance bone formation. Here, we examined the effects of betulinic acid on cell proliferation, differentiation, and mineralization of MC3T3-E1 osteoblasts. Then, the impact of betulinic acid on signaling pathways known to be implicated in osteoblastogenesis was explored. Betulinic acid (1-20 microM) markedly increased alkaline phosphatase (ALP) activity and calcium nodule formation, although without a notable effect on cell proliferation. Stimulation with betulinic acid not only increased the osteopontin level and osteocalcin mRNA expression but also upregulated the osteoprotegerin (OPG)/RANKL ratio. Noggin, but not ICI 182780, significantly repressed betulinic acid-induced ALP activity, suggesting a possible action of betulinic acid through the bone morphogenetic protein (BMP) pathway. This was strengthened by the induction of BMP-2 expression, increases in Smad1/5/8 phosphorylation, and Runx2 expression. Furthermore, betulinic acid increased the nuclear level of the active form beta-catenin. These results suggested that betulinic acid has the potential to enhance osteoblastogenesis probably through the activation of BMP/Smad/Runx2 and beta-catenin signal pathways. Furthermore, upregulation of the OPG/RANKL ratio to repress bone catabolism may also indirectly contribute to the bone anabolic effect of betulinic acid.

Osteogenesis in an in vitro coculture of human periodontal ligament fibroblasts and human microvascular endothelial cells

BACKGROUND

Periodontal bone healing is a complex process involving many cells and processes that must function flawlessly for proper healing to occur. The exact progenitor cells that contribute to this process are not fully characterized. Periodontal fibroblasts and pericytes were postulated to be potential osteoprogenitor cells. This study describes a viable coculture model for the in vitro study of osteogenesis.

METHODS

Human microvascular endothelial cells (HMVEC) and human periodontal ligament (HPDL) fibroblasts were cocultured in a layered model and monitored for the development of runt-related transcription factor 2 (runx2) and desmin expression by real-time polymerase chain reaction. Conditions shown to be osteogenic (bone morphogenetic protein [BMP]-2 and enamel matrix derivative [EMD]) were compared to a control coculture that was unstimulated.

RESULTS

The HMVEC migrated into a layer of collagen containing only HPDL cells as monitored by fluorescent labeling. runx2 and desmin expressions were increased in stimulated cocultures in week 2 compared to controls. At week 3, the unstimulated control cocultures developed the expression of runx2 and desmin, and the cocultures that were stimulated with EMD and BMP-2 achieved significantly higher levels of these factors than any of the other conditions.

CONCLUSIONS

Signs of osteogenesis were present in the cocultures in unstimulated and stimulated conditions. However, in the stimulated condition, osteogenic markers were increased at earlier time points. As such, this model may provide a good method for the study of specific cellular processes that may lead to osteogenesis and eventually for understanding the regeneration of periodontal bone in vivo.

Interleukin-6 polymorphisms modify the risk of periodontitis: a systematic review and meta-analysis

OBJECTIVE

To clarify the association of IL-6 polymorphisms and periodontitis, a meta-analysis of case-control studies and a systemic review were conducted.

MATERIAL AND METHODS

We performed a literature search using PubMed and Medline database to May 2009, with no restrictions. We also reviewed references from all retrieved articles. Six case-control studies involving 1 093 periodontitis cases and 574 controls were selected for meta-analysis to assess the purported associations between IL-6 polymorphisms and the risk of periodontitis. IL-6 -174 G/C and -572 C/G polymorphisms were included in the present meta-analysis, and the association between IL-6 -6331 T/C polymorphism and the risk of periodontitis was adequately reviewed as well.

RESULTS AND CONCLUSION

The present meta-analysis indicates that the IL-6 -174 G allele could not modify the risk of chronic periodontitis, but increased the risk of aggressive periodontitis. And -572 C/G polymorphism is associated with the pathogenesis of periodontitis, including chronic periodontitis or aggressive periodontitis.

Differentiation dependent expression of urocortin's mRNA and peptide in human osteoprogenitor cells: influence of BMP-2, TGF-beta-1 and dexamethasone

Urocortin-1 (UCN) a corticotropin releasing-factor (CRF) related peptide, has been found to be expressed in many different tissues like the central nervous system, the cardiovascular system, adipose tissue, and skeletal muscle. The effects of UCN are mediated via stimulation of CRF-receptors 1 and 2 (CRFR1 and 2, CRFR’s) with a high affinity for CRFR2. It has been shown that the CRF-related peptides and CRFR’s are involved in the regulation of stress-related endocrine, autonomic and behavioural responses. Using immunocytochemistry, immunohistochemistry and RT–PCR, we now can show the differentiation dependent expression of UCN mRNA and peptide in human mesenchymal progenitor cells (MSCs) directed to the osteoblastic phenotype for the first time. UCN expression was down regulated by TGF-beta and BMP-2 in the early proliferation phase of osteoblast development, whereas dexamethasone (dex) minimally induced UCN gene expression during matrix maturation after 24 h stimulation. Stimulation of MSCs for 28 days with ascorbate/beta-glycerophosphate (asc/bGp) induced UCN gene expression at day 14. This effect was prevented when using 1,25-vitamin D3 or dex in addition. There was no obvious correlation to osteocalcin (OCN) gene expression in these experiments. In MSCs from patients with metabolic bone disease (n = 9) UCN gene expression was significantly higher compared to MSCs from normal controls (n = 6). Human MSCs did not express any of the CRFR’s during differentiation to osteoblasts. Our results indicate that UCN is produced during the development of MSCs to osteoblasts and differentially regulated during culture as well as by differentiation factors. The expression is maximal between proliferation and matrix maturation phase. However, UCN does not seem to act on the osteoblast itself as shown by the missing CRFR’s. Our results suggest new perspectives on the role of urocortin in human skeletal tissue in health and disease.

Nonviral delivery of basic fibroblast growth factor gene to bone marrow stromal cells

Basic fibroblast growth factor (bFGF) is capable of stimulating osteogenic differentiation of preosteoblast cells in vitro and new bone tissue deposition in vivo. Delivering the gene for the protein, rather than the protein itself, is considered advantageous for bone repair since gene delivery obviates the need to produce the protein in pharmaceutical quantities. To explore the feasibility of bFGF gene delivery by nonviral methods, we transfected primary rat bone marrow stromal cells (BMSC) using cationic polymers (polyethylenimine and poly(L-lysine)-palmitic acid) in vitro. After delivering a bFGF-expression plasmid (pFGF2-IRES-AcGFP) to BMSC, the presence of bFGF in culture supernatants was detected by a commercial ELISA. As much as 0.3 ng bFGF/10(6) cells/day was obtained from the BMSC under optimal conditions. This secretion rate was approximately 100-fold lower than the secretion obtained from immortal, and easy-to-transfect, human 293T cells. These data suggest the feasibility of modifying BMSC with nonviral delivery systems for bFGF expression, but also highlight the need for substantial improvement in transfection rate for an effective therapy.

Prosthetic considerations for orthodontic implant site development in the adult patient

Proper site development is a key factor for long-term clinical success of dental implants. Whereas surgical and restorative techniques have been refined to ensure predictable functional and esthetic outcome, individual clinical prerequisites do not always allow proper placement of implants when prosthetic and material properties are considered. Orthodontic tooth movement may be a viable and nonsurgical site development treatment option. With the introduction and advancements of minimal invasive and less visible orthodontic appliances, a growing number of adult patients are willing to obtain orthodontic treatment. The spectrum of modern appliances is broad and ranges from clear aligners to lingual brackets. Skeletal anchorage devices such as orthodontic mini-implants often eliminate unpopular external anchorage devices (ie, headgear) in adult patients, This article discusses the selection of an appropriate pretreatment approach by taking patient-specific criteria into account.