Effects of growth factors and cytokines on osteoblast differentiation

Synthesis of novel 5,6-dehydrokawain analogs as osteogenic inducers and their action mechanisms

An imbalance between bone resorption by osteoclasts and bone formation by osteoblasts can cause bone loss and bone-related disease. In a previous search for natural products that increase osteogenic activity, we found that 5,6-dehydrokawain (1) from Alpinia zerumbet promotes osteoblastogenesis. In this study, we synthesized and evaluated series of 5,6-dehydrokawain analogs. Our structure-activity relationships revealed that alkylation of para or meta position of aromatic ring of 1 promote osteogenic activity. Among the potential analogs we synthesized, (E)-6-(4-Ethylstyryl)-4-methoxy-2H-pyran-2-one (14) and (E)-6-(4-Butylstyryl)-4-methoxy-2H-pyran-2-one (21) both significantly up-regulated Runx2 and Osterix mRNA expression at 10µM. These osteogenic activities could be mediated by bone morphogenetic protein (BMP) and activation of p38 MAPK signaling pathways. Compounds 14 and 21 also inhibited RANKL-induced osteoclast differentiation of RAW264 cells. These results indicated that novel 5,6-dehydrokawain analogs not only increase osteogenic activity but also inhibit osteoclast differentiation, and could be potential lead compounds for the development of anti-osteoporosis agents.

Inflammatory mediator polymorphisms associate with initial periodontitis in adolescents

Several studies have addressed cytokine gene polymorphisms and their possible associations with periodontitis. We examined the association between salivary anti- and pro-inflammatory mediator polymorphisms and initial periodontitis in Finnish adolescents, taking into account the effect of smoking. Salivary samples of 93 clinically examined adolescents from Eastern Finland were analyzed. Their oral health and smoking habits were recorded. Periodontal probing depth (PPD), and bleeding on probing (BOP) at four sites per tooth, root calculus (RC), and visible plaque index (VPI) were recorded from the index teeth. Salivary MMP-8 median values were assessed. The sites with ≥4 mm PD were categorized as follows: PPD1 = one or more ≥4 mm pocket, PPD2 = two or more ≥4 mm pockets, and PPD3 = three or more ≥4 mm pockets. Genomic DNA was extracted from 300 μl of the saliva samples by genomic QIAamp® DNA Blood Mini Kit and genotyped for polymorphisms. Genetic variants for genotyping were selected from the following genes of interest: S100A8, FCGR2A, FCGR2B, IL10, MMP8, MMP3, MMP13, VDR, TLR4, MMP2, MPO, ELANE, IL1A, IL1B, IL1RN, CD28, MMP9, DDX39B, NFKBIL1, LTA, TNF, SOD2, IL6, TLR4, TIMP1, and SYN1. After false discovery rate control (FDR), polymorphisms in MMP3 (rs679620, rs520540, rs639752), CD28 (rs3116496), and VDR (rs2228570) associated (FDR q < 0.05) with deepened periodontal pockets. Smoking did not affect the results. Genetic polymorphisms of pro-inflammatory mediators MMP3, CD28, and VDR seem to link to initial periodontitis.

Tissue Engineering for Vertical Ridge Reconstruction

This article provides an overview of basic tissue engineering principles as they are applied to vertical ridge defects and reconstructive techniques for these types of deficiencies. Presented are multiple clinical cases ranging from office-based dentoalveolar procedures to the more complex reconstruction of postresection mandibular defects. Several different types of regenerative tissue constructs are presented; either used alone or in combination with traditional reconstructive techniques and procedures, such as maxillary sinus augmentation, Le Fort I osteotomy, and microvascular free tissue transfer. The goal is to also familiarize the reconstructive surgeon to potential future strategies in vertical alveolar ridge augmentation.

Composite cell sheet for periodontal regeneration: crosstalk between different types of MSCs in cell sheet facilitates complex periodontal-like tissue regeneration

Background

Tissue-engineering strategies based on mesenchymal stem cells (MSCs) and cell sheets have been widely used for periodontal tissue regeneration. However, given the complexity in periodontal structure, the regeneration methods using a single species of MSC could not fulfill the requirement for periodontal regeneration.

Methods

We researched the interaction between the periodontal ligament stem cells (PDLSCs) and jaw bone marrow-derived mesenchymal stem cells (JBMMSCs), and constructed a composite cell sheet comprising both of the above MSCs to regenerate complex periodontium-like structures in nude mice.

Results

Our results show that by co-culturing PDLSCs and JBMMSCs, the expressions of bone and extracellular matrix (ECM)-related genes and proteins were significantly improved in both MSCs. Further investigations showed that, compared to the cell sheet using PDLSCs or JBMMSCs, the composite stem cell sheet (CSCS), which comprises these two MSCs, expressed higher levels of bone- and ECM-related genes and proteins, and generated a composite structure more similar to the native periodontal tissue physiologically in vivo.

Conclusions

In conclusion, our results demonstrate that the crosstalk between PDLSCs and JBMMSCs in cell sheets facilitate regeneration of complex periodontium-like structures, providing a promising new strategy for physiological and functional regeneration of periodontal tissue.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0417-x) contains supplementary material, which is available to authorized users.

Caffeic acid phenethyl ester attenuates lipopolysaccharide-stimulated proinflammatory responses in human gingival fibroblasts via NF-κB and PI3K/Akt signaling pathway

Periodontal diseases often begin with chronic gingival inflammation, which causes the destruction of periodontal tissues. Inflammatory immune responses from host cells to bacteria, such as Porphyromonas gingivalis (P. gingivalis), cause periodontal degradation. Human gingival fibroblasts (HGFs) are the major cells in periodontal soft tissues. When stimulated by lipopolysaccharide (LPS), HGFs could secrete several pro-inflammatory cytokines and chemokines, such as interleukins (ILs) IL-6, IL-8, inducible nitric oxide synthase (iNOS), and cyclooxygenase 2 (COX-2). Caffeic acid phenethyl ester (CAPE) is the main active component of propolis, which is collected by honeybees from different plants and known for its anti-inflammatory effects. The anti-inflammatory effects of CAPE on the LPS-induced HGFs were demonstrated in this study. HGFs were pretreated with CAPE (10, 20, and 30µm) for 1h, followed by LPS stimulation (1μg/ml) for 24h. Enzyme-linked immunosorbent assay, Western blot analysis, and immunofluorescence staining were used to evaluate the production of IL-6, IL-8, iNOS, and COX-2, as well as the activation of TLR4-mediated NF-κB, PI3K/AKT, and MAPK signaling pathways. The results indicated that CAPE inhibits LPS-induced IL-6, IL-8, iNOS, and COX-2 production in a dose-dependent manner. Moreover, CAPE suppresses LPS-induced TLR4/MyD88 and nuclear factor kappa B (NF-κB) activation. In addition, phosphatidylinositol 3 kinase (PI3K) and protein kinase B (AKT) phosphorylation was inhibited by CAPE. These results demonstrated that CAPE could be effective for treating of periodontal diseases.

Effects of TGF-β1 on mineralization mediated by rat calvaria-derived osteogenic cells

In this study, we have analyzed the viability and cell growth, as well as, the mineralization of extracellular matrix (ECM) by alizarin red and von Kossa staining of calvaria-derived osteogenic cultures, treated with TGF-β1 alone or associated with Dex comparing with acid ascorbic (AA) + β-glicerophosphate (βGP) (positive mineralization control). The expression of the noncollagenous proteins bone sialoprotein (BSP), osteopontin (OPN) and fibronectin (FN) were evaluated by indirect immunofluorescence. In addition, the main ultrastructural morphological findings were assessed by transmission electron microscopy. Osteogenic cells were isolated of calvaria bone from newborn (2-day-old) Wistar rats were treated with TGF-β1 alone or with dexamethasone for 7, 10, and 14 days. As positive mineralization control, the cells were supplemented only with AA+ βGP. As negative control, the cells were cultured with basal medium (α-MEM + 10%FBS + 1%gentamicin). The treatment with TGF-β1, even when combined with Dex, decreased the viability and cell growth when compared with the positive control. Osteoblastic cell cultures were positive to alizarin red and von Kossa stainings after AA + βGP and Dex alone treatments. Positive immunoreaction was found for BSP, OPN and FN in all studied treatments. Otherwise, when the cell cultures were supplemented with TGF-β1 and TGF-β1 + Dex, no mineralization was observed in any of the studied periods. These present findings suggest that TGF-β1, in the studied in vitro doses, inhibits the proliferation and differentiation of osteoblastic cells by impairment of nodule formation.

Recent advancements in regenerative dentistry: A review

Although human mouth benefits from remarkable mechanical properties, it is very susceptible to traumatic damages, exposure to microbial attacks, and congenital maladies. Since the human dentition plays a crucial role in mastication, phonation and esthetics, finding promising and more efficient strategies to reestablish its functionality in the event of disruption has been important. Dating back to antiquity, conventional dentistry has been offering evacuation, restoration, and replacement of the diseased dental tissue. However, due to the limited ability and short lifespan of traditional restorative solutions, scientists have taken advantage of current advancements in medicine to create better solutions for the oral health field and have coined it "regenerative dentistry." This new field takes advantage of the recent innovations in stem cell research, cellular and molecular biology, tissue engineering, and materials science etc. In this review, the recently known resources and approaches used for regeneration of dental and oral tissues were evaluated using the databases of Scopus and Web of Science. Scientists have used a wide range of biomaterials and scaffolds (artificial and natural), genes (with viral and non-viral vectors), stem cells (isolated from deciduous teeth, dental pulp, periodontal ligament, adipose tissue, salivary glands, and dental follicle) and growth factors (used for stimulating cell differentiation) in order to apply tissue engineering approaches to dentistry. Although they have been successful in preclinical and clinical partial regeneration of dental tissues, whole-tooth engineering still seems to be far-fetched, unless certain shortcomings are addressed.

VEGF-C and TGF-β reciprocally regulate mesenchymal stem cell commitment to differentiation into lymphatic endothelial or osteoblastic phenotypes

The direction of mesenchymal stem cell (MSC) differentiation is regulated by stimulation with various growth factors and cytokines. We recently established MSC lines, [transforming growth factor-β (TGF-β)-responsive SG‑2 cells, bone morphogenetic protein (BMP)-responsive SG‑3 cells, and TGF-β/BMP-non-responsive SG‑5 cells], derived from the bone marrow of green fluorescent protein-transgenic mice. In this study, to compare gene expression profiles in these MSC lines, we used DNA microarray analysis to characterize the specific gene expression profiles observed in the TGF-β-responsive SG‑2 cells. Among the genes that were highly expressed in the SG‑2 cells, we focused on vascular endothelial growth factor (VEGF) receptor 3 (VEGFR3), the gene product of FMS-like tyrosine kinase 4 (Flt4). We found that VEGF-C, a specific ligand of VEGFR3, significantly induced the cell proliferative activity, migratory ability (as shown by Transwell migration assay), as well as the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in the SG‑2 cells. Additionally, VEGF-C significantly increased the expression of prospero homeobox 1 (Prox1) and lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), which are lymphatic endothelial cell markers, and decreased the expression of osteogenic differentiation marker genes in these cells. By contrast, TGF-β significantly increased the expression of early-phase osteogenic differentiation marker genes in the SG‑2 cells and markedly decreased the expression of lymphatic endothelial cell markers. The findings of our study strongly suggest the following: i) that VEGF-C promotes the proliferative activity and migratory ability of MSCs; and ii) VEGF-C and TGF-β reciprocally regulate MSC commitment to differentiation into lymphatic endothelial or osteoblastic phenotypes, respectively. Our findings provide new insight into the molecular mechanisms underlying the regenerative ability of MSCs.

Rescuing failed oral implants via Wnt activation

AIM

Implant osseointegration is not always guaranteed and once fibrous encapsulation occurs clinicians have few options other than implant removal. Our goal was to test whether a WNT protein therapeutic could rescue such failed implants.

MATERIAL AND METHODS

Titanium implants were placed in over-sized murine oral osteotomies. A lack of primary stability was verified by mechanical testing. Interfacial strains were estimated by finite element modelling and histology coupled with histomorphometry confirmed the lack of peri-implant bone. After fibrous encapsulation was established peri-implant injections of a liposomal formulation of WNT3A protein (L-WNT3A) or liposomal PBS (L-PBS) were then initiated. Quantitative assays were employed to analyse the effects of L-WNT3A treatment.

RESULTS

Implants in gap-type interfaces exhibited high interfacial strains and no primary stability. After verification of implant failure, L-WNT3A or L-PBS injections were initiated. L-WNT3A induced a rapid, significant increase in Wnt responsiveness in the peri-implant environment, cell proliferation and osteogenic protein expression. The amount of peri-implant bone and bone in contact with the implant were significantly higher in L-WNT3A cases.

CONCLUSIONS

These data demonstrate L-WNT3A can induce peri-implant bone formation even in cases where fibrous encapsulation predominates.

Nanoparticles combined with growth factors: recent progress and applications

Increasing attention has been focused on the applications of nanoparticles combined with growth factors (NPs/GFs) due to the substantial functions of GFs in regenerative medicine and disease treatments.

Adult Human Mesenchymal Stem Cell Differentiation at the Cell Population and Single-Cell Levels Under Alternating Electric Current

Mesenchymal stem cells, precursors that can differentiate into osteoblasts, chondrocytes, and adipocytes, have tremendous potential for derivation of cells with specific (e.g., osteogenic) phenotypes for tissue engineering and tissue regeneration applications. To date, the predominant strategy to achieve directed differentiation of MSCs into osteoblasts was to recapitulate the normal developmental ontogeny of osteoblasts using growth factors (e.g., bone morphogenetic proteins). In contrast, the effects of biophysical stimuli alone on such outcomes remain, at best, partially understood. This in vitro study examined and optimized the effects of alternating electric current alone on the differentiation of adult human mesenchymal stem cells (hMSCs) at the cell population and single-cell levels. hMSCs, cultured on flat, indium-tin-oxide-coated glass in the absence of supplemented exogenous growth factors were exposed to alternating electric current (5-40 μA, 5-10 Hz frequency, sinusoidal waveform), for 1-24 h daily for up to 21 consecutive days. Compared to results obtained from the respective controls, hMSC populations exposed to the alternating electric current alone (in the absence of exogenous growth factors) expressed genes at various stages of differentiation (specifically, TAZ, Runx-2, Osterix, Osteopontin, and Osteocalcin). Optimal osteogenic differentiation was achieved when hMSCs were exposed to a 10 μA, 10 Hz alternating electric current for 6 h daily for up to 21 days. Exclusive osteodifferentiation was observed since genes for the chondrocyte (Collagen Type II) and adipocyte (FABP-4) lineages were not expressed under all conditions of the biophysical stimulus tested. Single cell mRNAs for 45 genes (indicative of hMSC differentiation) were monitored using Fluidigm Systems. Homogeneous expression of the early osteodifferentiation genes (specifically, TAZ and Runx-2) was observed in hMSCs exposed to the alternating electric current at 7 and 21 days. Heterogeneity for all other genes monitored was observed in hMSCs exposed to alternating electric current and in their respective controls. These results provide the first glimpse of gene expression in differentiating hMSCs at the cell population and single-cell levels and represent novel approaches for stem cell differentiation pertinent to new tissue formation.

Extracellular heat shock protein 70 promotes osteogenesis of human mesenchymal stem cells through activation of the ERK signaling pathway

Heat shock proteins have protective effects when cells are exposed to stress. However, the relationship between extracellular heat shock protein 70 (eHSP70) and osteogenesis of hMSCs has not been reported. The results of this study showed that HSP70 (200 ng/ml) increases alkaline phosphatase activity and promotes hMSC mineralization. Under osteogenic induction conditions, HSP70 significantly upregulated the expression of osteo-specific genes, such as the runt family transcription factor Runx2 and osterix (OSX). Comparative expression profiling by microarray and pathway analyses revealed that HSP70 promotes osteogenesis of hMSCs through activation of the ERK signaling pathway. HSP70 may be a potential therapeutic agent for the treatment of bone nonunion.

MicroRNA-24 Regulates Osteogenic Differentiation via Targeting T-Cell Factor-1

MicroRNAs (miRNAs) have been reported to have diverse biological roles in regulating many biological processes, including osteogenic differentiation. In the present study, we identified that miR-24 was a critical regulator during osteogenic differentiation. We found that overexpression of miR-24 significantly inhibited osteogenic differentiation, which decreased alkaline phosphatase activity, matrix mineralization and the expression of osteogenic differentiation markers. In contrast, inhibition of miR-24 exhibited an opposite effect. Furthermore, we delineated that miR-24 regulates post-transcriptionals of T-cell factor-1 (Tcf-1) via targeting the 3'-untranslated region (UTR) of Tcf-1 mRNA. MiR-24 was further found to regulate the protein expression of Tcf-1 in the murine osteoprogenitors cells and bone mesenchymal stem cells. Additionally, the positive effect of miR-24 suppression on osteoblast differentiation was apparently abrogated by Tcf-1 silencing. Taken together, our data suggest that miR-24 participates in osteogenic differentiation by targeting and regulating Tcf-1 expression in osteoblastic cells.

A 3D ex vivo mandible slice system for longitudinal culturing of transplanted dental pulp progenitor cells

Harnessing mesenchymal stem cells for tissue repair underpins regenerative medicine. However, how the 3D tissue matrix maintains such cells in a quiescent state whilst at the same time primed to respond to tissue damage remains relatively unknown. Developing more physiologically relevant 3D models would allow us to better understand the matrix drivers and influence on cell‐lineage differentiation in situ. In this study, we have developed an ex vivo organotypic rat mandible slice model; a technically defined platform for the culture and characterization of dental pulp progenitor cells expressing GFP driven by the β‐actin promoter (cGFP DPPCs). Using confocal microscopy we have characterized how the native environment influences the progenitor cells transplanted into the dental pulp. Injected cGFP‐DPPCs were highly viable and furthermore differentially proliferated in unique regions of the mandible slice; in the dentine region, cGFP‐DPPCs showed a columnar morphology indicative of expansion and lineage differentiation. Hence, we demonstrated the systematic capacity for establishing a dental pulp cell‐micro‐community, phenotypically modified in the tooth (the “biology”); and at the same time addressed technical challenges enabling the mandible slice to be accessible on platforms for high‐content imaging (the biology in a “multiplex” format). © 2015 The Authors. Published by Wiley Periodicals, Inc.

In vivo bone formation by human alveolar-bone-derived mesenchymal stem cells obtained during implant osteotomy using biphasic calcium phosphate ceramics or Bio-Oss as carriers

OBJECTIVES

The aim of this study was to evaluate HA coated with different ratios of TCP as a carrier for hABMSCs obtained during implant osteotomy in comparison to slowly-resorbing biomaterial, Bio-Oss, as a negative control, using in vitro and in vivo experiments.

MATERIALS AND METHODS

Human ABMSCs (hABMSCs) harvested during implant osteotomy were transplanted using HA/TCP or Bio-Oss as carriers in a murine ectopic transplantation model (n = 12). Pore size and cell affinity were evaluated in vitro. The area of newly formed bone was analyzed histometrically, the number of osteocytes was counted, and immunohistochemical staining was conducted against several markers of osteogenesis, including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX-2), osteocalcin (OCN), and osteopontin (OPN). Osteoclast formation was evaluated by tartrate-resistant acid phosphatase staining.

RESULTS

The carrier materials had comparable pore sizes. The cell affinity assay resulted in a high proportion of cell adhesion (>90%) in all experimental groups. Substantial new bone and osteocyte formation was observed on both HA/TCP carriers, whereas it was minimal with Bio-Oss. Positive immunostaining for ALP, RUNX-2, OCN, and OPN was observed with HA/TCP, but only limited expression of osteogenic markers with Bio-Oss. Conversely, there was a minimal osteoclast presence with Bio-Oss, but a significant presence of osteoclasts with both HA/TCP carriers.

CONCLUSIONS

Both types of scaffolds, BCP and Bio-Oss, showed high stem cell-carrying potential, but the in vivo healing patterns of their complexes with hABMSC could be affected by the microenvironment on the surfaces of the scaffolds.

TGF-β/BMP signaling and other molecular events: regulation of osteoblastogenesis and bone formation

Transforming growth factor-beta (TGF-β)/bone morphogenetic protein (BMP) plays a fundamental role in the regulation of bone organogenesis through the activation of receptor serine/threonine kinases. Perturbations of TGF-β/BMP activity are almost invariably linked to a wide variety of clinical outcomes, i.e., skeletal, extra skeletal anomalies, autoimmune, cancer, and cardiovascular diseases. Phosphorylation of TGF-β (I/II) or BMP receptors activates intracellular downstream Smads, the transducer of TGF-β/BMP signals. This signaling is modulated by various factors and pathways, including transcription factor Runx2. The signaling network in skeletal development and bone formation is overwhelmingly complex and highly time and space specific. Additive, positive, negative, or synergistic effects are observed when TGF-β/BMP interacts with the pathways of MAPK, Wnt, Hedgehog (Hh), Notch, Akt/mTOR, and miRNA to regulate the effects of BMP-induced signaling in bone dynamics. Accumulating evidence indicates that Runx2 is the key integrator, whereas Hh is a possible modulator, miRNAs are regulators, and β-catenin is a mediator/regulator within the extensive intracellular network. This review focuses on the activation of BMP signaling and interaction with other regulatory components and pathways highlighting the molecular mechanisms regarding TGF-β/BMP function and regulation that could allow understanding the complexity of bone tissue dynamics.

Genomic analyses of early peri-implant bone healing in humans: a systematic review

Objective

The objective of the study was to systematically review the literature for studies reporting gene expression analyses (GEA) of the biological processes involved in early human peri-implant bone healing.

Methods

Electronic databases (MEDLINE, EMBASE) were searched in duplicate. Controlled and uncontrolled studies reporting GEA of human peri-implant tissues - including ≥5 patients and ≥2 time points - during the first 4 weeks of healing were eligible for inclusion. Methodological quality and risk of bias were also assessed.

Results

Four exploratory studies were included in reporting GEA of either tissues attached to SLA or SLActive implants after 4 to 14 days or cells attached to TiOBlast or Osseospeed implants after 3 to 7 days. A total of 111 implants from 43 patients were analyzed using validated array methods; however, considerable heterogeneity and risk of bias were detected. A consistent overall pattern of gene expression was observed; genes representing an immuno-inflammatory response were overexpressed at days 3 to 4, followed by genes representing osteogenic processes at day 7. Genes representing bone remodeling, angiogenesis, and neurogenesis were expressed concomitantly with osteogenesis. Several regulators of these processes, such as cytokines, growth factors, transcription factors, and signaling pathways, were identified. Implant surface properties seemed to influence the healing processes at various stages via differential gene expression.

Conclusion

Limited evidence from gene expression studies in humans indicates that osteogenic processes commence within the first post-operative week and they appear influenced at various stages by implant surface properties.

Aberrant gene expression profiles, during in vitro osteoblast differentiation, of telomerase deficient mouse bone marrow stromal stem cells (mBMSCs)

Background

Telomerase deficiency has been associated with inadequate differentiation of mesenchymal stem cells. However, the effect of telomerase deficiency on differential regulation of osteoblast specific genes, based on functional gene grouping, during in vitro osteoblast differentiation has not been reported before.

Results

To examine these effects, Terc^-/- BMSCs (bone marrow stromal stem cells) were employed which exhibited reduced proliferation during in vitro osteogenesis along with increased population doubling time and level compared to wild type (WT) BMSCs during the normal culture. Osteogenic super array at day 10 of osteoblast differentiation revealed that telomerase deficiency strongly affected the osteoblast commitment by down-regulating Runx2, Twist and Vdr – known transcription regulators of osteogenesis. Similarly, in Terc^-/- BMSCs a marked reduction in other genes engaged in various phases of osteoblast differentiation were observed, such as Fgfr2 involved in bone mineralization, Phex and Dmp1 engaged in ossification, and Col11a1 and Col2a1 involved in cartilage condensation. A similar trend was observed for genes involved in osteoblast proliferation (Tgfb1, Fgfr2 and Pdgfa) and bone mineral metabolism (Col1a1, Col2a1, Col1a2 and Col11a1). More profound changes were observed in genes engaged in extracellular matrix production: Col1a1, Col1a2, Mmp10, Serpinh1 and Col4a1.

Conclusion

Taken together, these data suggest that telomerase deficiency causes impairment of BMSCs differentiation into osteoblasts affecting commitment, proliferation, matrix mineralization and maturation. Thus, modulating telomerase in BMSCs with advanced aging could improve BMSCs responsiveness towards osteoblast differentiation signals, optimal for osteoblast commitment, proliferation and maturation processes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0116-4) contains supplementary material, which is available to authorized users.

Fucoidan promotes osteoblast differentiation via JNK- and ERK-dependent BMP2-Smad 1/5/8 signaling in human mesenchymal stem cells

Fucoidan has attracted attention as a potential drug because of its biological activities, which include osteogenesis. However, the molecular mechanisms involved in the osteogenic activity of fucoidan in human alveolar bone marrow-derived mesenchymal stem cells (hABM-MSCs) remain largely unknown. We investigated the action of fucoidan on osteoblast differentiation in hABM-MSCs and its impact on signaling pathways. Its effect on proliferation was determined using the crystal violet staining assay. Osteoblast differentiation was evaluated based on alkaline phosphatase (ALP) activity and the mRNA expression of multiple osteoblast markers. Calcium accumulation was determined by Alizarin red S staining. We found that fucoidan induced hABM-MSC proliferation. It also significantly increased ALP activity, calcium accumulation and the expression of osteoblast-specific genes, such as ALP, runt-related transcription factor 2, type I collagen-α 1 and osteocalcin. Moreover, fucoidan induced the expression of bone morphogenetic protein 2 (BMP2) and stimulated the activation of extracellular signal-related kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase by increasing phosphorylation. However, the effect of fucoidan on osteogenic differentiation was inhibited by specific inhibitors of ERK (PD98059) and JNK (SP600125) but not p38 (SB203580). Fucoidan enhanced BMP2 expression and Smad 1/5/8, ERK and JNK phosphorylation. Moreover, the effect of fucoidan on osteoblast differentiation was diminished by BMP2 knockdown. These results indicate that fucoidan induces osteoblast differentiation through BMP2-Smad 1/5/8 signaling by activating ERK and JNK, elucidating the molecular basis of the osteogenic effects of fucoidan in hABM-MSCs.

Osteoblast differentiation and survival: A role for A2B adenosine receptor allosteric modulators

The A2B adenosine receptor (A2B AR), activated in response to high levels of endogenous adenosine, is the major AR subtype involved in mesenchymal stem cell (MSC) differentiation to osteoblasts and bone formation. For this reason, targeting of A2B AR with selective allosteric modulators may represent a promising pharmacological approach to the treatment of bone diseases. Herein, we report the characterization of a 3-keto-indole derivative, 2-(1-benzyl-1H-indol-3-yl)-2-oxo-N-phenylacetamide (KI-7), as A2B AR positive allosteric modulator in MSCs, demonstrating that this compound is able to potentiate the effects of either adenosine and synthetic orthosteric A2B AR agonists in mediating osteoblast differentiation in vitro. In detail, we observed that MSC treatment with KI-7 determined an increase in the expression of osteoblast-related genes (Runx2 and osterix) and osteoblast marker proteins (phosphatase alkaline and osteocalcin), associated with a stimulation of osteoblast mineralization. In the early phase of differentiation programme, KI-7 significantly potentiated physiological and A2B AR agonist-mediated down-regulation of IL-6 release. Conversely, during the late stage of differentiation, when most of the cells have an osteoblast phenotype, KI-7 caused a sustained raise in IL-6 levels and an improvement in osteoblast viability. These data suggest that a positive allosteric modulation of A2B AR not only favours MSC commitment to osteoblasts, but also ensures a greater survival of mature osteoblasts. Our study paves the way for a therapeutic use of selective positive allosteric modulators of A2B AR in the control of osteoblast differentiation, bone formation and fracture repair.

Gender- and region-specific alterations in bone metabolism in Scarb1-null female mice

A positive correlation between plasma levels of HDL and bone mass has been reported by epidemiological studies. As scavenger receptor class B, type I (SR-BI), the gene product of Scarb1, is known to regulate HDL metabolism, we recently characterized bone metabolism in Scarb1-null mice. These mice display high femoral bone mass associated with enhanced bone formation. As gender differences have been reported in HDL metabolism and SR-BI function, we investigated gender-specific bone alterations in Scarb1-null mice by microtomography and histology. We found 16% greater relative bone volume and 39% higher bone formation rate in the vertebrae from 2-month-old Scarb1-null females. No such alteration was seen in males, indicating gender- and region-specific differences in skeletal phenotype. Total and HDL-associated cholesterol levels, as well as ACTH plasma levels, were increased in both Scarb1-null genders, the latter being concurrent to impaired corticosterone response to fasting. Plasma levels of estradiol did not differ between null and WT females, suggesting that the estrogen metabolism alteration is not relevant to the higher vertebral bone mass in female Scarb1-null mice. Constitutively, high plasma levels of leptin along with 2.5-fold increase in its expression in white adipose tissue were measured in female Scarb1-null mice only. In vitro exposure of bone marrow stromal cells to ACTH and leptin promoted osteoblast differentiation as evidenced by increased gene expression of osterix and collagen type I alpha. Our results suggest that hyperleptinemia may account for the gender-specific high bone mass seen in the vertebrae of female Scarb1-null mice.

PLGA/nHA hybrid nanofiber scaffold as a nanocargo carrier of insulin for accelerating bone tissue regeneration

The development of tissue engineering in the field of orthopedic surgery is booming. Two fields of research in particular have emerged: approaches for tailoring the surface properties of implantable materials with osteoinductive factors as well as evaluation of the response of osteogenic cells to these fabricated implanted materials (hybrid material). In the present study, we chemically grafted insulin onto the surface of hydroxyapatite nanorods (nHA). The insulin-grafted nHAs (nHA-I) were dispersed into poly(lactide-co-glycolide) (PLGA) polymer solution, which was electrospun to prepare PLGA/nHA-I composite nanofiber scaffolds. The morphology of the electrospun nanofiber scaffolds was assessed by field emission scanning electron microscopy (FESEM). After extensive characterization of the PLGA/nHA-I and PLGA/nHA composite nanofiber scaffolds by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM), the PLGA/nHA-I and PLGA/nHA (used as control) composite nanofiber scaffolds were subjected to cell studies. The results obtained from cell adhesion, alizarin red staining, and Von Kossa assay suggested that the PLGA/nHA-I composite nanofiber scaffold has enhanced osteoblastic cell growth, as more cells were proliferated and differentiated. The fact that insulin enhanced osteoblastic cell proliferation will open new possibilities for the development of artificial scaffolds for bone tissue regeneration.

Biointerface control of electrospun fiber scaffolds for bone regeneration: engineered protein link to mineralized surface

Control over the interface of biomaterials that favors the initial adhesion and subsequent differentiation of stem cells is one of the key strategies in bone tissue engineering. Here we engineer the interface of biopolymer electrospun fiber matrices with a fusion protein of fibronectin 9-10 domain (FNIII9-10) and osteocalcin (OCN), aiming to stimulate mesenchymal stem cell (MSC) functions, including initial adhesion, growth and osteogenic differentiation. In particular, a specific tethering of FNIII9-10-OCN protein was facilitated by the hydroxyapatite (HA) mineralization of the biopolymer surface through a molecular recognition of OCN to the HA crystal lattice. The FNIII9-10-OCN anchorage to the HA-mineralized fiber was observed to be highly specific and tightly bound to preserve stability over a long period. Initial cell adhesion levels, as well as the spreading shape and process, of MSCs within 24h were strikingly different between the fibers linked with and without fusion protein. Significant up-regulations in the mRNA expression of adhesion signaling molecules occurred with the fusion protein link, as analyzed by the reverse transcriptase polymerase chain reaction. The expression of a series of osteogenic-related genes at later stages, over 2-3weeks, was significantly improved in the fusion protein-tailored fiber, and the osteogenic protein levels were highly stimulated, as confirmed by immunofluorescence imaging and fluorescence-activated cell sorting analyses. In vivo study in a rat calvarium model confirmed a higher quantity of new bone formation in the fiber linked with fusion protein, and a further increase was noticed when the MSCs were tissue-engineered with the fusion protein-linked fiber. Collectively, these results indicate that FN-OCN fusion protein links via HA mineralization is a facile tool to generate a biointerface with cell-attractive and osteogenic potential, and that the engineered fibrous matrix is a potential bone regenerative scaffold.

Inflammatory and bone remodeling responses to the cytolethal distending toxins

The cytolethal distending toxins (CDTs) are a family of exotoxins produced by a wide range of Gram-negative bacteria. They are known for causing genotoxic stress to the cell, resulting in growth arrest and eventually apoptotic cell death. Nevertheless, there is evidence that CDTs can also perturb the innate immune responses, by regulating inflammatory cytokine production and molecular mediators of bone remodeling in various cell types. These cellular and molecular events may in turn have an effect in enhancing local inflammation in diseases where CDT-producing bacteria are involved, such as Aggregatibacter actinomycetemcomitans, Haemophilus ducreyi, Campylobacter jejuni and Helicobacter hepaticus. One special example is the induction of pathological bone destruction in periodontitis. The opportunistic oral pathogen Aggregatibatcer actinoycemetemcomitans, which is involved in the aggressive form of the disease, can regulate the molecular mechanisms of bone remodeling in a manner that favors bone resorption, with the potential involvement of its CDT. The present review provides an overview of all known to-date inflammatory or bone remodeling responses of CDTs produced by various bacterial species, and discusses their potential contribution to the pathogenesis of the associated diseases.

Inflammatory bone loss in experimental periodontitis induced by Aggregatibacter actinomycetemcomitans in interleukin-1 receptor antagonist knockout mice

The interleukin-1 receptor antagonist (IL-1Ra) binds to IL-1 receptors and inhibits IL-1 activity. However, it is not clear whether IL-1Ra plays a protective role in periodontal disease. This study was undertaken to compare experimental periodontitis induced by Aggregatibacter actinomycetemcomitans in IL-1Ra knockout (KO) mice and wild-type (WT) mice. Computed tomography (CT) analysis and hematoxylin-and-eosin (H&E) and tartrate-resistant acid phosphatase (TRAP) staining were performed. In addition, osteoblasts were isolated; the mRNA expression of relevant genes was assessed by real-time quantitative PCR (qPCR); and calcification was detected by Alizarin Red staining. Infected IL-1Ra KO mice exhibited elevated (P, <0.05) levels of antibody against A. actinomycetemcomitans, bone loss in furcation areas, and alveolar fenestrations. Moreover, protein for tumor necrosis factor alpha (TNF-α) and IL-6, mRNA for macrophage colony-stimulating factor (M-CSF), and receptor activator of NF-κB ligand (RANKL) in IL-1Ra KO mouse osteoblasts stimulated with A. actinomycetemcomitans were increased (P, <0.05) compared to in WT mice. Alkaline phosphatase (ALP), bone sialoprotein (BSP), osteocalcin (OCN)/bone gla protein (BGP), and runt-related gene 2 (Runx2) mRNA levels were decreased (P, <0.05). IL-1α mRNA expression was increased, and calcification was not observed, in IL-1 Ra KO mouse osteoblasts. In brief, IL-1Ra deficiency promoted the expression of inflammatory cytokines beyond IL-1 and altered the expression of genes involved in bone resorption in A. actinomycetemcomitans-infected osteoblasts. Alterations consistent with rapid bone loss in infected IL-Ra KO mice were also observed for genes expressed in bone formation and calcification. In short, these data suggest that IL-1Ra may serve as a potential therapeutic drug for periodontal disease.

Oligomerization-induced conformational change in the C-terminal region of Nel-like molecule 1 (NELL1) protein is necessary for the efficient mediation of murine MC3T3-E1 cell adhesion and spreading

NELL1 is a large oligomeric secretory glycoprotein that functions as an osteoinductive factor. NELL1 contains several conserved domains, has structural similarities to thrombospondin 1, and supports osteoblastic cell adhesion through integrins. To define the structural requirements for NELL1-mediated cell adhesion, we prepared a series of recombinant NELL1 proteins (intact, deleted, and cysteine-mutant) from a mammalian expression system and tested their activities. A deletion analysis demonstrated that the C-terminal cysteine-rich region of NELL1 is critical for the cell adhesion activity of NELL1. Reducing agent treatment decreased the cell adhesion activity of full-length NELL1 but not of its C-terminal fragments, suggesting that the intramolecular disulfide bonds within this region are not functionally necessary but that other disulfide linkages in the N-terminal region of NELL1 may be involved in cell adhesion activity. By replacing cysteine residues with serines around the coiled-coil domain of NELL1, which is responsible for oligomerization, we created a mutant NELL1 protein that was unable to form homo-oligomers, and this monomeric mutant showed substantially lower cell adhesion activity than intact NELL1. These results suggest that an oligomerization-induced conformational change in the C-terminal region of NELL1 is important for the efficient mediation of cell adhesion and spreading by NELL1.

New development of carbonate apatite-chitosan scaffold based on lyophilization technique for bone tissue engineering

Carbonate apatite-chitosan scaffolds (CA-ChSs) were fabricated using the lyophilization technique. It was found that ChSs prepared with 200 mg chitosan powder (ChSs200) had well-structured three-dimensional architecture with high porosity and good retentive form without brittleness. In addition, it was shown that the number of osteoblast-like cells MC3T3-E1 proliferated on desalinated ChSs200 was larger than that on the non-desalinated ChSs200. CA-ChSs were fabricated by adding 100 mg carbonate apatite (CA) to 200 mg chitosan gels followed by freeze-drying (CA100ChSs200). SEM observation revealed that CA100ChSs200 had favorable three- dimensional porous structures. The number of living cells increased more rapidly on CA100ChSs200 prepared with different amounts of CA than on ChSs. ALP activity significantly increased after day 14 and reached a plateau after day 21 in ChSs200 and CA100ChSs200. It was concluded that newly developed CA100ChSs200 may be a possible scaffold material for tissue engineering.

Epithelial sodium channel enhanced osteogenesis via cGMP/PKGII/ENaC signaling in rat osteoblast

The amiloride-sensitive epithelial sodium channel (ENaC) is a major contributor to intracellular sodium homeostasis. In addition to epithelial cells, osteoblasts (Obs) express functional ENaCs. Moreover, a correlation between bone Na content and bone disease has been reported, suggesting that ENaC-mediated Na(+) regulation may influence osteogenesis. Obs were isolated and cultured by enzyme digestion. Cell proliferation and differentiation were evaluated by WST-8 assay kit and AKP assay kit respectively. PKGII expression was silenced by siRNA. The mRNA expression was investigated by semi-quantitative PCR and the protein expression was determined by Western-blot. The cell-permeable cGMP analog 8-(4-chlorophenylthio)-cGMP (8-pCPT-cGMP) increased α-ENaC channel expression in primary rat Obs as indicated by RT-PCR. In addition, 8-pCPT-cGMP stimulation enhanced expression of the mRNA encoding cGMP-dependent protein kinases II (PKGII). The cGMP analog also promoted osteoblast proliferation, differentiation and induced the expression of several osteogenic genes, including core binding factor al, osteocalcin, alkaline phosphatase, collagen type I, and osteopontin. Furthermore, the expression of α-ENaC, the main functional subunit of ENaC, was reduced when a small interfering RNA specific for PKGII was introduced into Obs. Treatment with 8-pCPT-cGMP in cells transfected with the siRNA for PKGII partially reversed downregulated α-ENaC mRNA expression. Our results suggest that 8-pCPT-cGMP stimulates proliferation, differentiation, and osteogenic gene expression in Obs through cGMP/PKGII-dependent regulation of ENaC channel expression. The cGMP/PKGII signaling pathway is a potential target for pharmaceutical interventions to treat metabolic bone diseases.

Electrical stimulation to promote osteogenesis using conductive polypyrrole films

In this study, we developed an electrical cell culture and monitoring device. Polypyrrole (PPy) films with different resistances were fabricated as conductive surfaces to investigate the effect of substrate-mediated electrical stimulation. The physical and chemical properties of the devices, as well as their biocompatibilities, were thoroughly evaluated. These PPy films had a dark but transparent appearance, on which the surface cells could be easily observed. After treating with the osteogenic medium, rat bone marrow stromal cells cultured on the PPy films differentiated into osteoblasts. The cells grown on the PPy films had up-regulated osteogenic markers, and an alkaline phosphatase activity assay showed that the PPy films accelerated cell differentiation. Alizarin red staining and calcium analysis suggested that the PPy films promoted osteogenesis. Finally, PPy films were subjected to a constant electric field to elucidate the effect of electrical stimulation on osteogenesis. Compared with the untreated group, electrical stimulation improved calcium deposition in the extracellular matrix. Furthermore, PPy films with lower resistances allowed larger currents to stimulate the surface cells, which resulted in higher levels of mineralization. Overall, these results indicated that this system exhibited superior electroactivity with controllable electrical resistance and that it can be coated directly to produce medical devices with a transparent appearance, which should be beneficial for research on electrical stimulation for tissue regeneration.

Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration

The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre-absorbed with the growth factor. nHA-PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA-PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules.

Dual delivery of rhPDGF-BB and bone marrow mesenchymal stromal cells expressing the BMP2 gene enhance bone formation in a critical-sized defect model

Bone tissue healing is a dynamic, orchestrated process that relies on multiple growth factors and cell types. Platelet-derived growth factor-BB (PDGF-BB) is released from platelets at wound sites and induces cellular migration and proliferation necessary for bone regeneration in the early healing process. Bone morphogenetic protein-2 (BMP-2), the most potent osteogenic differentiation inducer, directs new bone formation at the sites of bone defects. This study evaluated a combinatorial treatment protocol of PDGF-BB and BMP-2 on bone healing in a critical-sized defect model. To mimic the bone tissue healing process, a dual delivery approach was designed to deliver the rhPDGF-BB protein transiently during the early healing phase, whereas BMP-2 was supplied by rat bone marrow stromal cells (BMSCs) transfected with an adenoviral vector containing the BMP2 gene (AdBMP2) for prolonged release throughout the healing process. In in vitro experiments, the dual delivery of rhPDGF-BB and BMP2 significantly enhanced cell proliferation. However, the osteogenic differentiation of BMSCs was significantly suppressed even though the amount of BMP-2 secreted by the AdBMP2-transfected BMSCs was not significantly affected by the rhPDGF-BB treatment. In addition, dual delivery inhibited the mRNA expression of BMP receptor type II and Noggin in BMSCs. In in vivo experiments, critical-sized calvarial defects in rats showed enhanced bone regeneration by dual delivery of autologous AdBMP2-transfected BMSCs and rhPDGF-BB in both the amount of new bone formed and the bone mineral density. These enhancements in bone regeneration were greater than those observed in the group treated with AdBMP2-transfected BMSCs alone. In conclusion, the dual delivery of rhPDGF-BB and AdBMP2-transfected BMSCs improved the quality of the regenerated bone, possibly due to the modulation of PDGF-BB on BMP-2-induced osteogenesis.

RGD-bearing peptide-amphiphile-hydroxyapatite nanocomposite bone scaffold: an in vitro study

In this study, a fibrous nanocomposite scaffold was developed by combining hydroxyapatite (HA) fibers produced by electrospinning method and arginine-glycine-aspartic acid (RGD)-bearing peptide-amphiphile (PA) gel (PA-RGD) produced by self-assembly and gelation induced by calcium ions. Scanning electron microscope, transmission electron microscope and atomic force microscopy imaging confirmed the successful production of inorganic and organic components of this nanocomposite material. Within the HA, the presence of a CaCO3 phase, improving biodegradation, was shown by x-ray diffraction analysis. The in vitro effectiveness of the PA-RGD/HA scaffold was determined on MC3T3-E1 preosteoblast cultures in comparison with HA matrix and PA-RGD gel. The highest cellular proliferation was obtained on PA-RGD gel, however, alkaline phosphatase activity results denoted that osteogenic differentiation of the cells is more favorable on HA containing matrices with respect to PA-RGD itself. Microscopic observations revealed that all three matrices support cell attachment and proliferation. Moreover, cells form bridges between the HA and PA-RGD components of the nanocomposite scaffold, indicating the integrity of the biphasic components. According to the real time-polymerase chain reaction (RT-PCR) analyses, MC3T3-E1 cells expressed significantly higher osteocalcin on all matrices. Bone sialoprotein (BSP) expression level is ten-fold higher on PA-RGD/HA nanocomposite scaffolds than that of HA and PA-RGD scaffolds and the elevated expression of BSP on PA-RGD/HA nanocomposite scaffolds suggested higher mineralized matrix on this novel scaffold. Based on the results obtained in this study, the combination of HA nanofibers and PA-RGD gel takes advantage of good structural integrity during the cell culture, besides the osteoinductive and osteoconductive properties of the nanofibrous scaffold.

Buccal bone formation after flapless extraction: a randomized, controlled clinical trial comparing recombinant human bone morphogenetic protein 2/absorbable collagen carrier and collagen sponge alone

BACKGROUND

Flapless extraction of teeth allows for undisturbed preservation of the nearby periosteum and a source of osteoprogenitor cells. Recombinant human bone morphogenetic protein 2 (rhBMP-2) has been used for different bone augmentation purposes with great osteoinductive capacity. The aim of this study is to compare the bone regenerative ability of rhBMP-2 on an absorbable collagen sponge (ACS) carrier to a collagen sponge (CS) alone in extraction sites with ≥50% buccal dehiscence.

METHODS

Thirty-nine patients requiring extraction of a hopeless tooth with ≥50% buccal dehiscence were enrolled. After flapless extraction and randomization, either rhBMP-2/ACS carrier or CS alone was placed in the extraction site. After extraction, a baseline cone beam computed tomography (CBCT) scan was obtained of the site, and a similar scan was obtained 5 months postoperatively. Medical imaging and viewing software were used to compare the baseline and 5-month postoperative images of the study site and assess ridge width measurements, vertical height changes, and buccal plate regeneration.

RESULTS

Radiographically, CBCT analysis showed that with ≥50% of buccal bone destruction, rhBMP-2/ACS was able to regenerate a portion of the lost buccal plate, maintain theoretical ridge dimensions, and allow for implant placement 5 months after extraction. The test group performed significantly (P <0.05) better in regard to clinical buccal plate regeneration (4.75 versus 1.85 mm), clinical ridge width at 5 months (6.0 versus 4.62 mm), and radiographic ridge width at 3 mm from the alveolar crest (6.17 versus 4.48 mm) after molar exclusion. There was also significantly (P <0.05) less remaining buccal dehiscence, both clinically (6.81 versus 10.0 mm) and radiographically (3.42 versus 5.16 mm), at 5 months in the test group. Significantly (P <0.05) more implants were placed in the test group without the need for additional augmentation. The mean loss in vertical ridge height (lingual/palatal) was less in the test sites but was not significantly (P = 0.514) different between the test and control groups (0.39 versus 0.64 mm).

CONCLUSIONS

rhBMP-2/ACS compared to CS alone used in flapless extraction sites with a buccal dehiscence is able to regenerate lost buccal plate, maintain theoretical ridge dimensions, and allow for implant placement 5 months later.

JNK signaling plays an important role in the effects of TNF-α and IL-1β on in vitro osteoblastic differentiation of cultured human periosteal-derived cells

The purpose of this study was to examine the effects of TNF-α and IL-1β on in vitro osteoblastic differentiation of cultured human periosteal-derived cells. To examine the effects of TNF-α and IL-1β on in vitro osteoblastic differentiation of cultured human periosteal-derived cells, the cells cultured in the osteogenic induction medium were treated with 0.1-10 ng/ml TNF-α and 0.01-1 ng/ml IL-1β. TNF-α and IL-1β enhanced the alkaline phosphatase (ALP) activity and alizarin red S staining in cultured human periosteal-derived cells. However, these cytokines did not stimulate the Runt-related transcription factor (Runx) 2 activity and osteocalcin secretion. The ALP activity was decreased in the periosteal-derived cells pretreated with mitogen activated protein kinase (MAPK) inhibitors and then treated with TNF-α or IL-1β. Among the periosteal-derived cells pretreated with MAPK inhibitors, the ALP activity was markedly decreased in the cells pretreated with SP 600125, the specific inhibitor of C-Jun N-terminal kinase (JNK). The periosteal-derived cells treated with TNF-α and IL-1β showed an increase in extracellular signal-regulated kinase (ERK) and JNK phosphorylation. Among the ERK and JNK phosphorylation, JNK phosphorylation was strongly observed in the cells. These results suggest that TNF-α and IL-1β increased the in vitro osteoblastic differentiation of cultured human periosteal-derived cells by enhancing the ALP activity and mineralization process, but not by Runx2 activation. The functional role of TNF-α and IL-1β in increasing the ALP activity and mineralization of periosteal-derived cells primarily depends on the JNK signaling among the MAPK pathways.

Polyelectrolyte multilayer coating with two regulatory molecules on titanium: construction and its biological effects

Aim: This study aimed at constructing a novel disulfide-crosslinked collagen I/hyaluronic acid polyelectrolyte multilayer (PEM) coating incorporated with bFGF and arginine–glycine–aspartic acid on titanium via the layer-by-layer technique, and evaluating its biological effects. Materials & methods: The surface topography and components, thickness, degradation behaviors and bFGF release profiles of the PEM coating were investigated. The effects of the PEM coating on osteoprogenitor cell growth and bone implant interfacial binding strength in the rabbit femur model were evaluated separately. Results: The formation of disulfide bonds improved the stability of the PEM coating, resulting in a coating that can release bFGF in a slow and sustained manner. Biological evaluations revealed that the resultant PEM coating on titanium promoted various cell behaviors and enhanced the binding strength. Conclusion: The employed cotreatment regimen enabled bFGF and arginine–glycine–aspartic acid to have a synergistic effect on the cell responses, which, in turn, improved the osseointegration.

Original submitted 26 January 2012; Revised submitted 10 June 2012; Published online 5 February 2013

The association of IL-6 and IL-6R gene polymorphisms with chronic periodontitis in a Chinese population

OBJECTIVE

The aim of our investigation is to reveal the association of interleukin-6 (IL-6) and interleukin-6 receptor (IL-6R) gene polymorphisms with chronic periodontitis in Northwestern Chinese Han Population.

MATERIAL AND METHODS

A case-control study of 199 cases of chronic periodontitis patients and 216 healthy controls was performed. Genomic DNA was isolated from whole venous blood, and four single nucleotide polymorphisms (IL-6 -572 G/C and -1363 G/T, IL-6R -183 G/A and +48892 A/C) were analysed using polymerase chain reaction, followed by restriction fragment length polymorphism analysis and sequencing methods.

RESULTS

Our SNP analyses showed that the distribution of the IL-6 -572 G/C and IL-6R -183 G/A polymorphisms did not differ between patients and controls. The frequency of the IL-6 -1363 G/T genotype GG was significantly increased chronic periodontitis cases (P = 0.023, odds ratio (OR) = 2.825 adjusted for gender and age.) The IL-6R +48892 A/C polymorphisms genotype CC was found to be protective against chronic periodontitis (P = 0.004, OR = 0.318 adjusted for gender and age.). In addition, compared with the other haplotypes, haplotype A(+48892) A(-183) was significantly associated with chronic periodontitis, with an odds ratio of 0.720 (P = 0.0235).

CONCLUSION

Our results suggest that the IL-6 -1363 G/T and IL-6R +48892 A/C polymorphisms may contribute to genetic susceptibility to chronic periodontitis in Northwestern Chinese Han population.