Gene expression of growth differentiation factors in the developing periodontium of rat molars

Prohibitin modulates periodontium differentiation in mice development

Introduction: Prohibitin (PHB) is an essential scaffold protein that modulates signaling pathways controlling cell survival, metabolism, inflammation, and bone formation. However, its specific role in periodontium development remains less understood. This study aims to elucidate the expression pattern and function of PHB in periodontium development and its involvement in alveolar bone formation. Methods: Immunolocalization of PHB in the periodontium of postnatal (PN) mice were examined. Phb morpholino was micro-injected into the right-side mandible at PN5, corresponding to the position where the alveolar bone process forms in relation to the lower first molar. The micro-injection with a scramble control (PF-127) and the left-side mandibles were used as control groups. Five days post-micro-injection, immunohistochemical analysis and micro-CT evaluation were conducted to assess bone mass and morphological changes. Additionally, expression patterns of signaling molecules were examined following Phb downregulation using 24-h in vitro cultivation of developing dental mesenchyme at E14.5. Results: The immunostaining of PHB showed its localization in the periodontium at PN5, PN8, and PN10. The in vitro cultivation of dental mesenchyme resulted in alterations in Bmps, Runx2, and Wnt signalings after Phb knock-down. At 5 days post-micro-injection, Phb knocking down showed weak immunolocalizations of runt-related transcription factor (RUNX2) and osteocalcin (OCN). However, knocking down Phb led to histological alterations characterized by decreased bone mass and stronger localizations of Ki67 and PERIOSTIN in the periodontium compared 1 to control groups. The micro-CT evaluation showed decreased bone volume and increased PDL space in the Phb knock-down specimens, suggesting its regulatory role in bone formation. Discussion: The region-specific localization of PHB in the margin where alveolar bone forms suggests its involvement in alveolar bone formation and the differentiation of the periodontal ligament. Overall, our findings suggest that Phb plays a modulatory role in alveolar bone formation by harmoniously regulating bone-forming-related signaling molecules during periodontium development.

BMP signaling in the development and regeneration of tooth roots: from mechanisms to applications

Short root anomaly (SRA), along with caries, periodontitis, and trauma, can cause tooth loss, affecting the physical and mental health of patients. Dental implants have become widely utilized for tooth restoration; however, they exhibit certain limitations compared to natural tooth roots. Tissue engineering-mediated root regeneration offers a strategy to sustain a tooth with a physiologically more natural function by regenerating the bioengineered tooth root (bio-root) based on the bionic principle. While the process of tooth root development has been reported in previous studies, the specific molecular mechanisms remain unclear. The Bone Morphogenetic Proteins (BMPs) family is an essential factor regulating cellular activities and is involved in almost all tissue development. Recent studies have focused on exploring the mechanism of BMP signaling in tooth root development by using transgenic animal models and developing better tissue engineering strategies for bio-root regeneration. This article reviews the unique roles of BMP signaling in tooth root development and regeneration.

Current and future trends in periodontal tissue engineering and bone regeneration

Periodontal tissue engineering involves a multi-disciplinary approach towards the regeneration of periodontal ligament, cementum and alveolar bone surrounding teeth, whereas bone regeneration specifically applies to ridge reconstruction in preparation for future implant placement, sinus floor augmentation and regeneration of peri-implant osseous defects. Successful periodontal regeneration is based on verifiable cementogenesis on the root surface, oblique insertion of periodontal ligament fibers and formation of new and vital supporting bone. Ultimately, regenerated periodontal and peri-implant support must be able to interface with surrounding host tissues in an integrated manner, withstand biomechanical forces resulting from mastication, and restore normal function and structure. Current regenerative approaches utilized in everyday clinical practice are mainly guided tissue/bone regeneration-based. Although these approaches have shown positive outcomes for small and medium-sized defects, predictability of clinical outcomes is heavily dependent on the defect morphology and clinical case selection. In many cases, it is still challenging to achieve predictable regenerative outcomes utilizing current approaches. Periodontal tissue engineering and bone regeneration (PTEBR) aims to improve the state of patient care by promoting reconstitution of damaged and lost tissues through the use of growth factors and signaling molecules, scaffolds, cells and gene therapy. The present narrative review discusses key advancements in PTEBR including current and future trends in preclinical and clinical research, as well as the potential for clinical translatability.

Adsorption and Release of Growth Factors from Four Different Porcine-Derived Collagen Matrices

Xenogeneic acellular collagen matrices represent a safe alternative to autologous soft tissue transplants in periodontology and implant dentistry. Here, we aimed to investigate the adsorption and release of growth factors from four porcine-derived collagen matrices using enzyme-linked immunosorbent assay. Non-crosslinked collagen matrix (NCM), crosslinked collagen matrix (CCM), dried acellular dermal matrix (DADM), and hydrated acellular dermal matrix (HADM) adsorbed each of the following growth factors, TGF-β1, FGF-2, PDGF-BB, GDF-5 and BMP-2, with an efficiency close to 100%. Growth factor release for a 13-day period was in the range of 10-50% of the adsorbed protein, except for the BMP-2 release that was in the range of 5-7%. Generally, protein release occurred in two phases. Phase I was arbitrary defined by the highest release from the matrices, usually within 24 h. Phase II, spanning the period immediately after the peak release until day 13, corresponded to the delayed release of the growth factors from the deeper layers of the matrices. HADM showed significantly (P < 0.001) higher TGF-β1, FGF-2, and PDGF-BB release in phase II, compared to the rest of the matrices. NCM exhibited significantly (P < 0.001) higher FGF-2 release in phase II, compared to CCM and DADM as well as a characteristic second peak in PDGF-BB release towards the middle of the tested period. In contrast to NCM and HADM, CCM and DADM showed a gradual and significantly higher release of GDF-5 in the second phase. Several burst releases of BMP-2 were characteristic for all matrices. The efficient adsorption and sustained protein release in the first 13 days, and the kinetics seen for HADM, with a burst release within hours and high amount of released growth factor within a secondary phase, may be beneficial for the long-term tissue regeneration following reconstructive periodontal surgery.

Facial shape and allometry quantitative trait locus intervals in the Diversity Outbred mouse are enriched for known skeletal and facial development genes

The biology of how faces are built and come to differ from one another is complex. Discovering normal variants that contribute to differences in facial morphology is one key to untangling this complexity, with important implications for medicine and evolutionary biology. This study maps quantitative trait loci (QTL) for skeletal facial shape using Diversity Outbred (DO) mice. The DO is a randomly outcrossed population with high heterozygosity that captures the allelic diversity of eight inbred mouse lines from three subspecies. The study uses a sample of 1147 DO animals (the largest sample yet employed for a shape QTL study in mouse), each characterized by 22 three-dimensional landmarks, 56,885 autosomal and X-chromosome markers, and sex and age classifiers. We identified 37 facial shape QTL across 20 shape principal components (PCs) using a mixed effects regression that accounts for kinship among observations. The QTL include some previously identified intervals as well as new regions that expand the list of potential targets for future experimental study. Three QTL characterized shape associations with size (allometry). Median support interval size was 3.5 Mb. Narrowing additional analysis to QTL for the five largest magnitude shape PCs, we found significant overrepresentation of genes with known roles in growth, skeletal and facial development, and sensory organ development. For most intervals, one or more of these genes lies within 0.25 Mb of the QTL's peak. QTL effect sizes were small, with none explaining more than 0.5% of facial shape variation. Thus, our results are consistent with a model of facial diversity that is influenced by key genes in skeletal and facial development and, simultaneously, is highly polygenic.

Comparative study of periodontal differentiation propensity of induced pluripotent stem cells from different tissue origins

BACKGROUND

Despite being almost identical to embryonic stem cells, induced pluripotent stem cells (iPSCs) have been shown to possess a residual somatic memory that favors their differentiation propensity into donor tissue. To further confirm this assumption, we compare for the first time the periodontal differentiation tendency of human gingival fibroblast-derived iPSCs (G-iPSCs) and human neonatal skin fibroblast-derived iPSCs (S-iPSCs) to assess whether G-iPSCs could be more efficiently induced toward periodontal cells.

METHODS

We induced G- and S-iPSCs under the treatment of growth/differentiation factor-5 and connective tissue growth factor, respectively, for 14 days. Immunofluorescence staining and real-time polymerase chain reaction were used to compare their expression levels of related markers. Furthermore, a hydrogel carrier was developed to seed these periodontal progenitors for subcutaneous implantation in non-obese diabetic-severe combined immunodeficiency disease mice. Their differentiated periodontal phenotype maintenance was further assayed by HE observation, immunohistochemical staining and immunofluorescence co-localization with pre-labeled PKH67.

RESULTS

As expected, both iPSCs were inclined to differentiate back into their original lineage by expressing higher markers at both gene and protein levels in vitro. HE observation of G-iPSCs-seeded hydrogel constructs present more mineralized structure formation than S-iPSCs-seeded ones. Immunohistochemical staining and immunofluorescence analysis also showed stronger positive staining for periodontal related markers in G-iPSCs-seeded hydrogel constructs.

CONCLUSIONS

Our results preliminarily confirmed that both G- and S-iPSCs were inclined to differentiate back into their original tissue in vitro. Animal study further confirmed the phenotype maintenance of periodontal differentiated G-iPSCs, which highlighted their significant implications for therapeutic use in periodontal regeneration.

Surface Modification of Titanium with BMP-2/GDF-5 by a Heparin Linker and Its Efficacy as a Dental Implant

In this study, we prepared human bone morphogenetic protein-2 (hBMP-2)/human growth and differentiation factor-5 (hGDF-5)-coated titanium (Ti) disc and screw types for controlled release of the growth factors (GFs). The two growth factors were coated onto Ti with a smooth surface using their specific interaction with heparin, because they have heparin binding sites in their molecular structures. Efficacy of the two growth factor-coated Ti for enhancement of bone formation and osseointegration was compared to pristine Ti, and hBMP-2- and hGDF-5-coated Ti in vivo. The surface chemical composition, surface morphology, and wettability characteristics of the metal samples were determined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurement, respectively. The initial burst of hBMP-2, hGDF-5, and their combination, occurred within one day of the release study, resulting in 12.5%, 4.5%, and 13.5%/3.2%, and then there was a sustained, even release of these two growth factors from the coated metal for 30 days. In vitro tests revealed that MC3T3-E1 cells cultured on the two growth factor-coated Ti had a higher proliferation rate and a higher activity for alkaline phosphatase (ALP), which led to a larger amount of calcium deposition and larger expressions of type I collagen (COL 1), ALP, and osteocalcin (OCN) mRNAs. In vivo animal tests using ten white New Zealand rabbits showed that the two growth factor-coated Ti enhanced bone formation and osseointegration at the interface between the implants and host bone. In addition, histological evaluation showed that bone remodeling, including bone formation by osteoblasts and bone resorption by osteoclasts, actively occurred between the two growth factor-coated Ti and host bone. Consequently, it is suggested that Ti surface modification with the combination of hBMP-2 and hGDF-5 for the two growth factor-coated Ti implants can improve the clinical properties of implants for orthopedic and dental applications.

The use of heparin chemistry to improve dental osteogenesis associated with implants

In this study, we designed a hybrid Ti by heparin modifying the Ti surface followed by Growth/differentiation factor-5 (GDF-5) loading. After that, products were characterized by physicochemical analysis. Quantitative analysis of functionalized groups was also confirmed. The release behavior of GDF-5 grafted samples was confirmed for up to 21days. The surface modification process was found to be successful and to effectively immobilize GDF-5 and provide for its sustained release behavior. As an in vitro test, GDF-5 loaded Ti showed significantly enhanced osteogenic differentiation with increased calcium deposition under nontoxic conditions against periodontal ligament stem cells (PDLSc). Furthermore, an in vivo result showed that GDF-5 loaded Ti had a significant influence on new bone formation in a rabbit model. These results clearly confirmed that our strategy may suggest a useful paradigm by inducing osseo-integration as a means to remodeling and healing of bone defects for restorative procedures in dentistry.

Vascular Endothelial Growth Factor (VEGF) in Human Tooth Germ Center

Many oncogenis and tumour suppressor genes found inside normal and pathological cells are fundamental for the processes of development, proliferation and tissue differentiation. The purpose of our study is to show the presence and a possible relationship of the VEGF protein during different phases of the development of human dental germ centers. After cephalometric investigation in 8 orthodontic patients with a mean age of 13 years, (4 females and 4 males), hyperdivergence of the third molars were extracted. The 40 surgical samples were tested with monoclonal human anti-VEGFs antibodies carrying out a semi-quantitative analysis to look for a positive reaction. Reaction for anti-VEGF antibodies was detected in normal embryological tissues and in microvessels near odontogenic cells. During different phases of embryologic development of the dental bud our search showed intracytoplasmatic positive immunoreactions both in the ameloblastic and odontoblastic cells. Additionally, a positive reaction was observed for the VEGF protein in the cells of the stellate reticulum and in those endothelial tissue surrounding the microvessels in all the samples examined.

Recombinant human bone morphogenetic protein-9 potently induces osteogenic differentiation of human periodontal ligament fibroblasts

To accomplish effective periodontal regeneration for periodontal defects, several regenerative methods using growth and differentiation factors, including bone morphogenetic proteins (BMPs), have been developed. Bone morphogenetic protein-9 exhibits the most potent osteogenic activity of this growth factor family. However, it is unclear whether exogenous BMP-9 can induce osteogenic differentiation in human periodontal ligament (PDL) fibroblasts. Here, we examined the effects of recombinant human (rh) BMP-9 on osteoblastic differentiation in human PDL fibroblasts in vitro, compared with rhBMP-2. Recombinant human BMP-9 potently induced alkaline phosphatase (ALP) activity, mineralization, and increased expression of runt-related transcription factor-2/core binding factor alpha 1 (RUNX2/CBFA1), osterix, inhibitor of DNA binding/differentiation-1 (ID1), osteopontin, and bone sialoprotein genes, compared with rhBMP-2. The levels of rhBMP-9-induced osterix and ALP mRNA were significantly reduced in activin receptor-like kinase-1 and -2 small interfering RNA (siRNA)-transfected human PDL fibroblasts. Recombinant human BMP-9-induced ALP activity was not inhibited by noggin, in contrast to rhBMP-2 induced ALP activity, which was. Phosphorylation of SMAD1/5/8 in human PDL fibroblasts was induced by addition of rhBMP-9. Recombinant human BMP-9-induced ALP activity was suppressed by SB203580, SP600125, and U0126, which are inhibitors of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase 1/2 (ERK1/2), respectively. Our data suggest that rhBMP-9 is a potent inducer of the differentiation of human PDL fibroblasts into osteoblast-like cells and that this may be mediated by the SMAD and mitogen-activated protein kinase (p38, ERK1/2, and JNK) pathways.

Photo-cured hyaluronic acid-based hydrogels containing growth and differentiation factor 5 (GDF-5) for bone tissue regeneration

In this study we describe the generation and influences on in vitro and in vivo osteogenesis of photo-cured hyaluronic acid (HA) hydrogels loaded with growth and differentiation factor 5 (GDF-5). Prior to loading GDF-5, we characterized the release profiles from these hydrogels and tested their respective cell viability, differentiation and in vivo bone regeneration. The results from this testing indicated that GDF-5 was observed to release in a sustained manner from the HA hydrogels I-III. MTT and Live/Dead assays showed that the HA hydrogels I-III have good biocompatibility for use as scaffolds for bone tissue regeneration. In vitro cell tests showed a higher level of MC3T3-E1 cell proliferation and differentiation on HA hydrogels I-III than on HA hydrogel 0. Moreover, in vivo animal tests showed that the HA hydrogels I and III had a significant improvement on osteogenesis. Overall, our results suggest that the HA-based hydrogel is a good biomaterial to deliver osteogenic differentiation factors such as GDF-5, and GDF-5 can be useful as an effective alternative to aid new bone formation.

The effect of a bioactive collagen membrane releasing PDGF or GDF-5 on bone regeneration

Regenerative procedures using barrier membrane technology are presently well established in periodontal/endodontic surgery. The objective of this study was to compare the subsequent effects of the released platelet-derived growth factor (PDGF) and growth/differentiation factor 5 (GDF-5) from collagen membranes (CMs) on bone regeneration in vitro and in vivo. In vitro studies were conducted using MC3T3-E1 mouse preosteoblasts cultured with or without factors. Cell viability, cell proliferation, alkaline phosphatase (ALP) activity and bone marker gene expression were then measured. In vivo studies were conducted by placing CMs with low or high dose PDGF or GDF-5 in rat mandibular defects. At 4 weeks after surgery new bone formation was measured using μCT and histological analysis. The results of in vitro studies showed that CM/GDF-5 significantly increased ALP and cell proliferation activities without cytotoxicity in MC3T3-E1 cells when compared to CM/PDGF or CM alone. Gene expression analysis revealed that Runx2 and Osteocalcin were significantly increased in CM/GDF-5 compared to CM/PDGF or control. Quantitative and qualitative μCT and histological analysis for new bone formation revealed that although CM/PDGF significantly enhanced bone regeneration compared to CM alone or control, CM/GDF-5 significantly accelerated bone regeneration to an even greater extent than CM/PDGF. The results also showed that GDF-5 induced new bone formation in a dose-dependent manner. These results suggest that this strategy, using a CM carrying GDF-5, might lead to an improvement in the current clinical treatment of bone defects for periodontal and implant therapy.

GDFs promote tenogenic characteristics on human periodontal ligament-derived cells in culture at late passages

Tendon/ligament injures are leading disabilities worldwide. The periodontal ligament (PDL) connects teeth to bone, and is comparable to a tendon/ligament-to-bone insertion. PDL-derived cells (PDLCs) express both osteo/cementogenesis and teno/ligamentogenesis genes. However, an efficient method to induce a tenogenic differentiation of PDLCs has not been thoroughly examined. Therefore, this study tested if growth/differentiation factors (GDFs) enhanced tenogenic characteristics of human PDLCs, as a potential cell source for tendon/ligament engineering. Results demonstrated recombinant GDF-5/GDF-7 inhibited alkaline phosphatase (ALP) activity of PDLCs from passage 3 to 6, while GDF-5 enhanced ALP in dental pulp-derived cells and mesenchymal stem cells. GDF-5 (particularly at 10 ng/ml concentration) induced high expression of both early (scleraxis) and mature (tenomodulin, aggrecan, collagen3) tenogenic genes in P4-6 PDLCs, while inhibiting expression of specific transcription-factors for osteogenic, chondrogenic and adipogenic differentiation. Exogenous GDFs might lead PDLCs being expanded in culture during several passages to highly useful cell source for tendon/ligament engineering.

Growth and differentiation factor-5 regulates the growth and differentiation of human dental pulp cells

INTRODUCTION

Growth and differentiation factor-5 (GDF-5) is a multifunctional protein that regulates the development and repair in many tissues. The purpose of this study was to investigate whether GDF-5 may influence the proliferation, differentiation, and collagen turnover of human dental pulp cells.

METHODS

Human dental pulp cells were treated with different concentrations of GDF-5 (0-500 ng/mL). Morphology of pulp cells was observed under a microscope. Cell proliferation was evaluated by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Immunofluorescent assay was used to observe the percentages of cell mitosis. Collagen content was measured by Sircol collagen assay. Tissue inhibitor of metalloproteinase-1 level in the culture medium was measured with enzyme-linked immunosorbent assay and Western blotting. Cell differentiation was evaluated by alkaline phosphatase (ALP) staining and ALP enzyme activity assay.

RESULTS

After exposure of dental pulp cells to various concentrations of GDF-5, cell number was up-regulated significantly in dose-dependent manner. GDF-5 also stimulated mitosis of dental pulp cells as indicated by an increased percentage of binucleated cells from 28% to 35%-45%. GDF-5 did not affect the collagen content and tissue inhibitor of metalloproteinase-1 level of pulp cells. GDF-5 decreased the ALP activity of pulp cells as analyzed by ALP staining and enzyme activity assay, with 14%-44% of inhibition.

CONCLUSIONS

GDF-5 revealed mitogenic and proliferative activity to dental pulp cells. GDF-5 showed inhibitory effect on ALP activity but little effect on the collagen turnover. These events are crucial in specific stages of dental pulp repair and regeneration. GDF-5 may be potentially used for tissue engineering of pulp-dentin complex.

Protein and peptide-based therapeutics in periodontal regeneration

Protein and peptide-based therapeutics provide a unique strategy for controlling highly specific and complex biologic actions that cannot be accomplished by simple devices or chemical compounds. This article reviews some of the key characteristics and summarizes the clinical effectiveness of protein and peptide-based therapeutics targeting periodontal regeneration.

EVIDENCE ACQUISITION

A literature search was conducted of randomized clinical trials and systematic reviews evaluating protein and peptide-based therapeutics for the regeneration of periodontal tissues of at least 6 months duration. Data sources included PubMed and Embase electronic databases, hand-searched journals, and the ClinicalTrials.gov registry.

EVIDENCE SYNTHESIS

Commercially marketed protein and peptide-based therapeutics for periodontal regeneration provide gains in clinical attachment level and bone formation that are comparable or superior to other regenerative approaches. Results from several clinical trials indicate that protein and peptide-based therapies can accelerate repair and regeneration when compared with other treatments and that improvements in clinical parameters continue beyond 12 months. Protein and peptide-based therapies also exhibit the capacity to increase the predictability of treatment outcomes.

CONCLUSIONS

Clinical and histologic studies support the effectiveness of protein- and peptide-based therapeutics for periodontal regeneration. Emerging evidence suggests that the delivery devices/scaffolds play a critical role in determining the effectiveness of this class of therapeutics.

Epigenetic marks define the lineage and differentiation potential of two distinct neural crest-derived intermediate odontogenic progenitor populations

Epigenetic mechanisms, such as histone modifications, play an active role in the differentiation and lineage commitment of mesenchymal stem cells. In the present study, epigenetic states and differentiation profiles of two odontogenic neural crest-derived intermediate progenitor populations were compared: dental pulp (DP) and dental follicle (DF). ChIP on chip assays revealed substantial H3K27me3-mediated repression of odontoblast lineage genes DSPP and dentin matrix protein 1 (DMP1) in DF cells, but not in DP cells. Mineralization inductive conditions caused steep increases of mineralization and patterning gene expression levels in DP cells when compared to DF cells. In contrast, mineralization induction resulted in a highly dynamic histone modification response in DF cells, while there was only a subdued effect in DP cells. Both DF and DP progenitors featured H3K4me3-active marks on the promoters of early mineralization genes RUNX2, MSX2, and DLX5, while OSX, IBSP, and BGLAP promoters were enriched for H3K9me3 or H3K27me3. Compared to DF cells, DP cells expressed higher levels of three pluripotency-associated genes, OCT4, NANOG, and SOX2. Finally, gene ontology comparison of bivalent marks unique for DP and DF cells highlighted cell-cell attachment genes in DP cells and neurogenesis genes in DF cells. In conclusion, the present study indicates that the DF intermediate odontogenic neural crest lineage is distinguished from its DP counterpart by epigenetic repression of DSPP and DMP1 genes and through dynamic histone enrichment responses to mineralization induction. Findings presented here highlight the crucial role of epigenetic regulatory mechanisms in the terminal differentiation of odontogenic neural crest lineages.

Alveolar ridge augmentation using implants coated with recombinant human growth/differentiation factor -5 (rhGDF-5). Radiographic observations

OBJECTIVES

Application of growth factors onto dental implant surfaces is being considered to support local bone formation. Bone morphogenetic protein-2 (BMP-2) and BMP-7 have been shown to support local bone formation, but are also associated with adverse events including seroma formation, extensive bone remodeling, and implant displacement captured in the radiographic evaluation. This report presents mineralized tissue formation and associated adverse events following implantation of recombinant human growth/differentiation factor-5 (rhGDF-5) coated onto a purpose-designed titanium porous-oxide implant surface.

MATERIAL AND METHODS

Twelve young adult Labrador dogs were used. Three 10-mm titanium implants/jaw quadrant were placed 5 mm into the alveolar ridge in the posterior mandible following surgical extraction of the premolar teeth and reduction of the alveolar ridge. Six animals received implants coated with rhGDF-5 at 30 or 60 μg/implant in contralateral jaw quadrants. Six animals received implants coated with rhGDF-5 at 120 μg/implant or uncoated implants (sham-surgery control) using the same split-mouth design. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants. Radiographic recordings were made immediately postsurgery (baseline), and at week 4 and 8 (end of study). Two masked examiners performed the analysis using computer enhanced radiographic images.

RESULTS

rhGDF-5 coated implants displayed mineralized tissue formation significantly exceeding that of the sham-surgery control in a dose-dependent order. The greatest increase was observed for implants coated with rhGDF-5 at 60 μg and 120 μg amounting to approximately 2.2 mm for both groups at 8 weeks. Importantly, none of the implants showed evidence of peri-implant bone remodeling, implant displacement, or seroma formation. The newly formed mineralized tissues assumed characteristics of the resident bone.

CONCLUSIONS

rhGDF-5 coated onto a titanium porous-oxide implant surface exhibits a dose-dependent potential to stimulate local mineralized tissue formation. Application of rhGDF-5 appears safe as it is associated with limited, if any, adverse events.

Cholesteryl group- and acryloyl group-bearing pullulan nanogel to deliver BMP2 and FGF18 for bone tissue engineering

To create a drug delivery system that allows the controlled release of proteins, such as growth factors, over a long-term period, cholesteryl group- and acryloyl group-bearing pullulan (CHPOA) nanogels were aggregated to form fast-degradable hydrogels (CHPOA/hydrogels) by cross-linking with thiol-bearing polyethylene glycol. The gold standard of clinical bone reconstruction therapy with a physiologically active material is treatment with recombinant human bone morphogenetic protein 2 (BMP2); however, this approach has limitations, such as inflammation, poor cost-efficiency, and varying interindividual susceptibility. In this study, two distinct growth factors, BMP2 and recombinant human fibroblast growth factor 18 (FGF18), were applied to a critical-size skull bone defect for bone repair by the CHPOA/hydrogel system. The CHPOA-FGF18/hydrogel displayed identical results to the control CHPOA-PBS/hydrogel, and the CHPOA-BMP2/hydrogel treatment imperfectly induced bone repair. By contrast, the CHPOA-FGF18 + BMP2/hydrogel treatment strongly enhanced and stabilized the BMP2-dependent bone repair, inducing osteoprogenitor cell infiltration inside and around the hydrogel. This report indicates that the CHPOA/hydrogel system can successfully deliver two different proteins to the bone defect to induce effective bone repair. The combination of the CHPOA/hydrogel system with the growth factors FGF18 and BMP2 might be a step towards efficient bone tissue engineering.

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

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

A phase IIa randomized controlled pilot study evaluating the safety and clinical outcomes following the use of rhGDF-5/β-TCP in regenerative periodontal therapy

To present the safety profile, the early healing phase and the clinical outcomes at 24 weeks following treatment of human intrabony defects with open flap debridement (OFD) alone or with OFD and rhGDF-5 adsorbed onto a particulate β-tricalcium phosphate (β-TCP) carrier. Twenty chronic periodontitis patients, each with at least one tooth exhibiting a probing depth ≥6 mm and an associated intrabony defect ≥4 mm entered the study. Ten subjects (one defect/patient) were randomized to receive OFD alone (control) and ten subjects OFD combined with rhGDF-5/β-TCP. Blood samples were collected at screening, and at weeks 2 and 24 to evaluate routine hematology and clinical chemistry, rhGDF-5 plasma levels, and antirhGDF-5 antibody formation. Plaque and gingival indices, bleeding on probing, probing depth, clinical attachment level, and radiographs were recorded pre- and 24 weeks postsurgery. Comparable safety profiles were found in the two treatment groups. Neither antirhGDF-5 antibody formation nor relevant rhGDF-5 plasma levels were detected in any patient. At 6 months, treatment with OFD + rhGDF-5/β-TCP resulted in higher but statistically not significant PD reduction (3.7 ± 1.2 vs. 3.1 ± 1.8 mm; p = 0.26) and CAL gain (3.2 ± 1.7 vs. 1.7 ± 2.2 mm; p = 0.14) compared to OFD alone. In the tested concentration, the use of rhGDF-5/β-TCP appeared to be safe and the material possesses a sound biological rationale. Thus, further adequately powered, randomized controlled clinical trials are warranted to confirm the clinical relevance of this new approach in regenerative periodontal therapy. rhGDF-5/β-TCP may represent a promising new techology in regenerative periodontal therapy.

Implications of cultured periodontal ligament cells for the clinical and experimental setting: a review

The periodontal ligament (PDL) is a key contributor to the process of regeneration of the periodontium. The heterogeneous nature of the PDL tissue, its development during early adulthood, and the different conditions to which the PDL tissue is exposed to in vivo impart on the PDL unique characteristics that may be of consequence during its cultivation in vitro. Several factors affecting the in vivo setting influence the behaviour of PDL fibroblasts in culture. The purpose of this review is to address distinct factors that influence the behaviour of PDL fibroblasts in culture -in vivo-in vitro transitions, cell identification/isolation markers, primary PDL cultures and cell lines, tooth-specific factors, and donor-specific factors. Based on the reviewed studies, the authors recommendations include the use of several identification markers to confirm cell identity, use of primary cultures at early passage to maintain unique PDL heterogeneic characteristics, and noting donor conditions such as age, systemic health status, and tooth health status. Continued efforts will expand our understanding of the in vitro and in vivo behaviour of cells, with the goal of orchestrating optimal periodontal regeneration. This understanding will lead to improved evidence-based rationales for more individualized and predictable periodontal regenerative therapies.

bmp2b and bmp4 are dispensable for zebrafish tooth development

Bone morphogenetic protein (Bmp) signaling has been shown to play important roles in tooth development at virtually all stages from initiation to hard tissue formation. The specific ligands involved in these processes have not been directly tested by loss-of-function experiments, however. We used morpholino antisense oligonucleotides and mutant analysis in the zebrafish to reduce or eliminate the function of bmp2b and bmp4, two ligands known to be expressed in zebrafish teeth and whose mammalian orthologs are thought to play important roles in tooth development. Surprisingly, we found that elimination of function of these two genes singly and in combination did not prevent the formation of mature, attached teeth. The mostly likely explanation for this result is functional redundancy with other Bmp ligands, which may differ between the zebrafish and the mouse.

The progressive ankylosis protein regulates cementum apposition and extracellular matrix composition

BACKGROUND/AIMS

Tooth root cementum is sensitive to modulation of inorganic pyrophosphate (PP(i)), an inhibitor of hydroxyapatite precipitation. Factors increasing PP(i) include progressive ankylosis protein (ANK) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) while tissue nonspecific alkaline phosphatase hydrolyzes PP(i). Studies here aimed to define the role of ANK in root and cementum by analyzing tooth development in Ank knock-out (KO) mice versus wild type.

MATERIALS AND METHODS

Periodontal development in KO versus control mice was analyzed by histology, histomorphometry, immunohistochemistry, in situ hybridization, electron microscopy, and nanoindentation. Cementoblast cultures were used in vitro to provide mechanistic underpinnings for PP(i) modulation of cell function.

RESULTS

Over the course of root development, Ank KO cervical cementum became 8- to 12-fold thicker than control cervical cementum. Periodontal ligament width was maintained and other dentoalveolar tissues, including apical cementum, were unaltered. Cervical cementum uncharacteristically included numerous cells, from rapid cementogenesis. Ank KO increased osteopontin and dentin matrix protein 1 gene and protein expression, and markedly increased NPP1 protein expression in cementoblasts but not in other cell types. Conditional ablation of Ank in joints and periodontia confirmed a local role for ANK in cementogenesis. In vitro studies employing cementoblasts indicated that Ank and Enpp1 mRNA levels increased in step with mineral nodule formation, supporting a role for these factors in regulation of cementum matrix mineralization.

CONCLUSION

ANK, by modulating local PP(i), controls cervical cementum apposition and extracellular matrix. Loss of ANK created a local environment conducive to rapid cementogenesis; therefore, approaches modulating PP(i) in periodontal tissues have potential to promote cementum regeneration.

Evaluation of an injectable rhGDF-5/PLGA construct for minimally invasive periodontal regenerative procedures: a histological study in the dog

AIM

To evaluate the injectability, biocompatibility, safety, and periodontal wound healing/regeneration following application of a novel bioresorbable recombinant human growth/differentiation factor-5 (rhGDF-5)/poly(lactic-co-glycolic acid) (PLGA) construct.

MATERIAL AND METHODS

Periodontal pockets (3 x 6 mm, width x depth) were surgically created over the buccal roots of the second and fourth mandibular pre-molars in eight adult Hound Labrador mongrel dogs. Surgeries including injection of the rhGDF-5/PLGA construct into the pockets were sequenced that four animals provided 2-/4-week and four animals 6-/8-week observations of sites receiving rhGDF-5/PLGA or serving as sham-surgery control.

RESULTS

The rhGDF-5/PLGA construct was easy to prepare and apply. Approximately 0.2 ml (93 microg rhGDF-5)/tooth was used. Clinical and radiographic healing was exemplary without adverse events. Healing was characterized by a non-specific connective tissue attachment, acellular/cellular cementum, periodontal ligament (PDL), bone regeneration, and a junctional epithelium. PLGA fragments were observed in 4/7, 2/8, and 1/8 sites at 2, 4, and 6 weeks, respectively. Associated inflammatory reactions exhibited no limiting effect on periodontal wound healing/regeneration. Root resorption/ankylosis was not observed. Bone formation showed apparent increased maturity (lamellar bone) at 6 weeks in sites receiving rhGDF-5/PLGA compared with the control. Both protocols exhibited significant increases in PDL, cementum, and bone regeneration over time, without significant differences between treatments. In time, PDL and cementum regeneration was twofold greater for the control at 4 weeks (p=0.04) while increased bone formation was observed at sites receiving rhGDF-5/PLGA (p<0.01).

CONCLUSIONS

In conclusion, the rhGDF-5/PLGA construct appears to be a safe technology for injectable, ease-of-use application of rhGDF-5-stimulated periodontal wound healing/regeneration. Additional work to optimize the polymer carrier and rhGDF-5 release kinetics/dose might be required before evaluating the efficacy of this technology in clinical settings using minimally invasive approaches.

Mechanism of active eruption of molars in adolescent rats

The mechanism of active eruption of molars was examined in 36 male adolescent Wistar rats. Histological, histochemical [tetracycline (TC) labelling and alkaline phosphatase (ALP) activity], and immunohistochemical [transforming growth factor (TGF)-β1, -β2, and -β3] investigations were conducted of the rat molar areas. Real-time reverse transcription-polymerase chain reaction (RT-PCR) for mRNA of TGF-β was performed on the periodontal ligament (PDL) dissected out by laser capture microdissection. TC labelling lines showed that a considerable amount of bone formation occurred in the alveolar crest region, apical region, and intraradicular septum, indicating that the maxillary molars had moved downward. However, the periodontal fibres revealed a regular arrangement (alveolar crest, horizontal and oblique fibres) during the experimental period. This suggests that new formation of alveolar crest fibres and rearrangement of the periodontal fibres occurred in the PDL. ALP activity was intense on the bone surface and in the PDL. TGF-β1 was also detected in osteoblasts and fibroblasts but less so in cementoblasts. Real-time RT-PCR also demonstrated significant expression of mRNA of TGF-β1 in the PDL, indicating that TGF-β1 was involved in active eruption. These results suggest that active eruption occurs in adolescent rats and can be managed by TGF-β1.

Growth/differentiation factor-5 significantly enhances periodontal wound healing/regeneration compared with platelet-derived growth factor-BB in dogs

OBJECTIVE

Recombinant human growth/differentiation factor-5 (rhGDF-5) in a particulate beta-tricalcium phosphate (beta-TCP) carrier is being evaluated to support periodontal regeneration. The objective of this study was to evaluate periodontal wound healing/regeneration following an established clinical (benchmark) protocol including surgical implantation of rhGDF-5/beta-TCP in comparison with that following implantation of recombinant human platelet-derived growth factor-BB (rhPDGF) combined with a particulate beta-TCP biomaterial using an established canine defect model.

MATERIALS AND METHODS

Bilateral, 4 x 5 mm (width x depth), one-wall, critical-size, intrabony periodontal defects were surgically created at the mandibular second and fourth pre-molar teeth in five adult Beagle dogs. Defect sites were randomized to receive rhGDF-5/beta-TCP or the rhPDGF construct followed by wound closure for primary intention healing. The animals were sacrificed following an 8-week healing interval for histological and histometric examination.

RESULTS

Clinical healing was generally uneventful. Sites receiving rhGDF-5/beta-TCP exhibited a significantly enhanced cementum formation compared with sites receiving the rhPDGF construct, averaging (+/-SD) 4.49+/-0.48 versus 2.72+/-0.91 mm (p<0.001). Similarly, bone regeneration height and area were significantly enhanced at sites receiving rhGDF-5/beta-TCP versus that of the rhPDGF construct averaging, 3.08+/-0.74 versus 1.29+/-0.78 mm (p<0.001) and 6.03+/-1.28 versus 2.98+/-2.61 mm(2) (p<0.01), respectively. Cementum regeneration included cellular/acellular mixed (extrinsic/intrinsic) fibre cementum at sites receiving rhGDF-5/beta-TCP; sites receiving the rhPDGF/beta-TCP showed a pre-dominantly acellular cementum. Newly formed cementum generally extended above the adjoining alveolar bone. Both protocols displayed beta-TCP residues apparently undergoing resorption. Application of both materials appears safe, as they were associated with limited, if any, adverse events.

CONCLUSION

rhGDF-5/beta-TCP shows a significant potential to support/accelerate periodontal wound healing/regeneration. Application of rhGDF-5/beta-TCP appears safe and should be further evaluated in human clinical trials.

Alveolar ridge augmentation using implants coated with recombinant human growth/differentiation factor-5: histologic observations

OBJECTIVES

In vitro and in vivo preclinical studies suggest that growth/differentiation factor-5 (GDF-5) may induce local bone formation. The objective of this study was to evaluate the potential of recombinant human GDF-5 (rhGDF-5) coated onto an oral implant with a purpose-designed titanium porous oxide surface to stimulate local bone formation including osseointegration and vertical augmentation of the alveolar ridge.

MATERIALS AND METHODS

Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in 12 young adult Hound Labrador mongrel dogs. Six animals received implants coated with 30 or 60 microg rhGDF-5, and six animals received implants coated with 120 microg rhGDF-5 or left uncoated (control). Treatments were alternated between jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at weeks 3, 4, 7, and 8 post-surgery when they were euthanized for histologic evaluation.

RESULTS

The clinical examination showed no noteworthy differences between implants coated with rhGDF-5. The cover screw and implant body were visible/palpable through the alveolar mucosa for both rhGDF-5-coated and control implants. There was a small increase in induced bone height for implants coated with rhGDF-5 compared with the control, induced bone height averaging (+/-SD) 1.6+/-0.6 mm for implants coated with 120 microg rhGDF-5 versus 1.2+/-0.5, 1.2+/-0.6, and 0.6+/-0.2 mm for implants coated with 60 microg rhGDF-5, 30 microg rhGDF-5, or left uncoated, respectively (p<0.05). Bone formation was predominant at the lingual aspect of the implants. Narrow yellow and orange fluorescent markers throughout the newly formed bone indicate relatively slow new bone formation within 3-4 weeks. Implants coated with rhGDF-5 displayed limited peri-implant bone remodelling in the resident bone; the 120 microg dose exhibiting more advanced remodelling than the 60 and 30 microg doses. All treatment groups exhibited clinically relevant osseointegration.

CONCLUSIONS

rhGDF-5-coated oral implants display a dose-dependent osteoinductive and/or osteoconductive effect, bone formation apparently benefiting from local factors. Application of rhGDF-5 appears to be safe as it is associated with limited, if any, adverse effects.

Periodontal wound healing/regeneration following the application of rhGDF-5 in a beta-TCP/PLGA carrier in critical-size supra-alveolar periodontal defects in dogs

AIM

The objective of this study was to evaluate the effect of a novel recombinant human GDF-5 (rhGDF-5) construct intended for onlay and inlay indications on periodontal wound healing/regeneration.

METHODS

Contralateral, surgically created, critical-size, 6-mm, supra-alveolar periodontal defects in five adult Hound Labrador mongrel dogs received rhGDF-5 coated onto beta-tricalcium phosphate (beta-TCP) particles and immersed in a bioresorbable poly(lactic-co-glycolic acid) (PLGA) composite or the beta-TCP/PLGA carrier alone (control). The rhGDF-5 and control constructs were moulded around the teeth and allowed to set. The gingival flaps were then advanced; flap margins were adapted 3-4 mm coronal to the teeth and sutured. The animals were euthanized at 8 weeks post-surgery when block biopsies were collected for histometric analysis.

RESULTS

Healing was generally uneventful. A few sites exhibited minor exposures. Three control sites and one rhGDF-5 site (in separate animals) experienced more extensive wound dehiscencies. The rhGDF-5 and control constructs were easy to apply and exhibited adequate structural integrity to support the mucoperiosteal flaps in this challenging onlay model. Limited residual beta-TCP particles were observed at 8 weeks for both rhGDF-5/beta-TCP/PLGA and beta-TCP/PLGA control sites. The rhGDF-5/beta-TCP/PLGA sites showed significantly greater cementum (2.34 +/- 0.44 versus 1.13 +/- 0.25 mm, p=0.02) and bone (2.92 +/- 0.66 versus 1.21 +/- 0.30 mm, p=0.02) formation compared with the carrier control. Limited ankylosis was observed in four of five rhGDF-5/beta-TCP/PLGA sites but not in control sites.

CONCLUSIONS

Within the limitations of this study, the results suggest that rhGDF-5 is a promising candidate technology in support of periodontal wound healing/regeneration. Carrier and rhGDF-5 dose optimization are necessary before further advancement of the technology towards clinical evaluation.

Differential effects of growth differentiation factor-5 on porcine dental papilla- and follicle-derived cells

In this study, the effect of growth differentiation factor-5 (GDF-5) on the growth and differentiation of porcine dental papilla- and follicle-derived cells was investigated. Furthermore, the effect was compared with that of BMP-2. Recombinant mouse GDF-5 (rmGDF-5) enhanced alkaline phosphatase (ALP) activity in dental papilla-derived cells in a dose-dependent manner, while ALP activity in dental follicle-derived cells was reduced. In rmGDF-5 stimulated dental papilla-derived cells, the expressions of odontoblast-marker genes were up-regulated. Conversely, recombinant human BMP-2 (rhBMP-2) enhanced ALP activity dose-dependently in both dental papilla- and follicle-derived cells. When combined, GDF-5 did not further enhance BMP-2-induced ALP activities. Rather, GDF-5 reduced BMP-2-induced ALP activities in both dental papilla- and follicle-derived cells. This suggests that affinity of GDF-5 to the shared receptors may be higher than that of BMP-2 in both cell types. These observations indicate that GDF-5 regulates differentiation of both dental papilla and follicle during odontogenesis, co-operatively with other growth factors such as BMP-2.

Periodontal regeneration: focus on growth and differentiation factors

Several growth and differentiation factors have shown potential as therapeutic agents to support periodontal wound healing/regeneration, although optimal dosage, release kinetics, and suitable delivery systems are still unknown. Experimental variables, including delivery systems, dose, and the common use of poorly characterized preclinical models, make it difficult to discern the genuine efficacy of each of these factors. Only a few growth and differentiation factors have reached clinical evaluation. It appears that well-defined discriminating preclinical models followed by well-designed clinical trials are needed to further investigate the true potential of these and other candidate factors. Thus, current research is focused on finding relevant growth and differentiation factors, optimal dosages, and the best approaches for delivery to develop clinically meaningful therapies in patient-centered settings.

The KK-Periome database for transcripts of periodontal ligament development

The periodontal ligament (PDL) is a strong connective tissue that surrounds the tooth root, absorbs occlusal forces, and functions as a sense organ. PDL originated from dental follicle (DF), which possessed mesenchymal progenitors in the developing tooth germ. However, as specific marker genes for PDL and DF are currently unavailable, the molecular mechanisms of PDL development are yet to be clarified. To facilitate the identification of such genes, we have previously established a transcriptome database of the human PDL (the KK-Periome database) and screened for specific genes expressed during PDL development. Initial screening of the database revealed two marker genes for distinguishing DF and PDL. The KK-Periome database thus appears to offer a useful resource for investigating genes involved in PDL development.

Influence of ADAM28 on biological characteristics of human dental follicle cells

OBJECTIVES

The aim of this study was to investigate the effects of a disintegrin and metalloproteinase 28 (ADAM28) on the biological characteristics of human dental follicle cells (HDFCs) and possible action mechanism.

METHODS

Eukaryotic expression plasmid containing ADAM28 coding region and ADAM28 antisense oligodeoxynucleotides (AS-ODN) with FITC labelling were constructed and synthesised by gene clone and recombination. Then we respectively transfected them into HDFCs by Lipofectamine 2000 system and detected their effects on proliferation, differentiation and apoptosis of HDFCs by MTT assay, cell cycle detection, ALP activity and Annexin V-FITC/PI analysis. Finally we observed the effects of ADAM28 AS-ODN on HDFCs expressing extracellular matrix (ECM) proteins by immunocytochemical staining.

RESULTS

ADAM28 eukaryotic plasmid was constructed and identified successfully, and could be correctly translated and expressed in HDFCs, furthermore overexpression of ADAM28 promoted the HDFCs proliferation and inhibited specific differentiation of HDFCs, while inhibition of ADAM28 exerted the opposite effects and induced apoptosis. Moreover ADAM28 could significantly inhibit the secretion of OPN and type III collagen of HDFCs.

CONCLUSIONS

ADAM28 might actively participate in the network regulation which associates HDFCs proliferation, differentiation, apoptosis with matrix mineralisation during tooth development by interacting with multiple signal molecules.

Development of an injectable composite as a carrier for growth factor-enhanced periodontal regeneration

AIM

Biomaterials are often applied in periodontal therapy; however, not always well adapted for tissue regeneration. The objective of this study was to evaluate the physico-chemical properties and biocompatibility of an injectable, in situ setting composite for growth factor-enhanced periodontal regeneration.

MATERIAL AND METHODS

The composite constitutes bioresorbable poly(lactic-co-glycolic acid) (PLGA) and additives forming in situ a matrix designed as a carrier for recombinant human growth/differentiation factor-5 (rhGDF-5). In vitro characterization included the porosity, biointeraction, biodegradation, injectability, and biological activity of released rhGDF-5. Biocompatibility was compared with granular beta-tricalcium phosphate and an absorbable collagen sponge using a canine periodontal defect model.

RESULTS

The PLGA composite showed a highly porous (500-1000 mum) space-providing structure. It effectively induced coagulation exhibiting an intimate interaction with the fibrin clot. The biphasic biodegradation was complete within 4 weeks. The composite was conveniently injectable (90.4+/-3.6 N) for ease of use. It exhibited a sustained rhGDF-5 release over 4 weeks (40.8%) after initial burst (3.4%) detected by ALP activity. Sites receiving the composite showed limited, if any, residuals and had no appreciable negative effect on periodontal wound healing. There were no noteworthy inflammatory lesions in sites receiving the PLGA composite.

CONCLUSION

Characteristics of the PLGA composite makes it an attractive matrix to support native wound healing and rhGDF-5-enhanced periodontal regeneration.

Estrogen receptor-related receptor-alpha (ERR-alpha) is dysregulated in inflammatory arthritis

OBJECTIVES

Subchondral bone loss is a characteristic feature of inflammatory arthritis. Recently, estrogen receptor-related receptor-alpha (ERR-alpha), an orphan nuclear receptor, has been found to be involved in activation of macrophages. We hypothesized that ERR-alpha which is expressed and also functional in articular chondrocytes, osteoblasts and osteoclasts, may be involved in rodent models of inflammatory arthritis.

METHODS

Erosive arthritis was induced in DBA/1 mice by injection of type II collagen in Freund's complete adjuvant. RNA was isolated from the bone and joints and expression of ERR-alpha and cartilage (GDF5 and Col2a1) and bone [bone sialoprotein (BSP) and osteocalcin (OCN)] markers was analysed by semi-quantitative PCR.

RESULTS

We report for the first time that the expression of ERR-alpha is dysregulated in bones and joints in a mouse model of inflammatory arthritis. Specifically, we show that ERR-alpha expression is down-regulated early in bone and later in joints of mice with type II CIA. Concomitantly, temporal changes were observed in GDF-5 and Col2a1 expression in joints following both initial injection and booster injection of type II collagen. Similarly, down-regulation of ERR-alpha mRNA expression in subchondral bone in mice with induced joint inflammation was also paralleled by down-regulation of markers of bone formation (BSP, OCN).

CONCLUSIONS

These data suggest that dysregulation of ERR-alpha expression may precede and contribute to the destruction of cartilage and bone accompanying inflammatory arthritis.

Osteogenic-related gene expression profiles of human dental follicle cells induced by dexamethasone

AIM

Human dental follicle cells (hDFC) have the ability to differentiate into mineralized tissue-forming cells during root and periodontal development or osteogenic induction in vitro. The present study aimed to validate the osteogenic induction of hDFC by dexamethasone (DEX) and to explore the changes of related genes responsible for the osteogenic differentiation process.

METHODS

Passage-cultured hDFC were induced by DEX and analyzed for mineralization activity by morphological observation, alkaline phosphatase (ALP) activity, and alizarin red S staining. GEArray Q series human osteogenesis gene array was used to describe large-scale gene expression in treated hDFC compared to the control group. Quantitative real-time RT-PCR was performed to confirm the microarray data by analyzing the expression of 7 critical transcripts.

RESULTS

Osteogenic differentiation of hDFC was confirmed by morphological change, elevated ALP activity and calcified nodules. In 96 genes investigated through the microarray analysis, 20 genes were upregulated and 8 genes were downregulated more than 2-fold. The results of the real-time RT-PCR correlated with the microarray analysis. The expression of the transforming growth factor-beta superfamily showed varying degrees of increase, and fibroblast growth factors exhibited a differential changing trend of expression. The expression of most types of collagen genes representative of extracellular matrixes increased under DEX treatment while small mothers against decapentaplegic 6 and 7 expressions significantly decreased.

CONCLUSION

Our results demonstrated that hDFC displayed osteoblastic features in both phenotypic and genotypic traits induced by DEX in vitro.

Genomic screening identifies novel linkages and provides further evidence for a role of MYH9 in nonsyndromic cleft lip and palate

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common birth anomaly that requires prolonged multidisciplinary rehabilitation. Although variation in several genes has been identified as contributing to NSCLP, most of the genetic susceptibility loci have yet to be defined. To identify additional contributory genes, a high-throughput genomic scan was performed using the Illumina Linkage IVb Panel platform. We genotyped 6008 SNPs in nine non-Hispanic white NSCLP multiplex families and a single large African-American NSCLP multiplex family. Fourteen chromosomal regions were identified with LOD>1.5, including six regions not previously reported. Analysis of the data from the African-American and non-Hispanic white families revealed two likely chromosomal regions: 8q21.3-24.12 and 22q12.2-12.3 with LOD scores of 2.98 and 2.66, respectively. On the basis of biological function, syndecan 2 (SDC2) and growth differentiation factor 6 (GDF6) in 8q21.3-24.12 and myosin heavy-chain 9, non-muscle (MYH9) in 22q12.2-12.3 were selected as candidate genes. Association analyses from these genes yielded marginally significant P-values for SNPs in SDC2 and GDF6 (0.01<or=P<0.05). Evidence for an altered transmission was found for four MYH9 SNPs (P<0.01). SNP rs1002246 exhibited altered transmission by all analytic methods. However, analysis of two SNP MYH9 haplotypes did not identify a single high-risk haplotype. Our results confirm a previous report that 8q21.3-24.12 may harbor a clefting gene and identify 22q12.2-12.3 as a new candidate region that contains MYH9. Most importantly, we confirm the previous report of an association with MYH9.

Injectable growth/differentiation factor-5-recombinant human collagen composite induces endochondral ossification via Sry-related HMG box 9 (Sox9)expression and angiogenesis in murine calvariae

BACKGROUND AND OBJECTIVE

The types of collagens available today as biomaterials are purified from animal tissues. A major growing concern, however, is their safety, since there are risks of viral and prion contamination and of unknown and potentially zoonotic infectious diseases. The present study aimed to assess, using immunohistochemistry, the effects of recombinant human growth/differentiation factor-5 (rhGDF-5) combined with recombinant human collagen I (rhCI) on bone formation in murine calvariae.

MATERIAL AND METHODS

Composite rhGDF-5-rhCI or rhCI alone was injected subcutaneously into murine calvariae. After 3, 7 or 14 days, tissues were examined radiologically, histologically and immunohistochemically. The production of vascular endothelial growth factor (VEGF) by primary osteoblasts, periosteal cells and connective tissue fibroblasts isolated enzymatically from neonatal murine calvariae was also assessed.

RESULTS

A protrusion was observed on the calvariae at the site injected with rhGDF-5/rhCI composite. Its mineral density was shown to be different from that of the existing bone by two-dimensional microcomputed tomography. Type II collagen-positive staining was restricted to newly formed tissues. Thus, the newly formed tissues seemed to be bone- and cartilage-like tissues. A number of vessels with positively stained cells for Von Willebrand factor were detected in the newly formed tissues. The rhGDF-5 enhanced VEGF production in cultured connective tissue fibroblasts. Sry-related HMG box 9 (Sox9)-positive cells were detected in the hypertrophic periosteum, and penetrated into the newly formed tissues.

CONCLUSIONS

These results suggest that rhCI seems to allow the release of rhGDF-5 and that rhGDF-5-rhCI composite induces endochondral ossification via Sox9 expression and angiogenesis in murine calvariae.

Lateral ridge augmentation using particulated or block bone substitutes biocoated with rhGDF-5 and rhBMP-2: an immunohistochemical study in dogs

OBJECTIVES

The aim of the present study was to immunohistochemically evaluate lateral ridge augmentation using a particulated (BOG) or block (BOB) natural bone mineral biocoated with rhGDF-5 and rhBMP-2 in dogs.

MATERIALS AND METHODS

Three standardized box-shaped defects were surgically created at the buccal aspect of the alveolar ridge in each quadrant of eight beagle dogs. After 2 months of healing, the chronic-type defects were randomly allocated in a split-mouth design to either (i) BOG or (ii) BOB biocoated with (a) rhGDF-5 or (b) rhBMP-2, respectively. Uncoated grafts served as controls. After 3 and 8 weeks, dissected blocks were prepared for immunohistochemical [osteocalcin (OC)] and histomorphometrical analysis [e.g. area (mm(2)) of new bone fill (BF), newly formed mineralized (MT) and non-mineralized tissue (NMT)].

RESULTS

rhBMP-2 biocoated BOG revealed significantly highest BF and MT values at 3 (upper and lower jaws - UJ/LJ - compared with BOG) and 8 weeks (UJ - compared with rhGDF-5). Biocoating of BOB using both rhGDF-5 and rhBMP-2 resulted in significantly increased MT values at 8 weeks (UJ/LJ - compared with BOB). In all groups, NMT adjacent to BOG and BOB scaffolds revealed pronounced signs of an OC antigen reactivity.

CONCLUSIONS

Within the limits of the present study, it was concluded that both rhGDF-5 and rhBMP-2 have shown efficacy; however, their bone regenerative effect was markedly influenced by the carrier.