Bone morphogenetic protein-2 stimulates cell recruitment and cementogenesis during early wound healing

BMP Signaling Pathway in Dentin Development and Diseases

BMP signaling plays an important role in dentin development. BMPs and antagonists regulate odontoblast differentiation and downstream gene expression via canonical Smad and non-canonical Smad signaling pathways. The interaction of BMPs with their receptors leads to the formation of complexes and the transduction of signals to the canonical Smad signaling pathway (for example, BMP ligands, receptors, and Smads) and the non-canonical Smad signaling pathway (for example, MAPKs, p38, Erk, JNK, and PI3K/Akt) to regulate dental mesenchymal stem cell/progenitor proliferation and differentiation during dentin development and homeostasis. Both the canonical Smad and non-canonical Smad signaling pathways converge at transcription factors, such as Dlx3, Osx, Runx2, and others, to promote the differentiation of dental pulp mesenchymal cells into odontoblasts and downregulated gene expressions, such as those of DSPP and DMP1. Dysregulated BMP signaling causes a number of tooth disorders in humans. Mutation or knockout of BMP signaling-associated genes in mice results in dentin defects which enable a better understanding of the BMP signaling networks underlying odontoblast differentiation and dentin formation. This review summarizes the recent advances in our understanding of BMP signaling in odontoblast differentiation and dentin formation. It includes discussion of the expression of BMPs, their receptors, and the implicated downstream genes during dentinogenesis. In addition, the structures of BMPs, BMP receptors, antagonists, and dysregulation of BMP signaling pathways associated with dentin defects are described.

Age-related osteogenesis on lateral force application to rat incisor – Part II: Bony recession and cortical remodeling

Objective:

The aim of this study is to analyze the age-related changes in the bony recession and cortical bone remodeling induced by lateral orthodontic tooth movement, using a three-dimensional micro-computed tomography (CT) analysis.

Material and Methods:

A total of 40 male Sprague-Dawley rats were divided into two distinct age groups (young, 10 weeks and adult, 52 weeks). Double-helical springs exerting 40 g of force were applied to central incisors to analysis of changes in lateral cortical bone and tooth movement with age and time. The young and adult rats were divided into four subgroups, T0 (0 week), T1 (1 week), T2 (2 weeks), and T3 (3 weeks), depending on the period of wearing the appliance. Micro-CT image was taken on each dissected pre-maxilla specimen. In each subgroup, distance between the center of teeth, suture width, tooth displacement, bony recession, and bone volume was evaluated.

Results:

The changes in the distance between the center of teeth and the suture width were significantly greater in the young group. However, the change in the tooth displacement showed no significant difference between groups. In the young group, bony recession of outer cortical layer was observed at T1 (P < 0.05), but the amount of recession gradually decreased at T2 and T3. In contrast, in the adult group, bony recession increased gradually over observation period (P < 0.05). The bone volume decreased at T1 (P < 0.05), but recovered at T2 and T3 in both groups.

Conclusion:

The compensatory bone formation occurs in the pressure side of cortical bone more significantly in the young group than in the adult according to the lateral displacement of incisor in rats. The reduced bone reaction in the adult is considered a limiting factor of the excessive tooth movement in the compromised treatment of skeletal malocclusion.

Regeneration of rat periodontium by cementum protein 1-derived peptide

BACKGROUND AND OBJECTIVE

Cementum protein 1 (CEMP1) has the capacity to promote differentiation of periodontal ligament (PDL) cells toward a cementoblastic phenotype in vitro and bone regeneration in vivo. In this study, we tested the capabilities of a synthetic cementum protein 1-derived peptide, MGTSSTDSQQAGHRRCSTSN (CEMP1-p1), to promote regeneration of periodontal structures in a periodontal fenestration defect in rats.

MATERIAL AND METHODS

Fenestration defects were created using an extra-oral approach in the buccal aspect of the mandibular first molar roots. Eighteen male Wistar rats were divided into three groups. Two controls (defects non-treated or defects treated with a gelatin matrix scaffold [GMS] only) and the experimental group treated with 5 µg/dose of CEMP1-p1 embedded in GMS. After 28 days, the animals were sacrificed, and the mandibles processed for histopathological examination. Expression of cementum proteins, cementum attachment protein (CAP), CEMP1, integrin binding sialoprotein (IBSP), and osteocalcin (OCN), was assessed using immunofluorescence. The formation of new cementum, bone, and PDL fibers were compared between control and experimental groups.

RESULTS

The histological analysis revealed that the control group without any treatment new cementum or oriented PDL fibers were not observed. However, the presence of newly bone was detected. In the control group treated with GMS, new cementum formation was not detectable, the PDL fibers were oriented parallel to the longitudinal root axis, and new bone formation was observed. The experimental group showed deposit of acellular extrinsic fiber cementum (AEFC) in a lamellae-like feature with inserted Sharpey's fibers, formation of cellular mixed stratified cementum (CMSC) with the presence of cementocytes, and newly formed bone close to the cementum-enamel junction. Cementoblast cells adjacent to new cementum expressed CAP, CEMP1, IBSP, and OCN.

CONCLUSION

These studies show that CEMP1-p1 promotes the formation of AEFC, CMSC, new PDL with Sharpey's fibers inserted in cementum and bone, thus providing strong evidence that the synthetic peptide CEMP1-p1 promotes periodontal regeneration in a rat fenestration model.

2,3,5,4'-Tetrahydroxystilbene-2-O-β-d-glucoside promotes the effects of dental pulp stem cells on rebuilding periodontal tissues in experimental periodontal defects

BACKGROUND

This study aimed to investigate the regenerative effects of 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucoside (THSG)-treated human dental pulp stem cells (DPSC) on the healing of experimental periodontal defects in rats.

METHODS

The maxillary first molars of 30 male Sprague-Dawley rats were extracted, and after healing, bilateral periodontal defects were surgically created mesially in second molars. The defects were treated with Matrigel (as control), DPSC, or DPSC + THSG. After 2 weeks, the healed defects were evaluated using microcomputed tomography and through histological and immunohistochemical analyses.

RESULTS

In the microcomputed tomography analysis, more new bone formation in the DPSC and DPSC + THSG groups was observed compared with the control group. The periodontal bone supporting ratio in site with DPSC + THSG was significantly higher than that in DPSC. Histologically, an enhanced new bone formation and more significant periodontal attachment were observed in the DPSC + THSG group. The expression levels of proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), and osteopontin (OPN) in the DPSC + THSG group were significantly greater than those in other groups.

CONCLUSIONS

THSG-revolutionized DPSCs significantly shortened the regenerative period of periodontal defects by enhancing the cell recruitment and possibly the angiogenesis in rat models, which illustrate the critical implications for a clinical application and provide a novel tactic for periodontitis treatment.

Regenerative potential of cultured gingival fibroblasts in treatment of periodontal intrabony defects (randomized clinical and biochemical trial)

BACKGROUND

Defective cellular elements constitute an important challenge to achieve predictable periodontal regeneration. In an attempt to improve the cellularity of periodontal defects, gingival fibroblasts were implanted without their associated extracellular elements in periodontal defects to expose them to periodontal tissue mediators. In order to investigate the regenerative potential of gingival fibroblasts translocated into periodontal defects, the present study was designed to clinically and biochemically investigate the use of gingival fibroblasts (GF) and their associated mesenchymal stem cells (GMSC) in the treatment of intrabony periodontal defects.

METHODS

A total of 20 subjects were randomly divided into two groups (n = 20). Group I: ten patients were included with ten intrabony periodontal defects that received β-calcium triphosphate (β-TCP) followed by collagen membrane defect coverage, while group II: (10 patients) ten periodontal defects received cultured gingival fibroblasts (GF) on the β-TCP scaffold and covered by a collagen membrane. The clinical evaluation was carried out at the beginning and at 6 months. Gingival crevicular fluid (GCF) samples were collected directly from the test sites for the quantitative measurement of PDGF-BB and BMP-2 using the ELISA kit at 1, 7, 14, and 21 days after surgery.

RESULTS

Group II reported a significantly greater reduction in vertical pocket depth (VPD) and CAL gain compared with group I after 6 months. Radiographic bone gain was statistically higher in group II compared with group I. A significantly higher concentration of PDGF-BB was observed in group II on days 1, 3, and 7 compared with group I.

CONCLUSIONS

Translocation of gingival fibroblasts from gingival tissue to periodontal defects could be a promising option that increases cellular elements with regeneration potential. The concept of total isolation of gingival fibroblasts using occlusive membranes must be re-evaluated.

Transplantation of Adipose-derived Cells for Periodontal Regeneration: A Systematic Review

This systematic review evaluated the transplantation of cells derived from adipose tissue for applications in dentistry. SCOPUS, PUBMED and LILACS databases were searched for in vitro studies and pre-clinical animal model studies using the keywords "ADIPOSE", "CELLS", and "PERIODONTAL", with the Boolean operator "AND". A total of 160 titles and abstracts were identified, and 29 publications met the inclusion criteria, 14 in vitro and 15 in vivo studies. In vitro studies demonstrated that adipose- derived cells stimulate neovascularization, have osteogenic and odontogenic potential; besides adhesion, proliferation and differentiation on probable cell carriers. Preclinical studies described improvement of bone and periodontal healing with the association of adipose-derived cells and the carrier materials tested: Platelet Rich Plasma, Fibrin, Collagen and Synthetic polymer. There is evidence from the current in vitro and in vivo data indicating that adipose-derived cells may contribute to bone and periodontal regeneration. The small quantity of studies and the large variation on study designs, from animal models, cell sources and defect morphology, did not favor a meta-analysis. Additional studies need to be conducted to investigate the regeneration variability and the mechanisms of cell participation in the processes. An overview of animal models, cell sources, and scaffolds, as well as new perspectives are provided for future bone and periodontal regeneration study designs.

Bioinspired trimodal macro/micro/nano-porous scaffolds loading rhBMP-2 for complete regeneration of critical size bone defect

Critical size bone defects raise great demands for efficient bone substitutes. Mimicking the hierarchical porous architecture and specific biological cues of natural bone has been considered as an effective strategy to facilitate bone regeneration. Herein, a trimodal macro/micro/nano-porous scaffold loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2) was developed. With mesoporous bioactive glass (MBG) as matrix, a trimodal MBG scaffold (TMS) with enhanced compressive strength (4.28 MPa, porosity of 80%) was prepared by a "viscosity controlling" and "homogeneous particle reinforcing" multi-template process. A 7.5 nm, 3D cubic (Im3m) mesoporous structure was tailored for a "size-matched entrapment" of rhBMP-2 to achieve sustained release and preserved bioactivity. RhBMP-2-loaded TMS (TMS/rhBMP-2) induced excellent cell attachment, ingrowth and osteogenesis in vitro. Further in vivo ectopic bone formation and orthotopic rabbit radius critical size defect results indicated that compared to the rhBMP-2-loaded bimodal macro/micro- and macro/nano-porous scaffolds, TMS/rhBMP-2 exhibited appealing bone regeneration capacity. Particularly, in critical size defect, complete bone reconstruction with rapid medullary cavity reunion and sclerotin maturity was observed on TMS/rhBMP-2. On the basis of these results, TMS/rhBMP-2 developed here represents a promising bone substitute for clinical application and the concepts proposed in this study might provide new thoughts on development of future orthopedic biomaterials.

STATEMENT OF SIGNIFICANCE

Limited self-regenerating capacity of human body makes the reconstruction of critical size bone defect a significant challenge. Current bone substitutes often exhibit undesirable therapeutic efficacy due to poor osteoconductivity or low osteoinductivity. Herein, TMS/rhBMP-2, an advanced mesoporous bioactive glass (MBG) scaffold with osteoconductive trimodal macro/micro/nano-porosity and osteoinductive rhBMP-2 delivery was developed. The preparative and mechanical problems of hierarchical MBG scaffold were solved without affecting its excellent biocompatibilities, and rhBMP-2 immobilization in sizematched mesopores was first explored. Combining structural and biological cues, TMS/rhBMP-2 achieved a complete regeneration with rapid medullary cavity reunion and sclerotin maturity in rabbit radius critical size defects. The design conceptions proposed in this study might provide new thoughts on development of future orthopedic biomaterials.

Dental pulp stem cells. Biology and use for periodontal tissue engineering

Inflammatory periodontal disease is a major cause of loss of tooth-supporting structures. Novel approaches for regeneration of periodontal apparatus is an area of intensive research. Periodontal tissue engineering implies the use of appropriate regenerative cells, delivered through a suitable scaffold, and guided through signaling molecules. Dental pulp stem cells have been used in an increasing number of studies in dental tissue engineering. Those cells show mesenchymal (stromal) stem cell-like properties including self-renewal and multilineage differentiation potentials, aside from their relative accessibility and pleasant handling properties. The purpose of this article is to review the biological principles of periodontal tissue engineering, along with the challenges facing the development of a consistent and clinically relevant tissue regeneration platform. This article includes an updated review on dental pulp stem cells and their applications in periodontal regeneration, in combination with different scaffolds and growth factors.

Impact of ellagic acid in bone formation after tooth extraction: an experimental study on diabetic rats

Objectives. To estimate the impact of ellagic acid (EA) towards healing tooth socket in diabetic animals, after tooth extraction. Methods. Twenty-four Sprague Dawley male rats weighing 250–300 g were selected for this study. All animals were intraperitoneally injected with 45 mg/kg (b.w.) of freshly prepared streptozotocin (STZ), to induce diabetic mellitus. Then, the animals were anesthetized, and the upper left central incisor was extracted and the whole extracted sockets were filled with Rosuvastatin (RSV). The rats were separated into three groups, comprising 8 rats each. The first group was considered as normal control group and orally treated with normal saline. The second group was regarded as diabetic control group and orally treated with normal saline, whereas the third group comprised diabetic rats, administrated with EA (50 mg/kg) orally. The maxilla tissue stained by eosin and hematoxylin (H&E) was used for histological examinations and immunohistochemical technique. Fibroblast growth factor (FGF-2) and alkaline phosphatase (ALP) were used to evaluate the healing process in the extracted tooth socket by immunohistochemistry test. Results. The reactions of immunohistochemistry for FGF-2 and ALP presented stronger expression, predominantly in EA treated diabetic rat, than the untreated diabetic rat. Conclusion. These findings suggest that the administration of EA combined with RSV may have accelerated the healing process of the tooth socket of diabetic rats, after tooth extraction.

Outcome of enamel matrix derivative treatment in the presence of chronic stress: histometric study in rats

BACKGROUND

Psychologic stress and clinical hypercortisolism have been related to direct effects on bone metabolism. However, there is a lack of information regarding the outcomes of regenerative approaches under the influence of chronic stress (CS). Enamel matrix derivative (EMD) has been used in periodontal regenerative procedures, resulting in improvement of clinical parameters. Thus, the aim of this histomorphometric study is to evaluate the healing of periodontal defects after treatment with EMD under the influence of CS in the rat model.

METHODS

Twenty Wistar rats were randomly assigned to two groups; G1: CS (restraint stress for 12 hours/day) (n = 10), and G2: not exposed to CS (n = 10). Fifteen days after initiation of CS, fenestration defects were created at the buccal aspect of the first mandibular molar of all animals from both groups. After the surgeries, the defects of each animal were randomly assigned to two subgroups: non-treated control and treated with EMD. The animals were euthanized 21 days later.

RESULTS

G1 showed less bone density (BD) compared to G2. EMD provided an increased defect fill (DF) in G1 and higher BD and new cementum formation (NCF) in both groups. The number of tartrate-resistant acid phosphatase-positive osteoclasts was significantly higher in G1 when compared to G2 and in EMD-treated sites of both groups.

CONCLUSIONS

CS may produce a significant detrimental effect on BD. EMD may provide greater DF compared to non-treated control in the presence of CS and increased BD and NCF in the presence or absence of CS.

Intermittent parathyroid hormone administration improves periodontal healing in rats

BACKGROUND

Intermittent administration of parathyroid hormone (PTH) promotes new bone formation in patients with osteoporosis and bone fractures. It was shown previously that PTH also reduces periodontitis-related bone loss. The aim of this study is to evaluate the effect of treatment with PTH on periodontal healing in rats.

METHODS

Fenestration defects were created at the buccal surface of the distal root of the mandibular first molars, and both periodontal ligament (PDL) and cementum were removed. Animals were then assigned to two groups (eight animals per group): group 1: control, placebo administration; and group 2: test, human PTH (hPTH) 1-34 administration at a concentration of 40 μg/kg. For both groups, the animals were injected every 2 days, and the animals were sacrificed at 14 and 21 days after surgery. Specimens were harvested and processed for routine decalcified histologic sections. The following parameters were assessed: 1) remaining bone defect extension (RBDE); 2) newly formed bone density (NFBD); 3) total callus area (TCA); 4) osteoclast number (ON) in the callus region; and 5) newly formed dental cementum-like tissue (NFC). Birefringence of root PDL reattachment was also evaluated.

RESULTS

Birefringence analysis showed root PDL reattachment for both groups 21 days after treatment. Intermittent hPTH 1-34 administration decreased RBDE (P <0.01) and increased NFBD (P <0.01), TCA (P <0.01), area of NFC (P <0.01), and ON in the callus region (P <0.01).

CONCLUSION

Within the limits of the present study, intermittent administration of hPTH 1-34 led to an enhanced periodontal healing process compared with non-treated animals.

Effect of autologous platelet-rich plasma on distraction osteogenesis in the mandible of rabbits: a morphologic and morphometric approach

Distraction osteogenesis of the jaw is a common surgical practice in the treatment of pediatric craniofacial deformities. Autologous platelet rich plasma (PRP) has been used to increase the healing potential of bones in humans during distraction osteogenesis. This article aims to study the morphometric and morphologic parameters resulting from the effect of PRP on bone healing after mandibular distraction in rabbits. Right mandibular distraction was performed in 12 rabbits divided equally into 2 groups. PRP and physiological saline were injected, according to a defined protocol, in the callus following distraction of the experimental and control groups respectively. The rabbits were sacrificed after a consolidation period of 45 days and the mandibles were surgically removed. Bone mineral density, radiographic analysis, mechanical properties and histological features of the lengthened bones were assessed using radiographic examination, dual X-ray absorptiometry, biomechanical testing and histology. Results showed that the regenerate bone density, the amount of trabeculation in addition to the bone mineral density and mineral content, as measured by absorptiometry, were better with PRP but not significantly different between groups. Two radiographs revealed a more consistent healing in the experimental mandibles compared with erratic outcomes in corresponding controls. Two of the latter could not be subjected to any mechanical testing because the mandibular parts, connected with fibrous tissue, were separated. Consequently, the biomechanical test depicted greater maximal loads in the experimental group. The histological studies exhibited more ossification and less connective tissue fibers in the experimental group. PRP accelerated healing of mandibles in rabbits following distraction and improved their biomechanical properties. These findings have significant clinical implications on reducing the period of consolidation of the mandibles which may not be immobilized like other bones for long periods of time.

Migration of human dental follicle cells in vitro

BACKGROUND AND OBJECTIVES

The objective of this study was to elucidate the effects of different growth factors on the migration of dental follicle cells (DFCs). DFCs are ectomesenchymally derived easily accessible multipotent stem cells. Cell migration is a crucial step in many biological processes but also for tissue engineering. Growth factors such as epidermal growth factor (EGF), bone morphogenetic protein-2 (BMP2) or transforming growth factor β1 (TGF-β1) can be used to modify the behavior of cells.

MATERIAL AND METHODS

We used different migration assays (gel spot assay, scratch assay, transwell assay) to evaluate the influence of EGF, BMP2 and TGF-β1 on the migration of DFCs. We investigated the expression of migration-related genes after growth factor stimulation using the PCR array human cell motility.

RESULTS

DFCs treated with BMP2 or TGF-β1 migrated faster than DFCs treated with EGF. Additionally, more migration-related genes are regulated after treatment with BMP2 or TGF-β1 than with EGF. TGF-β1 additionally functions as a chemoattractant for DFCs. Osteogenic differentiation markers were regulated after BMP2 treatment only.

CONCLUSION

Whereas the strong migration induced by BMP2 was accompanied by beginning osteogenic differentiation the strong migration induced by TGF-β1 was directional. EGF exhibited not only the weakest migration stimulation but also the weakest induction of differentiation into mineralizing cells.

Transplanted Human Bone Marrow Mesenchymal Stem Cells Seeded onto Peptide Hydrogel Decrease Alveolar Bone Loss

Alveolar bone loss can be caused by periodontitis or periodontal trauma. We have evaluated the effects of transplanted undifferentiated human mesenchymal stem cells (hMSCs) on alveolar bone reaction and periodontal ligament healing in an experimental periodontal wound model. The hMSCs seeded onto a self-assembling peptide hydrogel in combination with collagen sponge were implanted into the right mandible of 12 rats and followed for 1 (n=6) or 4 weeks (n=6) postoperatively. The other 12 sham-treated rats were used as controls. Histological and histomorphometrical methods were used to assess the periodontal tissue reaction. The alveolar bone volume density was significantly higher at 1 week after surgery, and the osteoclast number was significantly lower at both 1 week and 4 weeks postoperatively in the mandibles treated with hMSCs. The implanted cells were detected only at 1 week after surgery. In conclusion, transplanted hMSCs can contribute to alveolar bone preservation after a periodontal surgical trauma at least by decreasing local osteoclast number.

Translational research and therapeutic applications of stem cell transplantation in periodontal regenerative medicine

Stem cells have received a great deal of interest from the research community as potential therapeutic "tools" for a variety of chronic debilitating diseases that lack clinically effective therapies. Stem cells are also of interest for the regeneration of tooth-supporting tissues that have been lost to periodontal disease. Indeed, substantial data have demonstrated that the exogenous administration of stem cells or their derivatives in preclinical animal models of periodontal defects can restore damaged tissues to their original form and function. As we discuss here, however, considerable hurdles must be overcome before these findings can be responsibly translated to novel clinical therapies. Generally, the application of stem cells for periodontal therapy in clinics will not be realized until the best cell(s) to use, the optimal dose, and an effective mode of administration are identified. In particular, we need to better understand the mechanisms of action of stem cells after transplantation in the periodontium and to learn how to preciously control stem cell fates in the pathological environment around a tooth. From a translational perspective, we outline the challenges that may vary across preclinical models for the evaluation of stem cell therapy in situations that require periodontal reconstruction and the safety issues that are related to clinical applications of human stem cells. Although clinical trials that use autologous periodontal ligament stem cells have been approved and have already been initiated, proper consideration of the technical, safety, and regulatory concerns may facilitate, rather than inhibit, the clinical translation of new therapies.

Methods to validate tooth-supporting regenerative therapies

In humans, microbially induced inflammatory periodontal diseases are the primary initiators that disrupt the functional and structural integrity of the periodontium (i.e., the alveolar bone, the periodontal ligament, and the cementum). The reestablishment of its original structure, properties, and function constitutes a significant challenge in the development of new therapies to regenerate tooth-supporting defects. Preclinical models represent an important in vivo tool to critically evaluate and analyze the key aspects of novel regenerative therapies, including (1) safety, (2) effectiveness, (3) practicality, and (4) functional and structural stability over time. Therefore, these models provide foundational data that supports the clinical validation and the development of novel innovative regenerative periodontal technologies. Steps are provided on the use of the root fenestration animal model for the proper evaluation of periodontal outcome measures using the following parameters: descriptive histology, histomorphometry, immunostaining techniques, three-dimensional imaging, electron microscopy, gene expression analyses, and safety assessments. These methods will prepare investigators and assist them in identifying the key end points that can then be adapted to later stage human clinical trials.

Designing biomaterials for in situ periodontal tissue regeneration

The regeneration of periodontal tissue poses a significant challenge to biomaterial scientists, tissue engineers and periodontal clinicians. Recent advances in this field have shifted the focus from the attempt to recreate tissue replacements/constructs ex vivo to the development of biofunctionalized biomaterials that incorporate and release regulatory signals in a precise and near-physiological fashion to achieve in situ regeneration. The molecular and physical information coded within the biomaterials define a local biochemical and mechanical niche with complex and dynamic regulation that establishes key interactions with host endogenous cells and, hence, may help to unlock latent regenerative pathways in the body by instructing cell homing and regulating cell proliferation/differentiation. In the future, these innovative principles and biomaterial devices promise to have a profound impact on periodontal reconstructive therapy and are also likely to reconcile the clinical and commercial pressures on other tissue engineering endeavors.

A comparison between adipose tissue and dental pulp as sources of MSCs for tooth regeneration

In this study, several in vivo and in vitro comparisons were performed to test the possibility of using adipose-derived stem cells (ADSCs), a more convenient cell source than dental pulp stem cells (DPSCs), in tooth regeneration. Using an efficient, non-engineering implantation method, we first demonstrated that both implants of ADSCs and DPSCs were able to grow self-assembled new teeth in adult rabbit extraction sockets with high success rate. The stem cells were necessary because the implants grew no tooth without them. A stepwise comparison showed that the regenerated teeth from these two types of adult stem cells were living with nerves and vascular system and remarkably similar to a normal tooth in many details. Further strictly controlled, side-by-side comparisons between the two types of stem cells also showed that the expression patterns of gene markers and the broad differentiation potentials induced by specific methods in vitro were very similar. Although a few differences were found, they did not affect the tested tooth regeneration in vivo or differentiation in vitro. Furthermore, rabbit ADSCs had a higher growth rate and a better senescence resistance in culture. All these findings suggest that ADSCs, one of the richest adult stem cells in mammals, are very similar and useful as DPSCs for regenerative dentistry.

A review on endogenous regenerative technology in periodontal regenerative medicine

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

The Yin and Yang of bone morphogenetic proteins in cancer

Bone morphogenetic proteins (BMPs) were first studied as growth factors or morphogens of the transforming growth factor-beta superfamily. These growth molecules, originally associated with bone and cartilage development, are now known to play an important role in morphogenesis and homeostasis in many other tissues. More recently, significant contributions from BMPs, their receptors, and interacting molecules have been linked to carcinogenesis and tumor progression. On the other hand, BMPs can sometimes function as a tumor suppressor. Our report highlights these new roles in the pathogenesis of cancer that may suggest novel targets for therapeutic intervention.

The impact of cigarette smoke inhalation on the outcome of enamel matrix derivative treatment in rats: histometric analysis

BACKGROUND

Tobacco use is the most significant risk factor of periodontal disease. Clinical evidence has demonstrated that tobacco may negatively influence the results after surgical and non-surgical periodontal therapy. Enamel matrix derivative (EMD) have been used in periodontal regenerative procedures resulting in improvement of clinical parameters. The effect of EMD in the presence of tobacco compounds is unclear. Thus, the aim of the present study is to evaluate the impact of cigarette smoke inhalation (CSI) on the results of EMD treatment.

METHODS

Twenty-two Wistar rats were assigned to two groups: Group 1, CSI (n = 11); Group 2, non-exposed (n = 11). Thirty days after initiation of CSI, fenestration defects were created at the buccal aspect of the first mandibular molar. The study followed a split-mouth design. After the surgeries the defects were randomly assigned to two subgroups: non-treated control and treated with EMD. The animals were sacrificed 21 days later and the percentage of defect fill, density of newly formed bone, and new cementum formation were histometrically assessed. The number of osteoclasts was determined by tartrate-resistant acid phosphatase.

RESULTS

CSI was associated with less bone density compared to the non-exposed group. EMD provided an increased defect fill and new cementum formation in both groups. The number of tartrate-resistant acid phosphatase-positive osteoclasts was significantly higher in the CSI non-treated control group compared to the non-treated control of the non-exposed animals.

CONCLUSIONS

EMD may provide increased defect fill and cementum formation in the presence or absence of CSI. However, tobacco smoke produced a detrimental effect on bone healing when density of newly formed bone was considered.

BMPs: Options, indications, and effectiveness

Alteration of the bone healing process with bone morphogenetic proteins offers a new perspective in orthopaedic surgery in those adverse situations that necessitate bone grafting. BMPs have been demonstrated to be effective and safe for human application and have an efficacy comparable with that of autologous bone grafting. Nevertheless, clinical trials with level 1 evidence are still limited in their ability to extrapolate robust and safe clinical conclusions for the possible indications mentioned in this article. Future research should refine issues regarding the relative effectiveness of bone morphogenetic proteins, the interaction between bone morphogenetic protein subtypes, and their specific effect on various target cell populations.

Dental stem cells and their potential role in apexogenesis and apexification

Injury to an immature permanent tooth may result in cessation of dentine deposition and root maturation leaving an open root apex and thin dentinal walls that are prone to fracture. Endodontic treatment is often complicated and protracted with an uncertain prognosis frequently resulting in premature tooth loss. Postnatal stem cells, which are capable of self-renewal, proliferation and differentiation into multiple specialized cell lineages have been isolated and identified within the dental pulp, apical papilla and periodontal ligament. The ability of these cells to produce pulp-dentine and cementum-periodontal ligament complexes in vivo suggest potential applications involving stem cells, growth factors and scaffolds for apexification or apexogenesis. Similar protein expression amongst dental stem cells possibly implicates a common origin; however, the dominant cells to repopulate an open apex will be directed by local environmental cues. A greater understanding of the structure and function of cells within their environment is necessary to regulate and facilitate cellular differentiation along a certain developmental path with subsequent tissue regeneration. This review focuses on development of the apical tissues, dental stem cells and their possible involvement clinically in closing the open root apex. MEDLINE and EMBASE computer databases were searched up to January 2009. Abstracts of all potentially relevant articles were scanned and their contents identified before retrieval of full articles. A manual search of article reference lists as well as a forward search on selected authors of these articles was undertaken. It appears that dental stem cells have the potential for continued cell division and regeneration to replace dental tissues lost through trauma or disease. Clinical applications using these cells for apexogenesis and apexification will be dependent on a greater understanding of the environment at the immature root end and what stimulates dental stem cells to begin dividing and then express a certain phenotype.

Pre-clinical models for oral and periodontal reconstructive therapies

The development of new medical formulations (NMF) for reconstructive therapies has considerably improved the available treatment options for individuals requiring periodontal repair or oral implant rehabilitation. Progress in tissue engineering and regenerative medicine modalities strongly depends on validated pre-clinical research. Pre-clinical testing has contributed to the recent approval of NMF such as GEM 21S and INFUSE bone grafts for periodontal and oral regenerative therapies. However, the selection of a suitable pre-clinical model for evaluation of the safety and efficacy of a NMF remains a challenge. This review is designed to serve as a primer to choose the appropriate pre-clinical models for the evaluation of NMF in situations requiring periodontal or oral reconstruction. Here, we summarize commonly used pre-clinical models and provide examples of screening and functional studies of NMF that can be translated into clinical use.

Bone morphogenetic protein 4 is induced in hepatocellular carcinoma by hypoxia and promotes tumour progression

Striking similarities exist between molecular mechanisms driving embryonic liver development and progression of hepatocellular carcinoma (HCC). Bone morphogenetic proteins (BMPs), particularly BMP4, have been proposed to regulate embryonic hepatic development. BMP expression has been observed in neoplasia but the expression and biological role of BMP4 in human HCC are unknown. We found increased BMP4 mRNA and protein in HCC cell lines and tissue samples compared to primary human hepatocytes and corresponding non-tumourous tissue. Hypoxia further induced BMP4 expression in HCC cells, which was abolished by transfection of a dominant negative form of HIF-1 alpha (dnHIF-1 alpha). However, gel shift assays revealed only minor binding activity in nuclear extracts from (hypoxic) HCC cells to a putative hypoxia-response element in the BMP4 promoter. Sequence analysis of the BMP4 promoter revealed two Ets-1 binding sites, and Ets-1 activity was increased in HCC cells under hypoxic conditions. Transfection of dnHIF-1 alpha completely abrogated hypoxia-induced Ets-1 activity as well as BMP4 expression. Overexpression of Ets-1 markedly enhanced BMP4 promoter activity, while antisense Ets-1 almost completely abolished basal as well as hypoxia-induced BMP4 expression. These data demonstrate that Ets-1 activity contributes to baseline expression of the BMP4 gene and is the predominant mediator of the HIF-dependent BMP4 induction under hypoxic conditions. To determine the functional relevance of BMP4 expression, HCC cell lines were treated with antisense BMP4 constructs or siRNA against BMP4. BMP4 suppression resulted in a strong reduction of the migratory and invasive potential and anchorage-independent growth. Furthermore, tube formation assays indicated that BMP4 expressed by HCC cells promotes vasculogenesis. Our findings demonstrate that BMP4 is increased in HCC and promotes HCC progression. Therefore, BMP4 expression may have clinical relevance, and interfering with BMP4 signalling appears as an attractive therapeutic target for this highly aggressive tumour.

In vitro cellular responses to scaffolds containing two microencapulated growth factors

Growth factors play an important role in the complex cascade of tissue events in periodontal regeneration, although optimal methods of delivery remain to be identified. We hypothesize that multiple delivery of growth factors, particularly via a microparticle-containing scaffold, will enhance cellular events leading to periodontal regeneration. In this study, cellular responses of periodontal ligament fibroblasts (PDLFs) in scaffolds containing microparticles (MPs) loaded with either bone morphogenetic protein (BMP)-2, insulin-like growth factor (IGF)-1, or a mixture of both MPs were evaluated, and the dual-MP-containing scaffold exhibited the release of different proteins in a sustained and independent fashion. When PDLF-seeded scaffolds were cultured in a flow perfusion bioreactor, cell metabolism and proliferation of PDLFs were significantly increased within 3 days in all IGF-1-containing scaffolds compared with those in groups lacking IGF-1 and particulate delivery enhanced these effects between 3 and 7 days. The dual-MP-containing group showed the most positive results. Both the BMP-2-in-MP and IGF-1-in-MP groups showed greater effects of alkaline phosphatase activity, more osteocalcin and osteopontin production, and more calcium deposition compared with matched GF-adsorbed groups. All osteoblastic markers were at their highest in the dual-MP-containing group at all detected time points. The combined results suggest that our dual-MP-containing scaffold can be used as a cell vehicle to positively affect cell behavior, thus exhibiting the potential to be a candidate scaffold for future periodontal tissue engineering.

Periodontal ligament cell sheet promotes periodontal regeneration in athymic rats

AIM

The primary goal of periodontal treatment is regeneration of the periodontium. Current theories suggest that the periodontal ligament (PDL) cells have the capacity to participate in restoring connective and mineralized tissues, when appropriately triggered. We evaluated whether human PDL cell sheets could reconstruct periodontal tissue.

MATERIAL AND METHODS

To obtain the cell sheet, human PDL cells were cultured on temperature-responsive culture dishes with or without osteogenic differentiation medium. The cell sheets were transplanted on periodontal fenestration defects of immunodeficient rats. Forty rats were divided in two groups: in one group, cell sheets cultured with control medium were transplanted and in the other, cell sheets cultured with osteogenic differentiation medium were transplanted. The defects were analysed histologically and histomorphologically after healing.

RESULTS

Most of the experimental group exhibited a new cementum-like layer and new attachment of collagen fibres to the layer. Histomorphological analyses indicated significant periodontal regeneration. The control group revealed dense extracellular matrix and fibre formation, but an obvious cementum layer was not observed.

CONCLUSIONS

Transplanted PDL cell sheets cultured with osteogenic differentiation medium induced periodontal regeneration containing an obvious cementum layer and Sharpey's fibres. Thus, the method could be feasible as a new therapeutic approach for periodontal regeneration.

Regeneration of bone and periodontal ligament induced by recombinant amelogenin after periodontitis

Regeneration of mineralized tissues affected by chronic diseases comprises a major scientific and clinical challenge. Periodontitis, one such prevalent disease, involves destruction of the tooth-supporting tissues, alveolar bone, periodontal-ligament and cementum, often leading to tooth loss. In 1997, it became clear that, in addition to their function in enamel formation, the hydrophobic ectodermal enamel matrix proteins (EMPs) play a role in the regeneration of these periodontal tissues. The epithelial EMPs are a heterogeneous mixture of polypeptides encoded by several genes. It was not clear, however, which of these many EMPs induces the regeneration and what mechanisms are involved. Here we show that a single recombinant human amelogenin protein (rHAM⁺), induced in vivo regeneration of all tooth-supporting tissues after creation of experimental periodontitis in a dog model. To further understand the regeneration process, amelogenin expression was detected in normal and regenerating cells of the alveolar bone (osteocytes, osteoblasts and osteoclasts), periodontal ligament, cementum and in bone marrow stromal cells. Amelogenin expression was highest in areas of high bone turnover and activity. Further studies showed that during the first 2 weeks after application, rHAM⁺ induced, directly or indirectly, significant recruitment of mesenchymal progenitor cells, which later differentiated to form the regenerated periodontal tissues. The ability of a single protein to bring about regeneration of all periodontal tissues, in the correct spatio-temporal order, through recruitment of mesenchymal progenitor cells, could pave the way for development of new therapeutic devices for treatment of periodontal, bone and ligament diseases based on rHAM⁺.

Cementum-periodontal ligament complex regeneration using the cell sheet technique

BACKGROUND AND OBJECTIVE

In the present study we evaluated if a multilayered human periodontal ligament cell sheet could reconstruct the physiological architecture of a periodontal ligament-cementum complex.

MATERIAL AND METHODS

Human periodontal ligament cells were isolated and then cultured in dishes coated with a temperature-responsive polymer to allow cell detachment as a cell sheet. In the control group, human periodontal ligament cells were cultured in Dulbecco's modified Eagle's minimal essential medium containing 10% fetal bovine serum and 1% antibiotics. In the experimental group, human periodontal ligament cells were cultured in Dulbecco's modified Eagle's minimal essential medium and osteodifferentiation medium containing dexamethasone, ascorbic acid and beta-glycerophosphate. After 3 wk, scanning electron microscopy was carried out, in addition to staining for alkaline phosphatase activity and for calcium (using the Von Kossa stain). Then human periodontal ligament cell sheets were multilayered and placed onto dentin blocks. The constructs were transplanted subcutaneously into the back of immunodeficient rats. At 1 and 6 wk after transplantation, the animals were killed. Demineralized tissue sections were stained using hematoxylin and eosin, and Azan, and then analyzed.

RESULTS

After 3 wk of culture in osteodifferentiation medium, human periodontal ligament cells produced mineral-like nodules and also showed positive staining for alkaline phosphatase, calcium (Von Kossa) and mRNA expression of type I collagen. By contrast, in the control group only weak alkaline phosphatase staining was observed, the Von Kossa stain was negative and there was no mRNA expression of type I collagen. Six weeks after transplantation with human periodontal ligament cells cultured in osteodifferentiation medium, most of the dentin surfaces showed a newly immature cementum-like tissue formation and periodontal ligament with perpendicular orientation inserted into the newly deposited cementum-like tissue.

CONCLUSION

This study suggests that the multilayered temperature-responsive culture system can be used as a novel strategy for periodontal regeneration. The human periodontal ligament cell sheet technique may be applicable for regeneration of the clinical periodontal ligament-cementum complex.

Are statins associated with decreased tooth loss in chronic periodontitis?

AIM

To evaluate whether statin use was associated with decreased tooth loss among patients with chronic periodontitis.

MATERIAL AND METHODS

We evaluated administrative health plan data from 1996 to 2002 covering dental and periodontal treatment utilization, dental extractions, and prescription medication fills of 12,631 adults aged 48-64 in 2002. With tooth loss as the outcome, we evaluated a number of different patterns of statin prescription across time in multivariate generalized linear models.

RESULTS

Unadjusted, statin use was associated with increased tooth loss. After adjustment for potential confounders, there was no suggestion of either increased or decreased tooth loss associated with statin use.

CONCLUSIONS

Statin use was not associated with either a decreased or an increased risk of tooth loss.

Effect of Interleukin-1β on Transforming Growth Factor-Beta and Bone Morphogenetic Protein-2 Expression in Human Periodontal Ligament and Alveolar Bone Cells in Culture: Modulation by Avocado and Soybean Unsaponifiables

BACKGROUND

In periodontal disease, interleukin-1beta (IL-1beta) is responsible for the matrix breakdown through excessive production of degrading enzymes by periodontal ligament fibroblasts and osteoblasts. Transforming growth factor-beta (TGF-beta) plays an important role in tissue regeneration as one of the factors capable of counteracting IL-1beta effects. In this study, we investigated the in vitro effect of avocado and soya unsaponifiables (ASU) on the expression of TGF-beta1, TGF-beta2, and bone morphogenetic protein-2 (BMP-2) by human periodontal ligament (HPL) and human alveolar bone (HAB) cells in the presence of IL-1beta.

METHODS

HPL and HAB cells were incubated for 48 hours with ASU (10 microg/ml) in the presence or absence of IL-1beta (10 ng/ml). The steady-state levels of TGF-beta1, TGF-beta2, and BMP-2 mRNAs were determined by Northern blot or reverse transcription-polymerase chain reaction (RT-PCR). The amounts of TGF-beta1 and TGF-beta2 proteins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The data indicated that IL-1beta strongly decreases the expression of TGF-beta1 and TGF-beta2 by HPL cells. ASU were capable of opposing the cytokine effect. In HAB cells, TGF-beta1 and BMP-2 mRNA levels were downregulated by the cytokine. ASU were found to reverse the IL-1beta-inhibiting effect. In contrast, the cytokine stimulated the production of TGF-beta2 in alveolar bone cells, with no significant effect of ASU.

CONCLUSIONS

The results indicate that the IL-1beta-driven erosive effect in periodontitis could be enhanced by a decreased expression of members of the TGF-beta family. The ASU stimulation of TGF-beta1, TGF-beta2, and BMP-2 expression may explain their promoting effects in the treatment of periodontal disorders, at least partly. These findings support the hypothesis that ASU could exert a preventive action on the deleterious effects exerted by IL-1beta in periodontal diseases.

Preparation and biological characteristics of recombinant human bone morphogenetic protein-2-loaded dextran-co-gelatin hydrogel microspheres, in vitro and in vivo studies

Hydrogels are based on hydrophilic polymers which are cross-linked to prevent dissolution in water. Because hydrogels can contain large amounts of water, they are interesting devices for the delivery of protein drugs. In this contribution, biodegradable dextran-co-gelatin hydrogel microspheres (DG-MPs) are described which are based on physical interactions and are particularly suitable for the controlled delivery of pharmaceutically active proteins. The unique feature of this preparation system is that the hydrogel microsphere formation takes place in an all-aqueous solution, by which the use of organic solvents is avoided. We investigated the preparation and biological activities of recombinant human bone morphogenetic protein-2 (rhBMP2)-loaded dextran-co-gelatin hydrogel microspheres (rhBMP2-DG-MPs), which aimed to keep rhBMP2's biological activity and to achieve a long-term sustained release of rhBMP2. The microspheres' average diameter was about 20-40 microm and rhBMP2 release in vitro could be maintained for >10 days. Cytology studies showed that using rhBMP2-DG-MPs could promote the proliferation and osteoblastic differentiation of periodontal ligament cells better than using rhBMP2 aqueous solution. By a freeze-drying method, rhBMP2-DG-MPs could be adhered in chitosan membranes for guided tissue regeneration use, namely functionalized membranes. To evaluate bone regeneration induced by rhBMP2-DG-MPs, an animal experiment with canine class III furcation defects was adopted and the results indicated that using rhBMP2-DG-MPs incorporating scaffolds and functionalized membranes could gain more periodontal tissue regeneration than using scaffolds and general membranes soaked with concentrated rhBMP2 aqueous solution. Therefore, those studies demonstrate the potential of DG-MPs in the sustained delivery of low dosages of rhBMP2 to periodontal defects.

Marker of cemento-periodontal ligament junction associated with periodontal regeneration

OBJECTIVE

The purpose of this study was to identify factors promoting formation of the cemento-periodontal ligament junction.

BACKGROUND

Regeneration of the cemento-periodontal ligament junction is an important factor in recovery of the connective tissue attachment to the cementum and it is important to identify all specific substances that promote its formation. To clarify the substances involved in cemento-periodontal ligament junction formation, we produced a monoclonal antibody (mAb) to human cemento-periodontal ligament junction (designated as the anti-TAP mAb) and examined its immunostaining properties and reactive antigen.

METHODS

Hybridomas producing monoclonal antibody against human cemento-periodontal ligament junction antigens were established by fusing P3U1 mouse myeloma cells with spleen cells from BALB/c mice immunized with homogenized human cemento-periodontal ligament junction. The mAb, the anti-TAP mAb for cemento-periodontal ligament junction, was then isolated. The immunoglobulin class and light chain of the mAb were examined using an isotyping kit. Before immunostaining, antigen determination using an enzymatic method or heating was conducted. Human teeth, hard tissue-forming lesions, and animal tissues were immunostained by the anti-TAP mAb.

RESULTS

The anti-TAP mAb was positive in human cemento-periodontal ligament junction and predentin but negative in all other human and animal tissues examined. In the cemento-osseous lesions, the anti-TAP mAb was positive in the peripheral area of the cementum and cementum-like hard tissues and not in the bone and bone-like tissues. The anti-TAP mAb showed IgM (kappa) and recognized phosphoprotein.

CONCLUSION

The anti-TAP mAb is potentially useful for developing new agents promoting cementogenesis and periodontal regeneration.

Bone Morphogenic Proteins Are Overexpressed in Malignant Melanoma and Promote Cell Invasion and Migration

Malignant melanoma cells are known to have altered expression of growth factors compared with normal human melanocytes. These changes probably favor tumor growth and progression and influence the tumor environment. The induction of transforming growth factor β1 (TGF-β1), TGF-β2, and TGF-β3 expression in malignant melanoma has been reported before, whereas the expression of related bone morphogenic protein (BMP) molecules has not been analyzed in melanomas until now. Here, we show that BMP4 and BMP7 are up-regulated in nine melanoma cell lines, whereas BMP2 is overexpressed in only two of the analyzed cell lines. Immunohistochemistry of primary and metastatic melanoma also shows increased BMP4 and BMP7 expression compared with nevi. Promoter studies reveal that expression is controlled at the transcriptional level. The transcription factor Ets-1 was identified as a positive regulator for BMP4 expression. In order to determine the functional relevance of BMP expression in malignant melanoma, chordin-expressing cell clones and antisense BMP4 cell clones were generated. The clones in which BMP4 activity and expression are reduced show no changes in proliferation or in attachment-independent growth when compared with controls. However, a strong reduction of migratory and invasive properties was observed in these cells, suggesting that BMP4 promotes melanoma cell invasion and migration and therefore has an important role in the progression of malignant melanoma.