Bone gap healing in the dog using recombinant human bone morphogenetic protein-2

Poly(POG)n loaded with recombinant human bone morphogenetic protein-2 accelerates new bone formation in a critical-sized bone defect mouse model

Background

Delivery of bone morphogenetic protein-2 (BMP-2) via animal-derived absorbable collagen materials is used for the treatment of large bone defects. However, the administration of bovine proteins to humans is associated with the risk of zoonotic complications. We therefore examined the effect of combining BMP-2 with collagen-like peptides, poly(POG)n, in a critical-sized bone defect mouse model.

Methods

A 2-mm critical-sized bone defect was created in the femur of 9-week-old male C57/BL6J mice. Mice were randomly allocated into one of four treatment groups (n = 6 each): control (no treatment), poly(POG)n only, 0.2 μg, or 2.0 μg BMP-2 with poly(POG)n. New bone formation was monitored using soft X-ray radiographs, and bone formation at the bone defect site was examined using micro-computed tomography and histological examination at 4 weeks after surgery.

Results

Administration of 2.0 μg of BMP-2 with poly(POG)n promoted new bone formation and resulted in greater bone volume and bone mineral content than that observed in the control group and successfully achieved consolidation. In contrast, bone formation in all other groups was scarce.

Conclusions

Our findings suggest the potential of BMP-2 with poly(POG)n as a material, free from animal-derived collagen, for the treatment of large bone defects.

Quantifying Vascular Changes Surrounding Bone Regeneration in a Porcine Mandibular Defect Using Computed Tomography

Angiogenesis is a critical process essential for optimal bone healing. Several in vitro and in vivo systems have been previously used to elucidate some of the mechanisms involved in the process of angiogenesis, and at the same time, to test potential therapeutic agents and bioactive factors that play important roles in neovascularization. Computed tomography (CT) is a noninvasive imaging technique that has recently allowed investigators to obtain a diverse range of high-resolution, three-dimensional characterization of structures, such as bone formation within bony defects. Unfortunately, to date, angiogenesis evaluation relies primarily on histology, or ex vivo imaging and few studies have utilized CT to qualitatively and quantitatively study the vascular response during bone repair. In the current study a clinical CT-based technique was used to evaluate the effects of rhBMP-2 eluting graft treatment on soft tissue vascular architecture surrounding a large segmental bone defect model in the minipig mandible. The objective of this study was to demonstrate the efficacy of contrast-enhanced, clinical 64-slice CT technology in extracting quantitative metrics of vascular architecture over a 12-week period. The results of this study show that the presence of rhBMP-2 had a positive effect on vessel volume from 4 to 12 weeks, which was explained by a concurrent increase in vessel number, which was also significantly higher at 4 weeks for the rhBMP-2 treatment. More importantly, analysis of vessel architecture showed no changes throughout the duration of the study, indicating therapeutic safety. This study validates CT analysis as a relevant imaging method for quantitative and qualitative analysis of morphological characteristics of vascular tissue around a bone healing site. Also important, the study shows that CT technology can be used in large animal models and potentially be translated into clinical models for the development of improved methods to evaluate tissue healing and vascular adaptation processes over the course of therapy. This methodology has demonstrated sensitivity to tracking spatial and temporal changes in vascularization and has the potential to be applied to studying changes in other high-contrast tissues as well. Impact Statement Tissue engineering solutions depend on the surrounding tissue response to support regeneration. The inflammatory environment and surrounding vascular supply are critical to determining if therapies will survive, engraftment occurs, and native physiology is restored. This study for the first time evaluates the blood vessel network changes in surrounding soft tissue to a bone defect site in a large animal model, using clinically available computed tomography tools and model changes in vessel number, size, and architecture. While this study focuses on rhBMP2 delivery impacting surrounding vasculature, this validated method can be extended to studying the vascular network changes in other tissues as well.

New Bone Formation Induced by Injection of Native Reindeer Bone Morphogenetic Protein Extract

Background and Aims:

Bone morphogenetic proteins (BMPs) are usually administered with a solid framing material during open surgery. In some instances, percutaneous administration of injectable BMP would be preferable. We tested the new bone-forming activity of injectable native reindeer BMP extract in the Balb/C mouse thigh muscle pouch model.

Materials and Methods:

The injectable implants contained 6 mg of native reindeer BMP extract and either physiological saline (NaCl/BMP) or collagen (Gel/BMP). Corresponding implants without BMP served as controls. New bone formation was evaluated based on incorporation of Ca45 and radiographically three weeks after the injection into the mouse thigh muscles.

Results:

None of the injections without BMP were able to induce new bone visible in radiographs, whereas the injections with BMP induced new bone effectively. There were no significant differences in the area of new bone (p = 0.247) and its density (p = 0.739) between the NaCl/BMP and Gel/BMP groups. Ca-45 incorporation was multifold in the NaCl/BMP and Gel/BMP groups compared to the controls (p = 0.000). No significant differences in Ca-45 incorporation (p = 0.739) between the NaCl/BMP and Gel/BMP groups were observed.

Conclusion:

Our results suggest that BMP can be administered percutaneously, and that collagen and physiological saline are equally good carriers of injectable implants of native reindeer BMP.

Radiographic Assessment of Bone Formation Using rhBMP2 at Maxillary Periapical Surgical Defects: A Case Series

Periapical cysts are the most common inflammatory odontogenic cysts arising from untreated dental caries with pulp necrosis and periapical infection. The choice of treatment is often influenced by various factors like size, extension of the lesion, proximity to vital structures, systemic condition and compliance of the patient too. The treatment protocol for management of periapical cysts is still under discussion and options vary from conservative treatment by means of endodontic technique to surgical treatment like decompression or a marsupialisation or even to enucleation. Large bony defect secondary to periapical surgery compromising the tooth integrity often requires bone graft to enhance bone formation and thus restoring function at the earliest. The present case series included 10 patients who had established periapical pathology secondary to history of trauma on upper anterior teeth as well patients with history of carious teeth with an apparent failure in root canal therapy. All ten patients were treated with cyst enucleation and apiceotomy along with 1.4cc Recombinant Human Bone Morphogenetic Protein-2 soaked Absorbable Collagen Sponge implantation at surgical defect. Radiographs and clinical examinations were done upto 3 months to evaluate healing. Radiographic and clinical assessments revealed bone regeneration and restoration of the maxillary surgical defects in all 10 patients. No evidence of graft failure was noted. The Recombinant Human Bone Morphogenetic Protein-2 soaked Absorbable Collagen Sponge carrier is thus proved to be a viable option for the treatment of maxillary periapical surgical defects.

Osteodistraction of mandibles with a small bone defect at the planned osteotomy site: a histological pilot study in dogs

AIM

To develop a treatment plan for cases in which a bone defect is located on the osteotomy line of mandibular osteodistraction (DO).

SUBJECTS AND METHODS

Bilateral DO was performed in 17 Mongrel dogs. Prior to surgery, the 34 hemi-mandibles were randomly allocated to three groups: C (n = 10; a standard DO was performed), D - G (n = 12; a bone defect was created on the DO osteotomy line), and D + G (n = 12; the bone defect on the osteotomy line was grafted). After one week of latency, 8 days of distraction, and 4 weeks of consolidation the animals were sacrificed, and the newly formed bone were examined.

RESULTS

In group C, two zones of immature trabecular bone originating from host bone margins were separated by a central fibrous zone. In group D + G uniform new bone formation of the entire distraction gap was observed. In group D - G the distraction gap was mainly filled with fibrous tissue. The values for the newly formed bone volume and trabecular thickness were not significantly different between groups D + G and C, but were higher than values in group D - G (p < 0.05).

CONCLUSION

When a mandibular defect is located at the site of distraction osteotomy, DO can be performed simultaneous with bone grafting of the defect.

New bone formation around xenogenic dentin grafts to rabbit tibia marrow

PURPOSE

From traumatology, it is well known that dentoalveolar ankylosis results in osseous replacement and formation of new bone. This principle is used after decoronation for preservation of the height and width of the alveolar bone crest after trauma. Dentin possesses bone-forming properties and may possibly also be used as a bone augmentation material prior to implant placement. The aim of this study was to investigate whether xenogenic dentin particles inserted into the marrow space of rabbit tibia, a space where there is no solid bone tissue initially, would contribute to new bone formation.

MATERIALS AND METHODS

Dentin chips from human teeth were inserted into tibias of ten New Zealand rabbits. The tibial bones were processed for histology after 6 months, and new bone formation was quantified.

RESULTS

Bone formation was ranging from 0 to 86% on the dentin fragments, and there was minor inflammation. Bone formation was seen to a larger extent on dentin grafts located close to the native tibial bone wall. There was a significant correlation (r = -0.579, P < 0.001) between the amount of bone formation around the dentin graft and distance to the tibial cortical wall.

CONCLUSION

Dentin promotes new bone formation when located close to native cortical bone and may have a potential as a bone augmentation material.

rhBMP-2 not alendronate combined with HA-TCP biomaterial and distraction osteogenesis enhance bone formation

INTRODUCTION

The long treatment duration of distraction osteogenesis (DO) usually causes some complications such as re-fracture, non-union. We have previously demonstrated that the combined use of biomaterial with distraction osteogenesis technique can enhance bone formation and consolidation. This study further tested whether the use of biological agents such as rhBMP-2 or alendronate together with biomaterials in DO will further promote bone formation.

METHODS

A 1.0-cm tibial shaft was removed in the left tibia of 30 rabbits. The 1.0-cm defect gap was reduced to 0.5 cm and the remaining 0.5-cm defect gap was filled with 0.5-cm restorable hydroxyapatite/tri-calcium phosphates (HA/TCP) cylindrical block. The animals were divided into three groups with the following added on the HA/TCP block: Group A 50 μl of saline, Group B 75 μg rhBMP-2 in 50 μl of saline, Group C 250 μg alendronate in 50 μl saline. The tibia was then fixed with unilateral lengthener and lengthening started 7 days after at a rate of 1.0 mm/day for 5 days. All animals were terminated at day 37 following surgery. The excised bone specimens were subject to micro-CT, mechanical testing and histological examinations.

RESULTS

Bone mineral density and content were significantly higher in Groups A and B compared to Group C and the mechanical properties of the regenerates in Group B were highest. Micro-CT and histological examinations also confirmed that the regenerates in Group B had the most advanced bone formation, consolidation and remodeling comparing to other groups.

CONCLUSION

The combined use of rhBMP-2 with HA-TCP biomaterial in DO has significantly enhanced bone formation and consolidation than using the HA-TCP biomaterials alone, whereas the use of alendronate has inhibitory effects on bone formation.

Exogenous recombinant human BMP-2 has little initial effects on human osteoblastic cells cultured on collagen type I coated/noncoated hydroxyapatite ceramic granules

PURPOSE

Tissue engineering of bone entails the successful interplay between osteoinductive factors, osteogenic cells, their extracellular environment, and an osteoconductive biomaterial scaffold. Naturally produced ceramics, like hydroxyapatite (HA) calcified from red algae, are the most promising materials for use as scaffolds in this field. We hypothesized that extracellular matrix compartments and osteoinductive factors could further ameliorate the bioactivity of the scaffold.

MATERIALS AND METHODS

Osteosarcoma cells with proven osteogenic phenotype (SaOS-2) were cultured onto type I collagen coated (Coll I/HA) and noncollagen coated HA granules (NC/HA) gained from red algae (C GRAFT/Algipore). Cells grown on tissue culture polystyrene dishes (TCPS) were used as controls. Second, SaOS-2 cells cultured on Coll I/HA, NC/HA, and TCPS were treated with recombinant human bone morphogenetic protein-2 (rhBMP-2) in different concentrations (10, 100, and 500 ng/mL). Non rhBMP-2-treated cultures were used as controls. Cultures of both experiments were grown under osteogenic differentiation conditions and after 24, 48, and 72 hours assays for cell viability, apoptosis, alkaline phosphatase activity (ALP), and osteocalcin (OC) secretion were done.

RESULTS

Coating of HA granules with type I collagen showed higher cell viability in rhBMP-2-treated and nontreated cells. Supplementation of cultured cells with exogenous rhBMP-2 showed a dose-dependent effect only in the TCPS group. No alterations of the apoptotic rate within 1 investigation group were found. Addition of rhBMP-2 did not significantly alter the specific OC secretion of cells grown on Coll I/HA and TCPS.

CONCLUSION

These in vitro findings show that in the initial period of cultivation and up to 72 hours, the coating of HA granules with collagen type I had positive effects on cell viability and osteoblastic characteristics of osteoblastic cells. In contrast, the supplementation with exogenous rhBMP-2 shows no dose-dependent effects. The combination of collagen type I and exogenous rhBMP-2 did not ameliorate the bioactivity of hydroxyapatite calcified from red algae in the initial period of cultivation.

Reindeer BMP extract in the healing of critical-size bone defects in the radius of the rabbit

BACKGROUND

Native BMP extracts from reindeer effectively induce ectopic new bone formation in vivo, but their bone healing properties have not yet been evaluated. We investigated the effect of reindeer BMP extracts on the healing of long bone defects.

METHODS

The implants tested contained 5 mg or 10 mg of unsterilized BMP extract from reindeer and 10 mg of gamma-sterilized BMP extract administered with collagen carrier (Lyostypt, B. Braun, Germany). 70 micro g of rhBMP-2 with collagen carrier (InductOs; Wyeth Europa) served as positive control, and collagen implants (Lyostypt) and untreated defects served as negative controls. New Zealand White rabbits with 1.5 cm of critical-size radius bone defects were used, with 8 weeks of follow-up.

RESULTS

Radiographic analysis showed bone formation (BF) to be higher in all groups containing BMPs than in the untreated controls. BF was also higher in the rhBMP-2 group, and marginally higher in the group treated with 10 mg of unsterilized reindeer BMP extract (p = 0.06) as compared to the collagen controls. Bone union (BU) was better in the unsterilized BMP extract groups and rhBMP-2 group than in the untreated controls. BU was also better in the implants with 10 mg of unsterilized reindeer BMP extract and rhBMP-2 than in the collagen-treated implants. The mean area of new bone at the site of the defect proved to be higher in all implants containing BMP than in the untreated defects. It was also higher in the groups with 10 mg of unsterilized reindeer BMP extract and rhBMP-2 than in the collagen-treated controls. Mechanical tests showed torsional stiffness of the bones to be higher in the group with 10 mg of unsterilized BMP extract than in the collagen group. The mean cross-sectional bone area measured by pQCT densitometry was higher in the rhBMP-2 group than in the collagen group. The mean bone density at the defect area was higher in the group with 10 mg of unsterilized BMP than in the rhBMP-2 group.

INTERPRETATION

We conclude that both reindeer BMP extract and rhBMP-2 induced improved healing of the rabbit radius bone defects at the doses used. Gamma sterilization of reindeer BMP extract reduced osteoinductivity slightly, but not significantly.

The critical-size supraalveolar peri-implant defect model: characteristics and use

OBJECTIVE

Novel implant technologies and reconstructive therapies for alveolar augmentation require pre-clinical evaluation to estimate their biologic potential, efficacy, and safety before clinical application. The objective of this report is to present characteristics and use of the critical-size, supraalveolar, peri-implant defect model.

METHODS

Bilateral extraction of the mandibular premolars was performed in 12 Hound Labrador mongrel dogs following horizontal surgical cut-down of the alveolar ridge approximating 6 mm. Each jaw quadrant received three custom-produced TiUnite, phi 4.0 x 10 mm threaded implants placed into osteotomies prepared into the extraction sites of the third and fourth premolars. The implants exhibited a reference notch 5 mm from the implant platform to facilitate surgical placement leaving 5 mm of the implant in a supraalveolar position, and to serve as a reference point in the radiographic, histologic and histometric analysis. The implants were submerged under the mucoperiosteal flaps for primary intention healing. Fluorescent bone markers were administered at weeks 3 and 4 post-surgery, and pre-euthanasia. The animals were euthanized following an 8-week healing interval when block biopsies were collected for analysis.

RESULTS

Healing was generally uneventful. The radiographic and histometric evaluations demonstrate the limited osteogenic potential of this defect model. Whereas lingual peri-implant sites exhibited a mean (+/-SE) bone gain of 0.4+/-0.1 mm, resorption of the buccal crestal plate resulted in a mean bone loss of 0.4+/-0.2 mm for an overall osteogenic potential following sham-surgery averaging 0.0+/-0.1 mm. Overall bone density and bone-implant contact in the contiguous resident bone averaged 79.1+/-1.1% and 76.9+/-2.3%, respectively.

CONCLUSION

The results suggest that the critical-size, supraalveolar, peri-implant defect model appears a rigorous tool in the evaluation of candidate technologies for alveolar reconstruction and osseointegration of endosseous oral implants. Limited innate osteogenic potential allows critical evaluation of osteogenic, osteoconductive, or osteoinductive technologies in a challenging clinical setting.

rhBMP-2 delivered in a calcium phosphate cement accelerates bridging of critical-sized defects in rabbit radii

BACKGROUND

Treatment of segmental bone loss remains a challenge in skeletal repairs. This study was performed to evaluate the efficacy of the use of recombinant bone morphogenetic protein-2 (rhBMP-2) delivered in an injectable calcium phosphate cement (alpha bone substitute material [alpha-BSM]) to bridge critical-sized defects in the rabbit radius.

METHODS

Unilateral 20-mm mid-diaphyseal defects were created in the radii of thirty-six skeletally mature New Zealand White rabbits. The defects in twelve rabbits each were filled with 0.166 mg/mL rhBMP-2/alpha-BSM cement, 0.033 mg/mL rhBMP-2/alpha-BSM cement, or buffer/alpha-BSM cement. Six rabbits from each group were killed at four weeks, and six were killed at eight weeks. Serial radiographs were made to monitor defect-bridging and residual alpha-BSM carrier. A semiquantitative histological scoring system was used to evaluate defect-bridging. Histomorphometry was used to quantify residual alpha-BSM; trabecular bone area; trabecular bone volume fraction; and cortical length, width, and area.

RESULTS

At four weeks, there had been more rapid resorption of alpha-BSM and filling of the defects with trabecular bone in the group treated with 0.166 mg/mL rhBMP-2/alpha-BSM than in the other two groups. Histomorphometry confirmed an increased trabecular area and volume fraction in this group compared with the other two groups. In both rhBMP-2/alpha-BSM-treated groups, the majority of the trabecular bone was formed by a direct process adjacent to the resorbing alpha-BSM. At eight weeks, complete cortical bridging and regeneration of the marrow space were present in all of the defects treated with 0.166 mg/mL rhBMP-2/alpha-BSM. That group also had reduced residual alpha-BSM and trabecular area and volume, compared with the other two groups, at eight weeks as a result of a rapid remodeling process.

CONCLUSIONS

Treatment of a critical-sized defect in a rabbit radius with 0.166 mg/mL rhBMP-2/alpha-BSM injectable cement can result in bridging with cortical bone and a regenerated bone-marrow space by eight weeks. Site-specific remodeling appears to be responsible for corticalization and marrow regeneration.

CLINICAL RELEVANCE

RhBMP-2 delivered in a calcium phosphate cement may be useful to achieve bridging of critical-sized defects in patients. Its injectable properties may allow minimally invasive use. Delayed percutaneous administration would also be possible when augmentation is desired following an initial surgical procedure or when soft-tissue injuries preclude adequate initial treatment.

Effects of osteogenic inducers on cultures of canine mesenchymal stem cells

OBJECTIVE

To examine age-related efficacy of bone morphogenetic protein (BMP)-2, ascorbate, and dexamethasone as osteogenic inducers in canine marrow-derived stromal cells (MSCs).

SAMPLE POPULATION

Samples of femoral bone marrow obtained from 15 skeletally immature (< 1 year old) and 4 skeletally mature (> 1.5 years old) dogs.

PROCEDURE

First-passage canine MSC cultures were treated with 100 microg of ascorbate phosphate/mL, 10(-7)M dexamethasone, 100 ng of BMP-2/mL, or a combination of these osteoinducers. On day 6, cultures were harvested for quantitation of alkaline phosphatase (ALP) activity and isolation of RNA to prepare cDNA for real-time polymerase chain reaction analyses of osteoblast markers.

RESULTS

Early markers of osteogenesis were induced in canine MSCs by BMP-2 but not dexamethasone. In young dogs, the combination of BMP-2 and ascorbate yielded the highest ALP mRNA concentrations and activity. This combination also induced significant increases in mRNA for osteopontin and runt-domain transcription factor 2. In comparison to MSCs from immature dogs, those from mature dogs had diminished ALP activity in response to BMP and ascorbate. Results for cultures treated with 3,4-dehydroproline suggested that ascorbate-induced production of extracellular matrix was important for maximal BMP-2 response in canine MSCs.

CONCLUSIONS AND CLINICAL RELEVANCE

BMP-2 was capable of inducing markers of osteogenesis in short-term cultures of canine MSCs. In MSCs obtained from skeletally immature dogs, ascorbate was required for maximal effects of BMP These results define optimal conditions for stem cell osteogenesis in dogs and will facilitate development of stem cell-based treatments for dogs with fractures.

Contour and volume assessment of repairing mandibular osteoperiosteal continuity defects in sheep using recombinant human osteogenic protein 1

BACKGROUND

This study describes the contour and volume of reconstructed mandibles using recombinant human osteogenic protein 1.

MATERIAL AND METHODS

The investigation was conducted on six adult sheep, where a unilateral 35 mm parasymphyseal osteoperiosteal continuity defect of the mandible was created. Recombinant human osteogenic protein 1 and type-I collagen (as carrier) were applied to the defects. Radiographic and ultrasonographic examinations were carried out at day 1 of the surgery and 2, 4, 8, and 12 weeks following the surgery. The animals were then sacrificed 3 months after the operation. Postmortem CT-scan was performed for volumetric, cross-sectional area, height and width measurements.

RESULTS

Ultrasound was more efficient than radiographs in demonstrating early callus formation at 2 weeks, while radiographic evidence of bone formation was consistently detectable only after 4 weeks. Using the combination of recombinant human osteogenic protein type 1 and type-I collagen resulted in twice the volume, cross-sectional surface area, and height when compared with those of the corresponding region of the contra-lateral non-operated side of the mandible.

CONCLUSION

Within 3 months, recombinant human osteogenic protein type 1 on type-I collagen carrier failed to restore the original contour and volume of mandibular osteoperiosteal continuity defects.

Tissue engineering with recombinant human bone morphogenetic protein-2 for alveolar augmentation and oral implant osseointegration: experimental observations and clinical perspectives

Surgical placement of oral implants is governed by the prosthetic design and by the morphology and quality of the alveolar bone. Nevertheless implant placement often appears difficult, if at all possible, due to aberrations of the alveolar ridge. Hence prosthetically dictated implant positioning often entails augmentation of the alveolar ridge and adjoining structures. In this review we discuss recent observations of the biologic potential, clinical relevance, and perspectives of application of recombinant human bone morphogenetic protein-2 (rhBMP-2) technologies for alveolar bone augmentation and oral implant osseointegration. Using discriminating critical-size supraalveolar defects and clinical modeling in dogs, we show that rhBMP-2 has a substantial potential for augmenting alveolar bone and supporting osseointegration of titanium oral implants. Moreover, using clinical modeling, we demonstrate re-osseointegration in advanced periimplantitis defects and long-term functional loading of titanium oral implants placed into rhBMP-2-induced bone. Our studies suggest that inclusion of rhBMP-2 for alveolar bone augmentation and oral implant fixation will not only enhance the predictability of existing clinical protocol but also allow new approaches to these procedures.

Delivery of bone morphogenetic proteins for orthopedic tissue regeneration

Carriers for bone morphogenetic proteins (BMPs) are used to increase retention of these factors at orthopedic treatment sites for a sufficient period of time to allow regenerative tissue forming cells to migrate to the area of injury and to proliferate and differentiate. Carriers can also serve as a matrix for cell infiltration while maintaining the volume in which repair tissue can form. Carriers have to be biocompatible and are often required to be bioresorbable. Carriers also have to be easily, and cost-effectively, manufactured for large-scale production, conveniently sterilized and have appropriate storage requirements and stability. All of these processes have to be approvable by regulatory agencies. The four major categories of BMP carrier materials include natural polymers, inorganic materials, synthetic polymers, composites of these materials. Autograft or allograft carriers have also used. Carrier configurations range from simple depot delivery systems to more complex systems mimicking the extracellular matrix structure and function. Bone regenerative carriers include depot delivery systems for fracture repair, three-dimensional polymer or ceramic composites for segmental repairs and spine fusion and metal or metal/ceramic composites for augmenting implant integration. Tendon/ligament regenerative carriers range from depot delivery systems to three-dimensional carriers that are either randomly oriented or linearly oriented to improve regenerative tissue alignment. Cartilage regenerative systems generally require three-dimensional matrices and often incorporate cells in addition to factors to augment the repair. Alternative BMP delivery systems include viral vectors, genetically altered cells, conjugated factors and small molecules.

Utilisation de facteurs de croissance pour la réparation osseuse

Osteoformation is induced by numerous growth factors that play an important role in bone repair such as fracture healing. They may serve as therapeutic agent in the treatment of squeletal injuries in the orthopeadic and maxillo-facial fields. Among these proteins, Bone Morphogenetic Proteins (BMP) are the only known osteoinductive growth factors. Unfortunately, they are highly susceptible to proteolysis in vivo and require a suitable delivery system to potentiate their biological activity in a local, controlled and durable manner. In this aim, three options are under investigations: (i) osteoinductive materials made of appropriate carrier to release the protein in situ, (ii) in vivo gene therapy in which the gene is directly transfected in cells of the patient or (iii) ex vivo gene therapy in which cells are harvested from the patient, transfected with DNA in culture and then implanted in the defect. These different kinds of BMP delivery will be discussed.

Mechanics and mechano-biology of fracture healing in normal and osteoporotic bone

Fracture repair, which aims at regaining the functional competence of a bone, is a complex and multifactorial process. For the success of fracture repair biology and mechanics are of immense importance. The biological and mechanical environments must be compatible with the processes of cell and tissue proliferation and differentiation. The biological environment is characterized by the vascular supply and by many biochemical components, the biochemical milieu. A good vascular supply is a prerequisite for the initiation of the fracture repair process. The biochemical milieu involves complex interactions among local and systemic regulatory factors such as growth factors or cytokines. The mechanical environment is determined by the local stress and strain within the fracture. However, the local stress and strain is not accessible, and the mechanical environment, therefore, is described by global mechanical factors, e.g., gap size or interfragmentary movement. The relationship between local stress and strain and the global mechanical factors can be obtained by numerical models (Finite Element Model). Moreover, there is considerable interaction between biological factors and mechanical factors, creating a biomechanical environment for the fracture healing process. The biomechanical environment is characterized by osteoblasts and osteocytes that sense the mechanical signal and express biological markers, which effect the repair process. This review will focus on the effects of biomechanical factors on fracture repair as well as the effects of age and osteoporosis.

Evaluation of Recombinant Human Bone Morphogenetic Protein-2 on the Repair of Alveolar Ridge Defects in Baboons

BACKGROUND

The objective of this study was to evaluate alveolar ridge augmentation following surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) using two novel space-providing carrier technologies in the baboon (Papio anubis) model.

METHODS

Standardized alveolar ridge defects ( approximately 15 x 8 x 5 mm) were surgically produced in maxillary and mandibular edentulous areas in four baboons. The defect sites were implanted with rhBMP-2 (0.4 mg/mL) in a tricalcium phosphate/hydroxyapatite/ absorbable collagen sponge composite (TCP/HA/ACS) or calcium phosphate cement (alpha-BSM). Control treatments were TCP/HA/ACS and ?-BSM without rhBMP-2 and sham surgery. Stainless steel pins were placed at the mid-apical and coronal level of the defect sites to provide landmarks for clinical measurements pre- and post-implantation. Impressions were obtained pre- and postimplantation to determine changes in alveolar ridge volume. Radiographic registrations were obtained pre- and post-implantation. Block sections of the defect sites were harvested at week 16 postimplantation and processed for histometric analysis including new bone area and bone density. Statistical comparisons between treatments were made using a mixed effect generalized linear model using least squares estimation.

RESULTS

The carrier systems without rhBMP-2 provided a modest ridge augmentation. The addition of rhBMP-2 resulted in an almost 2-fold increase in alveolar ridge width, including a greater percentage of trabecular bone and a higher bone density compared to controls (P < or =0.05) without significant differences between the two rhBMP-2 protocols.

CONCLUSIONS

TCP/HA/ACS and alphaBSM appear to be suitable carrier technologies for rhBMP-2. Alveolar augmentation procedures using either technology combined with rhBMP-2, rather than stand-alone therapies, may provide clinically relevant augmentation of alveolar ridge defects for placement of endosseous dental implants.

The effect of different mineral frames on ectopic bone formation in mouse hind leg muscles induced by native reindeer bone morphogenetic protein

INTRODUCTION

Bone morphogenetic proteins (BMPs) require carrier material for slow release and framing material for osteoconduction.

MATERIALS AND METHODS

The effect of a frame on early bone formation induced by partially purified native reindeer BMP in composite implants containing 3 mg of BMP, type IV collagen and tricalcium phosphate (TCP/Col/BMP) or hydroxyapatite (HA/Col/BMP) or biphasic tricalcium phosphate-hydroxyapatite (TCP/HA/Col/BMP) or biocoral (NC/Col/BMP) was evaluated using a mouse hind leg muscle pouch model. Collagen with native reindeer BMP (Col/BMP) and corresponding implants without native reindeer BMP served as controls. Evaluation was done by incorporation of 45Ca, radiographically and histologically 3 weeks after the implantation.

RESULTS

None of the implants without native reindeer BMP were able to induce new bone visible on radiographs. The area of new bone formation in the Col/BMP (p=0.026) and TCP/HA/Col/BMP (p=0.012) groups was significantly greater than in the TCP/Col/BMP group. The optical density of the new bone area was significantly greater in the TCP/HA/Col/BMP group than in the TCP/Col/BMP (p=0.036) or Col/BMP (p=0.02) groups. 45Ca incorporation was many times greater in all the groups containing native reindeer BMP than in the corresponding groups without BMP. In the Col/BMP (p=0.046) and TCP/HA/Col/BMP (p=0.046) groups, 45Ca incorporation was significantly greater than in the TCP/Col/BMP group. No significant differences were found in any parameters between HA/Col/BMP and NC/Col/BMP groups and the other BMP-containing groups.

CONCLUSIONS

Hydroxyapatite, biocoral and biphasic tricalciumphosphate-hydroxyapatite are equally good as framing material for native reindeer BMP, while tricalciumphosphate is somewhat worse. Osteoinduction of native reindeer BMP works well with collagen alone.

Histological assessment of bioengineered new bone in repairing osteoperiosteal mandibular defects in sheep using recombinant human bone morphogenetic protein-7

Numerous experimental studies have been published about osteoinductive bone morphogenetic proteins (BMPs). However, to our knowledge there has been no detailed histological study of a mandibular defect in a large mammal, reconstructed using BMPs. We describe here the histological features of rhBMP-7-induced bone in mandibular defects in sheep.

METHODS

A 35 mm osteoperiosteal defect was created at the parasymphyseal region of the mandible in six adult sheep. The continuity of the mandible was maintained using a bony plate, and rhBMP-7 was applied on a type I collagen carrier. Bone labels were injected at selected time intervals during the follow-up period. The animals were killed after 3 months and bone samples were examined histologically, histomorphometrically, and by fluorescence microscopy.

RESULTS AND CONCLUSIONS

We found a mixture of woven and lamellar bone that contained many cells with large nuclei. This had not reorganised to form cortical bone and the rhBMP-7-induced bone was more porous than the native bone. The newly-formed bone restored both endosteal and periosteal layers. rhBMP-7-induced bone was biocompatible and induced no ossification of soft tissue or abnormal growth of nearby vital structures. The mineral apposition rate was 1.98 microm/day (range 0.62-5.63 microm/day), a value close to that reported in humans. This suggests that BMPs have a limited effect in accelerating the rate of mineralisation, but promote the pre-mineralisation processes, and perhaps the formation of woven bone.

rhBMP-2 significantly enhances guided bone regeneration

BACKGROUND

Previous studies have shown a limited potential for bone augmentation following guided bone regeneration (GBR) in horizontal alveolar defects. Surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in such defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained. The objective of this study was to evaluate the potential of rhBMP-2/ACS to enhance GBR using a space-providing, macro-porous expanded polytetrafluoroethylene (ePTFE) device.

METHODS

Bilateral, critical size, supra-alveolar, peri-implant defects were surgically created in four Hound Labrador mongrel dogs. Two turned and one surface-etched 10-mm titanium dental implant were placed 5 mm into the surgically reduced alveolar ridge creating 5-mm supra-alveolar defects. rhBMP-2/ACS (rhBMP-2 at 0.2 mg/ml) or buffer/ACS was randomly assigned to left and right jaw quadrants in subsequent animals. The space-providing, macro-porous ePTFE device was placed to cover rhBMP-2/ACS and control constructs and dental implants. Gingival flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks postsurgery for histologic and histometric analysis.

RESULTS

Bone formation was significantly enhanced in defects receiving rhBMP-2/ACS compared to control. Vertical bone gain averaged (+/- SD) 4.7 +/- 0.3 and 4.8 +/- 0.1 mm, and new bone area 10.3 +/- 2.0 and 8.0 +/- 2.5 mm2 at turned and surface-etched dental implants, respectively. Corresponding values for the control were 1.8 +/- 2.0 and 1.3 +/- 1.3 mm, and 1.8 +/- 1.3 and 1.2 +/- 0.6 mm2. Bone-implant contact in rhBMP-2-induced bone averaged 6.4 +/- 1.4% and 9.6 +/- 7.5% for turned and surface-etched dental implants, respectively (P=0.399). Corresponding values for the control were 14.6 +/- 19.4% and 23.7 +/- 9.7% (P=0.473). Bone-implant contact in resident bone ranged between 43% and 58% without significant differences between dental implant surfaces.

CONCLUSIONS

rhBMP-2/ACS significantly enhances GBR at turned and surface-etched dental implants. The dental implant surface technology does not appear to substantially influence bone formation.

Space-Providing Expanded Polytetrafluoroethylene Devices Define Alveolar Augmentation at Dental Implants Induced by Recombinant Human Bone Morphogenetic Protein 2 in an Absorbable Collagen Sponge Carrier

BACKGROUND

Surgical implantation of recombinant human bone morphogenetic protein 2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in horizontal alveolar defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained.

PURPOSE

The objective of this proof-of-principle study was to evaluate the potential of a space-providing macroporous expanded polytetrafluoroethylene (ePTFE) device to control volume and geometry of rhBMP-2/ACS-induced alveolar bone augmentation.

MATERIALS AND METHODS

Bilateral critical-size supra-alveolar periimplant defects were created in four Hound-Labrador mongrel dogs. Two turned and one surface-etched 10 mm titanium dental implants were placed 5 mm into the surgically reduced alveolar ridge creating 5 mm supra-alveolar defects. rhBMP-2/ACS (0.4 mg rhBMP-2) was placed around the exposed dental implants. Additionally, one jaw quadrant in each animal was randomly assigned to receive the dome-shaped macroporous ePTFE device. Mucoperiosteal flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks post surgery for histometric analysis.

RESULTS

The space-providing macroporous ePTFE device defined the volume and geometry of rhBMP-2/ACS-induced bone formation, whereas bone formation at sites receiving rhBMP-2/ACS alone varied considerably. Vertical bone gain at turned dental implants averaged (+/-SD) 4.7 +/-0.2 mm at sites receiving rhBMP-2/ACS and the ePTFE device compared with 3.5 +/-0.9 mm at sites receiving rhBMP-2/ACS only. The corresponding values for rhBMP-2/ACS-induced bone area were 9.6 +/- 0.7 mm2 and 7.5 +/-6.2 mm2. There was a highly significant correlation between induced bone area and the space provided by the ePTFE device (p <.001). There was no difference in induced bone density or bone-implant contact between the two technologies. These observations were consistent with those observed at surface-etched dental implants.

CONCLUSIONS

The data from this study suggest that a space-providing macroporous ePTFE device defines rhBMP-2/ACS-induced alveolar augmentation to provide adequate bone quantities for implant dentistry. The dental implant surface technology does not appear to substantially influence bone formation.

Investigation of allogeneic mesenchymal stem cell-based alveolar bone formation: preliminary findings

This study was designed to evaluate mesenchymal stem cell (MSC)-based alveolar bone regeneration in a canine alveolar saddle defect model. MSCs were loaded onto hydroxyapatite/tricalcium phosphate (HA/TCP) matrices. Scanning electron microscopic (SEM) evaluation demonstrated greater than 75% MSC coverage of the HA/TCP porous surface prior to placement regardless of MSC donor. Matrices, 6 mm x 6 mm x 20 mm, with and without cells, were implanted for 4 and 9 weeks, then removed for histological evaluation of bone formation. Cell-free control matrices were compared with MSC-loaded matrices post implantation. Histomorphometrical analysis showed that equivalent amounts of new bone were formed within the pores of the matrices loaded with autologous MSCs or MSCs from an unrelated donor. Bone formation in the cell-free HA/TCP matrices was less extensive. There was no histologic evidence of an immunological response to autologous MSCs. Surprisingly, allogeneic MSC implantation also failed to provoke an immune response. Analysis of circulating antibody levels against MSCs supported the hypothesis that neither autologous nor allogeneic MSCs induced a systemic response by the host. Analysis of dye-labelled MSCs in histological sections confirmed that the MSCs persisted in the implants throughout the course of the experiment. At 9 weeks, labelled cells were present within the lacunae of newly formed bone. We conclude that autologous and allogeneic MSCs have the capacity to regenerate bone within craniofacial defects.

Periodontal repair in dogs: space-providing ePTFE devices increase rhBMP-2/ACS-induced bone formation

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) technologies have been shown to enhance alveolar bone formation significantly. Biomaterial (carrier) limitations, however, have restricted their biologic potential for indications where compressive forces may limit the volume of bone formed. The objective of this proof-of-principle study was to evaluate the potential of a space-providing, macroporous ePTFE device to define rhBMP-2-induced alveolar bone formation using a discriminating onlay defect model.

METHODS

Routine, critical size, 5-6 mm, supra-alveolar, periodontal defects were created around the third and fourth mandibular premolar teeth in four young adult Hound Labrador mongrel dogs. All jaw quadrants received rhBMP-2 (0.4 mg) in an absorbable collagen sponge (ACS) carrier. Contralateral jaw quadrants in subsequent animals were randomly assigned to receive additionally the dome-shaped, macroporous ePTFE device over the rhBMP-2/ACS implant or no additional treatment. The gingival flaps were advanced to cover the ePTFE device and teeth, and sutured. Animals were scheduled for euthanasia to provide for histologic observations of healing at 8 weeks postsurgery.

RESULTS

Healing was uneventful without device exposures. New bone formation averaged (+/-SD) 4.7+/-0.2 mm (98%) and 4.5+/-0.4 mm (94%) of the defect height, respectively, for jaw quadrants receiving rhBMP-2/ACS with the ePTFE device or rhBMP-2/ACS alone (p>0.05). In contrast, the regenerated bone area was significantly enhanced in jaw quadrants receiving rhBMP-2/ACS with the ePTFE device compared to rhBMP-2/ACS alone (9.3+/-2.7 versus 5.1+/-1.1 mm2; p<0.05). Cementum formation was similar for both treatment groups. Ankylosis compromised periodontal regeneration in all sites.

CONCLUSIONS

The results suggest that the novel space-providing, macroporous ePTFE device appears suitable as a template to define rhBMP-2/ACS-induced alveolar bone formation.

A preliminary study on the enhancement of the osteointegration of a novel synthetic hydroxyapatite scaffold in vivo

Synthetic hydroxyapatite, a bioactive calcium phosphate, is clinically used as a bone replacement bioceramic because of its similarity in composition to bone mineral, biocompatibility, and osteoconductive nature. The aim of this study was to evaluate the bioactivity of a novel synthetic porous hydroxyapatite (PHA) in vivo in rabbit and to investigate the enhancement of its bioactivity and osteointegration. In the investigation reported here, insulin-like growth factor-I (IGF-I) has been used to enhance the bioactivity of PHA. Cylindrical PHA implants with or without IGF-I were implanted bilaterally in rabbit femurs. Fluorochrome bone markers were administered at 7-day intervals. The implants with the attached bone were retrieved at postmortem, 1 and 3 weeks after implantation, for histological and histomorphometric analysis. Undecalcified sections stained with toluidine blue showed new bone formation. Mineralization of the new bone formed in the interface, surrounding trabecular bone, and within the pores of the implants was studied. Lamellar bone mineral apposition rate (MAR) was assessed and compared among treatment groups, sham, PHA alone, and PHA with IGF-I (500 ng/implant), by fluorochrome label incorporation using UVL microscopy. We report for the first time, that the supplementation of PHA implants with IGF-I significantly increased new bone formation and MAR (6.58 +/- 0.08 microm/day) compared with implantation of PHA alone (4.08 +/- 0.05 microm/day) or sham operation (3.11 +/- 0.12 microm/day). These results suggest that synthetic PHA might provide a delivery system for bioactive agents to accelerate bone healing in orthopedic procedures.

RhBMP-2/alphaBSM induces significant vertical alveolar ridge augmentation and dental implant osseointegration

BACKGROUND

Recombinant human bone morphogenetic protein 2 (rhBMP-2) in a carrier has been shown to induce significant bone formation. Several candidate carriers, however, lack structural integrity to offset compressive forces that may compromise rhBMP-2 bone induction, in particular, for challenging onlay indications such as alveolar ridge augmentation.

PURPOSE

The objective of this study was to evaluate rhBMP-2 in a calcium-phosphate cement carrier, alphaBSM, for vertical alveolar ridge augmentation and immediate dental implant osseointegration.

MATERIALS AND METHODS

Six adult Hound Labrador mongrels with 5 mm critical size supra-alveolar peri-implant defects were used. Three animals received rhBMP-2/alphaBSM (rhBMP-2 at 0.40 and 0.75 mg/mL) in contralateral jaw quadrants (total implant volume/defect approximately 1.5 mL). Three animals received alphaBSM without rhBMP-2 (control group). The animals were euthanized at 16 weeks post surgery, and block biopsies were processed for histologic and histometric analysis.

RESULTS

rhBMP-2/alphaBSM induced substantial augmentation of the alveolar ridge. Control sites exhibited limited new bone formation. Vertical bone augmentation averaged (+/- SD) 4.9 +/- 1.0 mm (rhBMP-2 at 0.40 mg/mL), 5.3 +/- 0.3 mm (rhBMP-2 at 0.75 mg/mL), and 0.4 +/- 0.4 mm (control); new bone area 8.5 +/- 4.2 mm2, 9.0 +/- 1.9 mm2, and 0.5 +/- 0.4 mm2; new bone density 55.1 +/- 6.4%, 61.1 +/- 6.0%, and 67.7 +/- 9.5%; and new bone-implant contact 26.9 +/- 17.5%, 28.5 +/- 1.4%, and 24.6 +/- 16.1%, respectively. Residual alphaBSM comprised < 1% of the new bone. Bone density for the contiguous resident bone ranged from 65 to 71%, and bone-implant contact ranged from 49 to 64%.

CONCLUSIONS

Surgical implantation of rhBMP-2/alphaBSM appears an effective protocol for vertical alveolar ridge augmentation procedures and immediate dental implant osseointegration and for onlay indications of lesser complexity.

Effect of surgical implantation of recombinant human bone morphogenetic protein-2 in a bioabsorbable collagen sponge or calcium phosphate putty carrier in intrabony periodontal defects in the baboon

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) in a proper carrier has been shown to induce clinically relevant bone formation for several oral/maxillofacial and periodontal indications and to stimulate regeneration of the periodontal attachment. The objective of this study is to evaluate regeneration of alveolar bone, cementum, periodontal ligament, and associated root resorption and ankylosis following surgical implantation of rhBMP-2 in an absorbable collagen sponge (ACS) or a calcium phosphate putty (alphaBSM) carrier in 3-wall intrabony periodontal defects in the baboon.

METHODS

rhBMP-2/ACS and rhBMP-2/alphaBSM were implanted in surgically produced, maxillary and mandibular, large size, 3-wall intrabony defects in 4 baboons. Contralateral jaw quadrants were implanted with buffer/ACS, buffer/ alphaBSM, or served as sham-operated surgical controls. Treatments were allocated to left and right, maxillary and mandibular, jaw quadrants following a randomization schedule. Four months following implantation, block biopsies of defect sites were obtained, processed, and subjected to histologic and histometric analysis.

RESULTS

Defect sites receiving rhBMP-2/ACS and rhBMP-2/alphaBSM demonstrated significantly greater regeneration than controls. No significant differences were observed between defect sites receiving rhBMP-2/ACS or rhBMP-2/alphaBSM regarding epithelial migration and connective tissue attachment and new bone formation. However, rhBMP-2/ACS supported significantly greater new cementum formation. Ankylosis or root resorption were not observed.

CONCLUSIONS

The results of this study support the use of rhBMP-2 to enhance periodontal regeneration of intrabony periodontal defects. While this novel technology holds promise, refinement in carrier systems may provide the key to enhancement of the regenerative potential.

Bone consolidation is enhanced by rhBMP-2 in a rabbit model of distraction osteogenesis

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a differentiation factor which has been shown to induce bone formation and heal bony defects in a variety of animal models. A possible application of rhBMP-2 is to accelerate bone regeneration during distraction osteogenesis. which clinically is a long procedure, often involving significant complications. In this study we tested the ability of rhBMP-2 to accelerate the consolidation phase of distraction osteogenesis in a rabbit model of leg lengthening. Tibiae were lengthened 2 cm over a period of ten days. rhBMP-2 was administered at the end of the lengthening phase. Two modes of rhBMP-2 application were tested: surgical implantation of rhBMP-2/ACS (absorbable collagen sponge) into the regenerate (50 microl of 1.5 mg/ml rhBMP-2, total dose = 75 microg rhBMP-2), and percutaneous injection of rhBMP-2/buffer (0.1 ml of 0.75 mg/ml rhBMP-2. total dose = 75 microg rhBMP-2) into three sites within the regenerate. Also, there were three groups of control animals: (1) no surgical intervention, (2) surgical implantation of buffer/ACS and (3) percutaneous injection of buffer. Rabbits were sacrificed at 5, 14 and 28 days after the interventions. Radiographic evaluation indicated a significant increase in bony union of the distraction regenerate in the rhBMP-2 treated groups compared with the untreated groups at 5 and 14 days. At 28 days, formation of a cortex and reestablishment of the medullary canal was evident only in the rhBMP-2 treated groups. The bone mineral content (BMC) of the regenerate was significantly higher in the rhBMP-2 treated groups at 5 and 14 days. However, at 28 days, BMC of the regenerate was similar in all groups. The average volumetric density of the regenerate was significantly higher in the rhBMP-2 injection group at day 14. In Summary, both injection of rhBMP-2/buffer and implantation of rhBMP-2/ACS enhanced the consolidation stage of distraction osteogenesis in this rabbit model.

Genetic approaches to craniofacial tissue repair

This review discusses in some detail the opportunities and challenges of applying gene therapy to the important clinical problem of wound repair and regeneration.

Clinical evaluation of recombinant human bone morphogenetic protein-2

Recombinant human bone morphogenetic protein-2 is an osteoinductive protein that plays a pivotal role in bone growth and regeneration. Several hundred studies were conducted in the past 7 years in numerous animal models to establish unequivocally the efficacy, safety, mechanism of action, pharmacokinetics, and surgical handling properties of recombinant human bone morphogenetic protein-2, building a solid foundation for clinical development programs. Pilot clinical trials have shown the feasibility and safety of recombinant human bone morphogenetic protein-2 treatment, and defined the effective dose for its use in open long bone fractures and for augmentation or preservation of the alveolar bone in the dental ridge. Prospective observational clinical studies helped define clinical efficacy end points, identify significant variables, and estimate appropriate population sample size for pivotal clinical trials. Pivotal clinical trials of recombinant human bone morphogenetic protein-2 are underway in patients with open tibial shaft fractures and in patients with a deficiency of the alveolar ridge.

Osteogenesis of large segmental radius defects enhanced by basic fibroblast growth factor activated bone marrow stromal cells grown on non-woven hyaluronic acid-based polymer scaffold

Osteogenesis of large segmental radius defects in a rat model was studied by implanting a biodegradable non-woven hyaluronic acid-based polymer scaffold (Hyaff 11) alone or in combination with bone marrow stromal cells (BMSCs). These cells had been previously grown in vitro in mineralising medium either supplemented with basic fibroblast growth factor (bFGF) or unsupplemented. The healing of bone defects was evaluated at 40, 80, 160 and 200 days and the repair process investigated by radiographic, histomorphometric (assessment of new bone growth and lamellar bone) and histological analyses (toluidine blue and von Kossa staining). Mineralisation of bone defects occurred in the presence of the Hyaff 11 scaffold alone or when combined with BMSCs grown with or without bFGF, but each process had a different timing. In particular, bFGF significantly induced mineralisation from day 40, whereas 160 days were necessary for direct evidence that a similar process was developing under the other two conditions tested (scaffold alone or with BMSCs). Radiographic score, new bone growth and lamellar bone percentage were highly correlated. The present outcomes were further confirmed by toluidine blue and von Kossa staining. According to these in vivo findings, the Hyaff 11 scaffold is an appropriate carrier vehicle for the repair of bone defects; additionally, it can significantly accelerate bone mineralisation in combination with BMSCs and bFGF.

Differential expression of bone matrix regulatory proteins in human atherosclerotic plaques

In the present study, we examined the expression of regulators of bone formation and osteoclastogenesis in human atherosclerosis because accumulating evidence suggests that atherosclerotic calcification shares features with bone calcification. The most striking finding of this study was the constitutive immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein in nondiseased aortas and the absence of bone morphogenetic protein (BMP)-2, BMP-4, osteopontin, and osteonectin in nondiseased aortas and early atherosclerotic lesions. When atherosclerotic plaques demonstrated calcification or bone formation, BMP-2, BMP-4, osteopontin, and osteonectin were upregulated. Interestingly, this upregulation was associated with a sustained immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein. The 2 modulators of osteoclastogenesis (osteoprotegerin [OPG] and its ligand, OPGL) were present in the nondiseased vessel wall and in early atherosclerotic lesions. In advanced calcified lesions, OPG was present in bone structures, whereas OPGL was only present in the extracellular matrix surrounding calcium deposits. The observed expression patterns suggest a tight regulation of the expression of bone matrix regulatory proteins during human atherogenesis. The expression pattern of both OPG and OPGL during atherogenesis might suggest a regulatory role of these proteins not only in osteoclastogenesis but also in atherosclerotic calcification.