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PubMed2006

Synthesis and characterization of a fluvastatin-releasing hydrogel delivery system to modulate hMSC differentiation and function for bone regeneration.

Increases in bone formation have been demonstrated in mice and rats treated with statins, a group of molecules that increase the production of bone morphogenetic proteins-2 (BMP2) by stimulating its promoter. However, clinical use of statins (e.g., fluvastatin) is limited by the lack of a suitable delivery system to localize and sustain release. To harness the therapeutic effect of statins in orthopedic applications, a fluvastatin-releasing macromer was synthesized. When copolymerized with a dimethacrylated poly(ethylene glycol) solution, this fluvastatin-containing molecule was covalently incorporated into hydrogel networks, and hydrolysis of lactic acid ester bonds resulted in the release of the pendantly tethered fluvastatin from the hydrogel into the surrounding solution. The rate of fluvastatin release was controlled by the length of lactic acid spacer (2-6 repeats), and the dose was controlled by the initial comonomer composition (5-500 microg fluvastatin/gel). Released fluvastatin increased human mesenchymal stem cell (hMSC) gene expression of CBFA1, ALP, and COL I by 34-fold, 2.6-fold, and 1.8-fold, respectively, after 14 days of in vitro culture. In addition, treating hMSCs with the released fluvastatin resulted in an average of 2.0- and 1.5-fold greater BMP2 production whereas mineralization increased an average of 3.0-fold and 2.5-fold for 0.01 and 0.1 microM fluvastatin, respectively, over the 2 week culture period. Therefore, fluvastatin-releasing hydrogels may be useful in bone tissue engineering applications, not only for triggering osteogenic differentiation of hMSCs, but also by modulating their function.

Biocompatible Materials↗
PubMed1991

Novel agents that promote bone regeneration.

Regulation of bone growth is controlled partly by local growth factors, which have effects on bone including the differentiation of precursor cells, osteoblast proliferation, the stimulation of matrix synthesis and angiogenesis. These factors are hypothesized to have a role in augmenting bone repair. In the past year, recombinant technology has provided sufficient material to allow extensive in vivo evaluation of this hypothesis.

Animals↗
PubMed1996

Comparison of bone regeneration with the use of mineralized and demineralized freeze-dried bone allografts: a histological and histochemical study in man.

Mineralized (FDBA) and demineralized freeze-dried bone allografts (DFDBA) have been proposed as substitutes for autologous bone in oral surgery. The demineralization process has been shown, in rodents, to determine osteoinduction in tissues other than bone. Other investigators have reported poor clinical results, in man, with the use of DFDBA. The aim of the present study was a comparative light microscopical and histochemical analysis of bone regeneration processes, in man, with the use of FDBA and DFDBA. Our histological results showed that in DFDBA only the particles near the host bone were involved in the mineralization processes, while in FDBA even the particles that were farthest from the host bone were lined by osteoblasts, actively secreting osteoid matrix and newly formed bone. These results probably point to a more osteoconductive effect of FDBA. No osteoinduction was observed with FDBA or DFDBA.

Bone Demineralization Technique↗
PubMed2005

Bone regeneration in cranial defects previously treated with radiation.

OBJECTIVES/HYPOTHESIS: Bone reconstruction in the head and neck region is frequently performed in the context of previous radiation treatment. Thus, the effectiveness of tissue engineering approaches for regenerating bone in radiated defects needs to be determined before considering application to patients. Incomplete healing is described when using osteoinductive protein therapy alone for bone defects previously treated with radiation. We hypothesized that a different approach using ex vivo gene therapy can heal these severely compromised defects. STUDY DESIGN: Animal study using Fisher rats. METHODS: Two weeks before surgery, rats received either no radiation or a 12 Gray radiation dose to the calvarium. Syngeneic dermal fibroblasts were transduced ex vivo using an adenoviral vector containing the cDNA for bone morphogenetic protein (BMP)-7. Critical-sized calvarial defects were created, and either a transduced cell-seeded scaffold or an autologous bone graft was placed into the defect. Nonradiated defects were harvested 4 weeks later for both groups. Radiated defects treated with bone grafts were harvested at 4 weeks, and those treated with gene therapy were harvested either at 4 or 8 weeks. Gross inspection and histology were used to evaluate wound healing. RESULTS: None of the bone grafts had gross or histologic evidence of healing at the wound margins. The nonradiated gene therapy treated defects revealed gross and histologic near-100% bone regeneration by 4 weeks after surgery. By gross inspection, the radiated defects had soft tissue admixed with islands of bone at both 4 and 8 weeks. The histologic appearance revealed areas of dense bone in a nonconfluent pattern admixed with adjacent cells having the morphologic appearance of hypertrophic chondrocytes, suggesting continued endochondral ossification. CONCLUSIONS: Preoperative radiation significantly impairs the ability of BMP-7 ex vivo gene therapy to heal rat critical-sized cranial defects. This finding has significant implications for translating this tissue engineering approach to patients with cancer-related segmental bone defects.

Animals↗
PubMed1996

Evaluation of guided bone regeneration in rabbit tibia using bioresorbable and non-resorbable membranes.

The aim of this study was an evaluation of the possibility of bone regeneration in connection with implant placement, using a new bioresorbable membrane (Guidor Matrix Barrier) used previously in periodontal tissues regeneration. The study compared the bone regeneration obtained around Bonefit-ITI implants inserted in rabbit tibia using Guidor membranes, Gore-Tex membranes and in control sites. Microscopic analysis was performed after 6, 9 and 12 weeks. It was possible to see that the amount of bone around implants covered by Guidor and Gore-Tex membranes was roughly equivalent in all experimental sites at the 6-, 9- and 12-week time intervals. Also, all control sites healed completely. It could be concluded from this study that: (1) rabbit tibia cannot be recommended in research connected with guided bone regeneration, as all control sites healed in the same way as the test sites; (2) in no case did the presence or the degradation of the resorbable membrane prevent the formation of new bone; (3) no inflammatory reaction was present around the bioresorbable and the non-resorbable membranes; (4) bone formed in all cases on the outer surface of the non-resorbable membranes; (5) large Guidor membrane fragments were present in the 6-week specimens, while in the 12-week specimens only small fragments were recognizable; (6) Guidor membranes can be used in guided bone regeneration.

Animals↗
PubMed2006

Bone regeneration through controlled release of bone morphogenetic protein-2 from 3-D tissue engineered nano-scaffold.

The objective of the present study was to enhance ectopic bone formation through the controlled release of bone morphogenetic protein-2 (BMP-2) from an injectable three dimensional (3-D) tissue engineered nano-scaffold. We demonstrate that a 3-D scaffold can be formed by mixing of peptide-amphiphile (PA) aqueous solution with BMP-2 suspension. A 3-D network of nanofibers was formed by mixing BMP-2 suspensions with dilute aqueous solutions of PA. Scanning electron microscopy (SEM) observation revealed the formation of fibrous assemblies with an extremely high aspect ratio and high surface areas. In vivo release profile of BMP-2 from 3-D network of nanofibers was investigated. In addition, ectopic bone formation induced by the released BMP-2 was assessed in a rat model using histological and biochemical examinations. It was demonstrated that the injection of an aqueous solution of PA together with BMP-2 into the back subcutis of rats, resulted in the formation of a transparent 3-D hydrogel at the injected site and induced significant homogeneous ectopic bone formation around the injected site, in marked contrast to BMP-2 injection alone or PA injection alone. The combination of BMP-2-induced bone formation is a promising procedure to improve tissue regeneration.

Absorptiometry, Photon↗
PubMed1999

Effect of different microstructures of e-PTFE membranes on bone regeneration and soft tissue response: a histologic study in canine mandible.

The purpose of the present study was to compare the effect of 3 types of titanium reinforced e-PTFE membranes (GTRM #1, #2, and #3) on bone regeneration and tissue integration. GTRM #1 was a standard titanium reinforced membrane, GTRM #2 was a prototype characterized by a more open total surface microstructure and GTRM #3 was a prototype characterized by two extremely porous external layers separated by a totally occlusive internal layer. The membranes were used to cover saddle type ridge defects surgically created in the mandible of 6 dogs. After a healing period of 6 months, all the membrane protected sites demonstrated almost complete osseous healing of the defects. GTRM #3 specimens showed the most favourable biologic response, in fact they were characterized by a larger surface of contact between the membrane and the regenerated bone, but from a clinical point of view GTRM #3 material was too difficult to remove. The results of this study suggest that an extremely open porous microstructure, in combination with a totally occlusive barrier, may provide significant improvements in regenerative outcomes. However, these design characteristics may be applied only to resorbable devices, which do not require removal.

Alveolar Process↗
PubMed2004

Spontaneous bone regeneration after mandible resection in a case of ameloblastoma--a case report.

INTRODUCTION: A case of spontaneous bone regeneration after mandible resection is reported. CASE REPORT: A 6-year-old boy suffered from ameloblastoma in his right mandible. Six months after haemimandibulectomy, a bone regeneration forming a new form of mandible is seen. HISTOPATHOLOGY: Lamellar mature bone was observed. Resection of the large portion of the mandible as the choice of treatment as the tumor was grown extensively. Spontaneous bone regeneration after a mandible resection. CONCLUSION: Unexpected spontaneous bone regeneration may be explained by the fact that periosteum, as the source of osteogenic cells, might be responsible for this process.

Ameloblastoma↗
PubMed1999

Guided bone regeneration using titanium grids: report of 10 cases.

In order to ensure an adequate space where new bone can be formed in guided bone regeneration (GBR), most surgeons fill bone defects with biomaterials. In this work we evaluated new bone regeneration in 10 patients using only a blood clot protected with titanium grids and non-resorbable membranes, without any filling material. A manual measurement of the size of the bone defect, using a plastic probe, was performed at 2 surgical steps. After 5 months of treatment, a biopsy was taken from each patient, fixed and embedded in PMMA, examined microradiographically and morphologically to evaluate the newly-formed bone. Our results showed a good repair of the defects by bone regeneration (about 85% overall), high mineral density of new bone around the implants after 5 months, and steady state deposition processes. These results in GBR, without filling material, appear very promising for implantology and reconstructive odontostomatology practice.

Adult↗
PubMedDate not supplied

Engineered pluripotent mesenchymal cells integrate and differentiate in regenerating bone: a novel cell-mediated gene therapy.

BACKGROUND: Among the approximately 6.5 million fractures suffered in the United States every year, about 15% are difficult to heal. As yet, for most of these difficult cases there is no effective therapy. We have developed a mouse radial segmental defect as a model experimental system for testing the capacity of Genetically Engineered Pluripotent Mesenchymal Cells (GEPMC, C3H10T1/2 clone expressing rhBMP-2), for gene delivery, engraftment, and induction of bone growth in regenerating bone. METHODS: Transfected GEPMC expressing rhBMP-2 were further infected with a vector carrying the lacZ gene, that encodes for beta-galactosidase (beta-gal). In vitro levels of rhBMP-2 expression and function were confirmed by immunohistochemistry, and bioassay. Differentiation was assayed using alkaline phosphatase staining. GEPMC were transplanted in vivo into a radial segmental defect. The main control groups included lacZ clones of WT-C3H10T1/2-LacZ, and CHO-rhBMP-2 cells. New bone formation was measured quantitatively via fluorescent labeling, X-ray analysis and histomorphometry. Engrafted mesenchymal cells were localized in vivo by beta-gal expression, and double immunofluorescence. RESULTS: In vitro, GEPMC expressed rhBMP-2, beta-gal and spontaneously differentiated into osteogenic cells expressing alkaline phosphatase. Detection of transplanted cells revealed engrafted cells that had differentiated into osteoblasts and co-expressed beta-gal and rhBMP-2. Analysis of new bone formation revealed that at four to eight week post-transplantation, GEPMS significantly enhanced segmental defect repair. CONCLUSIONS: Our study shows that cell-mediated gene transfer can be utilized for growth factor delivery to signaling receptors of transplanted cells (autocrine effect) and host mesenchymal cells (paracrine effect) suggesting the ability of GEPMC to engraft, differentiate, and stimulate bone growth. We suggest that our approach should lead to the designing of mesenchymal stem cell based gene therapy strategies for bone lesions as well as other tissues.

Animals↗
PubMed2004

Guided bone regeneration at immediate implant insertion and loading: a case report.

A tapered-end, SLA- (sandblasted and acid-etched) surfaced ITI implant was placed in a compromised ridge at the time of tooth removal. After placement of nonautogenous regenerative materials, the implant was immediately loaded with a provisional restoration within 2 hours of implant insertion. Six-month reentry demonstrated regeneration of lostalveolar bone surrounding the implant and clinical implant immobility. Clinical ramifications of these findings are discussed.

Absorbable Implants↗
PubMed2006

Nell-1-induced bone regeneration in calvarial defects.

Many craniofacial birth defects contain skeletal components requiring bone grafting. We previously identified the novel secreted osteogenic molecule NELL-1, first noted to be overexpressed during premature bone formation in calvarial sutures of craniosynostosis patients. Nell-1 overexpression significantly increases differentiation and mineralization selectively in osteoblasts, while newborn Nell-1 transgenic mice significantly increase premature bone formation in calvarial sutures. In the current study, cultured calvarial explants isolated from Nell-1 transgenic newborn mice (with mild sagittal synostosis) demonstrated continuous bone growth and overlapping sagittal sutures. Further investigation into gene expression cascades revealed that fibroblast growth factor-2 and transforming growth factor-beta1 stimulated Nell-1 expression, whereas bone morphogenetic protein (BMP)-2 had no direct effect. Additionally, Nell-1-induced osteogenesis in MC3T3-E1 osteoblasts through reduction in the expression of early up-regulated osteogenic regulators (OSX and ALP) but induction of later markers (OPN and OCN). Grafting Nell-1 protein-coated PLGA scaffolds into rat calvarial defects revealed the osteogenic potential of Nell-1 to induce bone regeneration equivalent to BMP-2, whereas immunohistochemistry indicated that Nell-1 reduced osterix-producing cells and increased bone sialoprotein, osteocalcin, and BMP-7 expression. Insights into Nell-1-regulated osteogenesis coupled with its ability to stimulate bone regeneration revealed a potential therapeutic role and an alternative to the currently accepted techniques for bone regeneration.

Animals↗
PubMed2003

Guided bone regeneration for fenestration defects in dental implants.

Guided bone regeneration has been applied in implant dentistry for increasing the width and height of the alveolar ridge in areas with insufficient bone. Various materials and techniques have been used for this purpose. It refers to a surgical procedure by which utilizing a mechanical barrier to create a secluded space around the defect to permit bone regeneration without the competition of other tissues. This report presents a case with buccal fenestrations on maxillary implant sites observed during a surgical procedure. An allograft and a non-resorbable membrane were concomitantly used to increase the width of the alveolar ridge. Hard tissue regeneration was evident clinically. The implants were restored for functioning and followed for 2 years. Factors affecting outcomes are also discussed. Membrane stability and the space-making effect remain the keys to success.

Bone Regeneration↗
PubMed2001

Effect of recombinant human bone morphogenetic protein-2 on bone regeneration and osseointegration of dental implants.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) induced bone regeneration and osseointegration was evaluated in bony defects created within the hollow chamber of endosseous dental implants in 14 foxhound dogs. Bilateral extractions of mandibular premolars were performed and surgical implantation of 104 hollow cylinder implants followed after 8 weeks of healing. Experimental implants had their hollow chamber filled with 20 microg of rhBMP-2 delivered with a bovine collagen carrier, whereas the control implants had their apical chamber left empty. Dogs were followed for 2, 4, 8 and 12 weeks. Histomorphometric evaluation and immunohistochemical analysis were performed. Minimal bone was regenerated at 2 weeks for both groups. At 4 weeks, bone fill averaged 23.48% for the rhBMP-2 and 5.98% for the control group (P<0.05). At 8 weeks, mean bone fill was 20.94% and 7.75% for the rhBMP-2 and the controls, respectively (P<0.05). At 12 weeks, mean bone fill was 31.39% and 24.31% for the rhBMP-2 and control implants, respectively (P>0.05). Bone-implant contact (BIC) increased for both groups over time and at 8 weeks the rhBMP-2 BIC value was 18.65% and for the control 7.22% (P<0.05). At 12 weeks, the BIC was 43.78% and 21.05% for the rhBMP-2 and the control group, respectively (P<0.05). Immunohistochemical staining for type II collagen was positive only for parts of the collagen carrier and formation of cartilaginous intermediate was not observed in any of the specimens. The results suggest that, in confined defects adjacent to dental implants, rhBMP-2 can induce bone regeneration in close apposition to the implant surface.

Animals↗
PubMedDate not supplied

Bone regeneration after peri-implant care with the CO2 laser: a fluorescence microscopy study.

PURPOSE: The carbon dioxide (CO2) laser has been shown to be suitable for the treatment of ailing implants. However, comparatively little is known about bone regeneration after laser treatment. Therefore, the purpose of this study was to determine the course of bone regeneration after peri-implant care with the CO2 laser. MATERIALS AND METHODS: In 6 beagle dogs, a total of 60 implants and bony defects were treated either conventionally by air-powder abrasive (group 1), by laser irradiation alone (group 2), or by a combination of the 2 (group 3). After therapy, polychrome sequence labeling was performed using 4 different markers. Four months later, after sacrifice, histologic sections were photographed and scanned. In each specimen, the 4 stained areas were detected with special software and indicated as a percentage of the standardized measurement frame. Lastly, the time-course of the bone regeneration was determined for each of the 3 therapy groups. RESULTS: Fluorescence microscopy demonstrated maximum bone regeneration after 8 weeks in all 3 therapy groups. In this period, groups 2 and 3 showed significantly greater amounts of newly formed bone than group 1 (P < .03 and P < .05, respectively). However, there was no difference in bone regeneration between groups 2 and 3. DISCUSSION: Using fluoresence microscopy, it was possible to analyze and interpret the bone regeneration processes during all 4 application phases of the 3 groups. CONCLUSIONS: These results support the hypothesis that CO2 laser irradiation renders significantly more new bone formation, especially 5 to 8 weeks postoperatively, than conventional decontamination in the dog model. Further investigation will be required to determine the clinical efficacy.

Air Abrasion, Dental↗
PubMed2000

Guided bone regeneration with titanium membranes: a clinical study.

Guided bone regeneration using barrier membranes is useful in bone augmentation. Because the commonly used polytetrafluoroethylene (PTFE, Gore-Tex (R), WL Gore, Flagstaff, AZ, USA) membranes or resorbable membranes tend to collapse, more stable membranes are desirable. A titanium membrane (FRIOS(R) BoneShield, Friatec, Mannheim, Germany) was evaluated in a clinical study of 52 patients. Most of them had particulate bone grafts or phycogene hydroxyapatite (Algipore(R), Friatec, Mannheim, Germany) or both stabilized with titanium membranes. In 78 procedures, 23 membranes (29%) became exposed, but only seven of these (9%) led to failure of the graft with a considerable loss of augmented material. The time interval between operation and possibly exposure was responsible for the result. Early exposures (within a few weeks) led to poor formation of new bone within the grafts, whereas if exposure was later, results were as good as in procedures in which the membranes did not become exposed.

Adult↗
PubMed1999

Clinically applied models of bone regeneration in tissue engineering research.

The development of new strategies for the engineering of bone regeneration requires appropriate model systems. Selection of the best model for testing a new technology depends on a host of factors. In general, the best model system is the one which most closely mimics the clinical situation for which this technology is being developed, will not heal spontaneously unless the technology is used, and will not heal when another technology is used if that technology is less advanced than the one being tested. For the purposes of developing new strategies for bone regeneration, systems which can be considered include those which model normal fracture healing, the segmental loss of bone or critical size defects, and various forms of nonunions in which fracture healing is perturbed either by mechanical, metabolic, or neurologic means. Careful experimental design and selection of the appropriate model system will enhance scientific efforts in bone regeneration research.

Animals↗