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Bone Regeneration (bone + regeneration)
Kinds of Bone Regeneration Selected AbstractsSkeletal Cell Fate Decisions Within Periosteum and Bone Marrow During Bone Regeneration,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2009Céline Colnot Abstract Bone repair requires the mobilization of adult skeletal stem cells/progenitors to allow deposition of cartilage and bone at the injury site. These stem cells/progenitors are believed to come from multiple sources including the bone marrow and the periosteum. The goal of this study was to establish the cellular contributions of bone marrow and periosteum to bone healing in vivo and to assess the effect of the tissue environment on cell differentiation within bone marrow and periosteum. Results show that periosteal injuries heal by endochondral ossification, whereas bone marrow injuries heal by intramembranous ossification, indicating that distinct cellular responses occur within these tissues during repair. Next, lineage analyses were used to track the fate of cells derived from periosteum, bone marrow, and endosteum, a subcompartment of the bone marrow. Skeletal progenitor cells were found to be recruited locally and concurrently from periosteum and/or bone marrow/endosteum during bone repair. Periosteum and bone marrow/endosteum both gave rise to osteoblasts, whereas the periosteum was the major source of chondrocytes. Finally, results show that intrinsic and environmental signals modulate cell fate decisions within these tissues. In conclusion, this study sheds light into the origins of skeletal stem cells/progenitors during bone regeneration and indicates that periosteum, endosteum, and bone marrow contain pools of stem cells/progenitors with distinct osteogenic and chondrogenic potentials that vary with the tissue environment. [source] Bone Regeneration Is Regulated by Wnt Signaling,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2007Jae-Beom Kim Abstract Tissue regeneration is increasingly viewed as reactivation of a developmental process that, when misappropriated, can lead to malignant growth. Therefore, understanding the molecular and cellular pathways that govern tissue regeneration provides a glimpse into normal development as well as insights into pathological conditions such as cancer. Herein, we studied the role of Wnt signaling in skeletal tissue regeneration. Introduction: Some adult tissues have the ability to regenerate, and among these, bone is one of the most remarkable. Bone exhibits a persistent, lifelong capacity to reform after injury, and continual bone regeneration is a prerequisite to maintaining bone mass and density. Even slight perturbations in bone regeneration can have profound consequences, as exemplified by conditions such as osteoporosis and delayed skeletal repair. Here, our goal was to determine the role of Wnts in adult bone regeneration. Materials and Methods: Using TOPgal reporter mice, we found that damage to the skeleton instigated Wnt reporter activity, specifically at the site of injury. We used a skeletal injury model to show that Wnt inhibition, achieved through adenoviral expression of Dkk1 in the adult skeleton, prevented the differentiation of osteoprogenitor cells. Results: As a result, injury-induced bone regeneration was reduced by 84% compared with controls. Constitutive activation of the Wnt pathway resulting from a mutation in the Lrp5 Wnt co-receptor results in high bone mass, but our experiments showed that this same point mutation caused a delay in bone regeneration. In these transgenic mice, osteoprogenitor cells in the injury site were maintained in a proliferative state and differentiation into osteoblasts was delayed. Conclusions: When considered together, these data provide a framework for understanding the roles of Wnt signaling in adult bone regeneration and suggest a feasible approach to treating clinical conditions where enhanced bone formation is desired. [source] Aged Mice Require Full Transcription Factor, Runx2/Cbfa1, Gene Dosage for Cancellous Bone Regeneration After Bone Marrow Ablation,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2004Kunikazu Tsuji Abstract Runx2 is prerequisite for the osteoblastic differentiation in vivo. To elucidate Runx2 gene functions in adult bone metabolism, we conducted bone marrow ablation in Runx2 heterozygous knockout mice and found that aged (but not young) adult Runx2 heterozygous knockout mice have reduced new bone formation capacity after bone marrow ablation. We also found that bone marrow cells from aged Runx2 heterozygous knockout mice have reduced ALP+ colony-forming potential in vitro. This indicates that full Runx2 dosage is needed for the maintenance of osteoblastic activity in adult mice. Introduction: Null mutation of the Runx2 gene results in total loss of osteoblast differentiation, and heterozygous Runx2 deficiency causes cleidocranial dysplasia in humans and mice. However, Runx2 gene functions in adult bone metabolism are not known. We therefore examined the effects of Runx2 gene function in adult mice with heterozygous loss of the Runx2 gene. Materials and Methods: Bone marrow ablation was conducted in young adult (2.5 ± 0.5 months old) or aged adult (7.5 ± 0.5 months old) Runx2 heterozygous knockout mice and wildtype (WT) littermates. Cancellous bone regeneration was evaluated by 2D ,CT. Results: Although new bone formation was observed after bone marrow ablation in the operated bone marrow cavity of WT mice, such bone formation was significantly reduced in Runx2 heterozygous knockout mice. Interestingly, this effect was observed specifically in aged but not young adult mice. Runx2 heterozygous deficiency in aged mice significantly reduced the number of alkaline phosphatase (ALP)+ cell colonies in the bone marrow cell cultures, indicating a reduction in the numbers of osteoprogenitor cells. Such effects of heterozygous Runx2 deficiency on osteoblasts in vitro was specific to the cells from aged adult mice, and it was not observed in the cultures of marrow cells from young adult mice. Conclusion: These results indicate that full gene dosage of Runx2 is required for cancellous bone formation after bone marrow ablation in adult mice. [source] Efficacy of Bone Marrow Mononuclear Cells to Promote Bone Regeneration Compared With Isolated CD34+ Cells From the Same Volume of AspirateARTIFICIAL ORGANS, Issue 7 2010Shinji Yasuhara Abstract Autologous bone marrow mononuclear cell (BMMNC) transplantation is currently an emerging clinical treatment in the orthopedic as well as cardiovascular fields. It is believed that the therapeutic effect of the BMMNCs is due to neovascularization enhanced by the CD34+ cells contained therein, which include endothelial progenitor cells. However, isolation of the CD34+ cell fraction for clinical application has many disadvantages such as cost and invasiveness related to cell mobilization with cytokine. To investigate whether a purification step is in fact necessary for bone regeneration, we separated BMMNCs, CD34+, and CD34 - cells from the same initial volume of rabbit bone marrow aspirates. We then transplanted them back into a femoral bone defect of the same rabbit together with atelocollagen gel and basic fibroblast growth factor (bFGF) and evaluated neovascularization and bone regeneration up to 8 weeks after transplantation. The greatest potential for neovascularization and bone regeneration medicated by cells from the same volume of bone marrow aspirate was found in the BMMNC group. Although purified CD34+ cells might be an ideal cell source, BMMNCs could be a practical and feasible cell source for bone regeneration in present clinical settings with limited cost, availability of materials, and technical issues for transplantation. [source] Effects of Implant Design and Surface on Bone Regeneration and Implant Stability: An Experimental Study in the Dog MandibleCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2001Lars Rasmusson DMD ABSTRACT Background: Previous experimental studies have shown a higher degree of bone-implant contact for surface-enlarged implants compared with machined implants. Yet, there is insufficient evidence that such implants show higher stability and an increased survival rate. Purpose: The purpose of this investigation was to study the integration and stability of grit-blasted implants with retention elements on the implant neck, with and without marginal bone defects, compared with machined implants without retention elements. Materials and Methods: After tooth extraction of the mandibular premolars in six dogs, two grit-blasted, partly microthreaded Astra Tech implants and one standard Branemark implant were bilaterally placed in each dog. On one side, 3 ± 3 mm large buccal defects were created, to expose three to four implant threads. The contralateral side served as control, and no defects were made. The animals were sacrificed after 4 months of healing. Implant stability was measured using resonance frequency analysis at implant installation and after 4 months of healing. Histologic and histomorpho-metric evaluation was made after 4 months of healing. Results: Resonance frequency analysis indicated that all implants in the test and control groups were osseointegrated after 4 months, with a tendency toward higher implant stability for the Astra Tech implants. There was a statistically significant higher increase in resonance frequency for the Astra test implants compared with their corresponding controls. Histology and histomorphometry showed well-integrated implants with varying degrees of bone repair at the defect sites. The greater bone-implant contact for the Astra implants was statistically significant. No significant difference between the implants in amount of bone filling the threads was recorded. Conclusions: The Astra Tech implants tested showed a higher degree of bone,implant contact and higher level of bone regenerated at defect sites compared with the Brånemark implants. Resonance frequency analysis demonstrated a significantly higher increase in the Astra test implants compared with their control groups than did the Brånemark test implants versus their controls. [source] Bone regeneration in rabbit sinus lifting associated with bovine BMPJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004Sergio Allegrini Jr. Abstract Autogenous bone is considered the optimal grafting material for sinus lifting, although its harvesting causes great patient discomfort. Various approaches have been taken in order to obtain sinus lifting with preexisting tissue. However, because of the unsuitability of such tissue, additional materials have been required. Alternatively, biomaterials from humans or other animals are used. In this study, the efficacy of using morphogenetic bovine bone protein (BMPb) to augment the maxillary sinus floor was examined. Four grafting materials were employed: lyophilized bovine bone powder, absorbable collagen flakes, natural hydroxylapatite, and synthetic hydroxylapatite. Two groups of rabbits were studied. In one group, graft material only was used. In the other, graft material was combined with 0.5 mg BMPb. During 8 weeks of observation, polyfluorochrome tracers were injected in subcutaneous tissue to evaluate new bone- deposition periods. Following sacrifice, the samples were examined under fluorescent and light microscopes. Results indicated 33.34% more newly formed bone in BMPb animals than in controls. Graft-material resorption increased, but natural HA showed no significant alterations. The results show that the use of BMPb, although providing osteoinduction, might not promote sufficient bone formation. Nonetheless, this material could provide an alternative to autogenous grafts, thereby avoiding patient discomfort. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 127,131, 2004 [source] Bone regeneration in dehiscence-type defects at chemically modified (SLActive®) and conventional SLA titanium implants: a pilot study in dogsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2007Frank Schwarz Abstract Objectives: The aim of the present study was to evaluate bone regeneration in dehiscence-type defects at titanium implants with chemically modified (mod) and conventional sand-blasted/acid-etched (SLA) surfaces. Material and Methods: Standardized buccal dehiscence defects (height: 3 mm, width: 3 mm) were surgically created following implant site preparation in both the upper and lower jaws of four beagle dogs. modSLA and SLA implants were inserted bilaterally according to a split-mouth design. The animals were sacrificed after 2 and 12 weeks (n=2 animals each). Dissected blocks were processed for histomorphometrical analysis: defect length, new bone height (NBH), percent linear fill (PLF), percent of bone-to-implant contact (BIC-D) and area of new bone fill (BF). Results: Wound healing at SLA implants was predominantly characterized by the formation of a dense connective tissue at 2 and 12 weeks, without significant increases in mean NBH, PLF, BIC-D or BF values. In contrast, modSLA implants exhibited a complete defect fill at 12 weeks following implant placement. In particular, histomorphometrical analysis revealed the following mean values at 12 weeks: NBH (3.2±0.3 mm), PLF (98%), BIC-D (82%) and BF (2.3±0.4 mm2). Conclusion: Within the limits of the present study, it was concluded that modSLA titanium surfaces may promote bone regeneration in acute-type buccal dehiscence defects at submerged implants. [source] Low intensity pulsed ultrasound accelerated bone remodeling during consolidation stage of distraction osteogenesisJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2006Chun Wai Chan Abstract Bone regeneration in distraction osteogenesis occurs under tensile stress with axial rhythmic distraction after osteotomy. In this study, we evaluated if the low intensity pulsed ultrasound (LIPUS) was also effective on enhancement of bone remodeling during consolidation stage of distraction osteogenesis. Open osteotomy of seventeen 18-week-old female New Zealand rabbit tibiae were performed. The distraction was applied with the rate of 1 mm per day. LIPUS (30 mW/cm2, 1.5 MHz) was delivered for 20 min per day during 4-week consolidation stage (n,=,10). The animals without treatment served as sham group (n,=,7). Plain X-ray, peripheral quantitative computational tomography (pQCT), and torsional test were performed. Results showed that smaller radiolucent interzone of LIPUS treatment group was gradually occupied by calcified tissue in plain X-ray at week 2. The bone mineral density (BMD) measured on radiographs increased by 9.18% in the LIPUS group. Bone mineral content (BMC), hard callus volume, and bone strength index (BSI) measured by pQCT were 83%, 116%, and 94%, respectively, in LIPUS group that were significantly greater than those of the controls. At the 4th week, LIPUS-treated callus showed the development of neocorticalization in the proximal and distal region. The BMC, hard callus volume, and BSI of LIPUS group decreased and was not significantly different from control. This was also confirmed by the maximum torque of LIPUS-treated callus (1424.2,±,457.3 N,·,mm) obtained at week 4, which did not differ from that of the sham group (1968.8,±,895.1 N,·,mm). In conclusion, the effective period of LIPUS treatment was at the initial stage of consolidation, with accelerated bone formation and remodeling. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Induction of a neoarthrosis by precisely controlled motion in an experimental mid-femoral defectJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2002Dennis M. Cullinane Bone regeneration during fracture healing has been demonstrated repeatedly, yet the regeneration of articular cartilage and joints has not yet been achieved. It has been recognized however that the mechanical environment during fracture healing can be correlated to the contributions of either the endochondral or intramembranous processes of bone formation, and to resultant tissue architecture. Using this information, the goal of this study was to test the hypothesis that induced motion can directly regulate osteogenic and chondrogenic tissue formation in a rat mid-femoral bone defect and thereby influence the anatomical result. Sixteen male Sprague Dawley rats (400 ± 20 g) underwent production of a mid-diaphyseal, non-critical sized 3.0 mm segmental femoral defect with rigid external fixation using a custom designed four pin fixator. One group of eight animals represented the controls and underwent surgery and constant rigid fixation. In the treatment group the custom external fixator was used to introduce daily interfragmentary bending strain in the eight treatment animals (12°s angular excursion), with a hypothetical symmetrical bending load centered within the gap. The eight animals in the treatment group received motion at 1.0 Hz, for 10 min a day, with a 3 days on, one day off loading protocol for the first two weeks, and 2 days on, one day off for the remaining three weeks. Data collection included histological and immunohistological identification of tissue types, and mean collagen fiber angles and angular conformity between individual fibers in superficial, intermediate, and deep zones within the cartilage. These parameters were compared between the treatment group, rat knee articular cartilage, and the control group as a structural outcome assessment. After 35 days the control animals demonstrated varying degrees of osseous union of the defect with some animals showing partial union. In every individual within the mechanical treatment group the defect completely failed to unite. Bony arcades developed in the experimental group, capping the termini of the bone segments on both sides of the defect in four out of six animals completing the study. These new structures were typically covered with cartilage, as identified by specific histological staining for Type II collagen and proteoglycans. The distribution of collagen within analogous superficial, intermediate, and deep zones of the newly formed cartilage tissue demonstrated preferred fiber angles consistent with those seen in articular cartilage. Although not resulting in complete joint development, these neoarthroses show that the induced motion selectively controlled the formation of cartilage and bone during fracture repair, and that it can be specifically directed. They further demonstrate that the spatial organization of molecular components within the newly formed tissue, at both microanatomical and gross levels, are influenced by their local mechanical environment, confirming previous theoretical models. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Bone regeneration of dental implant dehiscence defects using a cultured periosteum membraneCLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2008Daiki Mizuno Abstract Objectives: This study aimed to demonstrate the feasibility of a cultured periosteum (CP) membrane for use in guided bone regeneration at sites of implant dehiscence. Material and methods: Four healthy beagle dogs were used in this study. Implant dehiscence defects (4 × 4 × 3 mm) were surgically created at mandibular premolar sites where premolars had been extracted 3 months back. Dental implants (3.75 mm in diameter and 7 mm in length) with machined surfaces were placed into the defect sites (14 implants in total). Each dehiscence defective implant was randomly assigned to one of the following two groups: (1) PRP gel without cells (control) or (2) a periosteum membrane cultured on PRP gel (experimental). Dogs were killed 12 weeks after operation and nondecalcified histological sections were made for histomorphometric analyses including percent linear bone fill (LF) and bone-to-implant contact (BIC). Results: Bone regeneration in the treatment group with a CP membrane was significantly greater than that in the control group and was confirmed by LF analysis. LF values in the experimental and the control groups were 72.36±3.14% and 37.03±4.63%, respectively (P<0.05). The BIC values in both groups were not significantly different from each other. The BIC values in the experimental and the control groups were 40.76±10.30% and 30.58±9.69%, respectively (P=0.25) and were similar to native bone. Conclusion: This study demonstrated the feasibility of a CP membrane to regenerate bone at implant dehiscence defect. [source] Reconstruction of a Rabbit Ulna Bone Defect Using Bone Marrow Stromal Cells and a PLA/, -TCP Composite by a Novel Sintering Method,ADVANCED ENGINEERING MATERIALS, Issue 11 2009Youngmee Jung We developed PLA/, -TCP composites with a novel sintering method in order to enhance cellular interaction with matrices for bone regeneration. Thereafter, we confirmed the superior bone-forming characteristics of PLA/, -TCP cell-composite constructs resulting from greater surface exposure of the , -TCP particles, which may yield higher osteogenic and osteoconductive properties. [source] Zebrafish sp7:EGFP: A transgenic for studying otic vesicle formation, skeletogenesis, and bone regenerationGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 8 2010April DeLaurier Adult transgenic zebrafish expressing eGFP under the control of the zinc finger transcription factor Sp7 gene, which is expressed in osteoblasts but not chondrocytes. In this line, eGFP expression recapitulates the endogenous gene pattern of expression in the otic placode, otic vesicle and developing skeletal structures. GFP-positive cells are also observed in adult skeletal structures and in regenerating fins. This transgenic line will be a very useful tool for studying otic development and the development and regeneration of the skeleton. See the article by DeLaurier et al. in this issue. [source] Hydroxyapatite fiber material with BMP-2 gene induces ectopic bone formationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009Mitsumasa Oda Abstract Collagen containing bone morphogenetic protein-2 (BMP-2) expression vector, which is called "gene-activated matrix," promotes bone regeneration when transplanted to the bone defect. We speculated that hydroxyapatite fiber (HF) would be an ideal matrix for "gene-activated matrix" especially for bone regeneration, because it is oseteoconductive and has high affinity to DNA. The purpose of this study is to clarify whether HF containing BMP-2 expression vector induces ectopic bone formation. We prepared HF containing 0, 10, 50, and 100 ,g BMP-2 expression vector. Wistar male rats (8 weeks) were used and each rat received two HF implants in the left and right dorsal muscle. The rats were sacrificed 4, 8, and 12 weeks after the operation, and implants were analyzed radiographically by softex, dual-energy X-ray absorptiometry, and they were histologically examined. At 4 weeks, HF containing 50 or 100 ,g BMP-2 expression vector showed high bone mineral contents and large radiopaque volume compared to the other implants. At 8 and 12 weeks, HF containing 50 ,g BMP-2 expression vector exerted the highest values in the radiographic analyses. Bonelike tissue was histologically observed in HF containing 50 and 100 ,g BMP-2 expression vector groups but not detected in the other implants. The present results suggest that HF is potential as a matrix for "gene-activated matrix" for bone tissue engineering. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Growth of osteoblast-like cells on biomimetic apatite-coated chitosan scaffoldsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008I. Manjubala Abstract Porous scaffold materials that can provide a framework for the cells to adhere, proliferate, and create extracellular matrix are considered to be suitable materials for bone regeneration. Interconnected porous chitosan scaffolds were prepared by freeze-drying method, and were mineralized by calcium and phosphate solution by double-diffusion method to form nanoapatite in chitosan matrix. The mineralized chitosan scaffold contains hydroxyapatite nanocrystals on the surface and also within the pore channels of the scaffold. To assess the effect of apatite and porosity of the scaffolds on cells, human osteoblast (SaOS-2) cells were cultured on unmineralized and mineralized chitosan scaffolds. The cell growth on the mineralized scaffolds and on the pure chitosan scaffold shows a similar growth trend. The total protein content and alkaline phosphatase enzyme activity of the cells grown on scaffolds were quantified, and were found to increase over time in mineralized scaffold after 1 and 3 weeks of culture. The electron microscopy of the cell-seeded scaffolds showed that most of the outer macropores became sealed off by a continuous layer of cells. The cells spanned around the pore wall and formed extra cellular matrix, consisting mainly of collagen in mineralized scaffolds. The hydroxyproline content also confirmed the formation of the collagen matrix by cells in mineralized scaffolds. This study demonstrated that the presence of apatite nanocrystals in chitosan scaffolds does not significantly influence the growth of cells, but does induce the formation of extracellular matrix and therefore has the potential to serve for bone tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] In vitro change in mechanical strength of ,-tricalcium phosphate/copolymerized poly- L -lactide composites and their application for guided bone regenerationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002Masanori Kikuchi Abstract Novel composites of bioactive ,-tricalcium phosphate [Ca3(PO4)2] and biodegradable copolymerized poly- L -lactide (CPLA) were prepared by a heat-kneading method. The mechanical and chemical changes of the composites were evaluated in vitro by soaking in physiological saline and Dulbecco's phosphate buffered saline. When soaked in physiological saline, the 3-point mechanical strength decreased rapidly from 60 to 30 MPa in the initial 4 weeks and then gradually reached a plateau; the initial decrease in the mechanical strength was ascribed to the dissolution of ,-tricalcium phosphate from the surface. The mechanical properties evident at 8,12 weeks were sufficient for the composites to be used as a biodegradable material for regeneration of bone because the hydrolysis of CPLA was inhibited in both physiological saline and phosphate-buffered saline as a result of a pH-buffering effect. Composite membranes 250-,m thick were used to regenerate large bone defects in beagle dogs: 10 × 10 × 10 mm3 in volume in the mandible and 20 mm in length in the tibia. The afflicted areas covered with the composite membranes were almost perfectly filled with new bone 12 weeks after the operation, whereas those covered with a CPLA membrane or without any membranes were invaded by soft tissue. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 265,272, 2002 [source] A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgeryJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 5 2001Anita A. Ignatius Abstract The aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL-lactide) and ,-tricalcium phosphate in comparison to a membrane made of pure poly(L, DL-lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 °C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 ± 2.4 MPa and 27.7 ± 2.3 MPa and the elastic modulus 3106 ± 108 MPa and 3101 ± 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 564,569, 2001 [source] Regulation of Osteogenesis-Angiogenesis Coupling by HIFs and VEGF,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2009Ernestina Schipani Abstract Bone is a highly vascularized tissue, but the function of angiogenesis in bone modeling and remodeling is still poorly defined, and the molecular mechanisms that regulate angiogenesis in bone are only partially elucidated. Genetic manipulations in mice have recently highlighted the critical role of the hypoxia-inducible-factor/vascular endothelial growth factor pathway in coupling angiogenesis and osteogenesis. In this brief perspective, we review the current understanding of the mechanisms responsible for this coupling. Elucidation of such mechanisms will expand our knowledge of bone development and homeostasis, and it may aid in the design of new therapies for accelerating bone regeneration and repair. [source] Skeletal Cell Fate Decisions Within Periosteum and Bone Marrow During Bone Regeneration,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2009Céline Colnot Abstract Bone repair requires the mobilization of adult skeletal stem cells/progenitors to allow deposition of cartilage and bone at the injury site. These stem cells/progenitors are believed to come from multiple sources including the bone marrow and the periosteum. The goal of this study was to establish the cellular contributions of bone marrow and periosteum to bone healing in vivo and to assess the effect of the tissue environment on cell differentiation within bone marrow and periosteum. Results show that periosteal injuries heal by endochondral ossification, whereas bone marrow injuries heal by intramembranous ossification, indicating that distinct cellular responses occur within these tissues during repair. Next, lineage analyses were used to track the fate of cells derived from periosteum, bone marrow, and endosteum, a subcompartment of the bone marrow. Skeletal progenitor cells were found to be recruited locally and concurrently from periosteum and/or bone marrow/endosteum during bone repair. Periosteum and bone marrow/endosteum both gave rise to osteoblasts, whereas the periosteum was the major source of chondrocytes. Finally, results show that intrinsic and environmental signals modulate cell fate decisions within these tissues. In conclusion, this study sheds light into the origins of skeletal stem cells/progenitors during bone regeneration and indicates that periosteum, endosteum, and bone marrow contain pools of stem cells/progenitors with distinct osteogenic and chondrogenic potentials that vary with the tissue environment. [source] Bone Regeneration Is Regulated by Wnt Signaling,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2007Jae-Beom Kim Abstract Tissue regeneration is increasingly viewed as reactivation of a developmental process that, when misappropriated, can lead to malignant growth. Therefore, understanding the molecular and cellular pathways that govern tissue regeneration provides a glimpse into normal development as well as insights into pathological conditions such as cancer. Herein, we studied the role of Wnt signaling in skeletal tissue regeneration. Introduction: Some adult tissues have the ability to regenerate, and among these, bone is one of the most remarkable. Bone exhibits a persistent, lifelong capacity to reform after injury, and continual bone regeneration is a prerequisite to maintaining bone mass and density. Even slight perturbations in bone regeneration can have profound consequences, as exemplified by conditions such as osteoporosis and delayed skeletal repair. Here, our goal was to determine the role of Wnts in adult bone regeneration. Materials and Methods: Using TOPgal reporter mice, we found that damage to the skeleton instigated Wnt reporter activity, specifically at the site of injury. We used a skeletal injury model to show that Wnt inhibition, achieved through adenoviral expression of Dkk1 in the adult skeleton, prevented the differentiation of osteoprogenitor cells. Results: As a result, injury-induced bone regeneration was reduced by 84% compared with controls. Constitutive activation of the Wnt pathway resulting from a mutation in the Lrp5 Wnt co-receptor results in high bone mass, but our experiments showed that this same point mutation caused a delay in bone regeneration. In these transgenic mice, osteoprogenitor cells in the injury site were maintained in a proliferative state and differentiation into osteoblasts was delayed. Conclusions: When considered together, these data provide a framework for understanding the roles of Wnt signaling in adult bone regeneration and suggest a feasible approach to treating clinical conditions where enhanced bone formation is desired. [source] Application of Histomorphometric Methods to the Study of Bone Repair,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2005Louis C Gerstenfeld Abstract ABSTRACT: Standardized methods for the histomorphometric assessment of bone are essential features of most studies of metabolic bone diseases and their treatments. These methodologies were developed to assess coupled remodeling, focusing primarily on osteoblasts and osteoclasts, the anabolic and catabolic rates of these cells, and structural features of mature bone. Research studies on bone healing and the development of new therapeutic approaches for the enhancement of bone repair also require a comprehensive understanding of the basic cellular and tissue level mechanisms that underlie these processes. However, the histological methods developed for metabolic bone disease studies are not completely suitable for studies of bone repair because they are based on assumptions that there is little variation in tissue composition within a sample of bone and not generally designed to quantify other types of tissues, such as cartilage, that contribute to bone healing. These techniques also do not provide tissue-based structural measurements that are relatable to the specific types of biomechanical and radiographic structural assessments that are used to determine rates of bone healing. These deficiencies in current histological approaches therefore point to the need to establish standardized criteria for the histomorphometric assessments that are specifically adapted for the study of bone repair in models of fracture healing and bone regeneration. In this Perspective, we outline what we believe to be the specific structural, tissue. and cellular aspects that need to be addressed to establish these standardized criteria for the histomorphometric assessment of bone repair. We present the specific technical considerations that need to be addressed to appropriately sample repair tissues to obtain statistically meaningful results and suggest specific procedures and definitions of nomenclatures for the application of this technology to bone repair. Finally, we present how aspects of histomorphometric measurements of bone repair can be related to biomechanical and radiographic imaging properties that functionally define rates of bone healing, and thus, how these tools can be used to provide corroborating data. [source] Aged Mice Require Full Transcription Factor, Runx2/Cbfa1, Gene Dosage for Cancellous Bone Regeneration After Bone Marrow Ablation,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2004Kunikazu Tsuji Abstract Runx2 is prerequisite for the osteoblastic differentiation in vivo. To elucidate Runx2 gene functions in adult bone metabolism, we conducted bone marrow ablation in Runx2 heterozygous knockout mice and found that aged (but not young) adult Runx2 heterozygous knockout mice have reduced new bone formation capacity after bone marrow ablation. We also found that bone marrow cells from aged Runx2 heterozygous knockout mice have reduced ALP+ colony-forming potential in vitro. This indicates that full Runx2 dosage is needed for the maintenance of osteoblastic activity in adult mice. Introduction: Null mutation of the Runx2 gene results in total loss of osteoblast differentiation, and heterozygous Runx2 deficiency causes cleidocranial dysplasia in humans and mice. However, Runx2 gene functions in adult bone metabolism are not known. We therefore examined the effects of Runx2 gene function in adult mice with heterozygous loss of the Runx2 gene. Materials and Methods: Bone marrow ablation was conducted in young adult (2.5 ± 0.5 months old) or aged adult (7.5 ± 0.5 months old) Runx2 heterozygous knockout mice and wildtype (WT) littermates. Cancellous bone regeneration was evaluated by 2D ,CT. Results: Although new bone formation was observed after bone marrow ablation in the operated bone marrow cavity of WT mice, such bone formation was significantly reduced in Runx2 heterozygous knockout mice. Interestingly, this effect was observed specifically in aged but not young adult mice. Runx2 heterozygous deficiency in aged mice significantly reduced the number of alkaline phosphatase (ALP)+ cell colonies in the bone marrow cell cultures, indicating a reduction in the numbers of osteoprogenitor cells. Such effects of heterozygous Runx2 deficiency on osteoblasts in vitro was specific to the cells from aged adult mice, and it was not observed in the cultures of marrow cells from young adult mice. Conclusion: These results indicate that full gene dosage of Runx2 is required for cancellous bone formation after bone marrow ablation in adult mice. [source] Ex vivo bone morphogenetic protein-2 gene delivery using gingival fibroblasts promotes bone regeneration in ratsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 3 2010Joong-Ho Shin Shin J-H, Kim K-H, Kim S-H, Koo K-T, Kim T-I, Seol Y-J, Ku Y, Rhyu I-C, Chung C-P, Lee Y-M. Ex vivo bone morphogenetic protein-2 gene delivery using gingival fibroblasts promotes bone regeneration in rats. J Clin Periodontol 2009; 37: 305,311. doi: 10.1111/j.1600-051X.2009.01522.x. Abstract Aim: The aim of the present study was to investigate bone regeneration following ex vivo bone morphogenetic protein-2 (BMP-2) gene delivery using human gingival fibroblasts (HGFs) in rat calvarial defects. Materials and Methods: An 8 mm craniotomy defect was created in Sprague,Dawley rats. The animals were divided into four groups: (1) non-grafted group, the defect was left empty; (2) collagen matrix group, the defect was filled with collagen matrix only; (3) HGF group, the defect was filled with non-transduced HGFs on collagen matrix; (4) BMP-2/HGF group, the defect was filled with BMP-2 gene-transduced HGFs on collagen matrix. Animals were sacrificed at 2 and 4 weeks after surgery, and micro-computed tomographic and histologic observations were performed. Results: The BMP-2/HGF group showed promoted osseous healing of calvarial defects, as compared with the other groups. At both 2 and 4 weeks, regenerated bone area was significantly greater in the BMP-2/HGF group than the other three groups. Quite a few number of transplanted HGFs were observed within the regenerated bone tissues. Conclusions: The results of this study suggest that ex vivo BMP-2 gene delivery induces prominent bone regeneration in vivo and HGFs may be useful as target cells for ex vivo gene therapy. [source] Bone regeneration in dehiscence-type defects at chemically modified (SLActive®) and conventional SLA titanium implants: a pilot study in dogsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2007Frank Schwarz Abstract Objectives: The aim of the present study was to evaluate bone regeneration in dehiscence-type defects at titanium implants with chemically modified (mod) and conventional sand-blasted/acid-etched (SLA) surfaces. Material and Methods: Standardized buccal dehiscence defects (height: 3 mm, width: 3 mm) were surgically created following implant site preparation in both the upper and lower jaws of four beagle dogs. modSLA and SLA implants were inserted bilaterally according to a split-mouth design. The animals were sacrificed after 2 and 12 weeks (n=2 animals each). Dissected blocks were processed for histomorphometrical analysis: defect length, new bone height (NBH), percent linear fill (PLF), percent of bone-to-implant contact (BIC-D) and area of new bone fill (BF). Results: Wound healing at SLA implants was predominantly characterized by the formation of a dense connective tissue at 2 and 12 weeks, without significant increases in mean NBH, PLF, BIC-D or BF values. In contrast, modSLA implants exhibited a complete defect fill at 12 weeks following implant placement. In particular, histomorphometrical analysis revealed the following mean values at 12 weeks: NBH (3.2±0.3 mm), PLF (98%), BIC-D (82%) and BF (2.3±0.4 mm2). Conclusion: Within the limits of the present study, it was concluded that modSLA titanium surfaces may promote bone regeneration in acute-type buccal dehiscence defects at submerged implants. [source] Management of inter-dental/inter-implant papillaJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2005Laura Zetu Abstract Objectives: The aims of this paper are to review and compare existing techniques for creation of interdental/interimplant papillae, to address factors that may influence its appearance and to present an approach that authors developed that could help clinicians to manage and recreate the interproximal papillae. Methods: Papers related to interdental and interimplant papillae published over the last 30 years were selected and analyzed. Results: Thorough treatment planning is essential for maintenance of the height of the interproximal papillae following tooth removal. The key for achieving an esthetically pleasing outcome is the clinicians' ability of properly managing/creating interdental/interimplant papillae. Bone support is the foundation for any soft tissue existence, techniques such as socket augmentation, orthodontic extrusion, guided bone regeneration, onlay graft and distraction osteogenesis are often used for this purpose. Soft tissue grafts as well as esthetic mimic restorations can also be used to enhance the esthetic outcomes. Conclusions: An esthetic triangle is developed to address the foundations that are essential for maintaining/creating papilla. These include adequate bone volume, proper soft tissue thickness as well as esthetic appearing restorations. [source] Healing patterns in calvarial bone defects following guided bone regeneration in ratsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 9 2002A micro-CT scan analysis Abstract Objective: The objective of this study was to evaluate healing patterns of critical-size calvarial bone defects treated according to principles of guided bone regeneration using micro-CT scan analysis. Specifically, the contribution of bone, periosteum and dura mater to the amount and mineralization of newly formed bone was evaluated. Material and Methods: Surgically induced, critical-size calvarial bone defects in 48 adult male Wistar rats received the following: an occlusive expanded polytetrafluoroethylene (ePTFE) membrane at the exo- and endocranial aspect (OO; n = 12); an occlusive membrane at the exocranial and a perforated membrane at the endocranial aspect (OP; n = 12); a perforated membrane at the exocranial and an occlusive membrane at the endocranial aspect (PO; n = 12); and a perforated membrane at the exo- and endocranial aspect (PP; n = 12). The animals were euthanized at 4 weeks for quantitative analysis of bone volume fraction and mineralization in the region of interest (ROI) as well as in the external, middle and central area of the defect using micro-CT. Results: Bone volume fraction ranged from 31.4% (OP) to 24.5% (PP). No differences were found among the groups. Bone volume fraction and mineralization in the middle area were significantly greater in group OP than in group PP, and in the central area in group OO and PO than in group PP. Conclusions: The results of this study suggest that use of occlusive ePTFE membranes enhances bone formation and maturation in the calvarial skeleton. When occlusion of endo- and exocranial tissues was compromised by membrane perforation, impaired bone formation and mineralization were observed. [source] Recombinant human platelet-derived growth factor BB (rhPDGF-BB) and beta-tricalcium phosphate/collagen matrix enhance fracture healing in a diabetic rat modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2009Loay Al-Zube Abstract Diabetes mellitus is a common systemic disease that has been associated with poor fracture healing outcomes. The mechanism through which diabetes impairs bone regeneration is unknown. One possible mechanism may be related to either decreased or uncoordinated release of local growth factors at the fracture site. Indeed, previous studies have found reduced platelet-derived growth factor (PDGF) levels in the fracture callus of diabetic rats, suggesting that local application of PDGF may overcome the negative effects of diabetes and promote fracture healing. To test this hypothesis, low (22 µg) and high (75 ug) doses of recombinant human PDGF-BB (rhPDGF-BB) were applied directly to femur fracture sites in BB Wistar diabetic rats that were then compared to untreated or vehicle-treated animals. rhPDGF-BB treatment significantly increased early callus cell proliferation compared to that in control specimens. Low dose rhPDGF-BB treatment significantly increased callus peak torque values (p,<,0.05) at 8 weeks after fracture as compared to controls. High dose rhPDGF-BB treatment increased callus bone area at 12 weeks postfracture. These data indicate that rhPDGF-BB treatment ameliorates the effects of diabetes on fracture healing by promoting early cellular proliferation that ultimately leads to more bone formation. Local application of rhPDGF-BB may be a new therapeutic approach to treat diabetes-impaired fracture healing. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 1074,1081, 2009 [source] A new animal model for bone atrophic nonunion: Fixation by external fixatorJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 12 2008Katharina Kaspar Abstract A new small animal model of bone atrophic nonunion was established for investigating the process of bone regeneration by performing cauterization of the periosteum, removal of the local bone marrow, and stabilization with external fixation. The model allows the creation of an atrophic nonunion without the need for a critical size defect. Furthermore, it provides reproducible, well-defined mechanical conditions and minimized physical interference of the implant with the biological processes in the healing zone. Eighty adult Sprague-Dawley rats received an osteotomy of the left femur, stabilized with an external fixator. In half of the animals, the periosteum proximal and distal to the osteotomy was destroyed by cauterization and the adjacent bone marrow was removed (nonunion group). At 2 and 8 weeks after surgery, radiological, biomechanical, histological, and histomorphometrical analyses showed a typical physiological healing in the control group, while the nonunion group was characterized by resorption of the bone ends with some callus formation distant to the osteotomy. At both time points, the callus was composed of significantly less bone and significantly more connective tissue (p,<,0.001). In addition, the torsional strength of the osteotomized femur was significantly less in the nonunion group than in the control group, which was comparable to that of the intact femur (p,<,0.001). In conclusion, the present model allows the induction of an atrophic nonunion without the need of a critical size defect. It is reproducible, provides standardized biomechanical conditions, and allows minimized interaction of the implant with the healing zone. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Cellular and molecular characterization of a murine non-union modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2004P. Choi Abstract Purpose. We have developed a method to study the molecular and cellular events underlying delayed skeletal repair in a model that utilizes distraction osteogenesis. Methods. The clinical states of delayed union and non-union were reproduced in this murine model by altering distraction parameters such as the inclusion and exclusion of a latency phase and variations in the rate and rhythm of distraction. Radiographic, cellular, and molecular analyses were performed on the distraction tissues. Results. Eliminating the latency period delayed bony union, but did not appreciably alter the extent of platelet endothelial cell adhesion marker (PECAM) immunostaining. Following elimination of a latency phase and a threefold increase in the rate of distraction, there was a further delay in bone regeneration and a higher rate of non-union (60%). Instead of bone, the distraction gap was comprised of adipose or fibrous tissue. Once again, despite the rigorous distraction protocol, we detected equivalent PECAM staining within the distraction gap. In a minority of cases, cartilage and osseous tissues occupied the distraction gap likely by a prolonged process of endochondral ossification. Conclusions. Here, we have altered the mechanical environment in such a way to reproducibly create delays in skeletal regeneration. These delays in skeletal tissue regeneration appear to develop even in the presence of endothelial cells, which suggests that mechanisms other than a disruption to the vascular network can account for some cases of non-union. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Platelets are mitogenic for periosteum-derived cellsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2003Reinhard Gruber Abstract The early stages of bone regeneration are associated with a high mitogenic activity of periosteal cells. Here we addressed the question of whether platelets that accumulate within the developing haematoma can account for this tissue response. Addition of platelets, platelet-released supernatants, platelet membranes, and microparticles to bovine periosteum-derived cells resulted in an increase in 3H-thymidine incorporation; lipid extracts had no effect. Platelet-released supernatants retained their activity after incubation at 56°C, but not at 100°C. Gel chromatographic analysis revealed the highest mitogenic activity at approximately 35 kD. Of the factors released from activated platelets, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) increased 3H-thymidine incorporation. The mitogenic activity of platelet-released supernatants was decreased by anti-PDGF, and anti-bFGF antibodies. Platelet-released supernatants increased the number of proliferating periosteum-derived cells as determined by the expression pattern of Ki67. Platelet-released supernatants also resulted in a stimulation of cell proliferation in periosteal explants. These results suggest that platelets have the potential to stimulate the mitogenic response of the periosteum during bone repair. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Molecular aspects of healing in stabilized and non-stabilized fracturesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2001A. X. Le Bone formation is a continuous process that is initiated during fetal development and persists in adults in the form of bone regeneration and remodeling. These latter two aspects of bone formation are clearly influenced by the mechanical environment. In this study we tested the hypothesis that alterations in the mechanical environment regulate the program of mesenchymal cell differentiation, and thus the formation of a cartilage or bony callus, at the site of injury. As a first step in testing this hypothesis we produced stabilized and non-stabilized tibial fractures in a mouse model, then used molecular and cellular methods to examine the stage of healing. Using the "molecular map" of the fracture callus, we divided our analyzes into three phases of fracture healing: the inflammatory or initial phase of healing, the soft callus or intermediate stage, and the hard callus stage. Our results show that indian hedgehog(ihh), which regulates aspects of chondrocyte maturation during fetal and early postnatal skeletogenesis, was expressed earlier in an non-stabilized fracture callus as compared to a stabilized callus, ihh persisted in the non-stabilized fracture whereas its expression was down-regulated in the stabilized bone. IHH exerts its effects on chondrocyte maturation through a feedback loop that may involve bone morphogenetic protein 6 [bmp6; (S. Pathi, J.B. Rutenberg, R.L. Johnson, A. Vortkamp, Developmental Biology 209 (1999) 239,253)] and the transcription factor gli3, bmp6 and gli3 were re-induced in domain adjacent to the ihh -positive cells during the soft and hard callus stages of healing. Thus, stabilizing the fracture, which circumvents or decreases the cartilaginous phase of bone repair, correlates with a decrease in ihh signaling in the fracture callus. Collectively, our results illustrate that the ihh signaling pathway participates in fracture repair, and that the mechanical environment affects the temporal induction of ihh, bmp6 and gli3. These data support the hypothesis that mechanical influences affect mesenchymal cell differentiation to bone. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] | ||||||||||||||||