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Schofer MD, Roessler PP, Schaefer J, Theisen C, Schlimme S, Heverhagen JT, Voelker M, Dersch R, Agarwal S, Fuchs-Winkelmann S, Paletta JRJ. Electrospun PLLA nanofiber scaffolds and their use in combination with BMP-2 for reconstruction of bone defects. PLoS One 2011; 6:e25462. [PMID: 21980467 PMCID: PMC3182232 DOI: 10.1371/journal.pone.0025462] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 09/05/2011] [Indexed: 01/14/2023] Open
Abstract
INTRODUCTION Adequate migration and differentiation of mesenchymal stem cells is essential for regeneration of large bone defects. To achieve this, modern graft materials are becoming increasingly important. Among them, electrospun nanofiber scaffolds are a promising approach, because of their high physical porosity and potential to mimic the extracellular matrix (ECM). MATERIALS AND METHODS The objective of the present study was to examine the impact of electrospun PLLA nanofiber scaffolds on bone formation in vivo, using a critical size rat calvarial defect model. In addition we analyzed whether direct incorporation of bone morphogenetic protein 2 (BMP-2) into nanofibers could enhance the osteoinductivity of the scaffolds. Two critical size calvarial defects (5 mm) were created in the parietal bones of adult male Sprague-Dawley rats. Defects were either (1) left unfilled, or treated with (2) bovine spongiosa, (3) PLLA scaffolds alone or (4) PLLA/BMP-2 scaffolds. Cranial CT-scans were taken at fixed intervals in vivo. Specimens obtained after euthanasia were processed for histology, histomorphometry and immunostaining (Osteocalcin, BMP-2 and Smad5). RESULTS PLLA scaffolds were well colonized with cells after implantation, but only showed marginal ossification. PLLA/BMP-2 scaffolds showed much better bone regeneration and several ossification foci were observed throughout the defect. PLLA/BMP-2 scaffolds also stimulated significantly faster bone regeneration during the first eight weeks compared to bovine spongiosa. However, no significant differences between these two scaffolds could be observed after twelve weeks. Expression of osteogenic marker proteins in PLLA/BMP-2 scaffolds continuously increased throughout the observation period. After twelve weeks osteocalcin, BMP-2 and Smad5 were all significantly higher in the PLLA/BMP-2 group than in all other groups. CONCLUSION Electrospun PLLA nanofibers facilitate colonization of bone defects, while their use in combination with BMP-2 also increases bone regeneration in vivo and thus combines osteoconductivity of the scaffold with the ability to maintain an adequate osteogenic stimulus.
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Affiliation(s)
- Markus D. Schofer
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
| | - Philip P. Roessler
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
| | - Jan Schaefer
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
| | - Christina Theisen
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
| | - Sonja Schlimme
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
| | | | - Maximilian Voelker
- Department of Diagnostic Radiology, University Hospital Marburg, Marburg, Germany
| | - Roland Dersch
- Department of Macromolecular Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Seema Agarwal
- Department of Macromolecular Chemistry, Philipps-University Marburg, Marburg, Germany
| | | | - Jürgen R. J. Paletta
- Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany
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Kim BJ, Kwon TK, Baek HS, Hwang DS, Kim CH, Chung IK, Jeong JS, Shin SH. A comparative study of the effectiveness of sinus bone grafting with recombinant human bone morphogenetic protein 2-coated tricalcium phosphate and platelet-rich fibrin-mixed tricalcium phosphate in rabbits. Oral Surg Oral Med Oral Pathol Oral Radiol 2011; 113:583-92. [PMID: 22676983 DOI: 10.1016/j.tripleo.2011.04.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 04/06/2011] [Accepted: 04/24/2011] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The objective of this histologic study was to evaluate platelet-rich fibrin (PRF)-mixed tricalcium phosphate (TCP) and recombinant human bone morphogenic protein 2 (rhBMP-2)-coated TCP in their potential to enhance bone regeneration in sinus elevation in rabbits as well as in their inflammatory features. STUDY DESIGN Bilateral round-shaped defects (diameter 8.0 mm) were formed in the maxillary anterior sinus walls of 36 New Zealand white rabbits. The defects were grafted with TCP only (control group), with rhBMP-2-coated TCP (experimental group A) and with PRF-mixed TCP (experimental group B). Each group included 12 rabbits. The animals were killed at 3 days, 1 week, 2 weeks, 4 weeks, 6 weeks, and 8 weeks. The specimens underwent decalcification and were stained for histologic analysis. RESULTS There were no significant differences in inflammatory features among the groups at 3 days or the first week after operation. In a histomorphometric analysis, the new bone formation ratio showed significant differentiation between groups A and B. The TCP-only control group showed a relatively lower bone formation ratio rather than the experimental groups. The PRF-mixed TCP group showed a larger bone formation area, compared with both the control group and group A. CONCLUSIONS In the results of the histologic evaluation (hematoxylin-eosin, Masson trichrome stain), the experimental groups A and B showed rapid bone formation, remodeling, and calcification in the second week. Moreover, there was a significant difference between those experimental groups and the control group in the new bone formation area at the fourth, sixth, and eighth weeks. The PRF-mixed TCP showed more rapid bone healing than the rhBMP-2-coated TCP or the TCP-only control.
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Affiliation(s)
- Bok-Joo Kim
- Department of Oral and Maxillofacial Surgery, Dong-A University Medical Center, Busan, Korea
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Srouji S, Ben-David D, Lotan R, Livne E, Avrahami R, Zussman E. Slow-Release Human Recombinant Bone Morphogenetic Protein-2 Embedded Within Electrospun Scaffolds for Regeneration of Bone Defect: In Vitro and In Vivo Evaluation. Tissue Eng Part A 2011; 17:269-77. [DOI: 10.1089/ten.tea.2010.0250] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Samer Srouji
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel
- Department of Oral and Maxillofacial Surgery, Carmel Medical Center, Haifa, Israel
| | - Dror Ben-David
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel
| | - Rona Lotan
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel
| | - Erella Livne
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel
| | - Ron Avrahami
- Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Haifa Israel
| | - Eyal Zussman
- Faculty of Mechanical Engineering, Technion—Israel Institute of Technology, Haifa Israel
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Min CK, Wikesjö UME, Park JC, Chae GJ, Pippig SD, Bastone P, Kim CS, Kim CK. Wound healing/regeneration using recombinant human growth/differentiation factor-5 in an injectable poly-lactide-co-glycolide-acid composite carrier and a one-wall intra-bony defect model in dogs. J Clin Periodontol 2011; 38:261-8. [DOI: 10.1111/j.1600-051x.2010.01691.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Wojtowicz AM, Templeman KL, Hutmacher DW, Guldberg RE, García AJ. Runx2 overexpression in bone marrow stromal cells accelerates bone formation in critical-sized femoral defects. Tissue Eng Part A 2010; 16:2795-808. [PMID: 20412027 DOI: 10.1089/ten.tea.2010.0025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The repair of large nonunions in long bones remains a significant clinical problem due to high failure rates and limited tissue availability for auto- and allografts. Many cell-based strategies for healing bone defects deliver bone marrow stromal cells (BMSCs) to the defect site to take advantage of the inherent osteogenic capacity of this cell type. However, many factors, including donor age and ex vivo expansion of the cells, cause BMSCs to lose their differentiation ability. To overcome these limitations, we have genetically engineered BMSCs to constitutively overexpress the osteoblast-specific transcription factor Runx2. In the present study, we examined Runx2-modified BMSCs, delivered via polycaprolactone scaffolds loaded with type I collagen meshes, in critical-sized segmental defects in rats compared to unmodified cells, cell-free scaffolds, and empty defects. Runx2 expression in BMSCs accelerated healing of critical-sized defects compared to unmodified BMSCs and defects receiving cell-free treatments. These findings provide an accelerated method for healing large bone defects, which may reduce recovery time and the need for external fixation of critical-sized defects.
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Affiliation(s)
- Abigail M Wojtowicz
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA
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Kim IS, Lee EN, Cho TH, Song YM, Hwang SJ, Oh JH, Park EK, Koo TY, Seo YK. Promising efficacy of Escherichia coli recombinant human bone morphogenetic protein-2 in collagen sponge for ectopic and orthotopic bone formation and comparison with mammalian cell recombinant human bone morphogenetic protein-2. Tissue Eng Part A 2010; 17:337-48. [PMID: 20868206 DOI: 10.1089/ten.tea.2010.0408] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Nonglycosylated recombinant human bone morphogenetic protein (rhBMP)-2 prepared in Escherichia coli (E. coli rhBMP-2) has recently been considered as an alternative to mammalian cell rhBMP-2. However, its clinical use is still limited owing to lack of evidence for osteogenic activity comparable with that of mammalian cell rhBMP-2 via microcomputed tomography-based analysis. Therefore, this study aimed to evaluate the ability of E. coli rhBMP-2 in absorbable collagen sponge to form ectopic and orthotopic bone and to compare it to that of mammalian rhBMP-2. In vitro investigation was performed to study osteoblast differentiation of human mesenchymal stromal cells. Both types of rhBMP-2 enhanced proliferation, alkaline phosphatase activity, and matrix mineralization of human mesenchymal stromal cells at similar levels. Similar tendencies were observed in microcomputed tomography analysis, which determined bone volume, fractional bone volume, trabecular thickness, trabecular separation, bone mineral density, and other characteristics. Histology from an in vivo osteoinductivity test and from a rat calvarial defect model demonstrated a dose-dependent increase in local bone formation. The E. coli rhBMP-2 group (5 μg) not only induced complete regeneration of an 8-mm critical-sized defect at 4 weeks, but also led to new bone with the same bone mineral density as normal bone at 8 weeks, with the same efficiency as that of mammalian cell rhBMP-2 (5 μg). These uniformly favorable results provide evidence that the osteogenic activity of E. coli rhBMP-2 is not inferior to that of mammalian cell rhBMP-2 despite its low solubility and lack of gylcosylation. These results suggest that the application of E. coli rhBMP-2 in absorbable collagen sponge may be a promising equivalent to mammalian cell rhBMP-2 in bone tissue engineering.
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Affiliation(s)
- In Sook Kim
- Dental Research Institute, Seoul National University, Seoul, Republic of Korea
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Jungbluth P, Wild M, Grassmann JP, Ar E, Sager M, Herten M, Jäger M, Becker J, Windolf J, Hakimi M. Platelet-rich plasma on calcium phosphate granules promotes metaphyseal bone healing in mini-pigs. J Orthop Res 2010; 28:1448-55. [PMID: 20872580 DOI: 10.1002/jor.21152] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The role of platelet-rich plasma (PRP) as a promoter of bone healing remains controversial. The aim of this study was to investigate the effect of PRP in combination with calcium phosphate granules (CPG) on bone defect healing in a metaphyseal long bone defect. A metaphyseal bone defect at the proximal tibia of 16 mini-pigs was filled with CPG combined with autologous PRP or CPG solely (control group). The PRP showed 4.4-fold more platelets compared to peripheral blood. Six weeks after surgery the radiological and histomorphometrical evaluations showed significantly more bone formation in the PRP group in the central area of the defect zone (p < 0.01) as well as the cortical defect zone (p < 0.04). Furthermore, the resorption rate of CPG was increased in animals who received PRP. Nevertheless there were only isolated instances of complete osseous bridging of the bone defects even in the PRP group. This study demonstrates that a PRP-CPG composit promotes bone regeneration but does not lead to a solid fusion of a tibial defect in mini-pigs.
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Affiliation(s)
- Pascal Jungbluth
- Department of Trauma and Handsurgery, Heinrich Heine University Hospital Duesseldorf, Moorenstr 5, 40225 Duesseldorf, Germany
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Bone morphogenetic protein binding peptide mechanism and enhancement of osteogenic protein-1 induced bone healing. Spine (Phila Pa 1976) 2010; 35:2049-56. [PMID: 20581758 DOI: 10.1097/brs.0b013e3181cc0220] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN In vitro and in vivo evaluation of BBP interactions with BMP. OBJECTIVE To explore bone morphogenetic protein-binding peptide (BBP)'s mechanism of action, investigate an extended repertoire for BBP applications, and evaluate the usefulness of BBP as a surgical adjuvant when used with recombinant human osteogenic protein-1 (rhOP-1). SUMMARY OF BACKGROUND DATA Bone morphogenetic proteins (BMPs) are osteoinductive proteins that provide a potential alternative to autograft. Their utility is limited by cost, and potential dose-dependent risks, such as local inflammatory reactions and ectopic bone formation. BBP, a cyclized synthetic peptide, avidly binds recombinant human BMP-2(rhBMP-2) and has been shown to accelerate and enhance its osteogenic qualities. METHODS BBP binding with 4 growth factors from the transforming growth factor -beta family were assessed using surface plasmon resonance. The in vivo retention of rhBMP-2 was quantified by comparing the percentage of retained [¹²⁵I]-labeled rhBMP-2 in absorbable collagen sponge implants with or without BBP at 1, 3, and 7 days postimplantation. The adjunctive effect of BBP with rhOP-1-induced bone growth was evaluated by comparing time to fusion and fusion rates in a rodent posterolateral fusion model with 2 different doses of rhOP-1 with or without BBP. RESULTS BBP bound all 4 growth factors with an intermediate affinity. The in vivo retention of rhBMP-2 alone ranged from about 40% on day 1 to about 30% on day 7, whereas, the retention of rhBMP-2 in the presence of BBP was about 85% on day 1 and about 55% on day 7. The addition of BBP to rhOP-1 resulted in significantly earlier and greater fusion rates than achieved with rhOP-1 alone. CONCLUSION The mechanism of the BBP enhanced osteoinductive properties of BMPs involves the binding and retention of the growth factor, resulting in a prolonged exposure of BMP to the desired fusion site. The use of BBP in conjunction with BMPs may prove to provide satisfactory fusion outcomes, while reducing the costs and side effects associated with BMP use.
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Bessa PC, Balmayor ER, Hartinger J, Zanoni G, Dopler D, Meinl A, Banerjee A, Casal M, Redl H, Reis RL, van Griensven M. Silk Fibroin Microparticles as Carriers for Delivery of Human Recombinant Bone Morphogenetic Protein-2: In Vitro and In Vivo Bioactivity. Tissue Eng Part C Methods 2010; 16:937-45. [DOI: 10.1089/ten.tec.2009.0486] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Paulo César Bessa
- 3B's Research Group—Biomaterials, Biodegradables, and Biomimetics, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, University of Minho, Guimarães, Portugal
- PT Associated Laboratory, IBB—Institute for Biotechnology and Bioengineering, Guimarães, Portugal
- CBMA—Centre of Molecular and Environment Biology, University of Minho, Braga, Portugal
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Elizabeth R. Balmayor
- 3B's Research Group—Biomaterials, Biodegradables, and Biomimetics, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, University of Minho, Guimarães, Portugal
- PT Associated Laboratory, IBB—Institute for Biotechnology and Bioengineering, Guimarães, Portugal
| | - Joachim Hartinger
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Gerald Zanoni
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Daniela Dopler
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Alexandra Meinl
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Bernhard Gottlieb University School of Dentistry, Vienna, Austria
| | - Asmita Banerjee
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Margarida Casal
- CBMA—Centre of Molecular and Environment Biology, University of Minho, Braga, Portugal
| | - Heinz Redl
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Rui L. Reis
- 3B's Research Group—Biomaterials, Biodegradables, and Biomimetics, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, University of Minho, Guimarães, Portugal
- PT Associated Laboratory, IBB—Institute for Biotechnology and Bioengineering, Guimarães, Portugal
| | - Martijn van Griensven
- Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, AUVA Research Center, Austrian Cluster for Tissue Regeneration, Vienna, Austria
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Seib FP, Lanfer B, Bornhäuser M, Werner C. Biological activity of extracellular matrix-associated BMP-2. J Tissue Eng Regen Med 2010; 4:324-7. [PMID: 20014079 DOI: 10.1002/term.240] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The critical requirement for matrix-associated bone morphogenetic proteins (BMPs) during induction of bone formation in vivo has long been recognized. However, the role of extracellular matrix (ECM) physisorbed BMPs in inducing the differentiation of resident mesenchymal stem cells into osteoblasts has been ill-defined. We therefore used BMP-responsive C2C12s to study the biological activity of collagen type I physisorbed BMP-2. Fibrillar collagen type I scaffolds were loaded with 75 ng BMP-2/microg collagen. Under cell culture conditions, 40% of loaded (125)I-labelled BMP-2 was released within 24 h, whereas the remaining BMP-2 was stably physisorbed for > 7 days. Using these systems suggested that physisorbed BMP-2 is more active than diffusible BMP-2. Thus, the current clinical practice of immobilizing BMPs on collagen type I scaffolds not only prolongs local delivery of the morphogen but could also enhance biological activity at the cellular level.
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Affiliation(s)
- F Philipp Seib
- Leibniz Institute for Polymer Research, Max Bergmann Centre for Biomaterials, Dresden, Germany
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Asamura S, Mochizuki Y, Yamamoto M, Tabata Y, Isogai N. Bone regeneration using a bone morphogenetic protein-2 saturated slow-release gelatin hydrogel sheet: evaluation in a canine orbital floor fracture model. Ann Plast Surg 2010; 64:496-502. [PMID: 20224349 DOI: 10.1097/sap.0b013e31819b6c52] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bone regeneration methods using bone inductive cytokines show promise, however, due to early diffusion and absorption of single applications of these cytokines, the bone inductive effects are limited. In this study, such a system was applied, using gelatin hydrogel as a carrier to slowly release (bone morphogenetic proteins) BMP-2 over a relatively long period in vivo. By coupling this slow-release system with a biodegradable copolymer, this composite was evaluated by grafting into bone defect sites of a canine orbital floor fracture model. Radio-iodinated BMP-2 incorporated into the gelatin hydrogel carrier and subcutaneously implanted into nude mice showed a similar slow release (approximately, 60% at 3 days and 80% at 14 days) as the radiolabeled hydrogel carrier alone. In contrast, greater than 90% of fluid-injected BMP-2 was lost in the injection site within the first 8 hours. Using a dog model of orbital floor fracture, a complex of BMP-2-saturated gelatin hydrogel and a polylactide-based biodegradable copolymer was implanted into the orbital bone defect. Bone structural analysis, using radiography, histologic examination, and microfocus CT, showed greatly enhanced new bone formation and defect healing at 5 weeks in comparison to implanted biodegradable copolymer directly saturated with the same amount of BMP-2 (no slow-release hydrogel carrier). A trabecular structure resembling that normal bone tissue was restored in the new bone tissue generated by the slow-release constructs. Thus study demonstrates the potential of slow-release BMP-2 for bone healing of difficult defects.
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Affiliation(s)
- Shinichi Asamura
- Department of Plastic and Reconstructive Surgery, Kinki University School of Medicine, Osaka, Japan.
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Abstract
Aim The aim of the present review was to characterize the potential of different biomaterials as carriers for bone growth factors. Introduction Beyond mechanical and structural characteristics, one of the features that account for a potential carrier is the possibility to couple growth factor molecules to it. As simple adsorption of the growth factor to the carrier surface by soak loading produces a burst release of growth factors with rapid decrease of biological activity, the ability to accomplish controlled release of functional growth factor molecules is one of the crucial characteristics for an appropriate carrier material. Conclusion The variety of carrier materials requires different strategies to either couple growth factors to the material surface or to incorporate them into the carrier matrix. The present review outlines current technical approaches and discusses future trends in the use of carrier materials for bone growth factors.
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Sohier J, Daculsi G, Sourice S, de Groot K, Layrolle P. Porous beta tricalcium phosphate scaffolds used as a BMP-2 delivery system for bone tissue engineering. J Biomed Mater Res A 2010; 92:1105-14. [PMID: 19301273 DOI: 10.1002/jbm.a.32467] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Macroporous beta tricalcium phosphate (beta-TCP) scaffolds were evaluated as potential carriers and delivery systems for bone morphogenetic protein-2 (BMP-2). Chemical etching was performed to increase the available surface and thus the protein loading. X-ray diffraction and infrared spectrocopy analyses confirmed the preparation of pure beta-TCP scaffolds. Scanning electron microscopy revealed interconnected porosity (64%) and a microporous surface after chemical etching. Scaffolds loaded with 30 and 15 microg of BMP-2 were implanted respectively into the back muscles and into femoral defects (condyle and diaphysis) of rabbits for 4 weeks. Histological observations confirmed the activity of the BMP-2 released from the scaffolds. Intramuscularly, bone was formed within the BMP-2-loaded scaffold pores. In the bone defects, the effect of released BMP-2 was similarly noticeable, as evaluated by histomorphometry. The incorporation of BMP-2 resulted in an amount of newly formed bone that was 1.3 times higher than with unloaded scaffolds. The implant site, however, did not have an effect on bone formation as no statistical differences were measured between cortical (diaphysis) and trabecular (condyle) defects. These results indicate the suitability of chemically etched beta-TCP scaffolds as BMP-2 carriers, in the context of bone regeneration.
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Affiliation(s)
- Jérôme Sohier
- Inserm, U791, Laboratory for Osteo-Articular and Dental Tissue Engineering, Faculty of Dental Surgery, University of Nantes, Nantes, France
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Wang Y, Zhang L, Hu M, Wen W, Xiao H, Niu Y. Effect of chondroitin sulfate modification on rhBMP-2 release kinetics from collagen delivery system. J Biomed Mater Res A 2010; 92:693-701. [PMID: 19263491 DOI: 10.1002/jbm.a.32190] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Protein delivery systems focus on protecting the protein that directly affects release kinetics. This study was carried out to determine the effect of surface polar group and fiber structure in a recombinant human bone morphogenetic protein-2 (rhBMP-2) protecting system based on a collagen matrix on its pharmacokinetics (PK) and osteoinductive activity In this study, two types of collagen carriers were made for rhBMP-2 protecting system. The PKs of rhBMPs within collagen (Col) and collagen-chondroitin sulfate (Col-CS) carriers were determined using (125)I-labeled proteins in rat ectopic assay. The two carriers were characterized with surface energy and hydrophilicity. We observed that the osteoinductivity of these two scaffolds seemed to depend on two parameters: the nature of the carrier material and the release kinetics of the carriers. Results indicated that with CS modification, the initial burst release of rhBMP-2 from Col-CS scaffold was much higher than collagen scaffold. The subsequent PKs at longer times were not strongly dependent on the carriers. These differences were expected to affect the osteoinductive activity of the implants. It was concluded that surface energy played a significant role in the release PK of implanted rhBMP and higher initial burst is favorable to bone regeneration near the matrix.
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Affiliation(s)
- Yan Wang
- Department of Orthopaedics, Chinese PLA General Hospital, Beijing 100853, People's Republic of China
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Facca S, Cortez C, Mendoza-Palomares C, Messadeq N, Dierich A, Johnston APR, Mainard D, Voegel JC, Caruso F, Benkirane-Jessel N. Active multilayered capsules for in vivo bone formation. Proc Natl Acad Sci U S A 2010; 107:3406-11. [PMID: 20160118 PMCID: PMC2840428 DOI: 10.1073/pnas.0908531107] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interest in the development of new sources of transplantable materials for the treatment of injury or disease has led to the convergence of tissue engineering with stem cell technology. Bone and joint disorders are expected to benefit from this new technology because of the low self-regenerating capacity of bone matrix secreting cells. Herein, the differentiation of stem cells to bone cells using active multilayered capsules is presented. The capsules are composed of poly-L-glutamic acid and poly-L-lysine with active growth factors embedded into the multilayered film. The bone induction from these active capsules incubated with embryonic stem cells was demonstrated in vitro. Herein, we report the unique demonstration of a multilayered capsule-based delivery system for inducing bone formation in vivo. This strategy is an alternative approach for in vivo bone formation. Strategies using simple chemistry to control complex biological processes would be particularly powerful, as they make production of therapeutic materials simpler and more easily controlled.
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Affiliation(s)
- S. Facca
- a: Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 977, Faculté de Médecine, 11 rue Humann, 67085 Strasbourg Cedex, France, b: Faculté de Chirurgie Dentaire Université de Strasbourg (UdS), 1 place de l’hôpital, 67084, Strasbourg, France
| | - C. Cortez
- Center for Nanoscience and Nanotechnology, Department of Chemical and Bimolecular Engineering, University of Melbourne, Victoria 3010, Australia
| | - C. Mendoza-Palomares
- a: Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 977, Faculté de Médecine, 11 rue Humann, 67085 Strasbourg Cedex, France, b: Faculté de Chirurgie Dentaire Université de Strasbourg (UdS), 1 place de l’hôpital, 67084, Strasbourg, France
| | - N. Messadeq
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Institut Clinique de la Souris (ICS), Centre National de la Recherche Scientifique (CNRS)/Institut National de la Santé et de la Recherche Médicale INSERM/UdS, Collège de France, BP 10142, Strasbourg, France
| | - A. Dierich
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Institut Clinique de la Souris (ICS), Centre National de la Recherche Scientifique (CNRS)/Institut National de la Santé et de la Recherche Médicale INSERM/UdS, Collège de France, BP 10142, Strasbourg, France
| | - A. P. R. Johnston
- Center for Nanoscience and Nanotechnology, Department of Chemical and Bimolecular Engineering, University of Melbourne, Victoria 3010, Australia
| | - D. Mainard
- Unité Mixte de Recherches 7561, Center National de la Recherche Scientifique-Université de Nancy, Faculté de Médecine, Vandoeuvre les Nancy, France; and
- Center Hospitalier Universtaire de Nancy, Hôpital Central (service d’orthopédie) 29 Avenue du Maréchal de Lattre de Tassigny, 54000 Nancy, France
| | - J.-C. Voegel
- a: Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 977, Faculté de Médecine, 11 rue Humann, 67085 Strasbourg Cedex, France, b: Faculté de Chirurgie Dentaire Université de Strasbourg (UdS), 1 place de l’hôpital, 67084, Strasbourg, France
| | - F. Caruso
- Center for Nanoscience and Nanotechnology, Department of Chemical and Bimolecular Engineering, University of Melbourne, Victoria 3010, Australia
| | - N. Benkirane-Jessel
- a: Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 977, Faculté de Médecine, 11 rue Humann, 67085 Strasbourg Cedex, France, b: Faculté de Chirurgie Dentaire Université de Strasbourg (UdS), 1 place de l’hôpital, 67084, Strasbourg, France
- Center for Nanoscience and Nanotechnology, Department of Chemical and Bimolecular Engineering, University of Melbourne, Victoria 3010, Australia
- Center Hospitalier Universtaire de Nancy, Hôpital Central (service d’orthopédie) 29 Avenue du Maréchal de Lattre de Tassigny, 54000 Nancy, France
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Kasten P, Beyen I, Bormann D, Luginbühl R, Plöger F, Richter W. The effect of two point mutations in GDF-5 on ectopic bone formation in a beta-tricalciumphosphate scaffold. Biomaterials 2010; 31:3878-84. [PMID: 20170953 DOI: 10.1016/j.biomaterials.2010.01.109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 01/18/2010] [Indexed: 12/14/2022]
Abstract
The osteoinductivity of human growth-and-differentiation factor-5 (GDF-5) is well established, but a reduced amount of ectopic bone is formed compared to other members of the bone morphogenetic protein (BMP) family like BMP-2. We hypothesized that swap of two BMP-receptor-interacting residues of GDF-5 to amino acids present in BMP-2 (methionine to valine at the sites 453 and 456) may improve the bone formation capacity of the mutant GDF-5. Heterotopic bone formation of a mutant GDF-5 coated beta-TCP carrier was compared to carriers coated with similar amounts (10 microg) of GDF-5 and BMP-2 in SCID mice. Four week explants revealed 6-fold higher ALP activity in the mutant GDF-5 versus the wild type GDF-5 group (p < 0.0001) and 1.4-fold higher levels compared to BMP-2 (p < 0.006). Bone area in histology was significantly higher in mutant GDF-5 versus all other groups at 4 weeks; however, at 8 weeks BMP-2 reached a similar neo-bone formation like mutant GDF-5. Micro-CT evaluation confirmed higher values in the mutant GDF-5 and BMP-2 groups compared to wild type GDF-5. In conclusion, the mutant GDF-5 showed superior bone formation capacity than GDF-5, and a faster induction at similar final outcome as BMP-2. Mutant GDF-5 thus represents a promising new GDF-5 variant for bone regeneration possibly acting via an increased binding affinity to the BMP-type I receptor.
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Affiliation(s)
- Philip Kasten
- Research Center for Experimental Orthopaedics, Orthopaedic University Hospital Heidelberg, Heidelberg, Germany
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67
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Rose FRAJ, Hou Q, Oreffo ROC. Delivery systems for bone growth factors — the new players in skeletal regeneration. J Pharm Pharmacol 2010; 56:415-27. [PMID: 15099436 DOI: 10.1211/0022357023312] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Abstract
Given the challenge of an increasing elderly population, the ability to repair and regenerate traumatised or lost tissue is a major clinical and socio-economic need. Pivotal in this process will be the ability to deliver appropriate growth factors in the repair cascade in a temporal and tightly regulated sequence using appropriately designed matrices and release technologies within a tissue engineering strategy. This review outlines the current concepts and challenges in growth factor delivery for skeletal regeneration and the potential of novel delivery matrices and biotechnologies to influence the healthcare of an increasing ageing population.
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Affiliation(s)
- Felicity R A J Rose
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
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68
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Tang P, Yao Q, Zhang W, Liang Y, Zhang L, Wang Y. A study of femoral neck fracture repair using a recombinant human bone morphogenetic protein-2 directional release system. Tissue Eng Part A 2010; 15:3971-8. [PMID: 19995304 DOI: 10.1089/ten.tea.2009.0052] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE Significant difficulties are caused by the delayed union of femoral neck fractures. To address this issue, we designed a new device that applies recombinant human bone morphogenetic protein-2 (rhBMP-2) to promote fracture union. METHODS A cannulated screw with holes was used to deliver rhBMP-2 to the fracture site. Fibrin glue was used as an adhesive agent to hold rhBMP-2 in the vicinity of fracture. RhBMP-2 was protected with polylactide-glycolide acid microspheres. RhBMP-2 release was evaluated to determine the effect of the improved screws. RESULT When polylactide-glycolide acid microspheres were used, 3.65% of the rhBMP-2 was released in the first 2 h, 5.17% was released within 8 h, and 8.95% was released within 24 h. In the microsphere + fibrin glue group, 1.15% of the rhBMP-2 was released in the first 2 h, 1.75% was released within 8 h, and 6.68% was released within 24 h. Over 42 days, about 76.75% of the rhBMP-2 was released when using fibrin glue, which was lower than the amount released using microspheres alone (91.75%). In dog, a faster repair rate was observed on the side with the improved screw than on the side with traditional screw. CONCLUSION The directional release system described here can improve the process of fracture healing and is a promising technique for repairing femoral neck fracture.
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Affiliation(s)
- Peifu Tang
- Department of Orthopaedics, Chinese PLA General Hospital, Beijing, P.R. China
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69
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Seeherman HJ, Li XJ, Bouxsein ML, Wozney JM. rhBMP-2 induces transient bone resorption followed by bone formation in a nonhuman primate core-defect model. J Bone Joint Surg Am 2010; 92:411-26. [PMID: 20124069 DOI: 10.2106/jbjs.h.01732] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Bone resorption preceding bone formation has been reported following the administration of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in an absorbable collagen sponge (ACS) in metaphyseal bone. This study characterizes treatment with rhBMP-2/ACS in metaphyseal bone with use of a nonhuman primate core-defect model. METHODS Unilateral proximal femoral core defects were treated with 360 microg of rhBMP-2/ACS or ACS alone or were left untreated in seven, five, and five adult male cynomolgus monkeys, respectively. Distal femoral core defects in seven of the above animals were treated with 360 microg of rhBMP-2/ACS in one limb and ACS alone in the contralateral limb. Retention of rhBMP-2 in the proximal part of the femora was determined with use of tracer amounts of (125)I-rhBMP-2 imaged with a gamma camera. The distal part of the femora was evaluated with in vivo computed tomography. Computed tomography and histological evaluation were performed on harvested segments in all animals at twenty-four weeks. The histological response in the proximal and distal parts of the femora containing core defects treated with 360 microg of rhBMP-2/ACS in one limb and ACS alone in the contralateral limb was evaluated at one, two, and four weeks in three animals per time point. RESULTS Approximately 39.9%, 24.2%, 3.4%, and 0.5% of the rhBMP-2 was retained in the proximal part of the femora at one, seven, fourteen, and twenty-one days, respectively. The mineral density and trabecular volume fraction of the core defects treated with rhBMP-2/ACS, those treated with ACS alone, and untreated core defects in the proximal part of the femora were 81%, 54%, and 20%, respectively, and 94%, 36%, and 31%, respectively, of the corresponding region in the contralateral limbs at twenty-four weeks. The mineral density and trabecular volume fraction of the region surrounding the core defects treated with rhBMP-2/ACS, those treated with ACS alone, and untreated core defects were 112%, 105%, and 104%, respectively, and 117%, 108%, and 107%, respectively, of the corresponding region in the contralateral limbs. Treatment with rhBMP-2/ACS increased the size of the proximal and distal core defects compared with treatment with ACS alone. Histological evaluation of the rhBMP-2/ACS-treated limbs demonstrated that bone resorption was initiated at one week in association with osteoclasts and receptor activator of nuclear factor-kappaB ligand-positive stained spindle-shaped cells and peaked at two weeks. Bone formation was observed at two weeks and was ongoing at twenty-four weeks. CONCLUSIONS Treatment of metaphyseal core defects with rhBMP-2/ACS resulted in bone resorption followed by bone formation in nonhuman primates.
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Affiliation(s)
- Howard J Seeherman
- Musculoskeletal Therapies, Wyeth Discovery Research, Cambridge, MA 02140, USA.
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70
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Haidar ZS, Hamdy RC, Tabrizian M. Biocompatibility and safety of a hybrid core-shell nanoparticulate OP-1 delivery system intramuscularly administered in rats. Biomaterials 2009; 31:2746-54. [PMID: 20044132 DOI: 10.1016/j.biomaterials.2009.12.034] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 12/13/2009] [Indexed: 11/18/2022]
Abstract
A hybrid, localized and release-controlled delivery system for bone growth factors consisting of a liposomal core incorporated into a shell of alternating layer-by-layer self-assembled natural polyelectrolytes has been formulated. Hydrophilic, monodisperse, spherical and stable cationic nanoparticles (< or =350 nm) with an extended shelf-life resulted. Cytocompatibility was previously assayed with MC3T3-E1.4 mouse preosteoblasts showing no adverse effects on cell viability. In this study, the in vivo biocompatibility of unloaded and loaded nanoparticles with osteogenic protein-1 or OP-1 was investigated. Young male Wistar rats were injected intramuscularly and monitored over a period of 10 weeks for signs of inflammation and/or adverse reactions. Blood samples (600 microL/collection) were withdrawn followed by hematological and biochemical analysis. Body weight changes over the treatment period were noted. Major organs were harvested, weighed and examined histologically for any pathological changes. Finally, the injection site was identified and examined immunohistochemically. Overall, all animals showed no obvious toxic health effects, immune responses and/or change in organ functions. This hybrid core-shell nanoparticulate delivery system localizes the effect of the released bioactive load within the site of injection in muscle with no significant tissue distress. Hence, a safe and promising carrier for therapeutic growth factors and possibly other biomolecules is presented.
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Affiliation(s)
- Ziyad S Haidar
- Faculty of Dentistry, McGill University, Montréal, QC H3A2B4, Canada
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71
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Bergman K, Engstrand T, Hilborn J, Ossipov D, Piskounova S, Bowden T. Injectable cell-free template for bone-tissue formation. J Biomed Mater Res A 2009; 91:1111-8. [DOI: 10.1002/jbm.a.32289] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Zhang S, Kucharski C, Doschak MR, Sebald W, Uludağ H. Polyethylenimine-PEG coated albumin nanoparticles for BMP-2 delivery. Biomaterials 2009; 31:952-63. [PMID: 19878992 DOI: 10.1016/j.biomaterials.2009.10.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 10/05/2009] [Indexed: 01/24/2023]
Abstract
Bone Morphogenetic Protein-2 (BMP-2) plays an important role in stimulating new bone formation, and has been utilized in clinical bone repair by implantation. In this study, we report a nanoparticulate (NP) system for BMP-2 delivery based on bovine serum albumin (BSA) NPs stabilized with a poly(ethylene glycol) modified polyethylenimine (PEI-PEG) coating. PEI-PEG with different PEG substitutions were synthesized, and the cell viability assay showed PEG substitution greatly reduced the cytotoxicity of the native PEI. Furthermore, PEI-PEG coated BSA NPs demonstrated smaller size and decreased zeta potential compared to PEI-coated NPs. The bioactivity of the encapsulated BMP-2 and the toxicity of PEI-PEG coated NPs were examined by the alkaline phosphatase (ALP) induction assay and the MTT assay, respectively, using human C2C12 cells. The results indicated that BMP-2 remained bioactive in NPs and PEI-PEG coating was advantageous in reducing the NP toxicity as compared to PEI. A 7-day pharmacokinetics study showed the BMP-2 retention in PEI-PEG coated NPs was similar to the uncoated NPs, but lower than that of the PEI-coated NPs. The osteoinductivity of BMP-2 delivered in NPs was determined by subcutaneous implantation in rats, and the results revealed that PEI-PEG coated BSA NPs induced significant de novo bone formation after implantation, while PEI-coated NPs demonstrated much less bone formation. We conclude that BMP-2 delivered by PEGylated PEI-coated BSA NPs displays favorable biocompatibility and promotes new bone formation after implantation.
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Affiliation(s)
- Sufeng Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Canada
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73
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Mandal BB, Kundu SC. Calcium alginate beads embedded in silk fibroin as 3D dual drug releasing scaffolds. Biomaterials 2009; 30:5170-7. [DOI: 10.1016/j.biomaterials.2009.05.072] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 05/24/2009] [Indexed: 10/20/2022]
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Zhang S, Doschak MR, Uludağ H. Pharmacokinetics and bone formation by BMP-2 entrapped in polyethylenimine-coated albumin nanoparticles. Biomaterials 2009; 30:5143-55. [PMID: 19540582 DOI: 10.1016/j.biomaterials.2009.05.060] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Accepted: 05/21/2009] [Indexed: 11/29/2022]
Abstract
The osteoinductive growth factor, bone morphogenetic protein-2 (BMP-2), is capable of inducing de novo bone formation after implantation. A nanoparticulate (NP) system was developed for BMP-2 delivery based on NPs fabricated from bovine serum albumin (BSA) and stabilized by polyethylenimine (PEI) coating. In this study, the pharmacokinetics and osteoinductivity of BMP-2 delivered with different BSA NP formulations were determined by subcutaneous implantation in rats. A 7-day pharmacokinetics study showed that PEI coating on NPs effectively reduced the initial burst release of BMP-2 and prolonged the BMP-2 retention at implantation site. However, the uncoated BMP-2 NPs (BMP-2 loading of 1.44% w/w) were able to induce a robust ectopic bone formation, while no bone formation was found by the BMP-2 NPs coated with PEI. The toxicity of the PEI used for NP coating was determined to be the reason for lack of osteoinduction. Increasing BMP-2 loading (up to 5.76% w/w) was then employed to formulate NPs with lower PEI content; the higher BMP-2 loading was found to better promote induction of de novo bone. Our findings indicated that PEI coating on BSA NPs was effective for controlling BMP-2 release from NPs, but the toxicity of cationic PEI was a concern for the osteoinductive activity, which should be alleviated by further optimization of NP formulations.
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Affiliation(s)
- Sufeng Zhang
- Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, Edmonton, AB, Canada
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75
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Shen H, Hu X, Yang F, Bei J, Wang S. The bioactivity of rhBMP-2 immobilized poly(lactide-co-glycolide) scaffolds. Biomaterials 2009; 30:3150-7. [DOI: 10.1016/j.biomaterials.2009.02.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2008] [Accepted: 02/02/2009] [Indexed: 10/21/2022]
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Gruber R, Weich HA, Dullin C, Schliephake H. Ectopic bone formation after implantation of a slow release system of polylactic acid and rhBMP-2. Clin Oral Implants Res 2009; 20:24-30. [PMID: 19126104 DOI: 10.1111/j.1600-0501.2008.01613.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES The present study was conducted to test the hypothesis that preshaped polylactic acid (PLA) implants loaded with recombinant human bone morphogenic protein 2 (rhBMP-2) can induce bone formation in a rat ectopic model. MATERIALS AND METHODS Two groups of porous cylindrical poly-DL-lactic acid implants of 8-mm diameter were produced by gas foaming with CO(2), incorporating 48 and 96 microg rhBMP-2, respectively, into each implant. Blank PLA implants were used as controls. The release of BMPs and the induction of alkaline phosphatase were assessed in vitro. Osteoinduction in vivo was tested by insertion of 15 implants from each group into the gluteal muscles of Wistar rats. Five implants from each group were retrieved after 6, 13 and 26 weeks and assessed using flat panel volume detector computed tomography and light microscopy. RESULTS Both groups of implants showed increased release of rhBMP-2 during the first 24-48 h, with a slightly higher amount being released from the implants with 48 microg. Release during subsequent intervals was <100 ng/72 h in the low-concentration group and >100 ng in the group with 96 microg rhBMP-2. Implants with 95 microg rhBMP-2 exhibited bone formation in vivo on the outside of the implants across the observation period of 26 weeks with invasion of bone into the pores, whereas implants with 48 microg rhBMP-2 failed to induce the formation of bone tissue. No bone formation was found in the control implants. CONCLUSIONS The results suggest that release rates of rhBMP-2 for ectopic bone induction have to be >100 ng/72 h to maintain the osteoinductive activity of the tested porous PLA implants. This slow release system may have impact on alveolar bone augmentation procedures when used as individually preformed osteoinductive implants.
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Affiliation(s)
- R Gruber
- Department of Oral and Maxillofacial Surgery, George-Augusta-University, Göttingen, Germany
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77
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Zhang S, Wang G, Lin X, Chatzinikolaidou M, Jennissen HP, Laub M, Uludağ H. Polyethylenimine-coated albumin nanoparticles for BMP-2 delivery. Biotechnol Prog 2009; 24:945-56. [PMID: 19194903 DOI: 10.1002/btpr.12] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nanoparticle (NP)-based delivery has gained importance for improving the potency of therapeutic agents. The bovine serum albumin (BSA) NPs, obtained by a coacervation process, was modified by electrostatic adsorption of cationic polyethylenimine (PEI) to NP surfaces for delivery of bone-inducing growth factor, bone morphogenetic protein-2 (BMP-2). Different concentrations of PEI were utilized for coating BSA NPs to stabilize the colloidal system and to control the release of BMP-2. The NPs were characterized by size and zeta potential measurements, as well as by Scanning Electron Microscopy and Atomic Force Microscopy. The encapsulation efficiency was typically >90% in all NP preparations. In vitro release kinetics showed that the PEI concentration used for coating the NPs efficiently controlled the release of BMP-2, demonstrating a gradual slowing, sustained release pattern during a 10-day study period. The bioactivity of the encapsulated BMP-2 and the toxicity of the NPs were examined by the alkaline phosphatase (ALP) induction assay and the MTT assay, respectively, using C2C12 cells. The results indicated that PEI was the primary determinant of NP toxicities, and BSA NPs coated with 0.1 mg/mL PEI demonstrated tolerable toxicity, retained the bioactivity of BMP-2, and efficiently slowed the release rate of BMP-2. We conclude that BMP-2 encapsulated in BSA NPs might be an efficient way to deliver the protein for in vivo bone induction.
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Affiliation(s)
- Sufeng Zhang
- Faculty of Engineering, Dept. of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
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78
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Crouzier T, Ren K, Nicolas C, Roy C, Picart C. Layer-by-layer films as a biomimetic reservoir for rhBMP-2 delivery: controlled differentiation of myoblasts to osteoblasts. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:598-608. [PMID: 19219837 DOI: 10.1002/smll.200800804] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Efficient delivery of growth or survival factors to cells is one of the most important long-term challenges of current cell-based tissue engineering strategies. The extracellular matrix acts as a reservoir for a number of growth factors through interactions with its components. In the matrix, growth factors are protected against circulating proteases and locally concentrated. Thus, the localized and long-lasting delivery of a matrix-bound recombinant human bone morphogenetic protein 2 (rhBMP-2) from a biomaterial surface would mimic in vivo conditions and increase BMP-2 efficiency by limiting its degradation. Herein, it is shown that crosslinked poly(L-lysine)/hyaluronan (HA) layer-by-layer films can serve as a reservoir for rhBMP-2 delivery to myoblasts and induce their differentiation into osteoblasts in a dose-dependent manner. The amount of rhBMP-2 loaded in the films is controlled by varying the deposition conditions and the film thickness. Its local concentration in the film is increased up to approximately 500-fold when compared to its initial solution concentration. Its adsorption on the films, as well as its diffusion within the films, is evidenced by microfluorimetry and confocal microscopy observations. A direct interaction of rhBMP-2 with HA is demonstrated by size-exclusion chromatography, which could be at the origin of the rhBMP-2 "trapping" in the film and of its low release from the films. The bioactivity of rhBMP-2-loaded films is due neither to film degradation nor to rhBMP-2 release. The rhBMP-2-containing films are extremely resistant and could sustain three successive culture sequences while remaining bioactive, thus confirming the important and protective effect of rhBMP-2 immobilization. These films may find applications in the local delivery of immobilized growth factors for tissue-engineered constructs and for metallic biomaterial surfaces, as they can be deposited on a wide range of substrates with different shapes, sizes, and composition.
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Affiliation(s)
- Thomas Crouzier
- UMR 5235 Dynamique des Interactions Membranaires Normales et Pathologiques CNRS, Université Montpellier II et I cc 107, Montpellier, France
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79
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Bodde EWH, Boerman OC, Russel FGM, Mikos AG, Spauwen PHM, Jansen JA. The kinetic and biological activity of different loaded rhBMP-2 calcium phosphate cement implants in rats. J Biomed Mater Res A 2009; 87:780-91. [PMID: 18200544 DOI: 10.1002/jbm.a.31830] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The healing of large bone defects can be improved by osteogenic bone graft substitutes, due to growth factor inclusion. A sustained release of these growth factors provides more efficient bioactivity when compared with burst release and might reduce the dose required for bone regeneration, which is desirable for socioeconomical and safety reasons. In this study, we compared different rhBMP-2 loadings in a sustained release system of CaP cement and PLGA-microparticles and were able to couple kinetic to biological activity data. Fifty-two rats received a critical-size cranial defect, which was left open or filled with the cement composites. The implants consisted of plain, high, and five-fold lower dose rhBMP-2 groups. Implantation time was 4 and 12 weeks. Longitudinal in vivo release was monitored by scintigraphic imaging of (131)I-labeled rhBMP-2. Quantitative analysis of the scintigraphic images revealed a sustained release of (131)I-rhBMP-2 for both doses, with different release profiles between the two loadings. However, around 70% of the initial dose was retained in both implant formulations. Although low amounts of rhBMP-2 were released (2.4 +/- 0.8 mug in 5 weeks), histology showed defect bridging in the high-dose implants. Release out of the low-dose implants was not sufficient to enhance bone formation. Implant degradation was limited in all formulations, but was mainly seen in the high-dose group. Low amounts of sustained released rhBMP-2 were sufficient to bridge critically sized defects. A substantial amount of rhBMP-2 was retained in the implants because of the slow release rate and the limited degradation.
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Affiliation(s)
- Esther W H Bodde
- Department of Periodontology and Biomaterials, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
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80
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Kempen DHR, Yaszemski MJ, Heijink A, Hefferan TE, Creemers LB, Britson J, Maran A, Classic KL, Dhert WJA, Lu L. Non-invasive monitoring of BMP-2 retention and bone formation in composites for bone tissue engineering using SPECT/CT and scintillation probes. J Control Release 2008; 134:169-76. [PMID: 19105972 DOI: 10.1016/j.jconrel.2008.11.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 11/13/2008] [Accepted: 11/20/2008] [Indexed: 10/21/2022]
Abstract
Non-invasive imaging can provide essential information for the optimization of new drug delivery-based bone regeneration strategies to repair damaged or impaired bone tissue. This study investigates the applicability of nuclear medicine and radiological techniques to monitor growth factor retention profiles and subsequent effects on bone formation. Recombinant human bone morphogenetic protein-2 (BMP-2, 6.5 microg/scaffold) was incorporated into a sustained release vehicle consisting of poly(lactic-co-glycolic acid) microspheres embedded in a poly(propylene fumarate) scaffold surrounded by a gelatin hydrogel and implanted subcutaneously and in 5-mm segmental femoral defects in 9 rats for a period of 56 days. To determine the pharmacokinetic profile, BMP-2 was radiolabeled with (125)I and the local retention of (125)I-BMP-2 was measured by single photon emission computed tomography (SPECT), scintillation probes and ex vivo scintillation analysis. Bone formation was monitored by micro-computed tomography (microCT). The scaffolds released BMP-2 in a sustained fashion over the 56-day implantation period. A good correlation between the SPECT and scintillation probe measurements was found and there were no significant differences between the non-invasive and ex-vivo counting method after 8 weeks of follow up. SPECT analysis of the total body and thyroid counts showed a limited accumulation of (125)I within the body. Ectopic bone formation was induced in the scaffolds and the femur defects healed completely. In vivo microCT imaging detected the first signs of bone formation at days 14 and 28 for the orthotopic and ectopic implants, respectively, and provided a detailed profile of the bone formation rate. Overall, this study clearly demonstrates the benefit of applying non-invasive techniques in drug delivery-based bone regeneration strategies by providing detailed and reliable profiles of the growth factor retention and bone formation at different implantation sites in a limited number of animals.
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Affiliation(s)
- Diederik H R Kempen
- Tissue Engineering and Biomaterials Laboratory, Departments of Orthopedic Surgery and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
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Wei G, Ma PX. Nanostructured Biomaterials for Regeneration. ADVANCED FUNCTIONAL MATERIALS 2008; 18:3566-3582. [PMID: 19946357 PMCID: PMC2701700 DOI: 10.1002/adfm.200800662] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Biomaterials play a pivotal role in regenerative medicine, which aims to regenerate and replace lost/dysfunctional tissues or organs. Biomaterials (scaffolds) serve as temporary 3D substrates to guide neo tissue formation and organization. It is often beneficial for a scaffolding material to mimic the characteristics of extracellular matrix (ECM) at the nanometer scale and to induce certain natural developmental or/and wound healing processes for tissue regeneration applications. This article reviews the fabrication and modification technologies for nanofibrous, nanocomposite, and nanostructured drug-delivering scaffolds. ECM-mimicking nanostructured biomaterials have been shown to actively regulate cellular responses including attachment, proliferation, differentiation and matrix deposition. Nano-scaled drug delivery systems can be successfully incorporated into a porous 3D scaffold to enhance the tissue regeneration capacity. In conclusion, nano-structured biomateials are a very exciting and rapidly expanding research area, and are providing new enabling technologies for regenerative medicine.
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Affiliation(s)
- Guobao Wei
- Department of Biomedical Engineering, University of Michigan
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82
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Bessa PC, Casal M, Reis RL. Bone morphogenetic proteins in tissue engineering: the road from the laboratory to the clinic, part I (basic concepts). J Tissue Eng Regen Med 2008; 2:1-13. [PMID: 18293427 DOI: 10.1002/term.63] [Citation(s) in RCA: 230] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Discovered in 1965, bone morphogenetic proteins (BMPs) are a group of cytokines from the transforming growth factor-beta (TGFbeta) superfamily with significant roles in bone and cartilage formation. BMPs are used as powerful osteoinductive components of diverse tissue-engineering products for the healing of bone. Several BMPs with different physiological roles have been identified in humans. The purpose of this review is to cover the biological function of the main members of BMP family, the latest research on BMPs signalling pathways and advances in the production of recombinant BMPs for tissue engineering purposes.
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Affiliation(s)
- P C Bessa
- 3Bs Research Group, Biomaterials, Biodegradables and Biomimetics, Department of Polymer Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
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83
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Sohier J, Moroni L, van Blitterswijk C, de Groot K, Bezemer JM. Critical factors in the design of growth factor releasing scaffolds for cartilage tissue engineering. Expert Opin Drug Deliv 2008; 5:543-66. [PMID: 18491981 DOI: 10.1517/17425247.5.5.543] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Trauma or degenerative diseases of the joints are common clinical problems resulting in high morbidity. Although various orthopedic treatments have been developed and evaluated, the low repair capacities of articular cartilage renders functional results unsatisfactory in the long term. Over the last decade, a different approach (tissue engineering) has emerged that aims not only to repair impaired cartilage, but also to fully regenerate it, by combining cells, biomaterials mimicking extracellular matrix (scaffolds) and regulatory signals. The latter is of high importance as growth factors have the potency to induce, support or enhance the growth and differentiation of various cell types towards the chondrogenic lineage. Therefore, the controlled release of different growth factors from scaffolds appears to have great potential to orchestrate tissue repair effectively. OBJECTIVE This review aims to highlight considerations and limitations of the design, materials and processing methods available to create scaffolds, in relation to the suitability to incorporate and release growth factors in a safe and defined manner. Furthermore, the current state of the art of signalling molecules release from scaffolds and the impact on cartilage regeneration in vitro and in vivo is reported and critically discussed. METHODS The strict aspects of biomaterials, scaffolds and growth factor release from scaffolds for cartilage tissue engineering applications are considered. CONCLUSION Engineering defined scaffolds that deliver growth factors in a controlled way is a task seldom attained. If growth factor delivery appears to be beneficial overall, the optimal delivery conditions for cartilage reconstruction should be more thoroughly investigated.
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Affiliation(s)
- J Sohier
- Laboratory for osteo-articular and dental tissue engineering (LIOAD), Faculté de chirurgie dentaire de Nantes, Inserm U791, 1 Place Alexis Ricordeau, 44042 Nantes Cedex 1, France.
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84
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Kasten P, Vogel J, Beyen I, Weiss S, Niemeyer P, Leo A, Lüginbuhl R. Effect of platelet-rich plasma on the in vitro proliferation and osteogenic differentiation of human mesenchymal stem cells on distinct calcium phosphate scaffolds: the specific surface area makes a difference. J Biomater Appl 2008; 23:169-88. [PMID: 18632770 DOI: 10.1177/0885328207088269] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The in vitro effect of platelet-rich plasma (PRP) on cell loading, proliferation, and osteogenic differentiation of human mesenchymal stem cells (MSC) is assessed on distinct resorbable and synthetic calcium phosphate scaffolds. A high specific surface area scaffold composed of calcium-deficient hydroxyapatite (CDHA; 48m2/g) is compared with one made out of beta-tricalcium phosphate (beta-TCP; surface area <0.5 m2/g). Fivefold concentrated fresh PRP is applied to scaffolds loaded with 2 x 10(5) MSC (n = 5). These constructs are kept in a medium with osteogenic supplements for 3 weeks. The addition of PRP leads to a higher cell loading efficiency of MSC on CDHA (p = 0.0001), that reaches the values of beta-TCP. Proliferation over 21 days is improved by PRP both on CDHA (p = 0.0001) and beta-TCP (p = 0.014) compared to MSC/calcium phosphate composites. Without the addition of PRP, CDHA has a lower cell loading efficiency (p= 0.0001) and proliferation (p= 0.001) than beta-TCP. The ALP activity is higher in the MSC/ceramics groups than in the monolayer controls (p<0.05). The addition of PRP does not significantly affect ALP activity. However, ALP activity varies considerably within the cell donors and different PRP-pools (p = 0.001), while the cell numbers do not vary within these two parameters. PRP generates a positive effect on the loading efficiency of MSC on the high specific surface scaffold CDHA that thereby reaches the loading efficiency of beta-TCP. PRP improved proliferation, but its osteogenic properties on both calcium phosphate scaffolds are weak.
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Affiliation(s)
- Philip Kasten
- Orthopaedic Surgery, University of Heidelberg, Schlierbacher Landstr. 200a 69118 Heidelberg, Germany.
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85
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Abstract
STUDY DESIGN Prospective measurement of rhBMP-2 from drains in a cohort of patients undergoing posterolateral spinal fusion. OBJECTIVE To quantify the amount of rhBMP-2 that extravasates into drains after posterolateral fusion using its current commercially available form, rhBMP-2 within an absorbable collagen sponge. SUMMARY OF BACKGROUND DATA Retention of rhBMP-2 at the fusion site is essential for clinical efficacy and avoidance of unintentional bony growth in other areas of the spine. In vitro studies have shown a large degree of rhBMP-2 release from the sponge within the first 48 hours. It is unknown what effect drainage may have on changing the local concentration of BMP at the posterolateral site. METHODS The entire contents of drains were collected for 48 hours after surgery from 9 patients who underwent instrumented posterolateral fusion with rhBMP-2. The total amount collected was calculated from the concentration of BMP-2 as measured by enzyme-linked immunosorbent assay. RESULTS A median 68 microg of BMP-2 (range, 13-498) was recovered from drains, representing a median 0.58% (range, 0.21%-4.2%) of the amount implanted; adjusted for yield rate, a median 1.08% was recovered. No significant relationships were found between percentage of BMP-2 extravasation and amount implanted, number of levels, blood loss, and drainage output. A mean 54% of the total amount recovered was in the drain within the first 6 hours. CONCLUSION The greater bleeding and muscular compression associated with posterolateral fusion did not result in a substantial amount of rhBMP-2 extravasation into postoperative drains. Based on the small rates of recovery, suction drains may be placed after even complex surgeries involving large blood loss without the loss of significant amounts of the implanted rhBMP-2 into the drain.
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86
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Kempen DHR, Lu L, Classic KL, Hefferan TE, Creemers LB, Maran A, Dhert WJA, Yaszemski MJ. Non-invasive screening method for simultaneous evaluation of in vivo growth factor release profiles from multiple ectopic bone tissue engineering implants. J Control Release 2008; 130:15-21. [PMID: 18554743 DOI: 10.1016/j.jconrel.2008.05.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 04/29/2008] [Accepted: 05/06/2008] [Indexed: 11/28/2022]
Abstract
The purpose of this study was to develop and validate a screening method based on scintillation probes for the simultaneous evaluation of in vivo growth factor release profiles of multiple implants in the same animal. First, we characterized the scintillation probes in a series of in vitro experiments to optimize the accuracy of the measurement setup. The scintillation probes were found to have a strong geometric dependence and experience saturation effects at high activities. In vitro simulation of 4 subcutaneous limb implants in a rat showed minimal interference of surrounding implants on local measurements at close to parallel positioning of the probes. These characteristics were taken into consideration for the design of the probe setup and in vivo experiment. The measurement setup was then validated in a rat subcutaneous implantation model using 4 different sustained release carriers loaded with (125)I-BMP-2 per animal. The implants were removed after 42 or 84 days of implantation, for comparison of the non-invasive method to ex vivo radioisotope counting. The non-invasive method demonstrated a good correlation with the ex vivo counting method at both time-points of all 4 carriers. Overall, this study showed that scintillation probes could be successfully used for paired measurement of 4 release profiles with minimal interference of the surrounding implants, and may find use as non-invasive screening tools for various drug delivery applications.
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Affiliation(s)
- Diederik H R Kempen
- Tissue Engineering and Biomaterials Laboratory, Departments of Orthopedic Surgery and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
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87
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Mandibular bone repair by implantation of rhBMP-2 in a slow release carrier of polylactic acid--an experimental study in rats. Biomaterials 2008; 29:103-10. [PMID: 17936352 DOI: 10.1016/j.biomaterials.2007.09.019] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Accepted: 09/18/2007] [Indexed: 11/24/2022]
Abstract
The aim of the present study was to test the hypothesis that human recombinant bone morphogenic protein 2 (rhBMP-2) implanted in a slow release carrier of polylactic acid (PLA) can repair a non-healing defect in the rat mandible and maintain the thickness of an augmented volume. p-DL-lactic acid discs were produced and loaded with 48 and 96 microg rhBMP-2 and inserted into non-healing defects of the mandible of 45 Wistar rats. Fifteen rats received implants with 96 microg rhBMP-2 (Group 2), 48 microg rhBMP-2 (Group 1) and blank implants without BMP (Group 0) each on one side of the mandible. Unfilled defects of the same size on the contralateral sides of the mandibles served as empty controls. After 6, 13 and 26 weeks, implants of each group were retrieved from five animals each and submitted to flat panel detector computed tomography. Bone formation and thickness of augmentation was assessed by computer-assisted histomorphometry. In Group 2 significantly more bone was produced than in Group 1. Implants of Group 1 induced significantly more bone than the blank controls only after 6 weeks, whereas the difference was not significant after 13 and 26 weeks. Differences between Group 2 and Group 1 were clearly significant after 26 weeks. The thickness of bone tissue was maintained in Group 2 whereas it decreased in Group 1 and was negligible in Group 0. It is concluded that the PLA implants with 96 microg rhBMP-2 were able to bridge a non-healing defect in the rat mandible and maintained the thickness of an augmented volume. However, continuous supply of osteogenic signals appears to be required to compensate for adverse effects during polymer degradation.
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88
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Patterson TE, Kumagai K, Griffith L, Muschler GF. Cellular strategies for enhancement of fracture repair. J Bone Joint Surg Am 2008; 90 Suppl 1:111-9. [PMID: 18292365 DOI: 10.2106/jbjs.g.01572] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Tissue engineering seeks to translate scientific knowledge into tangible products to advance the repair, replacement, or regeneration of organs and tissues. Current tissue engineering strategies have progressed recently from a historical approach that is based primarily on biomaterials to a cell and tissue-based approach that includes understanding of cell-sourcing and bioactive stimuli. New options include methods for harvest and transplantation of tissue-forming cells, bioactive matrix materials that act as tissue scaffolds, and delivery of bioactive molecules within scaffolds. These strategies are already benefiting patients, and they place increasing demands on orthopaedic surgeons to have a solid foundation in the contemporary concepts and principles of cell-based tissue engineering. Essentially all orthopaedic tissue engineering strategies can be distilled to a strategy or combination of strategies that seek to increase the number or relative performance of bone-forming cells. The global term connective tissue progenitors has been used to define the heterogeneous populations of stem and progenitor cells that are found in native tissue and that are capable of differentiating into one or more connective tissue phenotypes. These stem or progenitor populations are found in various tissue sources, with varying degrees of ability to differentiate along connective tissue lineages. Available cell-based strategies include targeting local cells with use of scaffolds or bioactive factors, or transplantation of autogenous connective tissue progenitor cells derived from bone marrow or other tissues, with or without processing to change their concentration or prevalence. The future may include means of homing circulating connective tissue progenitor cells with use of intrinsic chemokine systems, or modifying the biological performance of connective tissue progenitor cells by means of genetic modifications.
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Affiliation(s)
- Thomas E Patterson
- Department of Orthopaedic Surgery, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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89
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Maus U, Andereya S, Gravius S, Ohnsorge JAK, Niedhart C, Siebert CH. BMP-2 incorporated in a tricalcium phosphate bone substitute enhances bone remodeling in sheep. J Biomater Appl 2008; 22:559-76. [PMID: 18194994 DOI: 10.1177/0885328207083311] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Bone morphogenetic protein-2 (BMP-2) is a well-known osteoinductive protein, which requires a carrier for local application. As an alternative to the previously described carriers, an in situ hardening, resorbable, and osteoconductive beta-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 microg rhBMP-2 per cm3 TCP, autologous bone graft, pure TCP, or left empty. A radiological follow-up is performed after 7 weeks and 3 months. The sheep are euthanized and bone samples are analyzed by microradiography, histology, and histomorphometry. Microradiography and histology show similar results for pure TCP and the composite. The defects are filled with trabecular bone and newly formed bone is in close contact with the remaining TCP-particles. The majority of the cement is resorbed, in the composite group the amount of remaining cement particles is reduced. Defects treated with autologous bone graft are filled completely, while untreated defects shows only a small amount of bone originating from the rim of the defect. Histomorphometry of the defects treated with pure TCP shows a significantly increased bone content in comparison to defects treated with the composite or autologous bone graft. Analysis of the remaining cement particles shows significantly less cement in the TCP/rhBMP-2 group in comparison to pure TCP. The sum of bone and cement content in the rhBMP-2 group shows amounts comparable to the calcified structures found following autologous bone grafting. The addition of rhBMP-2 to the TCP leads to faster remodeling of the defect comparable to autologous bone graft, while defects treated with pure TCP are not completely remodeled.
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Affiliation(s)
- Uwe Maus
- Department of Orthopedic Surgery, University of Aachen, Pauwelsstr 30, D-52074 Aachen, Germany.
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90
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Erickson BP, Pierce AR, Simpson AK, Nash J, Grauer JN. 125I-labeled OP-1 is locally retained in a rabbit lumbar fusion model. Clin Orthop Relat Res 2008; 466:210-5. [PMID: 18196395 PMCID: PMC2505306 DOI: 10.1007/s11999-007-0017-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Accepted: 09/10/2007] [Indexed: 01/31/2023]
Abstract
Osteogenic protein-1 is evolving as a potential bone graft alternative. Surgical site retention is important to maximize local osteoinduction and to limit peripheral effects. An established rabbit lumbar posterolateral fusion model was used to evaluate the systemic distribution and pharmacokinetics of locally applied osteogenic protein-1 delivered on a collagen carrier. L5-L6 intertransverse process fusions were performed on 27 New Zealand White rabbits. Radiolabeled (125)I-osteogenic protein-1 collagen putty was implanted. At intervals, whole blood, plasma, and excreta were analyzed for radioactivity with liquid scintillation counting. Surgical site and tissue radioactivity also were assessed by quantitative whole-body autoradioluminography of animals euthanized at times ranging from 6 hours to 35 days. Animals remaining at the final time were assessed for fusion with manual palpation, radiography, and histology. Limited distribution of radioactivity was observed in the blood, plasma, and tissues apart from at the surgical site and in the urinary bladder and thyroid. The mean residence time for osteogenic protein-1 collagen putty was 10.4 +/- 2.7 days. These excretion profiles and kinetic properties are similar to those described for recombinant human bone morphogenetic protein-2 in the rabbit model (mean residence times of 7.6 days and 10.2 days with different carriers).
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Affiliation(s)
- Benjamin P. Erickson
- Department of Orthopaedics, Rehabilitation, Yale University School of Medicine, PO Box 208071, New Haven, CT 06520-8071 USA
| | | | - Andrew K. Simpson
- Department of Orthopaedics, Rehabilitation, Yale University School of Medicine, PO Box 208071, New Haven, CT 06520-8071 USA
| | - John Nash
- Charles River Laboratories Preclinical Services, Montreal, Quebec Canada
| | - Jonathan N. Grauer
- Department of Orthopaedics, Rehabilitation, Yale University School of Medicine, PO Box 208071, New Haven, CT 06520-8071 USA
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91
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Schliephake H, Weich HA, Schulz J, Gruber R. In vitro characterization of a slow release system of polylactic acid and rhBMP2. J Biomed Mater Res A 2007; 83:455-62. [PMID: 17477390 DOI: 10.1002/jbm.a.31227] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The aim of the present report was to test a system for controlled release of recombinant human bone morphogenic protein (rhBMP2) incorporated into polylactic acid (PLA) implants. Incorporation of rhBMP2 into the polymer was accomplished by mixing rhBMP2 solution with granular powder of amorphous poly-DL-lactic acid, subsequent lyophilization, and high pressure CO(2) treatment at 100 bar. Porous cylindrical implants of 8 mm diameter and 3 mm thickness were fabricated with 100, 200, 400, and 800 microg BMP2/g polymer and submitted to in vitro testing. Polymer degradation was assessed during immersion of PLA implants into PBS for 176 days by measuring the inherent viscosity at days 0, 99, and 131. BMP2 release was evaluated by immersion of both the lyophilized powder and the implants into cell culture medium for up to 27 days. BMP2 release was assessed using a custom made ELISA. The biological activity of the released growth factor was determined by measuring the induction of alkaline phosphatase (AP) in C2C12 cells. There was a significant retardation in the release of BMP2 from the implants compared to the granular powder. Detectable amounts of BMP2 were found for all concentrations of BMP2 until the end of the observation period. Significant induction of AP was detected by BMP released from the implants after 3, 6, and 9 days. The present in-vitro study has shown that incorporation of rhBMP2 into PLA implants with subsequent slow release of biologically active growth factor is possible.
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Affiliation(s)
- H Schliephake
- Department of Oral and Maxillofacial Surgery, George-Augusta-University, Göttingen, Germany.
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92
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Link DP, van den Dolder J, van den Beucken JJ, Wolke JG, Mikos AG, Jansen JA. Bone response and mechanical strength of rabbit femoral defects filled with injectable CaP cements containing TGF-beta 1 loaded gelatin microparticles. Biomaterials 2007; 29:675-82. [PMID: 17996293 DOI: 10.1016/j.biomaterials.2007.10.029] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Accepted: 10/19/2007] [Indexed: 11/17/2022]
Abstract
This study focused at the potential of transforming growth factor beta 1 (TGF-beta 1) loaded gelatin microparticles to enhance the bone response and mechanical strength of rabbit femoral defects filled with injectable calcium phosphate (CaP)/gelatin microparticle composites. Therefore, TGF-beta1 loaded composites and non-loaded controls were injected in circular defects as created in the femoral condyles of rabbits and were left in place for 4, 8 and 12 weeks. The specimens were evaluated mechanically (push-out test), and morphologically (scanning electron microscopy (SEM), histology, and histomorphometry). The results showed a gradual increase in mechanical strength with increasing implantation periods. Histological and histomorphometrical evaluation showed similar results for both composite formulations regarding histological aspect, new bone formation and bone/implant contact. However, TGF-beta1 loading of the composites demonstrated a significant effect on composite degradation after twelve weeks of implantation. The results of this study showed that CaP/gelatin composites show excellent osteogenic properties and a rapid increase in mechanical strength. The addition of TGF-beta1 significantly enhances the bone remodeling process.
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Affiliation(s)
- Dennis P Link
- Department of Periodontology and Biomaterials, Radboud University Nijmegen Medical Center, Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
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93
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Na K, Kim SW, Sun BK, Woo DG, Yang HN, Chung HM, Park KH. Osteogenic differentiation of rabbit mesenchymal stem cells in thermo-reversible hydrogel constructs containing hydroxyapatite and bone morphogenic protein-2 (BMP-2). Biomaterials 2007; 28:2631-7. [PMID: 17331575 DOI: 10.1016/j.biomaterials.2007.02.008] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Accepted: 02/08/2007] [Indexed: 01/16/2023]
Abstract
The aim of this study was to assess the efficacy of ectopic bone formation in a three-dimensional hybrid scaffold in combination with hydroxyapatite (HA) and poly(NiPAAm-co-AAc) as an injectable vehicle in the form of a supporting matrix for the osteogenic differentiation of rabbit mesenchymal stem cells (MSCs). Osteogenic differentiation of MSCs in the hybrid scaffold was greatly influenced by the addition of growth factors. When the osteoinduction activity of hybrid scaffold was studied following implantation into the back subcutis of nude mouse in terms of histological and biochemical examinations, significantly homogeneous bone formation was histologically observed throughout the hybrid scaffolds containing growth factor (BMP-2: bone morphogenic protein-2). The level of alkaline phosphatase activity and osteocalcin content at the implanted sites of hybrid scaffolds were significantly high for the perfusion group compared with those in static culture group. We conclude that combination of MSC-seeded hybrid scaffold containing BMP-2 was a promising method by which to enhance in vitro osteogenic differentiation of MSC and in vivo ectopic bone formation.
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Affiliation(s)
- Kun Na
- Division of Biotechnology, The Catholic University of Korea, 43-1 Yokkok2-dong, Wonmi-gu, Bucheon 420-743, Republic of Korea
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94
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Zhang S, Wright JEI, Ozber N, Uludağ H. The Interaction of Cationic Polymers and Their Bisphosphonate Derivatives with Hydroxyapatite. Macromol Biosci 2007; 7:656-70. [PMID: 17457941 DOI: 10.1002/mabi.200600286] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Conjugating proteins with bisphosphonates (BPs), a class of molecules with exceptional affinity to hydroxyapatite (HA), is a feasible means to impart bone affinity to protein-based therapeutic agents. To increase the targeting effectiveness while minimizing protein modification, a polymeric linker containing multiple copies of BPs could be constructed for protein conjugation and targeting to bone. Towards this goal, poly(L-lysine) (PLL) and poly(ethylenimine) (PEI) were utilized as the polymeric backbones to incorporate a BP, namely 2-(3-mercaptopropylsulfanyl)-ethyl-1,1-bisphosphonic acid (thiolBP), by using N-hydroxysuccinimidyl polyethylene glycol maleimide and succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate, respectively. In vitro and in vivo mineral affinity of the polymer-BP conjugates were determined in comparison with the unmodified polymers. The in vitro results indicated strong binding of the cationic polymers to HA in their unmodified form. BP conjugation did not enhance the inherent mineral affinity of the polymers; in contrast, certain modifications negatively affected the polymers' binding to the HA. In vivo results from a subcutaneous implant model in rats also showed no significant difference in mineral affinity of the BP modified and unmodified PEI. We conclude that thiolBP conjugation to the cationic polymers PLL and PEI was not beneficial for increasing the mineral affinity of the polymeric molecules. The strong interaction between the cationic polymers and HA may make the polymers suitable for imparting mineral affinity to bone-acting therapeutics.
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Affiliation(s)
- Sufeng Zhang
- Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, Edmonton, AB, T6G 2G6, Canada
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95
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Issa JPM, do Nascimento C, Bentley MVLB, Del Bel EA, Iyomasa MM, Sebald W, de Albuquerque RF. Bone repair in rat mandible by rhBMP-2 associated with two carriers. Micron 2007; 39:373-9. [PMID: 17482469 DOI: 10.1016/j.micron.2007.03.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 10/23/2022]
Abstract
This study evaluated the quantity and quality of newly formed bone, stimulated by rhBMP-2 in combination with monoolein or chitosan gel as carriers, in critical bone defects created in 36 Wistar rat mandibles. Two weeks after surgery, the animals were anesthetized with 37.5% urethane submitted to perfusion and the hemi-mandibles removed for histological and histomorphometrical analysis. The results showed that there was a statistical difference between groups of animals receiving or not rhBMP-2 (p<0.05). Newly formed bone was more intense in the occlusal region, followed by the basal and middle regions, respectively. Both carriers, monoolein and chitosan gels were adequate for defect filling and control of protein release.
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96
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Sohier J, Hamann D, Koenders M, Cucchiarini M, Madry H, van Blitterswijk C, de Groot K, Bezemer JM. Tailored release of TGF-β1 from porous scaffolds for cartilage tissue engineering. Int J Pharm 2007; 332:80-9. [PMID: 17056215 DOI: 10.1016/j.ijpharm.2006.09.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 09/19/2006] [Accepted: 09/21/2006] [Indexed: 12/25/2022]
Abstract
In view of cartilage tissue engineering, the possibility to prepare porous scaffolds releasing transforming growth factor-beta(1) (TGF-beta(1)) in a well controlled fashion was investigated by means of an emulsion-coating method. Poly(ether-ester) multiblock copolymers were used to prepare emulsions containing TGF-beta(1) which were subsequently applied onto prefabricated scaffolds. This approach resulted in defined porous structures (66%) with interconnected porosity, suitable to allow tissue ingrowth. The scaffolds were effectively associated with TGF-beta(1) and allowed to tailor precisely the release of the growth factor from 12 days to more than 50 days by varying the copolymer composition of the coating. An incomplete release was measured by ELISA, possibly linked to the rapid concentration decrease of the protein in solution. The released growth factor retained its biological activity as was assessed by a cell proliferation assay and by the ability of the released protein to induce chondrogenic differentiation of bone marrow-derived mesenchymal stem cells. However, exact bioactivity quantification was rendered difficult by the protein concentration decrease during storage. Therefore, this study confirms the interest of poly(ether-ester) multiblock copolymers for controlled release of growth factors, and indicates that emulsion-coated scaffolds are promising candidates for cartilage tissue engineering applications requiring precise TGF-beta(1) release rates.
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Affiliation(s)
- J Sohier
- OctoPlus, Zernikedreef 12, 2333 CL, Leiden, The Netherlands.
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97
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Takahashi Y, Yamamoto M, Yamada K, Kawakami O, Tabata Y. Skull Bone Regeneration in Nonhuman Primates by Controlled Release of Bone Morphogenetic Protein-2 from a Biodegradable Hydrogel. ACTA ACUST UNITED AC 2007; 13:293-300. [PMID: 17504062 DOI: 10.1089/ten.2006.0088] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The objective of this study was to investigate the feasibility of biodegradable gelatin hydrogels as the controlled-release carrier of bone morphogenetic protein-2 (BMP-2) to enhance bone regeneration at a skull defect of nonhuman primates. Hydrogels with 3 different water contents were prepared through glutaraldehyde crosslinking of gelatin with an isoelectric point of 9.0 under varied reaction conditions. A critical-sized defect (6 mm in diameter) was prepared at the skull bone of skeletally mature cynomolgus monkeys, and gelatin hydrogels incorporating various doses of BMP-2 were applied to the defects. When the bone regeneration was evaluated by soft radiography and bone mineral density (BMD) examinations, the gelatin hydrogel incorporating BMP-2 exhibited significantly higher osteoinduction activity than did an insoluble bone matrix that incorporated BMP-2 (one of the best osteoinduction systems), although the activity depended on the water content of hydrogels. BMD enhancement was highest for the gelatin hydrogel that had a water content of 97.8 wt% among all types of hydrogels. Moreover, the gelatin hydrogel enabled BMP-2 to induce the bone regeneration in nonhuman primates even at low doses. We conclude that the controlled release of BMP-2 for a certain time period was essential to inducing the osteoinductive potential of BMP-2.
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Affiliation(s)
- Yoshitake Takahashi
- Department of Biomaterials, Field of Tissue Engineering, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan
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Alam S, Ueki K, Marukawa K, Ohara T, Hase T, Takazakura D, Nakagawa K. Expression of bone morphogenetic protein 2 and fibroblast growth factor 2 during bone regeneration using different implant materials as an onlay bone graft in rabbit mandibles. ACTA ACUST UNITED AC 2007; 103:16-26. [PMID: 17178489 DOI: 10.1016/j.tripleo.2006.01.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Revised: 12/25/2005] [Accepted: 01/23/2006] [Indexed: 11/28/2022]
Abstract
OBJECTIVES The purpose of this study was to histologically and immunohistochemically evaluate bone regeneration using 3 different implant materials in rabbit mandibles and to compare the bone regenerative capability of these materials in an animal model. STUDY DESIGN Adult male Japanese white rabbits (n = 48; 12-16 wks old; 2.5-3.0 kg) were divided into 4 groups, consisting of 12 animals each. The implant materials were beta-tricalcium phosphate (beta-TCP), autologous bone derived from the radius, and recombinant human bone morphogenetic protein 2 (rhBMP-2) with polylactic acid/polyglycolic acid copolymer and gelatin sponge (PGS) complex. After incising along the inferior border of the mandible, the materials were implanted as only grafts and covered by titanium mesh with screws. No material was implanted into the control group. The rabbits were killed at 2, 4, 8, 12, and 24 wks postoperatively, and formalin-fixed specimens containing titanium mesh were embedded in acrylic resin. The specimens were stained with hematoxylin and eosin. For immunohistochemical analysis, the specimens were treated with BMP-2 and fibroblast growth factor 2 (FGF-2) antibodies. Finally, they were examined microscopically. RESULTS The autologous bone induced substantially more new bone formation compared with beta-TCP at 4 wks postoperatively. However, rhBMP-2/PGS induced new bone formation at 8 wks postoperatively. No growth of bony tissue was observed in the control group at any period. In the autologous bone and rhBMP-2/PGS groups, both BMP-2 and FGF-2 were observed later in the beta-TCP group than in other groups. CONCLUSION This study suggests that autologous bone as well as rhBMP-2/PGS implants induce expression of both BMP-2 and FGF-2 specifically at the operated sites, even at early stages.
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Affiliation(s)
- Shamiul Alam
- Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kanazawa University, Kanazawa and Toyama, Japan
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Moroni L, Schotel R, Sohier J, de Wijn JR, van Blitterswijk CA. Polymer hollow fiber three-dimensional matrices with controllable cavity and shell thickness. Biomaterials 2006; 27:5918-26. [PMID: 16935328 DOI: 10.1016/j.biomaterials.2006.08.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 08/08/2006] [Indexed: 10/24/2022]
Abstract
Hollow fibers find useful applications in different disciplines like fluid transport and purification, optical guidance, and composite reinforcement. In tissue engineering, they can be used to direct tissue in-growth or to serve as drug delivery depots. The fabrication techniques currently available, however, do not allow to simultaneously organize them into three-dimensional (3D) matrices, thus adding further functionality to approach more complicated or hierarchical structures. We report here the development of a novel technology to fabricate hollow fibers with controllable hollow cavity diameter and shell thickness. By exploiting viscous encapsulation, a rheological phenomenon often undesired in molten polymeric blends flowing through narrow ducts, fibers with a shell-core configuration can be extruded. Hollow fibers are then obtained by selective dissolution of the inner core polymer. The hollow cavity diameter and the shell thickness can be controlled by varying the polymers in the blend, the blend composition, and the extrusion nozzle diameter. Simultaneous with extrusion, the extrudates are organized into 3D matrices with different architectures and custom-made shapes by 3D fiber deposition, a rapid prototyping tool which has recently been applied for the production of scaffolds for tissue engineering purposes. Applications in tissue engineering and controlled drug delivery of these constructs are presented and discussed.
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Affiliation(s)
- Lorenzo Moroni
- Institute for BioMedical Technology (BMTI), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
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Ruhé PQ, Boerman OC, Russel FGM, Mikos AG, Spauwen PHM, Jansen JA. In vivo release of rhBMP-2 loaded porous calcium phosphate cement pretreated with albumin. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2006; 17:919-27. [PMID: 16977389 DOI: 10.1007/s10856-006-0181-z] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2005] [Accepted: 08/23/2005] [Indexed: 05/11/2023]
Abstract
In this study, the release of rhBMP-2 loaded porous Ca-P cement was studied in vitro and in vivo. We hypothesized that adsorption sites of Ca-P ceramic with high affinity for rhBMP-2 can be blocked by pretreatment of the ceramic with albumin prior to rhBMP-2 loading, which would result in weaker rhBMP-2 binding and enhanced release of rhBMP-2. Preset porous Ca-P cement discs with a diameter of 6.35 mm (volume: 75 mm3) were pretreated by incubation in a solution of 10% rat serum albumin for 24 h or in ddH2O (control group) prior to administration of 5 mug radiolabeled 131I-rhBMP-2. Release was assessed in vitro in phosphate buffered saline (PBS) and fetal calf serum and in vivo by longitudinal scintigraphic imaging of radiolabeled 131I-rhBMP-2 and gamma counting of dissected implants. In vitro release from pretreated discs was higher during the first day. For both formulations, release in PBS was limited compared to release in serum. In vivo release considerably exceeded in vitro release. In vivo release kinetics showed no significant difference of half-lives between pretreated and control discs. Both formulations showed sustained release during at least 4 weeks. Ex vivo gamma counting of retrieved samples confirmed scintigraphic results and showed that the capsule and surrounding tissues only contained a minor fraction rhBMP-2. We conclude that 1. scintigraphy of 131I-labeled rhBMP-2 provides a reliable method for longitudinal measurement of rhBMP-2 release kinetics in vivo. 2. albumin pretreatment of porous Ca-P cement does not results in relevant increase of initial release of rhBMP-2 in vivo, and 3. preset rhBMP-2 loaded porous Ca-P cement discs exhibit one phase exponential release kinetics in the rat ectopic model, characterized by a retention of 20-30% after 4 weeks.
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Affiliation(s)
- P Q Ruhé
- Department of Perio-Dontology and Biomaterials, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
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