Effects of locally applied vascular endothelial growth factor (VEGF) and VEGF-inhibitor to the rabbit tibia during distraction osteogenesis (original) (raw)
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Angiogenesis Is Required for Successful Bone Induction During Distraction Osteogenesis
Journal of Bone and Mineral Research, 2005
The role of angiogenesis during mechanically induced bone formation is incompletely understood. The relationship between the mechanical environment, angiogenesis, and bone formation was determined in a rat distraction osteogenesis model. Disruption of either the mechanical environment or endothelial cell proliferation blocked angiogenesis and bone formation. This study further defines the role of the mechanical environment and angiogenesis during distraction osteogenesis.
Journal of Cranio-Maxillofacial Surgery, 2005
Background: With a hypothesis that ''angiogenesis occurs before osteogenesis,'' an experimental study using a rat model was carried out. Histological and immunohistochemical examinations of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2, -4 (BMP-2, -4) were performed at the margins of bone formation after femoral bone lengthening. Material and methods: Thirty-five Wistar rats weighing 380-400 g (11-week-old males) were used. An external fixator was applied on the femur, and an osteotomy performed under general anaesthesia. Five days after the operation, femoral lengthening was initiated at a rate of 0.8 mm/day for 8 days. The rats were sacrificed just after distraction was completed, and at 1, 3, 5, 7, 9 and 14 days after distraction. The specimens from these rats were stained with haematoxylin-eosin, VEGF, and BMP-2, -4 immunohistochemical staining, and were investigated. Results: Expression of VEGF was observed in the woven bone at the osteogenetic front and near to osteoblasts around the newly formed bone. On the other hand, expressions of BMP-2, -4 were seen in the hypertrophic chondrocytes. In the same specimen, the VEGF area was further away from the bone stump than the BMP-2, -4 areas. Conclusion: These results confirm the hypothesis that angiogenesis is induced before osteogenesis. r 2005 European Association for Cranio-Maxillofacial Surgery
Osteogenesis and Angiogenesis in Regenerating Bone during Transverse Distraction
Clinical Orthopaedics and Related Research, 2005
For some patients with a bone defect, curved deformity, or small diameter bone, transverse distraction might be better indicated than bone transport or lengthening. However, detailed quantitative evaluation of osteogenesis or angiogenesis during transverse distraction by creating a well-controlled animal model has not been done. We established a transverse distraction model of the canine tibia. A rectangular cortex was separated for a distraction fragment. Seven days after the operation, 0.5-mm distraction was applied twice daily for 14 days. After a 28-day consolidation period, the animals were sacrificed. Quantitative evaluations of the rates of mineralization and the increases of bone mineral density indicated faster mineralization and earlier corticalization of the regenerating bone in the initial stage of the consolidation period. The average blood vessel volume ratio in the distraction area was more than three times greater than in the intact contralateral tibiae. We hypothesized that adequate preservation of the marrow arteries and stability of the distraction site throughout an experimental period could induce this faster osteogenesis. Our results indicated that the transverse distraction technique was feasible. The transverse distraction technique could be indicated for patients with smalldiameter bones or with massive bone defects.
Bone, 2005
Aim of this study was the investigation of systemic biochemical regulation mechanisms of bone regeneration by angiogenic and matrixdegrading enzymes during distraction osteogenesis compared to rigid osteotomy bone healing. Serum samples of 10 otherwise healthy patients with callus distraction for lower limb-lengthening and 10 osteotomy patients undergoing elective axis correction have been collected prospectively in a standardized time schedule before and up to 6 months after the procedure. At the end of the individual investigation period, concentrations of metalloproteinases (MMP-9,-13), tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2) and the angiogenic factors angiogenin and VEGF have been detected by use of commercially available enzyme immunoassays. Results have been compared to our preliminary study on proMMP-1-3. In distraction osteogenesis, significantly elevated serum concentrations compared to baseline could be detected postoperatively for proMMP-1, MMP-9, TIMP-1, angiogenin and VEGF but not for proMMP-2, proMMP-3 or TIMP-2. In patients with rigid osteotomy healing, MMP-9, TIMP-1, TIMP-2, angiogenin and VEGF were significantly increased respectively. Comparison of both patient collectives revealed significantly higher increases of serum proMMP-1, VEGF and TIMP-1 in distraction patients during the lengthening period and significantly higher serum concentrations of TIMP-2 in late fracture healing period in osteotomy patients. Serum levels of MMP-13 were below the lowest standards, and therefore quantitative analysis was not possible. Bone regeneration in distraction osteogenesis and rigid osteotomy healing is accompanied by systemic increase of matrix-degrading and angiogenic factors in a certain time course and quantity. This might reflect biochemical regulation of local bone healing in the circulation. ProMMP-1, VEGF and TIMP-1 seem to be key regulatory factors during distraction osteogenesis.
Bone, 2008
Experimental tibial lengthening was achieved in 61 rabbits to examine the effect of continuous local infusion of recombinant human fibroblast growth factor-2 (rhFGF-2) on bone healing of the lengthened segment. The tibial diaphysis was separated by osteotomy and was subjected to slow progressive distraction (rate: 0.35 mm/12 h) using a monolateral external fixator. There were a lag phase for 1 week, a distraction phase for 2 weeks, and a consolidation phase for 5 weeks in this experiment. At various stages of distraction, rhFGF-2 was infused continuously for 2 weeks into the lengthened segment (rate: 14.28 μg/60 μl/day) using an osmotic pump implanted under the skin. Bone healing was significantly accelerated when rhFGF-2 was infused in the beginning of consolidation phase, but not in the distraction phase or in the lag phase. Infusion of normal saline (N/S) using the same osmotic pump had no effect. Dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT) studies demonstrated that rhFGF-2-treated tibia had increased bone mineral density (BMD), bone mineral content (BMC) and cortical bone thickness (CBT) when compared with N/S-treated tibia. Three-point bending test demonstrated that rhFGF-2-treated bone had significantly stronger mechanical properties than N/S-treated bone. Finally, distribution of the infused materials was checked by using Indian ink or radio-opaque. The dyes distributed widely but exclusively in the lengthened segment. Based on these results, we conclude that direct delivery of rhFGF-2 into the lengthened segment can shorten the consolidation phase of limb lengthening and the method is applicable to the clinical treatment.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2010
Because complications of distraction osteogenesis are largely related to the long duration of therapy, increasing efforts were reached to shorten treatment by using osteoconductive replacement materials incorporating bioactive molecules such as IGF-1 and TGF-b1. The controlled release of IGF-1 and TGF-b1 from coated biodegradable poly(D,L-lactide) implants could stimulate fracture healing locally. We investigated the effect of locally applied IGF-1 and TGF-b1 from IGF-1/TGF-b1-enriched polylactide membranes on fracture healing in a sheep model of delayed callus formation. Twenty-eight sheep were used for this study. Callus distraction of 1 mm/day by means of a unilateral fixator was continued for 30 days. At the beginning of the subsequent consolidation phase, either growth factors were applied locally or the defect was packed with cancellous bone, or both. The groups treated with growth factors were compared to a control group. The consolidation phase lasted for 60 days and both tibiae were dissected for histological and histomorphometric analyses. This investigation found a reduced absolute callus area in the lengthening zone in all treatment groups. The two treatment groups that received a membrane coated with growth factors showed distinctly higher relative bone areas than the groups treated with an uncoated membrane or packing of the osteotomy defect with cancellous bone. The differences in bone areas were not statistically significant. Application of the growth factors accelerated bone healing and achieved results comparable with those of established treatment methods (packing with autologous cancellous bone). The best results were achieved with a combination of both methods. '
Growth factors in distraction osteogenesis
International Orthopaedics, 1999
Although growth factors have been demonstrated during bone healing, their presence has not yet been confirmed in callus distraction. Therefore, in 3 patients we searched for cytokines during callus distraction. Bone biopsies were immuno-histochemically stained for TGF-β1, IGF-I, TGF-β type II receptor, IGF receptor, and proliferating cell nuclear antigen (PCNA). Histologically we found immature woven bone in the middle of the callus zone and increasing calcification and lamellar bone in the re-modelling zone. Osteoblasts and fibroblast-like cells in the middle zone, and osteoblasts in all zones stained for TGF-β and its receptor. The number of positive staining cells related to proliferous activity as assessed both by PCNA, and by bone density in radiographs. IGF-I could be detected everywhere. In conclusion, growth factors are present in bone formation and in areas of re-modelling during callotasis. Their relation to proliferous activity and radiographic density supports their involvement in osteogenesis.
In vitro models for the evaluation of angiogenic potential in bone engineering
Acta Pharmacologica Sinica, 2011
Role of angiogenesis in bone engineering In bone, the connection between cells and blood vessels is required to maintain skeletal integrity. In tissue engineering, a vessel network is an essential prerequisite for scaffolds to survive and integrate with existing host tissue. Activators and inhibitors of angiogenesis Vascular development is a coordinated process through three major steps, regulating (1) sprouting of endothelial cells (ECs) from mature vessels, (2) assembly of vessels to vascular structures and (3) vessel maturation and subsequent induction of quiescence [1]. Each of these steps is regulated by molecules acting on specific vascular receptors. Sprouting is induced by vascular endothelial growth factor (VEGF) [2] , which is produced by monocytes and macrophages migrated to the site of the tissue lesion and stimulated by hypoxia. Vessel cells become sensitive to VEGF after the hypoxia-induced bond of angiopoietin-2 to the endothelial receptor tyrosine kinase Tie-2. VEGF binds to receptors VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR) on EC membrane. Assembly of vessels to vascular structures is regulated by the ephrin ligands and ephrin receptor tyrosine kinases, which mediate cell-contact-dependent signalling [3]. Angiopoietins [4] and Tie-1 and-2 receptors [5]
Biomaterials, 2010
Regenerating bone tissue involves complex, temporal and coordinated signal cascades of which bone morphogenic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF 165 ) play a prominent role. The aim of this study was to determine if the delivery of human bone marrow stromal cells (HBMSC) seeded onto VEGF 165 /BMP-2 releasing composite scaffolds could enhance the bone regenerative capability in a critical sized femur defect. Alginate-VEGF 165 /P DL LA-BMP-2 scaffolds were fabricated using a supercritical CO 2 mixing technique and an alginate entrapment protocol. Increased release of VEGF 165 (750.4 AE 596.8 rg/ml) compared to BMP-2 (136.9 AE 123.4 rg/ml) was observed after 7-days in culture.