Effect of rhBMP-2 and VEGF in a vascularized bone allotransplant experimental model based on surgical neoangiogenesis
ABSTRACT We have demonstrated survival of living allogeneic bone without long-term immunosuppression using short-term immunosuppression and simultaneous creation of an autogenous neoagiogenic circulation. In this study, bone morphogenic protein-2 (rhBMP-2), and/or vascular endothelial growth factor (VEGF), were used to augment this process. Femoral diaphyseal bone was transplanted heterotopically from 46 Dark Agouti to 46 Lewis rats. Microvascular repair of the allotransplant nutrient pedicle was combined with intra-medullary implantation of an autogenous saphenous arteriovenous (AV) bundle and biodegradable microspheres containing buffer (control), rhBMP-2 or rhBMP-2 + VEGF. FK-506 given daily for 14 days maintained nutrient pedicle flow during angiogenesis. After an 18 weeks survival period, we measured angiogenesis (capillary density) from the AV bundle and cortical bone blood flow. Both measures were greater in the combined (rhBMP-2 + VEGF) group than rhBMP-2 and control groups (p < 0.05). Osteoblast counts were also higher in the rhBMP-2 + VEGF group (p < 0.05). A trend towards greater bone formation was seen in both rhBMP2 + VGF and rhBMP2 groups as compared to controls (p = 0.059). Local administration of VEGF and rhBMP-2 augments angiogenesis, osteoblastic activity and bone blood flow from implanted blood vessels of donor origin in vascularized bone allografts. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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ABSTRACT: Adipose-derived stem cells (ASCs) hold promise for bone regeneration but possess inferior osteogenesis potential. Allotransplantation of ASCs engineered with the BMP2/VEGF-expressing baculoviruses into rabbits healed critical-size segmental bone defects. To translate the technology to clinical applications, we aimed to demonstrate massive bone healing in minipigs that more closely mimicked the clinical scenarios, using a new hybrid baculovirus system consisting of BacFLPo expressing the codon-optimized FLP recombinase (FLPo) and the substrate baculovirus harboring the transgene flanked by Frt sequences. Co-transduction of minipig ASCs (pASCs) with BacFLPo and the substrate baculovirus enabled transgene cassette excision, recombination and minicircle formation in ≈73.7% of pASCs, which substantially prolonged the transgene (BMP2 and VEGF) expression to 28 days. When encoding BMP2, the FLPo/Frt-based system augmented the pASCs osteogenesis. Allotransplantation of the BMP2/VEGF-expressing pASCs into minipigs healed massive segmental bone defects (30 mm in length) at the mid-diaphysis of femora, as evaluated by computed tomography, positron emission tomography, histology, immunohistochemical staining and biochemical testing. The defect size was ≈15% of femoral length in minipigs and was equivalent to ≈60-70 mm of femoral defect in humans, thus the healing using pASCs engineered with the FLPo/Frt-based baculovirus represented a remarkable advance for the treatment of massive bone defects. Copyright © 2015 Elsevier Ltd. All rights reserved.Biomaterials 05/2015; 50. DOI:10.1016/j.biomaterials.2015.01.052 · 8.31 Impact Factor
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ABSTRACT: Nowadays, open anatomic reduction and internal fixation can be considered as a valuable treatment for displaced intra-articular fractures of the calcaneus. However, the application of a calcaneal plate via an extensile lateral approach is at risk for a substantial rate of complications including delayed healing, skin necrosis, or infection. There is some evidence that a limited exposure might contribute to a decreased soft tissue complication rate bearing in mind that most minimally invasive techniques have to accept a reduced primary stability compared with the open application of an angular stable plate. Recently, an intrafocal minimal invasive reduction technique has been established employing an intramedullary nail for fracture stabilisation and support of the subtalar joint. The aim of this study was to compare the primary biomechanical performance of the new device versus lateral angular stable plating.Injury 10/2013; 45. DOI:10.1016/j.injury.2013.10.031 · 2.46 Impact Factor
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ABSTRACT: The treatment of large, non-healing bone defects remains a clinical challenge, and has driven efforts toward the development of new approaches to engineer vascularized bone grafts. Despite great advances in bone tissue engineering over the past decade, clinical translation of stem cell-based strategies has been limited. This article discusses the hurdles blocking the effective application of stem cell-based regeneration of mature bone with perfusable vascular networks as well as avenues for potentially overcoming those hurdles. Particular focus is placed on the combination of autologous heterogeneous cell sources with key regenerative growth factors to mimic the complex cellular and biochemical environments that occur during normal bone healing. Understanding how to guide the intrinsic self-assembly mechanisms of these cells may increase their regenerative efficacy and enable in situ tissue morphogenesis. The development of more effective, safer, and simpler approaches to engineer vascularized bone grafts may bring stem cell-based approaches closer to wider clinical application.02/2014; 3:75–82. DOI:10.1016/j.coche.2013.12.002