Delivery of VEGFA in bone marrow stromal cells seeded in copolymer scaffold enhances angiogenesis, but is inadequate for osteogenesis as compared with the dual delivery of VEGFA and BMP2 in a subcutaneous mouse model (original) (raw)
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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.
Biomaterials, 2008
The capacity to deliver, temporally, bioactive growth factors in combination with appropriate progenitor and stem cells to sites of tissue regeneration promoting angiogenesis and osteogenesis offers therapeutic opportunities in regenerative medicine. We have examined the bone regenerative potential of encapsulated vascular endothelial growth factor (VEGF 165 ) biodegradable poly(DL-lactic acid) (PLA) scaffolds created using supercritical CO 2 fluid technology to encapsulate and release solvent-sensitive and thermolabile growth factors in combination with human bone marrow stromal cells (HBMSC) implanted in a mouse femur segmental defect (5 mm) for 4 weeks. HBMSC seeded on VEGF encapsulated PLA scaffolds showed significant bone regeneration in the femur segmental defect compared to the scaffold alone and scaffold seeded with HBMSC as analysed by indices of increased bone volume (BV mm 3 ), trabecular number (Tb.N/mm) and reduced trabecular separation (Tb.Sp. mm) in the defect region using micro-computed tomography. Histological examination confirmed significant new bone matrix in the HBMSC seeded VEGF encapsulated scaffold group as evidenced by Sirius red/alcian blue and Goldner's trichrome staining and type I collagen immunocytochemistry expression in comparison to the other groups. These studies demonstrate the ability to deliver, temporally, a combination of VEGF released from scaffolds with seeded HBMSC to sites of bone defects, results in enhanced regeneration of a bone defect.
The major challenge for biomaterials in bone regeneration is a good integration with the host tissue, in which a proper vasculatization is crucial. Calcium phosphate (CP) materials have gain importance in bone regeneration since it has been proved that they stimulate the formation of bone. However, little is known about their angiogenic potential. Recent findings in our group suggest that Ca 2+ have a role in angiogenesis 1,2,3. In this study we developed different Ca 2+ releasing scaffolds by combining different sol-gel CP degradable nanoparticles (containing only Ca and P) with electrospun polylactic acid (PLA) nanofibers. Scaffolds were seeded with human mesenchymal stem cells (hMSCs) and cultured in both regular (RM) and osteogenic (OM) media. Cell proliferation, Alkaline Phosphatase (ALP) activity, VEGF synthesis and L-lactate release were assessed. Angiogenesis was examined in vitro by HUVEC tube formation and in vivo by using the chick choriallantoic membrane (CAM) angiogenic model. Scaffolds showed a long term (up to 20 days) Ca 2+ release in both culture media. The presence of the particles in the scaffolds enhanced hMSCs adhesion and increased their proliferation as well as the ALP activity in OM. hMSCs substantially increased their production of L-lactate and VEGF when seeded on the scaffolds containing the particles in RM. However, this increase was minimized when cultured in OM. HUVEC showed an enhancement in tube formation when cultured in the conditioned media obtained from culturing the hMSCs on the scaffolds. This time, no differences were found between the scaffolds with or without particles. Finally, the CAM assay showed a significant increase in the formation of new blood vessels for the scaffolds containing the particles. Their angiogenic response was similar to a VEGF loaded PLA fibers used as a positive control. We demonstrate that the presence of the Ca 2+ releasing particles enhanced several angiogenic parameters. However, some of these parameters were significantly reduced in OM due to the osteogenic differentiation of hMSCs.
Biomaterials, 2013
Rapid vascularisation of tissue-engineered osteogenic grafts is a major obstacle in the development of regenerative medicine approaches for bone repair. Vascular endothelial growth factor (VEGF) is the master regulator of vascular growth. We investigated a cell-based gene therapy approach to generate osteogenic grafts with an increased vascularization potential in an ectopic nude rat model in vivo, by genetically modifying human bone marrow-derived stromal/stem cells (BMSC) to express rat VEGF. BMSC were loaded onto silicate-substituted apatite granules, which are a clinically established osteoconductive material. Eight weeks after implantation, the vascular density of constructs seeded with VEGF-BMSC was 3-fold greater than with control cells, consisting of physiologically structured vascular networks with both conductance vessels and capillaries. However, VEGF specifically caused a global reduction in bone quantity, which consisted of thin trabeculae of immature matrix. VEGF did not impair BMSC engraftment in vivo, but strongly increased the recruitment of TRAP-and Cathepsin K-positive osteoclasts. These data suggest that VEGF over-expression is effective to improve the vascularization of osteogenic grafts, but also has the potential to disrupt bone homoeostasis towards excessive degradation, posing a challenge to its clinical application in bone tissue engineering.
Combined Angiogenic and Osteogenic Factor Delivery for Bone Regenerative Engineering
Bentham Science Publishers
Both osteogenesis and angiogenesis are integrated parts of bone growth and regeneration. Combined delivery of osteogenic and angiogenic factors is a novel approach in bone regenerative engineering. Exogenous addition of mesenchymal stem cells (MSCs), vascular endothelial growth factor (VEGF) and bone morphogenetic proteins (BMPs) together with an osteoconductive scaffold is a very promising method to enhance bone repair. This concept has been incorporated into the development of new strategies for bone tissue engineering and significant advancements have been made in last 10 years. In contrary to previous belief that VEGF modulates bone repair only by enhancing angiogenesis in the proximity of bone injury, recent evidence also suggests that cross-talk between VEGF and BMP signaling pathways in MSCs promotes osteoblastic differentiation of MSCs which aids in fracture repair. Future studies should focus on cross-talk between angiogenesis and osteogenesis, optimization of VEGF/BMP ratios, selection of the most potent BMPs, and optimization of delivery methods for VEGF and BMP. Recent discoveries from basic research including effective delivery of growth factors and cells to the area of interest will help bring VEGF plus BMP for bone healing from the bench to the patient's bedside.
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]
Microvascular Research, 2008
This is a postprint of an article published in Klöpper, J., Lindenmaier, W., Fiedler, U., Mehlhorn, A., Stark, G.B., Finkenzeller, G. High efficient adenoviral-mediated VEGF and Ang-1 gene delivery into osteogenically differentiated human mesenchymal stem cells (2008) Microvascular Research, 75 (1), pp. 83-90. Abstract Survival of ex vivo constructed tissues after transplantation is limited by insufficient oxygen and nutrient supply. Therefore, strategies aiming at improvement of neovascularization of engineered tissues are a key issue in tissue engineering applications. This in vitro study aimed at exploring the usability of osteogenically differentiated human mesenchymal stem cells (MSCs) as carriers of the angiogenic growth factor genes vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) for therapeutic angiogenesis in bone tissue engineering. The ex vivo adenoviral vector mediated transduction into osteogenically differentiated MSCs revealed a highly efficient and long lasting expression of the transgenes. Biological activity of VEGF and Ang-1 secreted from transduced cells was confirmed by analyzing the sprouting, proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) in response to conditioned medium obtained from transduced cells. The transduced osteogenically differentiated MSCs described in this report may be suitable for inducing neovascularization in bone tissue engineering applications.
Biomaterials, 2010
Although vascularized tissue-engineered bone grafts (TEBG) have been generated ectopically in several studies, the use of prevascularized TEBG for segmental bone defect repair are rarely reported. In current study, we investigated the efficacy of prevascularized TEBG for segmental defect repair. The segmental defects of 15 mm in length were created in the femurs of rabbits bilaterally. In treatment group, the osteotomy site of femur was implanted with prevascularized TEBG, which is generated by seeding mesenchymal stem cells (MSCs) into b-TCP scaffold, and prevascularization with the insertion of femoral vascular bundle into the side groove of scaffold; whereas in the control group, only MSC mediated scaffolds (TEBG) were implanted. The new bone formation and vascularization were investigated and furthermore, the expression of endogenous vascular endothelial growth factor (VEGF) which might express during defect healing was evaluated, as well. At 4, 8, and 12 weeks postoperatively, the treatment of prevascularized TEBG led to significantly higher volume of regenerated bone and larger amount of capillary infiltration compared to non-vascularized TEBG. The expression of VEGF in mRNA and protein levels increased with implantation time and peaked at 4 weeks postoperatively, followed by a slow decrease, however, treatment group expressed a significant higher level of VEGF than control group throughout the whole study. In conclusion, this study demonstrated that prevascularized TEBG by insertion of vascular bundle could significantly promote the new bone regeneration and vascularization compared to non-vascularized TEBG, which could be partially explained by the up-regulated expression of VEGF.
Tissue Engineering Part A, 2013
The ideal bone tissue-engineered (TE) construct remains to be found, although daily discoveries significantly contribute to improvements in the field and certainly have valuable long-term outcomes. In this work, different TE elements, aiming at bone TE applications, were assembled and its effect on the expression of several vascularization/angiogenesis mediators analyzed. Starch/polycaprolactone (SPCL) scaffolds, obtained by two different methodologies, were combined with fibrin sealant (Baxter Ò), human adipose-derived stem cells (hASCs), and growth factors (vascular endothelial growth factor [VEGF] or fibroblast growth factor-2 [FGF-2]), and implanted in vascular endothelial growth factor receptor-2 (VEGFR2)-luc transgenic mice. The expression of VEGFR2 along the implantation of the designed constructs was followed using a luminescence device (Xenogen Ò) and after 2 weeks, the explants were retrieved to perform histological analysis and reverse transcriptase-polymerase chain reaction for vascularization (VEGF and VEGFR1) and inflammatory (tumor necrosis factor-alpha, interleukin-4, and interferon-gamma) markers. It was showed that SPCL scaffolds obtained by wet spinning and by fiber bonding constitute an adequate support for hASCs. The assembled TE constructs composed by fibrin sealant, hASCs, VEGF, and FGF-2 induce only a mild inflammatory reaction after 2 weeks of implantation. Additionally, the release of VEGF and FGF-2 from the constructs enhanced the expression of VEGFR2 and other important mediators in neovascularization (VEGF and VEGFR1). These results indicate the potential of VEGF or FGF-2 within a bone TE construct composed by wet-spun SPCL, fibrin sealant, and hASCs in promoting the vascularization of newly formed tissue.
Journal of Cellular and Molecular Medicine, 2009
A novel therapeutic approach for the treatment of bone defects is gene therapy assisted bone tissue engineering using bone marrow stromal cells (hBMSC). The aim of this study was to investigate the influence of human epidermal growth factor (hEGF) on proliferation and alkaline phosphatase (AP) activity of primary hBMSC in vitro. hBMSC cultures were achieved by explantation culture of bone chips. Following exposure to 0-10 ng recombinant hEGF (rhEGF)/ml cell numbers were determined by automated cell counting and cell bound AP activity was measured spectrophotometrically. hBMSC were transfected with hEGF plasmids and the proliferative effect was studied by cocultivation of transfected and untreated cells using porous cell culture inserts. The persistence of hEGF expression even after cell transfer was studied by the generation of possibly osteogenic constructs introducing transfected hBMSC in fibrin glue and bovine cancellous bone. The maximum increase in proliferation (156 +/- 7%) and AP activity (220 +/- 34%) was detected after exposition to 10 ng rhEGF/ml. In the separation chamber assay transfected cells produced hEGF concentrations up to 3.6 ng/ml, which induced a mean proliferation increase of 93% which could be significantly inhibited by a neutralizing hEGF antibody. Further, EGFsecretion of transfected hBMSC in 3D-culture was verified. Recombinant and transgenic hEGF stimulate proliferation of primary hBMSC in vitro. Lipotransfection of hBMSC with hEGF plasmids allows the transient and site directed delivery of biologically active transgenic hEGF. The introduction of mitogenic, angiogenic and chemoattractive factors in gene therapy assisted bone tissue engineering is discussed by the example of EGF.