Short-term delivery of fibrin-bound VEGF protein in osteogenic grafts: increased vascularization with efficient bone formation (original) (raw)
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European cells & materials, 2010
Bone formation and osseointegration of biomaterials are dependent on angiogenesis and vascularization. Angiogenic growth factors such as vascular endothelial growth factor (VEGF) were shown to promote biomaterial vascularization and enhance bone formation. However, high local concentrations of VEGF induce the formation of malformed, nonfunctional vessels. We hypothesized that a continuous delivery of low concentrations of VEGF from calcium phosphate ceramics may increase the efficacy of VEGF administration.VEGF was co-precipitated onto biphasic calcium phosphate (BCP) ceramics to achieve a sustained release of the growth factor. The co-precipitation efficacy and the release kinetics of the protein were investigated in vitro. For in vivo investigations BCP ceramics were implanted into critical size cranial defects in Balb/c mice. Angiogenesis and microvascularization were investigated over 28 days by means of intravital microscopy. The formation of new bone was determined histomorpho...
The proangiogenic potential of a novel calcium releasing biomaterial: Impact on cell recruitment
Acta Biomaterialia, 2015
Insufficient angiogenesis remains a major hurdle in current bone tissue engineering strategies. An extensive body of work has focused on the use of angiogenic factors or endothelial progenitor cells. However, these approaches are inherently complex, in terms of regulatory and methodologic implementation, and present a high cost. We have recently demonstrate the potential of electrospun poly(lactic acid) (PLA) fiber-based membranes, containing calcium phosphate (CaP) ormoglass particles, to elicit angiogenesis in vivo, in a subcutaneous model in mice. Here we have devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a (Hydroxypropyl)methyl cellulose (HPMC) matrix, with the capacity to release calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. The bone regeneration kinetics was dependent on the Ca 2+ release rate, with the faster Ca 2+ release composite gel showing improved bone repair at 3 weeks, in relation to control. In the same line, improved angiogenesis could be observed for the same gel formulation at 6 weeks post implantation. This methodology allows to integrate two fundamental processes for bone tissue regeneration while using a simple, cost effective, and safe approach.
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.
Journal of Tissue Engineering and Regenerative Medicine, 2015
A major limitation with current tissue-engineering approaches is creating functionally vascularized constructs that can successfully integrate with the host; this often leads to implant failure, due to avascular necrosis. In order to overcome this, the objective of the present work was to develop a method to incorporate growth factor-eluting alginate microparticles (MPs) into freeze-dried, collagen-based scaffolds. A collagen-hydroxyapatite (CHA) scaffold, previously optimized for bone regeneration, was functionalized for the sustained delivery of an angiogenic growth factor, vascular endothelial growth factor (VEGF), with the aim of facilitating angiogenesis and enhancing bone regeneration. VEGF was initially encapsulated in alginate MPs by spray-drying, producing particles of < 10 μm in diameter. This process was found to effectively encapsulate and control VEGF release while maintaining its stability and bioactivity post-processing. These VEGF-MPs were then incorporated into CHA scaffolds, leading to homogeneous distribution throughout the interconnected scaffold pore structure. The scaffolds were capable of sustained release of bioactive VEGF for up to 35 days, which was proficient at increasing tubule formation by endothelial cells in vitro. When implanted in vivo in a rat calvarial defect model, this scaffold enhanced vessel formation, resulting in increased bone regeneration compared to empty-defect and VEGF-free scaffolds. This biologically functionalized scaffold, composed entirely of natural-based materials, may offer an ideal platform to promote angiogenesis and tissue regeneration.
Tissue Engineering Part A, 2010
Background: Bone substitutes should ideally promote rapid vascularization, which could be accelerated if these substitutes were vitalized by autologous cells. Although adequate engraftment of porous poly(L-lactideco-glycolide) (PLGA) scaffolds has been demonstrated in the past, it has not yet been investigated how vascularization is influenced by vitalization or, more precisely, by seeding PLGA scaffolds with osteoblast-like cells (OLCs). For this reason, we conducted an in vivo study to assess host angiogenic and inflammatory responses after the implantation of PLGA scaffolds vitalized with isogeneic OLCs. Materials and Methods: OLCs were seeded on collagen-coated PLGA scaffolds that were implanted into dorsal skinfold chambers in BALB/c mice (n ¼ 8). Two further groups of animals received either collagen-coated (n ¼ 8) or uncoated PLGA scaffolds (n ¼ 8). Animals that received chambers without implants served as controls (n ¼ 8). Angiogenesis, neovascularization, and leukocyte-endothelial cell interaction were analyzed for 14 days using intravital fluorescence microscopy. Results: PLGA scaffolds with and without OLCs showed a temporary increase in leukocyte recruitment. At day 3 after implantation, a marked angiogenic host tissue response was observed in close vicinity of all scaffolds studied. At days 6 and 10, the angiogenic response was significantly higher (p < 0.05) in PLGA scaffolds vitalized with OLCs than in uncoated or collagen-coated PLGA scaffolds. The majority of OLCs, however, died within 14 days after implantation. Conclusion: Our study demonstrates that PLGA scaffold vitalization with OLCs accelerates the angiogenic response in the surrounding host tissue. Bone substitutes created by tissue engineering may thus be superior to nonvitalized substitutes although the seeded cells do not survive for long periods.
Journal of Biomedical Materials Research Part A, 2008
Scaffolds for tissue engineering of bone should mimic bone matrix and promote vascular ingrowth. Whether synthetic hydroxyapatite and acellular dentin, both materials composed from calcium phosphate, fulfill these material properties has not been studied yet. Therefore, we herein studied in vivo the host angiogenic and inflammatory response to these biomaterials. Porous scaffolds of hydroxyapatite and isogeneic acellular dentin were implanted into the dorsal skinfold chamber of balb/c mice. Additional animals received perforated implants of isogeneic calvarial bone displaying pores similar in size and structure to those of both scaffolds. Chambers of animals without implants served as controls. Angiogenesis and neovascularization as well as inflammatory leukocyteendothelial cell interaction and microvascular leakage were analyzed over a 14-day time period using intravital fluorescence microscopy. Implantation of both hydroxyapatite and dentin scaffolds showed a slight increase in leukocyte recruitment compared with controls. This was associated with an elevation of microvascular permeability, which was comparable to that observed in response to isogeneic bone. In addition, hydroxyapatite as well as dentin scaffolds induced a marked angiogenic response, which resulted in complete vascularization of the implants until day 14. Of interest, in hydroxyapatite scaffolds, the newly formed capillaries were not as densely meshed as in dentin scaffolds, in which the functional capillary density was comparable to that measured in bone implants. Hydroxyapatite and, in particular, dentin scaffolds promote vascularization and exhibit a biocompatibility comparable to that of isogeneic bone. This may guarantee the rapid incorporation of these materials into the host tissue.
Heparin modification of a biomimetic bone matrix for controlled release of VEGF
Journal of Biomedical Materials Research Part A, 2013
In this study, the effect of heparin-modified collagen type I/hydroxyapatite (HA) nanocomposites on key processes of bone regeneration-osteogenesis and angiogenesiswas characterised in vitro. Two approaches were applied for heparin modification: it was either integrated during material synthesis (in situ) or added to the porous scaffolds after their fabrication (post). Cultivation of human bone marrow-derived stromal cells (hBMSC), in heparinmodified versus heparin-free scaffolds, revealed a positive effect of the heparin modification on their proliferation and osteogenic differentiation. The amount of heparin rather than the method used for modification influenced the cell response favouring proliferation at smaller amount (30 mg/g collagen) and differentiation at larger amount (150 mg/g collagen). A co-culture of human umbilical vein endothelial cells (HUVEC) and osteogenically induced hBMSC was applied for in vitro angiogenesis studies. Pre-vascular networks have formed in the porous structure of scaffolds which were not modified with heparin or modified with a low amount of heparin (30 mg/g collagen). The modification with higher heparin quantities seemed to inhibit tubule formation. Pre-loading of the scaffolds with VEGF influenced formation and stability of the prevascular structures depending on the presence of heparin: In heparin-free scaffolds, induction of tubule formation and sprouting was more pronounced whereas heparinmodified scaffolds seemed to promote stabilisation of the pre-vascular structures. In conclusion, the modification of mineralised collagen with heparin by using both approaches was found to modulate cellular processes essential for bone regeneration; the amount of heparin has been identified to be crucial to direct cell responses.
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.
Stem cell research & therapy, 2018
In bone tissue engineering (BTE), extensive research into vascular endothelial growth factor A (VEGFA)-mediated angiogenesis has yielded inconsistent results. The aim of this study was to investigate the influence on angio- and osteogenesis of adenoviral-mediated delivery of VEGFA alone or in combination with bone morphogenetic protein 2 (BMP2) in bone marrow stromal cells (BMSC) seeded onto a recently developed poly(LLA-co-CL) scaffold. Human BMSC were engineered to express VEGFA alone or in combination with BMP2 and seeded onto poly(LLA-co-CL) scaffolds. Changes in angiogenic and osteogenic gene and protein levels were examined by quantitative reverse-transcription polymerase chain reaction (RT-PCR), PCR array, and alkaline phosphatase assay. An in vivo subcutaneous mouse model was used to investigate the effect on angio- and osteogenesis of VEGFA alone or in combination with BMP2, using microcomputed tomography (μCT), histology, immunohistochemistry, and immunofluorescence. Combi...
Tissue engineering strategies for the induction of angiogenesis using biomaterials
Journal of Biological Engineering
Angiogenesis is touted as a fundamental procedure in the regeneration and restoration of different tissues. The induction of de novo blood vessels seems to be vital to yield a successful cell transplantation rate loaded on various scaffolds. Scaffolds are natural or artificial substances that are considered as one of the means for delivering, aligning, maintaining cell connection in a favor of angiogenesis. In addition to the potential role of distinct scaffold type on vascularization, the application of some strategies such as genetic manipulation, and conjugation of proangiogenic factors could intensify angiogenesis potential. In the current review, we focused on the status of numerous scaffolds applicable in the field of vascular biology. Also, different strategies and priming approaches useful for the induction of pro-angiogenic signaling pathways were highlighted.