Dual delivery of an angiogenic and an osteogenic growth factor for bone regeneration in a critical size defect model

Abstract

This study investigated the effects of dual delivery of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) for bone regeneration in a rat cranial critical size defect. Four groups of scaffolds were generated with VEGF (12 μg), BMP-2 (2 μg), both VEGF (12 μg) and BMP-2 (2 μg), or no growth factor released from gelatin microparticles incorporated within the scaffold pores. These scaffolds were implanted within an 8 mm rat cranial critical size defect (n = 8-9 for each group). At 4 and 12 weeks, implants were retrieved and evaluated by microcomputed tomography (microCT) and histological scoring analysis. Additionally, 4 week animals were perfused with a radiopaque material to visualize and quantify blood vessel formation. Histological analysis revealed that for all groups at 4 weeks, a majority of the porous scaffold volume was filled with vascularized fibrous tissue; however, bone formation appeared most abundant in the dual release group at this time. At 12 weeks, both dual release and BMP-2 groups showed large amounts of bone formation within the scaffold pores and along the outer surfaces of the scaffold; osteoid secretion and mineralization were apparent, and new bone was often in close or direct contact with the scaffold interface. MicroCT results showed no significant difference among groups for blood vessel formation at 4 weeks (<4% blood vessel volume); however, the dual release group showed significantly higher bone formation (16.1±9.2% bone volume) than other groups at this time. At 12 weeks, dual release and BMP-2 groups exhibited significantly higher bone formation (39.7 ± 14.1% and 37.4 ± 18.8% bone volume, respectively) than either the VEGF group or blank scaffolds (6.3 ± 4.8% and 7.8 ± 7.1% bone volume, respectively). This work indicates a synergistic effect of the dual delivery of VEGF and BMP-2 on bone formation at 4 weeks and suggests an interplay between these growth factors for early bone regeneration. For the doses investigated, the results show that the addition of VEGF does not affect the amount of bone formation achieved by BMP-2 at 12 weeks; however, they also indicate that delivery of both growth factors may enhance bone bridging and union of the critical size defect compared to delivery of BMP-2 alone.

Titanium-Enriched Hydroxyapatite–Gelatin Scaffolds with Osteogenically Differentiated Progenitor Cell Aggregates for Calvaria Bone Regeneration

“…1), which have been previously described. [22][23][24] Briefly, 11-to 13-week-old Sprague-Dawley rats (Charles River) were anesthetized and a CSD was created on the calvaria bone using a dental trephine drill. Calvaria defects were assigned to the following experimental groups listed in Table 1.…”

Emerging Ideas: Treatment of Precollapse Osteonecrosis Using Stem Cells and Growth Factors

“…Combined use of VEGF and BMP-2 [19,24,34,35,37,40] and BMP-4 [20,25,36] showed synergistic effects in osteogenesis. It has been shown that combined use of VEGF with one of the most potent BMPs, BMP-6 [23,26], enhances osteogenesis and angiogenesis of mouse bone marrow stem cells in vitro and in vivo [8], however, the effectiveness of this therapy for ON has not been determined.…”

“…In addition to its effects on angiogenesis, VEGF plays an important role in bone growth and repair by interacting with other growth factors [35,36]. However, overexpression of VEGF actually can adversely affect osteogenesis and decrease bone formation [25,[34][35][36][37]. In our in vitro study, the optimal ratio of VEGF and BMP-6 will be determined so that the undesired effects of VEGF can be avoided in the in vivo study.…”

“…Stem cell-mediated bone regeneration augmented with combined use of VEGF and BMPs has been reported but only for BMP-2 [19,24,34,35,37,40] and BMP-4 [20,25,36]. It has been shown that VEGF enhances BMP-6-induced osteogenesis of mouse stem cells in vitro and in vivo, however, the effectiveness of this therapy for ON has not been determined [8].…”

Realizing the potential of gene-based molecular therapies in bone repair

“…(130) In particular, VEGF (131) and bFGF (132,133) have been shown to be beneficial on their own for osteogenesis and in combinations with BMPs. (134,135) Angiogenic genes have been delivered in clinical studies but not in the context of bone regeneration. VEGF-expressing AVs have been delivered for treatment of coronary heart diseases (136) and end-stage renal disease, (137) whereas pDNA-expressing VEGF have been injected for treatment of diabetic neuropathy (138) and critical limb ischemia.…”