Bone Regeneration via a Mineral Substrate and Induced Angiogenesis

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Abstract
Angiogenesis and biomineral substrates play major roles in bone development and regeneration. We hypothesized that macroporous scaffolds of biomineralized 85:15 poly(lactide-co-glycolide), which locally release vascular endothelial growth factor-165 (VEGF), would direct simultaneous regeneration of bone and vascular tissue. The presence of a bone-like biomineral substrate significantly increased regeneration of osteoid matrix (32 ± 7% of total tissue area; mean ± SD; p < 0.05) and mineralized tissue (14 ± 2%; P < 0.05) within a rat cranium critical defect compared with a non-mineralized polymer scaffold (19 ± 8% osteoid and 10 ± 2% mineralized tissue). Further, the addition of VEGF to a mineralized substrate significantly increased the generation of mineralized tissue (19 ± 4%; P < 0.05) compared with mineralized substrate alone. This appeared to be due to a significant increase in vascularization throughout VEGF-releasing scaffolds (52 ± 9 vessels/mm2; P < 0.05) compared with mineralized scaffolds without VEGF (34 ± 4 vessels/mm2). Surprisingly, there was no significant difference in total osteoid between the two samples, suggesting that increased vascularization enhances mineralized tissue generation, but not necessarily osteoid formation. These results indicate that induced angiogenesis can enhance tissue regeneration, supporting the concept of therapeutic angiogenesis in tissue-engineering strategies.