Evaluation of adenoviral vascular endothelial growth factor-activated chitosan/hydroxyapatite scaffold for engineering vascularized bone tissue using human osteoblasts: In vitro and in vivo studies

Bone tissue is dependent on an efficient blood supply to ensure delivery of nutrients and oxygen. One method to acquire a vascular-engineered bone tissue could be the use of an angiogenic gene-activated scaffold. In the current study, porous chitosan/hydroxyapatite (C/HA) scaffolds were fabricated via freeze-drying with desired pore size, and then combined with the adenoviral vector encoding vascular endothelial growth factor and green fluorescence protein (Ad-VEGF). Human osteoblasts were cultured and seeded on characterized scaffolds. The attachment, proliferation, and differentiation of cells on gene-activated and unactivated C/HA scaffolds were evaluated in vitro and in vivo by histo- and immunohistochemistry. Findings confirmed that human osteoblasts cultured on gene-activated C/HA scaffold secreted vascular endothelial growth factor, besides maintaining its characteristic phenotype with specific extracellular matrix production. In vivo experiments indicated that scaffolds were tissue biocompatible, and that gene-activated scaffold provided a suitable environment for neovessel formation by recruiting host endothelial cells into the newly forming ectopic bone-like tissue. This study revealed that the Ad-VEGF-activated C/HA composite scaffold has potential for vascular bone regeneration applications.