Construction of tissue engineered bone with vascularizatio

Because the human bone tissues are essentially composite materials with anisotropic properties, making of various components of tissues with different amount, structural arrangements and function, the repairing bone defect with engineered grafts is a coordinated process, involving interplay among various determinants. Therefore we attempt to develop a systemic approach to construct tissue engineered bone, including (1) a complex scaffold materials consisting of poly-e-caprolactone (PCL) and hydroxyapatite (HA) to optimize the mechanical properties and biocompatibility; (2) a complex cells populations containing bone marrow stromal cells (MSCs)-derived osteoblast responsible for osteogenesis, and endothelial progenitor cells (EPCs)-derived endothelial cells specifying vascularization; (3) consequently a complex bone graft characterized by a precedent vascular network, used to repair mice and rat bone defects.;Multiporous PCL-HA scaffolds were developed and variety of porosities and pore sizes were created. It was found that the PCL-HA scaffolds with desired porous properties, microtopography, and mechanical properties could be fabricated by reasonable adjusting porogen ratio and dimensions. The mice and rat bone marrow-derived endothelial cells and osteoblasts could be harvested, induced and expanded in vitro with specific protocol to provide adequate cell amount for application of bone tissue engineering. To optimize biocompatibility of PCL-HA scaffold in response to relevant animal model, dose-effects of HA in PCL vehicle were investigated regarding to various cells types and sources. The biochemical testing at single-cell level revealed that biomaterials at the variety of component ratio could result in different cellular behavior. The optimal endothelial cells and osteoblasts activities could be elicited by altering the supplement of HA to PCL, on which we based the appropriate PCL-HA scaffolds for further engineered bone construction. Relying on assessments of repairing segmental femoral defects in mice and rat model, bone marrow-derived endothelial cells and osteoblasts were capable to assemble into microvascular networks and form bony matrix respectively in grafts. By precedent seeding endothelial cells, endothelial cells-depended vascularization was able to promote osteogenesis, prevent ischemic necrosis and improve the mechanical properties in engineered bone tissue. The successful outcomes provide a new therapeutic strategy for clinic bone defects.