Engineering Porous β-Tricalcium Phosphate (β-TCP) Scaffolds with Multiple Channels to Promote Cell Migration, Proliferation, and Angiogenesis.

Inadequate oxygen and nutrient diffusion in a porous scaffold often resulted in insufficient formation of branched vasculatures, which hindered bone regeneration. In this study, interconnected porous β-tricalcium phosphate (β-TCP) scaffolds with different geometric designs of channels were fabricated and compared to discover the functionality of structure on facilitating nutrient diffusion for angiogenesis. In vitro fluid transportation and degradation of the scaffolds were performed. Cell infiltration, migration, and proliferation of human umbilical vein endothelial cells (HUVECs) on the scaffolds were carried out under both static and dynamic culture conditions. A computational simulation model and a series of immunofluorescent staining were implemented to understand the mechanism of cell behavior in response to different types of scaffolds. Results showed that geometry with multiple channels significantly accelerated the release of Ca2+ and increased the fluid diffusion efficiency. Moreover, multiple channels promoted HUVECs' infiltration and migration in vitro. The ex vivo implantation results showed that the channels promoted cells from the rats' calvarial bone explants to infiltrate into the implanted scaffold. Multiple channels also stimulated HUVECs' proliferation prominently at both static and dynamic culturing conditions. The expression of both cell migration-related protein α5 and angiogenesis-related protein CD31 on multiple-channeled scaffolds was upregulated compared to that on the other two types of scaffolds, implying that multiple channels reinforced cell migration and angiogenesis. All the findings suggested that the geometric design of multiple channels in the porous β-TCP scaffold has promising potential to promote cell infiltration, migration, and further vascularization when implanted in vivo.