ENGINEERING CHANNELS IN POROUS CALCIUM PHOSPHATE BIOCERAMIC SCAFFOLDS FOR BONE TISSUE REGENERATION

Inadequate nutrition exchange and slow transportation in a porous scaffold often resulted in insufficient vasculature formation, which hindered rapid bone regeneration. In this study, interconnected porous beta-tricalcium phosphate (b-TCP) scaffolds with channeled geometry were fabricated. In vitro fluid transportation and degradation of the scaffolds were performed. Cell attachment, migration, proliferation, and differentiation were carried out under both static and dynamic culturing conditions. A computational simulation model and a series of immunofluorescent staining were implemented to understand the mechanism of cell behavior in respond to different scaffolds geometry. We then implanted scaffolds into rat critical-sized calvarial defects to further evaluate channels’ function on bone regeneration in vivo. Results showed that multiple channeled geometry significantly accelerated the release of Ca2+ and increased the fluid diffusion efficiency. Moreover, multiple channels promoted human umbilical vein endothelial cells (HUVECs) infiltration, migration, besides prominently promoted alkaline phosphatase (ALP) activity, and up-regulated osteogenic gene expression in human bone marrow mesenchymal stem cells (hBMSCs) at both static and dynamic culturing conditions in vitro. The expression of both cell migration related protein a5 and angiogenesis related protein CD31 were upregulated by multiple channels in HUVECs. And the expression of mechanosensing markers, focal adhesion kinase (FAK), polymeric filamentous actin (Factin), and Yes-associated protein-1 (YAP-1) were highly stimulated by multiple channels in hBMSCs. The in vivo implantation and characterization results demonstrated more bone formation inside multiple-channeled scaffolds compared to non-channeled scaffolds. Multiple channels accelerated collagen type I, Bone Sialoprotein (Bsp), Osteocalcin (OC) protein expression prominently. The angiogenesis related protein CD31 staining displayed longer and more vasculature structures on multiple-channeled scaffolds compared to nonchanneled scaffolds. Fluorescent images of the fluorochrome labeled samples exhibited considerably more mineral deposition on multiple-channeled scaffolds than non-channeled scaffolds. All the findings suggested that the addition of multiple channels in the porous b-TCP scaffold is very promising approach to promote vascularization and bone tissue regeneration.