3D-printed oxygen-releasing scaffolds improve bone regeneration in mice

Low oxygen (O-2) diffusion into large tissue engineered scaffolds hinders the therapeutic efficacy of transplanted cells. To overcome this, we previously studied hollow, hyperbarically-loaded microtanks (mu tanks) to serve as O-2 reservoirs. To adapt these for bone regeneration, we fabricated biodegradable mu tanks from polyvinyl alcohol and poly (lactic-co-glycolic acid) and embedded them to form 3D-printed, porous poly-epsilon-caprolactone (PCL)-mu tank scaffolds. PCL-mu tank scaffolds were loaded with pure O-2 at 300-500 psi. When placed at atmospheric pressures, the scaffolds released O-2 over a period of up to 8 h. We confirmed the inhibitory effects of hypoxia on the osteogenic differentiation of human adipose-derived stem cells (hASCs and we validated that mu tank-mediated transient hyperoxia had no toxic impacts on hASCs, possibly due to upregulation of endogenous antioxidant regulator genes. We assessed bone regeneration in vivo by implanting O-2-loaded, hASC-seeded, PCL-mu tank scaffolds into murine calvarial defects (4 mm diameters x 0.6 mm height) and subcutaneously (4 mm diameter x 8 mm height). In both cases we observed increased deposition of extracellular matrix in the O-2 delivery group along with greater osteopontin coverages and higher mineral deposition. This study provides evidence that even short-term O-2 delivery from PCL-mu tank scaffolds may enhance hASC-mediated bone tissue regeneration.