Fig. 4.

Mineralized bone formation after ectopic implantation of 3D bio-printed hydrogel scaffolds with different densities of BMSCs. (a) X-ray images of rats' posterior gluteus muscle pouches implanted with biological scaffolds at week 2, 4 and 8. Scale bar: 5 ​mm. (b) A schematic illustration of isolation of mineralized biological scaffolds from rat posterior gluteal muscle pouches. (c) EDS energy spectrum analysis of mineralized scaffolds. Scanning electron micrographs of mineralized nodules, distribution of P and Ca elements, and spectrums of various elemental compositions are shown. (d) Micro-CT imaging of biological scaffolds with different densities of BMSCs implanted in rat muscle pouches after 2, 4, and 8 weeks (silver color represents mineralized bone, yellow represents fibrous soft tissue) and (e) the corresponding bone volume fraction. Scale bar: 4 ​mm ^αp<0.05 vs T0; ^βp<0.05 vs T5; ^γp<0.05 vs T6; ^δp<0.05 vs T7. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)