Fig. 6. In vivo implantation and vascularization within 3D bioprinted bone constructs. (A) Two bioprinted constructs after 21 day in vitro culture were subcutaneously implanted in the athymic mouse (as indicated by black arrows); (B) overall view of explanted constructs after 4 week subcutaneous implantation (scale bar: 5 mm); (C) representative images of H&E staining (scale bar: 200 μm); (D) IHC staining for CD31 (green), αSMA (red), and nuclei (blue) within 3D bioprinted constructs (scale bar: 50 μm). The white arrows indicate the formed microvessels with lumen structures, and the black arrows indicate the murine erythrocytes within blood vessels. The asterisks indicate the PCL/HAp scaffold strand areas; quantification of CD31 positive vascular-network within 3D bioprinted constructs in hypoxia and normoxia groups by measuring the microvessel density (E) and microvessel area distribution (F) (two images per sample from the images of five scaffold samples, 10 images in total).