Hypoxic cells increase in vivo bone repairing ability. Calvarial defects were implanted with hypoxic (Hyp) or normoxic cells (Nor). (A) Radiographic images and densitometric analysis were performed at 6 weeks. (B) Micro-CT 3D reconstruction imaging and (C) quantitation for bone volume, bone mineral content (BMC), and bone mineral density (BMD) of newly formed tissues were performed at 6 weeks. The data are expressed as mean ± SEM. Asterisks indicate significant differences: *P < .05, **P < .01, ***P < .005. (D) Samples were harvested for histologic analysis 6 weeks later. Hematoxylin and eosin staining (H&E) for morphologic evaluation (the rectal angle area in the top panel is magnified in the middle panel) and Mallory trichrome staining for collagen deposition in hypoxic and normoxic groups. Photomicrographs were captured using an Olympus AX80 microscope equipped with a Qimaging QiCam digital camera (Qimaging). Original magnifications, 2×/0.13 NA dry objective (top), 20×/0.7 NA dry objective (middle and bottom). Arrow indicates bone area. Bar = 100 μm.