HE-stained sections at 4 weeks PI of HC100 (a), HC200 (b), and HC300 (c). Overviews (a-c); scale bars, 500 μm. Magnified images (A1-1-C1-1, A2-1-C2-1, and A3-1-C3-1); images of the regions A1-1-C1-1, A2-1-C2-1, and A3-1-C3-1 shown in images a-c; scale bars, 50 μm. Higher magnified images (A1-2-C1-2, A2-2-C2-2, and A3-2-C3-2); images of the regions A1-2-C1-2, A2-2-C2-2, and A3-2-C3-2 shown in images A1-1-C1-1, A2-1-C2-1, and A3-1-C3-1; scale bars, 20 μm. “#,” “NB,” and “OB” indicate strut, new bone, and osteoblast, respectively. CD31-stained sections of HC100 (d), HC200 (e), and HC300 (f); scale bars: 20 μm. Yellow arrowheads indicate vascular endothelial cells. “BV” indicates blood vessel. MT-stained sections of HC100 (g), HC200 (h), and HC300 (i); scale bars: 20 μm. Green arrowheads indicate vascular endothelium.