Histology showing DIC-, TRAP-, ALP-, and hematoxylin-stained sections of the critical sized defects after 4 weeks of implantation with Healos along with BMSCs, with or without rhBMP-2 Full calvarial sections (scale bars: 1000 μm), magnified images a–d (scale bar: 50 μm). DIC sections show activity of GFP reporters in the regenerated tissues colocalized with alizarin complexone (AC). Bright green host-derived cells as well as very few donor cell derived bright blue cells are observed, lined with a red mineralizing AC label. These are mature osteoblasts. Host-derived light green elongated cells form a periosteum-like layer is seen at the periphery of the defects. TRAP: Bright yellow stain colocalized with light green/blue cells represents TRAP positive osteoclasts. ALP: Red color indicates ALP positive cells. Cell nuclei are stained white with DAPI. (ˆ) Early woven bone with disorganized mineralized, ALP positive matrix; (*) host-derived fibroblastic periosteum-like layer.