Nonadherent donor bone marrow cells engraft as osteoblasts and osteocytes after transplantation. (A) Representative photomicrograph of a bone/bone marrow section taken from a mouse after nonadherent marrow cell transplantation double stained with anti-GFP (black) and antiosteocalcin (red) antibodies. Several double-positive donor osteoblasts are distributed along the surface of endosteal bone, with a donor (GFP⁺) osteocyte embedded in bone. Osteocalcin-expressing host cells (H; red stain without GFP) are indicated by arrows. (B) Bone/bone marrow section double stained with anti-GFP (black) and anti-collagen l (red) antibodies. Donor osteoblasts and osteocytes were detected by red/black colocalization. Collagen-expressing host osteocytes (H) are indicated by arrows. (C) Control bone section from a mouse transplanted with nontransduced nonadherent bone marrow cells and stained with anti-GFP and isotype control antibodies. Original magnification for all panels, 1600× (400× optical, 4× digital).