Cytokine-induced mobilization results in the specific loss of osteoblast CXCL12 expression. (A) Representative photomicrograph of CXCL12 RNA in situ from G-CSF–treated (left) and untreated (right) mouse long bones. Specific CXCL12 signal (red) was detected along endosteal surfaces (arrows) and within the bone marrow (arrowheads; n = 3-5, each group). (B) Transgenic (pOBCol2.3-GFP) mice expressing GFP in osteoblast lineage cells were treated with cytokines(n = 4-5 each group), and stromal cells were isolated and fractionated by flow cytometry into nonosteoblast and osteoblast (GFP+) fractions. Shown are representative dot plots showing the sorting strategy; data are gated on CD45− Ter119− stromal cells. (C) CXCL12 mRNA expression (relative to β-actin) in the GFP+ (osteoblast) cell fraction is shown. Data represent mean ± SEM; *P < .05.