CXCR4 surface expression on bone marrow cell populations. Bone marrow cells were collected from mice by bone marrow flush for analysis of CXCR4 expression by flow cytometry. (A) Cells were stained with antibodies to detect mesenchymal progenitor cells (PαS; TER119⁻CD45⁻CD31⁻PDGFRα⁺SCA1⁺), hematopoietic progenitor cells (LSK; Lin⁻cKit⁺SCA1⁺), and BMECs (Lin⁻CD45⁻CD31⁺). Histograms of surface CXCR4 expression on cells (solid red areas) were determined by flow cytometry. Open dashed-line histograms represent FMO controls. CXCR4 positive percentage of cells within each population (B) and calculated mean fluorescence intensity for CXCR4 (C) (n = 4 mice per group). Data from 2 independent experiments are represented as mean ± SEM. MFI, mean fluorescence intensity.