Characterization of bone marrow-derived hMSCs, CD34⁺ cells, or non-hMSCs/CD34^- cells. (A) FACS profiles of hMSCs, CD34⁺ cells, or non-hMSCs/CD34^- cells stained with CD73 (PE-conjugated mAbs) and CD34 (FITC-conjugated mAbs). (B) Expression of surface antigens on hMSCs. (Left) The x-axis indicates CD45 expression labeled with FITC-conjugated mAbs; the y-axis indicates CD14 expression labeled with PE-conjugated mAbs. (Right) The x-axis indicates HLA class I expression labeled with PE-conjugated mAbs; the y-axis indicates CD105 expression labeled with FITC-conjugated mAbs. Numbers indicate the percentage of cells in each quadrant. (C) Expression of surface antigens on non-hMSCs/CD34^- cells. The x-axis indicates CD45 expression labeled with FITC-conjugated mAbs; the y-axis indicates CD14 expression labeled with PE-conjugated mAbs. Cells were gated based on forward and side light scatter to exclude debris. Positivity for a surface antigen was defined using the isotype control monoclonal antibody. (D) Immunophenotype of hMSCs. Cells were harvested at passage 5, labeled with the antibodies specific for the indicated human surface antigens or negative controls, and analyzed by flow cytometry. Bar indicates positive reactivity with the indicated antigens. (E) hMSCs at passage 5 are induced to differentiate into osteoblasts and stain positive for alkaline phosphatase. Under adipogenic conditions, hMSCs differentiate into adipocytes, which are positively stained by Oil-Red staining. Under chondrogenic conditions, hMSCs differentiate into chrondrocyte-like cells and stained positively by Alcian blue. Original magnification, × 100. The results shown are representative of 2 experiments that had similar results.