Characterization of bone marrow stromal cells. (a) Representative results of phenotypic characterization of good manufacturing practice-grade bone marrow stromal cells (BMSCs) by flow cytometry. More than 90% of BMSCs express CD73, CD90, CD105 and HLA A-B-C, and <5% of cells had surface antigen expression for CD3, CD34, CD45 and HLA DP, DQ, DR. (b) Tri-lineage differentiation capacity was confirmed. Adipogenic (Oil Red O/hematoxylin staining), chondrogenic (Alcian blue staining) and osteogenic differentiation (Alizarin red staining) could be induced, whereas no differentiation could be observed in controls without induced of differentiation. Black scale bars: 250 μm for adipogenic, 500 μm for osteogenic differentiation, and 1,000 μm for chondrogenic.