Phenotypic analysis of bone marrow mesenchymal stem cells. (A) Primary rat bone marrow MSCs attached to the surface of the flask exhibiting elongation (arrow). (B) Homogenous rat BM MSCs at passage 4 displaying a fibroblast-like appearance and spindle-like arrangement. (C-D) Immunofluorescence of BM MSCs showing a strong expression of CD90 (C) and CD44 (D). (E) BM MSCs showing weak expression of nestin. (F) Immunophenotypes of BM MSCs analysed by flow cytometry. Images were viewed at 400× magnification using an inverted microscope and a fluorescence microscope equipped with a pseudo-fluorescence filter.