Figure 1: Characterization of MSC.
A. Expression of cells surface proteins on human MSC was investigated by flow cytometry [7]. Expression of CD34, the marker for hematopoietic stem and progenitor cells, CD14, the co-receptor for LPS on macrophages, CD45, the common leucocyte antigen, and CD11b, the complement receptor 3 (= Mac-1, ITGAM) were not detected or showed very low expression on MSC in vitro. MSC expressed the typical antigens including TGF-ß receptor CD105 (endoglin), CD73 (5’ecto-nuclease), CD90 (GPI-anchored glycoprotein, = Thy- 1), and CD146 (adhesion molecule, = MUC18, MCAM).
B. The tri-lineage differentiation of MSC was investigated after 4 weeks of differentiation in vitro. Chondrogenesis was induced in micromasses and differentiation was documented by Alcian Blue staining (upper right). Adipogenesis (lower left) and osteogenesis (lower right) were induced in monolayer cultures and success of differentiation was investigated by Oil Red O and von Kossa staining, respectively. MSC in expansion medium maintained their fibroblastoid appearance and served as controls (upper left). Size bars measure 200 µm.