BM-MSCs, but not WAT-, UC-, or skin-derived MSCs form bone, cartilage, and marrow tissue in vivo. (A) Phase-contrast images depicting spindle-shaped morphology of BM-MSCs and WAT-, UC-, and skin-derived MSCs. (B) Flow cytometric profiles of the same respective cell populations as in panel A. Histograms show fluorescent cell surface staining intensity of anti-CD90, anti-CD73, anti-CD105, anti-CD45, anti-HLA-DR, anti-CD14, anti-CD19, and anti-CD34 monoclonal antibodies conjugated to fluorophores (gray shading) and corresponding isotype control (no shading). (C) Trilineage in vitro differentiation of BM-MSCs and WAT-, UC-, and skin-derived MSCs (shown left to right). MSCs were induced to differentiate along osteogenic, adipogenic, and chondrogenic lineage in vitro according to standard protocols. After 21 days of osteogenic induction, cells were stained with alizarin red for visualization of Ca²⁺ accumulation (upper left image for each). Adipogenic differentiation capacity was visualized after 14 days of induction by staining lipid droplets with fluorescent nile red (upper right image for each). A 3-dimensional chondrogenic differentiation assay in Transwell plates was used for evaluation of chondrogenic differentiation potential. Tissue was fixed and further processed for histologic evaluation of chondrotypic glucosaminoglycans with toluidine blue after 28 days of induction. (D) BM-MSCs form bone, cartilage, and marrow tissue in vivo. Upper image shows schematic of the in vivo protocol. After expansion in pHPL-supplemented α-modified minimum essential medium (α-MEM), 2 × 10⁶ MSCs were resuspended in matrigel and subcutaneously injected into NSG mice. Spontaneous in vivo tissue formation was evaluated 8 to 12 weeks postimplantation by histology. Representative photomicrographs of hematoxylin and eosin ([H&E], upper row) and pentachrome-stained sections (lower row) are shown. Inserts show low-magnification overview photographs. ECM, extracellular matrix.