Fig 1: Immunocytochemistry for the detection of myogenic markers. The expression of muscle-related proteins in the tonsil-derived mesenchymal stem cells (T-MSCs) during the process of myogenic induction (T-MSCs; T-MSC-derived myoblasts; T-MSC-derived myocytes) was evaluated by immunostaining using antibodies against myogenic satellite cells (panel a, CD34; red), precursors [panel b, paired box 7 (Pax7); green], differentiated myogenic cells [panel c, desmin (red); panel d, dystrophin (green); panel e, myosin heavy chain (MHC; red)], skeletal myogenic cells [panel f, a-actinin (green); panel g, troponin I type 1 (TNNI1; green); panel h, myogenin (red)]. The cells were counterstained with DAPI (blue). The samples were analyzed under a fluorescence microscope using appropriate filters. (A) Undifferentiated T-MSCs expressed (panel a) CD34 and (panel b) Pax7, but no other markers of myogenic cells. (B) Following differentiation into myoblasts, 80–90% of cells expressed (panel c) desmin, (panel d) dystrophin, and (panel e) MHC and 20–50% of cells expressed skeletal muscle (SKM) markers including (panel f) a-actinin, (panel g) TNNI1, and (panel h) myogenin. (Panel a) CD34 and (panel b) Pax7 were not expressed at any stage of the differentiation process from T-MSC-derived myoblasts into T-MSC-derived myocytes. (C) T-MSC-derived myocytes exhibited an increased expression of (panels c to h) myogenic and SKM cell markers compared with T-MSC-derived myoblasts and formed multinucleated myotubes. FITC, fluorescein isothiocyanate; TRITC, tetramethylrhodamine isothiocyanate. Original magnification, ×200.