Figure 5

Immunohistochemical analysis of human myoblasts and cells after 6 days of differentiation. Homogeneous staining of cells with (A) antibody against three different sarcomeric TM isoforms and (B) a specific antibody against beta-tropomyosin, β-TM isoform. (C) Strong positive staining of multinucleated cells with an antibody against sarcomeric TM isoforms. (D) Staining of cells with specific antibody against beta-tropomyosin. (E) The mononucleated cells were negative for fast troponin T expression, while positive immunoreactivity was observed in (F) multinucleated cells, as illustrated by the anti-fast TNNT MAb staining. Homogeneous staining of (G) proliferating myoblasts and (H) multinucleated myotubes with antibody against slow isoform of troponin I. No expression of fast troponin I was detected in (I) proliferating myoblasts whereas positive staining was observed in (J) differentiated cells by an antibody against this isoform. Homogeneous immunoreactivity of both (K) proliferating myoblasts and (L) multinucleated cells with antibodies against cardiac isoform of troponin I. A subset of the multinucleated myotubes have a myofibre-like appearance with peripherally located nuclei (H and J; arrows). The bar represents 10 μm.