Growth and differentiation of myogenic clones from adult human muscle cell cultures.
Clonal cultures only recently have been applied to normal and pathological human muscle, but detailed clonal analysis and differentiative properties of individual long term muscle subclones derived from adult normal human muscle cell (HMC) cultures have not been reported. In this study we compared the growth potential by plating efficiency (PE), muscle colony differentiation (MC) and growth cuvers and the differentiative properties by fusion index, dystrophin localization, creatine kinase (CK) total activity and isozyme electrophoresis in HMC cultures derived myogenic subclones. These properties were tested in two experimental culture systems (200 cells/dish versus single cell/well) and with two tissue culture media (standard medium--MM--versus conditioned medium--CM). We found a significant high PE and MC in clonal cells established with single cell/well and grown in conditioned medium. In derived subclones we observed two classes of myogenic cells: one characterized by exponential growth kinetic, branched myotubes with high fusion index and predominantly sarcolemmal distribution of dystrophin and MM band at CK electrophoresis; the other with flat growth curve, low fusion index and low CK total activity. These findings demonstrate the variability of the expression of myogenic potentials in cells cloned from adult normal HMC cultures and represent an important tool for comparing the various cell types present in normal and diseased human muscle and for transplantation of normal myoblasts in Duchenne Muscular Dystrophy.