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Electric Stimulation Promotes Differentiation of Cultured Myoblasts. Y. Kawahara, C. Umeda1, T. Miyashita1, T. Kajiume1, H. Moriyama1, K. Kataoka2, L. Yuge1  (1Graduate School of Health Sciences, 2Graduate School of Biomedical Sciences, Hiroshima University, Japan)

   Muscle growth is facilitated by electric stimulation, and this has been clinically used for treatment of muscle atrophy in space flight.   However, the effect of electric stimulation has not been elucidated on differentiation of myoblasts.   A rat myoblast cell line, L6 (ATCC.CRL.1458) was used.   The cells were seeded in a culture dish (day 0) and cultured in a Dulbecco's MEM.   The culture dish became confluent on day 6.   We exposed the cells to the electric stimulation (group E) and compared with normal culture control (group C).   The condition of the square wave stimulation is 50 V, 2 msec, 30 pulses/min and 5 min/day, and we stimulated the cells on day 7, 9, 11 and 13 in group E.   The cells were cultured up to day 21.   We studied morphological characteristics of the cells and expression of myogenin, a myogenic regulatory factor, by RT-PCR (for mRNA) and western blot analysis (for protein).   The formation of myotubes was earlier and more frequently in group E, than in group C.   Myogenin was expressed earlier and continued longer in group E than group C.   Moreover, we succeeded in differentiation of striated muscle cells showing spontaneous contraction in group E.   The differentiation of myoblast was accelerated by the application of electric stimulation, and even striated muscle cells were obtained.   These results suggest the possibility that electric stimulation, effectively used in clinical therapy of muscle atrophy, facilitates not only the growth of existing muscle fibers but also the differentiation of myoblasts.