Maturation of human skeletal muscle fibres in explant tissue culture

Human foetal skeletal muscle was grown in explant cultures and the development of myotubes was monitored morphologically and by the development of membrane potential and acetylcholine sensitivity. Migration of uninucleate cells from the explants occurred in the first day of culture and formation of multinucleated myotubes took place between 7 to 10 days. Early myotubes were variable in appearance, being either flat and nonrefractile or narrow and cylindrical. Some cross-striated cells were observed. Resting membrane potentials were around -25 mV and there was great variation in myotube sensitivity to acetylcholine. After about 6 weeks in culture most myotubes were of the refractile type. Many had hypolemmal nuclei and were cross-striated; some contracted spontaneously. All myotubes had developed high sensitivity to acetylcholine although there had been no increase in resting membrane potential.