Morphological differentiation of human muscle cocultured with mouse spinal cord

Human muscle fibres have been cocultured with sections of embryonic mouse spinal cord for periods of up to 2 months. The muscle fibres regenerated to form a bundle of myotubes, a proportion of which developed cross-striations and contractions. This proportion was variable between biopsies, and morphological differentiation was not as successful as when mouse muscle and mouse nerve were cultured together. Regeneration and morphological differentiation were unaffected by storing samples in liquid nitrogen, and were not improved by the presence of original synaptic areas in the explanted bundle or by alterations in the growth media. These involved changing the levels of serum and embryo extract, using different sources of serum, and the incorporation of additives in the medium. A comparison of the growth characteristics of samples of muscle from 30 patients (including some control samples) indicated that although muscle from younger patients (less than 14 years) regenerated more quickly, the myotubes did not have better differentiation. It also indicated that the growth characteristics of regenerated myotubes from diseased and normal muscle were indistinguishable within the 4-8 weeks observation period. Muscle from patients with Duchenne muscular dystrophy regenerated and differentiated less well than would be expected from age-matched controls, but this was not thought to reflect an intrinsic abnormality in the regenerative capacity of the muscle.