Abnormality of cultured muscle and Schwann's cells in familial lipid neuromyopathy. Muscle corrected by neural influence

V. Askanas, W. K. Engel, H. H. Kwan and J. V. Lawrence

Muscle and Schwann's cell cultures were established from a family (mother and two sons) with non-carnitine deficient neuromyopathy. Electron microscopy of noninnervated cultured muscle showed poorly matured muscle fibers containing large "mushy" mitochondria, lipid droplets, abundant multilaminated inclusions, and dense-core dark osmiophilic bodies. Parallel innervated muscle fibers (cocultured with normal-rat motor neurons for two to three weeks) were well cross-striated, had well-developed T tubules and sarcoplasmic reticulum, and none of the abnormalities of aneural muscle cultures. Cultured Schwann's cells were normal by light microscopy, but had ultrastructurally abnormal mitochondria, lipid droplets, dark osmiophilic granular inclusions, and numerous "foamy" vacuoles. Those studies demonstrated (1) intrinsic muscle and Schwann's cell defects because of reproduction of abnormalities in culture, (2) normal muscle cell responsiveness to innervation reflected by development of contractions and longer survival in culture, and (3) beneficial influence of a neural factor(s) on the endogenous muscle cell abnormality.