Increased growth of myoblasts from hypertrophic muscles in syringomyelia.

Proliferation and differentiation of myoblasts from hypertrophic muscles were studied "in vitro" in two cases of syringomyelia with muscle hypertrophy (MH). Their myoblast growth was compared with that of muscle cells sampled on the contralateral side in the same patients and in control subjects. The effect of a circulating factor was tested using patient sera in place of fetal calf and horse sera. The results showed that MH cells were morphologically abnormal (giant and granular). MH myoblasts proliferated more rapidly than contralateral and normal myoblasts, their fusion was accelerated and the resulting myotubes synthesized higher levels of protein. MH sera increased these effects. Serum factors are therefore likely to be involved in "in vivo" muscle hypertrophy. These findings suggest that the pathogenesis of muscle hypertrophy in syringomyelia involves acquired abnormalities due to molecules released in response to neural lesions.