Increased collagen synthesis by Duchenne myogenic clones

Myogenic cell clones were grown in triplicates from 3 patients with Duchenne muscular dystrophy, 5 with late onset myotonic dystrophy, 2 with spinal muscular atrophy, 6 male children controls, 4 adult controls and 6 normal aborted fetuses (10-12 weeks old). The clones from patients with myotonic dystrophy and spinal muscular atrophy had normal collagen synthesis. The fetal clones showed 3.3-fold lower values than control clones for [3H] extracellular (medium) hydroxyproline, while intracellular [3H] hydroxyproline levels showed normal values. Analysis of [3H] proline incorporation demonstrated a 4-fold increase in [3H] hydroxyproline released into the medium of Duchenne myogenic cell clones while intracellular [3H] hydroxyproline levels showed normal values. The collagen turnover of Duchenne clones was normal. These results strongly suggest that the increased amount of collagen present in Duchenne dystrophic muscle is related to the primary defect of the disease and is not due to secondary replacement fibrosis.