Mitochondrial myopathies: morphological and biochemical studies in human muscle cultures

The mitochondrial myopathies are a heterogeneous group of disorders presumed to be caused by primary mitochondrial dysfunction with impairment of energy provision from oxidative metabolism. An increasing number of specific functional mitochondrial deficiencies have been documented and recently new strategies are beginning to analyze molecular and genetic mechanisms. Nevertheless these specific disorders have not been studied extensively in human muscle cultures. The objectives of our study were to reproduce morphological and biochemical changes in cultured myotubes of three Kearns-Sayre syndrome (KSS) patients to evidentiate a different mitochondrial susceptibility to 2-4 dinitrophenol (DNP) into normal and KSS muscle cultures, and to investigate the protective effect of ubidecarenone (Q10) on KSS myotubes exposed to DNP. In KSS cultures as compared to normal ones no abnormalities in growth pattern and differentiation were observed. KSS myotubes DNP exposed showed some abnormally large mitochondria with parallel-packed cristae and decrement in all mitochondrial enzymes activity ranging from 20 to 40%. In normal myotubes DNP exposed and in patient cultures DNP-Q10 treated a normal mitochondrial morphology and a recovery of enzymatic activity was found. In Complex I deficiency patient cultured myotubes cytochemical, immunocytochemical, ultrastructural and biochemical studies were performed and no abnormalities were found. Negative tissue culture findings could be explained by the fact that the defect cannot be reproduced in aneural cultures, and that there could be a gradual selection of cells containing a preponderance of wild type mitochondria over those that contain mutant mitochondria.