Modulation of mitochondrial morphology by bioenergetics defects in primary human fibroblasts

Mitochondria are dynamic organelles with continuous fusion and fission, the equilibrium of which results in mitochondrial morphology. Evidence points to there being an intricate relationship between mitochondrial dynamics and oxidative phosphorylation. We investigated the bioenergetics modulation of mitochondrial morphology in five control cultured primary skin fibroblasts and seven with genetic alterations of oxidative phosphorylation. Under basal conditions, control fibroblasts had essentially filamentous mitochondria. Oxidative phosphorylation inhibition with drugs targeting complex I, III, IV or V induced partial but significant mitochondrial fragmentation, whereas dissipation of mitochondrial membrane potential (DΨm) provoked complete fragmentation, and glycolysis inhibition had no effect. Oxidative phosphorylation defective fibroblasts had essentially normal filamentous mitochondria under basal conditions, although when challenged some of them presented with mild alteration of fission or fusion efficacy. Severely defective cells disclosed complete mitochondrial fragmentation under glycolysis inhibition. In conclusion, mitochondrial morphology is modulated by DΨm but loosely linked to mitochondrial oxidative phosphorylation. Its alteration by glycolysis inhibition points to a severe oxidative phosphorylation defect.