Mitochondrial dysfunction and apoptosis in myopathic mice with collagen VI deficiency.
Collagen VI is an extracellular matrix protein that forms a microfilamentous network in skeletal muscles and other organs. Inherited mutations in genes encoding collagen VI in humans cause two muscle diseases, Bethlem myopathy and Ullrich congenital muscular dystrophy. We previously generated collagen VI-deficient (Col6a1-/-) mice and showed that they have a muscle phenotype that strongly resembles Bethlem myopathy. The pathophysiological defects and mechanisms leading to the myopathic disorder were not known. Here we show that Col6a1-/- muscles have a loss of contractile strength associated with ultrastructural alterations of sarcoplasmic reticulum (SR) and mitochondria and spontaneous apoptosis. We found a latent mitochondrial dysfunction in myofibers of Col6a1-/- mice on incubation with the selective F1F(O)-ATPase inhibitor oligomycin, which caused mitochondrial depolarization, Ca2+ deregulation and increased apoptosis. These defects were reversible, as they could be normalized by plating Col6a1-/- myofibers on collagen VI or by addition of cyclosporin A (CsA), the inhibitor of mitochondrial permeability transition pore (PTP). Treatment of Col6a1-/- mice with CsA rescued the muscle ultrastructural defects and markedly decreased the number of apoptotic nuclei in vivo. These findings indicate that collagen VI myopathies have an unexpected mitochondrial pathogenesis that could be exploited for therapeutic intervention.
Irwin
William A
WA
Department of Histology, University of Padova, 35121 Padova, Italy.
Bergamin
Natascha
N
Sabatelli
Patrizia
P
Reggiani
Carlo
C
Megighian
Aram
A
Merlini
Luciano
L
Braghetta
Paola
P
Columbaro
Marta
M
Volpin
Dino
D
Bressan
Giorgio M
GM
Bernardi
Paolo
P
Bonaldo
Paolo
P
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D024142:Collagen Type VI / Q000172:deficiency*; D016572:Cyclosporine / Q000494:pharmacology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006720:Homozygote; D007166:Immunosuppressive Agents / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000473:pathology*; D028361:Mitochondrial Diseases / Q000473:pathology*; D018482:Muscle, Skeletal / Q000187:drug effects; D009135:Muscular Diseases / Q000473:pathology*; D009840:Oligomycins / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure
D024142:Collagen Type VI; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D009840:Oligomycins; D016572:Cyclosporine; D002118:Calcium