Mitochondrial respiratory chain defects have been associated with various diseases and normal aging, particularly in tissues with high energy demands including skeletal muscle. Musclespecific mitochondrial DNA (mtDNA) mutations have also been reported to accumulate with aging. Our understanding of the molecular processes mediating altered mitochondrial gene expression to dysfunction associated with mtDNA mutations in muscle would be greatly enhanced by our ability to transfer muscle mtDNA to established cell lines. Here, we report the successful generation of mouse cybrids carrying skeletal muscle mtDNA. Using this novel approach, we performed bioenergetic analysis of cells bearing mtDNA derived from young and old mouse skeletal muscles. A significant decrease in oxidative phosphorylation coupling and regulation capacity has been observed with cybrids carrying mtDNA from skeletal muscle of old mice. Our results also revealed decrease growth capacity and cell viability associated with the mtDNA derived from muscle of old mice. These findings indicate that a decline in mitochondrial function associated with compromised mtDNA quality during aging leads to a decrease in both the capacity and regulation of oxidative phosphorylation.
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