Mitochondrial DNA deletions are associated with ischemia and aging in Balb/c mouse brain

Deletions in the mitochondrial DNA (mtDNA) of Balb/c mouse cerebrums, resembling deletions found in elderly humans or in patients with certain disorders, were detected by PCR. Analysis was carried out on mice of various ages and on mice in which the bilateral common carotid arteries had been incompletely ligated to reconstruct cerebral ischemia. A 3,867 bp mtDNA deletion was present only in old or ischemic mouse groups. Among the non-ischemic groups, it was found in 0 of 12 weaning, 0 of 12 young, and four of eight old mice. Among the ischemic groups, it was found in 12 of 17 young and 11 of 11 old mice. Moreover, the percentage of total mtDNA containing deletions was 22% for the old non-ischemic group, 37% for the young ischemic group, and 69% for the old ischemic group. In addition, PCR analysis detected two other deletions of 3,726 bp and 4,236 bp in 4 of the 11 old ischemic cerebrums. The results indicate that mtDNA deletions are associated with aging, that ischemia increases the incidence of mtDNA deletions, and that mtDNA deletions resulting from ischemia are more likely to occur in old mice than in young mice.