Correlation of Cochlear Blood Supply with Mitochondrial DNA Common Deletion in Presbyacusis

Abstract

Objectives To study the relationships between cochlear hypoxia, mitochondrial (mt) DNA⁴⁹⁷⁷ deletion and metabolic features of mtDNA in presbyacusis.

Material and Methods Sixty-seven temporal bones from a presbyacusis group, an age-matched control group and a young and middle-aged control group were involved in the experiment. Nested and tri-nested polymerase chain reactions (PCRs) were applied to test for the presence of the mtDNA⁴⁹⁷⁷ deletion. Computer imaging processing was used to measure blood vessel parameters in the internal acoustic meatus (IAM).

Results The mtDNA⁴⁹⁷⁷ deletion was detected in 17/34 ears in the presbyacusis group, 4/19 ears in the age-matched control group and 0/14 ears in the young and middle-aged control group. In the presbyacusis group, the lumen of the vasa nervorum of the IAM showed a more severe narrowing in cases with than without the mtDNA⁴⁹⁷⁷ deletion.

Conclusions The high incidence of the mtDNA⁴⁹⁷⁷ deletion in the temporal bones of presbyacusis patients suggests a correlation between the mtDNA⁴⁹⁷⁷ deletion and presbyacusis. Hypoxia of the cochlea may cause the mtDNA⁴⁹⁷⁷ deletion and other mtDNA mutants and furthermore may cause a reduction in mitochondrial oxidative phosphorylation and decreased function of the acoustic neural system. The symptoms of presbyacusis may occur when the function of the acoustic neural system is impaired as a result of abnormal mtDNA metabolism reaching a particular threshold.

• hearing loss
• hypoxia
• mitochondrial DNA
• mutant aging