Correlation of cochlear blood supply with mitochondrial DNA common deletion in presbyacusis.
OBJECTIVE
To study the relationships between cochlear hypoxia, mitochondrial (mt) DNA4977 deletion and metabolic features of mtDNA in presbyacusis.


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.
Dai
Pu
P
Department of Otolaryngology-Head and Neck Surgery, Chinese PLA General Hospital, Beijing, People's Republic of China.
Yang
Weiyan
W
Jiang
Sichang
S
Gu
Rui
R
Yuan
Huijun
H
Han
Dongyi
D
Guo
Weiwei
W
Cao
Juyang
J
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics / Q000473:pathology; D001301:Audiometry, Pure-Tone; D016022:Case-Control Studies; D003051:Cochlea / Q000098:blood supply*; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D006801:Humans; D007511:Ischemia / Q000150:complications*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011304:Presbycusis / Q000209:etiology* / Q000235:genetics / Q000378:metabolism
D004272:DNA, Mitochondrial