Clinical Study On Mitochondrial DNA4977Mutation In Presbycusis

OBJECTIVE: This study was to investigate the relationship between mitochondrial DNA 4977 bp deletion(mtDNA4977bp)mutation in hair shaft and hearing loss in individuals with presbycusis and to clarify the relationship between obtaining mitochondrial DNA damage of hair shaft in presbycusis.Methods:Case selection: From February 31,2018 to January 1,2019,in Otorhinolaryngology ward of Zhejiang Provincial Hospital of TCM to Zhejiang Chinese Medical University.We collected 3-5 hairs shaft from each of the 39 experimental groups(presbycusis group)and 20 control groups(normal hearing group)through questionnaires and rigorous hearing programs(pure tone audiometry,PTA and tympanogram).Inclusion criteria:Patients with symmetric,bilateral,sensorineural hearing loss;the pure tone average threshold sincreased by 26 dB or more of each;The frequency of the patient at the same frequencies differerence wthin 10 dB.The inclusion criteria of the control group: the pure tone hearing threshold test chart with each frequency is within the normal range(Control subjects had normal ear examinations and PTA frequencies of 25 dB);No history of taking ototoxic drugs;All participants signed informed consent letters.2.Extraction of mitochondrial DNA from hair shaft: we collected 3-5 hair shaft of each subject included in the study and used chelex-100 method to extract mitochondrial DNA in hair shaft.Ordinary PCR validated mitochondrial DNA of hair shaft was successfully extracted.Nested PCR identified the state of mitochondrial DNA 4977 bp deletion.3.DNA sequencing: Nested PCR amplified mitochondrial DNA fragments were sequenced using a sequencer to verify that the deleted fragment was a mitochondrial DNA 4977 fragment.Result: 1.Ordinary PCR results showed that all samples were extracted 135-bp mitochondrial DNA.Nested PCR amplified a 396 bp target fragment in a 4977 bp deletion-positive sample of mitochondrial DNA.The detection rate of mitochondrial DNA 4977 bp deletion was 10/39 cases(25.64%)in the presbycusis group,and in the normal hearing,3/20 cases(15.00%)werefound to have themitochondrial DNA 4977 bp deletion useing nested PCR.The comparison between the two groups was statistically analyzed by chi-square and found to be P=0.258(P>0.05),which was not statistically significant.2.The nested PCR amplified mitochondrial DNA fragment was sequenced using a sequencer,showing that the deletion fragment was a mitochondrial DNA 4977 fragment.Conclusion: 1.In presbycusis experimental group and the hearing normal old control group,the mitochondrial DNA4977 bp deletion are present from hair shaft.2.The total detection rate of mitochondrial DNA 4977 bp in presbycusis experimental group was higher than that in the hearing normal control group.