Quantitative cellular level analysis of mitochondrial DNA 3243A > G mutations in individual tissues from the archival temporal bones of a MELAS patient.

Conclusion: We could represent the first quantitative analysis of the mutation rate at the cellular level in human inner ear of a patient with MELAS (mitochondrial encephalopathy, lactic acidosis and stroke-like episodes) by combining laser capture microdissection (LCM) and quantitative real time PCR.

Objectives: We previously reported combining LCM and PCR to isolate mtDNA from the cells of specific tissues within a human archival celloidin-embedded temporal bone section without known otological history. Using this method, we quantitatively analyzed the rate of mtDNA 3243A > G mutation in the inner ear of a MELAS patient, and examined the correlation of the mutation rate at the cellular level and their histopathological condition.

Methods: We extracted each inner ear organs using LCM from temporal bone sections of a MELAS patient, and studied the mutation rate, which was calculated as the ratio of the amount of mutant mtDNA to the total mtDNA.

Results: We found that the mtDNA mutation rate was high in spiral ganglion cells and the saccular macula, but was comparatively low in hair cells of the organ of Corti, the stria vascularis and the facial nerve. With the exception of the stria vascularis, there was a good correlation between the mutation rate and the histological findings.