Mitochondrial abnormalities in ageing macular photoreceptors

Purpose. To evaluate somatic mitochondrial (mt) DNA mutations in the macula during ageing. Methods. Ten 30-mum cryostat sections from the macula (foveal and perifovea l regions) and peripheral retina of 14 donors (aged 14-94 years) were cut f or cytochrome c oxidase cytochemistry. The photoreceptor layer was microdis sected and DNA extracted for 4977-bp mtDNA (mtDNA(4977)) quantification usi ng PCR. Dual cytochemistry for cytochrome c oxidase and succinate dehydroge nase allowed the detection of cytochrome c oxidase-deficient cones. Results. Findings showed a progressive accumulation of mtDNA(4977) from age s 14 to 94 years. From ages 14 to 60 years there was an increase from 0.006 % to 0.25%, and from ages 60 to 94 years there was a steeper increase from 0.25% to 5.39%, Counts of cones in the dual-reacted preparations showed mor e cytochrome c oxidase-deficient cones in the foveal region than elsewhere. C Conclusions. The results show that mitochondrial DNA deletions and cytochro me c oxidase-deficient cones accumulate in the ageing retina, particularly in the foveal region. These defects may contribute to the changes in macula r function observed in ageing and age-related maculopathy.