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Updated: Jul 31, 2026

Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction
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Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction

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Age-related extensive fragmentation of mitochondrial DNA into minicircles

M Hayakawa1, K Katsumata, M Yoneda

  • 1Department of Biomedical Chemistry, Faculty of Medicine, University of Nagoya, Japan.

Biochemical and Biophysical Research Communications
|September 13, 1996
PubMed

Insights

Aging human hearts show fragmented mitochondrial DNA (mtDNA) with over 350 types of deletions. This fragmentation, linked to oxidative stress, supports the redox mechanism of aging.

Area of Science:

  • Mitochondrial biology
  • Aging research
  • Molecular genetics

Background:

  • Mitochondrial DNA (mtDNA) fragmentation is a hallmark of aging.
  • Previous studies have identified various mtDNA deletions, but a comprehensive analysis in aging human hearts was lacking.

Purpose of the Study:

  • To investigate the types and accumulation of deleted mtDNA (delta mtDNA) in normal human hearts with age.
  • To explore the underlying mechanisms of mtDNA fragmentation and its relationship with oxidative stress and aging.

Main Methods:

  • Utilized a novel total-detection system to identify and quantify various-sized delta mtDNA fragments.
  • Analyzed the correlation between wild-type mtDNA levels, delta mtDNA types, and oxidative damage markers (8-hydroxydeoxyguanosine).

Main Results:

  • Documented up to 358 types of age-related delta mtDNA in human hearts.
  • Observed accumulation of minicircles (delta mtDNA lacking replication origins), suggesting novel replication mechanisms.
  • Found a linear decrease in wild-type mtDNA with age, negatively correlated with delta mtDNA and oxidative damage.
  • Identified a mirror image in delta mtDNA size distribution, supporting double-strand break and rejoining via hydroxyl-radical attack.

Conclusions:

  • Age-related mtDNA fragmentation is extensive in human hearts.
  • Oxidative stress is a primary driver of mtDNA fragmentation, supporting the 'redox mechanism of aging'.

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