Jana Naue, Steffen Hörer, Timo Sänger et al.
The authors measured heteroplasmy levels across 100 individuals taken during autopsy. They examined a number of tissues: blood (control), buccal cells, liver, brain, muscle, heart, lung, bone and hair, with 883 samples in total across a range of ages. They find that muscle and liver cells are the most susceptible tissues to developing mtDNA mutations (79% and 69% of individuals respectively), with only 12 individuals displaying no mutations whatsoever in the measured tissues. Bone (19.8%), blood (18%), lung (17%) and buccal cells (16.2%) showed the fewest number of individuals with mtDNA mutations. They find a strong correlation between the mean number of heteroplasmies in muscle and age (r=0.746).