Both mtDNAΔ5kb (chimeric probe) (A, B) or wild-type mtDNA (wild type 1) (C, D) only show an increase in vulnerable neurons in AD. In the hippocampus, we found that, whereas pyramidal neurons (py) show mtDNA increase in AD (A, C) compared with controls (B, D), other neuronal populations, e.g., granule cells of the dentate gyrus (gr), as well as glia, show no detectable signals. Scale bar, 100 μm.