Figure 2.

Uptake and endocytic transport of extracellular mitochondria in cardiomyocytes. (a) iPS-CMs were exposed to gold-labelled HCF mitochondria for 2.5, 5, and 10 min and imaged by TEM. Labelled mitochondria had electron dense deposits and were apparent at all three study times outside cells, adjacent to the apical cell surface, undergoing endocytosis, and inside cells (left to right and indicated by arrows). Images are representative of four experiments at 5 min. Scale bars, 0.5 µm. (b) Four color 3-D SR-SIM of colocalisation of exogenous mitochondria (green) with early endosomes (red) at 4 h. Nuclei were stained with DAPI (blue) and both endogenous and exogenous mitochondria were detected with the MTC02 antibody (white). The combined image (left) and each color (right) are shown. Scale bars, 10 µm. (c) Colocalisation of HCF mitochondria (green) with late endosomes (red) at 1 h. Scale bars, 10 µm. (d) Colocalisation of mitochondria (green) with lysosomes (red) at 4 h. Scale bars, 10 µm. In (c,d) arrows indicate examples of exogenous mitochondria associated with each compartment, which also reacted with the anti-mitochondria MTC02 antibody. Nuclei were stained with DAPI (blue) and images represent twelve separate volumes analysed at each time (0.5, 1, 2, and 4 h).