Fig. 1

a, b Mitochondrial transfer from MSCs to fibroblast cell lines. a Representative fluorescence images showing mitochondrial transfer and TNT formation. Mitochondria of stem cells are labelled with Cox8a GFP (green fluorescent protein), mitochondria of human fibroblasts are labelled with Cox8a RFP (red fluorescent protein) and nuclei of murine fibroblasts are labelled with LMNB BFP (blue fluorescent protein). Co-cultures were fixed and stained with phalloidin. b Confocal images of mitochondrial transfer derived from MSCs. Fibroblast mitochondria are labelled with Cox8a RFP and stem cell mitochondria are labelled with Cox8a GFP. c, d Representative fluorescence images of cell fusion between stem cell and fibroblast. c Mitochondria are labelled with Cox8a GFP (stem cell) and Cox8a RFP (fibroblast). Cells with a complete co-localization of red and green fluorescence indicate the rare event of nuclear fusion (yellow cells). d Stem cells have Cox8a GFP-labelled mitochondria and LMNB BFP-labelled nuclei. Fibroblasts have LMNB RFP-labelled nuclei. Cells with a co-localization of LMNB BFP and LMNB RFP have fused nuclei. Scale bars represent 10 μm. Images were contrast optimized (Colour figure online). Cox8a Cytochrome c oxidase subunit 8A, LMNB Lamin B1