I am trying to label mitochondria in human dermal fibroblasts to assess mitochondrial transfer via tunnelling nanotubes to osteosarcoma cells. I am using a direct coculture approach whereby seed fibroblasts first and then 24 hours after seed osteosarcoma cells and perform time-lapse imaging on a confocal microscope for another 24 hours. I am using a direct coculture approach whereby seed fibroblasts first and then 24 hours after seeding osteosarcoma cells and performing time-lapse imaging on a confocal microscope for another 24 hours.
No matter how many times I wash my fibroblasts (that had been labelled with MitoRed), I can see the osteosarcoma cells pick up the label uniformly after a 10 minute period of coculture. I have tried washing my MitoRed overnight, labelling and washing MitoRed while cells are adherent to the substrate and I have tried labelling and washing MitoRed labelling cells in suspension (up to 7 washers in HBSS). I have even tried using MitoRed in various concentrations from 1:10,000 - manufacturers recommendation, down to 1:200,00. Even at the lowest concentration, there seems to be residual dye that the osteosarcoma cells pick up and coculture. As a result - it is almost impossible for me to determine whether fibroblasts have transferred some of their mitochondria into osteosarcoma cells.
Are there any ideas or approaches I could try that will allow me to assess the extent of mitochondrial transfer from one cell type to another? Many thanks in advance