Figure 1.

Transfer of mitochondria between chondrocytes (CH) and mesenchymal stromal cells (MSCs). (A) Stained mitochondria (MitoTracker, in red) are transferred from a donating MSC to a receiving CH stained with CellTrace (in blue). SiR-Actin stains F-actin in all cells (in green) and was used to visualize cell dimensions. Scale bar = 50 µm. (B) Quantification of transfer of mitochondria from donor to receiving cell, measured with flow cytometry. Mitochondrial transfer between all cell combinations (CH → CH, CH → MSC, and MSC → CH) occurred predominantly in the first 4 to 8 hours after initiation of the coculture. In all cases, 20,000 events were recorded. MTR = MitoTracker.