Validation of apoptosis in equine mesenchymal stem cells. Representative fluorescence images are shown for cells injected through a 21G needle, with (a) cell surface Annexin V (fluorescein isothiocyanate) and (b) nuclear propidium iodide staining of cells. (c) Merged Annexin V and propidium iodide images to distinguish coincidal and noncoincidal staining of cells. Cells in early apoptosis (green and green–red) and in late apoptosis (red) are present. Original magnification × 100, scale bar = 200 μm. (d) Quantification of apoptotic cells after treatment with known inducers of apoptosis. Cells injected through a 19G needle in D10 or in plasma are shown together with non-injected controls. D10, Dulbecco’s modified Eagle’s medium supplemented with 10% foetal bovine serum.