Spalax fibroblast-conditioned medium compromises cell cycle, causes nuclear and mitochondrial fragmentation in Hep3B cells. Hep3B cells were grown on cover slips under medium conditioned by Spalax or rat fibroblasts for seven days. Representative phase-contrast images demonstrating morphological changes (×200) are depicted. Cells were harvested and stained with PI, and cell cycles were analyzed by flow cytometry. Representative flow cytometry histograms of three independent experiments performed in duplicate are presented. Hep3B cells were stained with MitoTracker®Red, fixed with formaldehyde and counterstained with DAPI. Representative fluorescence microscopy images demonstrating nuclear and mitochondrial changes are present. White arrows point fragmented nuclei; empty arrows point chromatin condensation. Scale bars represent 10 μm. PI, Propidium iodide.