A-D. Effects of BM MNC co-cultivation on hippocampal cell death after oxygen glucose deprivation (OGD). A and B show representative illustrations of rat hippocampal slices (left column: light microscopic micrographs; right column: red Propidium iodide (PI) fluorescence). Compared to untreated control slices, the reduction of oxygen and glucose supply caused a significant increase of cell death (indicated by increased PI incorporation) at 24 h and 48 h (C and D: #p < 0.001 by ANOVA). Thereby, PI positive cells occurred primarily within the cornu ammonis of the hippocampus (A and B). The co-cultivation with BM MNCs derived from young donors effected a significant reduction of PI-positive death cells at both investigation time points (*p < 0.001 by ANOVA). The addition of old BM MNCs did not significantly affect the number of PI-positive cells. Values are means ± SD for 10 samples per group. Scale bar: 2 mm.