Comparable frequencies but lower ROS levels in BM ECs from young donors
To clarify whether BM EC frequencies differ in young, middle-aged and old individuals, we measured BM ECs (CD34+CD309+CD133+) by flow cytometry. Fig. 1 shows the gating strategy of BM ECs and the percentages as well as intracellular ROS levels of BM ECs among the three age groups. The percentages of primary BM ECs were comparable in the three groups (Fig. 1B, 0.12% ± 0.01% vs. 0.11% ± 0.01%, P = 0.98; 0.12% ± 0.01% vs. 0.11% ± 0.009%, P = 0.74), whereas the ROS levels in BM ECs from young donors were significantly lower than those from middle-aged donors (Fig. 1C, 1661 ± 259 vs. 2462 ± 253,P =0.02) and old donors (Fig. 1C, 1661 ± 259 vs. 2715 ± 315,P =0.005).