AZA treatment of healthy as well as MDS MSCs favors support of healthy HSPCs. (A) Experimental design. Healthy MSCs or MDS MSCs were treated once with 10 µM AZA for 48 hours. MSC layers were washed and healthy or MDS CD34⁺ HSPCs were added. After 4 days, CD34⁺ HSPCs were harvested and progenitor cell activity was assessed by short-term CFU assays. (B) Mean CFU frequencies ± SEM (n = 11 healthy CD34⁺ cells; n = 12 MDS CD34⁺ cells; n = 7 healthy MSCs layers). (C) Mean CFU frequencies ± SEM of n = 11 healthy CD34⁺ cells and n = 12 MDS CD34⁺ cells after culture on n = 7 healthy MSCs were compared with mean CFU frequencies ± SEM of n = 9 healthy CD34⁺ cells and n = 11 MDS CD34⁺ cells after culture on n = 6 MDS MSCs. (D) Mean CFU frequencies ± SEM (n = 9 healthy CD34⁺ cells /n = 6 MDS MSC layers; n = 11 MDS CD34⁺ cells /n = 6 MDS MSC layers). *P < .05; **P < .01; ***P < .001.