Fig. 6.

Thrombopoietic activity of YRS^ACT is relevant in human cells. (A) Human CD34⁺ cells (from two donors) isolated from cryopreserved PBSCs were expanded and kept for 7 d in cultures supplemented with 200 nM YRS^ACT or PBS (CON), or with the supernatant of hPBMC cultures (from three donors) pretreated with YRS^ACT or PBS (CON) for 2 d. The number of MKs in cultures exposed to YRS^ACT directly (red boxes) or indirectly (blue boxes) was calculated as the percent of that in PBS-treated cultures. All hPBMC supernatants were tested in triplicate and the corresponding results were averaged for analysis. Data are shown as 25th to 75th percentile bars with median and min to max whiskers. **P < 0.01 calculated by two-tailed Mann–Whitney test. (B) CD34⁺ cells from normal human iPS sacs (sac-like structures that enclose hematopoietic progenitor cells) were cultured for 14 d and then differentiated for 9 d with added YRS^ACT (200 nM) or PBS (Left), or culture supernatant of hPBMCs exposed to YRS^ACT or PBS (Right). (C) Experiment as in B, except that CD34⁺ cells were isolated from iPS cells derived from a patient with CAMT. MK counts in C and D are shown as dot plots with mean ± SD of technical triplicates.