Exogenous addition of DPT enhances HSC clonogenicity in both stroma/serum-based and stroma/serum-free culture conditions without influencing cell-cycle progression. (A) Effect of exogenous addition of 1.67 μg/mL mouse recombinant DPT (mrp, n = 4 independent experiments, 166 trees) or human recombinant DPT (hrp, n = 4 independent experiments, 155 trees) on proliferation rates of founder HSCs cultured on 2018 stroma. (B) Similar analysis showing the effect of exogenous DPT addition on the HSC progeny for the first 3 generations. (C) Founder HSC proliferation rates in stroma/serum-free cultures supplemented with 100 ng/mL SCF, 100 ng/mL TPO without (n = 5 independent experiments, at least 30 trees per experiment, 153 trees total) or with 1.67 μg/mL mouse DPT (n = 5 independent experiments, at least 30 trees per experiment, 190 trees total). (D) HSC proliferation kinetics in stroma/serum-free conditions in the presence of 100 ng/mL SCF, 100 ng/mL TPO, and 1.67 μg/mL mDPT. Values indicate the time at which 50% of the cells have divided. Dividing cells from 3 independent experiments were pooled. exp, experiment.