Distinct Stromal Cell Factor Combinations Can Separately Control Hematopoietic Stem Cell Survival, Proliferation and Self-Renewal. Mus musculus

Hematopoietic stem cells (HSCs) are identified by their ability to sustain prolonged blood cell production in vivo, although recent evidence suggests that durable self-renewal (DSR) is shared by HSC subtypes with distinct self-perpetuating differentiation programs. Net expansions of DSR-HSCs occur in vivo, but molecularly defined conditions that support similar responses in vitro are lacking. We hypothesized that this might require a combination of factors that differentially promote HSC viability, proliferation and self-renewal. We now demonstrate that HSC survival and maintenance of DSR potential is variably supported by different Steel factor (SF)-containing cocktails with similar HSC-mitogenic activities. In addition, stromal cells produce other factors, including nerve growth factor and collagen 1, that can antagonize the apoptosis of initially quiescent adult HSCs and, in combination with SF and interleukin-11, produce >15-fold net expansions of DSR-HSCs ex vivo within 7 days. These findings suggest a new molecular basis for HSC control and expansion. Overall design: Adult mouse bone marrow CD45+EPCR+CD48-CD150+ cells were used in a total of 4 conditions (fresh, 6 hour stimulation with SF+IL-11+UG26 CM, UG26 CM only, SF+IL-11) with 2 technical replicates per condition.