Genome-wide expression analysis of self renewing hematopoietic stem cells (HSC) in control and CD70TG mice.. Mus musculus

To study the effect of CD27 triggering on HSC biology Ageing of the hematopoietic stem cell (HSC) compartment is characterized by an accumulation of less productive HSCs with impaired lymphoid differentiation capacity, which contributes to age-dependent hematological abnormalities including anemia, myeloproliferative disorders and a decline in adaptive immunity. Since HSCs express the costimulatory receptor CD27 and because inflammation has been associated with HSC ageing, we investigated the effect of stimulation of CD27 by its inflammatory ligand CD70 on HSC maintenance. We found that CD27-triggering during CD70-driven immune activation in young mice enhances HSC self-renewal, leading to accumulation of HSCs to levels comparable with old control mice. These findings indicate that CD27-signaling accelerates HSC ageing, which is supported by the observation that CD27-triggering negatively affects HSC differentiation to the lymphoid lineage and increases myeloid differentiation. This functional change was mirrored by a corresponding difference in gene expression, as microarray analysis indicated that CD27-triggered HSCs have a strongly myeloid-biased gene signature. CD27 signaling also induced enrichment of genes associated with biological processes involved in cellular responses to DNA damage/repair and reactive oxygen species (ROS), which are associated with HSC ageing and related to increased proliferation. Therefore, we postulate that CD27 triggering during chronic inflammation contributes directly to ageing of the hematopoietic compartment. Overall design: FACS sorted fractions of long term (CD34-) and short-term (CD34+) HCS from control (IFNgamma-/-) and CD70TG (IFNgamma-/-xCD70TG) mice. RNA from two mice was pooled on each microarray and 4 independent replicates were used per condition.