Figure 1.Self-renewal and differentiation in hematopoiesis.
Hematopoietic
differentiation is a multi-step process. A small group of long term
repopulating hematopoietic stem cells (LT-HSC) replicates very slowly. The
down-stream compartments are more and more committed to a specific linage
and replicate at faster rates. Some of the progeny have to self-renew to
keep the pool of hematopoietic stem and progenitor cells. Our model is
based on the hypothesis this percentage of self-renewal versus
differentiation is regulated by a feedback mechanism that is related to the
number of mature cells in the blood (A). There is evidence, that the
dual function of self-renewal and differentiation is regulated by
asymmetric cell divisions where one daughter cell retains the stem cell
function whereas the other differentiating cell becomes a faster
proliferating precursor cell. Alternatively, cells can undergo symmetric
cell divisions to produce either two identical, self-renewing cells or two
differentiated daughter cells (B).
