Hematopoiesis - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 20

pluripotent SC

myeloid SC lymphoid SC

GMSC megacaryocytic SC erythrocytic SC

granulocytic SC monocytic SC

monocyte

basophil
eosinophil
neutrophil

macrophage

Fig. 2.1 Hematopoiesis with a focus on granulocytic and monocytic lineages (SC: stem cell,
GMSC: granulocyte-monophage stem cell). After birth, hematopoiesis occurs in the bone marrow.
Under the influence of stimulators, multipotent stem cells of the bone marrow differentiate
into progenitors (committed stem cells). The first differentiation leads to myeloid and lymphoid
stem cells. The progenitors undergo several divisions to give rise to stem cells with limited
differentiation potential, the specific progenitors and precursors of a single blood cell lineage.
Lymphoid stem cells (progenitors) produce B and T lymphocytes. Myeloid stem cells, or
colony-forming unit CFUgemm (granulocyte-erythroid-macrophage-megakaryocyte) give birth
to progenitors of many lineages (granulocytic, monocytic, erythrocytic, and megakaryocytic). Gen-
erator CFUgemm leads to more differentiated progenitors: (1) CFUgm (granulocyte-macrophage)
that give rise to CFUg (granulocyte) and CFUm (macrophage); (2) CFUeo (eosinophil); (3) CFUb
(basophil); (4) CFUe (erythroid); and (5) CFUmeg (megakaryocyte). Precursors have lost self-
renewal capacity. They include myeloblasts, monoblasts, lymphoblasts, proerythroblasts, and
megakaryoblasts. Several shared modifications characterize cell maturation: reduction in cell size
and nucleocytoplasmic ratio and chromatin condensation. Precursors lead to mature blood cells
after 3 to 5 divisions according to the cell lineage (one precursor can give birth to up to 32 daughter
cells). Mature blood cells enter blood. Lymphocytes and monocytes can differentiate in tissues after
their blood journey. Hematopoiesis is composed of several compartments: (1) multipotent stem
cells such as colony-forming unit-spleen ( CFUs ), (2) progenitors, (3) precursors, and (4) mature
cells (granulocytes, monoocytes, lymphocytes, erythrocytes, and thrombocytes).

The turnover of hematopoietic cells 1 is estimated to be about 10 12 cells per
day [ 39 ]. All blood cell types are produced in the bone marrow from pluripotent
stem cells (PSC; Fig. 2.1 ). Hematopoietic stem cells and derived progenitor cells
yield blood resupply during the entire life. Pluripotent stem cells give birth via

1

αιατικ π ι

o ς : associated with blood, o o: to do.