Hematopoiesis - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 47

(CSF3R) signaling by recruiting ubiquitin ligase, thus controlling pathway from
early to late endosomes and lysosomes [ 88 ].
Stimulated by macrophage colony-stimulating factor (mCSF or CSF1),
granulocyte-macrophage progenitor cells differentiate into monocytes. This factor
also enhances cytokine production (gCSF, IL6, and IL8) and other functions in
monocytes and macrophages. Macrophage colony-stimulating factor is synthesized
by fibroblasts, bone marrow stromal cells, endothelial cells, astrocytes, osteoblasts,
keratinocytes, activated B and T cells, and LPS-activated macrophages. Its receptor
on monocytes, macrophages, and their progenitors triggers the Ras-Raf1-ERK
cascade.

2.4.2.5 Stem Cell Factor

Stem cell factor (SCF) is produced by bone marrow endothelial cells, fibroblasts,
and other cells. It acts in synergy with Epo, Tpo, IL3, gmCSF, and gCSF on
BFUe, CFUgm, and CFUgemm, and possibly preCFUc (precolony-forming unit in
culture, i.e., granulocyte precursors), as well as on megakaryocytic progenitors [ 85 ].
Stem cell factor enhances IL7-induced proliferation of preB cells and stimulates
T-lymphocyte development and maturation. With IL2, SCF promotes differentiation
of CD34

hematopoietic cells into NK cells.
Stem cell factor triggers with costimulators proliferation of hematopoietic stem
cells. Many hematopoietic cell growth factors (e.g., SCF, IL3, and gmCSF), as well
as other growth factors (fibroblast [FGF1 and FGF2], hepatocyte [HGF], vascular
endothelial [VEGF], heparin-binding epidermal [HBEGF], platelet-derived [PDGF]
growth factor, transforming growth factor-

+

β ) and cytokines (e.g., interleukins IL1,

IL2, IL4, IL6-IL8, and interferon- ), can associate with heparin and heparan sulfate

proteoglycans of bone marrow stroma [ 89 ].

γ

2.4.2.6 Pleiotrophin

Pleiotrophin, a neurite outgrowth factor 48 promotes expansion of the population of
bone marrow hematopoietic stem and progenitor cells in vivo [ 90 ]. In addition to its
effects as a mitogen factor for neurons and angiogenic agent, this heparin-binding,
regenerative growth factor for hematopoietic stem cells, activates phosphoinositide
3-kinase.

2.4.2.7 Insulin-like Growth Factor-1

Insulin-like growth factor-1 induces erythroid colony formation.

48 A.k.a. heparin-binding brain mitogen (HBBM), heparin-binding growth factor HBGF8, neurite
growth-promoting factor NEGF1, heparin affinity regulatory peptide (HARP), and heparin-binding
growth-associated molecule (HBGAM).