Hematopoietic stem cells are found in the bone marrow of adults, especially in the pelvis, femur, vertebral bodies and sternum. All blood cells are derived from embryonic Pluripotent Hematopoietic Stem cells (PHSC).
Growth and conversion of stem cells are regulated by growth inducers, including the interleukins (IL-3 stimulates most types of progenitor cells), stem cell factor (SCF) and colony-stimulating factors (eg, G-CSF and GM-CSF).
Each blood cells are formed from their progenitor cells (e.g. CFU–GM – Granulocyte Monocyte colony forming unit, CFU-Meg – Megakaryotic progenitor cells forms megakaryoblast, BFU-E – Burst Forming Unit E generate erythrocyte by differentiation).
- Erythropoietin (EPO) promotes differentiation of erythroblasts into erythrocytes
- Thrombopoietin (Tpo) promotes differentiation of CFU-Meg (Megakaryocyte colony forming unit) into Megakaryoblast and then Platelets.
- Stem Cell Factor (SCF) Stimulates early stem cells to self-renewal and differentiate
- Transforming Growth Factor (TGF-beta) Inhibits hematopoiesis