Hematopoiesis - Cole Flashcards
Hematopoiesis regulated by
Adhesive interactions between the hematopoietic stem cells and hematopoetic progenitor cells within the bone marrow microenvironment
Hematopoiesis in the placenta
High capacity source of live and functional HSC
Provide abundant amounts of CD34+ and CD133+ colony-forming cells
During 7th month of intrauterine life what becomes primary site of hematopoiesis
Bone marrow
Red - presence of erythroid progenies
Yellow - adipose cells
Bone marrow
1.7 L of marrow contains 10^12 hematopoietic cells
Origin of all T and B cells, mononuclear phagocytes, erythrocytes and other leukocytes in the adult
Blood cells complete maturation immediately adjacent to the dilated vascular channels into which they will emigrate
2 compartments of bone marrow
Marrow stromal compartment
Hematopoietic cell compartment
Order: bone - endosteal niche - vascular niche
Marrow stromal compartment
Bone marrow - vascular niche
Niche for maintenance, self-renewal and expansion of stem cells
Hematopoietic cell compartment
In bone marrow - endosteal niche
Where stem cells live
Located near bone surfaces, forming the endosteal bone marrow
Stem cell niches
Maintain stem cells in a quiescent state
After tissue injury, the surrounding micro-enviro actively signals to stem cells to self-renew or differentiate
Bone marrow vascularization
Produce hematopoietic growth factors and cytokines that regulate production of blood cells
Endothelial cells form barrier that prevents immature from leaving marrow
Marrow adipose cells
Local source of energy and synthesize growth factors
Marrow macrophages
Remove apoptotic cells and residual nuclei from orthochromatic erythroblasts
Osteoblasts and osteoclasts
Maintain and remodel the cancellous bone surrounding the marrow tissue
Osteopontin
Glycoprotein produced by osteoblasts
Negative effect on the number of HSC
Transendothelial migration
How hematopoietic cells translocate from the site of growth through the sinusoid wall
Immature hematopoietic cells lack this capacity
3 Populations of hematopoietic cells in bone marrow
Hematopoietic stem cells
Committed precursor cells
Maturing cells
HSC in bone marrow
Capable of self-renewal
Can be identified by specific cell surface markers
Committed precursor cells in bone marrow
AKA multi potential stem cells
Colony forming units (CFUs)
Responsible for the generation of distinct cell lineages
-myeloid or lymphoid lineage
Maturing cells in bone marrow
Resulting from differentiation of the committed precursor cell population
-locked into specific lineage
5 Colony-forming units
Derive from the myeloid stem cell
- erythroid CFU
- megakaryocyte CFU
- basophil CFU
- eosinophil CFU
- granulocyte-macrophage CFU - monocytes and neutrophils
Hematopoietic cytokines
Control proliferative and maturational phases of hematopoiesis
AKA hematopoietic growth factors
3 major groups of hematopoietic growth factors
Colony-stimulating factors
Erythropoietin and thrombopoietin
Cytokines (primarily interleukins)
Erythropoiesis lineage sequence
Proerythroblast Basophilic erythroblast Polychromatophilic erythroblast Orthochromatic erythroblast Reticulocyte Erythrocyte
What cell type in erythroid lineage does EPO work on?
Proerythroblast
EPO
Major regulator of erythropoiesis
In response to hypoxia, stimulates the proliferation of erythroid progenitor cells by decreasing the levels of cell cycle inhibitors and increasing cyclins
