dr Sri Lestari Sulistyo Rini, MSc HEMATOPOIESIS dr Sri Lestari Sulistyo Rini, MSc

Hematopoiesis Hematopoiesis (hemopoiesis): blood cell formation Occurs in red bone marrow of axial skeleton, girdles and proximal epiphyses of humerus and femur

Hematopoiesis Hemocytoblasts (hematopoietic stem cells) Give rise to all formed elements Hormones and growth factors push the cell toward a specific pathway of blood cell development New blood cells enter blood sinusoids

Hematopoiesis: Stem cells in bone marrow proliferate differentiate mature myeloid vs. lymphoid Stromal cells secrete growth factors Cytokines signal via membrane receptors

Bone marrow Bone marrow stromal cells secrete growth factors Hematopoietc stem cells respond

Stem cells Hemocytoblast Myeloid stem cell Lymphoid stem cell Committed cells Myeloblast Myeloblast Myeloblast Monoblast Lymphoblast Developmental pathway Promyelocyte Promyelocyte Promyelocyte Promonocyte Prolymphocyte Eosinophilic myelocyte Basophilic myelocyte Neutrophilic myelocyte Eosinophilic band cells Basophilic band cells Neutrophilic band cells Eosinophils Basophils Neutrophils Monocytes Lymphocytes (a) (b) (c) (d) (e) Agranular leukocytes Some become Granular leukocytes Some become

Blood Cell Production

Growth factors signal through membrane receptors: Hematopoiesis involves cytokine signaling Growth factors signal through membrane receptors: Ligand causes receptors to aggregate Activates JAK (kinases) by phosphorylation (cytoplasmic RTK) JAK phophorylates cytokine receptor on Tyr

Hematopoiesis involves cytokine signaling Other signaling molecules bind, including STAT (signal transducer and activator of transcription) → nucleus transcription Also RAS/Raf/MAP kinase activated Overactive signal → cancer Transient signal: SOCS silences

Normal Marrow Composition 60% 20% 10% unidentified or disintegrated cells erythroid precursors Lymphocytes, monocytes granulocytes & precursors

Hematopoietic Growth Factors (SCF, IL-6, GM-CSF, etc.) glycoprotein hormones secreted by bone marrow stromal cells T-cells monocytes regulate division and differentiation of hematopoietic cells responsible for basal hematopoiesis and maintaining blood counts in normal ranges greatly increased secretion in response to infection

Erythropoiesis erythropoietin-independent stage: GM-CSF SCF erythropoietin-dependent stage: erythropoietin marrow stromal cells IL-3 (activated T-cells) hypoxia(liver, kidney)

Granulopoiesis early phase: Neutropoiesis: Monopoiesis: Eosinopoiesis: Basopoiesis,Mastpoiesis: GM-CSF SCF IL-3 G-CSF M-CSF IL-5 IL-3 GM-CSF SCF IL-3

Megakaryopoiesis may also play a role IL-3 GM-CSF SCF IL-6

Lymphopoiesis B-cells: T-cells: CD8 cells: initial stage: later stage: final proliferation and Ab secretion: T-cells: CD8 cells: CD4 cells: IL-7 SCF Fcg rec IL-4 IL-6 GM-CSF IL-6 IL-2 Ag TCR/CD3 CD28

Hematopoietic Growth Factors (IL-6, GM-CSF, SCF, etc.) Bacterial & viral products monocyte GM-CSF IL-3 T-cell IL-1 TNFa G-CSF M-CSF IL-6 GM-CSF G-CSF Fibroblast Endothelial cell

Hematopoietic Microenvironment Stromal cells: fibroblasts endothelial cells adipocytes Growth Factors

Basal Hematopoiesis SCF IL-6 GM-CSF G-CSF SCF: stem cell factor GM-CSF: granulocyte-macrophage colony-stimulating factor G-CSF: granulocyte colony-stimulating factor

Antigen-amplified hematopoiesis TNFa IL-1 SCF IL-6 GM-CSF G-CSF Ag IL-1 IL-3 GM-CSF IL-4 TNFa

Erythropoiesis Erythropoiesis: red blood cell production A hemocytoblast is transformed into a proerythroblast Proerythroblasts develop into early erythroblasts

Erythropoiesis Phases in development Ribosome synthesis Hemoglobin accumulation Ejection of the nucleus and formation of reticulocytes Reticulocytes then become mature erythrocytes

RBC Formation before birth Mesoblastic stage Nucleated RBCs - Yolk sac and Mesothelial layers of the placenta – 3rd week Hepatic stage At 6 weeks - Liver form blood cells Spleen + lymphoid tissues form blood cells.

RBC Formation before birth Myeloid stage From the third month onwards - the bone marrow gradually becomes the principal source of the RBCs Last month – Bone marrow exclusively

RBC Formation after birth The bone marrow - all bones - 5 years Marrow of the long bones (except for the proximal humerus and tibia) No more red blood cells after = age 20 years. Most red cells continue to be produced in the marrow of the membranous bones, such as Vertebrae, Sternum, Ribs, and Ilium.

Relative rates of red blood cell production in the bone marrow of different bones at different ages.

Bone marrow cells for Erythropoiesis Pluripotential hematopoietic stem cell, PHSC Committed stem cell that produces erythrocytes is called Colony-forming unit–erythrocyte, CFU-E Factors: Growth inducers Differentiation inducers.

Polychromatophil erythroblast Orthochromatophil erythroblast ERYTHROPOIESIS PHSC CFU-E Proerythroblast Polychromatophil erythroblast Orthochromatophil erythroblast Reticulocyte Erythrocyte. Bone marrow 4-5 days Blood 1-2 days.

Erythropoiesis Phases in development Ribosome synthesis in early erythroblasts Hemoglobin accumulation in late erythroblasts and normoblasts Ejection of the nucleus from normoblasts and formation of reticulocytes Reticulocytes then become mature erythrocytes 1 -2 % of all circulating erythrocytes

Stem cell Committed cell Developmental pathway Phase 1 Ribosome synthesis Phase 2 Hemoglobin accumulation Phase 3 Ejection of nucleus Proerythro- blast Early erythroblast Late erythroblast Reticulo- cyte Erythro- cyte Hemocytoblast Normoblast

Regulation of Erythropoiesis Too few RBCs leads to tissue hypoxia Too many RBCs increases blood viscosity Balance between RBC production and destruction depends on Hormonal controls : Erythropoietin (EPO) Direct stimulus for erythropoiesis Released by the kidneys in response to hypoxia Adequate supplies of iron, amino acids, and B vitamins

Hormonal Control of Erythropoiesis Effects of EPO More rapid maturation of committed bone marrow cells Increased circulating reticulocyte count in 1–2 days Testosterone also enhances EPO production, resulting in higher RBC counts in males

Hormonal Control of Erythropoiesis Causes of hypoxia Hemorrhage or increased RBC destruction reduces RBC numbers Insufficient hemoglobin (e.g., iron deficiency) Reduced availability of O2 (e.g., high altitudes)

Erythropoietin Mechanism Imbalance Start Normal blood oxygen levels Stimulus: Hypoxia due to decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2 Imbalance Increases O2-carrying ability of blood Reduces O2 levels in blood Erythropoietin stimulates red bone marrow Kidney (and liver to a smaller extent) releases erythropoietin Enhanced erythropoiesis increases RBC count Figure 17.6

Dietary Requirements for Erythropoiesis Nutrients—amino acids, lipids, and carbohydrates Iron Stored in Hb (65%), the liver, spleen, and bone marrow Stored in cells as ferritin and hemosiderin Transported loosely bound to the protein transferrin Vitamin B12 and folic acid—necessary for DNA synthesis for cell division

(a) Normal erythrocyte has normal hemoglobin amino acid sequence in the beta chain. 1 2 3 4 5 6 7 146 (b) Sickled erythrocyte results from a single amino acid change in the beta chain of hemoglobin. 1 2 3 4 5 6 7 146

Formation & Destruction of RBCs

Leukopoiesis Production of WBCs Stimulated by chemical messengers from bone marrow and mature WBCs Interleukins (e.g., IL-1, IL-2) Colony-stimulating factors (CSFs) named for the WBC type they stimulate (e.g., granulocyte-CSF stimulates granulocytes) All leukocytes originate from hemocytoblasts

Production of Leukocytes Leukopoiesis is hormonally stimulated by two families of cytokines (hematopoietic factors) – interleukins and colony-stimulating factors (CSFs) Macrophages and T cells are the most important sources of cytokines Many hematopoietic hormones are used clinically to stimulate bone marrow

Formation of Leukocytes All leukocytes originate from hemocytoblasts The mother of all blood stem cells Hemocytoblasts differentiate into myeloid stem cells and lymphoid stem cells Myeloid stem cells become myeloblasts or monoblasts Granulocytes form from myeloblasts Monoblasts enlarge and form monocytes Lymphoid stem cells become lymphoblasts Lymphoblasts develop into lymphocytes

Platelets Small fragments of megakaryocytes Formation is regulated by thrombopoietin Blue-staining outer region, purple granules Granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)

Platelets Form a temporary platelet plug that helps seal breaks in blood vessels Circulating platelets are kept inactive and mobile by NO and prostacyclin from endothelial cells of blood vessels

Stem cell Developmental pathway Hemocyto- blast Promegakaryocyte Megakaryoblast Megakaryocyte Platelets

Lifespan of blood cells RBC 120 days platelet 10 days granulocytes circ : 9 hours tissue : days lymphocyte circ : variable (hours to years) tissue : weeks to years

Hematopoietic Response hypoxia RBC infection granulocyte/monocyte antigen lymphocyte hemorrhage platelet

TERIMA KASIH