HAEMATOPOIESISHAEMATOPOIESISDr Rosline HassanDr Rosline Hassan

Hematology DepartmentHematology Department

School of Medical SciencesSchool of Medical Sciences

Universiti Sains MalaysiaUniversiti Sains Malaysia

Organization of the Organization of the hematopoietic systemhematopoietic system

EmbryologyEmbryology

Anatomy of the marrowAnatomy of the marrow

Stem cellsStem cells

Marrow stromaMarrow stroma

Hematopoietic growth factorsHematopoietic growth factors

ErythropoiesisErythropoiesis

GranulopoiesisGranulopoiesis

ThrombopoiesisThrombopoiesis

HaematopoiesisHaematopoiesis

Definition : production of red blood Definition : production of red blood cells, white cells and platelets cells, white cells and platelets

175 billion red blood cells/day 175 billion red blood cells/day 70 billion granulocytes/day 70 billion granulocytes/day

(neutrophils, eosinophils, basophils) (neutrophils, eosinophils, basophils) 175 billion platelets/day 175 billion platelets/day Capable of 5-10 fold increase in Capable of 5-10 fold increase in

production production

EmbryogenesisEmbryogenesis

Dev.Dev. ageage SitesSites

FoetusFoetus 0-2 0-2 monthsmonths

Yolk sacYolk sac

2-7 2-7 monthsmonths

Liver & spleenLiver & spleen

5-9 5-9 monthsmonths

Bone marrowBone marrow

InfantsInfants Bone marrow (all bones)Bone marrow (all bones)

AdultsAdults Vetebrae, ribs, sternum, Vetebrae, ribs, sternum, sacrum, pelvis and proximal end sacrum, pelvis and proximal end of femur.of femur.

Mesoblastic phaseMesoblastic phase 2nd week - 3rd month2nd week - 3rd month Cell clusters in yolk sacCell clusters in yolk sac

Hepatic phaseHepatic phase 2nd - 6th month2nd - 6th month Mainly liver with Mainly liver with

supplementation from supplementation from spleenspleen

Myeloid phaseMyeloid phase 6th month – adult6th month – adult Red bone marrowRed bone marrow

Anatomy of Marrow Anatomy of Marrow

Volume of bone marrow at birth: Volume of bone marrow at birth: 1.5%1.5%

of body weightof body weight Volume of bone marrow as an adult:Volume of bone marrow as an adult:

4.5% of body weight4.5% of body weight

HaematopoiesisHaematopoiesis

Anatomy of MarrowAnatomy of Marrow

Histology Histology Vascular CompartmentVascular Compartment Hematopoietic CompartmentHematopoietic Compartment

hematopoietic stem cellshematopoietic stem cells Precursor cellsPrecursor cells growth factor growth factor hemotopoietic microenvironment (stroma)hemotopoietic microenvironment (stroma) site for formation and maturationsite for formation and maturation

Cellularity 30-70% Cellularity 30-70%

Haematopoietic cellsHaematopoietic cells

Stem Cells Stem Cells Pluripotential Stem Cells Pluripotential Stem Cells

Self Renewal Self Renewal DifferentiationDifferentiation ProliferationProliferation

Multipotential Stem Cells – ( Lymphoid, Multipotential Stem Cells – ( Lymphoid, Myeloid Stem Cells)Myeloid Stem Cells)

Progenitor Cells - CFU's (Colony Forming Progenitor Cells - CFU's (Colony Forming Units)Units)

Stem cellStem cell

Multipotential stem cell

Progenitor cells

Haematopoietic cellsHaematopoietic cells

Precursor Cells - Blasts and their Precursor Cells - Blasts and their progeny progeny First morphologically identifiable cells First morphologically identifiable cells

Normoblast - Red Cells Normoblast - Red Cells Myeloblast – GranulocytesMyeloblast – Granulocytes Monoblast – MonocytesMonoblast – Monocytes Lymphoblast – LymphocytesLymphoblast – Lymphocytes Megakaryoblast - PlateletsMegakaryoblast - Platelets

Little if any self-renewalLittle if any self-renewal

Haematopoietic cellsHaematopoietic cells

Mature Effector CellsMature Effector Cells Red Cells – carry oxygen, carbon Red Cells – carry oxygen, carbon

dioxide; lifespan 120 daysdioxide; lifespan 120 days Neutrophils – phagocytosis, killing Neutrophils – phagocytosis, killing Monocytes – phagocytosis, killing, Monocytes – phagocytosis, killing,

antigen presentationantigen presentation Lymphocytes – immune responseLymphocytes – immune response Platelets – haemostasisPlatelets – haemostasis

Normal Peripheral BloodNormal Peripheral Blood

Eosinophil

Neutrophil

Lymphocyte

Basophil

Monocyte

MicroenvironmentMicroenvironmentForms a suitable environmentForms a suitable environment forfor stem cell stem cell growth and development.growth and development.

Composed of stromal cells & a microvascular Composed of stromal cells & a microvascular networknetwork

Bone Marrow Stromal CellsBone Marrow Stromal Cells - key role in marrow - key role in marrow Fibroblasts, fat cells, endothelial cells, reticulum Fibroblasts, fat cells, endothelial cells, reticulum

cells and macrophagecells and macrophage Express Adhesion Molecules Express Adhesion Molecules Secrete Growth FactorsSecrete Growth Factors and extracellular molecules and extracellular molecules

(collagen, glycoproteins & glycosaminoglycans) (collagen, glycoproteins & glycosaminoglycans) forming extracellular matrixforming extracellular matrix

Stromal matrixStromal matrix Physical Support for Hematopoietic Cells Physical Support for Hematopoietic Cells

Haemopoiesis occur within Haemopoiesis occur within microenvironmentmicroenvironment

Stem cells are in contact Stem cells are in contact with other cellwith other cell

(e.g macrophage, (e.g macrophage, fibroblast)fibroblast)

Cell-cell communication isCell-cell communication is

by binding via cell surface by binding via cell surface receptors, to adhesion receptors, to adhesion molecules & secretion of molecules & secretion of cytokines & GFs cytokines & GFs

These binding lead to These binding lead to proliferation, proliferation, differentiation & apoptosisdifferentiation & apoptosis

bone

Fat cells

vessel

Hemopoietic cells

Haematopoietic Growth Haematopoietic Growth FactorsFactors

Glycoprotein hormonesGlycoprotein hormones Function :Function : Progenitor cellsProgenitor cells

ProliferationProliferation DifferentiationDifferentiation MaturationMaturation

Act – locally or circulate Act – locally or circulate in plasmain plasma

Produced by :Produced by : lymphocyteslymphocytes monocytesmonocytes macrophagesmacrophages

e.g : IL-1, TNF, IL-3, erythropoietine.g : IL-1, TNF, IL-3, erythropoietin

Mature blood cellsMature blood cells Functional activationFunctional activation Prevention of apoptosisPrevention of apoptosis

endothelial cells endothelial cells fibroblastsfibroblasts

ClassificationClassification Non lineage specific GFNon lineage specific GF

Act on pluripotential & Act on pluripotential & multipotential stem cells to multipotential stem cells to initiate self renewal & initiate self renewal & differentiationdifferentiation

e.g :IL-3, GM-CSFe.g :IL-3, GM-CSF Lineage specific GFLineage specific GF

Act on progenitor cells, involve in Act on progenitor cells, involve in differentiation & maturation of differentiation & maturation of cells cells

e.g :CSF, M-CSF, erythropoetin e.g :CSF, M-CSF, erythropoetin & thrombopoietin& thrombopoietin

Lymphokine and Lymphokine and monokinesmonokines Release by lymphocytes & Release by lymphocytes &

monocytes monocytes e.g : interleukin-1 (IL-1)e.g : interleukin-1 (IL-1)

HaematopoiesisHaematopoiesis

ErythropoiesisErythropoiesis Occurs near the sinus apertures Occurs near the sinus apertures Seen as erythroblastic islands surround Seen as erythroblastic islands surround

the macrophages the macrophages Matured red cell squeeze through the Matured red cell squeeze through the

aperture leaving their nuclei behindaperture leaving their nuclei behind GranulopoiesisGranulopoiesis

Occurs deep in the cordsOccurs deep in the cords Mature cells become motile at the Mature cells become motile at the

metamyelocyte stagemetamyelocyte stage

LymphopoiesisLymphopoiesis Leave the bone marrow and complete Leave the bone marrow and complete

differentiation in the lymph nodes (B differentiation in the lymph nodes (B cells) and thymus (T cells)cells) and thymus (T cells)

ThrombopoiesisThrombopoiesis Occurs along the outside surface of the Occurs along the outside surface of the

vascular sinuses vascular sinuses Release strings of cytoplasmic platelet Release strings of cytoplasmic platelet

directly into the circulation. directly into the circulation.

ErythropoiesisErythropoiesis

RBC development takes about 7 daysRBC development takes about 7 days Involves 3 to 4 mitotic cell divisionsInvolves 3 to 4 mitotic cell divisions Each stem cell gives rise to 8 or 16 cellsEach stem cell gives rise to 8 or 16 cells Stages of RBC development characterized byStages of RBC development characterized by

1.1. gradual appearance of haemoglobingradual appearance of haemoglobin

2.2. disappearance of ribonucleic acid (RNA)disappearance of ribonucleic acid (RNA)

3.3. progressive degeneration of nucleusprogressive degeneration of nucleus

4.4. gradual loss of cytoplasmic organelles e.g gradual loss of cytoplasmic organelles e.g mitochondriamitochondria

5.5. gradual reduction in cell sizegradual reduction in cell size

Substances required for erythropoiesis :Substances required for erythropoiesis :

i.   Metal (e.g: iron, mangenese & cobalt)i.   Metal (e.g: iron, mangenese & cobalt)

ii.  Vitamin (e.g: Bii.  Vitamin (e.g: B1212, Folate, Vit C, Vit E, Vit , Folate, Vit C, Vit E, Vit

BB6 6 (pyridoxine), thiamine, (pyridoxine), thiamine,

riboflavin riboflavin & pantothenic acid)& pantothenic acid)

iii.  Amino acidiii.  Amino acid

iv.iv. Hormones (e.g: stem cell factor, IL-3, Hormones (e.g: stem cell factor, IL-3, GM-GM- CSF, erythropoietin, CSF, erythropoietin, androgen androgen & thyroxine)& thyroxine)

Life cycle of RBCsLife cycle of RBCs

1.1. Kidneys respond to lower Kidneys respond to lower oxygen concentration in blood oxygen concentration in blood releasing erythropoietin (EPO). releasing erythropoietin (EPO).

2.2. EPO travels to red marrow and EPO travels to red marrow and stimulates production of RBCs stimulates production of RBCs

3.3. Red marrow produces RBCs Red marrow produces RBCs from stem cellsfrom stem cells

4.4. RBCs squeeze through vessel RBCs squeeze through vessel membrane to enter circulationmembrane to enter circulation

5.5. Heart and lungs work to Heart and lungs work to supply oxygenation of RBCs. supply oxygenation of RBCs.

6.6. Damaged or old RBCs Damaged or old RBCs destroyed by the spleen.destroyed by the spleen.

LeukopoiesisLeukopoiesis

Leukopoiesis (white blood cell Leukopoiesis (white blood cell formation) encompasses both formation) encompasses both granulopoiesis and agranulopoiesis. granulopoiesis and agranulopoiesis.

Granulopoiesis occurs in the bone Granulopoiesis occurs in the bone marrow of healthy adults.marrow of healthy adults.

Kinetics of Neutrophil Production - 14 Kinetics of Neutrophil Production - 14 days from myeloblast to neutrophil.days from myeloblast to neutrophil.

GranulopoiesisGranulopoiesis

3 types of granulocytes (derive from a 3 types of granulocytes (derive from a single precursor CFU-G)single precursor CFU-G)

NeutrophilsNeutrophils BasophilsBasophils EosinophilsEosinophils

The structural changes include The structural changes include 1.1. Decrease in cell sizeDecrease in cell size

2.2. Condensation of nuclear chromatinCondensation of nuclear chromatin

3.3. Changes in nuclear shape (flattening Changes in nuclear shape (flattening →→ indentation indentation →→ lobulation lobulation

4.4. Accumulation of cytoplasmic granulesAccumulation of cytoplasmic granules

Stages of maturation :Stages of maturation :

1.1. MyeloblastMyeloblast2.2. Promyelocyte Promyelocyte (1(10 0

granules)granules)

3.3. Myelocyte (Myelocyte (220 0 granules)granules) Last mitotically active Last mitotically active

stage in granulopoiesis.stage in granulopoiesis.

4.4. MetamyelocyteMetamyelocyte

5.5. Band neutrophil / stab Band neutrophil / stab formform

LymphopoiesisLymphopoiesis

Production of lymphocytes.Production of lymphocytes. Lymphoid stem cells give rise to the major Lymphoid stem cells give rise to the major

functional classes of lymphocytes :functional classes of lymphocytes :

i.  B cells (Undergo differentiation to i.  B cells (Undergo differentiation to become become plasma cells and plasma cells and produce produce immunoglobulin.immunoglobulin.

ii.  T cellsii.  T cells

iii.  NK cellsiii.  NK cells

Arise from progenital cells responsible for Arise from progenital cells responsible for the production of granulocytes, the production of granulocytes, monocytes, red blood cells & platelet monocytes, red blood cells & platelet 

The differentiation involve :The differentiation involve : acquisitionacquisition loss of series of surface antigen loss of series of surface antigen defined by defined by monoclonal antibodies.monoclonal antibodies.

Antigen Independent PhaseAntigen Independent Phase Initial lymphopoiesis takes place in bone marrow Initial lymphopoiesis takes place in bone marrow Maturation takes places in lymph nodes or Maturation takes places in lymph nodes or

thymus thymus Antigen Dependent PhaseAntigen Dependent Phase

Second cycle of differentiation and proliferation Second cycle of differentiation and proliferation in response to antigen exposure in response to antigen exposure

Antibody and Hematopoietic Growth Hormone Antibody and Hematopoietic Growth Hormone Production Production

Memory Phase Memory Phase Follows antigen exposureFollows antigen exposure May live for years May live for years

ThrombopoiesisThrombopoiesis

Production of platelet.Production of platelet. Platelet are shed from the cytoplasm Platelet are shed from the cytoplasm

of megakaryocytes.of megakaryocytes. Megakaryocytes developed in the Megakaryocytes developed in the

bone marrow from the bone marrow from the megakaryocyte colony forming units megakaryocyte colony forming units (CFU-Mega) also derived from (CFU-Mega) also derived from pluripotential stem cells. pluripotential stem cells. 

Megakaryocytes maturation :Megakaryocytes maturation :

1.1. Endomitotic synchronous nuclear replication Endomitotic synchronous nuclear replication (nucleus divides, not cell - max 64 segments)(nucleus divides, not cell - max 64 segments)

2.2. Enlarging cytoplasmic volume Enlarging cytoplasmic volume

3.3. Cytoplasm become granularCytoplasm become granular

4.4. Demarcation of membrane of individual Demarcation of membrane of individual plateletsplatelets

Individual platelet or larger fragments are broken Individual platelet or larger fragments are broken off & carried by blood to lungs where the off & carried by blood to lungs where the breakdown is completed in pulmonary circulationbreakdown is completed in pulmonary circulation..

They circulate for 6-8 days, then destroyed in They circulate for 6-8 days, then destroyed in spleen or pulmonary vascular bed.spleen or pulmonary vascular bed.

Summary Summary Haematopoiesis is a process of blood cells productionHaematopoiesis is a process of blood cells production It begins very early in prenatal period and continues till adultIt begins very early in prenatal period and continues till adult The process requiresThe process requires

Stem cellsStem cells MicroenvironmentMicroenvironment

Stromal cellsStromal cells Stromal MatrixStromal Matrix

Other substancesOther substances Stem cells undergo differentiation & self renewal Stem cells undergo differentiation & self renewal Progenitor cells undergo differentiation and maturationProgenitor cells undergo differentiation and maturation Mature cells release into blood circulationMature cells release into blood circulation Most of cells will reenter the tissue phase and undergo Most of cells will reenter the tissue phase and undergo

apoptosisapoptosis