UNIT 3. HEMATOPOIESIS (PART 2)

• totipotential SC

• pluripotential SC

• multipotential SC

ENUMERATE

3 types of human HSC

Totipotential stem cells

most versatile type of stem cell

Totipotential stem cells

TYPE OF HSC

can develop into any human cell type

Totipotential stem cells

TYPE OF HSC

these cells are present in the first few hours after an ovum is fertilized

Pluripotential stem cells

TYPE OF HSC

these cells are present several days after fertilization

fetus

pluripotent SC can develop into any cell type except?

embryonic stem cells

ex of pluripotent SC

Pluripotential stem cells

TYPE OF HSC

can generate nearly all tissues in human body

Multipotential stem cells

TYPE OF HSC

these cells are derived from pluripotent stem cells

Multipotential stem cells

TYPE OF HSC

limited to specific types of cells to form tissues

Multipotential stem cells

TYPE OF HSC

limited to specific types of cells to form tissues

hematopoietic stem cells (HSCs)

ex of Multipotential stem cells

True

T or F

each tissue in the body arises from a tissue specific SC — multipotential SC

Monophyletic Theory

SC theory wherein all blood cells are derived from single hematopoietic stem cell hence it is most widely accepted

Polyphyletic Theory

SC theory wherein each of the blood cell lineages is derived from its own unique stem cell

1. Pluripotent

2. Multipotent

3. Totipotent

sequence the hierarchy of SCs

True

ie. megakaryocytic lineage, myeloid cells, lymphoid cells

T or F

each of the bld cell lineages is derived from its own unique SC

self renewing capability

what is the most important property of SC

Hematopoietic Stem Cells

give rise to all mature blood cells of the hematopoietic system

bone marrow

also present in small numbers in PB ↑ when there is administration of GF/chemotherapeutic agent — allows PB n BM as source of HSC for SC transplant.

HSC is mainly contained in the?

False

T or F

HSCs are morphologically recognizable cells

liver and spleen

extramedullary HSC in adult can be found in?

finite

HSCs have _________ lifespan

quiescent (G₀)

most of HSCs remain in ________ state, which makes them metabolically inactive, therefore HSC is exposed to less DNA damage induced by metabolic byproduct ROS (reactive oxygen spp) and helping preserve the stem cell pool throughout life.

True

T or F

progenitor cells are morphologically unrecognizable cells

1. multipotent progenitor cells (MPP)

2. lineage committed (oligopotent) progenitor cells

2 types of progenitor cells?

Lineage-Committed (Oligopotent) Progenitors

MPPs give rise to?

1. Common Myeloid Progenitors (CMP/CFU-GEMM)

2. Common Lymphoid Progenitors (CLP)

2 types of Lineage-Committed (Oligopotent) Progenitors

precursor (blast) stage

When do cells become morphologically recognizable?

Common Myeloid Progenitors (CMP/CFU-GEMM)

proliferates and differentiates into granulocytic, erythrocytic, monocytic, and megakaryocytic lineages

CMP or CLP

where do lineage-restricted progenitors arise from?

lineage-restricted progenitors

this progenitor cell have much more limited potential thus it is restricted to 1 or 2 blood cell lineages ONLY

• CFU-GM,

• CFU-Eo,

• CFU-Baso,

• CFU-MegE

ENUMERATE

lineage-restricted progenitors in CMP

Common Lymphoid Progenitors (CLP)

proliferates and differentiates into T, B, & NK cell and dendritic lineages

• Pro-B,

• Pro-T,

• Pro-NK

ENUMERATE

lineage-restricted progenitors in CLP

precursor cells

lineage-restricted progenitors give rise to _____________

Lineage-Specific Precursor Cells

committed to forming a specific type of mature blood cell

commitment

when a resulting cell loose their potential to develop as any other cell lineage — such loss is termed as ?

Mature Blood Cells

lineage-specific precursor cells will give rise to?

Mature Blood Cells

terminally differentiated cells, generally incapable of cell division

• Lin-

• CD34+

• CD38-

• CD90+

• CD45RA-

• CD49f+

MARKERS

Hematopoietic Stem Cells

flow cytometry

cell markers are used in immunophenotyping using ______________

• Lin-

• CD34+

• CD38-

• CD90-

• CD45RA-

• CD49f-

MARKERS

Multipotent Progenitors (MPPs)

• Lin-

• CD34+

• CD38+

• CD123+/low

• CD45RA-

[(+) and (-)]

MARKERS

Committed Myeloid Progenitors (CMPs)

• Lin-

• CD34+

• CD38+

• CD10+

[double neg']

MARKERS

Committed Lymphoid Progenitors (CLPs)

• Lin-

• CD34+

• CD38+

• CD123+

• CD45RA+

[double (+)]

MARKERS

GMPs (CFU-GM)

• Lin-

• CD34+

• CD38+

• CD123-

• CD45RA-

MARKERS

MEPs (CFU-Meg)

CD90+ and CD49f+

what are the markers that distinguishes HSCs from MPPs — these markers are less expressed as HSC becomes MPP

• CD33

• CD11b

• CD14

MAKRERS

Myeloid

• CD71

• GPA (Glycophorin A)

MAKRERS

Erythroid

• CD41

• CD61

MAKRERS

Megakaryocytic

• CD10

• CD19

MAKRERS

B-lymphoid

• CD3

• CD7

MARKERS

T-lymphoid

• Self-renewal

• Differentiation

• Apoptosis

what are the three possible fates of HSCs

Symmetric Division

HSCs divide → 2 identical daughter cells → both daughter cells leave the stem cell pool and undergo differentiation

Asymmetric Division

HSCs divide → 2 identical daughter cells → 1 daughter cell may return to the stem cell pool | 1 daughter cell may undergo differentiation

Instructive Model

THEORIES ON THE FATE OF THE STEM CELL 

Microenvironment in the BM determines whether the HSC will self-renew or differentiate

Stochastic Model (Till and McCulloch)

THEORIES ON THE FATE OF THE STEM CELL 

HSC randomly commits to self-renewal or differentiation

False

combination of both theories is accepted.

T or F

stochastic model is more accepted than instructive model

↓ N:C ratio

what is/are the morphologic changes tat occur as cell differentiates and matures?

• Loss of nucleoli

• Loss of nucleus

• ↓ diameter of nucleus

• Shape of nucleus

• Condensation of nuclear chromatin

ENUMERATE

changes in NUCLEUS as cell matures and differentiates

hematopoietic inductive microenvironment

the decision of a cell to proceed with lineage differentiation is triggered by various signals coming from the?

• ↓ in basophilia

• ↑ proportion of cytoplasm

• Possible appearance of granules in the cytoplasm

ENUMERATE

changes in CYTOPLASM as cell matures and differentiates

Intrinsic Factors

Internal regulators of HSCs involving genes that control stem cell development and hematopoiesis.

hemangioblast

is a bipotential progenitor of mesodermal origin that can become blood cells and blood vessels

TAL1

An intrinsic regulatory gene expressed in the hemangioblast

GATA2

An intrinsic regulatory gene expressed in late-appearing HSCs

TAL1 and GATA2

Essential intrinsic genes required for both primitive and definitive hematopoiesis.

Extrinsic Factors

External signals from the bone marrow microenvironment that regulate HSC behavior through growth factors and cytokines.

Regulatory Signaling Factors

Signaling pathways that enable HSCs to respond to the hematopoietic inductive microenvironment.

• Notch-1

• Notch-2

ex of Regulatory Signaling Factors

• TGF-β (Transforming Growth Factor-beta)

• JAK2 (Janus Kinase 2)

other ex of regulatory signaling factors other than notch 1 and 2

HEMATOPOIETIC GROWTH FACTORS OR CYTOKINES

group of specific glycoproteins that regulate the proliferation, differentiation and maturation of hematopoietic precursor cells

• interleukins (ILs)

• lymphokines

• monokines

• interferons

• chemokines

• colony-stimulating factors (CSFs)

ex of cytokines

• KIT ligand

• FLT3 ligand

• GM-CSF

• IL-1

• IL-3

• IL-6

• IL-11

ENUMERATE

Cytokines that exert positive influence (stimulatory)

• Growth factor-β

• Tumor necrosis factor-a

• Interferons

ENUMERATE

Cytokines that exert negative influence (inhibitory)

1. inhibit apoptosis

2. decrease the transit time from G₀ to G₁.

3. regulate cell differentiation into the various cell lineage

ENUMERATE

roles of cytokines

Apoptosis

process of eliminating unwanted, abnormal or harmful cells

COLONY-STIMULATING FACTORS

• have high specificity for their target cells

• active at low concentrations

GM-CSF (Granulocyte-Macrophage Colony Stimulating Factor)

Stimulates the formation of CFU-GM, leading to granulocyte and monocyte/macrophage production.

G-CSF (Granulocyte-Colony Stimulating Factor)

Stimulates the formation of CFU-G, promoting granulocyte production.

M-CSF (Macrophage-Colony Stimulating Factor)

Stimulates the formation of CFU-M, promoting monocyte/macrophage production.

• KIT Ligand (Stem Cell Factor)

• FLT3 Ligand

ex of EARLY-ACTING MULTILINEAGE GROWTH FACTORS

KIT Ligand : KIT

FLT3 Ligand : FLT3

KIT Ligand : _______

FLT3 Ligand : _______

INTERLEUKINS

protein molecules that regulate hematopoiesis

INTERLEUKINS

they have synergistic interactions with other cytokines to stimulate proliferation and differentiation of specific cell lines

• erythropoiesis

• leukopoiesis

• megakaryopoiesis

ENUMERATE

lineage-specific hematopoiesis

Erythropoietin (EPO)

Lineage-specific glycoprotein hormone produced specifically by the peritubular interstitial cells of the kidney

peritubular interstitial cells of the kidney ; small amnt in liver

EPO is produced at?

↓ oxygen : ↑ EPO production

__ oxygen : __ EPO production

Pluripotent HSC → Common Myeloid Progenitor/CFU-GEMM → BFU-E → CFU-E → Erythroid Precursor Cells → Mature erythrocytes

process of erythropoiesis

Burst-Forming Unit – Erythroid (BFU-E)

contains few receptors for EPO

Colony-Forming Unit – Erythroid (CFU-E)

contains many receptors for EPO

process of leukopoiesis

process of megakaryopoiesis

process of Lymphopoiesis

CD90 & CD49f

• HSC = CD90+, CD49f+

• MPP = CD90-, CD49f-

which surface marker/s are downregulated as cells mature from HSCs to MPPs?

CD123

CD45RA

which surface marker/s are present in GMPs (GFU-GM) but not in MEPs (GFU-MegE)?

CD38

which surface marker/s are upregulated as cells mature from MPPs to CMPs

CD 2, 3, 4, 7, 8, 10, 11b, 14, 19, 20, 56, 71, GPA

enumerate the lineage committed markers