4- hematopoiesis and bone marrow eval Flashcards
In the extravascular space what is the stromal elements of the hematopoietic microenvironment
Stromal elements: endothelial cells, reticular (fibroblast-like) cells, adipocytes and extracellular matrix
in the extravascular space what are the accessory cells of the hematopoietic microenvironment
accessory cells: macrophages, T and B lymphocytes
what are the types hematopoietic cells
- hematopoietic stem cells (HSC)
- hematopoietic progenitor cells (HPC)
- recognizable blood cell precursors
- mature leukocyte storage pools, esp neutrophils
what are bone marrow stromal cells produced by
produced by mesenchymal stem cells
what do endothelial cells do in regards to bone marrow
they regulate the trans endothelial movement of cells btwn blood and them marrow extravascular space
what do reticular cells do in regards to bone marrow
fibroblastic-type cells they provide structural support for the bone marrow
what do both endothelial cells and reticular cells do
- synthesis of growth factor and extracellular matrix
- also support hematopoiesis through cell-cell contact
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HSCs and HPCs have what kind of appearance
lymphocyte appearance
HSCs are generally…
**positive for the CD34 surface antigen **
—- early HPCs are also CD34+
what is CD an abbreviation for
clusters of differentiation antigens
what are the properties of Hematopoietic stem cells (HSCs)
- proliferation
-sustained self replication - replicate slowly (once every 8-10 weeks)
- capacity to differentiate into all blood cell types and some tissue cell types (macrophages, dendritic cells, osteoclasts, mast cells)
- <0.0001% of nucleated cells in cat marrow
what do hematopoietic stem cells produce
common lymphoid progenitor (CLP)
— B lymphocytes, T lymphocytes, NK cells
common myeloid progenitor (CMP)
— non-lymphoid blood cells, macrophages, dendritic cells, osteoclasts, mast cells
what are the properties of hematopoietic progenitor cells (HPCs)
- proliferation
- limited self replication - not sustained without replenishment from HSCs
- replicate more rapidly than HSCs
- differentiation but with more restricted lineage potential than HSCs
- about 1% of bone marrow cells in adults, but higher in neonates
what are hematopoietic growth factors (HGFs)
HGFs are glycoprotein cytokines that promote the proliferation, maturation, and survival of hematopoietic cells
—— HGF includes colony stimulating factors (CSFs), interleukins and poietins
where are hematopoietic growth factors produced
HGFs are produced locally in the marrow (paracrine and autocrine) and/or by cells in peripheral tissues (endocrine ex. erythropoietin from the kidney)
what are the early acting factors of HGFs
early acting factors include stem cell factor (SCF) and fIt3 ligand (FL). these factors require the presence of other cytokines
what are the intermediate-acting factors for HGFs
The intermediate-acting factors include IL3 and GM-CSF
what are the late acting factors for HGFs
late acting factors include G-CSF, M-CSF, EPO, TPO, and IL5
what types of indirect stimulation causes the release of HGFs
during inflammation, TNFa, and IL1 stimulate stromal and accessory cells to release various HGFs
slide 19 canine precursor cells photo
slide 20 erythropoiesis photo
what are erythroid islands
-erythroid cells develop around macrophages
- macrophages help create microenvironment
- phagocytize expelled nuclei and damaged or aged erythrocytes
- store iron released from phagocytized erythrocytes
add photo
Explain the properties of reticulocytes
- formed when metarubicytes expel their nuclei, usually while still bound to macrophages
- one rubriblast produces about 16 reticulocytes in about 4 days
- reticulocyte maturation occurs in marrow, blood, and spleen, depending on the species
what does erythropoietin (EPO) do
—- glycoprotein growth factor
promotes proliferation, differentiation, and survival erythroid progenitor cells and early erythroid precursors (ex rubriblasts)
inhibition of apoptosis is the main mechanism of action
what are the sites of EPO synthesis
renal interstitial cells (primary site in adults)
- increased synthesis in response to tissue hypoxia in the kidney
extrarenal production
- liver, especially in the mammalian fetus
- bone marrow macrophages and erythroid cells
neutrophil production slide 28
what are the neutrophilic growth factors
- early and intermediate acting factors
G-CSF - late acting factor
— granulocyte progenitors to myeloblasts
— increased cell division, decrease marrow transit time
Cells producing various growth factors
– fibroblasts and endothelial cells
– T lymphocytes and mononuclear phagocytes
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explain eosinophil production
- marrow transit time 1 week or less
- marrow storage pool like neutrophils
- early and intermediate acting factors
- IL5 from TH2 lymphocytes for terminal maturation
how are mast cells produced
mast cells progenitor (MaP) released form marrow to blood
- mast cells develop in tissues
-* stem cell factor promotes development *
what are monocytopoiesis
short generation time and little marrow reserve
- M-CSF is a late activation factor stimulation monocyte production
monocytes may become
- *macrophages *or inflammatory dendritic cells in tissues
- osteoclasts in bone marrow
- depends on the amounts of various cytokines presents
what are osteoclasts
osteoclasts are multinucleated cells which degrade bone
- develop from monocyte fusion
lymphopoiesis - slide 41
thrombopoiesis slide 42
megakaryocytes properties
Depending on size - 1000 to 3000 platelets produced/ megakaryocyte
— Megakaryocytes are located just outside the vascular sinuses
proplatelet processes extend into the vascular sinuses and platelets from the proplatelet processes within the vasculature
how are non mammals different
- no megakaryocytes
- thromboblasts produce thrombocytes
- the only giant cell in marrow is the osteoclast
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what promotes the stimulation of thrombopoiesis
early and intermediate- acting growth factors
– proliferation and expansion of megakaryocyte progenitor cells
Thrombopoietin (TPO)
- promotes differentiation of progenitor cells into megakaryocytes
- stimulates increased endomitosis, resulting in increased ploidy and size
where is thrombopoietin produced
major site of production - endothelial cells of liver
– inflammatory cytokine IL6 stimulates TPO synthesis by liver during inflammation
what is the purpose of recombinant growth factors
recomb human EPO and G-CSF have been used to treat animals
- they work for a short period of time, but antibodies are made against these glycoproteins, which limits their effectiveness
These antibodies may even cross- react with animals own EPO and G-CSF, when can make matters worse
dog and cat recombinant growth factors have been made, but to my knowledge are not commercially aval
list the reasons for bone marrow exam
- unexplained cytopenias in blood
- proliferative abnormalities with unexplained left shifts, nucleated erythroid cells, or blast cells in blood
- staging lymphomas or mast cell tumors
- evaluate iron stores (except in cats)
- evaluate focal lesions in bone (infections or neoplastic)
- unexplained hyperproteinemia in blood (ex plasma cell neoplasms)
- unexplained hypercalcemia (ex T-cell neoplasms)
what are bone marrow aspirate smears
simple, fast, relatively inexpensive
– ID individual cell types and stages with routine blood stains
– prussian blue stain for iron
used for cytochemistry and immunocytochemistry to ID neoplastic cells
How is an aspirate collected (with anticoag)
- aspirate syringe contains EDTA in sterile saline solu
- aspirate material is expelled in a petri dish and a pipette is used to collect particles to use in squash preparations
(this allows for more slides to be prepped for special stains)
what are bone marrow core biopsys
they give a better eval of overall cellularity done after unsuccessful aspirate attempts
- diagnosis of myelofibrosis
- Identification of focal lesions that may occur with metastatic neoplasia, necrosis, or granulomatous inflammation
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what is evaluated during a bone marrow exam
scan for particles and est, overall cellularity
- evaluate the number, morphology, and stages of megakaryocyte developments
- evaluate the number, morphology, and development of erythrocytic and granulocytic cells
—————-Calculate the M:E ratio (granulocytic: erythrocytic)
evaluate the number and morphology of other cell types present including lymphocytes, plasma cells, and macrophages.
assess the amount of hemosiderin present
normal marrow cellularity on a dog
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what do you see regarding megakaryocytes in bone marrow aspirate
most large particles have several megakaryocytes
- normally 3-15 megakaryocytes within particles per low-power field (10x)
**Normally 80-90% are mature **
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how do you interpretation of M:E ratio
knowledge of overall marrow cellularity, Hct and total neutrophil count in blood is critical
**- If the absolute blood neutrophil count is normal, changes in the M:E ratio generally reflect changes in the erythroid series **
**- If the Hct is normal, changes in M:E generally reflect changes in the neutrophilic series **
- if both Hct and total neutrophil count are abnormal, the interpretation is more difficult
- if the marrow is markedly hypoplastic of filled with neoplastic cells, the M:E ratio is of little value
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