1. No category

Cell-based Coagulation
Coagulation System Overview
And Cell-Based Coagulation
Coagulation Summary
George A. Fritsma, MS MLS
The Fritsma Factor
Your Interactive Hemostasis Resource
george@fritsmafactor.com
1
A 3 year-old boy experienced painful joints. His
hematologist ordered a prothrombin time (PT), activated
partial thromboplastin time (PTT), and platelet count.
Results:
Platelet count
PT
PTT
3/22/2015
Platelets
Plasma-based cascade
Coagulation controls
Fibrinolysis
Cell-based coagulation
Virtues and limitations
Cell-based Coagulation
RI
150–400,000/uL
12.6–14.6 sec
25–35 sec
•  Liver disease, vitamin K deficiency, renal
disease?
–  No symptoms, normal diet, PT normal
–  Liver enzymes normal
•  Lupus anticoagulant?
–  Unlikely in child
•  Inherited single factor deficiency
3
PT and PTT Test Results
in Inherited Coagulopathies
PT
Long
Long
Normal
PTT
Congenital Single Factor
Deficiency (Hemophilia)
Normal VII
Long X, V, II, and fibrinogen1
VIII, IX, XI
Long Contact factors: XII, prekallikrein,
high MW kininogen2
1.  PT and PTT are prolonged only when fibrinogen is < 100 mg/dL
5
2.  Contact factor deficiencies affect PTT results, but do not cause bleeding
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2
What are the Possibilities?
3 YO Boy: Chronic Joint Pain
Result
324,000/uL
12.9 sec
67 sec
• 
• 
• 
• 
• 
• 
4
A 3 Year-old Boy: Easy Bruising
Single Factor Assay Results
Factor
VIII
IX
XI
RI
Result
12%
95%
108%
50–150%
•  Implications of factor VIII deficiency: hemophilia A
•  The mild form accounts for late onset and mild symptoms
•  Therapy: RICE, DDAVP, tranexamic acid, FVIII concentrate
6
1
Cell-based Coagulation
Plasma-Based Coagulation Model
1964–2004
SMC
Internal Elastic Lamina
EC
•  Davie EW, Ratnoff OD. Waterfall sequence for intrinsic blood clotting. Science 1964; 145:
1310–12.
•  Macfarlane RG. An enzyme cascade in the blood clotting mechanism and its function as a
biological amplifier. Nature 1964; 202: 498–9.
•  Nemerson Y. The tissue factor pathway of blood coagulation. Semin Hematol 1992;29:170–6.
EC
EC
• 
• 
• 
• 
• 
• 
• 
• 
• 
• 
Plasminogen activator inhibitor -1
Tissue factor pathway inhibitor
Tissue plasminogen activator
Negative surface charge
Prostacyclin (PGI2)
EC
Thrombomodulin
Heparan sulfate
ADPase (CD39)
SMC
Nitric oxide
Urokinase
EC
EC
Integrins bind:
α1β1 : fibronectin
αvβ1 : collagen
α3β1 : laminin
α6β1 : laminin
α2β3 : vitronectin
EC
EC
Cytokines:
•  IL-1
•  TNF
•  γ-interferon
EC
EC
Permeability
RBC
RBC
PLT
EC
EC
EC
SMC
FB
EC
EC
SMC
FB
Collagen
SMC
FB
EC
EC
EC
EC
EC
EC
• 
• 
• 
• 
• 
Collagen, fibronectin, vitronectin, laminin
Membrane phospholipids
Von Willebrand factor
PLT
Heparan sulfate
Tissue factor
EC
EC
EC
Tunica
Intima
EC
Chemokines:
Adhesion Molecules:
ICAM-1
ICAM-2
VCAM-1
PECAM
P-selectin
EC: Endothelial cell
FB: Fibroblast
SMC: Smooth muscle cell
RBC
RBC
PLT
WBC
EC
EC
EC
EC
SMC
FB
SMC
Monocyte chemoattractive
protein
IL-6
IL-8
PLT
RBC
8
Tunica
Media
SMC
Damaged intimae trigger hemostasis
ry
EC
Tunica
Intima
EC
WBC
EC
SMC
EC
EC
EC
PLT
RBC
PLT
Internal Elastic Lamina
Hypoxia Inj
u
EC
Normal Blood
Flow in Intact Vessels
Injured Endothelial Cells Become Hemostatic
DDAVP
EC
Fritsma GA. Platelet production, structure, and function. In Keohane EM, Smith LJ,
Walenga JM. Rodak’s Hematology Clinical Principles and Applications. 2015, Elsevier
7
Shear Stress
EC
Tunica
Media
SMC
Intact intimae suppress hemostasis:
EC: Endothelial cell
FB: Fibroblast
SMC: Smooth muscle cell
THR
SMC
FB
EC
EC
SMC
FB
Collagen
Trauma to Vessel Exposes
Collagen and Tissue Factor
9
Initiation: vascular
injury exposes
fibroblast (FB)
tissue factor (TF)
P
P
P
P
P
P PP
FB
++
Ca
Tissue Factor “Extrinsic” Pathway
IX
TF
a
VII
XIa
VII
VIIIa
IXa
Xa
Ca++
XI
VIII
P
Ca++
X
10
Va
Propagation on activated
platelet (P) surfaces with
phosphatidyl serine
V
P
Access to tissue factor (TF) on smooth muscle
cells and fibroblasts in injured vessel wall
activates VII. In inflammation, TF appears on
endothelial cells and monocytes.
By Shape:
ote
Pr
Thrombin
as
Prothrombin
Fibrinogen
Coagulation
Fibrin
ed
P
nk
sli lot P P P P
os c
Cr ibrin P P
f
P
P P
P
www.fritsmafactor.com
e
XIIIa
gen
o
Zy m
XIII
Fibroblast
TF
VII
VIIa
X
TF
VIIa binds TF,
activates X
Xa
r
facto
Co
P P
P
12
2
Cell-based Coagulation
Tissue Factor and VIIa Activate IX
of the “Common” Pathway
Fibroblast
VIIa
By Shape:
te
Pro
Zym
oge
VIIa and TF
activate IX
TF
X
n
IXa
Ca++
as
Phospholipid
e
Cofa
ctor
X
VIIIa
PLT Phos
Xa
Ca++
VIII
THR
Fibrinogen
13
Fibrin Polymerization and Crosslinking
E
β-chain
B
B
FPa, FPb
D
D
D
D
E
D
E
Fibrinopeptides A and B
15
P
P
P
P
P
P PP
FB
++
Ca
a
VII
XI
XIa
VII
VIIIa
IXa
Xa
VIII
P
Ca++
Ca++
E
Va
Propagation on activated
platelet (P) surfaces with
phosphatidyl serine
V
P
D
D
E
D
D
D
E
D
Fibrinogen
Fibrin
D
E
D
E
D
E
D
D
D
Crosslinked Fibrin Polymer
Thrombin activates XI
IXa binds VIIIa, platelet
phosphatidyl serine, and
Ca++ to form the “tenase”
complex that activates X
XI
IX
THR
XIa
IXa
VIIIa
Ca++ PLT Phos
Thrombin
XIIIa
Coagulation
D
D
D
E
XIII
Prothrombin
E
D
XIIIa stabilizes fibrin polymer by forming
intermolecular γ-dimers between
neighboring γ-chain glutamine and lysine
E
D
E
Intrinsic
Pathway
IX
TF
X
D
D
D
D
D
XIIIa
B
B
A
D
D
D
E domain
γ-chain
Initiation: vascular
injury exposes
fibroblast (FB)
tissue factor (TF)
E
E
Fibrin Polymer
E
D
THR
D domain
A
Crosslinked
Fibrin
Fibrin
Fibrinogen
THR
A
Thrombin activates XIII,
XIIIa crosslinks fibrin
THR
XIIIa
D
D domain
Common Pathway
V
PRO
Thrombin Cleaves Fibrinogen
α-chain
Va
PLT Phos
XIII
IXa binds VIIIa, platelet
phosphatidyl serine, and Ca++ to
form “tenase,” which activates
factor X
Xa
A
Thrombin activates V,
a cofactor in the
prothrombinase complex
IX
TF
VII
Xa binds Va, platelet
phosphatidylserine, and Ca++ to
form the “prothrombinase”
complex that activates
prothrombin, forming thrombin
ed
P
nk
sli lot P P P P
os c
Cr ibrin P P
f
P
P P
P
www.fritsmafactor.com
P P
P
XIa activates IX
X
Xa
Common pathway
proceeds from Xa
3
Cell-based Coagulation
Vitamin K
In Vitro Contact Activation
XIIa binds HMWK
(Fitzgerald factor) and PK
(Fletcher factor) to activate
factor XI
HMWK
XI
PK
Ca++
-- -
XIIa
NCS
XIa
XII
Negatively charged
particles or surfaces
activate XII
Intrinsic pathway
proceeds from XIa
•  Necessary for normal activity of prothrombin (II)
and factors VII, IX, and X
•  Also necessary for normal activity of control
proteins C, S, and Z
•  Mediates γ-carboxylation of glutamic acid
•  Necessary for Ca++ fixation to phospholipid
•  Affected by oral anticoagulants
19
20
γ-carboxylation of Glutamic Acid
Fibroblast
TF
COOH
γ
β
HOOC
CH2
++
Ca
VIIa
COOH
Xa
CH
Vitamin K
VIIIa
IXa
Va
CH2
CH2
IIa
Simplified
Coagulation
Pathway
α
H2N-CH-COOH
H2N-CH-COOH
Fibrin polymer
Gla
Glu
Crosslinked fibrin
NH2
COOH
21
Procoagulant Concentrations and
Their Plasma Half-lives
Thrombin Properties
Mann KG. Thrombin formation. Chest 2003; 124:4S-10S
XIIIa
II, VII, IX, X,
PC, S, or Z
os
Ph
PLT
12-20 Gla
copies
Neg-charged
surface
PK
XIa
XIIa
HMWK
Platelets
Va
XIa
THR (IIa)
Fibrin polymer
VIIIa
XIIIa
TAFI
Thrombomodulin
www.fritsmafactor.com
23
Factor
Category
Half-life Plasma Hemostatic
Level
Level
Fibrinogen (I)
Substrate
4 days
280 mg/dL
50 mg/dL
Prothrombin (II)
Protease
60 hours
1300 µg/mL
20%
V
Cofactor
16 hours
680 µg/mL
25%
VII
Protease
6 hours
120 µg/mL
20%
VIII
Cofactor
12 hours
0.24 µg/mL
30%
IX
Protease
24 hours
5 µg/mL
30%
X
Protease
30 hours
10 µg/mL
25%
XI
Protease
2-3 days
6 µg/mL
25%
XIII
Transglutaminase
7-10 days
290 µg/mL
2-3%
VWF
Cofactor
30 hours
6 µg/mL
50%
24
4
Cell-based Coagulation
The Platelet Clot or “White” Clot
The Fibrin Clot or “Red” Clot
Platelet Adhesion Properties
Courtesy of Kathy Jacobs, Chronolog, Inc
•  Composed of platelets, fibrin, and RBCs
•  The endpoint of “secondary” hemostasis
•  Complete hemostasis in higher vertebrates
Courtesy of Kathy Jacobs, Chronolog, Inc
•  Composed of platelets and von Willebrand factor
•  The endpoint of “primary” hemostasis
•  Complete hemostasis in invertebrates and lower
vertebrates
A 7 Year-old Girl: Elective Surgery
•  Platelets bind vessel wall via VWF and fibrin
–  Platelet receptors GP Ia/IIa, IV, and VI bind intimal collagen
–  Platelet receptors GP Ib/V/IX and GP IIb/IIIa adhere to
VWF and fibrin
–  GP IIb/IIIa supports platelet aggregation
•  Platelets bind other adhesive proteins:
thrombospondin, fibronectin
•  Fibrin binds platelet interior actin: clot retraction
A healthy 7 year-old girl was scheduled for elective outpatient
surgery. The surgeon ordered a screening platelet count, PT,
and PTT. She had experienced no bleeding.
Results:
Result
RI
Platelet count
237,000/uL 150–400,000/uL
PT
13.5 sec
12.6–14.6 sec
PTT (APTT)
47 sec
25–35 sec
27
What are the Possibilities?
A 7 Year-old Girl: Elective Surgery
Mixing studies were performed to determine the cause for the
prolonged PTT. Results:
Test
PTT patient
PTT control
PTT 1:1 patient/control
2h incubated control
2h incubated PTT 1:1
PTT RI
Result
47 sec
29 sec
32 sec
34 sec
36.5 sec
25–35 sec
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28
•  Lupus anticoagulant inhibitor?
–  No: immediate correction within 10% of control
•  Specific inhibitor?
–  No: 2h correction to within 10% of 2h control
•  Liver disease, vitamin K deficiency, renal?
–  No symptoms, PT normal, liver enzymes normal
•  Inherited single factor deficiency?
29
30
5
Cell-based Coagulation
PT and PTT Test Results
in Inherited Coagulopathies
PT
PTT
Fibroblast
Congenital Single Factor
Deficiency (Hemophilia)
Long
Normal VII
Long
Long
X, V, II, and fibrinogen1
VIII, IX, XI
Normal Long
TF
PT
prolonged by
deficiencies of
“extrinsic” VII, and
“common” X, V,
prothrombin (II),
fibrinogen
Contact factors: XII, prekallikrein, high
MW kininogen2
VIIa
Xa
VIIIa
IXa
Va
IIa
Fibrin polymer
XIIIa
1.  PT and PTT prolonged when fibrinogen is < 100 mg/dL
2.  Contact factor deficiencies affect PTT results, but do not cause bleeding
Neg-charged
surface
PK
XIa
XIIa
HMWK
Crosslinked fibrin
PTT prolonged by
deficiencies of
“Intrinsic” XII, XI, IX,
VIII, and “common” X,
V, prothrombin (II),
fibrinogen
31
A 7 Year-old Girl: Elective Surgery
Factor Assay Results
True or False
1.  Coagulation is triggered by exposure to tissue
factor.
2.  Coagulation is also triggered by the in vivo
activation of factor XII.
3.  Factor VIII deficiency causes bleeding.
4.  Coagulation can occur without platelet
phosphatidylserine.
Intrinsic Pathway Factor Result
Factor XI
123%
Factor XII
37%
PK
97%
HMWK
89%
RI
50–150%
•  Bleeding implications of factor XII deficiency: none
•  Incidence: 3%
33
Antithrombin
Glycosaminoglycan
•  Linear heteropolysaccharide
•  Plasma antithrombin activity is upregulated by
endothelial cell heparan sulfate, a long-chain
glycosaminoglycan
•  Therapeutic heparin upregulates plasma
antithrombin 1000-2000×
•  Antithrombin is a serine protease inhibitor
(SERPIN) that neutralizes thrombin and Xa
35
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34
–  Disaccharide repeating unit
–  Chondroitin sulfate
–  Dermatan sulfate
–  Keratan sulfate
–  Heparan sulfate
–  Hyaluronic acid
–  Heparin
36
6
Cell-based Coagulation
Unfractionated Heparin Binds
Antithrombin to Thrombin
Protease
Binding
Site
AT
Heparin Binding
Site
Active
Protease
Site
IIa
Protease
Binding
Site
AT
Heparin Binding
Site
Heparin Binding
Site
IIa
AT
Unfractionated Heparin Binds
Antithrombin to Xa
AT
Xa
The Protein C Control Pathway
Fibroblast
UFH:AT
UFH:AT
TF
VIIa
VIIIa
Neg-charged
surface
PK
XIa
XIIa
HMWK
IXa
Va
UFH:AT
No Heparin
Binding Site
UFH
IIa
AT
Xa
Xa
Xa
AT
UFH
UFH:AT
Active
Protease
Site
IIa
Heparin: Antithrombin
Control Points
Fibrin polymer
•  Protein C activated by thrombomodulin-bound
thrombin
•  Becomes serine protease specific for Va and VIIIa
•  Forms cell-surface complex with protein S, digests
Va, VIIIa
Fritsma MG, Fritsma GA. Normal
Hemostasis and Coagulation. In Rodak
BF, Fritsma GA, Keohane EM.
Hematology Clinical Principles and
Applications, 4th Edition. 2012, Elsevier
XIIIa
Crosslinked fibrin
40
Protein C Control Pathway
Fibroblast
TF
Va
VIIa
VIIIa
Endothelial Cell
Thrombin
EPCR-1
APC
PC
Xa
Vi
PS
IIa
APC is a serine
protease
40% Free PS
C4b-BP
Bound PS
PS
Va, VIIIa
Vi, VIIIi
TM:
PC:
APC:
PS:
C4b-BP
EPCR-1
Activated factors V and VIII
Inactivated factors V and VIII
Thrombomodulin
Protein C
Activated protein C
Protein S
C4b binding protein
Endothelial protein C receptor
www.fritsmafactor.com
VIIIa
Fibrin polymer
XIIIa
Crosslinked fibrin
41
IXa
Va
APC
VIIIi
APC
TM
Neg-charged
surface
PK
XIa
XIIa
HMWK
Activated Protein C
Control Points
Fritsma MG, Fritsma GA. Normal
Hemostasis and Coagulation. In Rodak
BF, Fritsma GA, Keohane EM.
Hematology Clinical Principles and
Applications, 4th Edition. 2012, Elsevier
7
Cell-based Coagulation
True or False
Fibroblast
TF
TFPI
VIIa
ZPI
Xa
VIIIa
Neg-charged
surface
PK
XIa
XIIa
HMWK
IXa
Va
IIa
Fibrin polymer
XIIIa
Crosslinked fibrin
Tissue Factor Pathway Inhibitor
and Z-dependent Protease Inhibitor
Control Points
Fritsma MG, Fritsma GA. Normal
Hemostasis and Coagulation. In Rodak
BF, Fritsma GA, Keohane EM.
Hematology Clinical Principles and
Applications, 4th Edition. 2012, Elsevier
Virtues of the Plasma
Coagulation System Model
1.  Antithrombin deficiency confers a risk of
thrombosis.
2.  Protein S excess confers a risk of hemorrhage.
3.  Deep vein thrombosis is common in 30-yearolds.
4.  Though thrombin is procoagulant, it activates
protein C on endothelial cells.
44
Limitations of the
Plasma Coagulation System
•  It models coagulation as a series of amplifying proteolytic
reactions
–  Each protease cleaves and activates the subsequent substrate
zymogen in the series
•  It recognizes the participation of platelet anionic phospholipids,
mainly phosphatidylserine
–  Inert although essential assembly site
•  It models the screening tests PT and PTT as corresponding to
the “extrinsic” and “intrinsic” systems
•  If there is a separate tissue factor pathway, why doesn’t VIIa/
TF activate enough X to compensate for a lack of factor VIII
or IX in hemophilia?
•  If VIII or IX deficiency both cause severe bleeding, why is XI
deficiency bleeding mild and variable?
•  Why is no fibrin generated when the platelet count is less
than 10,000/uL?
•  Why does aspirin reduce thrombin formation?
45
46
The Cell-Based Coagulation System
2001-Present
The Answer
“It just got worse”
•  There is no “extrinsic,” “common,” or “intrinsic”
pathway
•  There is no plasma coagulation
•  Coagulation occurs only under the control of cells
Hoffman H, Monroe DM. Coagulation 2006: a modern view of
hemostasis. Hematol Oncol Clin North Am 2007;21:1-11
Hoffman M, Cichon LJH: Practical coagulation for the blood banker. Transfusion
53:1594-1602, 2013.
47
www.fritsmafactor.com
48
8
Cell-based Coagulation
Overlapping Coagulation Phases
Initiation
Amplification
Initiation: Tissue Factor Bearing Cell
•  TF constitutive on fibroblast, smooth muscle cell, or induced
on monocytes or endothelial cells
•  Exposure of TF cleaves VII → VIIa and binds TF/VIIa
•  TF/VIIa cleaves X → Xa; Xa cleaves and binds V → Va
•  Xa/Va cleaves prothrombin (Pro, II) → thrombin (Thr, IIa)
•  TF/VIIa also cleaves IX → IXa
Propagation
–  With no VIII around, IXa cannot function
•  Free initiation proteases are bound by TFPI, ZPI or AT
•  Occurs away from injury site and outside of vessels
Dahlbäck B. Blood coagulation. Lancet 2000; 355: 1627-32.
49
50
Amplification: COAT Platelets
Initiation: TF-bearing Cell
•  Amplification begins at injury
•  Platelets adhere to injury site collagen and VWF
•  Platelets contact thrombin-producing tissue factorbearing cells and become partially activated
•  Called “collagen and thrombin-stimulated” (COAT)
platelets
TF-bearing cell
VII
TF
Va
VIIa
Xa
V
X
PI
TF
TFPI
Pro (II)
Thr (IIa)
Xa
ZPI
AT
IXa
AT
AT
IX
51
52
Amplification: COAT Platelet
Amplification: COAT Platelet
•  Thrombin (IIa) in direct “hand-off” from TF-bearing cells
escapes AT and binds nearby COAT platelets
Tissue factor-bearing fibroblast
delivers IIa, IXa, and Xa
–  Triggers release of VIII/VWF and V from α-granules
–  Cleaves and activates VIII → VIIIa and V → Va
–  Cleaves VIII from VIII/VWF
–  Cleaves and activates XI from plasma and PLT α-granules → XIa
•  IXa from TF-bearing cells binds VIIIa on COAT platelets
•  Xa from TF-bearing cells binds Va on COAT platelets
•  XIa binds COAT platelet membranes
C
AP
VIIIa
VIIIa
IXa
XIa
IX
Thr (IIa)
XI
Xa
Va
Thr (IIa)
Va
C
AP
–  Cleaves and activates IX from plasma/platelets → IXa
53
www.fritsmafactor.com
Thr (IIa)
V
COAT Platelet
VIII/VWF
54
9
Cell-based Coagulation
Propagation: COAT Platelet
Propagation: COAT Platelet
•  COAT platelet continues to be activated by thrombin,
collagen and VWF
•  Tenase and prothrombinase complexes now
assemble on platelet surface
IXa
VIIIa
Xa
XI
–  TF/VIIa and Xa/Va are the extrinsic mechanism
–  XIa and IXa/VIIIa are intrinsic
•  The pathways now act at the platelet surface to
produce high-volume thrombin
•  Fibrin polymerization and stabilization
COAT Platelet
XI
XIa
Va
Thr (IIa)
D
IX
E
D
PRO
X
XIII
XIIIa
D
E
D
D
D
E
D
E
D
E
D
D
D
D
E
D
E
D
E
D
E
D
D
D
55
56
Cell Localization
Cell Localization: Platelets
• 
• 
• 
• 
•  Tissue factor has to be on a cell that supports
prothrombinase activity (Va/Xa)
–  Fibroblasts, smooth muscle cells, also macrophages,
monocytes, and endothelial cells when induced
•  Malignant cells that make TF but don’t support
prothrombinase activity are not as effective
• 
• 
• 
• 
No TF on platelets, so they have to adjoin TF bearing cells
No factor VII or VIIa receptor site on platelets
Thrombin cleaves protease activated receptor (PAR)
COAT activation moves phosphatidylserine to outer leaflet to
support “tenase” and “prothrombinase”
GP Ib/V/IX binds VWF, COAT platelets adhere to injury sites
Glycoprotein IIb/IIIa binds fibrinogen and VWF
Platelet provides surface receptors for VIIIa, Va, IX, X, XI
Subsequent non-COAT platelet layer damps the reaction
57
Virtues of the
Cellular Coagulation System
Coagulation Control: Endothelial Cells
•  Thrombomodulin (TM): binds thrombin and activates
protein C → APC
•  Endothelial protein C receptor (EPCR-1) binds APC to
surface
•  APC binds protein S, inactivates Va and VIIIa
•  Heparan-like glycosaminoglycans activate AT
•  Cell-surface ADPase neutralizes platelet ADP
59
www.fritsmafactor.com
58
•  If there is a separate tissue factor pathway, why can’t the
activation of factor X by VIIa/TF compensate for a lack of
factor VIII or IX in hemophiliacs?
–  Because the activation of X by VIIa/TF occurs on the wrong cell—
the fibroblast
–  Free Xa is inhibited by AT and TFPI—it does not diffuse to a
platelet
•  If VIII or IX deficiency both cause severe bleeding, why is
XI deficiency bleeding variable?
–  Free IXa can transfer to the platelet as AT has less effect
–  Free IXa on platelet bypasses need for factor XI
60
10
Cell-based Coagulation
Thrombosis and Cellular Coagulation
Fibrinolysis: Fibrin Degradation
•  If thrombosis is hemostasis that occurs on
endothelial cells, therapy could target the vulnerable
endothelial cells
•  Aspirin effect on platelets also slows coagulation
•  Thrombocytopenia also slows coagulation
Plasminogen
PAI-1
D
D
61
Kringle Adhesion
D
D
E
TPA:
PAI-1
E
D
TPA:
PAI-1
THR
TAFI
E
D
D
D
D
E
D
E
D
E
D
E
D
D
D
Tissue plasminogen activator
Plasminogen activator inhibitor-1
Thrombin (factor IIa)
Thrombin activatable fibrinolysis inhibitor
•  PAI-1, TPA, and plasmin bind fibrin polymers
through “kringle” structures
•  Plasmin cleaves fibrin at selected lysine and
arginine residues
•  TAFIa cleaves fibrin C-terminal lysines that
plasmin requires for their cofactor activity
D
D
E
D
E
THR
TAFIa
Plasmin
TPA
E
TAFI
Fibrinolysis
Plasmin
TPA
α2-plasmin inhibitor
PAI-1
D
PAI-1
Plasmin
TPA
D
Tissue plasminogen activator
Plasminogen activator inhibitor-1
64
Wound Healing
Fibrinolysis: Fibrin Degradation
D
E
D
E
D
D
D
E
E
D
D
D
D
D
D
E
E
E
D
E
D
D
D
D
Plasmin
D
D
E
D
D
D
D
D
D
E
D
D
E
D
E
D
D
D
D
D
D
E
E
E
D
E
D
D
E
D
D
Y
E
E
D
X
D-dimer and Fibrin Degradation Products
www.fritsmafactor.com
D
E
E
•  Fibrin attaches to platelet actin, clot retracts
•  Neutrophils that first appear are replaced by
macrophages
•  Macrophages secrete vascular endothelial cell growth
factor (VEGF), triggers neovascularization
•  Platelets secrete platelet derived growth factor that
attracts and stimulates fibroblasts and smooth muscle
cells
66
11
Cell-based Coagulation
Thank You For Listening
The End
Questions?
67
www.fritsmafactor.com
68
12