13. Platelet Gel- Exam 3 Flashcards
Young, fecund, robust, inactivated platelets are what size
1-3 μm discoids
platelet concentration and life span
Humans: Normally ~ 150,000-300,000/ml of blood
Life span~one week
what do α-granules contain
clotting factors, growth factors, and various other proteins
what do Dense granules contain
ADP, ATP, Serotonin, and Calcium
young VS old platelets [weight/size]
Young platelets are large and heavy (dense)
Old platelets are small and light
Young large platelets aggregate how much faster than older platelets
3-5 x
Young platelets release how much more ATP and ADP than do older platelets
ATP (4-8 x)
ADP (4-6 x)
Old platelets require substantially greater amounts of ____ to be activated than do young platelets
ADP
What are the 7 steps platelets go through- starting with the wound and ending with platelet aggregation
- Wound
- Exposes subendothelial collagen
- Binds von Willebrand Factor
- Platelet adhesion to blood vessel wall via GP IIb/IIIa
- Platelet activation
- Platelet cytoskeleton (via actin and myosin) expands
from a disc to a multi-pseudopodal sticky blob - Platelet aggregation
why do aggregated platelets release serotonin
Vasoconstriction
why do aggregated platelets release ADP
Recruits other platelets to aggregate and degranulate
why do aggregated platelets release thromboxane
Platelet aggregation and PGF release
PDGF: Platelet-Derived Growth Factor=
STRONGLY mitogenic and chemotactic for leukocytes
-By itself PDGF application doubles the rate of collagen
deposition in a wound
TGF-β: Transforming Growth Factor-Beta=
Also strongly mitogenic
-Allows damaged (irradiated, corticosteroid-treated)
tissues to revert to normalized collagen deposition
Attracted neutrophils and macrophages release what?
a host of other healing factors
Cells expressing the CD34 protein are concentrated where?
in the mononuclear layer of platelet concentrate
Cells expressing the CD34 protein are what?
stem cell “markers” and are important for other cells’ adhesion/chemotaxis
Platelet Rich Plasma (PRP)=
“The components of whole blood remaining after the removal of (most of) the red cells”
- The buffy coat (white cells and platelets) extending ??? into the top of the red cell column
- PLUS all of the plasma
Platelet Poor Plasma (PPP)=
“Plasma layer without the buffy coat”
-So…you get lots of fibrinogen & coagulation factors but no cells
Platelet concentrate: Buffy coat =
leukocytes + platelets
Platelet concentrate: Leukocyte=
neutrophils, eosinophils, basophils, macrophages, B- and T-lymphocytes
Platelet Gel (PG)=
Platelet Concentrate with enough fibrinogen (2-4mg/ml) to “set up” when combined with an activator
-Platelets 2-6x over baseline
Platelet Gel ‘activator’
“Activator” = Thrombin (bovine or human), Calcium (usually CaCl₂) or Collagen
How many platelets do you need:
Theory 1) Increase in multiples above baseline
- Typically 2-6 times above baseline
- Evidence suggests >6x actually delays healing…why?
- Theory suggests possible up-regulation of other tissues to “factors” in the presence of thrombocytopenia
How many platelets do you need:
Theory 2) Absolute numeric concentration
-Typically > 1,000,000/μL
Evidence supports platelet gel use in promoting healing in virtually all tissues except?
nervous tissue
what are some platelet gel contraindications
- Severe hypovolemia
- Unstable angina/LM disease
- Heparin therapy
- Post-incisional harvest
- Thrombocytopenia (~
what should you never apply platelet gel to
coronary grafts
To get more volume…what has to happen
you either need more blood initally
lower “Increases Above Baseline
you add more RBCs to the mix
To get more volume…what has to happen
you either need more blood initally
lower “Increases Above Baseline
you add more RBCs to the mix
How many platelets in a “unit” of whole blood?
[formula]
(Platelets/μL) X 1000 X (ml of whole blood)
How many platelets in a “unit” of PRP?
[formula]
(Platelets/μL) X 1000 X (ml of PRP)
What is the percent yield of platelets in PRP?
[formula]
(# platelets in PRP X 100)/(# platelets in whole blood)
Essentially two “fields” of stem cell therapy are?
1) Bone Marrow (“Mesenchymal”) Derived
2) Adipose Derived
Mesenchymal stem cells are generally found in?
bone marrow but can be isolated from circulating blood, cord blood, fallopian tubes, and fetal tissue.
Mesenchymal stem cells have a High capacity for?
High capacity for pluropotentiality
High capacity for self renewal
problems with Mesenchymal stem cells
Stem cells are “few and far between” in the bone marrow
adipose derived stem cells=
> 500 X more stem cells in 1 gram of fat as compared to 1 gram of aspirated bone marrow
–Can be extracted without anesthesia/sedative/tranquilizer
which is better? Mesenchymal or adipose?
Technology for utilizing adipose-derived stem cells is much simpler (and more commercially available)
(Moving away from B.M. towards A.D.)
Stem cells have the ability to “morph”…And they are synergistically attracted/stimulated by what?
activated platelets and the “factors” those platelets produce
adipose stem cell extraction systems do what 4 things
1) Remove the “lipids”
2) Remove the supernatant
3) Concentrate the adipose stem cells
4) Maintain the Stromal Vascular Fraction (SVF) which creates a warm, fuzzy microenvironment for the stem cells and helps promote graft retention
5) +/or allow for the stem cell extract to be mixed at some ratio with platelet concentrate in an aerobic environment
what is the estimated platelet/adipose ratio
1:2-1:10
