Wound Healing (Dong NAVDF) Flashcards
Wound HEALING vs wound REPAIR
Healing = regeneration. Back to OG. Keratinocytes + endothelial cells
Repair = scarring. Compromised function. Fibroblasts
4 phases of wound healing
1) Hemostasis/coagulation
2) Inflammation (neutrophils, then macs)
3) Repair/granulation phase
4) Remodeling/scar formation
Order of cells involved in wound healing (plt, mac, fibro, neut)
1) PLATELETS ARE FIRST
2) Neutrophils
3) Macrophages
4) Fibrocytes
Which are the FIRST cells in wound healing
Platelets
What allows platelets to bind to each other
Thromboxane
What mediates linkage of platelets with exposed collagen
von wilibrand factor
What marks the END of the coagulation phase
Fibrin clot
Factors of intrinsic coagulation cascade
Factors 11, 9, 8
Not $12, but $11.98
Factors of common coagulation cascade
Factors 10, 1 (aka fibrinogen)
“Small change = $10, $1”
Factors of the extrinsic cascade
Factor 7
Uses tissue factor to convert to factor 1, aka fibrinogen
What mediates conversion of fibrinogen to fibrin
Thrombin
What do damaged cells release to initiate hemostasis
Histamine
Serotonin
Catecholamines
3 “stages” platelets go through during hemostasis
1) Aggregation
2) Platelet plug
3) Fibrin clot
What happens to the blood vessels during hemostasis? (Vasoconstriction vs vasodilation)
Initially: Vasoconstriction to stop bleeding
Later: Vasodilation to recruit WBC
Platelet activation pathway
1) Tissue injury
2) Exposed collagen recruits platelets (VWB F)
2) Coagulation cascade –> fibrinogen to fibrin via thrombin
3) Quiet platelet becomes activated via exposure to collagen, thrombin, ADP, TXA2
4) Active platelet releases DENSE granules (ADP, ATP, Serotonin) and TXA2 to activate more platelets
4) Active platelet releases ALPHA granules (fibrinogen, fibronectin, PDGF, P-selectin) to attract more neutrophils, macrophages
5) Platelets release stores of TGF-B, which induces fibrocyte activity, recruits more neut/mac
Contents of Dense Granules (Platelets)
1) Serotonin
2) ADP
3) ATP
Induce aggregation of platelets
*Construction and adherence
Contents of Alpha Granules (Platelets)
1) Fibrinogen
2) Fibronectin
3) PDGF
4) P-selectin
*Fibrin clot factors
*Chemokines for neut/mac/fibroblasts
More important thing STORED in platelets, functions
TGF B
Activates neut/mac
Stimulates fibroblasts to myofibroblasts
Cells that stores TGF B
Platelets
Factors involved in LYSIS of fibrin clot (4)
1) Plasminogen activator (initiates lysis)
2) Antithrombin III
3) Protein C (factor 5, 8)
4) Prostacyclin C (limit platelet aggregation)
Timeframe for neutrophils to come to wound
Minutes to 72hr
Adhesion molecules involved in neutrophils ROLLING
Selectins
Which Selectins on which cell types?
P selectin- platelets
E selectins - endothelial cell
L selectin- leukocytes
Adhesion molecules involved in neutrophil ADHESION/activation
Integrins (ICAM, VCAM)
hold neutrophils TIGHTLY
What binds to ICAM on endothelial cells
LFA-1 on neutrophil
What binds to VCAM on endothelial cells
VLA on neutrophil
Which adhesion molecules allow diapedesis? (3)
1) PECAM1
2) JAM-1 (tight junctions)
3) VE-cadherin (adherens junctions)
When do macrophages enter wound healing site?
24-48hr
Which TYPE of macrophage is involved in wound healing?
M2
What are M1 macrophages
Phagocytize bacteria + neuts, induce inflammation, scavenge debris
Stimulated by TNF alpha
TNFalpha will induce which TYPE of macrophage
M1
What are M2 macrophages
Repair, help with wound healing. Suppress immune system
Stimualted by TGF Beta
TGF B will induce which TYPE of macrophage
M2
Time frame of REPAIR phase of wound healing
2-10d
4 “steps” of Repair Phase
1) Granulation tissue formation (3-4d)
2) Fibroplasia, wound contraction (triggered by hypoxia. Fibroblasts respond to TGF-B)
3) Angiogenesis
4) Re-epithelialization
What stimulates fibroblasts to turn into myofibroblasts for wound contracture
TGF B
PDGF
Increases collagen integrin receptor alpha-2 expression
Type of Collagen INITIALLY in wound healing, granulation tissue
Collagen 3, less strong
Type of Collagen in MATURE wound healing, remodeling phase
Collagen 1, stronger
Type of collagen in vessels and hypertrophic scars
Collagen 5
Most abundant type of collagen in basement membrane
Collagen 4
When does wound contraction peak?
2 weeks
What type of collagen is present in scar tissue
Collagen 1
What type of collagen is present in granulation tissue
Collagen 3
Which 2 growth factors stimulation wound contracture
1) PDGF (induce fibroblast to myofibroblast)
2) TGF-B1 (stim fibroblast contraction, myofibroblast differentiation, production of HA and RHAMM)
What is the receptor for HA
RHAMM
What is the function of GAGs in wound healing
Moist environment
What is the fastest and most abundant GAG in wound healing
HA
Where in cells is HA synthesized
Plasma membrane
When does angiogenesis start after wounding
Day 2
What stimulates angiogenesis (4)
1) Macrophage-released cytokines
2) Decreased O2
3) Lactic acid
4) Growth factors (VEGF, bFGF)
What are the 2 growth factors that stimulate angiogenesis
VEGF
bFGF (basic fibroblast GF)
Where do keratinocytes for re-epithelialization come from?
*Neighboring keratinocytes
*Hair follicle stem cells (bulge)
*Sebaceous glands
*Claws
If there is a full thickness wound, what to keratinocytes NEED to migrate over?
Granulation tissue
How do keratinocytes re-epithelialize with partial thickness wound?
Leap frog
What are lamellipodia
How keratinocytes migrate; little projections
Process of lamellipodia migration
1) Focal adhesion
2) Extension –> forms lamellipodia
3) Adhesion –> new focal adhesion at tip of lamellipodia
4) Translocation –> Contraction, cell body moves to the new focal adhesion
5) De-adhesion –> lets go of old focal adhesion
Stimulation of lamellipodia formation
Low Ca2+
High Mg2+
What are keratinocytes able to migrate over?
1) COL 1, 3, 5
2) Fibronectin
3) Fibrin
4) Tenascin
5) Vitronectin
Can keratinocytes cross the BMZ directly?
NO.
MMP degrades the BMZ, so keratinocytes can reach it once GRANULATION tissue is formed
What is “contact inhibition”
When keratinocytes reach each other, they know to stop migration.
What is the final strength of the scar compared to original, healthy skin
70% strength
What signal helps with remodeling and scar formation
TGF-B
Which species has delayed collagen synthesis
Cats
Forms day 19. “pseudo-healing”. Indolent pocket wounds.
Where does granulation tissue begin in cats
Periphery of wound
Which species has an early inflammatory response
Dogs
Where does granulation tissue begin in dogs
Center of the wound
Day 7.5
More direct cutaneous vessels
Which species has weak/prolonged inflammation phase
Horses
Which species has exuberant granulation tissue
Horse –> proud flesh
Which disease in horses is equivalent to keloids in people
Proud flesh
-Increased TGF beta
-Mast cell hyperplasia
T or F: Proud flesh can invade healthy skin
T
Which scar is characterized by NO myofibroblasts
Proud flesh
Which scar is characterized by ABUNDANT myofibroblasts
Hypertrophic scars
Noninvasive
Widely spaced collagen
Acronym to assess complications in wound healing= TIME. What does this mean?
TIME
T= nonviable tissue
I = inflammation, infection. Inflammation phase should be done in 3d, so if persistent, check for infection
M= moisture
E= epithelialization
Which growth factor is overexpressed in proud flesh. Which cell is hyperplastic in proud flesh?
TGF-B1
Mast cell hyperplasia
What is the difference between a wound DRESSING and wound BANDAGE
BANDAGE: Control swelling, immobilization
3 Layers
1) Dressing
2) Absorb deleterious factors
3) Hold layers together
DRESSING: Cover + protection
*Absorb excess exudate
*Stimulate repair (non-antigenic, not too moist, occludes dead space)
In which phase of wound healing is honey a good dressing?
Inflammatory + Repair phase
Functions of honey dressing
-Debridement
-Hyperosmotic effects
* -Dehydrates microorganisms + Manuka factor (uMF)
* -Reduces tissue edema
-Stimulates granulation tissue
Functions of granulated sugar
*Hyperosmotic effects
Inferior option:
No antiinflammatory /wound healing effects
Needs to be 1 cm thick
Painful
Function of fish skin (tilapia, cod)
-Excellent skin adherence
-Induces growth factors (EpidermalGF, FGF)
-Antimicrobial activity
-OFA 3: bacterial barrier, pain modulating
Function of negative pressure wound therapy
-Debridement
-Aids in contraction
-Increased perfusion
-Decreased edema
-Removes detrimental cytokines
Contraindications for negative pressure wound therapy
-Exsanguination
-Neoplasia
-Necrotic tissue/eschar
Benefits of HBOT (3)
-Hyper-oxygenation
-Leukocyte oxidative killing capacity (Mac ROS)
-Synergistic with antibiotics/antifungals
Which medications are synergistic with HBOT (4)
1) Fluoroquinolones
2) Aminoglycosides
3) Beta-lactams
4) Amphotericin B
Contraindications for HBOT (3)
-Pneumothorax
-Seizures, uncontrolled
-Unconscious patient, coma
Effect of serotonin and thromboxane A2 from platelet dense granules
Vasoconstriction
Amplify platelet activation/recruitment
Effect of Fibrinogen, vWF, factor V from platelet alpha granules
Stimulate more platelet aggregation –> platelet plug
Where in platelets are PDGF, TGF-B, VEGF made/stored?
Alpha granules
Which phase of wound healing would you expect to see exudate (septic or nonseptic)
Inflammatory phase
(neutrophils getting eaten up by macs)
Predominant cell type in repair phase
1) M2
2) Fibroblasts
3) Endothelial cells
4) Keratinocytes
**Marked increased in fibro, endo, KC during “proliferation” phase
What do fibroblasts bind to, to make scar?
Fibronectin of provisional ECM
Structural proteins of scar
Collagen, elastin
Adhesive proteins of scar
Fibronectin
Ground substance in scar
Hyaluron (HA), Proteoglycans (PG)
Which cell types of repair phase secrete proteases?
All of them (M2, fibloblasts, KC, endothelial cells)
Members of MMP family (3)
-Collagenases
-Gelatinases
-Stromelysins
What breaks down old blood vessels?
MMP
Heparinase
From endothelial cells
Inhibitors of angiogenesis (3)
Angiostatin
Endostatin
Antithrombin III
Risk factors for poor wound healing (6)
1) Infection
2) Medications
3) Comorbidities (age, endocrine, liver/kidney, neoplasia, immune-med)
4) Nutrition (need Glu, protein, Mg, Vit A)
5) Location
6) Radiation tx
How do wounds heal for rats/mice
Contraction
How do wounds heal for pigs?
Re-epithelialization
Since skin is tightly adhered to underlying structures, limited ability for contracture
Where on body is proud flesh most common
Distal limb wounds
Who has more wound contraction: horses or ponies?
Ponies –> less proud flesh than horses
Collagen dressing
-Hydrophilic: maintain moist wound environment
-Scaffold for fibroblasts
Platelet-derived products dressing
*Enhance fibroblast proliferation
*accelerate epithelial differentiation
Indication: decubital ulcers in dogs, horses
Mesenchymal stem cell dressing
*Make many SC lines
*Anti-inflammatory, pain modulating
*Immunmodulation
Bioelectric dressing
*Mimics physiologic currents at wound edge across wound surface
*Use AFTER inflammatory phase
*Antimicrobial, prevent biofilm
*Moist environment
*Increases epithelialization
