wound healing and tissue repair II - lecture notes - julia Flashcards
what is a wound?
any type of disruption in the integrity of an organ or tissue
what is a scab?
- coagulum that forms over a surface defect
- initial attempt to seal
- will have coagulation proteins, serum proteins, etc.
what is granulation tissue? (where in the body is it found, what does it consist of?)
- early phase of the formation of a scar anywhere in the body except the brain
- composed of very early capillaries, activated fibroblasts, new, watery ECM, lots of leukocytes
what is a scar?
- mature collagen that has become relatively hypovascular
what is a keloid?
situation on the skin where a wound has healed but the formation of collagen never stopped - keeps piling up
what is cicatrix?
scar
what processes does repair by connective tissue (scaring) involve? (list)
- angiogenesis
- migration and proliferation of fibroblasts
- deposition of ECM
- maturation of fibrous tissue (remodeling)
what coagulation factor activities are involved in wound healing?
- hageman factor fragments
- bradykinin
- complement activation
- fibrin clot
what is the effect of hageman factor fragments?
vasopermeability
what is the effect of bradykinin?
- vasodilation
- vasopermeability
- pain
what is the effect of complement activation?
- leukocyte recruitment
- vasopermeability
what is the effect of fibrin clots?
- hemostatic plug
- reseroir of growth factors
- provisional matrix for cell migration
what are the roles of platelets in wound repair? (list)
- adhesion
- aggregation
- mediator release
what is the effect of adhesion of platelets?
plug small leaks in blood vessels
what is the effect of aggregation of platelets?
- plug large leaks in blood vessels
- induce coagulation
what is the effect of mediator release by platelets?
- vasoconstriction
- stimulate additional platelet aggregation
- growth factor release
what growth factors are active in wound healing?
- FGF (fibroblast growth factor)
- PDGF (platelet-derived growth factor)
- TGF-B (transforming growth factor)
- VGEF (vascualar endothelial growth factor)
what is the effect of FGF?
- fibroblast and epidermal cell proliferation
- angiogenesis
what is the effect of PDGF?
- fibroblast chemotaxis, proliferation and contraction
what is the effect of TGF-B?
- fibroblast chemotaxis
- ECM deposition
- protease inhibitor secretion
what is the effect of VGEF?
- vascular permeability
- angiogenesis
what is the role of macrophages in wound repair?
- recruitment and maturation
- phagocytosis and killing of microorganisms
- pahgocytosis of tissue debris
- growth factor release
what is the effect of recruitment and maturation of macrophages in wound healing?
transition from ciruclating monocyte to tissue macrophage
what is the effect of macrophage phagocytosis and killing of microorganisms in wound repair?
wound decontamination
what is the effect of macrophage phagocytosis of tissue debris in wound repair?
wound debridement
what is the effect of macrophage growth factor release in wound repair?
autocrine and paracrine stimulation
what GFs cause monocyte chemotaxis?
- PDGF
- FGF
- TGF-B
what GFs cause fibroblast migration?
- PDGF
- EGF
- FGF
- TFG-B
- TNF
what GFs cause fibroblast proliferation?
- PDGF
- EGF
- FGF
- TNF
what GFs cause angiogenesis?
- VEGF, Ang, FGF
what GFs cause collagen synthesis?
- TGF-B
- PDGF
- TNF
what GFs cause collagenase secretion? what inhibits?
- PDGF
- FGF
- EGF
- TNF
TNF-beta inhibits
what cells are most important at the begining of wound repair? what cells take over?
- for the first few days, leukocytes
- after that, fibroblasts take over
what are the activities of fibroblasts in wound healing? (list)
- growth factor production
- proliferation and migration
- protease release
- ECM production
- dynamic linkage between actin bundles and ECM
- program cell death
what is the effect of GF production by fibroblasts in wound repair?
autocrine and paracrine stimulation
what is the effect of fibroblast proliferation and migration in wound repair?
granulation tissue formation
what is the effect of protease release by fibroblasts in wound repair?
provisional matrix lysis and ECM remodeling
what is the effect of ECM production by fibroblasts in wound repair?
connective tissue formation
what is the effect of dynamic linkage between actin bundles and the ECM by fibroblasts in wound repair?
tissue contraction
what is the effect of fibroblasts on cell death programing in wound repair?
transition from cell-rich granulation tissue to cell-poor scar
what are the roles of epithelial cells in wound repair? (list)
- growth factor production
- migration and proliferation
- protease release
- ECM production
- termial differentiation
what is the effect of GF production by epithelial cells in wound repair?
autocrine and paracrine stimulation
what is the effect of migration and proliferation by epithelial cells in wound repair?
reepithelialization
what is the effect of protease release by epithelial cells in wound repair?
dissection under clot and nonviable tissue - allows scabs to fall off
what is the effect of ECM production by epithelial cells in wound repair?
provisional matrix and basement membrane formation
what is the effect of terminal differentiation by epithelial cells in wound repair?
barrier function reestabilshed
what are the roles of endothelial cells in tissue repair?
- thrombomodulin and syndecan surface expression
- prostacyclin release
- plasminogen activator release
- surface expression of cell adhesion molecules
- metalloproteinase release
- GF production
- migration and proliferation
- ECM production
- tube formation
what is the effect of thrombomodulin and syndecan surface expression by endothelial cells in tissue repair?
limits coagulation
(part of mechanism to prevent thrombosis)
what is the effect of prostacyclin release by endothelial cells in tissue repair?
limits platelet thrombi
(part of mechanisms ot prevent thrombosis in new vessels)
what is the effect of prostacyclin release by endothelial cells in tissue repair?
clot lysis
part of mechanism to prevent thrombosis formation in new vessels
what is the effect of the surface expression of cell adhesion molecules by endothelial cells in tissue repair?
leukocyte diapedesis
what is the effect of metalloproteinase release by endothelial cells in tissue repair?
basement membrane degradation - digests material directly in front of leading endothelial cells - allows new blood vessels to grow into the area
how do endothelial cells help to prevent fomration of thrombosis in new vessels?
- thrombomodulin adn syndecan surface expression
- prostacyclin release
- plasminogen activator release
what is the effect of growth factor production by endothelial cells in tissue repair?
autocrine and paracrine stimulation
what is the effect of migration and proliferation of endothelial cells in tissue repair?
angiogenesis
what is the basic mechanism for scar tissue creation, response to dead tissue, wound healing, and resolution of inflammatory sites?
- neutrophils and macrophages remove debris
- fibroblasts make collagen
- new vessels form
- extracellular matrix matures and is remodelled
what is the difference between the healing by first intention and healing by second intention?
1st: goal is to reduce the amount of scar tissue to the minimum possible - occurs when the wound is small and edges can be rejoined
2nd: when one end of wound can’t be opposed to other end - such as in burn or when a large area of tissue is lost that can’t be pulled together by sutures - get large amount of granulation tissue forming, big scar, simplified or sometimes defective endothelial coverage
what does granulation tissue look like?
- earliest form of scar
- loose watery material in background - ECM (fibrin, fibronectin, collagen)
- lots of inflammatory cells
- many tiny, thin-walled blood vessels
- big blue “angry looking” cells = highly activated fibroblasts

what do fibroblasts look like?
very basophilic and huge
how will granulation tissue and mature scar appear different using a trichrome stain?
- mature collagen stains dark blue/purple
- granulation tissue will barely have any purple
- scar = mostly purple

what would a skin wound in the process of scar formation look like?
- reepithelialized
- area of granulation tissue that’s maturing
- will become a focus of scar
- month - two months old

what will a dermal scar look like when fully mature (histologically)?
- no inflammation
- virtually no blood vessels
- everything linear - organized collagen
- can take months to years

what does heart tissue look like 24 hours after myocardial infarction?
- necrotic myocytes
- vast influx of neutrophils - these are breaking down themselves and degenerating

what does heart tissue look like 3-4 days after an MI?
- neutrophils virtually all gone
- predominant cell type = macrophages
- some fibroblasts too but they’re not in full swing of producing collagen yet
- have a few capillaries

what does heart look like 7 days after an MI?
- still have inflammatory cells and macrophages
- now a lot more background ECM
- prominent fibroblasts - very enlarged
- lots of little capillaries

what does heart tissue look like 4-8 weeks after an MI?
- inflammatory cells virtually all gone
- ECM no longer as watery - beginning to organize, can see cords of collagen
- blood vessels far more defined

what are the systemic factors affecting the success of tissue repair?
- nutrition
- metabolic status
- circulation
- hormones
- genetic makeup
- medical treatment
what are the local factors affecting the success of tissue repair?
- infection
- foriegn bodies
- mechanical factors
- size, location, and type of wound
what are the potential complications/pathological outcomes of tissue damage? (list)
- scar formation and loss of function
- keloid formation
- desmoid (aggresive fibromatosis)
- ulceration
- wound dehiscence (separation)
- scar contraction
what is desmoid?
when fibroblasts don’t stop prolilferating and making collagen - can fill retroperitoneum up with collagen
what is wound dehiscence?
wound is put together and looks like it’s going to heal and then all of a sudden it just opens up on its own
what does keloid look like histologically?
- very dense collagen
- lots of fibroblasts - don’t stop making collagen
- huge ropey collagen
