Tissue Renewal, Repair, and Regeneration Flashcards
Lecture 33 - Exam 4
Describe tissue regeneration
Replacement of injured tissue with cells of the same type & function
Describe tissue repair
Occurs when extent or nature of damage cannot be revered by regeneration alone
Differentiate tissue regeneration and tissue repair
Tissue regeneration:
- Injured tissue replaced by OG cell type
- organ functions the same
- no scarring
Tissue repair:
- Injured tissue replaced by fibroblasts
- Organ does not function the same
- Causes scarring
List the 4 stages of healing after tissue injury
Hemostasis
Inflammation
Proliferation
Remodeling
What is the goal of hemostasis?
to stop bleeding & create the scaffold for migrating cells
Describe hemostasis
- Occurs in minutes
- Results in local vasoconstriction and activation of platelets and clotting factors to form a fibrin clot
- This creates the scaffold for migrating cells
What is the goal of inflammation?
to kill bacteria & clean the wound on the inside
Describe inflammation
- Occurs in hours
- Driven by platelet-derived mediators, bacteria, and secreted chemoattractants
What is the goal of proliferation?
to replace lost/injured tissue
Describe proliferation
- Occurs in days
- Mediated by macrophage and fibroblast-derived growth factors
-> Proliferate the cell types that have been lost
-> Endothelial cells for skin wounds
What is the goal of remodeling?
to restore the tensile strength of tissue
-> “framing” of new tissue
Describe remodeling
- Occurs in weeks to months
- Transition from type III to Type I collagen
- Restores tensile strength of tissue
What does complete injury healing require?
BOTH proliferation & remodeling
List the determinants of regeneration versus repair after tissue injury
- nature of cells injured
- extent of injury
- presence of ongoing inflammation
- underlying disease
Why does the nature of cells injured determine regeneration versus repair after tissue injury?
some cells have marginal renewal capacity
Why does the extent of injury determine regeneration versus repair after tissue injury?
the magnitude of injury may exceed regeneration capacity
Why does the presence or absence of ongoing inflammation determine regeneration versus repair after tissue injury?
Continued release of inflammatory mediators may disrupt balance toward repair
-> Can be due to concurrent infection or other factors
Why does underlying disease determine regeneration versus repair after tissue injury?
Underlying disease(s) may impair proliferative response or remodeling
(example = diabetes)
State the common outcome of various signal transduction pathways of growth factors
Growth factors interact with a variety of surface receptors & activate transcription factors
-> Causes cell proliferation
Name ONE common growth factor
Epidermal Growth Factor (EGF)
Name source(s) of epidermal growth factor
Activated macrophages, keratinocytes, and many other cells
Name function(s) of epidermal growth factor
- Mitogenic for keratinocytes and fibroblasts
- Simulates keratinocyte migration & granulation tissue formation
Describe the two forms of extracellular matrix (ECM)
There are two forms, located in the Basement Membrane & Interstitial Matrix, respectively
List the key components of ECM located in the basement membrane
Type 4 collagen
Laminin
Proteoglycan
List the key components of ECM located in the interstitial matrix
Fibrillar collagens
Elastin
Proteoglycan & hyaluronan
Name a difference between the ECM located in the basement membrane & the ECM located in the interstitial matrix
- Interstitial matrix needs to have more give / move / flexibility than basement membrane
- Basement is more structural
What is an important molecule for the ECM
INTEGRIN !!
List the 3 key growth factors that regulate fibrosis
PDGF (platelet-derived growth factor)
TGF-beta (transforming growth factor)
FGF-2 (fibroblast growth factor)
Describe the result of PDGF (platelet-derived growth factor
Migration & proliferation of fibroblasts smooth muscle cells & macrophages
Describe the result of TGF-beta (transforming growth factor)
- Potent fibrinogenic factor that stimulates collagen, fibronectin and proteoglycan synthesis
- Inhibits collagen degradation
- Inhibits lymphocyte proliferation
- Has anti-inflammatory effect
Describe the result of FGF-2 (fibroblast growth factor)
- Stimulates proliferation of endothelial cells
- Promotes migration of macrophages and fibroblasts to damaged areas
