Mechanisms of scarring in the skin Flashcards
What are the 3 layers of the skin?
Epidermis
Dermis
Hypodermis
What is the epidermis covered with?
Epithelial cells called keratocytes
What is the dermis involved with?
Scarring
Contains fibroblasts important for remodelling
What does the skin act like?
Protective barrier to the environment
Loss of integrity is associated with human diseases
Examples of acute fibrosis
Burns
Hypertrophic scars
Surgical procedures
Examples of chronic fibrosis
Systemic sclerosis
What is a keloid?
Overgrowth of scar tissue
What are the three stages of wound healing?
Inflammation
New tissue formation
Remodelling
Describe inflammation
Process that happens within 0-48 h after tissue damage
Wound = ischaemic environment
Bacteria, neutrophils and platelets are abundant in wound
Describe new tissue formation
Process that happens within 2-10 days after tissue damage
Scab is formed on the surface of the wound
Most cells have migrated from the wound
New blood vessels populate the area
Migration of epithelial cells observed under the scab
Describe remodelling
Happens up to 1 year or more after damage to the tissue
Disorganized collagen is laid down
Wound is contracted near the surface
Widest portion = deepest, higher that surrounding surface
Does not contain normal skin appendages (follicles or ducts)
Why does blood go to site of injury?
Damage to the blood vessels
More blood to the wound site due to increased vasodilation and permeability
What cytokines and GF do platelets release?
PDGF - platelet derived growth factor
TGFb - transforming growth factor beta
IGF - insulin growth factor
What is inflammation characterised by?
Migration of leukocytes into the wound site
What do neutrophils do at the wound site?
Phagocytosis
What do monocytes/macrophages do at the wound site?
Matrix turnover
Major source of stimulatory signals
What do lymphocytes do at the wound site?
Recruited later
Important in early remodelling
What is re-epithelization?
Singlel layer of keratocytes migrate from the wound edges under the fibrin clot
Move across to resurface the wound area
Differentiate to form new dermis
What molecules aids re-epithelization?
EGF
MMPs
What is EGF involved with in re-epithelization?
Keratocyte migration
Fibroblast proliferation
Differentiation
What is angiogenesis?
Formation of new blood vessels
How do new blood vessels grow during angiogenesis?
Along gradients of VEGF, bFGF and TNFa
What does bFGF stanf for?
Basic fibroblast growth factors
Which cells are angiogenic stimuli?
Macrophages and keratocytes
What are granulation tissues?
New connective tissue that forms on surfaces of a wound during the healing process
Established within 2-3 days post-injury
First appears beneath scab
What influence fibroblasts?
Growth factors and cytokines
VEGF, PDGF and TGFb
Describe the steps of fibroplasia
Fibroblasts migrate into the wound site (3-5 days)
Regulates matrix homeostasis
Synthesise and deposit ECM
Differentiate into myofibroblasts and express contractile proteins
What is the dominant cell type at the wound edge?
Fibroblasts
What is a major cell type in tissue remodelling?
Fibroblasts
