Mechanisms of scarring in the skin

Question 1

What are the 3 layers of the skin?

Answer 1

Epidermis

Dermis

Hypodermis

Question 2

What is the epidermis covered with?

Answer 2

Epithelial cells called keratocytes

Question 3

What is the dermis involved with?

Answer 3

Scarring

Contains fibroblasts important for remodelling

Question 4

What does the skin act like?

Answer 4

Protective barrier to the environment

Loss of integrity is associated with human diseases

Question 5

Examples of acute fibrosis

Answer 5

Burns

Hypertrophic scars

Surgical procedures

Question 6

Examples of chronic fibrosis

Answer 6

Systemic sclerosis

Question 7

What is a keloid?

Answer 7

Overgrowth of scar tissue

Question 8

What are the three stages of wound healing?

Answer 8

Inflammation

New tissue formation

Remodelling

Question 9

Describe inflammation

Answer 9

Process that happens within 0-48 h after tissue damage

Wound = ischaemic environment

Bacteria, neutrophils and platelets are abundant in wound

Question 10

Describe new tissue formation

Answer 10

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

Question 11

Describe remodelling

Answer 11

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)

Question 12

Why does blood go to site of injury?

Answer 12

Damage to the blood vessels

More blood to the wound site due to increased vasodilation and permeability

Question 13

What cytokines and GF do platelets release?

Answer 13

PDGF - platelet derived growth factor

TGFb - transforming growth factor beta

IGF - insulin growth factor

Question 14

What is inflammation characterised by?

Answer 14

Migration of leukocytes into the wound site

Question 15

What do neutrophils do at the wound site?

Answer 15

Phagocytosis

Question 16

What do monocytes/macrophages do at the wound site?

Answer 16

Matrix turnover

Major source of stimulatory signals

Question 17

What do lymphocytes do at the wound site?

Answer 17

Recruited later

Important in early remodelling

Question 18

What is re-epithelization?

Answer 18

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

Question 19

What molecules aids re-epithelization?

Answer 19

EGF

MMPs

Question 20

What is EGF involved with in re-epithelization?

Answer 20

Keratocyte migration

Fibroblast proliferation

Differentiation

Question 21

What is angiogenesis?

Answer 21

Formation of new blood vessels

Question 22

How do new blood vessels grow during angiogenesis?

Answer 22

Along gradients of VEGF, bFGF and TNFa

Question 23

What does bFGF stanf for?

Answer 23

Basic fibroblast growth factors

Question 24

Which cells are angiogenic stimuli?

Answer 24

Macrophages and keratocytes

Question 25

What are granulation tissues?

Answer 25

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

Question 26

What influence fibroblasts?

Answer 26

Growth factors and cytokines

VEGF, PDGF and TGFb

Question 27

Describe the steps of fibroplasia

Answer 27

Fibroblasts migrate into the wound site (3-5 days)

Regulates matrix homeostasis

Synthesise and deposit ECM

Differentiate into myofibroblasts and express contractile proteins

Question 28

What is the dominant cell type at the wound edge?

Answer 28

Fibroblasts

Question 29

What is a major cell type in tissue remodelling?

Answer 29

Fibroblasts