Wound Healing

Question 1

What is the difference between wound healing in the foetus and the adult?

Answer 1

In the foetus it resembles regeneration

In adult there is scaring and it often results in a functional defecit.

Question 2

What cells are responsible for organisation of new tissues and what other factors are involved in regulation of wound healing?

Answer 2

Resident stromal cells.

The ECM and soluble factors affect/mediate the healing process

Question 3

What are the stages of wound healing?

Answer 3

Coagulation then:

1. Inflammation (48hrs)
2. New tissue formation (granulation tissue)
   
   • Angiogenesis
   • Epithelialisation
   • Fibroplasia
   • Wound contraction
3. Remodelling/Maturation
   
   • Reorganisation of disorganised collage by fibroblasts

Question 4

What are the key cells involved in the inflammatory phase and what is their role?

Answer 4

Neutrophils - phagocytocis
Macrophages - Debridement/matrix turnover
- Coordination (stimulatory factors)
Lymphocytes - Important for early remodelling

Question 5

What do keratinocytes migrate under when healing the skin?

Answer 5

They migrate underneath the fibrin clot.

Question 6

What are the roles of keratinocytes in skin healing?

Answer 6

• ECM production
• Growth factor/Cytokine production
• Angiogenesis (with chemoattractants)
• Release of proteases (fibrin clot and dissolution of non-viable tissue)

Question 7

How does angiogenesis progress in the wound, and what cells are involved?

Answer 7

Endothelial cell buds move towards the wound space along gradients (O2/cytokines). Macrophages and keratinocytes (epithelial cells) provide stimuli. New capillaries also sprout from parent vessles, these are initially leaky so granulation tissue is often oedematous.

Question 8

What cell changes occur to allow wound contraction to occur?

Answer 8

The differentiation of fibroblasts into myofibroblasts - these then express contractile proteins.

Question 9

What is proud flesh?

Answer 9

Exuberant granulation tissue - normal part of wound healing in the horse

Question 10

Why is it important to minimise the inflammatory phase and prolonged tissue healing?

Answer 10

Long term scarring leads to fibrosis and the formation of a permanent scar.

Question 11

What extrinsic factors may affect wound healing?

Answer 11

Infection
Nutrition
Glucocorticoids
Mechanical factors
Poor blood flow
Pathogens

Question 12

List some examples of acute fibrosis?

Answer 12

Burns, hypertrophic scars
Radiation-induced fibrosis
Cardiac scarring following myocardial infarction
Surgical procedures

Question 13

List examples of chronic fibrosis

Answer 13

Major organ fibrosis
Fibroproliferative disease (atheroschlerosis, keloids)
Chrohn’s disease and IBD