Regeneration and Repair

Question 1

What is regeneration?

Answer 1

Replacing lost tissue with fresh tissue of the same kind

Question 2

What is repair?

Answer 2

Replacing lost tissue with scar tissue

Question 3

How does regeneration occur?

Answer 3

Damage causes PAMPs to enter tissues
PAMPS interact with TLRs on macrophages which induce COX2 and PGE2
PGE2 stimulates epithelial regeneration and stimulates the release of IL22
IL22 induces proliferation

Question 4

What are the four steps of repair?

Answer 4

Haemostasis
Inflammation
Proliferation
Re-epithelialisation

Question 5

What is haemostasis?

Answer 5

Platelets convert fibronogen to fibrin

Fibrin cross links with ECM proteins to form insoluble plug

Question 6

What is inflammation?

Answer 6

Neutrophils and macrophages enter wound site where they remove microbes and release pro-inflam cytokines

Question 7

What happens during proliferation?

Answer 7

• Development of granulation tissue
• Macrophages release VEGF to induce angiogenesis
• Endothelial cells migrate, proliferate and differentiate
• Fibroblasts lay down collagen which pull together to close the wound

Question 8

What is re-epithelialisation?

Answer 8

EGF induces epithelial cells surrounding a wound to undergo epithelial-to-mesenchymal transition (EMT)

Question 9

What is the EMT?

Answer 9

Epithelial cells lose polarity
Migrate over wound and degrade the clot
Cover the surface and assume epithelial form again

Question 10

What is remodelling?

Answer 10

Collagen III to collagen I which is stronger