L6 - Skin substitutes

Question 1

What are the three layers of the skin?

Answer 1

Epidermis, dermis and hypodermis

Question 2

Epidermis

Answer 2

Outermost layer, very thin, protective, no blood vessels - only cells. Keratinocytes, melanocytes, Langerhans cells and Merkel cells. Stratified epithelium - proliferation of cells in the basal layer, differentiation occurs as they move toward the outermost layer.

Question 3

Dermis

Answer 3

Bulk of skin, collagen, elastin, GAGs and fibroblasts. Blood vessels and glands

Question 4

Hypodermis

Answer 4

Network of adipose tissue and collagen. Thermal layer, insulating, shock absorber, fat storage - energy

Question 5

Injury to which layers tend to form scars?

Answer 5

Injury involving dermis and epidermis

Question 6

What types of wounds are seen in the skin?

Answer 6

Epidermal injuries, superficial partial-thickness wounds, deep partial-thickness wounds and full thickness wounds

Question 7

What is an epidermal injury?

Answer 7

Affects only the epidermis. Erythema and minor pain. No surgical treatment or scarring

Question 8

What is a superficial partial-thickness wound?

Answer 8

Epidermis and superficial dermis are affected. Weeping, welts, blisters. Painful - exposure of nerves. Heal spontaneously.

Question 9

What is a deep partial-thickness wound?

Answer 9

Dermal damage, moist appearance, more scarring

Question 10

What is a full thickness wound?

Answer 10

Complete destruction of epidermal regenerative elements. Dry, rigid and leathery. No spontaneous healing.

Question 11

How can major skin injuries currently be treated?

Answer 11

Early excision of dry scab
Wound closure
Skin graft - wound bed needs to be prepared and graft needs to take. Can be allogenic (from cadaver) for temporary protection

Question 12

What is the ideal skin graft?

Answer 12

Readily available, no immune response, cover and protect wound, enhance healing, lessen pain and doesn’t scar

Question 13

How are skin substitutes classified?

Answer 13

Layer to be substituted
Durability
Product origin

Question 14

How are epidermal substitutes created?

Answer 14

Isolation of keratinocytes from skin biopsy - expand in culture - deliver to wound - new layer
Autologous treatment - effective in treating chronic ulcers but sometimes the keratino diff too much - no integrins therefore can’t take

Question 15

What is a dermal substitute?

Answer 15

Mainly acellular but facilitate the process of wound healing. Apply to prepared dermis - substitutes are colonised and vascularised by underlying cells

Question 16

What is Integra?

Answer 16

A dermal substitute
Dermal layer - bovine type 1 collagen and shark chondroitin-6-sulfate
Epidermal layer - Silicone (regulates heat and fluid loss)

Question 17

What is Alloderm?

Answer 17

Decellularised skin preserved with freeze drying

2 step process: apply base/wound healing layer and then epidermal substitute after

Question 18

What is a composite substitute?

Answer 18

Aim to mimic histological structure of normal skin. Allogenic skin is incorp into dermal scaffold.
Allows creation of large batches of products.
Temporary bioactive dressings

Question 19

Apligraf

Answer 19

Bovine type 1 collagen cultured with allogenic male neonatal fibroblasts and keratinocytes = mimics normal skin structure

Question 20

OrCel

Answer 20

Allogeneic fibro and keratino from neonatal foreskin. Fibro seeded in bovine T1 collagen sponge and keratinocytes are placed on top. Cytokines and GF from product promote host cell migration and wound healing

Question 21

What are some current limitations of skin substitutes?

Answer 21

3-12 week wait time after biopsy
Currently only use keratinocytes and fibroblasts
Clinical success but economic failure