Skin substitutes

This presentation talks about various skin substitutes and their use in burn care.

1. Skin Substitutes
By-Dr Raghav Shrotriya
Department of Plastic Surgery
KEM Hospital, Mumbai

2. Definition
Skin substitutes are heterogeneous group of wound
coverage materials that aid in wound closure and replace
the functions of the skin, either temporarily or
permanently, depending on the product characteristics.
These substances are alternatives to the standard wound
coverage in circumstances when standard therapies are
not desirable

3. Introduction
The need for supplements to autologous skin grafts has
prompted development and use of wide variety of skin
substitutes as biologic and synthetic wound dressings
Functions:
Permanent wound coverage
Temporary coverage to promote healthy wound bed

4. Ideal Skin Substitutes
little or no antigenicity
tissue compatibility
lack of toxicity, either local or systemic
 permeability to water vapor just like normal skin
impenetrability to microorganisms
rapid and persistent adherence to a wound surface
porosity for ingrowth of fibrovascular tissue from the
wound bed
Able to resist infection

5. Able to prevent water loss
Able to withstand the shear forces
Cost effective
Widely available
Long shelf life and easy to store
Flexible in thickness
Durable with long-term wound stability
Can be conformed to irregular wound surfaces and
Easy to be secured and applied

6. Classification (Kumar P, 2008)
Class I: Temporary impervious dressing materials
a) single layer materials
naturally occurring or biological dressing substitute, e.g. amniotic
membrane, potato peel
synthetic dressing substitute, e.g. synthetic polymer sheet
(Tegaderm®, Opsite®), polymer foam or spray
b) bi-layered tissue engineered materials, e.g. TransCyte®

7. Class II: Single layer durable skin substitutes
Epidermal substitutes, e.g. cultured epithelial autograft (CEA),
Apligraf®
Dermal substuitutes
bovine collagen sheet, e.g. Kollagen®
porcine collagen sheet
bovine dermal matrix, e.g. Matriderm®
human dermal matrix, e.g. Alloderm®

8. Class III: Composite skin substitutes (containing both
dermal and epidermal component)

a) Skin graft
Allograft
Xenograft
b) Tissue engineered skin
Dermal regeneration template, e.g. Integra®
Biobrane®

10. Use of Bioactive Skin Substitutes
Wound cover
Improve wound healing
Control pain
Improve functional and cosmetic outcome
Increase survival

11. Temporary
1.Porcine xenograft
2.Human Allograft
3.Human amnion
4.Biobrane
5.Transcyte

12. Xenografts
Earliest In 1500 BC
Homogenised cryopreserved porcine xenograft
recent modifications to the porcine skin include aldehyde
cross-linking and silver ion impregnation to increase the
antimicrobial properties

13. Advantages:
Low cost
Reduces pain
Decreased fluid loss
Good wound adherence
Disadvantages:
Lack of revascularisation
Lack of transparency

14. Cadaver Allograft
Most common
2 types:
Cryopreserved
Glycerol preserved

15. Uses:
Wound bed preparation
provide growth factors and essential cytokines
creating chemotaxis and proliferation at wound beds.
increase vascularity in the wound bed
promoting angiogenesis with enhanced capillary ingrowth on the wound bed 
Pain free dressings
Sandwich grafting technique
prevents desiccation of the wound bed in the interstices of widely expanded
autografts
reduces bacterial colonisation
autograft is protected from shear

16. Advantages :
Provide biologically active temporary wound cover
Decrease metabolic demands
Provide a ‘test’ to assess whether wound is ready for
autograft
Disadvantages:
Expensive
Risk of disease transmission
Need for further procedure for wound closure

17. Amnion
 thin semi-transparent tissue forming the innermost layer
of the foetal membrane
Advantages:
 maintains low bacteria count
 reduces loss of protein, electrolytes and fluids, decreasing the
risk infection
minimises pain
acceleration of wound healing
good handling properties.

18. Synthetic Skin substitutes
Advantages:
composition and properties of the product can be much more
precisely controlled
avoid complications due to potential disease transmission
Disadvantages:
lack basement membrane
 their architecture do not resemble native skin

19. Biobrane®
 Composed of bilaminated membrane formed by nylon
mesh filled with Type I porcine collagen (dermal analogue)
and covered by a thin membrane of silicon (epidermal
analogue)

20. Indications:
Superficial partial thickness burn wounds
Donor sites
TENS patients
Contraindications:
Full thickness burns
Patial thickness burn with eschar
Chemical or electrical burns

21. Advantages:
Pliability and elasticisity
Confirms to irregular wounds
Good pain control
Less frequent dressing change
Extended shelf life
Transparent dressing for wound monitoring

22. Transcyte®
Temporary
Dermal layer of neonatal fibroblasts on a nylon mesh and
outer layer of synthetic epidermis
Contains :
Collagen type III, V
Fibronectin and tenascin
GAGs
GF : TGF-B1, VEGF, IGF-1

23. Similar to biobrane but with addition of growth factors
from lysed fibroblasts grown in culture

24. Semipermeable to allow fluid and gas exchange
Transparent for monitoring
Used as substitute for cadaveric allograft in full thickness
burns after excision

25. Permanent Skin Substitutes
1.Integra
2.Apligraf
3.Alloderm
4.Dermagraft
5.Orcel
6.Epicel

26. Integra® (Yannas et al, 1980)
Dermal analog made of cross linked bovine collagen-
GAG (chondroitin -6- sulphate) copolymer matrix
Epidermal analog thin silicone elastomer
After dermal analog incorporates (2-3 wks), silicon layer
is removed and replaced by thin SSG or Epicel

28. Advantages:
Regenerated skin is more pliable
Resembles normal skin
Favourable scarring
Provides physiologic wound closure
Disadvantages:
Costly
2 stage procedure with 3-4 week interval

29. Uses:
Scar contracture release
Excision of Giant congenital naevus
Irradiated scalp chronic wound closure
Exposed bone and tendons

30. Apligraf®
Permanent bilayered skin substitute
Dermal layer: Type I bovine collagen and allogenic
keratinocyte seeded with human foetal fibroblasts

31. Advantages:
Readily available
Applied in OPD setting
Disadvantages
Remote risk of disease transmission
Multiple applications
Short shelf life (5 days)
Expensive
Uses:
Diabetic ulcers
Venous stasis ulcers
Epidermolysis Bullosa.

32. Alloderm®
Scar Contracture is inversely related to the amount of
dermis
Treated human allograft with epidermis removed
resulting in intact BM and Collagen and removal of
antigenic Langerhans cells, melanocytes and fibroblasts
Used as dermal implant
Thin epithelial autograft is required

33. Advantages:
Thick dermis limits recontracture
Disadvantages:
Costly
Disease transmission

34. Dermagraft®
A cryopreserved human fibroblast derived dermal
substitute made of bioabsorbable polyglactin mesh
(bioabsorbable scaffold) seeded with allogenic neonatal
fibroblasts
Dermagraft human fibroblasts which secrete growth
factors, cytokine, ECM proteins and GAGs
Formation of neodermis through stimulation of
fibrovascular growth from wound bed and not by direct
re epithelialization from wound perimeter

35. Indications
 chronic wounds and diabetic foot ulcers
to support the take of meshed split-thickness skin grafts on
excised burn wounds

36. OrCel®
Bilayered cellular matrix in which normal human
allogeneic skin cells (epidermal keratinocytes and dermal
fibroblasts) are cultured in two separate layers into a
type I bovine collagen sponge.
Indication:
treatment of chronic wounds
skin graft donor sites
as an overlay dressing on split-thickness skin grafts to improve
function and cosmesis

37. Cultured Epithelial Autografts
Epicel®
Rhinewald and Green (1975)
 The autologous keratinocytes are isolated, cultured and
expanded into sheets over periods of 3–5 weeks. The
technique of suspension in fibrin glue has reduced the
time for clinical use to 2 weeks.
Uses:
Coverage of large TBSA wounds
Coverage of giant congenital naevus wound
Pressure ulcers
Vitiligo

38. Advantages:
 avoids the mesh aspect of split skin autografts
avoids discomfort of donor site after skin harvesting.
Disadvantages:
fragility and difficulty of handling
Shearing and blistering
 unpredictable take rate
 high cost.

42. Conclusion
Skin substitutes have a important role to play in plastic
surgery in complex wound management for cutaneous
continuity
Only a bridge until wound is better suited to accept graft
Prohibitive costs and availability limit the usage to
research settings
Future prospects

43. Thank you