This document discusses the use of skin substitutes in treating burns and bone regeneration through bioengineering approaches. It describes various temporary and permanent skin substitutes derived from cadaver skin, amniotic membrane, or xenografts. Issues with immune rejection and disease transmission are discussed. The use of cultured keratinocytes and fibroblasts seeded onto scaffolds is also summarized. For bone regeneration, the document outlines how mobilized stem cells, growth factors, and a biomimetic scaffold can promote endogenous bone repair by mimicking the natural process. Uncontrolled bone growth in diseases like fibrodyplasia ossificans progressiva is also briefly mentioned.

1. The use of skin substitute in the
treatment of burns and Bone
regeneration and bioengineering.
Dr. Munira Shahbuddin

8. • The idea of covering the exposed burnt tissue
to prevent and control fluid and heat loss.
• Treatment of burn:
1. Mimicking the normal wound healing
environment using dressing
2. Replicating the chemical environment of the
wound using chemokines and growth factors
3. Replacing the damaged skin, utilizing skin
substitutes.

9. Autograph
• The use of split thickness skin graft is to
transfer residual keratinocytes stem cells that
aid with regeneration and faster wound
epithelization.
• This is not ideal and may lead to the formation
of keloid.
• Result obtained with full-thickness skin are
much better aesthetically.

10. • The advantageous of autografts are that they
are immunologically compatible with the
patients.

11. Skin substitute
• The ideal skin substitute should be a safe, easy
to apply, topical material that promotes
healing and leads to good aesthetic and
functional recovery.
• Should have barrier function of actual skin.
• Can be derived from either naturally or
synthetically.

12. Examples of skin substitute
Collagen GAG scaffold for the
regeneration of skin after brain tumor
operation on 54 year old woman
The making of skin substitute – Tissue
engineered skin

13. Temporary skin substitutes
1. Cadaveric skin
- Can be used fresh or from a glycerol preserved
state. Both showed compatible metabolic
activities.
- Glycerol dehydrates the skin and prevent
oxidative and hydrolytic reaction which are
detrimental to the cells.

14. Disadvantageous of cadaveric skins
• Low supply, substandard quality, infection and
immune rejection, glycerolized cadeveric skin
slows the onset of rejection by 5 weeks.
• Removal of antigenic epidermal cells is technically
challenging and not successful to date.
• Although pretreated with antibiotic, certain
bacteria still persist.
• Concern about virus and prion disease
transmission.

16. Decellularized cadaveric skins.
• Eliminates any immune rejection
• The method takes 4 weeks
• Do not eliminate the risks of viral
transmission.

17. 2. Amniotic membrane
- The avascular nature of amnion and its thick
basement membrane containing collagen,
laminin and proteinase inhibitors aid healing of
burn wound.
- More successful than cadaveric skin use at
preserving the excised wound bed of a burn.
- Its complex structure minimizes fluid and
electrolyte loss from the wound bed underneath
and maintain an aerobic environment to
encourage healing.

18. • Disadvantageous
- Risk of bacterial and virus contamination.
- Not suitable for full thickness burns because it
disintegrates before entering reepithelization.
- Silver ions are used with amniotic membrane
for its antimicrobial activities. But this has
been found to inhibit epithelial and fibroblasts
proliferation that may impair wound healing.

19. Xenograft
• Economically and widely available
• Fresh disinfect porcine dermal grafts are used
because they similar to human cadaveric skin
in the result they give to patients.
• Similar to human cadaveric, this can be
decellularized to produce an acellular dermal
matrix as skin substitutes.
• Concern about viral, bacterial and prion
disease transmission.

20. Name and
Manufacturer or investigating group
Incorporated
human cells
Primary
cellular
loading
occur
Cell
source
Scaffold
source
Scaffold
materials
Duration of
cover
Reference
Epidermalsubstitute
Bioseed-S
BioTissue Technologies,
GmbH, Freiburg,
Germany
Cultured
keratinocytes
(subconfluent
cell sheet).
In vitro Auto Allo Fibrin
sealant
Permanent (Shevchenk
o, James et
al. 2010)
Cryoceal
XCELLentis, Gent, Belgium merged
with CellTrans Ltd, Sheffield, U.K.
Cryoreserved
keratinocytes
In vitro Auto Allo Temporary (Shevchenk
o, James et
al. 2010)
Lyphoderm
XCELLentis, Gent, Belgium merged
with CellTrans Ltd, Sheffield, U.K.
Lyophilized
neonatal
keratinocytes
In vitro Auto Allo Temporary (Shevchenk
o, James et
al. 2010)
Epicel
Genzyme Biosurgery,
Cambridge, MA, USA.
Cultured
dermal
keratinocytes
In vitro Auto - - Permanent (Shevchenk
o, James et
al. 2010)
MySkin
CellTrans Ltd. Sheffield, U.K.
Cultured
keratinocytes
(subconfluent
cell sheet).
In vitro Auto Synthetic Silicone
support
layer with
surface
coated with
specific
formulation
.
Permanent (Shevchenk
o, James et
al. 2010)
Commercially available or in development materials for
epidermal/dermal substitute for the treatment of wound

21. Name and
Manufacturer or investigating group
Incorporated
human cells
Primary
cellular
loading occur
Cell
source
Scaffold
source
Scaffold materials Duration of
cover
Reference
Dermalsubstitute
Collagen-GAG-Chitosan dermal
matrix
INSERM, U533, Universite’ Paris 7,
IUH, Paris, France
Cultured
dermal
fibroblasts
In vitro Allo Xeno Bovine collagen 1/
Chondroitin-4/ 6-
sulfate/ chitosan
lyophilized dermal
matrix
Temporary (Shevchenko,
James et al.
2010)
Collagen-GAG
Fibers and Polymers Laboratory,
Massachusetts Institute of
Technology, Bldg. Cambridge, MA.
U.S.A
- In vitro Allo Xeno Bovine collagen/
GAG
Temporary (Yannas, Lee
et al. 1989;
Yannas,
Tzeranis et
al. 2010)
Permacol™
Tissue Science Laboratories Inc.
Andover, MA, U.S.A
- In vitro Auto Xeno Crosslinked
collagen from
porcine
Temporary (MacNeil
2007)
Biodegradable polyurethane
Microfibers,
Department of Materials Science and
Engineering, University of Delaware,
Newark, DE, U.S.A
In vivo - Synt Biodegradable
polyurethane
microfibres
Permanent (Shevchenko,
James et al.
2010)
Silk fibroin and alginate
College of Veterinary Medicine and
School of Agricultural Biotechnology,
Seoul National University, Seoul,
South Korea
- In vivo Xeno + Synth Silk fibroin/
Alginate blended
sponge
Permanent (Shevchenko,
James et al.
2010)

22. Name and
Manufacturer or investigating
group
Incorporat
ed human
cells
Primary cellular
loading occur
Cell
source
Scaffold
source
Scaffold materials Duration of
cover
Reference
Dermalskinconstruct
Alloderm
LifeCell Corporation, Branchburg,
NJ. U.S.A
- In vivo - Allo Human acellular
lyophilized dermis
Temporary (Shevchenko
, James et al.
2010)
Surederm
HANS BIOMED Corporation,
Seoul, Korea
- In vivo - Allo Human acellular
dermis
Temporary (Shevchenko
, James et al.
2010)
Matriderm
Dr. Suwelack Skin and Health
Care, AG, Billerbeck, Germany
- In vivo - Xeno Bovine non
crosslinked
lyophilized dermis,
coated with α-elastin
hydrolysate
Temporary (Shevchenko
, James et al.
2010)
Integra
Integra LifeSciences Corporation,
Plainsboro, NJ. U.S.A.
- In vivo Synthetic
+ Xeno
Silicone, collagen
and glycosamino
glycans
Temporary (Wolter,
Noah et al.
2005)
Tegaderm – nanofibre contstruct
Nanoscience and Nanotech
Initiative, Division of
Bioengineering,
National University of Singapore,
Singapore.
Cultured
dermal
fibroblasts
In vitro Allo Synthetic
+ Xeno
Poly (ε-caprolactone/
gelatine nanofibrous
scaffold electrospun
on polyurethane
dressing
Temporary (Shevchenko
, James et al.
2010)

23. The image shows how keratinocytes are cultured from an initial
skin biopsy into confluent sheet of cells.

24. Cells - issue
• Keratinocytes and fibroblasts are most commonly used
to repopulate scaffolds intended for epidermal and
dermal replacement.
• In order of living cells to be cultured, each cell type is
expanded in its appropriate culture medium.
• Cytokeratin 19 (K19) has proven to be indicator of
proliferative keratinocytes, expressed in stratum
basale. This marker cannot be detected in skin of
human individuals over 2 years of age. May be a
subtype of stem cell, exclusively expressed at very
young age.

25. • Additional with other cells like endothelial
cells may improve healing by promoting
vascularization.
• The use of vascular endothelial growth factor
(VEGF) and fibroblast growth factor (FBF)
increase angiogenesis.

26. Bone regeneration and
Bioengineering

27. Bone repair – going back to the roots
Learning nature’s lesson: providing insight into
bone regeneration.
Preclinical and clinical studies indicate that the use
of MSC for bone reconstruction and repair is indeed
feasible.
MSC can be derived from various sources.
Biomimetic concept: tropic and immune-
modulatory effect of stem cells, scaffold resembling
the natural extracellular matrix and delivered
multiple growth factors: all in orchestrated fashion.

28. Bone remodelling after fracture.
Schematic illustration of tissue regeneration via endogenous regenerative
approaches. MSC secreted growth factors can produce their effect via
auticrine, telecrine and paracrine mechanisms.

30. • Fracture may induce mobilization of endothelial progenitor
cells from the bone marrow to prepheral blood and these
cells themselves can promote both neovascularization and
initiate the healing process in the damaged bone.
• Peripheral blood of fracture patients expressed an increase
in CD34+ and CD 133+, with high level of chemoattractant
BMP and SDF-1.
• This highlight the possibility of circulating osteogenic cells
related to hemapoetic stem cells and plastic adherent stem
cells. (both originated from bone marrow).

31. Fibrodyplasia ossificants progressiva – unstoppable
growth of bone.
Shown the activation of ALK2, in endothelial and
chrondrocytes.
In principle, the presence of these circulating cells
can hold great promise but strategies should be
developed to enhance the migration of cells and
promote natural endogenous repair mechanisms.
Uncontrolled bone growth: Disease??