Cadaveric Skin
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Using cultured keratinocytes in clinical practice has made it clear that stable
closure of full thickness wounds needs dermis as well as epidermis.
The ideal form of dermis contains living skin cells and is autologous. Dermis is a
complex tissue and cannot be grown in vitro.
No synthetic dermal replacement has been found to equal allograft dermis in closing
wounds. Soluble proteins released by living dermal cells probably contribute to the
dermo-epidermal interaction that improves grafting results.
The closest compromise to autograft containing living cells is fresh or cryopreserved
allograft skin.
Indications
Conventional closure of burns is accomplished by split thickness skin grafting, but
autologous donor sites may be inadequate to cover large burns.
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In this instance allograft skin can be used in two ways:
1.
as temporary cover while available donor sites heal ready for reharvesting of
split thickness skin grafts,
2.
for a more permanent dermis to improve the take of cultured autologous
keratinocyte grafts. This provides the highest clinical take rates for cultured
keratinocyte autografts, as well as good quality, supple skin at long term
follow up.
3.
Increased availability of allograft skin will facilitate early excision of burns
and obviate the need for obtaining skin from living relatives or unrelated
donors.
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The use of allograft skin has been limited to large, full thickness burns; the risk of
virus transmission from grafts containing living cells means that use of living
allograft cannot currently be justified in smaller wounds.
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Considerations
 The ethical issues raised by skin banking relate to
1. donor selection
 Living vs nonliving donors
 In Australia there is a public perception that skin donation involves an
unsavoury retrieval procedure, and there is no real appreciation that donor
skin may be life saving.
 Skin is not included as an organ donation option on donor cards, and some
transplant coordinators seem loathe to suggest skin donation.
2. consent
3. testing
4. allograft retrieval
 skin should be harvested within 18 h post mortem to obtain viable cells
 aseptic retrieval
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The method of skin graft harvest can be made acceptable by electric
dermatome retrieval from the back and posterior thighs, which delivers about
30% of the body surface area.
5. processing
 initial disinfection using a cocktail of antibiotics
6. storage
 After harvesting and just prior to further tissue bank processing, human
cadaver skin grafts exhibit approximately 60% of the metabolic activity found
in fresh skin samples obtained from living surgical donors. If allowed an
overnight (18–24 h) incubation period at 37C, cadaver samples show a
recovery of their metabolic activity to 95%
 When stored in liquid media at 4C, cellular metabolic activity of the cadaver
skin declines steadily, arriving at a measurement below that of cryopreserved
skin in less than five days storage
 Cryopreservation - provides graft material with good cellular viability
comparable to that of fresh skin stored at 4C for four days. Graft performance
of cryopreserved skin can be maintained at a relatively good level for a period
of five years; however, it decreases sharply thereafter
 Glycerolisation - High concentration glycerol dehydrates the skin by osmosis
and diffusion out of the cells and skin matrix, respectively preventing or
limiting the many degradation reactions that can occur within stored tissues
including enzymatic digestion, oxidation (peroxidation) and hydrolytic
reactions, as well as minimizing the detrimental effects of microbial growth
7. distribution.
 The Council of Europe recommends that tissue banking should be carried out
on a non-profit basis.
Problems
 limited supply, variable and occasionally poor quality, inconvenience of harvesting
skin in the mortuary
 immune rejection
 The use of allograft donor skin as a permanent skin replacement in fullthickness injuries is limited by its immunogenic properties.
 Allograft skin grafts routinely incorporate to a full-thickness wound, but they
ultimately are rejected.
 The timing of this rejection is delayed in burn patients due to their
immunosuppression.
 This immune response to allograft skin is directed primarily against the cells of
the epidermis and endothelial and fibroblast cells of the dermis. The noncellular
components of the dermis, consisting primarily of extracellular matrix proteins
and collagen, have been demonstrated to be relatively nonimmunogenic.
 pathogenic microbial organism
 Five percent of harvested cadaveric skin is usually discarded due to positive
cultures
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Methicillin resistant Staphylococcus epidermidis, (MRSE), is the most
predominant organism (22.2%), followed by Gram-negative rods as a group
(18.5%)
Viral transmission
 A single case of HIV transmission by donor skin has been reported
Cryopreservation vs Glycerolisation
 The considerably easier handling and storage of glycerol preserved allograft skin
makes it preferable to cryopreserved allografts however, GPA provides no viable
coverage material and lacks the beneficial effects of integration and vascularization of
viable allogenic grafts.
 One of its main benefits though is the need for less frequent change of the allograft
compared to several years ago due to the effects of glycerol in decreasing antigenicity
of the skin
 GPA is mainly used as a temporary cover on freshly excised wounds or as an overlay
on widely expanded autografts. It is used also to improve the quality of the wound bed
prior to autografting with cultured keratinocyte sheets.
 Cryopreserved skin, however, is still recommended in cases where the integration of a
dermal component as a permanent part of wound closure is desired
 Allograft dermis has been shown to be incorporated over time without rejection (thus
the use of Alloderm)
Australasian Skin Banks
 Donor Tissue Bank of Victoria operates the only TGA licensed skin bank in Australia
 skin retrieved at the Donor Tissue Bank of Victoria –split thickness allograft. The
pieces of skin are only 0.016 inches (0.40mm) thick.
 45% of the total body surface area of the donor can be procured with no visible
disfigurement.
 The age restrictions on skin donation Males & Females - 18 to 70 years.
 After collection, allografts are packaged as individual grafts, then treated with
DMSO, as a cryoprotectant, prior to controlled rate freezing ( at 1°C per minute) and
storage in liquid nitrogen vapour phase (-130ºC to -196ºC) for up to 5 years
 Auckland Skin bank operates under the auspices of the New Zealand Red Cross
Blood Transfusion Service
 However, in this bank the skin grafts are soaked in 15% glycerol as cryoprotectant
prior to controlled rate freezing. The allografts are, however, packaged in material
that allows for long term storage at a maximum temperature of –1400C which
eliminates any possibility of storage in liquid nitrogen. However, ultra low
temperature freezer technology has now improved to the point that freezers are
available for storage down to –1530C.