Transcript Tissue Engineering of the Skin

Tissue Engineering of the Skin
Connor Walsh
The Skin
• The skin is the largest organ in the human
body.
• It consists of about ten percent of our body
mass.
• The skin is composed of three distinct layers:
the epidermis, the dermis, and the
subcutaneous fat, sometimes called the
hypodermis.
Layers of the Skin
Layers of the Skin
• The epidermis is the outermost skin layer and
consists of keratinocytes, rapidly dividing stem
cells, that help generate epidermal cells.
• The second layer, the dermis, consists of
collagen fibers in a gel like state and also
fibroblasts. It helps binds the epidermis so it
conforms to the shape of the body.
• The deepest skin layer, the subcutaneous
layer, consists mainly of fatty tissue.
Keratinocytes and Fibroblasts
Keratinocytes
Fibroblasts
Function of the Skin
• A main function of the external skin layer is to
provide a tough barrier covering the entire
body.
• It provides defense from radiation, disease,
gases, chemicals, and many other destructive
forces.
• However, if the skin is damaged it can lead to
difficult complications.
Burns
• A common problem we see with skin damage are
burns.
• Approximately 2,000,000 burns per year in the
United States require medical attention.
• Of these, about 70,000 require hospitalization,
and 20,000 need referral to a specialized burn
center.
• About 10,000 patients die each year of infections
subsequent to sustaining serious burns
• These burns can lead to embarrassing scarring
and pain for the remainder of the victim’s life.
Burn Classification
Skin Grafting
• In the past, a burn victims
only option for repair was
a method known as a skin
graph.
• This requires doctors to
surgically cut a piece of
unburned skin from your
body and place it on the
burned area.
• This can cause bleeding,
infection, nerve damage,
and in some cases, a
repeat graph is required.
Current Skin Engineering
• Tissue-engineered skin exists as
cells grown in vitro and
subsequently seeded onto a
scaffold or some porous material
which is then placed in vivo at the
site of injury.
• Three categories of skin
substitutes:
– Epidermal Substitutes
– Dermal Substitutes
– Dermo-epidermal Substitutes
Process of Skin Engineering
1. Patient has a skin biopsy
2. The skin is then peeled and
separated into the epidermis
and dermis.
3. Keratinocytes and Fibroblasts
are then isolated from one
another.
4. Transferred into a culture on
top of a scaffold.
5. The final skin is finished after
about 3 to 4 weeks.
Process
IntegraTM
• Most well known design of skin
engineering.
• Consists of two layers:
– Bottom layer of collagen fibers
that create the basis of a scaffold
for the dermal cells
– Top layer of a protective film that
can be removed once the dermal
layer has been established.
• Does not provide any assistance
to epidermal cell rejuvenation.
Epidermal and Dermal Substitutes
• Epidermal substitutes contain only keratinocytes
grown in vitro and can be applied or sprayed onto
the wound site.
• Dermal substitutes try to restore dermal growth
with minimum scarring. Example: IntegraTM
• It is applied to the wound site and the skin
regenerates and grows naturally.
• Both processes take around 3 to 4 weeks to
complete.
Dermo-epidermal Substitutes
• Dermo-epidermal substitutes have
been difficult to create.
• The technique involves taking
keratinocytes and fibroblasts from
the burned patients epidermis and
dermis and adding them to a
collagen substrate.
• Both the dermis and epidermis are
regenerated through one piece of
skin.
Limitations
• The average wait time ranges anywhere from 3 to
12 weeks after the biopsy is taken.
• The cost of the treatment and the amount of
time it takes makes the process cost-inefficient.
• Currently there are few dermo-epidermal
substitutes which require patients with an injured
dermis to require both epidermis and dermis
substitutes.
• Skin grafting remains the most popular treatment
for skin replacement.
Towards the Future
• Skin engineering still has much room to evolve.
• More dermo-epidermal substitutes will be created that
will speed the process and the wait time for the
patient.
• An increase of “off the shelf” dermal and epidermal
substitutes will allow patients quick and easy access to
repairing their burns or wounds.
• A skin that includes sweat glands and hair follicles to
help mimic real skin is also being created.
• In the future, engineered skin will replace skin graphs
as the predominant method for treating skin defects.
References
1.
The Skin. Robert F. Rushmer, Konrad J. K. Buettner, John M. Short and George F. Odland.Science. New Series, Vol.
154, No. 3747 (Oct. 21, 1966), pp. 343-348; Published by: American Association for the Advancement of Science
2.
Brenner, Robert A. Medical Care Guide: Burn Statistics. Law Offices of Robert A. Brenner. 2010
<http://www.burnsurvivor.com/burn_statistics.html>
Tissue engineering of replacement skin: the crossroads of biomaterials, wound healing, embryonic
development, stem cells and regeneration. Anthony D Metcalfe and Mark W.J Ferguson. J R Soc Interface.
2007 June 22; 4(14): 413–437.
Groeber, Florian. Skin tissue engineering - In vivo and in vitro applications. Advanced drug delivery reviews
15 Jan 2011: null. Elsevier. 02 Mar 2011.
Burns, Volume 36, Issue 4, June 2010, Pages 450-460
Sophie Böttcher-Haberzeth, Thomas Biedermann, Ernst Reichmann
Biomaterials, Volume 28, Issue 34, December 2007, Pages 5100-5113
Anthony D. Metcalfe, Mark W.J. Ferguson
Tissue engineering of replacement skin: the crossroads of biomaterials, wound healing, embryonic
development, stem cells and regeneration Anthony D Metcalfe and Mark W.J Ferguson J R Soc Interface.
2007 June 22; 4(14): 413–437
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