Tissue engineering of skin

1. Tissue Engineering of the Skin
Bashir A. Lone

2. 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.

3. Layers of the Skin

4. 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.

5. Keratinocytes and Fibroblasts
Keratinocytes
Fibroblasts

6. 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.

7. 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.

8. Burn Classification

9. Skin Grafting
• In the past, a burn victims
only option for repair was
a method known as a skin
graft.
• 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 graft is required.

10. 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

11. 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.

12. Process

13. 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.

14. 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.

15. 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.

16. 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.

17. 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 grafts as
the predominant method for treating skin defects.

18. Thank You