New Dressings, Including
Tissue-Engineered Living Skin
MARCIA RAMOS-E-SILVA, MD, PhD
MARIA CRISTINA RIBEIRO DE CASTRO, MD
n humans, skin corresponds to one-tenth of the
body mass, and damage of a part of this organ has
critical consequences. Trauma, disease, burn or sur-
gery can result in a great difficulty to heal the affected
area. Any significant loss of dermis tends to contract
and distort the skin producing a scar. Unfortunately,
skin cannot just be transplanted like others organs and
requires other methods, such as reconstructive surgery,
or grafting procedure.
Healing by second intention is
a common technique of managing wound, but it has an
unpredictable cosmetic result and often prolongs heal-
ing time by several weeks.
Growing replacement tissues to repair skin was sci-
ence fiction in the past.
The first experience took place
in 1907 when Harrison demonstrated that individual
cells were capable to live outside the body in which
they were grown.
In our time, clonage is a reality.
Different materials or devices, capable of specific
interactions with biologic tissues, were developed to
restore the barrier function while permitting epidermal
regrowth. Some are entirely synthetic; some are combi-
nation of materials, while others are built from biologic
Many different wound dressings and tis-
sue-engineered skin are now available.
Tissue-engineered skin was defined in 1987 by the
National Science Foundation Bioengineering Panel
Meeting, in Washington, DC, as “the application of the
principles and methods of engineering and life sciences
toward the development of biologic substitutes to re-
store, maintain, or improve function.”
At present, there
are no strict distinction between wound dressing and
skin substitutes. Generally, synthetic polymer materials
and synthetics associated to some biologic component
are termed wound dressings, and materials that com-
bine matrix proteins and synthetics polymers and ma-
trix proteins with cells are consider skin substitutes. The
exact definition is very hard in biologic dressings, such
, which are in between wound dressings
and skin substitutes.
The skin is divided in epidermis, dermis, and hypo-
dermis. The first is totally cellular and, although thin,
has a sufficient thickness to provide the vital barrier
function. The dermis right below constitutes the bulk of
the skin. The upper layer of the dermis is based on an
extracellular matrix of predominantly of collagen, with
some elastin and glycosaminoglycans; fibroblasts are
distributed through it, adhering to the collagen fibers
and also to blood and lymph vessel, nerve endings, and
others structures. Fibroblasts are capable of producing
enzymes, such as collagenases and others proteases that
“re-model” the deposited collagen; this is a very impor-
tant process in the latter stages of the wound-healing
process. The hypodermis is the layer located beneath
the dermis, containing a considerable amount of adi-
pose tissue, which provides mechanical and thermal
insulating properties to the skin.
Tissue-engineered skin combines novel materials
with living cells to yield functional tissue equivalents,
such as skin substitutes. They provide a matrix, which
is required for the healing process.
blast in collagen gels or “lattices” produces structures
known as dermal equivalent, which forms the basis for
constructing skin equivalent. A dermal equivalent is
constructed by seeding dermal fibroblasts into a re-
formed, three-dimensional collagen matrix. Layering
keratinocytes on the upper surface of such a structure
produces a skin equivalent. It is a simplified model, but
they represent the first step in skin reconstruction.
Tissue-engineered skin is constructed based on cell bi-
ology of host cells and the variety of signals that control
their behavior. It has two forms: (1) cells are grown in
culture and seeded onto a porous material, from which
bone or skin substitutes are created; (2) an implanted
material induces a specific cell reaction, such as tissue
regeneration in vivo, which may accelerate nerve regen-
eration or induce the formation of new blood vessels.
The ideal tissue engineered skin should have some
essential characteristics: (1) appropriate water flux
(wound dependent); (2) ability to be handled and ap-
plied using standard surgical techniques; (3) action as
bacterial barrier; (4) sterile; (5) appropriate mechanical
From the Sector of Dermatology and Post Graduation Course, HUCFF-
UFRJ and School of Medicine, Federal University of Rio de Janeiro, Rio de
Correspondence to: Marcia Ramos-e-Silva, Rua Sorocaba 464/205,
22271-110-Rio de Janeiro, Brazil.
E-mail address: firstname.lastname@example.org
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