People who need skin
grafts because of burns
or other injuries might someday get lab-grown, bioengineered skin that works
much like real human skin, Swiss researchers report.
This new skin not only has its own blood vessels but also and just as
important – its own lymphatic vessels. The lymph vessels are needed to prevent
the accumulation of fluids that can kill the graft before it has time to become
part of the patient's own skin, the researchers said.
The discovery that lymph vessels can be grown in a laboratory also opens up
"a broad spectrum of possibilities in the field of tissue engineering,
since all organs in the human body – with the exception of the brain and inner
ear – contain lymph vessels," said lead researcher Daniela Marino, from
the Tissue Biology Research Unit at University Children's Hospital Zurich.
Components of real skin
"These data strongly suggest that if an engineered skin graft
containing both blood and lymph vessels would be transplanted on human
patients, fluid formation would be hindered, wound healing would be improved
and regeneration of a near natural skin would be greatly promoted," Marino
The researchers said that until now, bioengineered skin grafts had not
contained much of the components of real skin, including blood and lymphatic
vessels, pigmentation, sweat
glands, nerves and hair
vessels transport nutrients,
oxygen and other essential factors that keep organs alive and functioning.
Lymph vessels remove fluid from the tissue and return it to the bloodstream.
"When skin is wounded, fluid builds up in the damaged tissue,"
Marino said. "If not efficiently removed, it accumulates to form so-called
seromas, which may impair wound closure and skin regeneration."
To create the new skin, Marino's group used human cells from blood and lymph
vessels, placing them in a solution that scattered the cells onto a skin-like
gel. After time in an incubator, the mixture grew into skin grafts.
Trials in humans
The researchers then tested the grafts on rats, and found that the bioengineered
skin turned into near-normal skin. After connecting the graft to the rats' own
lymph system, it collected and drew fluid away from the tissue – just as
normal skin does.
Skin grafts grown this way might find their best use in patients with severe
burns who do not have enough of their own healthy skin available for grafts,
the researchers said.
Experts note, however, that experiments in animals don't always work out
when tested in people. But Marino said she is hopeful that trials in humans are
not too far away.
Not everyone is sure there will be a big role for these types of grafts,
Dr Alfred Culliford, director of plastic, reconstructive and hand surgery at
Staten Island University Hospital in New York City, called the bioengineered tissue
"a technology in search of a purpose".
Helpful in burn patients
"I don't think it will be broadly applicable to many people who need
skin grafts," Culliford said. "It may be helpful in burn patients who
have had a large portion of their body surface burned and don't have enough
healthy skin to transplant."
Culliford said the best grafts for most patients still come from the
patient's own skin. In addition, he said he doesn't believe adding lymph
vessels to a graft is a great advance, since fluid drainage is now done by
methods such as compressing the graft.
But Dr Robert Glatter, an emergency physician and burn expert at Lenox Hill
Hospital in New York City, saw more promise in the technology.
"Although we are still in animal models, in the near term there is a
significant possibility this could remarkably change the way we deal with
non-healing wounds," Glatter said.
A real advance
Non-healing wounds are generally found among people with diabetes or
vascular disease whose own skin doesn't function normally. "They don't
heal well with standard skin grafts," Glatter said.
For her part, Marino said the newer tissue is a real advance.
"Taken together, it is most important to have both blood and lymph
vessels in a bioengineered skin to initiate nutrition soon after
transplantation and to maintain the balance of tissue fluids," she said.
"This long-awaited step in regenerative medicine is now in reach."
The report was published in the journal Science Translational Medicine.