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Skin regeneration

Substitute skin with a supply system

08.09.2015
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At the University Children’s Hospital in Zurich a substitute skin has been successfully cultured for the first time, which, along with other cell types, also contains blood and lymph vessels.

Dr. Klaus Duffner | Germany

Although generations of scientists have already tried to reconstruct a natural skin substitute, the results have not been satisfactory. This largest of human organs seemed to be too complex, with its various functional layers and multitude of cell and tissue types, all of which have to be brought together in artificial skin to form a functional unit.

 

Juvenile skin: a special problem

As long ago as the 1970s, doctors in Boston, USA, attempted to develop a new skin from bovine skin, collagen and shark cartilage. But the powerful defense mechanism of the human immune system meant that all these attempts came to nothing. By the end of the 1980s, scientists were able to culture certain skin cells, although they were still very far from achieving a true skin substitute.

Until now burn victims have received mostly endogenous skin transplants. This is disadvantageous in particular for small children for whom only limited donor surfaces are available. Moreover, the transplants can cause new wounds and disfiguring scars. For children there is another serious problem, as the scar tissue will not keep pace with the body’s future growth. On the contrary, scars tend to contract over time, which can lead to restrictions in movement or physical distortions that mean many stressful subsequent operations could be necessary.

 

Vessels to supply the skin

To date, skin substitutes have contained no blood or lymph vessels, no pigmentation, no sweat glands or hair follicles, and no nerves. Due to the lack of a vessel system, which in natural skin is responsible for supplying oxygen and nutrients as well as removing excess water, there is an immediate oxygen and nutrient deficiency in the critical, initial healing phase, which clearly reduces the artificial skin’s chances of survival.

But now for the first time, scientists working with Ernst Reichmann, Martin Meuli and Clemens Schiestl at the University Children’s Hospital in Zurich have succeeded in creating a double- layer artificial human skin consisting of hypodermal cells (fibroblasts), epidermal cells (keratinocytes), melanocytes and the endothelial cells of blood and lymph vessels. In these trials, skin biopsies one to two centimeters in size are divided into layers and then broken down by enzymes into individual cell types. The cells are then placed in special nutrient media to allow them to multiply. The remarkable thing about the artificial skin is that the epithelial cells from the blood and lymph capillaries reform themselves spontaneously into the two vessel types on a jelly-like carrier matrix. These tiny capillaries have all the characteristics of their natural counterparts and are fully functional. The new sections of skin are 7×7 cm square and take about three weeks to grow before they can be transplanted.


It has been a long road

Over the last decade and a half, it has taken a huge technical effort and enormous financial outlay for the 15-person team to reach this stage. It took five years alone to develop a suitable carrier substance for culturing skin cells. And it was this special matrix that paved the way for the creation of real skin transplants. The recently developed laboratory-grown skin with its own supply capillaries is being tested in a clinical trial at the University Children’s Hospital in Zurich; and, according to the lead researcher, Ernst Reichmann, it is the best in clinical use anywhere in the world.

Dr. Klaus Duffner

Dr. Klaus Duffner | Germany

Scientific Journalist
Medizin & Wissen Freiburg

References
  1. Kemp AM, et al.: Arch Dis Child (online) 3 February 2014

Photo Header: Universitätskinderspital Zürich / Marc Latzel

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