MED: Development in Tissue Engineering

Date: Sun Jul 23 2000 - 07:52:26 MDT

>From Nature,
Monday 24 July 2000

biotechnology : We can rebuild him

Artificial skin grows on the scaffold in a matter of days.

"Gentlemen, we can rebuild him, we have the technology", the makers of the
‘bionic man’ famously claimed. Six-million-dollar men remain science
fiction, but modern-day researchers are perfecting techniques to build and
replace human tissue. Bioengineers in Japan have now developed support
materials that could help grow better artificial skin, blood vessels and
even vital organs - though telescopic eyes and tank-busting forearms will
have to wait.

You will not be as lucky as the bionic man if you crash your prototype space
vehicle. Artificial skin is the only synthetic tissue currently available to
patients, though heart valves, bones and liver tissue have all been grown in

The new material developed by Guoping Chen and colleagues at Tokyo
University, Japan, could offer a better way to make these synthetic body
parts. It acts as a three-dimensional scaffold on which cells grow and
organise themselves into the desired shape and tissue structure - just as
the human skeleton provides support for our bodies. The scaffold then
degrades, leaving the fully formed tissue behind.

Such scaffolds are not new. They form the basis for artificial tissues
throughout the world. But the material developed by Chen’s group offers a
step forward that "seems very novel, exciting and could be extremely
useful", says Mathis Riehle, a bioengineer at Glasgow University’s Centre
for Cell Engineering, UK.

The Japanese researchers combine two existing scaffold technologies - the
natural polymer collagen and a synthetic polymer mesh. Both have drawbacks:
collagen is weak and cells do not grow easily on synthetic polymer surfaces.
So the two materials are usually combined to pool their benefits. But such
‘hybrids’ restrict cell growth because they either simply coat the polymer
chains in collagen or immerse the whole network in a thick collagen gel.

Chen’s team takes a different approach, as they report in Chemical
Communications1. They amalgamate a polymer mesh with collagen sponge. The
sponge forms a second mesh inside the holes of the synthetic net - providing
greater support for growing cells. Simple but ingenious says Riehle, "it’s
quite astonishing that nobody has previously thought of combining these two

The new material’s extra strength will be its biggest asset, Riehle
predicts. It is almost as strong as conventional polymer meshes, and much
more resilient than collagen sponge alone. And it works: skin cells cultured
on the new hybrid grow into a connected layer within days, after which both
the polymer and collagen degrade.

But what works in the laboratory does not always succeed in the body, Riehle
cautions. Toxic chemicals used to strengthen the collagen fibres could leak
out, he warns. And the apparently rough material surface could make delicate
tissue construction difficult.

Still, the new material could to offer a simpler and more robust method of
making artificial skin and other tissues.

Chen, G., Ushida, T. & Tateishi, T. A hybrid network of synthetic polymer
mesh and collagen sponge. Chemical Communications [published on-line on July
19] (2000).
Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE

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