a heart and a set of arteries
13 April 2006
From New Scientist Print Edition.
SITTING in a culture dish, a layer of chicken
heart cells beats in synchrony. But this muscle layer was not sliced
from an intact heart, nor even grown laboriously in the lab. Instead,
it was "printed", using a technology that could be the
future of tissue engineering.
Gabor Forgacs, a biophysicist at the University of
Missouri in Columbia, described his "bioprinting" technique
last week at the Experimental Biology 2006 meeting in San Francisco.
It relies on droplets of "bioink", clumps of cells a few
hundred micrometres in diameter, which Forgacs has found behave
just like a liquid.
This means that droplets placed next to one another
will flow together and fuse, forming layers, rings or other shapes,
depending on how they were deposited. To print 3D structures, Forgacs
and his colleagues alternate layers of supporting gel, dubbed "biopaper",
with the bioink droplets. To build tubes that could serve as blood
vessels, for instance, they lay down successive rings containing
muscle and endothelial cells, which line our arteries and veins.
"We can print any desired structure, in principle," Forgacs
told the meeting.
Other tissue engineers have tried printing 3D structures,
using modified ink-jet printers which spray cells suspended in liquid
(New Scientist, 25 January 2003, p 16). Now Forgacs and a company
called Sciperio have developed a device with printing heads that
extrude clumps of cells mechanically so that they emerge one by
one from a micropipette. This results in a higher density of cells
in the final printed structure, meaning that an authentic tissue
structure can be created faster.
“When layers of chicken heart cells were printed
they quickly begin behaving as they would in a real organ”Cells
seem to survive the printing process well. When layers of chicken
heart cells were printed they quickly begin behaving as they would
in a real organ. "After 19 hours or so, the whole structure
starts to beat in a synchronous manner," says Forgacs.
Most tissue engineers trying to build 3D structures
start with a scaffold of the desired shape, which they seed with
cells and grow for weeks in the lab. This is how Anthony Atala of
Wake Forest University in Winston-Salem, North Carolina, and his
colleagues grew the bladders which he successfully implanted into
seven people (New Scientist, 8 April 2006, p 10). But if tissue
engineering goes mainstream, faster and cheaper methods will be
a boon. "Bioprinting is the way to go," says Vladimir
Mironov, a tissue engineer at the Medical University of South Carolina