Scientists and bio-engineers have been growing all sorts of
interesting things in labs lately -- small advances are made in the field of
tissue engineering every day. Scientists at Massachusetts Institute
of Technology, led by Institute Professor Robert Langer, have made another
such little leap with vascular tissue according to a recently published paper.
Growing blood vessels is not new and have been done for
several years. One of the inconveniences of prior methods, however, was that
when grown, the tissue would "spider" out in any direction, yielding
useful, but not easily worked with biomass. The new technique by Langer and
associates is able to grow the cells in a parallel structure, creating groups
of tubes instead of a jellyfish mess.
Using micro-fabrication machinery at Draper Laboratory in
Cambridge, the group etched out nano-scale patterns on a bed of silicone
elastomer. The patterns, a collection of ridges and grooves, guide the
direction of cellular growth to make it uniform rather than random.
"The cells can sense (the patterns), and they end up
elongated in the direction of those grooves," explained Christopher
Bettinger, an MIT graduate student and lead author of the paper. The cells
aligning and elongating along the grooves in the silicone substrate create
multi-cellular structures known as band structures.
The scientists used endothelial progenitor cells (EPCs) in
their successful experiments. Attempts with other types of cells, including
mature endothelial cells, did not yield results as promising as the EPCs,
failing to create the necessary band structures.
After the flat tissue has been grown on the substrate, the
researchers apply a commonly used gel that induces three-dimensional growth.
The finished product is a group of parallel tubes that could be used in
medicine to replace faulty or failing capillaries in areas where blood flow is
critical for moving nutrients and wastes – areas like the liver, heart or
kidneys.
As capillary structures are not necessarily straight lines,
this technology will improve medical work in that any sort of simple pattern
could be grown on the silicone surface simply by machining the ridges and
grooves into the desired shape. "With this technique, we can take the
guesswork out of it," said Bettinger.
The group had not yet at the time of the paper's publication
attempted to integrate the engineered tissue into a living organism.