From: Gregory Sullivan (sullivan@blaze.cs.jhu.edu)
Date: Wed Oct 22 1997 - 18:02:19 MDT
The topic of attempting to grow body transplant items by using a scaffold
to guide growth was raised by "den Otter" <otter@globalxs.nl>. I had read
about experimental work in this area but could not remember an exact
reference. To find a reference (newspaper quality) I used an interesting
web site that allows you to search a large multi-newspaper archive (100 US
newspapers):
In this archive I found a relevant Detroit News article
Scientists rebuilding the body
June 23, 1997
http://detnews.com/1997/discover/9706/23/06230023.htm
begin excerpt
In its infancy 20 years ago, tissue engineering was limited to growing
flat sheets of cells. But, except for skin, tissues in the body aren't
organized that way. The breakthrough that is driving the research now is
the ability to grow living cells on a synthetic "scaffolding" that will
dissolve away once the cells are firmly established. Using this
technique, Boston-area researchers have grown pretty good looking ears and
heart valves. They can also custom tailor replacement cartilage for
functional spinal discs or joint pads. Key to most of the strategies is
the "matrix," a synthetic mini-scaffold on which the cells attach
themselves and grow. Mooney and many others are using scaffolding
materials based on dissolvable surgical sutures. They're man-made, but
they degrade into natural materials found in the body and are easily
carried away by the blood stream. By altering the mix of suture materials
used in the scaffolding, they can control the rate of its break down "from
weeks to years," Mooney said.
end excerpt
Other techniques are discussed, e.g., methods for arteries. Consider this
excerpt regarding cells in the pancreas.
Begin excerpt
Scientists treating diabetes have made tiny porous beads of degradable
material that contain replacement "islets," the cells of the pancreas that
secrete insulin. The holes in the beads are small enough for nutrients and
oxygen to flow into the islet cells and for the insulin and waste products
from the cells to flow out. But the holes are too small for immune system
components like antibodies or white blood cells to get at the foreign
islets and kill them.
The islet cells, which come from pigs or cows, eventually die on their
own, and the capsules dissolve, so a re-injection is needed a couple of
times a year, but the system delivers insulin only as needed, the way the
body's own system would.
End excerpt
Here it seems possible that using tissue obtained by cloning would be
desirable because the threat of rejection by the immune system is
nullified and the cells may last much longer.
A natural idea I think is the following:
Initiate a clone and then by a process of selecting subsets of cells and
placing the cells in appropriate chemical micro-environments (i.e., with
the proper chemical concentration gradients) cause the cells to
differentiate into needed cells.
Islets cells would be a good example of needed cells for diabetics.
Another example of needed cells would be spinal column nerves which are
still somewhat immature and capable of growth. Some individuals who are
paralyzed because of spinal column injuries have a gap between nerve
endings of bundles in the spinal column. Imagine placing these cells in
the gap and setting up a chemical gradient so that the cells grow across
the gap and reconnect the spinal nerves. Proper physical rehabilitation
may allow these individuals to use their full body again.
Disclaimer: As always, I am a computer scientist and not a geneticist,
embryologist, or medical doctor.
Gregory Sullivan
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