Organ Donation and Transplantation
Many organizations raise awareness about organ donation and transplan- tation, including the following ones:
Organ Procurement Organizations ( http://www.organdonor.gov/
materialsresources/ materialsopolist.html): These 58 organizations, which
are managed by the U.S. Department of Health and Human Services, are
responsible for increasing the number of registered donors and for coordinating
the donation process when donors become available.
American Transplant Foundation ( http://www.am
ericantransplantfoun-dation.org/): This foundation raises awareness about organ donation and collaborates with other organ-donation groups.
American Organ Transplant Association ( http://www.aotaonline.org/):
This association helps patients with free transportation to and from a transplant
center, many times hundreds of miles away, and provides transplant patients
with resources about transplantation.
If you put the cryoprotected cells in the
freezer at temperatures down to –30 °C or so,
the cells will not freeze. Instead, the cytoplasm
inside and the solution surrounding cells are
brought to sub-zero temperature, but kept in
a liquid state. The process is not perfect, so
there can be some crystals. This is why a bag
of packed red blood cells looks slushy, so you
may hear them called “frozen” cells, but they
are essentially supercooled—a state in which
a liquid is held below its freezing point.
Could we use cryoprotectants to keep
entire organs supercooled? This is more
difficult than supercooling blood, for a
simple reason. Before cryopreserved
packed red blood cells are infused into a
patient, the glycerol or hydroxyethyl starch
must be removed, so the cells are spun
really fast in a centrifuge. This works well for
cells, but doing that to an organ would squish
it and destroy it.
protectants, which work their way into and
around the cells, so the organ can be supercooled. In 2015, researchers showed that rat
livers could be transplanted successfully after
being supercooled at – 6 °C.
Scientists are working on applying the
supercooling method to human livers and
other organs. This means that within a few
years, organs that are donated could have
shelf-lives measured in days instead of hours.
That would be a major improvement.
Once an organ is supercooled, it is also
possible to take things a step further. An
organ full of cryoprotectants can be cooled
to temperatures so low that water within it
transforms into a solid state, without crystallization. The process, called vitrification, occurs
when glass solidifies from its liquid state.
With the cryoprotectants that researchers are
testing, organs vitrify somewhere below
–100 °C. When this happens, the molecules
move significantly less, and chemical reactions come to a halt.
Unlike freezing, vitrification is not expected
to disrupt connections between cells. For
this reason, vitrification has been replacing
the method of freezing human eggs in fertility clinics. Scientists have also been testing
vitrification on organs. Rabbit kidneys have
been vitrified (Fig. 2) and then warmed and
transplanted into other rabbits.
This type of research could eventually
enable preservation of human organs for
months or years, and that’s when we can
begin thinking about banking organs the same
way we bank blood. If that happens, organ
donation would take on a totally new meaning, because many more organs could be
preserved and potentially save the lives of the
many people in need of an organ transplant.
Who would have thought that chilling temperatures could be so cool?
Maron, D. F. Supercooled Organ Donations Could
Last for Days. Scientific American, Sept 1,
[accessed Sept 2016].
Cossins, D. Will We Ever… Cryopreserve Our
Organs? BBC Future, Feb 24, 2014:
we-ever-freeze-our-organs [accessed Sept 2016].
David Warmflash is a science writer who lives in
Portland, Ore. His most recent ChemMatters article,
“Double, Double, Oil, and Trouble,” appeared in the
December 2015/January 2016 issue.
Scientists have solved the problem by
removing organs from test animals, such
as rats and rabbits, and connecting them to
equipment similar to the cardiopulmonary
bypass machine that kept Jim alive while
his old heart was being swapped for a new
one. The equipment pumps fluid through the
organ’s blood vessels. The fluid contains cryo-
Figure 2. Frozen (left) and vitrified (right) kidney
preservation of human
organs for months or
years, instead of days