This is a
biomedical advancement that scientists have always dreamed
about but at the same time has left scientists in a quandary
as they have hoped to be able to reach a solution to the
shortage of donor organs, which is now at a critical level.
Scientists said that every ten minutes someone is put on the
national waiting list to have an organ transplant. Every day
22 people who are waiting on that list pass away as they
have not been given the organ they need. They posed the
question of what if people did not have to rely on the death
of another and a donor as custom organs could be grown
inside a host animal.
While this might
sound far-fetched and something out of a movie, scientists
are now one step closer to making this become reality.
Researchers from the Salk Institute said that they have
created a chimera: an organism that is able to contain cells
that come from two separate species.
In the past,
this is something that has been out of reach of the
scientists. At the moment experiments such as these are not
eligible to receive funding in the US. Up to this point,
Salk and the rest of the team have had to rely on private
donations. Another factor that hampers organism creation
that is part animal and part human is the opinion of the
public.
Jun Wu, the lead
study author at the Salk Institute believes that people
should look at it from a different perspective and pointed
to mythical chimeras which he said included human-bird
hybrids that people call angels. He went on to say that
ancient civilizations always linked chimeras with God.
Ancestors believed that a chimera will guard over a human
and he pointed out that this is what the scientists hope for
with the human-animal hybrid in the future.
Basically, there
are two different ways to make a chimera. The first way
relies on introducing organs from one animal to another and
this is the riskiest due to the fact that the immune system
of the host could reject the organ. The other way starts
back at an embryonic level when one of the cells of one
animal is introduced to the embryo of the other and they
then fuse and grow into the hybrid. While this might sound
strange it does happen to be one way of eventually being
able to solve some of the most puzzling of biological issues
with organs that are grown in the lab.
When stem cells
were first discovered by scientists it looked as though they
contained a scientific promise that was infinite. However,
being able to convince the cells to grow into the organs and
tissues that were right was another matter and very
difficult to achieve. The cells need to be able to survive
in Petri dishes and the scientists used what they termed
“scaffolds” to try to ensure that the organs would grow into
the correct shapes. Patients would also have to undergo
procedures that were not only invasive but painful too to
harvest the tissues that were needed to start the process.
Pig
Lungs Filter Human Blood In A Lab
Juan Carlos
Izpisua Belmonte, a professor at the Salk Institute Gene
Expression Laboratory said that the idea of using a host
embryo so that organs could be grown seemed at first to be
something that was straightforward. This, in fact, turned
out not to be so and it took Belmonte and his team over 40
years to work out how to get a human-animal chimera.
Scientists had
already found a way of taking a mouse and growing pancreatic
tissue belonging to a rat. They revealed that the pancreas
had been used to successfully treat diabetes as parts of the
organs had been transplanted into mice that were diseased.
This is a
concept that was taken one step further by the researchers
of the Salk group and they made use of CRISPR, the genome
editing tool, to get into the blastocysts of the mouse. They
then deleted the genes belonging to the mice that need to
grow certain organs. The scientists then introduced the stem
cells from rats that would be capable of producing the
organs and found that the cells flourished. The resulting
mice lived to become adult mice and some of them grew
chimeric gallbladders that were rat and mouse cells, despite
the fact that rats do not have that organ.
The researchers
then took the stem cells from the rats and they were
injected into the blastocysts of pigs but it failed as pigs
and rats have gestation times that are very different. Pigs,
on the other hand, do have a similarity to humans and their
organs look a great deal like those of humans. The task was
still not easy as scientists had to get the timing perfect
when introducing the cells of humans to the pigs so that
they did not kill them.
Ju Wu said that
they had tried three types of cells from humans during the
experimental process. Finally, they found that naïve
pluripotent cells would not last as long as ones with more
development. The embryos survived when they injected the
human cells that were just right into the pig embryos. These
were then put into the adult pigs, which were left to carry
them for about four weeks before being removed and then
analyzed. 186 late stage chimeric embryos survived with each
of them having about 1 in 100,000 cells from humans.
Scientists are
now trying to work out if it is going to be possible to
boost the number of human cells as the number is low right
now. It is thought that it might take many more years before
human organs that are functioning will be seen, but the work
has been described as being a breakthrough.