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Hi, I am Dr. Julius Acquello.
I'm a scientist and an educator here at the American Museum of Natural History.
In this segment, I'll be discussing cells and
other organisms that have the properties of stem cells.
What if you could regrow an amputated hand or regenerate damaged brain cells?
People have been fascinated with regeneration since the beginning of biological science.
Regeneration is the reactivation of development in later life to restore missing tissues.
Although mammals have limited ability to regenerate,
other organisms have amazing regenerative capabilities.
Once we observe the wonder of limb regeneration in salamanders, cockroaches,
or seastars, it leads us to wonder why we humans can't regrow back our arms and legs too.
One aspect of regeneration that appears to be common to
most organisms is the use of stem cells to replace missing tissues.
While many animals regenerate,
we'll limit our discussion to two well studied organisms
that invoke cell proliferation in response to injury.
Axolotls or Mexican salamanders are
a favorite animal for scientists to study regeneration.
They have extensive regenerative abilities.
Not only can they regenerate limbs,
but they can also regenerate their eyes,
spinal cord, jaw, tail,
and skin without any scarring.
You can also even cut a part of their spine,
comeback in a month and a half and it will have grown back.
You would not be able to tell that you cut a piece of their spine out in the first place.
After the spine is cut,
the cells on the side of the cut lose their identity.
So instead of being skin cells or blood cells,
they become pluripotent stem cells and they can make
any cellular tissue that the body will need to repair itself.
In this case, axolotls use the pluripotent stem cells to
regenerate all the cells to create a new and perfect spine.
This phenomenon is a favorite among
the scientific community because of its potential to help amputees,
burn victims, and cancer patients.
The study of regeneration help scientists to learn
how adult tissues heal and rebuild themselves.
Researchers are interested in whether we can potentially use
this information for human patients in a clinical setting.
Another well studied group of organisms are the planarians, which are flatworms.
They're a popular model organism in the lab for a number of reasons.
A single planarian can be cut into
as many as 279 pieces and each
will regrow into a complete organism over the course of a few weeks.
They have been referred to as immortal under the edge of a knife.
Scientists don't know if they have pluripotent cells everywhere
or whether an injury side stimulates pluripotent cells to be active again.
One unusual experiment deserves mention.
Planarians do not like to go towards light.
In a lab setting however,
they can be taught to move towards light to get their food.
In this experiment, scientists cut off the heads of the light-loving planaria.
Around 14 days later,
when their heads had the time to regrow,
they were all placed in a petri dish and tested for an aversion to light once more.
The ones taught earlier to go towards the light to get their food kept that memory,
even though they had been decapitated previously.
Somehow, they passed that information along without having their brain.
Scientists study these cells and other organisms in the hopes of gaining insight into
the mechanisms of adult stem cells so that we can learn how to activate them.
What about plants?
The astonishing long lives of plants,
their regrowth and their regeneration capacity,
all depend on the activity of plant stem cells.
Plant stem cells are called Meristems.
Meristem comes from the Greek word Merist(os),
which means divide or division.
Rock cress is a small flowering plant related to cabbage and mustard.
Plant biologists have studied them as a model organism for
a long time and they were the first plant to have its entire genome sequenced.
Rock cress's stem cells are located in two areas.
One, is in their growing tips where they help the length of the plant grow.
They make new leaves, flowers, and stems.
Root tips meristems grow the roots so they can reach more resources from the soil.
So as you can see,
stem cells are not only a human phenomenon.
They can be found throughout nature in a variety of organisms across the tree of life.
And they are important cells not only in these astonishing regenerative examples,
but in the normal development and cellular differentiation of all living organisms.
Stem cells are the cellular beginnings of
all of the astonishing diversity of life on earth.
Dr. Zehra DincerCourse Instructor
