STEM CELLS We hear a lot about
stem cells these days, but what are they,
where do they come from and what do we really
know about them? Inside our bodies
there's a microscopic world, busy and complex
like the world around us. Stem cells build
and maintain this world. This is a story of stem cells
and their lives inside and outside our bodies. Life begins with one cell,
the fertilised egg. Throughout development
cells divide over and over again to produce the billions
of cells that make up the body. At certain stages, most cells
stop making copies of themselves and start to specialise. When we are fully formed
almost all our cells are specialised. Cells are beautiful things
when you see them down a microscope. Normally they're so miniscule
we can't see them, even though they're
what make us. And each type of cell
has its own characteristic. Some types of cell
grow very closely together and form beautiful patterns. Other types of cell
will move away from one and other. Some cells become big,
others are always very small. It depends on what type of cell they are. These different cell types
work in specialised teams. Some carry oxygen
through the blood system, some do the stretching
and contracting in our muscles, some carry messages between our brain
and the rest of our body. Stem cells are very special cells
They act as a resevoir, because the specialised cells can no longer make copies of themselves. So, if they die and get used up,
they have to be replaced from somewhere. And this is where the stem cells function. Stem cells are used
in the blood system. We need to make millions
of new blood cells every day and these are generated
from stem cells. And these cells actually live
in the bone marrow. Altogether a blood stem cell
can make eight different types of specialised cell. They're used in the skin. We need to make new skin cells
all the time because we're always
wearing away our skin. And actually now we know
they're present even in the brain. We always have to make
new stem cells, so they're not completely exhausted, because otherwise we'd lose
the capacity to make any new cells. So the stem cell has to
make a decision. Every time it divides,
it produces two daughter cells, and those daughter cells
can be new stem cells, or they can be specialised cells. Stem cells in the adult tissues
can normally only make the type of cell in that tissue. So a stem cell in the skin,
can make cells in the skin, but it can't make blood cells
and vice versa. Stem cells are already useful
in medicine. One skin stem cell alone can produce
enough specialised skin stells to cover the whole body. This produced a breakthrough
in the treatment of extensive burns. 1ST DEGREE BURN... When a person is heavily burnt,
we take a sample from an unburnt area
and we take apart the skin sample and we get the cells out of it, and we seed the cells
in a culture flask like this one. We feed the cells with a special liquid,
which is full of protein and sugar. They need to eat like you. At some point, these cells will divide,
will multiply. And they will cover the entire
bottom of the flask. We remove the cells using
a special chemical and we take this sheet of cells
into the surgery room and transplant the patient with it. We can do only part of the skin today, which means we can do
the outer most layer of the skin, which is very important, because without
this layer you wouldn't be able to survive. However, we cannot reconstruct
sweat glands our hair follicles. So these burnt patients have had
their lives saved by stem cells, but they have no hair
and they don't sweat. That is obviously a problem. They are alive, but I can't say
they have a normal life. That's why many laboratories
are trying to understand how the skin is built to be able
to reconstruct it in the lab, so we can improve the life
of these patients. Stem cells are also used to treat
patients with blood disorders, such as leukaemia. A transplant of just
a few blood stem cells, is enough to repair
the entire blood system. Stem cells for specific tissues
and organs can only make the cells
of that tissue. We know there are stem cells
in skin, blood, guts and muscles, but we don't know whether
other organs have their own stem cells, or how useful they will be. Back along the chain of development,
there's another kind of stem cell. It's controversial. It can become
any specialised cell. The embryonic stem cell. This cell comes from a blastocyst,
the stage of development before implantation in the uterus. For fertility treatment, blastocysts are
produced in the laboratory. If they are not used for a pregnancy,
they can be donated for research. In the early embryo,
there's a group of cells that can give rise to
all the tissues of the body. These are the cells
we're very interested in because we know that we can
take the cells from the early embryo and grow them in culture,
and maintain them in a state where they can contribute
to all the tissues. What we're seeing here
is the blastocyst stage of development. It's smaller than a pin head. You can't see it without
the microscope. So at this stage, the cells
in the embryo - these are the cells - they can make any tissue at all. What we have to do, is isolate these cells. One way is we can remove
the trophectoderm cells so that we're just left with a clean
inner cell mass. So we can grow these in culture,
and they'll multiply until we have lots of these cells that still have the capacity to form any tissue at all. Embryonic stem cells can become
heart, blood, brain or skin cells depending on the way they are grown. These stem cells have
turned into heart cells. When you're working with stem cells,
you're always observing the cells and you're trying to understand
how it is they can do what they can do. You're trying, actually, to make them do
what you want to do. It's almost like a battle of wills. A stem cell goes through a long series of decisions to become a specialised cell. A combination of internal and external
signals guide each stem cell along the path towards specialisation. These signals are normally
provided by the body. By figuring out how to recreate
these signals in the lab, scientists aim to grow pure populations
of almost any cell type. The challenge to us is to understand
each decision and how it's controlled. And then how to provide those signals, to impose the direction on the sytem. And once we get to a point
where that begins to happen, then you suddenly see that
you could use it to address medical conditions
and problems. Work that we have
been doing recently has been focussed on trying
to make stem cells for the brain from embryonic stem cells.
And it turns out we're able to do this. These neural stem cells
are now no longer able to make all cells, they can only make three types of cells,
the three types that exist in the brain. So this is an important first step
in creating a useful and powerful system, that can both be applied for drug screening
and perhaps in the end for transplantation. These lab-grown human cells,
produced in large numbers, provide improved models
for testing new medical treatments and may reduce
the need for animal testing. The same cells may help us understand
what goes wrong in complex diseases, like Alzheimer's, Parkinson's
and diabetes. Diabetes is a chronic disease
defined by high blood sugar levels that stay high just because
there is not enough insulin. We know that the insulin is produced by
cells in the pancreas. We call them beta cells. Transplantations of those cells
are now done in clinics. Those cells are isolated from
donor organs. After transplantation with those cells,
you can normalise diabetes. You can correct diabetes. The major obstacle to beta cell
transplantation in diabetes is the shortage of donor cells. We can transplant
only 25 patients per year, while there are more than 50,000 patients
in Belgium that are treated with insulin. We have to look for other techniques to produce insulin-making cells
in the laboratory. What the researchers try to do is first examine this path,
this evolution between the embryonic stem cell
and the insulin-producing beta cell, and then to also try to isolate
the different stages, the different kind of stem cells
on the way to beta cells. If one can then isolate them
and let them grow in the laboratory then you can make as many
insulin-producing cells as you want. And that's the goal
of many investigators in the world. The embryonic stem cell area
is a very exciting area. It really has opened a new world,
that of regenerative medicine. We have now bridges between
all the laboratories that have a particular expertise. Working together,
we will be in a good position to examine, to investigate
its enormous potential, but the enthusiasm should not cover
all the technical and scientific questions and obstacles that exist and that will have
to be studied very carefully. Stem cell research is a fast-moving field. Around the world,
new findings are constantly reported, creating new questions
and fresh challenges for scientists seeking to harness these cells
and to shape future medicine. So cells are the building blocks
of the tissues and organs of the body. And many people are interested in this. What captured my imagination,
was when I realised that in development, cells actually
have to make choices and decide to become
different types of cell, and understanding how that is controlled,
how that decision is made... If you could understand that,
it seems to me, then you would understand
the most important thing about life.
