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Hello, my name is Elaine Fuchs. I'm an investigator at the Howard Hughes Medical Institute
and a professor at the Rockefeller University.
We're located in Manhattan, in New York City, in the United States.
My laboratory studies stem cells.
We study their biology but we're also very mindful
of the promise of this biology of stem cells for regenerative medicine.
And today I'd like to tell you a little bit about stem cells
and then move into the kind of research that my laboratory does on adult stem cells in the skin.
So, at the Rockefeller University in New York City,
if we look out my window, at night, on the Fourth of July what you'll see are these fireworks.
And the reason is that my laboratory is located in the Rockefeller Research Building
and we are right over the East River and right in the heart of Manhattan.
And in Manhattan there are lots of people and there's a lot of exciting science going on.
So let me tell you a little bit about the science that we do.
We study stem cells and I'd like to start with just a simple question.
What are stem cells?
Well, stem cells are cells that have the capacity to make an animal (those are embryonic stem cells)
or they can make and replenish a tissue, such as in adult stem cells.
And stem cells of the body have the remarkable capacity to undergo
a process that we call self renewal. These cells are able to divide endlessly to generate self.
But these cells also have the remarkable capacity to be able to divide to
generate cells that are very rapidly proliferating
that we call transit-amplifying cells or TA cells.
These cells are in a transition zone. So they're rapidly proliferating and at some point
along the lineage these cells then will go on to differentiate to create the tissues of the body.
So what's the difference then between an embryonic stem cell and an adult stem cell?
Well, embryonic stem cells are what we call totipotent.
Embryonic stem cells have the capacity to generate
all of the tissues of the body. In contrast, adult stem cells are what we call multipotent.
These cells can generate several tissues.
Examples such as hematopoietic stem cells of the body that can generate blood,
cells of the immune system such as
B lymphocytes and T lymphocytes, and macrophages
or cells of the hair follicle stem cells.
These cells can generate not only hair follicles but also epidermis and sebaceous glands.
There are also cells of the body, stem cells of the body, that are called unipotent stem cells.
And these cells have the capacity to generate only one type of tissue.
An example of that would be the epidermal stem cell,
which as far as we know is only capable of generating epidermis.
Or, liver stem cells which as far as we know are only capable of generating hepatocytes.
So, where do embryonic stem cells of the body come from?
Well, my laboratory studies the mouse as do many of the researchers in the stem cell field
and in the early developing embryo we call this a blastocyst.
And already at just, only a few days old the blastocyst already has differentiated into two different cell types.
One cell type you see here in pink. These cells are called trophoblast cells.
These are feeder cells that support an additional group of cells called the inner cell mass.
These inner cell mass cells are the only cells of the trophoblasts that are able to give rise to the fetus.
These trophoblast cells are, in contrast, cells that are supporting the inner cell mass.
So the inner cell mass of the blastocyst has the capacity to develop into the fetus
and these trophoblast cells are support cells. They do not contribute to the fetus.
So another remarkable capacity about embryonic stem cells and about early stages of embryogenesis
is that all of this development can happen outside the womb.
This can happen in a tissue culture dish.
So, cells from the inner cell mass can be removed.
We can take these cells and we can put them into a tissue culture dish
and now these cells, which become embryonic stem cells, can divide and replicate endlessly.
So these cells continue to divide, they continue to generate more and more embryonic stem cells
an infinite supply of embryonic stem cells.
And then we can appropriately adjust the tissue culture conditions
so that we can regenerate blastocysts in a culture dish.
So these embryonic stem cells are capable to give rise
to this structure with an inner cell mass and with a trophectaderm.
And yet if we culture our conditions slightly differently,
these cells can just divide and endlessly generate more embryonic stem cells.
And then, if we take this blastocyst and we implant that into a pregnant female mouse,
that blastocyst will give rise to a whole mouse.
And so these are truly totipotent cells. We can divide them endlessly in a tissue culture dish
and if we culture them to the blastocyst stage,
we can implant those blastocysts into the mice and generate more mice.
So, why is this important for regenerative medicine?
Well, scientists study mouse so that we can learn more about the biology of stem cells.
But this technology has enormous implications for regenerative medicine.
How? Well, these cells might be able to be used to generate nerve cells.
And nerve cells if we're able to generate them in culture could be used to generate
or treat Parkinson's disease or Alzheimer's disease,
different types or neurodegenerative diseases.
Nerve cells might also be useful in treating very bad injuries,
spinal cord injuries from football or automobile injuries that could paralyze an individual.
If we're able to take these embryonic stem cells and specifically produce pancreatic islet cells,
those pancreatic islet cells might be useful for the treatment of diabetes.
If we could take these embryonic stem cells and be able to make muscle cells or cardiac muscle cells,
we might be able to use them for treatment in muscular dystrophy patients
or alternatively in terms of degenerative heart disorders.
These cells might also be able to be used to generate immune cells
which could be used to generate or treat immune deficiency disorders.
And finally, as scientists we might be able to use these stem cells
to be able to understand more about the basis of cancers
and that understanding might lead to new and improved treatments of cancers.
So for all of these reasons, that's why scientists are so excited about
the potential of embryonic stem cells
and we need to know more about the basic biology of stem cells
in order to find out whether any of these wonderful, potentially wonderful
uses of stem cells might actually become a reality.
So, this whole problem is not without ethical issues involved.
Why is there so much controversy over the issue of human embryonic stem cells?
And specifically human embryonic stem cell research?
So, on the one hand you could argue that
human embryonic stem cells are typically cultured from fertilized eggs.
On the other had though, you could argue that those fertilized eggs, in fact,
entail the destruction of a fetus when you then culture them to produce embryonic stem cells.
But, you could argue and say, "Well, human blastocysts and embryonic stem cells can be
created with egg and *** in tissue culture."
As I've just described to you there is no womb that is necessary
in order to take embryonic stem cells and culture them to the point of blastocysts.
And so, in fact, you can take a human egg and combine it with ***
in a petri dish and be able to generate blastocysts from which you can then culture
embryonic stem cells as I've just described for you.
This is the same technology that's already in place across the world
in various different advanced medical institutions that conduct in vitro fertilization to generate
babies for parents that aren't able to be able to generate babies in the normal fashion.
So embryos from in vitro fertilization are often discarded or kept frozen and unused.
Isn't it important then that we take these unused or discarded
embryos from in vitro fertilization and make good use of them in research?
Many researchers feel that that should be possible.
But then others believe that we could take these embryos
and instead offer them to another woman who would like to have a child.
So these embryos could still be used, instead of discarded, could be used
by others to carry them to term in a woman.
But, as I said we could use them for research to learn how to generate neurons,
pancreatic islet cells, muscle cells, for treating various different human disorders and injuries
for which we have, presently, no cure.
So what are the potential ways in which we might alleviate these ethical concerns.
Well, scientists only recently have learned that it's possible to
clone embryonic stem cells by taking an egg cell embryo in a petri dish from a blastocyst
produced by in vitro fertilization and just remove one single cell from that 8 cell embryo
and those 7 cells from the remaining embryo
can still generate a normal human being by in vitro fertilization.
Hence, no human lives are going to be lost in this process
because these 7 cell embryos can still generate a normal human being.
But we could take that one cell and expand that cell as I just described in tissue culture
to generate lots and lots of embryonic stem cells.
So, maybe we could get our cake and eat it too using this particular process.
The technology however, can also be used for couples who have a high risk of passing on a
serious genetic disease and wish to combine genetic identification of embryos
with in vitro fertilization to produce a healthy baby.
So in fact, this type of technology is already in use in various different clinics
where a couple does have a severe risk of passing on some very severe genetic disease to
their offspring and rather than to do that they would rather have their embryos screened
to make sure that they can identify which one is bad and which one is good and they
do that by this type of technology--removing one cell, taking the other 7 cells,
testing that one cell and finding out is it good or is it bad
and then taking that 7 cell embryo and producing a child.
The problem is that, in fact, there are some risks to the embryo by using this type of technology.
And so there are many who believe that the risk for parents
who might otherwise pass on a very serious disease,
perhaps life threatening or psychologically devastating disease,
to an offspring, that that risk is worth the risk because otherwise there's a huge risk,
a 50% risk, that that child might be born with some terrible disease.
But, with regards to research, one obviously would not want to take those 7
cell embryos, considering that risk, and actually implant them and create a normal human being.
There's too much risk involved for that sake.
So for some and in fact for many, this is really not an ethically acceptable way
in which we could alleviate the concerns that do exist for those who believe
that destroying the embryo, even though we can generate that embryo in vitro,
in petri dish, is still problematic for religious concerns.
So these's another hurdle to this technology.
Even if you say, "OK, I'm going to allow this technology because it's important
to come up with new possible cures for regenerative medicine."
there's still another hurdle to the technology and that hurdle is
that the immune system recognizes foreign cells and it eliminates them from your body.
So if I give you embryonic stem cells from a fertilized egg generated
in the fashion that I just described to you and you take those embryonic stem cells
which we perhaps can differentiate into a particular cell type
such as a pancreatic islet cell, if we put those cells into your pancreas,
your pancreatic cells and your immune system are going to recognize that that is a foreign cell
and your immune system is going to wipe that foreign cell out.
So given the technology, there's still a problem even if you say
that you will accept the ethical concerns involved and that the moral concerns
of trying to advance this technology for the use of curing
various, different types of diseases and degenerative disorders is worth the research involved.
So, a pancreatic islet cell, then, made from an embryonic stem cell of an unmatched
embryo is still going to be rejected by the body.
So what other methods can be used to generate stem cells
with broad potential for regenerative medicine?
Well, scientists have thought about this a lot. In fact, we've worked on this a lot.
And one technology that has been developing over the last five to ten years
is that of nuclear transfer research.
This is the technology that's often mistakenly referred to as human cloning,
the technology that was used to create Dolly, which was the first cloned animal
that happened to be a sheep, which was made in England some years back.
So this technology has the capacity to generate more and more and more
of perfectly, genetically identical animals.
So what is this technology involved and how can it be useful in regenerative medicine?
So let me just point out from the very beginning
that scientists and society are opposed to human cloning.
So what is this technology, then? How can we use this for regenerative medicine?
How can we use it in an ethical manner?
So let me first describe to you the process of nuclear transfer.
In this process what we do is to take an unfertilized oocyte
and my laboratory does this type of technology.
We work on mice to be able to understand the process better.
So what we do is we take...start with an unfertilized oocyte,
a single cell coming from a female.
And we then remove and discard the nucleus of this oocyte.
So this is effectively an oocyte now, but it has no genetic information.
So now we give it some genetic information.
We take and replace it with the nucleus of an adult stem cell or any other type of somatic cell.
So we could take a small piece of my skin, pull out the nucleus from that cell
and implant it into an unfertilized oocyte. We do that process from mice.
So what do we do next? So, we now have generated a hybrid cell.
The cytoplasm of this cell comes from the unfertilized oocyte.
The nucleus of this cell comes now from an adult somatic cell.
This is a diploid nucleus because all of the cells of your body, the somatic cell is basically diploid.
So even thought this started out as an unfertilized oocyte
with only the cells from the female,
basically what this cell now has is a diploid, adult nucleus sitting in an oocyte cytoplasm.
So what good is this cell now?
Well, what this cell can now be used for
is we first take the cell, we put these cells in culture
and again, I work on the mice,
take these cells, put these cells in culture, just as I described to you on the previous slides,
we generate embryonic stem cells, just as I described to you from the previous slide,
we can generate blastocysts, many blastocysts, just as we described.
Again, everything in vitro at that point.
But then we take the blastocysts and now we take those blastocysts
and we put those blastocysts into a female host and what that female does is three weeks later
produces pups, mice, and some of those mice, not all those mice, but some of those mice are healthy
and those mice then continue to grow to adult age.
And in fact, these mice now, are several years old and these mice
are perfectly healthy and we cannot tell the difference between these mice and a normal mouse.
And yet these mice came from an oocyte with a diploid somatic cell
and that somatic cell came from a skin stem cell the type of cells that my laboratory works on.
So, these healthy mice then are great.
The problem is that there's still a problem with efficiency.
And in fact even though we've got a couple healthy mice
and in fact we have more than a couple healthy mice,
the problem is that even on the best of days there are still only about 5% of all of the blastocysts
that end up surviving to this point and there are many embryos that do not develop properly.
So this technology is obviously not perfect
and there are problems with taking an adult nucleus and putting it in the oocyte cytoplasm
even though those hybrids, in some cases, can give rise to normal healthy mice.
But now consider the situation for humans.
I already told you that we as scientists are completely against the notion of human cloning.
So, we don't want to get to this stage.
The only stage that we want to get to is
a stage of generating human embryonic stem cells from nuclear transfer.
So what ideally we would like to do is to take cytoplasm from a human oocyte
and put into that cytoplasm a nucleus from your skin cell for instance,
if in fact you are the one that is going to be in need of regenerative medicine
and from that we then want to culture those cells to produce embryonic stem cells.
But now we take the exact same step that I just described to you,
the nuclear transfer experiment
and we now put the cells into culture just as I described to you earlier.
Culture them to the hybrid cell stage to form a blastocyst
and then the third step is to derive our embryonic stem cells from the blastocyst
and now the benefit is
that now we have embryonic stem cells that perfectly match the patient's DNA.
And that means that if we now generate pancreatic islet cells from those embryonic stem cells
that are perfectly genetically matched, now the patient's immune system
is going to recognize those cells, even though they came from a hybrid, the genetic content
was in fact the patient's genetic content
and so this cell basically, is not going to be rejected by the immune cell.
And so by generating embryonic stem cells from a skin stem cell
and making neurons, or muscle cells in culture,
the resulting cells are not recognized as foreign by your immune system.
So, right now scientists have potentially gotten around an enormous hurdle
that just a few years back presented a serious problem.
But now what are the problems remaining?
Well, unfortunately there's still the problem today
of generating healthy human embryonic stem cells
from human oocytes and somatic cell nuclei.
It works quite well, in fact quite beautifully for mice
even though the efficiency of producing healthy cloned mice
is only about 5%, 2%, 1% depending upon the various different researchers
and the various different cell types involved.
In fact, it turns out that to date there's very little evidence, if any evidence,
that in fact we can adapt this type of technology to humans.
That said I think scientists feel very optimistic that it's just a matter of learning more
about differences between mouse embryonic stem cells and human embryonic stem cells
and a matter of learning more about how to improve this type of technology.
And how to adapt technology that we can already use for a mouse and adapt that to human.
If we can we can get around the problem of immune rejection.
So nuclear transfer derived embryonic stem cells have potential for regenerative medicine.
They have potential for research and drug testing on cells from
various different patients with diseases that are inherited but for which little is known.
That is to say that scientists may be able to study Alzheimer's patients
at an early onset by cloning their skin cells.
So if in fact we could obtain good, healthy embryonic stem cells using the nuclear transfer
that I talked about and not only could we use that for regenerative medicine,
but now scientists could also be able to learn a lot about disease processes for which we really don't have
hardly any information or any way of really getting at that process.
So for instance in Alzheimer's disease or Parkinson's disease
one of the problems is that we can't simply say
"Well, let me get a patient biopsy and be able to study those neurons while the patient is living."
So what scientists are forced to do is to be able to understand t he degenerative process
of Alzheimer's disease by looking at an autopsy from an Alzheimer's patient
and trying to work their way back as to what must have happened
or to do genetic testing to be able to try to sift their way through the haystack of
the various different genes which defective give a tendency to Alzheimer's disease.
But if, in fact, we could generate embryonic stem cells from a patient...from an Alzheimer's patient
simply by taking the skin stem cells...
the skin cells from the body and be able to introduce their nuclei into these oocytes
and generate embryonic stem cells, now we could generate neurons in a petri dish.
And those neurons, because they harbor the genetic material of the patient,
those neurons now would be neurons that are, effectively, Alzheimer's neurons.
And if one is studying and family, for instance, with early onset Alzheimer's disease
one could even study the whole process of degeneration
of the neurodegenerative process
by being able to look at...making embryonic stem cells from a patient
long before the patient ever shows any symptoms or signs of the Alzheimer's disorder.
So, scientists are very optimistic and very hopeful that this type of technology,
of nuclear transfer, is not only going to be used for regenerative medicine
but in fact it's going to be enormously valuable with regards to being able to study
a whole host of different types of diseases
for which there currently is just very little avenue afforded to the scientists.
And I also keep in mind then that, in fact, if we're able
to generate different types of disorders, effectively in a petri dish,
different types of defective cells
then it also allows the drug industry, the pharmaceutical industry, now
to come in to say, "Well, what kinds of treatments could be done
to, for instance, prolong the survival of a neuron that otherwise is fated to degeneration?"
So these are the types of experiments and the types of applications that, I think,
really have bolstered the interests of scientists,
so many scientists, so many good scientists in embryonic stem cell research.
And really has, I think, captured also the interest and support of many people around the world.
So let's just talk for a moment then about differentiating
these embryonic stem cells in culture. I refer to this quite a bit.
But, in fact, again, what we do is we take these embryonic stem cells
that we take from a blastocyst now, producing these embryonic stem cells in culture
and now we subject these cells to various different regiments.
Various different types of culture medium that contains different kinds of growth factors:
hepatocyte growth factors to stimulate the production of liver
or epidermal growth factors to stimulate the production of epidermal cells,
various different regiments of growth factors to stimulate the production of neurons.
And then, we basically are able to generate
different types of cells starting with these embryonic stem cells.
So let's just take an example of this. And if we can click now,
I'm just going to disappear for a minute and see if I can click on this movie and show you.
In this case....
cultures that have been generated by embryonic stem cells
which have been treated with various different growth factors to produce
in this case, cultures of trophoblast cells.
So remember I talked about, early on, that those inner cell mass cells
are different from the trophoblast cells.
But in fact, we could start with embryonic stem cells and if we treat them right
in culture we can produce trophoblast cells.
So let's go through another example of what other types of cells we could generate.
Well, as I mentioned, nerve growth factors can basically be used to produce neurons,
various different blood growth factors to produce
cells of the...erythrocytes or immune cells.
Muscle growth factors: scientists have already
been able to differentiate these cells into muscle cells.
Epidermal growth factors: my colleagues have worked out methods
to be able to produce epidermal cells from these embryonic stem cells.
And then we haven't yet done this yet but it might be possible to use hair growth factors
to be able to produce hair cells.
So what are these cell types that I'm showing you here?
I'm going to show you movies in a second.
This cell is a beating heart cell generated from an embryonic stem cell in culture.
This cell is a neuron generated from an embryonic stem cell treated in this way
by basically treating with different growth factors.
So let's take a look now.
First I'll show you the heart cell. It's really quite amazing.
Look at the cell. It happens to be beating.
You can see this cell basically pumping. Amazing!
Contraction of a heart cell generated from an embryonic stem cell.
Now let's take a look at the neuron.
Here you can see the neuronal processes
and you can see that these neurons are being...are extending out exosomal processes.
They don't have connections to make in the brain because they don't have a brain
but basically we can generate neurons in culture.
We can generate beating heart cells in culture.
Again, suggesting the promise of these cells for regenerative medicine in the future.
So let's summarize what I've told you so far.
Human embryonic stem cells can differentiate into any cell of the body.
Neurons or muscle or pancreatic cells derived from someone else's embryonic stem cells
will likely be rejected by the patient.
Embryonic stem cells made from nuclear transfer won't be rejected.
What are the problems remaining?
Undifferentiated embryonic stem cells can cause teratomas.
If we take these embryonic stem cells from a mouse
and we inject them into another mouse, tumors develop.
They're a complex type of cancer
and these cancers contain all of the various different cell types of the body.
Differentiation gone amok.
These cells, perhaps, you could argue, have too much unharnessed potential.
So obviously, if we're going to use these cells we have to very pure populations
of differentiated cells because we wouldn't want an undifferentiated embryonic stem cell to
escape being differentiated if we expose it to, for instance, nerve growth factor.
We wouldn't want to inject an undifferentiated embryonic stem cell because
the risk of developing into other cell types
and differentiating into the wrong cell type is still there.
So there are some hurdles that still need to be considered in the technology.
Ethical issues involved in using an unfertilized oocyte
still pose a religious argument for some.