Jordana Lenon: Happy Stem Cell Awareness Day, everyone, and thank you so much for coming.
Thank you Tom Zinnen with Wednesday Nite at the Lab and Biotech for the nice introduction, and I'm going to
just jump right in and introduce our speaker for this evening. We're very pleased to have our new associate director for the
UW-Madison Stem Cell and Regenerative Medicine Center, Dr. William Murphy, here to speak to you about stem cells
and tissue engineering. And Bill is an associate professor of biomedical engineering, orthopedics and
rehab, and he is also director of the bio inspired materials lab in the Wisconsin Institutes for Biomedical Research.
Bill earned his PhD in biomedical engineering from the University of Michigan and did a postdoc in chemistry at the
University of Chicago. And he will tell you much more about what he's doing and his lab, and so I'm very pleased to
introduce Bill Murphy. Thank you. [APPLAUSE]
William Murphy: Thanks, Jordana, and thanks to all of you for being here. It's a real pleasure to have a
chance to tell you a little bit about stem cell research going on here at Wisconsin which has been termed the birth place of
stem cell research, and I'll try and describe why that is. And let me also thank Tom Zinnen and Jordana Lenon for putting
this together. And this looks like it's going to be a terrific event. Really well attended.
It's nice that there's so much excitement surrounding this topic area. As Jordana mentioned,
my background is really in bioengineering, and my focused background has been in development of biomaterials.
So I'm not a stem cell biologist, although we do apply biomaterials to stem cell type applications.
And applications in what we call tissue engineering. Because this is a cross-disciplinary field and
there's a lot of different moving parts to it, I'll spend a good bit of the talk today defining terms.
What do we mean by a stem cell? What do we mean by tissue engineering? What is regenerative medicine?
And what are some of the advances being made here at Wisconsin over the past year and more broadly over the past
couple of decades. So I'll go through a series of things, and then I'm told that we'll have some time afterward
to have some Q&A as well. So I look forward to fielding your questions and talking more after the talk during the lab
portion of the session. So without further ado, I'll share some of the discoveries now from Wisconsin.
Just to give you an idea of what I'm going to cover, there are a few basic questions that I'll go through.
The first is, what are stem cells and where do they come from? There are a few different types
of stem cells and sources as well. What are the different stem cell types?
How did this all get started? What's the history of the stem cell field? What are some applications of
stem cells and regenerative medicine technology? And what is what we term tissue engineering?
And then there will be time, as I mentioned, for Q&A at the end. So what are stem cells? Embryonic stem cells have been
termed blank slate cells because they go on to become all of the cell types in the body, which means that essentially they can
generate all of the 220 different cell types that are in the adult organism. Many of these cells turn into
mature dividing cells, which are cells that divide as we grow and grow as we age. Others become tissue specific or
adult stem cells which form an internal repair system. What that means is when we have tissue damage and if we're
talking about organs that turn over quickly, like the blood or the intestine, there are resident stem cells that are
capable of mobilizing quickly and generating new tissues. Those are what are termed adult derived stem cells.
Where do they come from? So adult stem cells for research some clinical uses come from many organs and tissue.
And that is a list that's expanding rapidly. It's becoming more and more clear that there are adult stem
cells present in most adult tissues and organs that do a variety of different sorts of jobs.
Human embryonic stem cells for both research and preclinical uses come from five- to seven-day old embryos that are
fertilized in the lab during in vitro fertilization, and they don't come from aborted fetuses. So this is a common
misconception. These cells don't come from aborted fetuses. In vitro fertilization clinic
patients often have several embryos fertilized and frozen for later implantation in case pregnancy is unsuccessful, and
less than 5% of those frozen embryos are donated for research. After three years, most frozen
embryos are discarded and no longer viable for implantation. So that's sort of the source for the embryonic stem cells that
are used in research applications. This, just to give you an idea of what this looks like, is a
fertilized embryo. So this is an early embryo termed a blastocyst. This is from an in vitro
fertilization clinic. And what you're seeing here is what's called the trophoblast layer on the outside, so it's
sort of this hollow ball of cells. And inside of that hollow ball of cells--
I'll stay in the lighting here, inside of that hollow ball of cells is what's termed the inner cell mass.
So you can see it pointed in that arrow, the blue arrow. And this is where human embryonic stem cells are
isolated. So that's what represents human embryonic stem cells, and that's the portion of the embryo that
will ultimately become the adult human organism. The trophoblast layer on the outside here is what would
become the placenta in vivo during the development of the organism. So as I mentioned, there are a
few different stem cell types. I just described human embryonic stem cells that are isolated from embryos that are taken from
in vitro fertilization clinics. There are a couple different types of pluripotent stem cells, though.
Pluripotent stem cells are the cells that are capable of differentiated or forming all of the cell types that are present
in the body. Multipotent stem cells are stem cells that are more limited. And these are the adult derived
stem cells. Adult derived stem cells can differentiate into multiple tissue types but not all of the
tissue types in the adult organism. So pluripotent stem cells, I mentioned embryonic stem cells,
there are also now genetically reprogrammed mature cells termed induced pluripotent stem cells. And I'll get into this discovery
a little bit later. But in each case, pluripotent stem cells have the potential to become any of the 220 human cell
types. They can divide and survive indefinitely in culture. And they maintain their
developmental potential over time. This is really important. Most cell types, adult cell
types that are taken from humans, ultimately will stop dividing in culture, and they'll lose their ability to form
tissues. These kinds of cells are very unique in their ability to divide indefinitely and their
ability to differentiate into all tissue types in the body. Multipotent stem cells are more tissue specific.
And these are also known as adult stem cells. These come from a variety of different tissue types, bone
marrow, fetal tissue, umbilical cord, blood, skin, muscle, fat and other sources, and they can become some but not all cell
types in the body. A good example is a blood derived stem cell that's termed a hematopoietic stem cell.
These are stem cells that can form all of the mature cell types that are present in the blood, but they're generally
thought to be restricted, to a large extent, to the blood system. So you're not going to see blood
derived stem cells commonly forming neural tissue, muscle tissue, fat tissue, bone tissue. You're going to see these
forming blood tissue. So those are the general types of stem cells. And this goes into a bit more
detail on how the different cell types are generated, particularly the pluripotent stem cell types, which are also
sometimes termed master stem cells because they can differentiate into all tissue types.
So in the case of induced pluripotent stem cells at the top, or IPS cells, skin samples can be taken from a patient and
grown in culture. Those skin cells can then be, so four genes are then introduced into those skin cells.
Those four genes reprogram those cells to form induced pluripotent stem cells. These can be observed after
about four weeks in culture, and then they can be cultured and differentiated into lots of different cell types shown here,
neural cells, hematopoietic cells, cardiomyocytes, which are heart muscle cells, renal cells, hepatocytes, which are liver
cells. So a variety of different directions. On the bottom side here you're
seeing embryonic stem cells, which, as I mentioned, come from the inner cell mass of the blastocyst.
Stem cells can be isolated from there, grown in culture and differentiated down the same sorts of lineages that I
mentioned for the IPS cells. So that gives you sort of a general description of what pluripotent stem cells are and
where they come from. So how did this get started and what is the history of the field?
Mouse embryonic stem cells were isolated initially in 1981 and set the stage for generating genetically engineered mice.
So this was really an important discovery. There was quite a lot of time lapse between the discovery of
mouse embryonic stem cells in 1981 and the initial isolation of primate embryonic stem cells in 1995 and 1996, which really
indicates what some of the challenges are here. It's not simple to isolate these kinds of cells and really a
major discovery to extend from the mouse to the monkey stem cells. In this case, Jamie Thomson's
group here at Wisconsin isolated rhesus and marmoset embryonic stem cells in a series of discoveries in the mid-1990s.
That really set the stage for a major discovery in the late 1990s, 1998, in a paper in the journal Science Jamie Thomson's
team from Wisconsin demonstrated isolation of the first human embryonic stem cells from in vitro fertilization embryos.
And this work showed the first example of isolating these cells from an embryo, being able to culture these cells over very
long periods of time in vitro, allowing them to expand what was termed indefinitely. So these cells could grow
indefinitely. And they were capable of forming tissues along all of the different germ layers of an
embryo. So, for example, they could generate cells derived from the ectoderm, the endoderm and the
mesoderm. I'm not going to get into detail in terms of what those developmental origins mean, but
effectively what that means is that ultimately these cells were capable of generating all of the cell types that are present in
the adult. So really a major story and one that was picked up by the popular press.
One of the maybe less anticipated consequences of the initial isolation of human embryonic stem cells is that
they really ultimately gave birth to what are called induced pluripotent stem cells. Some years later, almost a
decade later, a few different groups were able it generate pluripotent stem cells from adult cells, from adult derived
cells, specifically skin fibroblasts. And this was done by Jamie Thomson's group here, in a paper
that was published, again, in the journal Science in 2007, by Shinya Yamanaka's group in Japan and by a third group as well.
So this was a discovery that was made concurrently by multiple groups. And you can see that there was
quite a lot of interest in trying to generate these cells. What these cells really open the door to is the ability to
generate pluripotent stem cells that are patient specific. So the possibility of taking a cell type from a patient,
transforming that cell in culture into a pluripotent cell which can then generate any specific cell type.
So you can imagine that there are lots of potential consequences of this that are positive.
So what have we done with induced pluripotent stem cells and human embryonic stem cells over the last few years at
Wisconsin? There's quite a lot of exciting research that's come out of this area, and I want to feature just
a few things that I think might be of interest to the audience here. The first relates to
cardiomyocytes. These are the muscle cells in the heart. And in conditions such as heart
disease, cardiomyocytes oftentimes going awry or are missing because of defects that are present in the heart or
scarring that is present in the heart. So there is a great deal of interest in generating adult
cardiomyocytes that are replace diseased or damaged cardiomyocytes in the body and also for generating
cardiomyocytes that can be used to screen for drugs, that can be used against heart disease, to screen for toxins that could
potentially influence cardiomyocytes in the heart, etc. So there's a great deal of
interest in these cells. If one starts with induced pluripotent stem cells and cultures them under just the
right sets of conditions, it's possible to generate cells that will beat like cardiomyocytes, like heart cells, in the lab.
And that's what's being shown here. So if you look on the left, what I'm going to show is a movie and
this is a real-time movie of cells in culture. What you're seeing initially is a big bed of cells that's
sitting in a culture dish, just in a petri dish. And as I start the movie you'll see in beating taking place.
So these cells started out as dermal fibroblasts, skin cells. They were reprogrammed into pluripotent cells, and then
under just the right conditions were induced to differentiate into cardiomyocytes, which you're seeing beating in
culture. And this is done by Tim Kamp's lab. Tim is the director of our Stem
Cell and Regenerative Medicine Center here and is really a world leader in cardiomyocyte development differentiation from
stem cells. A second example of this comes from Igor Slukvin's lab. Again, here at Wisconsin.
What Igor has been able to do is, starting with human embryonic stem cells, identify just the right sets of
conditions in culture to induce these cells to differentiate into blood cells. And what you're seeing here, in
particular, are red blood cells. So this is quite important potentially because everybody is familiar with the possibility of
shortages, the need for blood. If one were able to generate a continuous source of blood derived cells like red blood
cells, there's a great deal of potential clinical potential. Another example comes from Su Chun Zhang's group here at
Wisconsin, again, over in the Waisman Center which is on the hospital campus. Su Chun is working on neural
development mechanisms, understanding how the brain develops, how the spinal cord develops, and has a particular
interest in early stages of neural development. What you're seeing here are cells that were derived from
human embryonic stem cells and then under just the right sets of conditions induced to differentiate into neural cells.
So you see in this culture fibers of neural tissue that are extending from one spot in the culture to another.
And these are stained for proteins that are particularly prevalent in neural tissue like the NF in red and the GFAP in
green. So essentially these are neural proteins that are being stained. So this demonstrates the ability
to form neural tissue from embryonic stem cells. One thing that's really important about this work that I
think represents, in some ways, where the field is going is embryonic stem cells represent the earliest stage of
development. What that means is if we understand how the embryo develops into the spinal cord,
for example, what are the time scales, what are the signals that those cells are exposed to while they form neural tissue,
we can try to recreate that in embryonic stem cell culture to form neurons. So in some sense we're mimicking
development. We're mimicking the way tissues develop in order to create adult cells that can be used for
therapeutic purposes or drug screening or toxin screening. And what Su Chun in this study that was so unique is that he
mimicked some of the timing associated with neural development in order to get very efficient differentiation of
these cells down the neural lineage. So this isn't the first time that one has seen neural cells
come from human embryonic stem cells, but arguably it's the first time it was done with a level of efficiency like this.
So really an impressive sort of mimicry of tissue development. Okay, so just very briefly to review before I get into some of
the applications of these cells, I just want to mention again, so adult stem cells have been studied for more than 60 years.
I'll get into a little bit of the adult stem cell work that's going on here at Wisconsin in a bit.
Mouse embryonic stem cells were first isolated in 1981. That ultimately led to the discovery in the mid-1990s of
non-human primate embryonic stem cells in Jamie Thomson's group. Jamie Thomson's group followed that up with what was really the
big discovery of human embryonic stem cells in 1998 which is what's made Wisconsin the birth place of stem cells.
And then human induced pluripotent stem cells were also first generated in 2007 by Jamie Thomson's group as well as two
other groups. So you with see that there's clearly some level of bias because I'm here at Wisconsin
and here all here in Madison. [LAUGHTER] However, it's very difficult to describe the history
of stem cell research without sounding like we're bragging about what we do at Wisconsin.
Jamie's lab really was the birth place of human embryonic stem cells and a lot of the work that's followed here has by
pioneering in the area. Okay, so adult derived stem cells. As I mentioned, there a lots of
different types of adult derived stem cells, and you're probably familiar with bone marrow transplants.
Bone marrow transplants are a very good example of a stem cell transplant. There are blood derived stem
cells that are present in bone marrow transplants that can repopulate the blood system of a patient.
One of the stem cell types that's really started to gain a lot of attention are what are termed mesenchymal stem cells.
These are stem cells that can differentiate into lots of different connective tissue cells like bone cells, cartilage
cells, in some cases cardiac myocytes, muscle cells, stromal cells that are present in the marrow, cells that are present
in the tendon, and adipose cells, fat cells. Arguably, we don't need more fat cells particularly, given the
obesity epidemic and the ready availability of brats and cheese curds here in Wisconsin in particular.
[LAUGHTER] However, there are reasons why one might want to generate adipose tissue.
So these cells are capable of going down many lineages, not all lineages. So this is where they're limited
when compared to embryonic stem cells. However, for clinical applications, these are
potentially quite interesting and important because they can be isolated in the operating room and placed back into the
same patient, transplanted into the same patient. So there are now systems that can be used today essentially
process bone marrow to process liposuction fat in the operating room to isolate populations of mesenchymal stem cells and then
add them back to a patient. So some of this you'll see in the popular press when you see an athlete flying to Europe to
get a procedure done with stem cells. They're not having embryonic stem cells injected into their
tendons. That's not happening, to my knowledge, in Europe. What's happening instead in many
cases is that they're having procedures done that involve isolating stem cells from their marrow or from their fat tissue
and then injected into a defect site or a healing tissue. And there aren't really clear sets of evidence that those
kinds of therapies are very effective but that's lots of anecdotal evidence. So these things are being done,
but they're not really gaining widespread use. But I do want to highlight, I think, one really good example
of what can be done with this type of cell. And I'll talk a little bit more later about maybe more generally
what's being done with this type of cell. But this is an example from Wan-Ju Li's lab.
Wan-Ju Li is in orthopedics and rehabilitation in biomedical engineering at Wisconsin. And what Wan-Ju is doing is
starting with scaffolds of polymers that degrade, so these are biodegradable materials, he adds stem cells on to those
materials and then he cultures the materials that are cell laden in a bioreactor. What I mean by bioreactor is
that environment is set up to create an environment that promotes cartilage formation by these cells.
In a normal environment these cells might grow, but they're not likely to differentiate into a specific tissue.
They're likely to form maybe multiple different tissue types. But Wan-Ju has identified just the right sets of conditions to
get these cells to different ate into chondrocytes, which a cartilage forming cells, and then since the material degrades
over time, it's biodegradable, it gets replaced by cartilage tissue. And then ultimately what you're
left with is what's termed engineered cartilage. So on the top right here you see chunks of engineered cartilage
that have been generated in the lab. So these are all done in the lab, can be taken off of a shelf
and be placed into a cartilage defect in the body. What Wan-Ju has done recently is formed defects in large animal
models, this is in a pig model, but what he's been able to do is form cartilage lesions that are about eight millimeters in
diameter in the femoral condyle and then replace them with this engineered cartilage and determine whether or not the
cartilage becomes fully integrated into the recipient and ends up becoming functional. And what you see on the bottom
right there is fully repaired cartilage. So you see this smooth surface that's typical of cartilage in
the joint and really nicely integrated with the native tissue. So this is really promising.
The suggestion is that if one has severe osteoarthritis or a cartilage lesion, that's the possibility of taking cartilage
from a shelf and placing it into a defect site. And you can imagine how this might be applied to other
orthopedic tissues like bone tissue, like tendon, like ligament. Okay.
So one just quick description of a few things that have happened this year, and I'm not going to get into detail on any of these
but I just want to describe them because some in the audience might be interested in following up on this kind of information.
There have been a few really high profile papers published from folks at Wisconsin this year in the stem cell area.
The first at the top here is a new method for culturing pluripotent stem cells. It turns out that under most
sets of culture conditions for these cells, the cells have to be exposed to animal products, like serum from animals,
in order to grow properly in culture. So there are groups on campus and elsewhere that are trying to
identify animal free environments that will allow for expansion of these cells so that in clinical applications the
cells don't get exposed to animal products. The challenge with getting exposed to animal products is
that the cells then bear the potential of presenting animal antigens when transplanted back into a patient and that has
immune consequences. So Laura Kiessling's group in chemistry here really used the clever approach to expose stem
cells to surfaces that contain the right kind of surface environment to promote growth of these cell populations.
So the cells will grow in culture and they'll stay undifferentiated, they'll stay stem cells.
So that's really exciting because the surfaces are synthetic. They're all man made.
There's no animal products that are used in that kind of culture environment. The second piece here is genetic
correction of induced pluripotent stem cells from a patient with gyrate atrophy in this advanced hope for therapy.
So Jamie Thomson's group and David Gamm's laboratory essentially have been using IPS technology to try to understand
how diseases might be manipulated, might ultimately be cured by making changes to the genetic code of the cell.
So in that case it was a genetic correction. But this is something that could be done with a variety of
different disease states. This specifically was done with gyrate atrophy. The last piece here, human
induced pluripotent stem cells beginning to form into a structure like a retina in a dish, this also comes from David
Gamm's laboratory. What you see is really remarkable. It's difficult to form retinal
tissue in a dish, but the possibility of doing so using stem cells is really quite exciting because the cells in
the retina are highly specialized and they're difficult to grow outside of the body which means that there's a
need for another source of cells to generate retinal tissue. So those are a few breakthroughs just from this year at
Wisconsin, and it's not unlikely that next year will bring similar levels of breakthrough that we'll be able to talk about
again. Okay, so I mentioned earlier what sorts of applications are possible with embryonic stem
cells and with adult derived stem cells, but I think really there are a few categories. And one of the categories that
generates the most excitement is what's termed regenerative medicine, the ability to replace lost or damaged tissue with
functional tissue that's derived from stem cells. So because stem cells are ultimately capable of making
tissue, they may be able to make tissue for therapeutic purposes. This also is arguably the hardest application of stem
cells to address because of barriers related to regulatory hurdles, FDA for example, and business hurdles related to cost
of these kinds of therapies. So there are a lot of challenges but there's quite a lot being done as well.
So regenerative medicine is a field where lots of different researchers are trying to generate, regenerate tissues in
the body using stem cell related techniques. So it's a new and emerging field, explores stem cells and
derivatives of stem cells to repair damaged or degenerated tissues and can now start to exploit endogenous mechanisms of
tissue repair and regeneration. What I mean by that is this sort of general concept of taking stem cells from a patient,
manipulating them in culture, putting them in a bioreactor and injecting them back into the patient might be the most
complex type of method that we can use. Something that might be much more simple is the idea of
mobilizing native stem cells to generate new tissues because there are some that are already present in the organism.
So there are lots of techniques along those lines as well. So this is a figure that was taken from an article from 1998
in the journal Business Week, and the name of the article was "Biotech Bodies." And I like to describe this
because it's incredibly optimistic. This paper was from almost 15 years ago and describes what
was on the horizon at the time. There was this new era of regenerative medicine right around the corner, and it was
going to be no time, if you read the article, it was going to be no time until we'd be taken bone, skin, pancreas, heart
valves right off the shelf and placing them into a patient. Well, it turns out that because of lots of different hurdles,
including not just scientific hurdles, but as I mentioned, regulatory hurdles, cost hurdles, each of these tissue
types has been really difficult to generate and our regenerative medicine techniques, at least in terms of therapeutic
regenerative medicine, have really been slowed and really a tremendous challenge to put forth.
So there's still quite a lot for us to be doing on the academic side, understanding how we can leverage these cells and what we
can do to help these cells to generate new tissues. But I just want to describe this as sort of maybe a cautionary
tale. The concepts that I described today are really quite challenging, and we're getting
close, I think, but I'm not ready to say that we're going to be taking these kinds of tissues off the shelf in the near term.
What I do think is coming on the horizon relatively quickly is this field that's termed tissue engineering.
And this is the cartoonish representation of the general tissue engineering concept. The idea is one takes stem cells
from a patient, isolates those cells, maybe places them into a bioreactor, seeds those cells on to what's termed a scaffold, the
scaffold has properties and functions that are similar to a scaffolding in a building, provides the shell for the cells
to generate the building over time, ultimately forming a new tissue or a neo-tissue that can be implanted back into that
patient. And the scaffold, in particular, has been an area of constant interest in this field since it
was initially formulated in the mid-1990s. The idea here is one has to generate a scaffold that's
biodegradable. It has to go away over time and allow for formation of a new tissue.
It has to be biocompatible which means different things in different tissue types. In bone it has to be very
strong. In skin, not so strong but it has to be quite elastic. You can imagine the different
tissue types have different requirements. It also has to include what are termed inductive factors.
These are environments that promote formation of a particular tissue type. If you want these cells in a
scaffold to form bone, they typically have to be exposed to an environment that encourages bone to grow.
Okay? So relatively simple but literally every one of the arrows in this graph is an
active area of study with multiple research groups nationwide and worldwide. So there's quite a lot going on
in this field. And the history of this field has primarily been combining mature cell types and material
carriers. What I mean by this is for example, there's a company called Organogenesis that's been
trying to generate skin substitutes in the simplest way you can imagine, taking cells that are known to form skin
tissue, placing them into a scaffold that degrades and allowing these cells to effectively do what they do:
form skin tissue. There's a company called Genzyme that's been generating approaches for cartilage
regeneration where they're isolating autologous chondrocytes, that means cartilage forming cells from a
patient, and they're injecting them into that patient for therapeutic purposes. So they're taking them out,
expanding them, putting them right back into the patient. And then the last piece here, there are areas where
researchers, in particular Tony Atala's group at Wake Forest University, has been generating bladder tissue.
There's a company called Tengion that's commercializing these kinds of concepts. Where the idea is to take smooth
muscle cells and urothelial cells from the bladder, seed them on a construct, and again sort of allow them to do what
they do: form new tissues. So these areas are exciting but they're limited in some important ways.
One is each of these tissue types is either relatively thin or it's poorly vascularized. And there's a reason for that.
It's difficult to generate highly vascularized large chunks of tissue. So tissues like bone and
cardiovascular tissue that need a lot of blood vessels to supply a large tissue are difficult to generate.
In addition to that, these are tissues that contain one primary cell type generating the tissue, and most tissues don't work that
way. There are some seven or eight different functional cell types in the liver and there's many
more than that if you sort of expand, depending on how you define what is an individual cell type.
So most tissue types and organ types have many different cell types present in this. So as you might imagine, this
has led a lot of investigators to move from adult derived specialized cell types to stem cell types but using the same
general concept. The idea of taking cells, seeding them on to a construct and allowing them to form new
tissues and really encouraging them to form specific new tissues. So the way the field is going
really is toward combining stem cell types and materials with the goal of allowing the materials to degrade and the
stem cells to form the new tissues that are functional. So these are just a few examples.
Embryonic stem cells in sponges that degrade. Mesenchymal stem cells in hydrogels that degrade.
Hydrogels are basically similar to gelatin. Tissue specific scaffold material.
So in this case one can generate a scaffold that looks and acts like bone tissue and that can be seeded with stem cells to form
new bone. And there's quite a lot of different directions that folks are heading here.
But the general direction the field is going is take these stem cells that are capable of doing lots of things, develop
scaffolds that instruct these cells to form some specific tissue type. One thing I'd like to do just
before we finish is describe one example of what I think is an emerging tissue engineering technique, and it relates to a
company that I co-founded a few years back. And I think it gives sort of an example of not just the
positives but also the challenges related to tissue engineering technologies and sort of the way the field is
going. So cranial facial tissue engineering. There's a lot of interest in
cranial facial tissue engineering for a variety of reasons. Not the least of which is for
blast injuries in war veterans. So a lot of the injures that are coming back from Iraq and Afghanistan involve blasts where
soldiers have lost large chunks of tissue from their face, for example. And they might be missing an
entire mandible. It's difficult to replace that kind of tissue and maintain function.
So you can replace it with titanium, but that titanium doesn't maintain function over time, and the bone that's
adjacent to that titanium oftentimes will ultimately become necrotic and you'll have a series of surgeries over time
and an inability to properly chew, facial deformities that extend from these sorts of things as well.
So there's lots of issues associated with using hardware to try and replace these kinds of tissues.
So healing of very large defects in the cranium is difficult. Here's another example. This is actually a cancer
resection. So this was an osteosarcoma where the bone had to be resected and the tissues
surrounding it had to be resected, and then you see on the right-hand side, in that diagram, a large defect.
So what does one do? Very difficult to determine what to do to replace at that kind of a defect.
And what's often done these days is it's replaced with a chunk of titanium and the bone is encouraged to grow over that
titanium, but ultimately that patient won't regain normal function or, in many cases, normal aesthetic appearance.
So there's an interest in using autologous bone grafts. Essentially, you take a bone graft from one spot in the body
and implant it into another spot in the body. And there are lots of procedures that are done in the U.S.
Many times harvested from the hip bone or the femur and then placed in vivo. There are also groups that are
developing growth factors, osteogenic cell, stem cells and osteoinductive scaffolds. So ultimately the hope is to be
able to replace the hardware, like titanium that's often used in current procedures, and to be able to develop more efficient
techniques when compared to autologous bone graft harvesting. Because when you take bone from
one spot and place it into another spot, oftentimes you get what's called donor site morbidity.
So you get problems, pain and loss of function at the donor site. So there's a need to develop
synthetic techniques that are capable of initiating new bone formation in that spot. The challenge, though, is that
in the cranial area, in the maxillofacial area, the aesthetic requirements are quite substantial.
Whatever is placed in this kind of a defect has to form fit quite well. It has to be quite strong
because the chewing forces are high. So it can't crumble under the force of chewing.
And it also has to be porous and degrade over time so that the cells that are going to come in and form new bone can form the
bone and the material can degrade over time. So there's a group that we've been collaborating with at
Michigan, the PI's name is Scott Hollister, who's been developing rapid prototyping techniques, that are oftentimes used in the
auto industry, for example, to generate scaffolds for mandibular reconstruction and more generally for cranial
facial reconstruction. And what you're seeing here is essentially what would amount to a temporomandibular joint on the
lower left. This is on the left-hand side, on the lower left, left-hand side, this is a computational
design of what a scaffold could look like, and on the right, just adjacent to it, is an actual polymer scaffold.
This is an actual plastic scaffold that degrades over time, and you can see that it's porous to allow for a new bone
to grow into the defect site. So there was a company generated from Scott's work and my work called Tissue Regeneration
Systems, and the idea is to move from reconstruction that's commonly done with titanium to regeneration.
The part that we're interested in is trying to promote stem cells to generate new bone in these materials.
So Scott's handling the rapid prototyping and generating the scaffolds, and we're working on filling in the gaps in those
scaffolds. But this is the sort of thing that you can think about doing. Generating scaffolds that will
fit into the mandible, and in this case we actually have sort of a Lego design. There's two pieces that snap
together, there's a pin that fastens them, and then those end pieces go right into the native bone in a mandible defect.
So that scaffold can be generated to essentially any size of defect and it can be generated on-site immediately.
So basically one can take a CT scan of a defect site, generate a scaffold that fits, paste it in.
And one thing that we've been doing at the bottom here is isolating stem cells from bone marrow, placing them into these
kinds of scaffolds so that those stem cells can generate new bone, and then we're creating environments that promote
formation of new bone by these cells. So the point of describing this to you is not to get you to buy
the product. We don't have any products. So this is not an advertisement. What it essentially describes is
one of the ways in which stem cells are being used in the very near-term for clinical applications.
Part of the reason why this is near-term is that that scaffold is likely to be regulated as a device, similar to the wound
dressings that are currently used, the injectable pastes that are used to form bone. And combining these with stem
cells in the operating room is something that can be done without additionally regulatory approval, potentially.
So depending on how it's done and whether or not the cells are manipulated in some way. But if the cells are not
manipulated, then it's possible for the surgeon to essentially isolate the cells, inject them on to a scaffold and place them
into a defect site. And if those cells are properly encouraged to form bone, then there's the potential for
regenerative therapies to get to the clinic maybe more quickly than they would if these cells were grown in a scaffold in a
bioreactor for eight weeks outside the body. That's just much more complicated.
So this is a relatively simple tissue engineering technique. This just gives you an idea of what the general approach is.
You see on the upper portion there a defect in a mandible. One would scan that defect, generate an implant that fits
directly into that defect, load that scaffold with stem cells and other molecules in the operating room and then implant
that scaffold into a defect site. And this happens to be a defect site in a primate model.
What we've found is that new bone will form effectively in these kinds of sites, and we get degradation of these site over a
long time, a couple of years, but it gets replaced with new bone. So quite exciting, I think, as a
potential therapeutic application. So as I mentioned, tissue engineering, this is sort of the
cartoonish representation of what the field can be, but one can argue that the techniques I was just describing that are
maybe short circuiting some of these arrows might be a simpler route to regenerative therapies in the clinic.
And all of these methods are potentially exciting for clinical applications. So before I finish up, I just
want to summarize some facts about stem cells, and I know that I'm sort of beating you over the head with this, but
part of the function of the Wednesday Nite at the Lab talks is to educate. And I know that we have an
audience that has a variety of different sort of expertise in the area. So embryonic stem cells can form
all 220 cell types in the human body. And these are a scientific gold standard for learning how all
cells, including stem cells, work, functionally. Scientists study early embryonic stem cells to understand
reproduction and development. Human embryonic stem cells successfully cultured for the first time just a few years back
are already widely used in drug safety and toxicity tests. And there are companies in Wisconsin that are generating
these kinds of tests. Tissue specific adult stem cells have proven clinically useful for 40 years, albeit in limited
ways. As I mentioned, they don't have the ability to form all cell types, all tissue types.
Tissue specific adult cell types also don't teach us about early reproduction and development. So there are limited things we
can do with adult stem cells. And important to note is that a lot of the debate surrounding stem cells has been one or the
other. Why are we using embryonic stem cells when we have all of these adult derived stem cells?
Why aren't we always using adult stem cells? And then vice versa. If we can isolate embryonic stem
cells, why would we ever want to work with adult derived cells? The embryonic stem cells are more powerful.
Each of those, I think, misses part of the point and that is that each area of research informs the other.
Improved embryonic stem cells culture techniques have led to better ways to grow tissue specific stem cells.
And vice versa. So there's different pieces of the research inform one another. They're really both needed.
So human embryonic stem cell culture led ultimately to the birth of induced pluripotent stem cells which has now become
really an important area in drug screening and understanding disease mechanisms, but there are significant differences
between induced pluripotent stem cells and human embryonic stem cells that we're just starting to understand.
So it's important to note that these are not effectively the same cell type. Embryonic stem cells don't and
never have come from aborted fetuses. I mentioned that that's a common misconception.
They come from five-day-old blastocysts that are grown in a petri dish. IVF procedures are privately
funded and always have been. And then Wisconsin, where, as I mentioned, this is a bit of a focus on Wisconsin's
discoveries, but pioneering discoveries have been made in all areas of stem cell research, brings millions into the state
economy. I didn't really focus on this but really it's an important note.
Stem cell research and regenerative medicine research, more generally, is a form of economic development for the
state, and because Wisconsin is so well positioned on the scientific side and because there's a burgeoning biotech
industry in the town, there's the potential for this really to add a lot to the state economy. And this is a time when clearly
we need things added to the state economy and the national economy. So hopefully this can be
a source of that. Okay, so I think I'll stop there, and I'm delighted to take any questions that you might
have. [APPLAUSE]