Gorr, 6:00
R10
USING STEM CELLS TO FACILITATE NERVE REGENERATION
Emma McBride (elm123@pitt.edu)
Electrospun nanofibrous scaffolds, the second type, are
“fine polymer nanofibrous meshes” with “a high surface
area to volume ratio” [2]; researchers have found that a
diameter of 283 nanometers of the nanofibers most
effectively promotes the growth of the neural stem cells
which are placed on the scaffolding [1]. “Contact guidance”
is another property of nanofibrous scaffolds which aids the
outgrowth and elongation of new nerves [1].
Clearly there are advantages and disadvantages of each
type: hydrogels are easily injected into the brain tissue but
they do not help direct the growing nerves, which
electrospun nanofibrous scaffolds do. Therefore, the best
scaffold would be a combination of hydrogels and
nanofibrous. Although miniscule protein scaffolds may seem
trivial, they are crucial in terms of today’s concern over
regenerative medicine.
INTRODUCTION: OVERCOMING BRAIN
DISEASE WITH SCAFFOLDING AND STEM
CELLS
I believe that everyone is entitled to a maximum state of
well-being and that the role of those in the medical field is to
help people achieve this. The most heartbreaking and
uncontrollable diseases often occur in the brain which is
where scientists and engineers should focus their research.
One such way that this can be achieved is in tissue
engineered brain tissues. One of the breakthroughs in
regenerative medicine is the use of neural stem cells on a
protein scaffold to promote the growth of new, healthy brain
tissues. Although some risks are associated with the use of
stem cells, I believe the overall benefits of patient-derived
stem cells are more important. Parkinson’s disease is an
example of a disease positively affected by this approach.
The engineering codes of ethics provide support for the
claim that neural stem cells will be beneficial in the medical
field. In order for people to realize this, however, we need to
educate our engineering students on the application of ethics
to engineering issues.
Sowing Stem Cells as Seeds
Stem cells are the “seeds” that grow on the architecture
laid out by the scaffolding. By definition, “stem cells (SCs)
are characterized by self-renewability, that is the ability not
only to divide themselves rapidly and continuously, but also
to create new SCs and progenitors more differentiated than
the mother cells” [3]. Unlike embryonic stem cells, adult
stem cells do not have the ability to differentiate into any
type of tissue because they are already partially committed
to a certain type, and they are “often defined by the organ in
which they reside” [2]. We are most interested in using adult
neural stem cells, “a kind of specific primitive nerve cell,
[which] exist in the nervous system” [4]. Neural stem cells
are multipotent which means they “are capable of yielding a
more restricted subset of cell lineages” [3], including
neurons and glia [2]. This ability of stem cells to
differentiate into the cells and tissues that we need is one of
their many benefits.
STRUCTURE AND GROWTH: APPLYING
TISSUE ENGINEERING PRINCIPALS IN
THE BRAIN
The technologies relevant to this discussion are tissue
engineered scaffolding and neural stem cells. The protein
scaffold acts as a support for the stem cells to grow on.
The Most Effective Scaffolding
Tissue engineers mimic the cell’s natural support, the
extracellular matrix, by creating protein scaffolds. As stated
in the book Tissue Engineering by Fon et al., “The
fundamental role of scaffolds is to ensure cell survival, and
to enable controlled proliferation and differentiation” [1].
Currently, the two major types of scaffolding in use are
hydrogel and electrospun nanofibrous scaffolds.
Hydrogels are long polymer chains whose macroporous
structure allows for a “high nutrient and waste exchange”
[2]. Because hydrogels have similar properties to the soft
tissue of the brain [2], the structure conforms to the shape of
the injury site where it is injected [1]. The best attribute of
hydrogels is the pore size, the optimal size being 30
micrometers, because it “promotes the healing of biomaterial
implants by suppressing the effects of the [foreign body
response]” [1].
BENEFITS OUTWEIGH RISKS
Tissue engineered scaffolding has numerous benefits and
no risks. The hydrogel and electrospun nanofibrous
scaffolding techniques allow for axon regeneration which is
not normally present in adult nervous systems [1]. Scaffolds
offer physical and chemical support to the growing stem
cells. Similarly to the extracellular matrix, tissue engineered
scaffolds encourage “neurite outgrowth” by “anchoring cells
and promoting axonal growth” [2]. The scaffolds also
provide nutrients and growth factors, stimulating the stem
cells to differentiate and grow.
University of Pittsburgh, Swanson School of Engineering
10/30/12
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Emma McBride
for Parkinson’s disease makes the effort of researching
neural stem cells worth it.
Stem cells, specifically neural stem cells, have
advantages as well. According to research, neural stem cells
“can not only carry out self-division growth, but also
differentiate into nerve cells and neuroglial cells” [4]. They
have the ability to form new nerves, which has many
medical applications. From the perspective of the operating
room, there is minimal damage to the patient and “no
immunologic rejection” [4].
However certain risks come with using stem cells in
general. One of these is that “self-renewal and plasticity are
properties which also characterize cancer cells” [3].
Although some fear that if we lost control over the stem
cells, tumors would form, but there is only a small chance of
this warning coming true. Also, as with all transplants,
certain stem cells, such as embryonic, have the risk of
inducing Graft Versus Host Disease, “an enhanced
inflammatory/immune response … against an environment
perceived as a foreign one” [3]. We can avoid this disease
though by using patient-derived neural stem cells. Because
these stem cells are from the patient’s own body, the
immune system does not identify them as foreign. If we use
neural stem cells in medical applications, the risks are
negligible when compared to the benefits.
PERSONAL BELIEFS
Several times when I was younger, I heard the myth that
most humans only use a small percentage of their brains, and
that a few “special people” had the ability to tap into the rest
of the brain. While I know now that this is not true, I am still
fascinated by the power and capabilities of the human brain.
Last year I read a book about a property of the brain called
plasticity. The brain’s ability to adapt and repair itself is
amazing, and scientists should fully take advantage of this
property by helping the brain fix itself. When the brain
deteriorates as a result of disease, so much of its power and
potential is lost. If scientists initiated the process of plasticity
with stem cells and scaffolding, the brain would have the
ability to restore its own functions.
I believe that everyone has the right to their health, and
scientists and biomedical engineers should not stop
exploring all possibilities until the cure is one hundred
percent effective. We need to make it our priority to find the
best cure. For Parkinson’s disease, this might be using stem
cells to regrow dopaminergic nerves, so this approach should
be researched thoroughly. Although these are the personal
morals that I follow, there are national codes of ethics that
all engineers must abide by.
RESTORING NERVE CONTROL
DAMAGED BY PARKINSON’S DISEASE
We can apply neural stem cells and scaffolding to revert
the damage done by Parkinson’s disease. Parkinson’s affects
1% of adults over 60 with “the loss of a distinct cell type
(e.g., dopaminergic neurons) and degeneration of highly
defined neural pathways” [5], [1]. This depletion of
dopamine results in the loss of control of movement,
including rigidity and tremors [1]. Because today’s
medicines cannot “[revert] the course of the disease, and
they cannot restore the loss of function incurred,” the current
“drug treatment strategies only provide limited relief of
motor symptoms, and the beneficial effects often wear off
after approximately 5 years” [1]. Therefore this is not a long
term solution.
According to an article on dopamine neurons, “cellreplacement therapies may provide the most promising
curative treatment for [Parkinson’s disease]” [5]. The neural
stem cells, with the aid of tissue engineered scaffolding,
would differentiate into the dopamine neurons. There is a
likely possibility of restoring the physical and mental
facilities affected by the disease “if cells can be placed in the
brain to produce suitable, controlled levels of dopamine
release” [5]. The hydrogel scaffolding provides a supportive
environment for the stem cells to grow [1]. In current
practice the transplantation of the stem cells is not at the site
of cell loss, so normal circuitry cannot be recovered [2];
therefore in the future we should focus on getting closer to
the site of cell loss in order to revert as much damage caused
by the disease as possible. The possibility of finding the cure
CODES OF ETHICS: ARE THEY
APPLICABLE?
National Society of Professional Engineers Code of
Ethics
While the National Society of Professional Engineers
(NSPE) Code of Ethics is generally useful to engineering
companies, they do not apply to this discussion on adult
neural stem cells. It is mostly related to the business side of
engineering that companies have to deal with.
The canons regarding business matters are useful in
company situations but not in research applications such as
stem cells. For example, canon number four states
“Engineers shall act for each employer or client as faithful
agents or trustees” [6]. The parts of this canon detail
financial obligations that engineers must follow such as not
accepting compensation from outside companies or more
than one company at a time [6]. Basically, engineers are not
allowed to deceive their employers or clients, which is true
to all other professions as well. Furthermore, canon four of
the Professional Obligations discusses the handling of
confidential information in business affairs, and discourages
disclosing information gained at one company to another [6].
There are also general guidelines provided for in this
code of ethics. Canon two states that “Engineers shall
perform services only in the areas of their competence” [6].
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Emma McBride
According to an article on this issue, “codes [of ethics] can
offer guidance and a common understanding of a
commitment to ethics that can uphold a professional image.
However, codes cannot substitute either for individual
capabilities in solving ethical dilemmas or substitute for
ethics education” [8]. One way that we can teach ethics
individually to engineering students is through assignments
such as this one, which encourage students to research the
ethical policies of a field they are interested in. I believe that
these writing assignments have been useful because they
guide us towards making a decision about what kind of
engineer we want to be. These assignments model the papers
that we will have to write as engineers, as well as guiding us
to explore current engineering issues and ethics. I think that
freshmen engineering students should continue to write these
types of assignments.
We can apply this rule to Biomedical Engineering because
there are so many specializations available, such as tissue
engineering or building prosthetic limbs or developing
pacemakers, and engineers should not work in an area other
than their specific one. While these guidelines are useful,
they do not impact my position that engineers should focus
their research on neural stem cells.
The only canon that directly applies to this discussion of
neural stem cells is canon number one which states that
“Engineers shall hold paramount the safety, health, and
welfare of the public” [6]. This canon is the fundamental
point of the Biomedical Engineering Society Code of Ethics
and is further explained there.
Biomedical Engineering Society Code of Ethics
The more specific rules described in the Biomedical
Engineering Society Code of Ethics reinforce my position
that neural stem cells should be used to research cures for
brain diseases. These codes are more applicable than the
NSPE codes in a discussion on medical research.
Firstly, the guidelines for conducting research outline
appropriate conduct. The first canon declares that
researchers must respect the rights of their subjects by
following ethical and moral responsibilities [7]. This is
crucial to the discussion of testing neural stem cells as a
possible cure for Parkinson’s disease because before it is an
official treatment, there must be many trial groups. These
volunteers have rights to safety and health which must be
respected.
The section on health care obligations also addresses the
rights of patients. Canon one especially deals with the rights
to confidentiality and privacy [7]. The second rule states that
engineers shall “consider the broader consequences of their
work in regard to cost, availability, and delivery of health
care” [7]. This is applicable to the topic of researching new
treatments because it is expensive to investigate and difficult
to find funding. Engineers need to consider the effectiveness
and practicalities of breakthroughs in medicine. I believe
that it will take much effort to perfect a treatment involving
adult neural stem cells but that in the end, the benefits of
finding the best cure to Parkinson’s will outweigh the cost of
exploring this field.
Finally, the rule on training obligations for biomedical
engineers maintains that engineers “honor the responsibility
not only to train biomedical engineering students in proper
professional conduct in performing research and publishing
results, but also to model such conduct before them” [7].
CONCLUSION: OUR DUTY TO THE
HUMAN RACE
With all the technology available to scientists and
engineers, we have a duty to the rest of the world to find a
solution to the diseases that plague our society. An example
of such a disease is Parkinson’s, for which there are various
ineffective drug treatments. We should not stop at just
alleviating symptoms; we should find a way to truly restore
all the original abilities that were damaged. Neural stem
cells have the potential to be this solution. This line of
thinking abides by the code of ethics’ canon about the
welfare of the public because a cure for Parkinson’s would
improve their health. The best way to inform the public
about these ethical rights is by educating engineering
students. Then they will be able to make decisions about
engineering issues such as whether or not to use neural stem
cells in a possible treatment for Parkinson’s disease.
Although there are some risks and public objection, the
benefits of neural stem cells and the possibility to cure
previously incurable diseases cannot be ignored.
REFERENCES
[1] D. Fon, D.R. Nisbet, J.S. Forsythe, G.A. Thouas, W.
Shen. (2011). “Tissue Engineering of Organs: Brain
Tissues.” Tissue Engineering. (Online Textbook).
http://www.springerlink.com/content/w481529730833nh4/fu
lltext.pdf
[2] A. L. Rodriguez, C. L. Parish, D. R. Nisbet. (2012). “The
Potential of Stem Cells and Tissue Engineered Scaffolds for
Repair of the Central Nervous System.” Stem Cells and
Cancer Stem Cells, Volume 4. (Online Textbook).
http://www.springerlink.com/content/p046167436022650/fu
lltext.pdf?MUD=MP
[3] D. Lodi, T. Iannitti, B. Palmieri. (2011). “Stem cells in
clinical practice: applications and warnings.” Journal of
Experimental & Clinical Cancer Research. (Online Article).
INCORPORATING ETHICS IN
EDUCATION
One crucial aspect of training biomedical engineers is
integrating engineering ethics into education, but it is
difficult to teach morals and values to individuals.
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Emma McBride
DOI: 10.1186/1756-9966-30-9
[4] B. Guo, M. Dong. (2009). “Application of neural stem
cells in tissue-engineered artificial nerve.” Sage Journals.
(Online Article). DOI: 10.1016/j.otohns.2008.10.039
[5] R. Fricker-Gates, M. Gates. (2010). “Stem cell-derived
dopamine neurons for brain repair in Parkinson’s disease.”
Regenerative
Medicine.
(Online
Article).
DOI:
10.2217/rme.10.3
[6] National Society of Professional Engineers Code of
Ethics. http://www.nspe.org/Ethics/CodeofEthics/index.html
[7] Biomedical Engineering Society Code of Ethics.
http://www.bmes.org/aws/BMES/pt/sd/news_article/52746/_
self/layout_details/false
[8] J. Li, S. Fu. (2012). “A Systematic Approach to
Engineering Ethics Education.” Science and Engineering
Ethics. (Online Article). DOI: 10.1007/s11948-010-9249-8
ACKNOWLEDGMENTS
I would like to thank Barbara Edelman for answering my
questions about my topic and for clarifying the instructions.
I would also like to thank Writing Center consultant Grace
Noble for reading over my paper and giving useful
comments.
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