stemcells notes

7/30/2019 StemCells Notes

1/17

Morality of Stem Cells


2/17

Stem Cells

Definition of stem cells Stem cells are pluripotent cells that can produce

many different kinds of cells. A fertilized egg isomnipotent, i.e. can produce all cells.

Different kinds of stem cells Embryonic stem cells come from embryos ( 6 weeks)

Stem cells are present in some adult tissues,including brain, spinal cord, and bone marrow.


3/17

Embryonic vs. Adult Stem Cells

Embryonic stem cells

Embryonic cells are

pluripotent and virtually

immortal. Embryonic stem cells can

form tumors called

teratomas.

Several methods are now

available to controlgrowth of embryonic

stem cells.

Adult stem cells Adult stem cells also

have the capacity to

produce many differentcell types, includingneurons.

A persons own stemcells should be the bestsource of cells for

transplantation Adult stem cells will

eventually substitute forembryonic stem cells.


4/17

Embryonic Stem Cells

Adapted from the New York Times

18 December 2001


5/17

Fetal Stem Cells

Neurosphere

from rat brain

Nestin stain BRDU stain


6/17

The Stem Cell Debate

On August 9, 2001, President George Bush announced that NIHwill fund human embryonic stem cell (HESC) research for thefirst time. The research will be restricted to 72 cell lines derivedfrom surplus fertilized embryos before August 9.

Both opponents and supporters of HESC research are unhappywith the ruling. Opponents believe that federal funding ofhuman ESC research will open a Pandoras box leading to babyand organ factories. Supporters believe that the restrictions willhold back crucial research that will benefit millions of people.

Researchers have recently found that they can create clonedembryos. Stem cells derived from such embryos have the samegenes and are an ideal source of stem cells for transplantation.Congress, however, is considering a bill that would outlawmaking of cloned embryonic stem cells.


7/17

Importance of Stem Cells

Studies of human embryonicstem cells will lead to majoradvances in human biology

Embryonic stem cell

research will provide criticalinsights into mechanisms ofcell differentiation, growth,and death.

Understanding stem cellsmay provide keys to why

people age. Limitations on the study of

human embryonic stem cellresearch will hold backbiomedical research.

Human embryonic stem celltherapies can save lives andrestore function of people

Human embryonic stem cell

can replace damaged or lostcells

These include diabetes,degenerative neurologicaldiseases, demyelinativediseases, brain & spinal

cord injury. These conditions are the

most common and costlycauses of disability in theUnited States.


8/17

Opposition to HESC Research

Killing human embryos isunacceptable

Use and study of humanembryonic stem cells will

require destruction ofhuman embryos.

Killing human embryos isunacceptable, no matterhow much good suchresearch will bring about.

The facts that embryos willdie anyway and that manypeople would benefit fromthe therapies do not justifykilling embryos. The enddoes not justify the means.

Embryonic stem celltherapies are not necessary

Adult and other sources ofstem cells, i.e. umbilical

blood or bone marrow stemcells can be used.

Many studies suggest thatstem cells from thesesources are beneficial inanimal disease models

Embryonic stem cells mayform tumors whereas adultstem cells have limitedgrowth potential and areless likely to producecancers.


9/17

Common Misconceptions

Human embryonic stem cellresearch encourages abortions.

The proposed NIH research willuse frozen fertilized eggs, not

aborted fetuses. The fertilized eggs are used

with permission of the parentswho would otherwise discardthem.

Availability of human embryonic

stem cells should reduce thecurrent need for and use ofhuman fetal tissues to treatParkinsons disease and otherconditions.

The research will increasekilling of human embryos.

The proposed NIH researchwill not create or clone

human embryos. Only fertilized eggs that

were already been createdfor the purposes ofin vitrofertilization are used.

Availability of this source of

stem cells should reducecurrent unrestricted creationand destruction of humanembryos for their stem cells.


10/17

More Misconceptions

Embryonic stem cells comefrom embryos that canbecome adults

Thousands of fertilized eggs

are being discarded fromfertility and not being usedfor research or therapy

Many fertilized eggs havebeen stored beyond thetime when they are suitable

for producing embryos. Many parents do not want

their eggs to be adoptedby others.

Embryonic stem cells comefrom embryos withrecognizable body parts

Embryonic stem cells come

from blastocysts (2 weeks),little round balls of cells withno discernible organs orbody parts.

The blastocysts are neverimplanted into a uterus.

Embryos form only after thenotochord appears at about2 weeks. Embryos becomefetuses at 6 weeks.


11/17

Current Situation

Current laws do not regulate

embryo production or use by

private companies

Many companies producestem cells from human

embryos created for this

purpose.

Some private organizations

are developing stem cells

from aborted fetuses. Some companies are even

cloning human embryos to

develop stem cell lines.

Most human embryonic stem

lines belong to private

companies.

Companies therefore mustdevelop their own lines if

they want to do human stem

cell research.

A public source of human

embryonic stem cells should

significantly reduce thenumber of embryos that are

created and destroyed for

their stem cells.


12/17

Stem Cells vs non-Stem Cells

Stem cell therapies willrevolutionize medicine.

The current generation ofdoctors will be the first to

use stem cell transplants torepair and replace tissues.

Genetically modified stemcells can deliver molecules.For example, insulin-secreting cells may replace

life-time insulin injections. Stem cells are important

class of transplantable cellsbecause they are robustand produce many celltypes.

Non-stem cells may bebetter for some purposes

Genetically modifiedfibroblasts, for example,

have already been shown todeliver gene products

Mixtures of progenitor cellsthat produce only one kindof cell may be more easy tocontrol than stem cells.

Some specialized cells mayhave advantages over stemcells. For example, Sertolicells have anti-immuneproperties.


13/17

Human Cloning

http://news.bbc.co.uk/hi/english/sci/tech/newsid_371000/371378.stm

First human clone by

placing human nucleus into

a cows egg and growing itto 32-cell stage.

Nov 1997

Scientific American article reporting the

first cloned human embryo showing a

fertilized cloned oocyte and cumuluscells. Advanced Cell Technology

Nov 24, 2001

http://www.sciam.com/explorations/2001/112401ezzell/


14/17

Religious Positions

Human embryonic stem cells are immoral The Catholic and Greek Orthodox Churches believe that

embryos are potential humans. Even if embryos are being

destroyed for other reasons, their use is immoral. Research and use of early embryos is not immoral

The Synod (Protestant) believes that human embryonicresearch is not immoral if it occurs before implantation

Islamic schools do not recognize early embryos as moral

persons and have no difficulty with use and study of them. Life-saving research is a moral obligation

The Jewish faith believes that saving human lives is a moralobligation and a divine mandate as long as care is taken toensure that the process is fair to all parties involved.


15/17

Philosophical Positions

The wisdom of repugnance argument Dr. Leon Kass applied this phrase to therapeutic cloning,

meaning that we know, deep down, that it is immoral tocreate human embryos to use them.

The sanctity of life argument Some philosophers have invoked the sanctity of life as an

argument against using embryonic stem cells. This reducesthe question to our definition of life and a person.

The respect for the embryo argument Human life demands respect. While it is not disrespectful to

use an organ from a dead person, some argue that it isdisrespectful to create an embryo and kill it for its stem cells


16/17

A Better Compromise

Allow NIH to use stem cells derived from fertilizedeggs under a strict guideline of demonstrated need. This provides sufficient diversity for therapy.

It will reduce the embryos use by private companies. Ban implant of non-fertilized eggs into human uterus

This ban on reproductive cloning is eminently enforceable.

It would allow cloning of eggs for infertile women.

Allow therapeutic cloning with a sunset clause This provides a temporary solution until adult stem cells and

other alternatives can be developed

It will prevent the flight of stem cell and cloning researchoverseas


17/17

Conclusions

Both sides of the debate share the same goal:minimize creation and destruction of human embryoswhile accelerating stem cell therapies

The current policy of limiting stem cells createdbefore August 9, 2001 will encourage unregulateduse of embryos while delaying stem cell therapies

Proposed anti-cloning legislation banning therapeuticcloning is not enforceable, delays stem cell therapies,and will drive scientists and companies overseas

A better policy would be to allow NIH to use newstem cell lines, ban reproductive cloning, and allowtherapeutic cloning with a sunset clause

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