An Ethical Debate on the Embryonic Stem Cell Research

HUMA DIG ITY OR RESEARCH FREEDOM?

J. CHARLES DAVIS

Introduction

The discovery, isolation, and culturing of human embryonic stem cells has been described

as one of the most significant breakthroughs in biomedicine of the century.1 This promising area

of science has led scientists to investigate the possibility of cell-based therapies to treat disease,

which is often referred to as regenerative or reparative medicine

.

Stem cells give rise to the

multiple specialized cell types that make up the heart, lung, skin, and other tissues and offer the

possibility of a renewable source of replacement cells and tissues to treat diseases including

Parkinson′s and Alzheimer′s diseases2, spinal cord injury, stroke, burns, heart disease, diabetes,

osteoarthritis, rheumatoid arthritis, etc. The Stem Cell Research (SCR) has become the centre of

public attention, both as a fascinating area of biomedical research and as a permanent focus for

ethical and legal controversy.3 The controversy is not because of its goals, but rather because of

the means of obtaining cells. The crux of the debate centres on derivation of embryonic stem cells

which require the destruction of an embryo.

1

See Thomas B. Okarma, "Human Embryonic Stem cells: A Primer on the Technology and Its Medical

Applications," in

The Human Embryonic Stem Cell Debate

, S. Holland, et.al. eds. (Cambridge: MIT Press,

2001).

2

Parkinson′s disease (PD) is a very common neurodegenerative disorder that affects more than 2% of the

population over 65 years of age. PD is caused by a progressive degeneration and loss of dopamine (DA)-

producing neurons, which leads to tremor, rigidity, and hypokinesia (abnormally decreased mobility). PD may

be the first disease to be amenable to treatment using stem cell transplantation. Alzheimer′s disease constitutes

about two thirds of cases of dementia overall (ranging in various studies from 42 to 81 percent of all dementias).

Alzheimer′s disease is a progressive neurologic disease that results in the irreversible loss of neurons, particularly

in the cortex and hippocampus. The clinical hallmarks are progressive impairment in memory, judgment,

decision making, orientation to physical surroundings, and language.

3

See LeRoy Walters, "Human Embryonic Stem Cell Research: An Intercultural Perspective,"

Kennedy Institute
of Ethics Journal

14/1 (March 2004): 3.

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2

1

What are Stem Cells?

Stem cells have two important characteristics that distinguish them from other types of

cells. First, they are unspecialized cells that renew themselves for long periods through cell

division. The second is that under certain physiologic conditions, they can be induced to become

cells with special functions such as the beating cells of the heart muscle or the insulin-producing

cells of the pancreas. Scientists primarily work with two kinds of stem cells: embryonic and

adult

stem cells of animals and humans

.

Scientists discovered ways to obtain or derive stem cells from

early

mouse

embryos more than 20 years ago. Many years of detailed study of the biology of

mouse stem cells led to the discovery of how to isolate stem cells from

human

embryos and grow

the cells in the laboratory in 1998.4 The embryos used here were created for infertility purposes

through

in vitro fertilization5

procedures and when they were no longer needed for that purpose,

they were donated for research with the informed consent of the donor.

1.1

What are embryonic stem cells?

An embryonic stem cell is a primitive type of cell that can be coaxed into developing into

most of the 220 types of cells found in the human body (e.g. blood cells, heart cells, nerve cells,

brain cells, etc). Immediately after the fertilization the cells divide once every 12-18 hours. Each

cleavage-stage cell is called a

blastomere

and

the

3- to 5-day-old embryo is called a

blastocyst.

6

A

fertilized egg is considered

totipotent7

meaning that its potential is total; it gives rise to all the

different types of cells in the body. Stem cells extracted from early embryos can become all cell

types of the body because they are

pluripotent

.

8 In contrast adult stem cells are generally limited

to differentiating into different cell types of their tissue of origin. Thus they are normally

multipotent

.9

4

By a team led by Dr. James Thomson at the University of Wisconsin.

5

In 1978 in vitro fertilization (IVF) led to the first successful human birth.

6

Blastocyst is a

preimplantation

embryo of about 150 cells produced by cell division following fertilization. The

blastocyst is a sphere made up of an outer layer of cells (the

trophoblast

), a fluid-filled cavity (the

blastocoel

),

and a cluster of cells on the interior (the

inner cell mass

).

Trophoblast is the

extraembryonic tissue responsible

for implantation, developing into the placenta, and controlling the exchange of oxygen and metabolites between

mother and embryo. The fluid-filled cavity inside the

blastocyst

of the developing embryo.

Inner cell mass
(ICM)

is the cluster of cells inside the

blastocyst

. These cells give rise to the

embryo

and ultimately the

foetus

.

The ICM cells are used to generate

embryonic stem cells

.

7

Totipotent means "capable of becoming anything".

8

Pluripotent stem cells can give rise to any type of cell in the body except those needed to develop a foetus.

9

Multipotent stem cells can give rise to a small number of different cell types.

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3

1.2

What are adult stem cells?

An adult stem cell is an undifferentiated cell found among differentiated cells in a tissue or

organ, can renew itself, and can differentiate to yield the major specialized cell types of the tissue

or organ. Some scientists use the term somatic stem cell instead of adult stem cell. The primary

roles of adult stem cells in a living organism are to maintain and repair the tissue in which they

are found. They are a very small number of stem cells in each tissue. They reside in a specific area

of each tissue where they may remain quiescent (non-dividing) for many years until they are

activated by disease or tissue injury. The history of research on adult stem cells began about 40

years ago. In the 1960s, researchers discovered that the bone marrow contains at least two kinds

of stem cells. One population, called hematopoietic stem cells, forms all the types of blood cells in

the body. A second population, called bone marrow stromal cells, was discovered a few years

later.

In 1990s scientists discovered that the adult brain does contain stem cells that are able to

generate the brain′s three major cell types--

astrocytes

and

oligodendrocytes

, which are non-

neuronal cells, and

neurons

, or nerve cells. A number of experiments over the last several years

have raised the possibility that stem cells from one tissue may be able to give rise to cell types of a

completely different tissue, a phenomenon known as plasticity. Examples of such plasticity

include blood cells becoming neurons, liver cells that can be made to produce insulin, and

hematopoietic stem cells that can develop into heart muscle. Therefore, exploring the possibility

of using adult stem cells for cell-based therapies has become a very active area of investigation by

researchers.

1.3

Successes of adult vs Failures of embryonic SCRs

Researchers in China met with a disastrous result. Fetal tissue injected into a patient′s

brain produced temporary improvement, but within two years the patient developed a brain tumor

and died. An autopsy revealed that the fetal cells had taken root, but had then metamorphed into

other types of human tissue ­ hair, skin and bone. These grew into the tumor, which killed the

patient. At Columbia University′s College of Physicians and Surgeons, the implanted embryonic

cells apparently grew too well in some of the patients, churning out so much of a chemical that

controls movement that they writhed and jerked uncontrollably. Dr. Paul E. Greene called the

uncontrollable movements developed by some patients as

"absolutely devastating

." He said,

"They chew constantly, their fingers go up and down, their wrists flex and distend. It′s a real

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4

nightmare. And we can′t selectively turn it off. o more fetal transplants. We are absolutely and

adamantly convinced that this should be considered for research only."

10

In stark contrast to the failures of embryonic SCR, the future looks very promising for

treatment with adult stem cells. The following are a sampling of research breakthroughs with

adult stem cells.11

· Researchers at Harvard Medical School say adult stem cells may eliminate the need for

embryonic ones. The researchers experienced a permanent reversal of Type 1 diabetes in

mice by killing the cells responsible for the diabetes. The animals′ adult stem cells took

over and regenerated missing cells needed to produce insulin and eliminate the disease.

The results hold promise for rheumatoid arthritis, multiple sclerosis, lupus and more than

50 other ailments.

· At the University of Texas MD Anderson Cancer Center in Houston, a man with a rare,

potentially fatal skin disorder that was so severe that he could no longer eat, is now

symptom-free after receiving a transplant of his own adult stem cells.

· Doctors at Northwestern Memorial Hospital in Chicago extracted the adult stem cells from

the blood of two Crohn′s patients and successfully used them to rebuild their faulty

immune systems.

· Researchers at the University of South Florida in Tampa have found that adult stem cells

from the umbilical cord blood may be able to help repair damaged brain tissue after a

stroke.

· Dr. Edward Holland of the Northern Kentucky Eye Laser Center in the greater Cincinnati

metropolitan area, is using adult stem cell transplants as part of a treatment to dramatically

improve the eyesight of his patients.

· The Albert Einstein College of Medicine in New York came to similar conclusions. A

study by the Institute for Stem Cell Research in Milan, Italy showed that certain cells from

the brains of adult rats can be used to generate muscular tissue.

· Scientists at the University of Medicine and Dentistry of NJ have found that bone marrow

cells may be converted into replacement nerve cells, able to treat brain and nerve injuries.

Dr. Ira Black and his team were able to convert 80% of the bone marrow cells into nerve

cells.

· Diane Irving, Ph.D., a former professor of biology at Georgetown University and former

biochemist with the National Cancer Institute, said,

"I have argued that adult stem cells
are better because they are closer to the stage of differentiation than embryonic or fetal
cells ­ therefore they do not have as long a distance to travel differentiation-wise as the
younger cells. Therefore there is far less of a chance for genetic errors to be accumulated
in the implanted cells and less side effects for the patient to deal with."12

10

Cited in Bradley Mattes, "Embryonic Versus Adult Stem Cells? It′s Really No Contest."

http://www.lifeissues.org/cloningstemcell/bradsarticle.html.

Cf. AAAS Policy Brief: Stem Cell Research.

Updated December 14, 2007. http://www.aaas.org/spp/cstc/briefs/stemcells/. Accessed on 31.05.08.

11

Ibid.

12

Ibid.

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