Stem Cell Research

By Daniel Sarfati

I. General

A. Stem Cells

1. Stem cells are undifferentiated (unchanged) cells.

2. There are many different kinds of stem cells, each with different levels of specialization.

3. Stem cells have the ability to divide unequally (one daughter cell would be more specialized than the parent and another daughter cell would be a stem cell).

4. Although stem cells may yield many different specialized cells, they themselves cannot do the functions of those cells (i.e. may yield a heart but it itself cannot pump blood).

5. All stem cells share three general properties: ¹⁾ they have the capability to divide and renew themselves over long periods of time, ²⁾ are unspecialized, and ³⁾ yield specialized cells.

6. Two fundamental properties of stem cells that scientists are studying are: ¹⁾ determining precisely how stem cells remain unspecialized and self-renewing for many years and ²⁾ identifying the signals that cause stem cells to specialize.

7. As scientists continue to learn more about stem cells, it may become possible to use them to screen new toxins and drugs and understanding of birth defects, as well as using them in cell-based therapies.

8. A single cell line can supply endless amounts of cells with carefully defined characteristics.

9. Theoretically, all diseases could be cured by using stem cells because all diseases known occur because cells in the body either are not functioning properly or because they are overwhelmed.

10. The isolations and survival of neural progenitor cells from human post-mortem (cadaver) tissues, up to twenty hours after death, provides an additional source of human stem cells.

11. Stem cell research gives scientists the opportunity to grown pure populations of specific cell types as a proving ground for chemical compounds that may have medical importance.

B. The Different Types of Stem Cells

1. There are two main types of stem cells: embryonic stem (ES) cells and adult stem (AS) cells.

2. The ES cells have three subtypes: totipotent, pluripotent, and multiple or specific stem cells.

C. The Differentiation Process

1. The process of unspecialized cells giving rise to specialized cells is known as differentiation.

2. Stem cell’s differentiation is directed by chemical signals to their location and the conditions in the body.

3. The internal signals that trigger differentiation are controlled by the cell’s genes.

4. The external signals that trigger differentiation include the secretion of certain chemical from other cells, physical contact with surrounding cells, and certain molecules in the cell’s environment.

5.  To generate cultures of specific types of differentiated cells, scientists alter the chemical composition of the culture medium, the surface of the culture dish, or modify the cells by inserting specific genes.

 *Over the years, scientists have established some basic protocols or “recipes” to stimulate the differentiation of embryonic stem cells into some specific cell types.

II. Embryonic Stem Cells

A. General

1. Embryonic stem cells yield the cells necessary to form everything in an organism.

2. Embryonic stem cells can live for very long periods of time (essentially forever) without forming tumors.

3. Embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro, not from a woman’s body. These embryos are donated for research purposed with the informed consent of the donors.

4. In 1998, a group of scientists led by developmental biologist James Thomson, became the first in the world to successfully isolate and culture human ES cells.

5. Due to the embryonic stem cells’ ability to differentiate into any cell in the organism, their therapeutic value is immense.

6. Embryonic stem cells, unlike adult stem cells, proliferate (grow) for a year or more in a laboratory without differentiating.

7. If scientists learn to reliably stimulate the differentiation of ES cells, the result may be used to treat certain diseases or disorders.

8. Scientists discovered ways to obtain stem cells from early mouse embryos over twenty years ago.

9. Five cell lines established at the University of Wisconsin-Madison in 1998 have continued to divide with no sign of diminished ability to multiply.

10. ES cells may pass through several intermediate stages before becoming the cell type needed. This process is controlled by complex chemical cues and without knowing what the cues are, controlling a stem cell’s differentiation is difficult.

11. Even if a tissue or organ was successfully created using ES cells, it could still face rejection from the recipients body. However, certain genetic engineering might yield cell lines with general compatibility.

B. Embryonic Differentiation Process

1. Embryonic stem cells are isolated by transferring the inner cell mass into a Petri dish. The cells are then allowed to proliferate and after several days, the dish becomes crowded and then the cells are gently removed and placed into several fresh culture dishes. These steps are continued and after a few moths, the population of the stem cells will be in the millions.

C. Totipotent Stem Cells

1. The original, fertilized egg cell and its “immediate descendents.”

2. Totipotent stem cells have the potential to form every cell or tissue in the organism.

3. Specialization of the totipotent stem cells begins almost immediately, as these cells begin to form a ball called a blastocyst.

D. Pluripotent Stem Cells

1. Pluripotent stem cells have the ability to form every cell in the organism except the placenta.

2. The blastocyst (a three to five day old embryo composed of a hollow, microscopic ball of cells) is made up of three parts: the trophoblast, the blastocoel, and the inner cell mass.

3. The trophoblast is the layer of cells that surrounds the blastocyst.

4. The blastocoel is the hollow cavity inside the blastocyst with about thirty cells at one end of it. This group of cells is known as the inner cell mass.

5. Pluripotent stem cells can develop into any of the three major tissue types: endoderm (interior gut lining), mesoderm (muscle, bone, blood), and ectoderm (epidermal tissues and nervous system).

E. Specific Stem Cells

1. Specific stem cells are committed to producing only one specific type of cell.

III. Adult Stem Cells

A. General

1. Adult stem cells are used to repair and regenerate damaged organs and tissues.

2. Adult stem cells are thought to remain quiescent or “dormant” until they are activated by disease or tissue injury.

3. The origin of adult stem cells in mature tissues is unknown (unlike ES cells, whose origin is the inner cell mass of the blastocyst).

4. Contrary to previous scientific assumptions, scientists in the 1990’s agreed that an adult contains stem cells that are able to generate the brains three major cell types: astrocytes and oligodendrocytes, which are non-neural cells, and neurons or nerve cells.

5. Recent experiments with adult stem cells have suggested that certain AS cells are pluripotent. This property of AS cells is known as plasticity or transdifferentiation.

B. Advantages (In Relation to ES Cells)

1. If a patient receives a tissue or organ from its own adult stem cells, then it would not face rejection from the body’s immune system.

2. Since adult stem cells are already partly specialize, it would take less outside stimulation to create the specialized cell or tissue.

3. There are no moral objections to using adult stem cells.

C. Disadvantages (In Relation to ES Cells)

1. Adult stem cells are difficult to isolate and purify, and their numbers tend to decrease with age.

2. Adult stem cells may have more DNA damage, and they appear to have a shorter life span than pluripotent stem cells.

3. Adult stem cells are difficult to identify over the billions of cells in the body. Even when found, they are present in small amounts.

4. Experiments done on adult stem cells have shown that it may take months for them to specialize into the particular cell type needed.

5. Adult stem cells do not have the ability to differentiate into every cell or tissue of the organism.

IV. Medical Uses For Stem Cells

A. General

1. Not only do stem cells hold the potential for advances in health care, they also offer science its only view to the earliest stages of human development.

2. A serious concern of using stem cells for medical treatments is the possibility of cancer. Since stem cells can essentially divide indefinitely, researchers must find a delicate balance between growing new cells to repair damaged tissues and making sure that cells don’t overgrow which could lead to tumors.

3. Some biotechnology companies that are developing different strategies for stem cell therapy are Diacrin, NeuroNova, and Neurotech.

B. Uses

1. In the early 1990’s, Swedish researchers injected fetal brain tissue into the brains of Parkinson’s-inflicted people. In the years following this experiment, many of the patients’ situations had improved.

2. Fetal brain transplantations have also helped improve the condition of patients with Huntington’s disease. A study done in Florida indicated that four of the seven people that had fetal brain cell transplantations showed improvements in their condition.

3. Some examples of potential treatments using AS cells include replacing the dopamine-producing cells in the brains of Parkinson’s patients, developing insulin-producing cells for type I diabetes and repairing damaged hear muscle following a heart attack with cardiac muscle cells.

4. Stem cell research is being used to treat: Cancer.

In many cancers, treatments like chemotherapy and radiation can destroy bone marrow. Stem cells could re-create the bone marrow, allowing doctors to use more powerful treatments to treat the cancer. Stem cells could also replace an organ or tissue that had been removed to get rid of the cancer.

5. Stem cell research is being used to treat: Spinal cord injury.

Stem cells have been used to make the nerve cells in the spinal cord, which could help, or even cure people who have lost use of their arms or legs due to a spinal cord injury.

6. Stem cell research is being used to treat: Crohn’s disease.

This illness is an autoimmune disease where the body’s immune system doesn’t work properly and begins to attack normal cells. Doctors could remove the misguided immune cells and use stem cells to create healthy replacements.

7. Stem cell research is being used to treat: Genetic disease

In many genetic diseases, there is a specific defect in the genes. Stem cells that do not have this defect could be used to correct the problem.