Embryonic Stem Cells By John A. Rhude Figure 1. Secretary of health and human Services Tommy Thompson at Promega Corporation in Madison, Wisconsin announcing the release of federal funds for stem cell research at UW Madison ( www.amarillonet.com) Figure 2. Nerve cells developed from embryonic stem cells ( www.) Figure 3. The first human cells coaxed from embryonic stem cells, red blood cell colony. The ability to make human blood may augment or replace the need for blood banks (www.news.wisc.edu.)
Embryonic Stem Cells <ul><li>What are embryonic stem (E.S.) cells? </li></ul><ul><li>Where do e.s. cells come from? </li></ul><ul><li>What practical applications do e.s. cells have </li></ul><ul><li>E.s. cells versus adult stem cells </li></ul><ul><li>Private versus federal funding </li></ul><ul><li>Ethical considerations </li></ul>
I. Stem Cells: What are they? <ul><li>Undifferentiated cells that have the ability to form any adult cell. I.e. Heart cells, liver cells, pancreatic cells, skin cells, nerve cells etc. </li></ul>Figure 4. Embryo three days after fertilization (www. hhmi.org/bulletin/mar2002/stemcells/harvest.html)
Background Information After fertilization the zygote undergoes equal divisions to create two, four, eight cells etc. These cells are considered totipotent (Cells that have the ability to form an entire new organism. Such as twins, quadruplets etc.)
Figure 5. Development of zygote into an individual organism. (www.nih.gov)
Approximately four days after fertilization and several mitotic divisions the totipotent cells begin to specialize, forming a hollow sphere of cells, called a blastocyst . An outer layer develops which will eventually become the placenta and other supporting tissues. An inner cell mass develops which will eventually form every type of cell found in the human body. These cells are considered Pluripotent – they can give rise to many types of cells but not all types necessary for fetal development.
Figure 6. Totipotent cells differentiate into pluripotent which will differentiate into Multipotent and then all types of tissues in the body ( www.nih.gov/news/stemcell/primer.htm , June 11, 2002 )
II. Where do stem cells come from <ul><li>A. The inner cell mass of human blastocysts that were produced through in vitro fertilization (IVF) and donated for research purposes. Keep in mind the embryos were not made for research purposes, but for purposes of reproduction. The embyos Dr. Thomson used were extras from IVF clinics and informed consent was obtained from donor couples. </li></ul>
<ul><li>Dr. Thomson’s technique </li></ul>Pluripotent stem cells were isolated from the inner cell mass of human embryos at the blastocyst stage. These were then cultured in vitro. These cells have the ability to continually divide and maintain the pluripotent state.
Figure 7. Extraction of embryonic stem cells from a human embryo (www.
B. Somatic Cell Nuclear Transfer (SCNT) The nucleus (containing the entire genome) is removed from an egg cell (zygote). A somatic cell , any cell other than an egg or sperm cell, is placed next to the egg from which the nucleus was removed. The two cells are fused. The resulting cell has the full potential ( totipotent ) to be an entire new organism (Dolly the sheep). This cell will form the blastocyst with the outer and inner cell mass, and the pluripotent stem cells can be extracted from the inner mass.
Figure 8. Somatic Cell Nuclear Transfer techique to develop pluripotent stem cells (www.nih.gov/news/stemcell/primer.htm)
Who isolated these cells? <ul><li>Dr. James Thomson and a group of U.W. Madison developmental biologists established five independent stem cell lines in November, 1998. </li></ul>Figure 9. Dr. James Thomson, U.W.Madison Dep. of Anatomy (www.cmb.wisc.edu/profiles/thomsonJames.html)
Figure 10. Method used for stem cell cultivation by Dr. James Thomson (www.wisc.edu.)
III. Potential Applications for Stem Cells <ul><li>Help researchers understand the complex events that occur during embryonic development, especially the factors that turn genes on and off. This could lead to understanding cancers and mutations. </li></ul><ul><li>Stem cells could change the way pharmaceutical companies and researchers develop and test drugs. </li></ul><ul><li>“ Cell therapies” </li></ul>
Figure 11. Schematic of potential applications for embryonic stem cells (www.nih.gov/news/stemcell/primer.htm)
<ul><li>Why Not Use Adult Stem Cell Lines? </li></ul><ul><li>Adult stem cells (multipotent) have not been isolated for all types of tissue. The most common known is the hemopoetic stem cell. </li></ul><ul><li>Adult stem cells have a destiny. Therefore they cannot be coaxed to form any particular tissue </li></ul><ul><li>Adult stem cells exist in very small quantities and their numbers decrease with age. </li></ul><ul><li>Adult stem cells cannot be cultured for long periods of time in vitro at this juncture. </li></ul>
Discussion Topic “Technology has made it possible to unravel our own biology, so that we will be able to manipulate it, alter it.”
Embryonic screening for genetic mutations <ul><li>Blood Tests </li></ul><ul><li>Amniocentesis </li></ul><ul><li>In-Vitro Screening 100 diseases including Tay-Sachs, cystic fibrosis, hemophilia, Huntington’s, Alzheimer’s, . . . </li></ul><ul><li>Cloning </li></ul><ul><li>What do you do with the results? Should we have a choice? </li></ul><ul><li>When is action or alteration warranted? </li></ul>
Child/Adult Disease Alteration <ul><li>Do we really want to know? </li></ul><ul><li>Should we have the right to change the course of destiny? </li></ul>
Should stem cell research continue? <ul><li>Religious vs. pragmatic views </li></ul><ul><li>Funding (public vs. private) </li></ul><ul><li>Should health insurance companies have access to genetic testing information? </li></ul>
Bibliography <ul><li>Stem Cells: A Primer . Retrieved June 12, 2002, from www.nih.gov/news/stemcell/primer.htm </li></ul><ul><li>Are Stem Cells the Answer? Retrieved June 14, 2002, from www.hhmi.org/bulletin/mar2002/stemcells/stemcells2.html . </li></ul><ul><li>Government Gives $3.5 million in Stem Cell Research Grants. Retrieved June 11, 2002, from www.amarillonet.com/stories/04902/hea_govgives.shtml . </li></ul><ul><li>Stem Cell Muscular Dystrophy Promise . Retrieved June 15, 2002, from www.news.bbc.co.uk/hi/english/health/newsid_1998000/199861 9.stm . </li></ul>