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.)
Undifferentiated cells that have the ability to form any adult cell. I.e. Heart cells, liver cells, pancreatic cells, skin cells, nerve cells etc.
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 )
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.
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)