Saving Superman:
A Look into Stem Cell Research

There are three ways thus far in which scientists can isolate human pluripotent cell lines.  Other methods currently under research, including parthogenesis, have not been successful with human cells.

Inner Cell Mass Isolation from Embryonic Tissue:  The inner cell mass of the blastocyst of an embryo constitutes pluripotent cells.  With permission from patients, researchers obtain excess embryos from in-vitro fertility clinics to isolate these cells, which are called embryonic stem cells (ES).

Primordial Germ Line Isolation from Fetal Tissue:  Pluripotent stem cells can be derived from the primitive germ line stem cells that exist from the blastocyst stage until their migration to and conversion within the developing gonads into either sperm or egg stem cells.  Researchers obtain these stem cells from terminated pregnancies, where parents independently decide to end the pregnancy and give consent.  These cells are called embryonic germ line stem cells (EG) and have very similar properties to ES.

Source:  National Institutes of Health, http://www4.od.nih.gov/stemcell/fig3b.gif

Somatic Cell Nuclear Transfer (aka "Therapeutic Cloning"):  This process involves the use of an unfertilized egg cell.  First, the nucleus of the egg is removed.  Then, the nucleus of a somatic cell (body cell) is transplanted into the enucleated egg.  The egg contains special factors to "reprogram" the genes of the body cell nucleus so that the result is a totipotent cell.  The cell is kept in culture in a nutrient bath for a few days until cellular division creates a cluster of 120 pluripotent cells, which researchers then isolate.  There are a few critical points to keep in mind.  Unlike the traditional method where a sperm and egg unite to form a totipotent zygote, nuclear transplantation involves the use of an unfertilized egg to form a totipotent cell.  Also, this cell is not implanted into a uterus and thus cannot develop into a human being on its own, a point that Reeve stresses in his advocacy for nuclear transplantation.  This is not reproductive cloning, but a way to produce stem cells that are compatible with a person's own body.

Concept Check:

1. What is one issue you think has arisen concerning the process of primordial germ line isolation?  How do you feel about it?
2. What are some possible ways in which the processes outlined above could be abused?
3. Using the diagram above, show how nuclear transplantation fits into the picture.
4. In what ways is nuclear transplantation so advantageous?
5. One important issue with stem cell research concerns the public vs. private sectors.  President Bush has agreed to federal funding only for the approximate 60 stem cell lines that have already been isolated.  He does not support further study of embryos.  With what you know so far, do you agree or disagree with this?  Why?
6. What consequences could arise by leaving future research unregulated in the private sector or by completely banning it?  What do you think are some advantages or disadvantages to having federally regulated research?

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