Where Do Stem Cells Come From?

Embryonic stem cells are derived from several sources. Most are derived from embryos that are no longer needed that are stored in fertility clinics. There are currently more than 400,000 embryos stored in freezers that are in excess of clinical need.

Parents of IVF embryos may be given a choice of what to do with their pre-implanted embryos in excess of clinical need. If the embryos have been kept in the freezer for one year or longer, parents may choose to:
  • Continue to store the embryos in the freezer which may cost about $1,200/year.
  • Give the embryos up for adoption (not many embryos are given up for adoption).
  • Dispose of the embryos in a dignified manner.
  • Donate the embryos for research purposes.

Thought Question

Should parents of donated embryos be compensated for the donation and for any subsequent patenting of technology derived from their donated embryos?

A second source of stem cells can be obtained from aborted fetuses, where the germ cells (ovaries and testes) are of particular interest.

A third source of stem cells, known as multipotent stem cells, can be found in many types of adult tissue such as bone marrow, adipose tissue (fat), and umbilical cord blood. Adult stem cells are needed every day to replenish a variety of cell types in our body that normally wear out and die in large numbers. Examples of cells that need to be constantly replaced are blood, skin cells, and the lining of our intestinal tract. Areas of the body not previously thought to contain stem cells, such as the brain, have in recent years been discovered to contain these self-renewing cells.

Given advancing research,including induced pluripotent stem, where somatic (skin) cells are programmed to revert back to stem cells, the need to destroy human embryos to harvest (derive) pluripotent stem cells is removed.

Given advancing research, including creation of induced pluripotent stem (iPS) cells, many ask -- Why not just pursue research with adult stem cells to eliminate any ethical concerns?
Several reasons are given why adult stem cells are difficult to use.
  • They are not found in great numbers.
  • They are difficult to isolate and maintain in culture.
  • They proliferate at a slower rate.
  • They are less diverse and less likely to change into another type of cell.
  • Also worrisome is that adult stem cells may contain more DNA abnormalities that are caused by exposure to environmental contaminants.

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