retrieved via a surgical procedure that is typically performed under anesthesia, and both the surgery and the anesthesia carry their own risks. Furthermore, given the very personal nature of egg donation, the experience may carry psychological risks for some women as well.

With this in mind, in 2006 the California Institute for Regenerative Medicine contracted with the National Academies to organize a workshop that would bring together experts from various areas to speak about the potential risks of oocyte donation and to summarize what is known and what needs to be known about this topic. The Committee on Assessing the Medical Risks of Human Oocyte Donation for Stem Cell Research was formed to plan the workshop, which was held in San Francisco on September 28, 2006. This report is a summary and synthesis of that workshop.

SOURCES OF STEM CELLS

Stem cells are the body’s resource for all other types of cells. That is, stem cells are unspecialized cells that can self-replicate and give rise to specialized types of cells, from neurons to white blood cells. Stem cells come in several varieties, including embryonic, fetal, and adult stem cells, but most of the interest in possible medical applications has focused on: embryonic stem cells and adult stem cells. Embryonic stem cells can give rise to any type of cell in the body, whereas adult stem cells are generally more limited, giving rise to only certain types of cells, depending on where in the body they are located. Although adult stem cells may have many important therapeutic uses, embryonic stem cells are generally considered to have more potential at this time, in large part because it is relatively easier to grow large numbers of embryonic stem cells in a cell culture. And, in particular, Proposition 71 gives priority to human embryonic stem cell research.

As Linda Giudice, the committee chair, explained in her introductory remarks at the workshop, human embryonic stem cells are generally collected from the inner cell mass of the blastocyst. A blastocyst is a spherical preimplantation embryo containing 200 to 250 cells. It consists of an outer layer of cells, the trophectoderm, and an inner fluid-filled cavity (blastocoel) containing an interior cluster of cells called the inner cell mass. It is the inner cell mass from which embryonic stem cells are derived.



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