News from the 2004 Clinical Congress

NEW ORLEANS—For the first time in the clinical literature, researchers are reporting that cells derived from an unfertilized female egg can be transformed into multi-purpose stem cells. In a study presented at the 2004 annual Clinical Congress of the American College of Surgeons (ACS), researchers described the use of parthenogenesis, which is the ability to create cloned embryos from an egg alone without it first being fertilized by sperm. Authors of the study believe parthenogenesis may be an alternative source of stem cells that does not require human embryonic tissue. However, stem cells obtained by means of parthenogenesis would not necessarily be a substitute for embryonic stem cells. "One would never want to say that one cell type is going to be a replacement for another. The different cell types are different options for the future. Some cell types are going to have pluses and others are going to have minuses," according to Anthony Atala, MD, FACS, professor of surgery and director of the Wake Forest Institute for Regenerative Medicine, Wake Forest University School of Medicine, Winston Salem, NC.

One advantage afforded by stem cells obtained through parthenogenesis is that they may be used in the same patient without immunosuppression (drug therapy to foster acceptance of foreign tissue). All human embryonic stem cells would be immunologically different from the patient they are intended to treat. The cells therefore would be rejected unless the patient under-went immunosuppression. "A woman produces an egg every 28 days. Unless it is fertilized, the egg is discarded. We may be able to take that egg, grow cells needed for a particular kind of therapy, and deliver them back to the patient. These cells would be genetically matched to the patient, so they would not be rejected, and the patient would not need to be immunosuppressed," Dr. Atala explained. Stem cells derived through parthenogenesis also could be used in other patients, in the same way as human embryonic stem cells, with immunosuppression, he added.

It is not clear how parthenogenesis-derived stem cells may be applied clinically. But these cells offer the same kind of treatment potential as human embryonic stem cells. Dr. Atala and his associates currently are exploring a number of avenues. "We're looking at conditions that need cells for therapy. The hope is that for any condition that requires cell or tissue therapy, this technology would have potential implications," he said.

In the study presented at the 2004 annual ACS Clinical Congress, the investigators took eggs from rabbits and activated them with electrical energy to induce cell division. Once a mass of cells was generated within the egg, the researchers removed them and grew them in culture. Cells that had specific markers consistent with the ability to transform into different cell lines were selected. These cells then were treated with growth factors to differentiate them into muscle, blood vessels, bone, and fat. Results from the study showed that sufficient numbers of cells could be produced for cell or tissue engineering purposes. "Researchers cannot use human embryonic stem cells because of the ethical debate. So we are looking at alternative sources of stem cells. Cell therapy consequently is a hot area, but parthenogenesis as a source of stem cells is largely unexplored," Dr. Atala concluded.

Also participating in the study were Chester Koh, MD; Robert Lanza, MD, PhD; Shay Soker, PhD; and James Yoo, MD, PhD.