Placental stem cells with key therapeutic properties can be harvested from chorion

Scientists at Children's Hospital Oakland Research Institute (CHORI) led by Vladimir Serikov, MD, PhD, and Frans Kuypers, PhD, report in the current Epub issue of Stem Cells Translational Medicine that placental stem cells with important therapeutic properties can be harvested in large quantities from the fetal side of human term placentas (called the chorion). The chorion is a part of the afterbirth and is normally discarded after delivery, but it contains stem cells of fetal origin that appear to be pluripotent -- i.e., they can differentiate into different types of human cells, such as lung, liver, or brain cells. Since these functional placental stem cells can be isolated from either fresh or frozen term human placentas, this implies that if each individual's placenta is stored at birth instead of thrown away, these cells can be harvested in the future if therapeutic need arises. This potential represents a major breakthrough in the stem cell field.

In previous work, Drs. Serikov and Kuypers reported a novel technology to harvest blood-forming stem cells from the placenta to augment cord blood cells. These cells are "siblings" of the cord blood derived stem cells. Cord blood stem cells, unlike embryonic stem cells, have been used for many hundreds of successful bone marrow transplants. These transplants are mainly performed in children, as the amount of cells that can be harvested from cord blood is usually not sufficient for a successful transplant in adults. Adding placental-derived stem cells to the cord blood stem cells could make successful adult bone marrow transplants routinely possible.

The current report demonstrates that placental stem cells have much broader therapeutic potential than bone-marrow transplants, because they are pluripotent - i.e. able to differentiate into many different cell types -- and they also generate growth factors that help in tissue repair. These cells are shown to integrate into different tissues when transplanted into mice, but like cord blood stem cells, and in contrast to embryonic pluripotent stem cells, they do not form tumor-like structures in mice.

Placental-derived stem cells are often viewed as "adult" stem cells in contrast to "embryonic" stem cells, which are the dominant focus in the stem cell research field. However, this report shows that these fetal stem cells can be harvested in large numbers, and without the ethical concerns attached to the use of embryonic stem cells. These stem cells may thus be a more practical source for regenerative medicine, particularly since, if placentas are routinely saved instead of thrown away, each individual will be able to draw on their own fetal stem cells if future therapeutic needs arise.

Placental stem cells are only 9 months old, and in contrast to adult stem cells, do not need to be reprogrammed to become pluripotent. Placental-derived stem cells have characteristics of young and vigorous cells, including young mitochondria. Future research will be aimed to bring this to the clinic and to test their efficacy in translational therapeutic applications.