Stem Cells :: Discarded placentas deliver researchers promising cells

Routinely discarded as medical waste, placental tissue could feasibly provide an abundant source of cells that may have the potential to treat diseases and regenerate tissues as their more controversial counterparts, embryonic stem cells, suggests a University of Pittsburgh study to be published in the journal Stem Cells and available now as an early online publication in Stem Cells Express.

A part of the placenta called the amnion, or the outer membrane of the amniotic sac, is comprised of cells that have strikingly similar characteristics to embryonic stem cells, including the ability to express two key genes that give embryonic stem cells their unique capability for developing into any kind of specialized cell, the researchers report. And according to the results of their studies, these so-called amniotic epithelial cells could in fact be directed to form liver, pancreas, heart and nerve cells under the right laboratory conditions.

If we could develop efficient methods that would allow amnion-derived cells to differentiate into specific cell types, then placentas would no longer be relegated to the trashcan. Instead, we?d have a useful source of cells for transplantation and regenerative medicine, said senior author Stephen C. Strom, Ph.D., associate professor of pathology at the University of Pittsburgh School of Medicine and a researcher at the university?s McGowan Institute for Regenerative Medicine.

According to U.S. census figures, there are more than 4 million live births each year. For each discarded placenta, the researchers calculate there are about 300 million amniotic epithelial cells that potentially could be expanded to between 10 and 60 billion cells relatively easily.

Provided that research advances to the point that we can demonstrate these cells? true therapeutic benefit, parents could conceivably choose to bank their child?s amniotic epithelial cells in the event they may someday be needed, as is sometimes done now with umbilical cord blood, commented Dr. Strom.

The amnion is derived from the embryo and forms as early as eight days after fertilization, when the fate of cells has yet to be determined, and serves to protect the developing fetus. According to the researchers? studies using placentas from full-term pregnancies, amniotic epithelial cells have many of the telltale surface markers that define embryonic stem cells, and also express the Oct-4 and nanog genes that are known to be required for self-renewal and pluripotency the ability to develop into any type of cell.

Yet the authors are careful to point out that despite their remarkable similarities to embryonic stem cells, amniotic epithelial cells are not stem cells per se, because they can?t grow indefinitely. This may be due to the fact that these amnion-derived cells do not express a certain enzyme, called telomerase, that is important for normal DNA and chromosome replication, and by extension, ultimately, cell division.

With the addition of various growth factors, the authors report the amnion-derived cells could differentiate to become liver cells, heart cells, the glial and neuronal cells that make up the nervous system, and pancreatic cells with genetic markers for insulin and glycogen production.

Further research will help to determine the efficacy of using cells from placenta tissue to treat diseases and regenerate tissue.


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