LOS ANGELES, Aug. 5 (Xinhuanet) -- A team of scientists at the University of Pittsburgh reported on Friday their newly discovered cells in placental tissue can develop into any type of cell.

    In a paper published in the online journal Stem Cells Express, scientists said these cells have the same potential to treat diseases and regenerate tissues as embryonic stem cells, and will not arouse so many ethic debates.

An ampoule containing a medium for stem cell storage is displayed at the UK Stem Cell Bank in north London, May 19, 2004. (Reuters/file)

    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 reported.

    These so-called amniotic epithelial cells could in fact be directed to form liver, pancreas, heart and nerve cells under the right laboratory conditions, scientists said.

    "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 lead investigator Stephen Strom, associate professor at the University of Pittsburgh School of Medicine.

    According to US census figures, there are more than 4 million live births each year. For each discarded placenta, there are about 300 million amniotic epithelial cells that 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 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 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, 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. Enditem