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.
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.
|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)|
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 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
"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
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